U.S. patent application number 16/079607 was filed with the patent office on 2019-02-21 for air-conditioning apparatus.
The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Yutaka AOYAMA, Misaki KODA, Naomichi TAMURA.
Application Number | 20190056160 16/079607 |
Document ID | / |
Family ID | 60266467 |
Filed Date | 2019-02-21 |
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United States Patent
Application |
20190056160 |
Kind Code |
A1 |
KODA; Misaki ; et
al. |
February 21, 2019 |
AIR-CONDITIONING APPARATUS
Abstract
In plural heat-source-side heat exchangers included in an
outdoor unit of an air-conditioning apparatus, bypasses for
defrosting are provided with flow-rate adjusting mechanisms for
refrigerant flowing into the bypasses. The flow rates of the
refrigerant which are to be adjusted by the flow-rate adjusting
mechanisms are determined in accordance with ambient environments
of plural heat-source-side heat exchangers.
Inventors: |
KODA; Misaki; (Tokyo,
JP) ; TAMURA; Naomichi; (Tokyo, JP) ; AOYAMA;
Yutaka; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
60266467 |
Appl. No.: |
16/079607 |
Filed: |
May 11, 2016 |
PCT Filed: |
May 11, 2016 |
PCT NO: |
PCT/JP2016/064006 |
371 Date: |
August 24, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 47/022 20130101;
F25B 2313/0251 20130101; F25B 2700/21174 20130101; F25B 2313/005
20130101; F25B 13/00 20130101; F25B 2600/2515 20130101; F25B 41/04
20130101; F25B 2600/2513 20130101; F25B 2400/0403 20130101; F25B
2600/2501 20130101; F25B 41/062 20130101; F25B 2313/0233 20130101;
F25B 2313/02522 20130101; F25D 21/004 20130101; F25B 2313/009
20130101; F25B 2313/02741 20130101 |
International
Class: |
F25B 47/02 20060101
F25B047/02; F25D 21/00 20060101 F25D021/00; F25B 41/04 20060101
F25B041/04; F25B 41/06 20060101 F25B041/06 |
Claims
1. An air-conditioning apparatus comprising: an outdoor unit
including a compressor, a flow-path switching unit and plural
heat-source-side heat exchangers, the compressor, the flow-path
switching unit and the heat-source-side heat exchangers being
connected by pipes; and an indoor unit connected to the outdoor
unit to air-condition a target space, wherein the outdoor unit
includes: plural bypasses each having ends one of which is, in
connection by pipes in the outdoor unit, connected to a discharge
side of the compressor, and the other of which is connected to a
suction side of the compressor, the bypasses being configured to
cause refrigerant to flow through lower parts of the plural
heat-source-side heat exchangers during a defrost operation of the
air-conditioning apparatus; and flow-rate adjusting mechanisms
provided in the respective bypasses to adjust flow rates of
refrigerant flowing into the plural bypasses.
2. The air-conditioning apparatus of claim 1, wherein the outdoor
unit further comprises a controller and detection units configured
to detect ambient temperatures of the plural heat-source-side heat
exchangers, and the controller controls the flow-rate adjusting
mechanisms based on ambient temperatures which are detected by the
respective detection units of the plural heat-source-side heat
exchangers, and adjusts flow rates of the refrigerant flowing into
the bypasses, immediately after start of the defrost operation of
the air-conditioning apparatus, or after elapse of a set time from
the start of the defrost operation.
3. The air-conditioning apparatus of claim 2, wherein the flow-rate
adjusting mechanisms are electronic expansion valves, and the
controller adjusts opening degrees of the electronic expansion
valves.
4. The air-conditioning apparatus of claim 1, wherein the flow-rate
adjusting mechanisms are capillary tubes, and the flow rates of the
refrigerant flowing into the plural bypasses through the capillary
tubes are set different from each other with respect to the plural
heat-source-side heat exchangers.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air-conditioning
apparatus which is applied to, for example, a
multi-air-conditioning apparatus for a building.
BACKGROUND ART
[0002] When an air-conditioning apparatus performs a heating
operation during winter season, water vapor in the air adheres to a
heat exchanger in a heat source, and frost is formed on the heat
exchanger. If the frost still adheres to the heat exchanger, the
heating capacity lowers. Therefore, generally, a defrost operation
is performed by an outdoor unit during an interval between heating
operations to melt the frost adhering to the heat exchanger, to
thereby achieve a stable heating capacity.
[0003] When the defrost operation is performed, the frost formed on
the heat exchanger is melted into defrost water, which flows to a
lower part of the heat exchanger. In a cold region, the temperature
of such defrost water is low, and the temperature of outside air is
extremely low. Therefore, in the cold region, in the case where
such a defrost operation is performed in an air-conditioning
apparatus, defrost water sometimes refreezes when it flows to a
lower part of a heat exchanger. In order to prevent the defrost
water from being refrozen, a bypass is provided at a lowermost part
of the heat exchanger, and refrigerant having a high pressure and a
high temperature is made to flow into the bypass (patent literature
1).
