U.S. patent application number 14/417870 was filed with the patent office on 2015-09-10 for air-conditioning apparatus.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Takayoshi Honda, Osamu Morimoto, Daisuke Shimamoto.
Application Number | 20150253020 14/417870 |
Document ID | / |
Family ID | 50477039 |
Filed Date | 2015-09-10 |
United States Patent
Application |
20150253020 |
Kind Code |
A1 |
Honda; Takayoshi ; et
al. |
September 10, 2015 |
AIR-CONDITIONING APPARATUS
Abstract
An air-conditioning apparatus includes a heat medium temperature
adjustment operation mode in which when the temperature of a heat
medium falls outside a predetermined temperature range while a
compressor and a pump are kept stopped, the compressor and the pump
are driven to cause an intermediate heat exchanger to exchange heat
between a refrigerant and the heat medium so that the heat medium
is heated or cooled to have a temperature that falls within the
temperature range.
Inventors: |
Honda; Takayoshi; (Tokyo,
JP) ; Shimamoto; Daisuke; (Tokyo, JP) ;
Morimoto; Osamu; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
50477039 |
Appl. No.: |
14/417870 |
Filed: |
October 10, 2012 |
PCT Filed: |
October 10, 2012 |
PCT NO: |
PCT/JP2012/076248 |
371 Date: |
January 28, 2015 |
Current U.S.
Class: |
62/190 |
Current CPC
Class: |
F25B 25/005 20130101;
F25B 13/00 20130101; F25B 2313/0314 20130101; F24D 3/18 20130101;
Y02B 30/70 20130101; Y02B 30/12 20130101; F25B 2600/13 20130101;
F25B 2313/0231 20130101; F24F 3/065 20130101; F25B 2313/003
20130101; Y02B 30/745 20130101; F24D 19/1009 20130101; F24F 5/001
20130101 |
International
Class: |
F24F 5/00 20060101
F24F005/00; F24F 11/00 20060101 F24F011/00 |
Claims
1. An air-conditioning apparatus including a refrigeration cycle
circuit including a compressor, a heat source side heat exchanger,
at least one expansion valve, and a plurality of intermediate heat
exchangers connected to one another via refrigerant pipes, the
intermediate heat exchangers being configured to exchange heat
between a refrigerant and a heat medium, and a heat medium
circulation circuit including the intermediate heat exchangers, a
pump configured to convey the heat medium, and a plurality of use
side heat exchangers, each use side heat exchanger being connected
to the intermediate heat exchangers and the pump via heat medium
pipes to form the heat medium circulation circuit in which the
plurality of use side heat exchangers are parallel to each other,
wherein the apparatus is provided with a heat medium temperature
adjustment operation mode in which when a temperature of the heat
medium falls outside a predetermined temperature range while the
compressor and the pump are kept stopped, the compressor and the
pump are driven to cause the intermediate heat exchangers to
exchange heat between the refrigerant and the heat medium so that
the heat medium is heated or cooled to have a temperature that
falls within the predetermined temperature range; the apparatus
comprising: a temperature sensor configured to detect the
temperature of the heat medium; a control device configured to
control the compressor and the pump based on at least a detection
result obtained by the temperature sensor to perform the heat
medium temperature adjustment operation mode; and a plurality of
channel switching valves located in portions of the heat medium
circulation circuit corresponding to an inlet and an outlet of the
heat medium in each of the plurality of the use side heat
exchangers, and configured to switch a passage of the heat medium
having passed through the plurality of intermediate heat exchangers
to one of the plurality of use side heat exchangers, wherein the
control device controls the channel switching valve such that the
heat medium is supplied from at least two of the plurality of
intermediate heat exchangers to the corresponding ones of the
plurality of use side heat exchangers, and mixes, through the
channel switching valve, a stream of the heat medium supplied from
one of the plurality of intermediate heat exchangers to the
corresponding one of the plurality of use side heat exchangers with
a stream of the heat medium supplied from another one of the
plurality of intermediate heat exchangers to the corresponding one
of the plurality of use side heat exchangers, and the control
device performs at least one of a control operation in which when
the detection result obtained by the temperature sensor is higher
than the temperature range, the control device causes a
corresponding one of the plurality of intermediate heat exchangers
to function as an evaporator and cools the heat medium passing
through a corresponding one of the plurality of intermediate heat
exchangers, and a control operation in which when the detection
result obtained by the temperature sensor is lower than the
temperature range, the control device causes a corresponding one of
the plurality of intermediate heat exchangers to function as a
radiator and heats the heat medium passing through a corresponding
one of the plurality of intermediate heat exchangers.
2-3. (canceled)
4. The air-conditioning apparatus of claim 1, wherein when the
detection result obtained by the temperature sensor a predetermined
time after driving of the compressor and the pump is higher than a
temperature obtained by adding an antihunting constant to a lower
limit of the temperature range and is not higher than an upper
limit of the temperature range, the control device stops the
compressor and the pump.
5. (canceled)
6. The air-conditioning apparatus of claim 1, wherein when the
detection result obtained by the temperature sensor a predetermined
time after driving of the compressor and the pump is lower than a
temperature obtained by subtracting an antihunting constant from an
upper limit of the temperature range and is not lower than a lower
limit of the temperature range, the control device stops the
compressor and the pump.
7. The air-conditioning apparatus of claim 1, wherein the control
device opens the channel switching valve to ensure a circulation
channel of the heat medium before or concurrently with driving of
the pump, and causes the heat medium to circulate between at least
one of the plurality of intermediate heat exchangers and a
corresponding one of the plurality of use side heat exchangers.
8. The air-conditioning apparatus of claim 1, further comprising:
an outdoor-air temperature sensor configured to detect an
outdoor-air temperature, wherein the control device calculates an
average temperature of outdoor air in a predetermined period of
time based on a detection result obtained by the outdoor-air
temperature sensor, and determines an upper limit and a lower limit
of the temperature range based on the calculated average
temperature.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a U.S. national stage application of
PCT/JP2012/076248 filed on Oct. 10, 2012, the contents of which are
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present invention relates to an air-conditioning
apparatus such as a multi-air-conditioning apparatus for
buildings.
BACKGROUND
[0003] In a multi-air-conditioning apparatus for buildings, which
is a typical air-conditioning apparatus, a refrigerant circulates
between an outdoor unit serving as a heat source device disposed
outdoors and an indoor unit disposed indoors so that cooling energy
or heating energy is conveyed into a room. Hydrofluorocarbon (HFC)
refrigerant is often used as a refrigerant, and the use of a
natural refrigerant such as CO.sub.2 has also been proposed.
[0004] In a chiller which typifies the conventional
air-conditioning apparatus as well, a heat source device located
outdoors generates cooling energy or heating energy, and a heat
exchanger disposed in an outdoor unit transmits the cooling energy
or heating energy to a heat medium such as water or antifreeze
(see, for example, Patent Literature 1). In such a chiller, cooling
energy or heating energy transmitted to the heat medium is conveyed
to, for example, a fan coil unit or a panel heater serving as an
indoor unit to enable cooling or heating.
[0005] In the chiller, heat is exchanged between a refrigerant and
water on the outside, and the water having undergone heat exchange
is conveyed to the indoor unit. Thus, considerable power is
necessary for conveying water, resulting in deterioration of energy
saving performance.
[0006] In addition, in the chiller, when a pump in a water circuit
is kept stopped for a long period of time, cooling energy of the
refrigerant in the refrigerant circuit is continuously transmitted
to the water near the heat exchanger, so the water is likely to
freeze in the pipe.
[0007] In another proposed air-conditioning apparatus, a
refrigerant circulation circuit is extended to a portion near the
inside of the room. If such an air-conditioning apparatus employs
HCF refrigerant, a refrigerant such as HFC is conveyed to the
indoor unit. Thus, damage to a pipe in the indoor unit, for
example, causes leakage of a refrigerant into the room, resulting
in deterioration of the indoor environments.
[0008] In view of this, a proposed air-conditioning apparatus
includes pipes configured to prevent a refrigerant such as HFC from
circulating near an indoor unit in order to attain excellent energy
saving performance, and prevent freezing of a heat medium (see, for
example, Patent Literature 2).
[0009] The technique of Patent Literature 2 includes an
anti-freezing operation mode for preventing freezing of water in a
heat medium pipe. In the anti-freezing operation mode, when the
temperature detected by a temperature sensor decreases to a set
temperature or lower while a compressor or a pump is kept stopped,
an outdoor unit starts in a heating mode. Then, in this operation
mode, heat is exchanged between a high-temperature high-pressure
refrigerant and the heat medium so as to prevent freezing of the
heat medium in the heat medium pipe.
PATENT LITERATURE
[0010] Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 2003-343936 (see, for example, FIG. 1)
[0011] Patent Literature 2: WO2010/050003A1 (see, for example,
claim 1 and FIG. 1)
[0012] In the technique of Patent Literature 2, suppose, for
example, the temperature detected by the temperature sensor
decreases to the set temperature or lower and the apparatus shifts
to an anti-freezing operation mode while the compressor is kept
stopped in a cooling mode. In this case, a heating mode is
performed to heat the heat medium, thereby suppressing freezing of
the heat medium.
[0013] In transition from the anti-freezing operation mode to the
cooling mode again, if a heat medium temperature necessary for
achieving a target indoor temperature is greatly different from a
heat medium temperature at the start of the compressor in the
cooling mode, air providing a feeling of draft (a feeling of
excessive cold or heat) is disadvantageously supplied into the
room, resulting in the possibility of impaired comfort of the
user.
[0014] Since wind providing a feeling of draft is not supplied into
the room, if an operation of reducing the amount of air blowing
from an indoor unit is performed for a long period of time, the
time taken for the room to reach a target temperature may
increase.
SUMMARY
[0015] The present invention has been made in order to solve the
above-mentioned problems, and has as its object to provide an
air-conditioning apparatus that can supply air providing little
feeling of draft (a feeling of cold or heat) to the room
immediately after the start of operation and reduce an increase in
time taken for the room to reach a target indoor temperature.
[0016] An air-conditioning apparatus according to the present
invention includes a refrigeration cycle circuit including a
compressor, a heat source side heat exchanger, at least one
expansion valve, and an intermediate heat exchanger connected to
one another via refrigerant pipes, the intermediate heat exchanger
being configured to exchange heat between a refrigerant and a heat
medium, and a heat medium circulation circuit including the
intermediate heat exchanger, a pump configured to convey the heat
medium, and a use side heat exchanger connected to one another via
heat medium pipes. The apparatus includes a heat medium temperature
adjustment operation mode in which when a temperature of the heat
medium falls outside a predetermined temperature range while the
compressor and the pump are kept stopped, the compressor and the
pump are driven to cause the intermediate heat exchanger to
exchange heat between the refrigerant and the heat medium so that
the heat medium is heated or cooled to have a temperature that
falls within the predetermined temperature range.
[0017] In the air-conditioning apparatus of the present invention,
even when the operations of the compressor and the pump are
temporarily stopped so that the temperature of the heat medium
varies and falls outside the predetermined temperature range
because of factors associated with, for example, outdoor air, the
compressor and the pump are driven to allow the intermediate heat
exchanger to exchange heat between the refrigerant and the heat
medium so that the temperature of the heat medium falls within the
predetermined temperature range.
[0018] With this arrangement, the air-conditioning apparatus of the
present invention can supply wind with little feeling of draft
immediately after the start of operation and reduce an increase in
time taken for the room to reach a target indoor temperature.
BRIEF DESCRIPTION OF DRAWINGS
[0019] FIG. 1 illustrates an example of the overall structure of an
air-conditioning apparatus according to an embodiment of the
present invention.
[0020] FIG. 2 illustrates another example of the overall structure
of the air-conditioning apparatus different from the example of
FIG. 1.
[0021] FIG. 3 illustrates an example of a circuit diagram for a
refrigerant and a heat medium in the air-conditioning apparatus of
the embodiment.
[0022] FIG. 4 is a circuit diagram illustrating flow of a
refrigerant and a heat medium in a cooling only operation.
[0023] FIG. 5 is a circuit diagram illustrating flow of a
refrigerant and a heat medium in a heating only operation.
[0024] FIG. 6 is a circuit diagram illustrating flow of a
refrigerant and a heat medium in a cooling main operation.
[0025] FIG. 7 is a circuit diagram illustrating flow of a
refrigerant and a heat medium in a heating main operation.
[0026] FIG. 8 is a flowchart showing operation in a heat medium
temperature adjustment operation mode.
[0027] FIG. 9 is a flowchart showing operation in a heat medium
temperature adjustment operation mode different from that shown in
FIG. 8.
DETAILED DESCRIPTION
[0028] An embodiment of an air-conditioning apparatus according to
the present invention will be described with reference to the
accompanying drawings. The following embodiment does not limit the
present invention. In the attached drawings including FIG. 1, the
size relationship among components may be different from those in
an actual relationship.
[0029] The air-conditioning apparatus of this embodiment can supply
air providing little feeling of draft to an air-conditioned space
(e.g., a room, a room of a building, or a warehouse) immediately
after the start of operation, and has an operation mode (a heat
medium temperature adjustment operation mode) for reducing an
increase in time taken for the air-conditioned space to reach a
target indoor temperature.
Configuration
[0030] FIG. 1 illustrates an example of the overall structure of an
air-conditioning apparatus according to an embodiment.
[0031] The air-conditioning apparatus of this embodiment includes a
heat source device (an outdoor unit) 1, an indoor unit 2 provided
in, for example, an indoor air conditioner, and a relay unit 3
separated from the outdoor unit 1 and located in, for example, a
non-air-conditioned space 8.
[0032] The heat source device 1 is connected to the relay unit 3 by
refrigerant pipes 4, and a refrigerant exhibiting a two-phase
change or a refrigerant (a primary medium) in supercritical state
circulates through them. The relay unit 3 is connected to the
indoor unit 2 by heat medium pipes 5, and a heat medium (a
secondary medium) such as water, brine, or antifreeze circulates
through them. The relay unit 3 includes, for example, intermediate
heat exchangers 15a and 15b to, for example, exchange heat between
the refrigerant supplied from the heat source device 1 and the heat
medium supplied from the indoor unit 2.
[0033] The heat source device 1 is generally disposed in an outdoor
space 6 that is outside a construction 9 such as a building. The
indoor unit 2 is disposed in an indoor space 7 such as a room
inside the building construction 9 at a position at which the
indoor unit 2 can convey heated or cooled air.
[0034] The relay unit 3 is encased in a housing different from
housings accommodating the heat source device 1 and the indoor unit
2, and is connected to the heat source device 1 and the indoor unit
2 by the refrigerant pipes 4 and the heat medium pipes 5 so that
the relay unit 3 can be located at a position different from the
outdoor space 6 and the indoor space 7. Referring to FIG. 1, the
relay unit 3 is disposed in the non-air-conditioned space 8, such
as a space above a ceiling, which is a space located inside the
construction 9 but different from the indoor space 7. The relay
unit 3 can be disposed in, for example, a common area including,
for example, an elevator.
[0035] The heat source device 1 and the relay unit 3 are connected
to each other by two refrigerant pipes 4. The relay unit 3 and each
indoor unit 2 are connected to each other by two heat medium pipes
5. Such connection using two pipes facilitates construction of the
air-conditioning apparatus.
[0036] FIG. 2 illustrates another example of the overall structure
of the air-conditioning apparatus different from the example of
FIG. 1. As illustrated in FIG. 2, the air-conditioning apparatus of
this embodiment may include a plurality of relay units 3. More
specifically, the relay units 3 include a main-relay unit 3a and
two sub-relay units 3b(1) and 3b(2) branching from the main-relay
unit 3a. In this manner, the plurality of sub-relay units 3b can be
connected to the single main-relay unit 3a. In this structure,
three pipes are used to connect the main-relay unit 3a and the
sub-relay units 3b.
[0037] Referring to FIGS. 1 and 2, the indoor unit 2 is of the
ceiling cassette type as an example, but the present invention is
not limited to this type. More specifically, the indoor unit 2 is
not limited to the ceiling cassette type, and may adopt the ceiling
concealed type or the ceiling suspension type as long as heated or
cooled air can be blown to the indoor space 7 directly or via, for
example, a duct.
[0038] In the above-described example, although the heat source
device 1 is placed in the outdoor space 6 outside the construction
9, the present invention is not limited to this example. The heat
source device 1 may be placed in an enclosed space such as a
machinery room having, for example, a ventilation opening. The heat
source device 1 may also be placed inside the construction 9 to
release waste heat to the outside of the construction 9 through an
exhaust duct, or may use a water-cooled heat source device as
located in the construction 9.
[0039] The relay unit 3 can also be placed near the heat source
device 1. In this case, however, if the distance from the relay
unit 3 to the indoor unit 2 is too long, a large amount of power is
needed to convey the heat medium, and thus the energy saving
performance deteriorates. For this reason, when the relay unit 3 is
located near the heat source device 1, the position of the heat
source device 1 is preferably determined such that the distance
from the relay unit 3 to the indoor unit 2 is not too long.
[0040] The structure of the air-conditioning apparatus illustrated
in FIGS. 1 and 2 will be specifically described. FIG. 3 illustrates
an example of a circuit diagram for a refrigerant and a heat medium
in the air-conditioning apparatus of the embodiment. As illustrated
in FIG. 3, the air-conditioning apparatus includes the heat source
device 1, the indoor unit 2, and the relay unit 3 described with
reference to FIGS. 1 and 2. In the following description, the relay
unit 3 of the air-conditioning apparatus of this embodiment
includes one main-relay unit 3a and one sub-relay unit 3b
illustrated in FIG. 2.
[0041] The heat source device 1 includes a compressor 10 that
compresses and discharges a refrigerant; a four-way valve 11 that
switches the flow of the refrigerant; a heat source side heat
exchanger 12 that serves as a condenser (a radiator) or an
evaporator; check valves 13a, 13b, 13c, and 13d that can uniform
the direction in which the refrigerant flows, irrespective of
whether the operation mode is a cooling operation or a heating
operation; and an accumulator 17 storing an excess refrigerant.