CITATION LIST
Patent Literature
[0004] Patent Literature: Japanese Unexamined Patent Application
Publication No. 2006-64381
SUMMARY OF INVENTION
Technical Problem
[0005] In many cases, as multi-air-conditioning apparatuses for a
building, plural air-conditioning apparatuses are used. In this
case, outdoor units of the air-conditioning apparatuses are
arranged side by side, that is, they are arranged such that side
surfaces of any adjacent two of them face each other. In the case
where plural outdoor units are densely installed, the distance
between side surfaces of any adjacent two of the outdoor units is
only several centimeters. During the above defrost operation, fans
of the outdoor units of the air-conditioning apparatuses are
stopped, and only outside air thus passes through the outdoor
units. Therefore, in multi-air-conditioning apparatuses, in the
case where plural outdoor units are densely installed, during the
defrost operation, outside air more greatly influences upon front
and rear surfaces of the outdoor units than upon the side surfaces
of the outdoor units, which are spaced from each other by a slight
distance. As a result, defrost water tends to refreeze on the front
and rear surfaces of the outdoor units.
[0006] Also, in many cases, the external shape of an outdoor unit
is a substantially cuboid as a whole. The influence of outside air
upon the outdoor unit varies from one surface of the outdoor unit
to another surface thereof, since the surfaces of the outdoor unit
have different areas. Furthermore, the temperature of refrigerant
at part of the above bypass which is the farthest from a header of
the heat exchanger is lower than the temperature of refrigerant at
any of the other parts of the bypass. Therefore, in a single heat
exchanger, the temperature of a bypass for preventing refreeze is
not uniform over the bypass, a drainage performance is easily
worsened, and there is a possibility that refreeze will occur, and
whether or not refreeze occurs depends on the distance between part
of the bypass and the header.
[0007] The present invention has been made to solve the above
problem, and an object of the invention is to improve a defrosting
efficiency during a defrost operation in a multi-air-conditioning
apparatus in which plural outdoor units are installed, and to
prevent defrost water from being refrozen.
Solution to Problem
[0008] An air-conditioning apparatus according to an embodiment of
the present invention includes: an outdoor unit including a
compressor, a flow-path switching unit and plural heat-source-side
heat exchangers, the compressor, the flow-path switching unit and
the heat-source-side heat exchangers being connected by pipes; and
an indoor unit connected to the outdoor unit to air-condition a
target space, wherein the outdoor unit includes: plural bypasses
each having ends one of which is, in connection by pipes in the
outdoor unit, connected to a discharge side of the compressor, and
the other of which is connected to a suction side of the
compressor, the bypasses being configured to cause refrigerant to
flow through lower parts of the plural heat-source-side heat
exchangers during a defrost operation of the air-conditioning
apparatus; and flow-rate adjusting mechanisms respectively provided
in the plural bypasses to adjust flow rates of refrigerant flowing
into the plural bypasses.
Advantageous Effects of Invention
[0009] In the air-conditioning apparatus according to the
embodiment of the present invention, the plural bypasses configured
to cause the refrigerant to flow through lower parts of the plural
heat-source-side heat exchangers during the defrost operation are
provided with flow-rate adjusting mechanisms for adjusting the flow
rates of the refrigerant flowing into the bypasses. Therefore, in
the multi-air-conditioning apparatus for a building, even in the
case where the outdoor units are densely installed, the flow-rate
adjusting mechanisms are made to function in accordance with the
states of the installation of the outdoor units, whereby defrost
water generated during the defrost operation can be reliably
prevented from being refrozen.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a schematic diagram of a refrigerant circuit of an
air-conditioning apparatus.
[0011] FIG. 2 is a diagram illustrating flows of refrigerant during
a heating operation of the air-conditioning apparatus.
[0012] FIG. 3 is a diagram illustrating flows of refrigerant during
a defrost operation of the air-conditioning apparatus.
[0013] FIG. 4 is a schematic diagram of a heat-source-side heat
exchanger of the air-conditioning apparatus.
[0014] FIG. 5 is a diagram illustrating flows of refrigerant in the
case where a solenoid valve for a bypass is opened during the
defrost operation of the air-conditioning apparatus.
[0015] FIG. 6 is a diagram illustrating an example of dense
installation of outdoor units in embodiment 1 of the present
invention.
[0016] FIG. 7 is a schematic diagram of a refrigerant circuit of
the air-conditioning apparatus according to embodiment 1 of the
present invention.
[0017] FIG. 8 is a control block diagram of the air-conditioning
apparatus according to embodiment 1 of the present invention.