[0042] The indoor unit 2 includes use side heat exchangers 26a to
26d serving as evaporators or condensers.
[0043] The relay unit 3 includes the main-relay unit 3a and the
sub-relay unit 3b. The main-relay unit 3a includes a gas-liquid
separator 14 that separates the refrigerant into gas and liquid
refrigerants, and an expansion valve (e.g., an electronic expansion
valve) 16e.
[0044] The sub-relay unit 3b includes the intermediate heat
exchangers 15a and 15b for exchanging heat between the refrigerant
and a heat medium; expansion valves (e.g., electronic expansion
valves) 16a to 16d for reducing the pressure of the refrigerant;
pumps 21a and 21b for conveying the heat medium; and channel
switching valves 22a to 22d and channel switching valves 23a to 23d
such as three-way valves for switching the flow of the heat
medium.
[0045] In the sub-relay unit 3b, stop valves 24a to 24d that can
open and close channels are connected to the heat medium pipes 5 on
the sides of the inlets of the use side heat exchangers 26a to 26d,
and flow control valves 25a to 25d that can adjust the flow rate of
the heat medium are connected to the heat medium pipes 5 on the
sides of the outlets of the use side heat exchangers 26a to
26d.
[0046] The sub-relay unit 3b further includes bypasses 27a to 27d
connecting the inlets and the outlets of the use side heat
exchangers 26a to 26d. The bypasses 27a to 27d connect the flow
control valves 25a to 25d to the heat medium pipes 5 provided
between the channel switching valves 23a to 23d and the use side
heat exchangers 26a to 26d.
[0047] The channel switching valves 22a to 22d and 23a to 23d are
provided for the inlet and outlet channels to the use side heat
exchangers 26a to 26d. More specifically, the channel switching
valves 22a to 22d switch the inlet channels of intermediate heat
exchangers to select either intermediate heat exchanger to be
connected, and the channel switching valves 23a to 23d switch the
outlet channels of the intermediate heat exchangers to select
either intermediate heat exchanger to be connected.
[0048] In the embodiment, the channel switching valves 22a to 22d
switch the inlet channels of the intermediate heat exchangers 15a
and 15b to select either of the intermediate heat exchangers 15a
and 15b to be connected, and the channel switching valves 23a to
23d switch the outlet channels of the intermediate heat exchangers
15a and 15b to select either of the intermediate heat exchangers
15a and 15b to be connected.
[0049] The stop valves 24a to 24d are located at the inlets of the
use side heat exchangers 26a to 26d, and the flow control valves
25a to 25d are provided at the outlets of the use side heat
exchangers 26a to 26d. The inlets and outlets of the use side heat
exchangers 26a to 26d are connected to each other by the bypasses
27a to 27d through the flow control valves 25a to 25d.
[0050] The sub-relay unit 3b includes first to seventh temperature
sensors and pressure sensors, as will be described below.
[0051] The sub-relay unit 3b includes temperature sensors (first
temperature sensors) 31a and 31b for detecting the temperatures of
the heat medium at the outlets of the intermediate heat exchangers
15a and 15b; temperature sensors (second temperature sensors) 32a
and 32b for detecting the temperatures of the heat medium at the
inlets of the intermediate heat exchangers 15a and 15b; temperature
sensors (third temperature sensors) 33a to 33d for detecting the
temperatures of the heat medium at the inlets of the use side heat
exchangers 26a to 26d; and temperature sensors (fourth temperature
sensors) 34a to 34d for detecting the temperatures of the heat
medium at the outlets of the use side heat exchangers 26a to
26d.
[0052] The sub-relay unit 3b includes a temperature sensor (a fifth
temperature sensor) 35 for detecting the temperature of the
refrigerant at the outlet of the intermediate heat exchanger 15a; a
temperature sensor (a sixth temperature sensor) 37 for detecting
the temperature of the refrigerant at the inlet of the intermediate
heat exchanger 15b; and a temperature sensor (a seventh temperature
sensor) 38 for detecting the temperature of the refrigerant at the
outlet of the intermediate heat exchanger 15b.
[0053] The sub-relay unit 3b further includes a pressure sensor 36
for detecting the pressure of the refrigerant at the outlet of the
intermediate heat exchanger 15a; and an outdoor-air temperature
sensor 39, located in the outdoor unit 1, for detecting an
outdoor-air temperature.
[0054] These temperature sensors and pressure sensors are not
specifically limited, and can be various types of thermometers,
temperature sensors, pressure gauges, and pressure sensors.
[0055] The air-conditioning apparatus of this embodiment includes a
refrigeration cycle circuit including the compressor 10, the
four-way valve 11, the heat source side heat exchanger 12, the
check valves 13a to 13d, the gas-liquid separator 14, the expansion
valves 16a to 16e, the intermediate heat exchangers 15a and 15b,
and the accumulator 17 connected to each other via the refrigerant
pipes.
[0056] The air-conditioning apparatus of this embodiment also
includes a heat medium circulation circuit (to be also referred to
as a first heat medium circulation circuit hereinafter) including
the intermediate heat exchanger 15a, the pump 21a, the channel
switching valves 22a to 22d, the stop valves 24a to 24d, the use
side heat exchangers 26a to 26d, the flow control valves 25a to
25d, and the channel switching valves 23a to 23d connected to each
other via the heat medium pipes. The air-conditioning apparatus of
this embodiment also includes a heat medium circulation circuit (to
be also referred to as a second heat medium circulation circuit
hereinafter) including the intermediate heat exchanger 15b, the
pump 21b, the channel switching valves 22a to 22d, the stop valves
24a to 24d, the use side heat exchangers 26a to 26d, the flow
control valves 25a to 25d, and the channel switching valves 23a to
23d connected to each other via the heat medium pipes.
[0057] As illustrated in FIG. 3, in the first heat medium
circulation circuit, the use side heat exchangers 26a to 26d are
connected in parallel to the intermediate heat exchanger 15a. In
the second heat medium circulation circuit as well, the use side
heat exchangers 26a to 26d are also connected in parallel to the
intermediate heat exchanger 15b.
[0058] The heat source device 1 includes a control device 100 that
controls components constituting the heat source device 1 to cause
the heat source device 1 to operate as a so-called outdoor unit.
The relay unit 3 includes a control device 300 that controls
components constituting the relay unit 3 to cause the relay unit 3
to perform the following operations. The control devices 100 and
300 are implemented using, for example, microcomputers, and are
connected to each other to be capable of communication with each
other. The operation of the air-conditioning apparatus in each
operation mode will now be described.
Cooling Only Operation
[0059] FIG. 4 is a circuit diagram illustrating flow of the
refrigerant and the heat medium in a cooling only operation. In the
cooling only operation, the refrigerant is compressed by the
compressor 10, turns into a high-temperature high-pressure gas
refrigerant, and enters the heat source side heat exchanger 12
through the four-way valve 11. The refrigerant is condensed and
liquefied in the heat source side heat exchanger 12, flows out of
the heat source device 1 through the check valve 13a, and then
flows into the relay unit 3 through the refrigerant pipes 4. In the
relay unit 3, the refrigerant enters the gas-liquid separator 14
and is introduced into the intermediate heat exchanger 15b through
the expansion valves 16e and 16a. In this process, the refrigerant
is expanded by the expansion valve 16a and turns into a
low-temperature low-pressure two-phase refrigerant, and the
intermediate heat exchanger 15b serves as an evaporator. In the
intermediate heat exchanger 15b, the refrigerant turns into a
low-temperature low-pressure gas refrigerant, flows out of the
relay unit 3 through the expansion valve 16c, and flows into the
heat source device 1 again through the refrigerant pipes 4. In the
heat source device 1, the refrigerant passes through the check
valve 13d and is drawn by suction into the compressor 10 through
the four-way valve 11 and the accumulator 17. At this time, the
expansion valves 16b and 16d have opening degrees small enough to
prevent flow of the refrigerant, and the expansion valve 16c is
fully opened so that no pressure loss occurs.
[0060] A motion of a secondary heat medium (e.g., water or
antifreeze) will now be described. In the intermediate heat
exchanger 15b, cooling energy of a primary refrigerant is
transmitted to a secondary heat medium, and the cooled heat medium
is caused to flow through pipes on the secondary side by the pump
21b. The heat medium having flowed out of the pump 21b passes
sequentially through the channel switching valves 22a to 22d and
the stop valves 24a to 24d, and flows into the use side heat
exchangers 26a to 26d and the flow control valves 25a to 25d. At
this time, the flow control valves 25a to 25d operate such that
only a part of the heat medium in an amount necessary for providing
an air-conditioning load required in a room flows in the use side
heat exchangers 26a to 26d, and the remaining part of the heat
medium passes through the bypasses 27a to 27d and does not
contribute to heat exchange. A heat medium stream having passed
through the bypasses 27a to 27d merges with a heat medium stream
having passed through the use side heat exchangers 26a to 26d,
flows into the intermediate heat exchanger 15b through the channel
switching valves 23a to 23d, and is drawn by suction into the pump
21b again.