[0018] FIG. 9 is a schematic diagram illustrating heat-source-side
heat exchangers in embodiment 2 of the present invention as seen
from above.
[0019] FIG. 10 is a schematic diagram of a refrigerant circuit of
an air-conditioning apparatus according to embodiment 2 of the
present invention.
DESCRIPTION OF EMBODIMENTS
[0020] Refrigeration cycle devices according to embodiments of the
present invention will be described in detail with reference to the
drawings. It should be noted that the present invention is not
limited to the embodiments, which will be described below. With
respect to the figures to be referred to, there is a case where the
size of each of structural elements is different from that of an
actual apparatus.
[0021] FIG. 1 is a schematic diagram of a refrigerant circuit of an
air-conditioning apparatus. In the air-conditioning apparatus 100,
indoor units 10a, 10b, 10c and 10d are connected to an outdoor unit
(heat source unit) 20 by pipes A and B. The indoor units 10a, 10b,
10c and 10d are connected in parallel. The pipes A and B are
refrigerant pipes which allow refrigerant (heat-source-side
refrigerant) to flow therethrough.
[0022] The outdoor unit 20 includes a compressor 1, a flow-path
switching unit 2 such as a four-way valve, heat-source-side heat
exchangers 3a and 3b and an accumulator 5, which are connected by
pipes. The compressor 1 sucks refrigerant, compresses it to cause
it to have a high temperature and a high pressure, and transfers it
to a refrigerant circuit. The compressor is provided as, for
example, an inverter compressor the capacity of which can be
controlled. The flow-path switching unit 2 switches the flow of
refrigerant between the flow of refrigerant in a heating operation
mode and the flow of refrigerant in a cooling operation mode. The
heat-source-side heat exchangers 3a and 3b function as evaporators
in the heating operation mode and function as radiators in the
cooling operation mode and a defrost operation mode, and cause heat
exchange to be performed between the refrigerant and air supplied
by an air-sending device such as a fan (not shown). The
heat-source-side heat exchangers 3a and 3b are connected in
parallel by refrigerant pipes in the outdoor unit 20. The
heat-source-side heat exchangers 3a and 3b are formed in an L-shape
as their outer shape, and are arranged to form a rectangular frame
as a whole in a housing of the outdoor unit 20. The accumulator 5
is installed on a suction side of the compressor 1, and accumulates
surplus refrigerant which generates because of the difference
between the heating operation mode and the cooling operation mode,
and surplus refrigerant which generates because of a change in a
transient operation.
[0023] Bypasses 6a and 6b are connected to pipes in the outdoor
unit 20. In the pipes in the outdoor unit 20, one of the ends of
each of the bypasses 6a and 6b is connected to the discharge side
of the compressor 1, and the other is connected to the suction side
thereof. Furthermore, the bypass 6a extends through lower part of
the heat-source-side heat exchanger 3a, and the bypass 6b extends
through lower part of the heat-source-side heat exchanger 3b. Also,
the bypasses 6a and 6b are connected by pipes to a solenoid valve 4
which serves as an opening/closing unit. The refrigerant in the
pipes does not flow into the bypasses 6a and 6b when the solenoid
valve 4 is closed, and flows into the bypasses 6a and 6b when the
solenoid valve 4 is opened. The bypasses 6a and 6b and the solenoid
valve 4 are used to prevent melted frost from being refrozen after
the defrost operation of the air-conditioning apparatus 100.
[0024] In the indoor unit 10a, a use-side heat exchanger
(indoor-side heat exchanger) 12a and an expansion unit 11a are
connected in series to each other. In the indoor unit 10b, a
use-side heat exchanger 12b and an expansion unit 11b are connected
in series to each other. In the indoor unit 10c, a use-side heat
exchanger 12c and an expansion unit 11c are connected in series to
each other. In the indoor unit 10d, a use-side heat exchanger 12d
and an expansion unit 11d are connected in series to each other.
The use-side heat exchangers 12a, 12b, 12c and 12d function as
condensers in the heating operation mode, and function as
evaporators in the cooling operation mode, causes heat exchange to
be performed between refrigerant and air supplied by the
air-sending device (not shown) such as a fan, and generates air for
cooling or air for heating, which is to be supplied to a
to-be-air-conditioned space. The expansion units 11a, 11b, 11c and
11d have functions of pressure reducing valves and expansion
valves, and reduce the pressure of the refrigerant and expand the
refrigerant, and they are also provided as, for example, electronic
expansion valves whose opening degrees can be controlled to be
changed. In the air-conditioning apparatus 100, the four indoor
units 10a, 10b, 10c and 10d are connected in parallel. This,
however, is a mere example, and the number of indoor units is not
limited to four.
[0025] Each of operation modes of the air-conditioning apparatus
100 will be described.