[0061] The air-conditioning load required in the room can be
provided by controlling the flow rate of the heat medium passing
through the use side heat exchangers 26a to 26d by the control
device 300 so that the differences between the temperatures
detected by the third temperature sensors 33a to 33d and those
detected by the fourth temperature sensors 34a to 34d are kept at a
predetermined target value. The same applies to a heating only
operation, a cooling main operation, and a heating main
operation.
[0062] Since no heat medium needs to be supplied to the use side
heat exchangers (including thermo-off) having no thermal loads, the
channels are closed by the stop valves 24a to 24d so that no heat
medium flows into these use side heat exchangers. Referring to FIG.
4, since the use side heat exchangers 26a and 26b have thermal
loads, the heat medium is supplied into them. On the other hand,
the use side heat exchangers 26c and 26d have no thermal loads, and
thus the corresponding stop valves 24c and 24d are closed.
Heating Only Operation
[0063] FIG. 5 is a circuit diagram illustrating flow of the
refrigerant and the heat medium in a heating only operation. In the
heating only operation, the refrigerant is compressed by the
compressor 10, turns into a high-temperature high-pressure gas
refrigerant, flows out of the heat source device 1 sequentially
through the four-way valve 11 and the check valve 13b, and then
flows into the relay unit 3 through the refrigerant pipes 4. In the
relay unit 3, the refrigerant is guided to the intermediate heat
exchanger 15a through the gas-liquid separator 14, condensed and
liquefied in the intermediate heat exchanger 15a, and flows out of
the relay unit 3 through the expansion valves 16d and 16b. In this
process, the refrigerant is expanded by the expansion valve 16b,
turns into a low-temperature low-pressure two-phase refrigerant,
and flows again into the heat source device 1 through the
refrigerant pipes 4. In the heat source device 1, the refrigerant
passes through the check valve 13c and is introduced into the heat
source side heat exchanger 12, and the heat source side heat
exchanger 12 serves as an evaporator. Then, the refrigerant turns
into a low-temperature low-pressure gas refrigerant and is drawn by
suction into the compressor 10 through the four-way valve 11 and
the accumulator 17. At this time, the expansion valve 16e and the
expansion valve 16a or 16c have opening degrees small enough to
prevent flow of the refrigerant.
[0064] A motion of a secondary heat medium (e.g., water or
antifreeze) will now be described. In the intermediate heat
exchanger 15a, heating energy of a primary refrigerant is
transmitted to a secondary heat medium, and the heated heat medium
is caused to flow through pipes on the secondary side by the pump
21a. The heat medium having flowed out of the pump 21a passes
sequentially through the channel switching valves 22a to 22d and
the stop valves 24a to 24d, and flows into the use side heat
exchangers 26a to 26d and the flow control valves 25a to 25d. At
this time, the flow control valves 25a to 25d operate such that
only a part of the heat medium in an amount necessary for providing
an air-conditioning load required in a room flows in the use side
heat exchangers 26a to 26d, and the remaining part of the heat
medium passes through the bypasses 27a to 27d and does not
contribute to heat exchange. A heat medium stream having passed
through the bypasses 27a to 27d merges with a heat medium stream
having passed through the use side heat exchangers 26a to 26d,
flows into the intermediate heat exchanger 15a through the channel
switching valves 23a to 23d, and is drawn by suction into the pump
21a again. The air-conditioning load required in the room can be
provided by a control operation in which the differences between
the temperatures detected by the third temperature sensors 33a to
33d and those detected by the fourth temperature sensors 34a to 34d
are kept at a predetermined target value.
[0065] In this process, since no heat medium needs to be supplied
to the use side heat exchangers (including thermo-off) having no
thermal loads, the channels are closed by the stop valves 24a to
24d so that no heat medium flows into these use side heat
exchangers. Referring to FIG. 5, since the use side heat exchangers
26a and 26b have thermal loads, the heat medium flows through them.
On the other hand, the use side heat exchangers 26c and 26d have no
thermal loads, and thus the corresponding stop valves 24c and 24d
are closed.
Cooling Main Operation
[0066] FIG. 6 is a circuit diagram illustrating flow of the
refrigerant and the heat medium in a cooling main operation. In the
cooling main operation, the refrigerant is compressed by the
compressor 10, turns into a high-temperature high-pressure gas
refrigerant, and is introduced into the heat source side heat
exchanger 12 through the four-way valve 11. Then, the gas
refrigerant is condensed into a two-phase refrigerant, which flows
out of the heat source side heat exchanger 12, flows out of the
heat source device 1 through the check valve 13a, and flows into
the relay unit 3 through the refrigerant pipes 4. In the relay unit
3, the refrigerant enters the gas-liquid separator 14 where the
two-phase refrigerant is separated into gas and liquid
refrigerants. The gas refrigerant is introduced into the
intermediate heat exchanger 15a, and condensed and liquefied in the
intermediate heat exchanger 15a, and passes through the expansion
valve 16d. On the other hand, the liquid refrigerant separated by
the gas-liquid separator 14 flows into the expansion valve 16e, is
condensed and liquefied in the intermediate heat exchanger 15a, and
merges with the liquid refrigerant having passed through the
expansion valve 16d. The refrigerant then passes through the
expansion valve 16a and is introduced into the intermediate heat
exchanger 15b. In this process, the refrigerant is expanded by the
expansion valve 16a and turns into a low-temperature low-pressure
two-phase refrigerant, and the intermediate heat exchanger 15b
serves as an evaporator. The refrigerant turns into a
low-temperature low-pressure gas refrigerant in the intermediate
heat exchanger 15b, flows out of the relay unit 3 through the
expansion valve 16c, and flows again into the heat source device 1
through the refrigerant pipes 4. In the heat source device 1, the
refrigerant passes through the check valve 13d and is drawn by
suction into the compressor 10 through the four-way valve 11 and
the accumulator 17. At this time, the expansion valve 16b has an
opening degree small enough to prevent flow of the refrigerant, and
the expansion valve 16c is fully opened so that no pressure loss
occurs.
[0067] A motion of a secondary heat medium (e.g., water or
antifreeze) will now be described. In the intermediate heat
exchanger 15a, heating energy of a primary refrigerant is
transmitted to the secondary heat medium, and the heated heat
medium is caused to flow through pipes on the secondary side by the
pump 21a. In the intermediate heat exchanger 15b, cooling energy of
the primary refrigerant is transmitted to the secondary heat
medium, and the cooled heat medium is caused to flow through pipes
on the secondary side by the pump 21b. The heat medium streams
having flowed out of the pumps 21a and 21b merge into one heat
medium stream, which passes sequentially through the channel
switching valves 22a to 22d and the stop valves 24a to 24d and
flows into the use side heat exchangers 26a to 26d and the flow
control valves 25a to 25d. At this time, the flow control valves
25a to 25d operate such that only a part of the heat medium in an
amount necessary for providing an air-conditioning load required in
a room flows in the use side heat exchangers 26a to 26d, and the
remaining part of the heat medium passes through the bypasses 27a
to 27d and does not contribute to heat exchange. A heat medium
stream having passed through the bypasses 27a to 27d merges with a
heat medium stream having passed through the use side heat
exchangers 26a to 26d, and the heat medium passes through the
channel switching valves 23a to 23d. Then, the hot heat medium
flows into the intermediate heat exchanger 15a and returns to the
pump 21a, while the cold heat medium flows into the intermediate
heat exchanger 15b and returns to the pump 21b. In this process,
upon the operation of the channel switching valves 22a to 22d and
23a to 23d, the hot and cold heat media are not mixed and are
individually introduced into the use side heat exchangers 26a to
26d having heating loads and cooling loads. The air-conditioning
load required in the room is provided by a control operation in
which the differences between the temperatures detected by the
third temperature sensors 33a to 33d and those detected by the
fourth temperature sensors 34a to 34d are kept at a target
value.
[0068] FIG. 6 illustrates a state in which a heating energy load is
generated in the use side heat exchanger 26a, and a cooling energy
load is generated in the use side heat exchanger 26b.
[0069] In this case, since it is unnecessary to supply a heat
medium to the use side heat exchangers (including thermo-off)
having no thermal loads, the channels are closed by the stop valves
24a to 24d so that no heat medium flows into these use side heat
exchangers. Referring to FIG. 6, since the use side heat exchangers
26a and 26b have thermal loads, the heat medium flows through them.
On the other hand, the use side heat exchangers 26c and 26d have no
thermal loads, and thus the corresponding stop valves 24c and 24d
are closed.
Heating Main Operation
[0070] FIG. 7 is a circuit diagram illustrating flow of a
refrigerant and a heat medium in a heating main operation. In the
heating main operation, the refrigerant is compressed by the
compressor 10, turns into a high-temperature high-pressure gas
refrigerant, flows out of the heat source device 1 through the
four-way valve 11 and the check valve 13b, and flows into the relay
unit 3 through the refrigerant pipes 4. In the relay unit 3, the
refrigerant is introduced into the intermediate heat exchanger 15a
through the gas-liquid separator 14, and is condensed and liquefied
in the intermediate heat exchanger 15a. Thereafter, the refrigerant
having passed through the expansion valve 16d is divided into a
channel passing through the expansion valve 16a and a channel
passing through the expansion valve 16b. The refrigerant having
passed through the expansion valve 16a is expanded by the expansion
valve 16a, turns into a low-temperature low-pressure two-phase
refrigerant, and flows into the intermediate heat exchanger 15b,
and the intermediate heat exchanger 15b serves as an evaporator.
The refrigerant having flowed out of the intermediate heat
exchanger 15b evaporates into a gas refrigerant, and passes through
the expansion valve 16c. On the other hand, the refrigerant having
passed through the expansion valve 16b is expanded by the expansion
valve 16b, turns into a low-temperature low-pressure two-phase
refrigerant, merges with the refrigerant having passed through the
intermediate heat exchanger 15b and the expansion valve 16c, and
turns into a low-temperature low-pressure refrigerant with a higher
quality of vapor. The resulting refrigerant flows out of the relay
unit 3 and flows again into the heat source device 1 through the
refrigerant pipes 4. In the heat source device 1, the refrigerant
is introduced into the heat source side heat exchanger 12 through
the check valve 13c, and the heat source side heat exchanger 12
serves as an evaporator. In the heat source side heat exchanger 12,
therefore, the low-temperature low-pressure two-phase refrigerant
is evaporated into a gas refrigerant and is drawn by suction into
the compressor 10 through the four-way valve 11 and the accumulator
17. At this time, the expansion valve 16e has an opening degree
small enough to prevent flow of the refrigerant.
[0071] A motion of a secondary heat medium (e.g., water or
antifreeze) will now be described. In the intermediate heat
exchanger 15a, heating energy of a primary refrigerant is
transmitted to a secondary heat medium, and a heated heat medium is
caused to flow through pipes on the secondary side by the pump 21a.
In the intermediate heat exchanger 15b, cooling energy of a primary
refrigerant is transmitted to the secondary heat medium, and the
cooled heat medium is caused to flow through pipes on the secondary
side by the pump 21b. The heat medium streams having flowed out of
the pumps 21a and 21b pass through the channel switching valves 22a
to 22d and the stop valves 24a to 24d, and flow into the use side
heat exchangers 26a to 26d and the flow control valves 25a to 25d.
At this time, the flow control valves 25a to 25d operate such that
only a part of the heat medium in an amount necessary for providing
an air-conditioning load required in the room flows in the use side
heat exchangers 26a to 26d, and the remaining part of the heat
medium passes through the bypasses 27a to 27d and does not
contribute to heat exchange. A heat medium stream having passed
through the bypasses 27a to 27d merges with a heat medium stream
having passed through the use side heat exchangers 26a to 26d, and
the heat medium passes through the channel switching valves 23a to
23d. Then, the hot heat medium flows into the intermediate heat
exchanger 15a and returns to the pump 21a, while the cold heat
medium flows into the intermediate heat exchanger 15b and returns
to the pump 21b. In this process, upon the operation of the channel
switching valves 22a to 22d and 23a to 23d, the hot and cold heat
media are not mixed and individually introduced into the use side
heat exchangers 26a to 26d having heating loads and cooling loads.
The air-conditioning load required in the room is provided by a
control operation in which the differences between the temperatures
detected by the third temperature sensors 33a to 33d and those
detected by the fourth temperature sensors 34a to 34d are kept at a
target value.
[0072] FIG. 7 illustrates a state in which a heating energy load is
generated in the use side heat exchanger 26a, and a cooling energy
load is generated in the use side heat exchanger 26b.
[0073] In this case, since it is unnecessary to supply a heat
medium to the use side heat exchangers (including thermo-off)
having no thermal loads, the channels are closed by the stop valves
24a to 24d so that no heat medium flows to these use side heat
exchangers. Referring to FIG. 7, since the use side heat exchangers
26a and 26b have thermal loads, the heat medium flows through them.
On the other hand, the use side heat exchangers 26c and 26d have no
thermal loads, and thus the corresponding stop valves 24c and 24d
are closed.
[0074] As described above, when heating loads are generated in the
use side heat exchangers 26a to 26d, the corresponding channel
switching valves 22a to 22d and 23a to 23d are switched to channels
connected to the intermediate heat exchanger 15a for heating. When
cooling loads are generated in the use side heat exchangers 26a to
26d, the corresponding channel switching valves 22a to 22d and 23a
to 23d are switched to channels connected to the intermediate heat
exchanger 15b for cooling. With this operation, the indoor unit 2
can freely perform a heating operation and a cooling operation.
[0075] The channel switching valves 22a to 22d and 23a to 23d may
adopt any type such as three-way valves that can switch three-way
channels or a combination of, for example, two types of shut-off
valves that open and close two-way channels, for example, as long
as the channel switching valves 22a to 22d and 23a to 23d can
switch the channels. The channel switching valve may also be
implemented using a valve such as a mixing valve of the
stepping-motor drive type that can change the flow rate of a
three-way channel or a combination of two valves such as electronic
expansion valves that can change the flow rate of two-way channels.
In this case, it is possible to prevent a water hammer produced
upon sudden opening or closing of a channel.
[0076] The thermal load in each of the use side heat exchangers 26a
to 26d is expressed as Equation (1), and obtained by multiplying
the flow rate, density, and specific heat at constant pressure of a
heat medium and the difference between the temperatures of the heat
medium at the inlet and outlet of each of the use side heat
exchangers 26a to 26d. In Equation (1), Vw is the flow rate of the
heat medium, .rho.w is the density of the heat medium, Cpw is the
specific heat at constant pressure of the heat medium, Tw is the
temperature of the heat medium, a suffix "in" symbolizes a value
for the heat medium at the inlet of each of the use side heat
exchangers 26a to 26d, and a suffix "out" symbolizes a value for
the heat medium at the outlet of each of the use side heat
exchangers 26a to 26d.
Q=V.sub.w(.rho..sub.winCp.sub.winT.sub.win-.rho..sub.woutCp.sub.woutT.su-
b.wout).apprxeq.V.sub.w.rho..sub.wCp.sub.w(T.sub.win-T.sub.wout)
[Math. 1]
[0077] When the flow rate of the heat medium flowing into the use
side heat exchangers 26a to 26d remains constant, the differences
between the temperatures of the heat medium at the inlets and
outlets of the heat medium vary depending on a change in thermal
load experienced by the use side heat exchangers 26a to 26d. Thus,
the flow control valves 25a to 25d are controlled such that the
differences between the temperatures of the heat medium at the
inlets and outlets of the use side heat exchangers 26a to 26d
approach a predetermined target value. With this operation, an
excess heat medium can be supplied into the bypasses 27a to 27d to
control the flow rate of the heat medium flowing into the use side
heat exchangers 26a to 26d. The target value of the differences
between the temperatures of the heat medium at the inlets and
outlets of the use side heat exchangers 26a to 26d is set at, for
example, 5 degrees C.
[0078] FIGS. 3 to 7 assume that the flow control valves 25a to 25d
are implemented using mixing valves located downstream of the use
side heat exchangers 26a to 26d. Alternatively, the flow control
valves 25a to 25d may be implemented using three-way valves located
upstream of the use side heat exchangers 26a to 26d.
Conventional Air-Conditioning Apparatus
[0079] In the air-conditioning apparatus of this embodiment, an
air-conditioning operation instruction issued from a terminal such
as a remote controller is transmitted to at least one of units
constituting the system, and an operation corresponding to this
instruction is performed. That is, when all instructions output
from the terminal such as the remote controller are associated with
a heating operation, the four-way valve 11, for example, is
controlled such that the control devices 100 and 300 perform a
heating only operation.
[0080] While a heating only operation, a cooling only operation, a
heating main operation, or a cooling main operation is performed, a
refrigerant and a heat medium on the refrigerant secondary side
exchange heat through the intermediate heat exchangers 15a and 15b,
and thus the temperature of the heat medium is kept constant.
[0081] However, when a suspension mode is set, the heat medium in
the heat medium pipes 5 exchanges heat with, for example, air
around the heat medium pipes 5. That is, the heat medium
temperature is affected by an ambient air temperature (e.g.,
outdoor air or indoor temperature). In this situation, the
temperature of the heat medium becomes unsuitable for a cooling or
heating operation especially in summer and winter. The suspension
mode refers to a mode in which the power supply of the
air-conditioning apparatus is on, but an air-conditioning operation
is temporarily stopped because, for example, an indoor space has
reached a target temperature. In this suspension mode, the stop of
the air-conditioning operation refers to a mode in which operation
of fans (not shown) provided to the compressor 10, the pumps 21a
and 21b, and the use side heat exchangers 26a to 26d are kept
stopped. In the suspension mode, although the heat source device 1
is kept stopped, the indoor unit 2 performs an air supply operation
in some cases.
[0082] In the case of transition from the suspension mode to a
cooling or heating operation, (1) air providing a feeling of draft
is supplied into the room; or (2) operation is performed with a
reduced amount of air blowing from the indoor unit for a long
period of time in order to reduce a feeling of draft.
[0083] More specifically, (1) in summer, the temperature of a heat
medium increases in the suspension mode. Thus, when the suspension
mode shifts to a cooling operation, the heat medium having an
increased temperature is supplied to the use side heat exchangers
26a to 26d. Accordingly, the temperature of air supplied into the
room through fans increases, providing a feeling of draft (a
feeling of excessive heat) to the user.
[0084] In winter, the temperature of a heat medium decreases in a
suspension mode. Thus, when the suspension mode shifts to a heating
operation, a heat medium having a reduced temperature is supplied
to the use side heat exchangers 26a to 26d. Accordingly, the
temperature of air supplied into the room through fans decreases,
providing a feeling of draft (a feeling of excessive cold) to the
user.
[0085] In addition, (2) the feeling of draft for (1) mentioned
above can be reduced by operation with a reduced volume of air from
fans until the temperature of the heat medium decreases (in the
case of summer) or the temperature of the heat medium increases (in
the case of winter). In these cases, however, the time required by
the room temperature to reach a target temperature increases.
[0086] In view of this, in the air-conditioning apparatus of this
embodiment, operation shown in the flowcharts of FIGS. 8 and 9 are
performed so that problems posed in (1) and (2) can be solved.
Heat Medium Temperature Adjustment Operation Mode
[0087] In the heat medium temperature adjustment operation mode,
when the pumps 21a and 21b are stopped after an operation of
preventing a heat medium from freezing, the temperature of the heat
medium that varies upon heating or cooling the heat medium through,
for example, outdoor air is set to fall within a predetermined
temperature range. More specifically, the air-conditioning
apparatus of this embodiment is configured to perform two heat
medium temperature adjustment operation modes.
[0088] (A) One of the two modes is enabled when the outdoor-air
temperature sensor 39 is not used. More specifically, in this mode,
although the air-conditioning apparatus of this embodiment includes
the outdoor-air temperature sensor 39, even if the air-conditioning
apparatus of this embodiment does not include the outdoor-air
temperature sensor 39, the heat medium temperature adjustment
operation mode can be performed.
[0089] (B) The other mode is used to perform a control operation
using the outdoor-air temperature sensor 39 in addition to the
above-mentioned control operation (A). More specifically, in this
mode the season is predicted based on a detection result obtained
by the outdoor-air temperature sensor 39 and a predetermined
temperature range, which is constant in control operation (A), is
changed.
[0090] As shown in FIGS. 6 and 7, the air-conditioning apparatus of
this embodiment includes a system capable of simultaneous cooling
and heating operations. Thus, the heat medium temperature
adjustment operation mode of the air-conditioning apparatus of this
embodiment can be used for either of cooling and heating modes.
[0091] FIG. 8 is a flowchart showing operation in the heat medium
temperature adjustment operation mode. The heat medium temperature
adjustment operation mode in the above-mentioned control operation
(A) will be described first. The control devices 100 and 500 will
be collectively referred to as a "control device" hereinafter.
(Step 1)
[0092] The control device determines whether the compressor 10 and
the pumps 21a and 21b have been kept stopped for a predetermined
time (e.g., one hour).
[0093] If the predetermined time has elapsed, the process proceeds
to step 2.
[0094] If the predetermined time has not elapsed, step 1 is
repeated.
(Step 2)
[0095] The control device drives the pumps 21a and 21b for a
predetermined time.
[0096] After driving the pumps 21a and 21b for the predetermined
time, the control device stops the pumps 21a and 21b again, and the
process proceeds to step 3.
[0097] Step 2 is a step for preventing the temperature around a
sensor from deviating from the average temperature of the heat
medium, and in step 2, the pumps 21a and 21b are driven for a
limited time.
(Step 3)
[0098] The control device determines whether the detection result
of the heat medium temperature Tw is equal to or greater than a
preset lower limit TL and equal to or less than a preset upper
limit TH. For example, supposing that the temperature as a
reference is 20 degrees C., it is determined whether the heat
medium temperature Tw falls within the range of .+-.5 degrees C.
(TL=15 degrees C., TH=25 degrees C.).
[0099] If the heat medium temperature Tw falls within the range,
the process returns to step 1.
[0100] If the heat medium temperature Tw does not fall within the
range, the process proceeds to step 4.
(Step 4)
[0101] The control device determines whether the detection result
of the heat medium temperature Tw is higher than a preset upper
limit TH (e.g., TH=25 degrees C.). More specifically, in step 4, it
is determined whether the water temperature exceeds the upper limit
of the temperature range serving as a reference.
[0102] If the heat medium temperature Tw is higher than TH, the
process proceeds to step 9.
[0103] If the heat medium temperature Tw is not higher than TH,
that is, lower than TL, the process proceeds to step 5.
(Step 5)
[0104] The control device controls various components so as to
perform a heating operation.
[0105] In step 5, to return an excessively reduced heat medium
temperature, which is lower than TL, to TL or more, operation is
performed in a heating mode.
[0106] Thus, to obtain flow of a refrigerant and a heat medium in
the heating only operation mode, the control device starts the
compressor 10, switches the four-way valve 11 to a heating mode,
starts the pump 21b, opens the expansion valves 16a, 16c, and 16e,
and closes the expansion valves 16b and 16d. The heat medium may be
heated by supplying the refrigerant and the heat medium similarly
to those in the heating main operation mode.
[0107] When fans provided to the indoor units 2a to 2d are in
operation, unnecessary wind is supplied into the room. Thus, the
amount of air blown by the indoor units 2a to 2d is set to provide
a breeze with no or little feeling of draft.
(Step 6)
[0108] The control device determines whether a predetermined time
has elapsed after execution of the heating operation of step 5. The
predetermined time is preferably determined in accordance with, for
example, the length and size of refrigerant pipes and branch
pipes.
[0109] If the predetermined time has elapsed, the process proceeds
to step 7.
[0110] If the predetermined time has not elapsed, step 6 is
repeated.
(Step 7)
[0111] The control device determines whether the detection result
of the heat medium temperature Tw is higher than a preset lower
limit TL+C (where C is an antihunting constant). That is, in step
7, it is determined whether the heat medium temperature Tw falls
within a range higher than TL+C.
[0112] If the heat medium temperature Tw exceeds TL+C, the process
proceeds to step 8.
[0113] If the heat medium temperature Tw does not exceed TL+C, step
7 is repeated. That is, since the heat medium temperature Tw does
not exceed TL+C, the heating operation continues until the heat
medium temperature Tw exceeds TL+C.
(Step 8)
[0114] The control device stops the heating operation. More
specifically, the control device stops the compressor 10 and the
pumps 21a and 21b. After step 8, the control device returns to step
1, that is, to a standby state.
(Step 9)
[0115] The control device controls various components so as to
perform a cooling operation.
[0116] In step 9, the heat medium temperature Tw is higher than TH,
and in order to return this excessively high heat medium
temperature to TH or less, operation is performed in a cooling
mode.
[0117] Thus, to obtain flow of a refrigerant and a heat medium in
the cooling only operation mode, the control device starts the
compressor 10, switches the four-way valve 11 to a cooling mode,
starts the pump 21a, opens the expansion valves 16b and 16d, and
closes the expansion valves 16a, 16c, and 16e. The heat medium may
be cooled by supplying the refrigerant and the heat medium
similarly to those in the cooling main operation mode.
[0118] When fans provided to the indoor units 2a to 2d are in
operation, unnecessary wind is supplied into the room. Thus, the
amount of air blown by the indoor units 2a to 2d is set to provide
a breeze with no or little feeling of draft.
(Step 10)
[0119] The control device determines whether a predetermined time
has elapsed after execution of the cooling operation of step 5. The
predetermined time is preferably determined in accordance with, for
example, the length and size of refrigerant pipes and branch
pipes.
[0120] If the predetermined time has elapsed, the process proceeds
to step 11.
[0121] If the predetermined time has not elapsed, step 10 is
repeated.
(Step 11)
[0122] The control device determines whether the detection result
of the heat medium temperature Tw is lower than a preset upper
limit TH-C (where C is an antihunting constant). That is, in step
11, it is determined whether the heat medium temperature falls
within a range lower than TH-C.
[0123] If the heat medium temperature Tw is lower than TH-C, the
process proceeds to step 12.
[0124] If the heat medium temperature Tw is not lower than TH-C,
step 11 is repeated. That is, since the heat medium temperature Tw
is not lower than TH-C, the cooling operation continues until the
heat medium temperature Tw falls below TH-C.
(Step 12)
[0125] The control device stops the cooling operation. More
specifically, the control device stops the compressor 10 and the
pumps 21a and 21b. After step 12, the control device returns to
step 1, that is, to a standby state.
[0126] Frequent start of the outdoor unit 1 (the compressor 10 and
the four-way valve 11) impairs energy saving performance, although
this is done for prevention of a feeling of draft. Thus, in steps 7
and 11, it is determined whether the heat medium temperature falls
within the range of TL to TH including the antihunting constant C
in order to prevent the outdoor unit 1 (the compressor 10 and the
four-way valve 11) from repeating on-off more frequently than
needed because of hunting of the heat medium temperature Tw.
[0127] FIG. 8 shows an example of determination as to whether the
heat medium temperature Tw falls within the range of .+-.5 degrees
C. (TL=15 degrees C., TH=25 degrees C.) when the reference
temperature is 20 degrees C. However, the present invention is not
limited to this example, and the reference temperature may be
arbitrarily selected.
[0128] It should be noted that when the reference temperature is
set to be close to an outdoor-air temperature of the intermediate
periods, the number of start operations of the outdoor unit 1 (the
compressor 10 and the four-way valve 11) decreases, and thereby, a
higher energy saving performance can be obtained.
[0129] That is, in the suspension mode of the air-conditioning
apparatus of this embodiment, the compressor 10 and the pumps 21a
and 21b are also driven such that the heat medium temperature is
kept within the predetermined range so as not to provide a feeling
of draft. Consequently, energy is consumed accordingly. However, in
this embodiment, the reference temperature is set at, for example,
a temperature close to an outdoor-air temperature of an
intermediate period, and thus energy consumption is reduced so that
the energy saving performance of the air-conditioning apparatus can
be enhanced.
[0130] In the air-conditioning apparatus of this embodiment, before
the control device drives the pumps 21a and 21b or at the same time
(including almost the same time) when the control device drives the
pumps 21a and 21b, the channel switching valves 22a to 22d and 23a
to 23d are switched so as to ensure the circulation channels of the
heat medium. With this operation, the heat medium in the heat
medium circulation circuit that has been heated or cooled in the
intermediate heat exchangers 15a and 15b is conveyed from the
intermediate heat exchangers 15a and 15b to the use side heat
exchangers 26a to 26d. Accordingly, temperature variations of the
heat medium can be reduced.
[0131] FIG. 9 is a flowchart showing the operation of the heat
medium temperature adjustment operation mode different from that
shown in FIG. 8.
[0132] In the operation shown in FIG. 8 above, the heat medium
temperature in the cooling operation or the heating operation is
kept within the predetermined temperature range, and even when the
cooling operation or the heating operation starts again, the heat
medium temperature can be rapidly cooled or heated to the target
temperature. That is, in the operation of FIG. 8, even while any
one of the cooling operation or the heating operation is performed,
the heat medium temperature can rapidly reach the target
temperature.
[0133] A heat medium temperature adjustment operation mode shown in
FIG. 9 is different from that of FIG. 8 in that the predetermined
temperature range is changed in accordance with the outdoor-air
temperature. More specifically, in the heat medium temperature
adjustment operation mode of FIG. 9, the upper and lower limits of
the predetermined temperature range shown in FIG. 8 is changed in
three patterns of summer, intermediate periods (spring and autumn),
and winter, in accordance with the average of the outdoor-air
temperature sampled in advance.
(Step 21)
[0134] The control device continuously samples the average
outdoor-air temperature and the heat medium temperature.
[0135] In this embodiment, the control device continuously samples
average outdoor-air temperatures and heat medium temperatures for
about one day or several days. Data sampled in step 21 is used to
determine a heat medium temperature serving as a reference in steps
24-1 to 24-3, which will be described later.
(Step 22)
[0136] The control device determines whether a predetermined time
(e.g., one hour) has elapsed after the stop of the compressor 10
and the pumps 21a and 21b.
[0137] If the predetermined time has elapsed, the process proceeds
to step 23.
[0138] If the predetermined time has not elapsed, step 22 is
repeated.
(Step 23-1)
[0139] The control device determines whether the average
outdoor-air temperature is lower than 10 degrees C.
[0140] If the average outdoor-air temperature is lower than 10
degrees C., the process proceeds to step 24-1.
[0141] The average outdoor-air temperature is not lower than 10
degrees C., the process proceeds to step 23-2.
(Step 23-2)
[0142] The control device determines whether the average
outdoor-air temperature is equal to or greater than 10 degrees C.
and falls within a range lower than 20 degrees C.
[0143] If the average outdoor-air temperature falls within the
range, the process proceeds to step 24-2.
[0144] If the average outdoor-air temperature does not fall within
the range, the process proceeds to step 24-3.
[0145] Although thresholds of 10 degrees C. and 20 degrees C. are
set in steps 3-1 and 3-2, they may be changed for, for example,
each region where the air-conditioning apparatus of this embodiment
is located, or each user demand.
(Step 24-1)
[0146] The control device sets the heat medium temperature as a
reference at 30 degrees C. Since the reference heat medium
temperature Twm is set at 30 degrees C., if the temperature width
of the heat medium is set at, for example, .+-.5 degrees C., then
the preset lower limit TLm is 25 degrees C., and the preset upper
limit THm is 35 degrees C.
[0147] Since the outdoor-air temperature is low in step 23-1, the
temperature is set assuming winter in step 24-1. That is, the next
operation mode is expected to be a heating mode, and the medium
temperature is set to be as relatively high as 30 degrees C.
(Step 24-2)
[0148] The control device sets the heat medium temperature Twm as a
reference at 20 degrees C. Since the reference heat medium
temperature Twm is set at 20 degrees C., if the temperature width
of the heat medium is set at, for example, .+-.5 degrees C., then
the preset lower limit TLm is 15 degrees C. and the preset upper
limit THm is 25 degrees C.
[0149] Since the outdoor-air temperature is equal to or higher than
10 degrees C. and lower than 20 degrees C. in step 23-2, the
temperature is set assuming an intermediate season (spring or
autumn) in the step 24-2. That is, since the next operation mode is
assumed to be both a heating mode and a cooling mode, the reference
temperature is set at 20 degrees C. so that the apparatus can cope
with both cooling and heating operations.
(Step 24-3)
[0150] The control device sets the heat medium temperature Twm as a
reference at 10 degrees C. Since the reference heat medium
temperature Twm is set at 10 degrees C., if the temperature width
of the heat medium is set at, for example, .+-.5 degrees C., then
the preset lower limit TLm is 5 degrees C. and the preset upper
limit THm is 15 degrees C.
[0151] Since the outdoor-air temperature is as high as 20 degrees
C. or more in step 23-2, the temperature is set assuming summer in
step 24-3. That is, since the next operation mode is expected to be
a cooling mode, the reference temperature is set to be as
relatively low as 10 degrees C.
[0152] In steps 24-1 to 24-3, the reference heat medium
temperatures Twm are set to 30 degrees C., 20 degrees C., and 10
degrees C. These temperatures Twm may be changed for, for example,
each region where the air-conditioning apparatus is located, or
each user demand. For example, by setting the reference heat medium
temperature Twm to be close to an average outdoor-air temperature
in each season, energy saving performance can further be
enhanced.
[0153] In steps 25 to 35 below, control operations corresponding to
steps 2 to 12 in FIG. 8 are performed.
(Step 25)
[0154] The control device drives the pumps 21a and 21b only for a
predetermined time.
[0155] After driving the pumps 21a and 21b for the predetermined
time, the control device stops the pumps 21a and 21b again, and the
process proceeds to step 26.
[0156] Similarly to step 2 in FIG. 8, step 25 is a step of
preventing an ambient temperature of sensors from deviating from
the average temperature of the heat medium due to a temperature
variation of the heat medium. In step 25, the pumps 21a and 21b are
driven for a limited time.
(Step 26)
[0157] The control device determines whether the detection result
of the heat medium temperature Tw is equal to or greater than the
preset lower limit TLm and equal to or less than the preset upper
limit THm. For example, when the process has reached step 26 by way
of step 24-2, the reference temperature is 20 degrees C., and it is
determined whether the heat medium temperature Tw falls within the
range of .+-.5 degrees C. (TLm=15 degrees C. and THm=25 degrees
C.).
[0158] If the heat medium temperature Tw falls within the range,
the process returns to step 21.
[0159] If the heat medium temperature Tw does not fall within the
range, the process proceeds to step 27.
(Step 27)
[0160] The control device determines whether the detection result
of the heat medium temperature Tw is higher than the preset upper
limit THm (e.g., THm=25 degrees C.). That is, in step 27, it is
determined whether the heat medium temperature Tw exceeds the upper
limit of the reference temperature range.
[0161] If the heat medium temperature Tw is higher than THm, the
process proceeds to step 32.
[0162] If the heat medium temperature Tw is higher than THm, that
is, lower than TLm, the process proceeds to step 28.
(Step 28)
[0163] The control device controls various components so as to
perform a heating operation.
[0164] In step 28, to return an excessively reduced heat medium
temperature, which is lower than TLm, to TLm or more, operation is
performed in a heating mode.
[0165] Thus, to obtain flow of a refrigerant and a heat medium in
the heating only operation mode, the control device starts the
compressor 10, switches the four-way valve 11 to a heating mode,
starts the pump 21b, opens the expansion valves 16a, 16c, and 16e,
and closes the expansion valves 16b and 16d. The heat medium may be
heated by supplying the refrigerant and the heat medium similarly
to those in the heating main operation mode.
[0166] When fans provided to the indoor units 2a to 2d are in
operation, unnecessary wind is supplied into the room. Thus, the
amount of air blown by the indoor units 2a to 2d is set to provide
a breeze with no or little feeling of draft.
(Step 29)
[0167] The control device determines whether a predetermined time
has elapsed after execution of the heating operation of step 29.
The predetermined time is preferably determined in accordance with,
for example, the length and size of refrigerant pipes and branch
pipes.
[0168] If the predetermined time has elapsed, the process proceeds
to step 30.
[0169] If the predetermined time has not elapsed, step 29 is
repeated.
(Step 30)
[0170] The control device determines whether the detection result
of the heat medium temperature Tw is higher than a preset lower
limit TLm+C (where C is an antihunting constant). That is, in step
30, it is determined whether the heat medium temperature falls
within a range higher than TLm+C.
[0171] If the heat medium temperature Tw exceeds TLm+C, the process
exceeds to step 31.
[0172] If the heat medium temperature Tw does not exceed TLm+C,
step 30 is repeated. That is, since the heat medium temperature Tw
does not exceed TLm+C, the heating operation continues until the
heat medium temperature Tw exceeds TLm+C.
(Step 31)
[0173] The control device stops the heating operation. More
specifically, the control device stops the compressor 10 and the
pumps 21a and 21b. After step 31, the control device returns to
step 21, that is, to a standby state.
(Step 32)
[0174] The control device controls various components so as to
perform a cooling operation.
[0175] In step 32, to return an excessively high heat medium
temperature, which is higher than THm, to THm or less, operation is
performed in a cooling mode.
[0176] Thus, to obtain flow of a refrigerant and a heat medium in
the cooling only operation mode, the control device starts the
compressor 10, switches the four-way valve 11 to a cooling mode,
starts the pump 21a, opens the expansion valves 16b and 16d, and
closes the expansion valves 16a, 16c, and 16e. The heat medium may
be cooled by supplying the refrigerant and the heat medium
similarly to those in the cooling main operation mode.
[0177] When fans provided to the indoor units 2a to 2d are in
operation, unnecessary wind is supplied into the room. Thus, the
amount of air blown by the indoor units 2a to 2d is set to provide
a breeze with no or little feeling of draft.
(Step 33)
[0178] The control device determines whether a predetermined time
has elapsed after execution of cooling operation of step 33. The
predetermined time is preferably determined in accordance with, for
example, the length and size of refrigerant pipes and branch
pipes.
[0179] If the predetermined time has elapsed, the process proceeds
to step 34.
[0180] If the predetermined time has not elapsed, step 33 is
repeated.
(Step 34)
[0181] The control device determines whether the detection result
of the heat medium temperature Tw is lower than a preset upper
limit THm-C (where C is an antihunting constant). That is, in step
34, it is determined whether the heat medium temperature falls
within a range lower than THm-C.
[0182] If the heat medium temperature Tw is lower than THm-C, the
process proceeds to step 35.
[0183] If the heat medium temperature Tw is not lower than THm-C,
step 34 is repeated. That is, since the heat medium temperature Tw
is not lower than THm-C, the cooling operation continues until the
heat medium temperature Tw falls below THm-C.
(Step 35)
[0184] The control device stops the cooling operation. More
specifically, the control device stops the compressor 10 and the
pumps 21a and 21b. After step 35, the control device returns to
step 21, that is, to a standby state.
[0185] As described earlier with reference to FIG. 9, the
air-conditioning apparatus of this embodiment expects the season on
the basis of the average outdoor-air temperature and determines a
target heat medium temperature. However, the present invention is
not limited to this example. Since the last operation mode is
expected to be performed again next, the control device may have
the function of recording the last operation mode. That is, when
the suspension mode is performed, the control device refers to the
record of the operation modes performed so far, and the next
operation is performed in the last operation mode performed by the
control device among the recorded operation modes.
[0186] Examples of the refrigerant include single-substance
refrigerants such as R-22 and R-134a, near-azeotropic refrigerant
mixtures such as R-410A and R-404A, zeotropic refrigerant mixtures
such as R-407C, refrigerants each including a double bond and
having a relatively low global warming potential such as
CF.sub.3CF.dbd.CH.sub.2, and mixtures of these refrigerants, and
natural refrigerants such as CO.sub.2 and propane.
[0187] In this embodiment, the refrigerant circuit includes the
accumulator, but may include no accumulator. The check valves 13a
to 13d are not necessary components, and similar operations and
advantages can be achieved with a circuit including no check valves
13a to 13d.
[0188] The heat source side heat exchanger 12 and the use side heat
exchangers 26a to 26d are preferably provided with air-sending
devices so that condensation or evaporation can be promoted by air
supply. However, the present invention is not limited to this
structure, and the use side heat exchangers 26a to 26d can be
implemented using, for example, a radiation panel heater. The heat
source side heat exchanger 12 can be implemented using a
water-cooled heat exchanger that transfers heat by means of water
or antifreeze, and can adopt any type as long as it can radiate or
absorb heat.
[0189] In the above-described example, the four use side heat
exchangers 26a to 26d are employed. However, the number of use side
heat exchangers is not limited.
[0190] The channel switching valves 22a to 22d and 23a to 23d, the
stop valves 24a to 24d, and the flow control valves 25a to 25d are
connected to the use side heat exchangers 26a to 26d in a
one-to-one correspondence. However, the present invention is not
limited to this example, and pluralities of channel switching
valves, stop valves, and flow control valves may be connected to
each use side heat exchanger. In this case, the channel switching
valves, the stop valves, and the flow control valves connected to
the same use side heat exchanger need only be operated in the same
manner.
[0191] In the above Embodiment, the intermediate heat exchanger 15a
for heating and the intermediate heat exchanger 15b for cooling are
provided. However, the present invention is not limited to this
structure. Simply performing either heating or cooling requires
only one intermediate heat exchanger. In this case, the heat medium
need not flow through another intermediate heat exchanger in the
heat medium temperature adjustment operation, and thus channels for
this flow are simplified. One or more sets of the heating
intermediate heat exchanger 15a and the cooling intermediate heat
exchanger 15b may be provided.
[0192] Instead of the flow control valves 25a to 25d of the
three-way channel type illustrated in, for example, FIG. 3, flow
control valves of the two-way channel type that can continuously
change the opening area using, for example, a stepping motor can be
used. Control in this case is similar to that when three-way
channel regulating valves are used, and the opening degrees of the
two-way channel regulating valves are adjusted to control the flow
rates of the heat medium into the use side heat exchangers 26a to
26d so that the differences between the temperatures of the heat
medium at the inlets an outlets of the use side heat exchangers 26a
to 26d reach a target value of, for example, 5 degrees C. Upon this
operation, the rotation speeds of the pumps 21a and 21b need only
be controlled such that the temperatures at the inlets or outlets
of the intermediate heat exchangers 15a and 15b take a
predetermined target value. The use of two-way channel regulating
valves as the flow control valves 25a to 25d advantageously
eliminates the necessity of the stop valves 24a to 24d and reduces
cost for constructing the system.
[0193] In the foregoing description, the flow control valves 25a to
25d, the third temperature sensors 33a to 33d, and the fourth
temperature sensors 34a to 34d are placed inside the relay unit 3.
However, the present invention is not limited to this example, and
the flow control valves 25a to 25d, the third temperature sensors
33a to 33d, and the fourth temperature sensors 34a to 34d can also
be placed near the use side heat exchangers 26a to 26d, that is,
inside or near the indoor unit 2. In this case, no substantial
problems occur in function, and similar operations and advantages
can be obtained. In the case of using two-way channel regulating
valves as the flow control valves 25a to 25d, the third temperature
sensors 33a to 33d and the fourth temperature sensors 34a to 34d
are placed inside or near the relay unit 3 and the flow control
valves 25a to 25d are placed inside or near the indoor unit 2.
[0194] In the air-conditioning apparatus of this embodiment having
the foregoing structure, when the temperature of the heat medium
falls outside a set temperature range, operations for adjusting the
heat medium temperature, such as operating the pumps, circulating
the heat medium, and intermittently starting the outdoor unit.
Then, wind providing little feeling of draft can be supplied into
the room, and the indoor temperature can reach a desired indoor
temperature in a relatively short time.
Advantages of Air-conditioning Apparatus of Embodiment
[0195] When the mode shifts to a suspension mode (the
air-conditioning operation temporarily stops) so that operations of
the compressor and the pumps temporarily stop, the temperature of
the heat medium varies due to factors associated with, for example,
outdoor air, and falls outside a predetermined temperature range in
some cases. In the air-conditioning apparatus of this embodiment,
however, when the temperature of the heat medium falls outside the
predetermined temperature range, the compressor 10 and the pumps
21a and 21b are driven so that the intermediate heat exchangers 15a
and 15b exchange heat between the refrigerant and the heat medium
and, thereby the temperature of the heat medium falls within the
predetermined temperature range. With this operation, wind
providing little feeling of draft can be supplied into the room
immediately after the start of operation, and an increase in time
taken for the temperature of the heat medium to reach the target
indoor temperature can be reduced.
* * * * *