[Heating Operation Mode]
[0026] FIG. 2 is a diagram illustrating flows of refrigerant during
the heating operation of the air-conditioning apparatus. In FIG. 2,
flows of refrigerant during the heating operation are indicated by
arrows. The following description is made referring to FIG. 2 with
respect to the case where all the indoor units 10a, 10b, 10c and
10d are operated. When gas refrigerant having a low temperature and
a low pressure is sucked into the compressor 1, it is compressed by
the compressor 1 to become gas refrigerant having a
high-temperature and a high and pressure, and is discharged from
the compressor 1. The gas refrigerant discharged from the
compressor 1 flows out from the outdoor unit 20 through the
flow-path switching unit 2 and the pipe A, and flows into the
use-side heat exchangers 12a, 12b, 12c and 12d.
[0027] In the use-side heat exchangers 12a, 12b, 12c and 12d, the
gas refrigerant having the high temperature and high pressure
exchanges heat with air supplied from the air-sending device not
shown, and thus becomes liquid refrigerant. The use-side heat
exchangers 12a, 12b, 12c and 12d function as condensers, which
transfer heat to the ambient air, and reduce the temperature of the
refrigerant in pipes in the heat exchangers. The liquid refrigerant
flows out from the use-side heat exchangers 12a, 12b, 12c and 12d
as liquid refrigerant having a high temperature and a high
pressure, and is expanded and reduced in pressure by the expansion
units 11a, 11b, 11c and 11d to become two-phase gas-liquid
refrigerant having a low temperature and a low pressure, and then
the two-phase gas-liquid refrigerant flows from the indoor units
10a, 10 b, 10c and 10 d. After flowing from the indoor units 10a,
10b, 10c and 10d, the two-phase gas-liquid refrigerant flows into
the outdoor unit 20 through the pipe B. After flowing into the
outdoor unit 20, in the heat-source-side heat exchangers 3a and 3b,
the two-phase gas-liquid refrigerant exchanges heat with air
supplied by the air-sending device (not shown) to become gas
refrigerant having a low temperature and a low pressure. The
heat-source-side heat exchangers 3a and 3b function as evaporators
that receive heat from the ambient air and evaporate the
refrigerant in the pipes. After flowing from the heat-source-side
heat exchangers 3a and 3b, the gas refrigerant flows into the
accumulator 5 through pipes and the flow-path switching unit 2 in
the outdoor unit 20. The refrigerant having flown into the
accumulator 5 is separated into liquid refrigerant and gas
refrigerant, and the gas refrigerant is sucked into the compressor
1.
[0028] When the heating operation is continued at a low external
temperature (at an evaporating temperature of 0 degrees C. or
less), frost forms on surfaces of the heat-source-side heat
exchangers 3a and 3b. This is because with moisture contained in
air to be subjected to heat exchange at the heat-source-side heat
exchangers 3a and 3b, dew condensation occurs at the surfaces of
the heat-source-side heat exchangers 3a and 3b, which serve as
evaporators, and the temperature of outside air is low, as a result
of which frost forms. When the quantity of frost forming on the
heat-source-side heat exchangers 3a and 3b increases, the thermal
resistance increases, and the quantity of air decreases.
Consequently, pipe temperatures (evaporating temperatures) in the
heat-source-side heat exchangers 3a and 3b lower, and the heating
capacity cannot be sufficiently fulfilled. It is therefore
necessary to perform defrosting to remove the frost.
[Defrost Operation Mode]
[0029] FIG. 3 is a diagram illustrating flows of refrigerant during
the defrost operation of the air-conditioning apparatus. In FIG. 3,
flows of refrigerant during the defrost operation mode are
indicated by arrows. In the defrost operation mode, a normal
heating operation is stopped, and the direction of circulation of
the refrigerant is changed by the flow-path switching unit 2 to the
same direction as that in the cooling operation mode. When gas
refrigerant having a low temperature and a low pressure is sucked
into the compressor 1, it is compressed by the compressor 1 to
become gas refrigerant having a high temperature and a high
pressure, and is discharged from the compressor 1. The gas
refrigerant discharged from the compressor 1 passes through the
flow-path switching unit 2, and flows into the heat-source-side
heat exchangers 3a and 3b. In the heat-source-side heat exchangers
3a and 3b, the gas refrigerant having the high temperature and high
pressure exchanges heat with the ambient air to become liquid
refrigerant. The heat-source-side heat exchangers 3a and 3b
function as condensers, which transfer heat to the ambient air and
reduce the temperature of refrigerant in the pipes. The heat
transferred by the heat-source-side heat exchangers 3a and 3b to
the air melts the frost on the surfaces of the heat-source-side
heat exchangers 3a and 3b. At this time, in many cases, the
air-sending device (not shown), which is located close to the
heat-source-side heat exchangers 3a and 3b, is in stopped state.
After flowing from the heat-source-side heat exchangers 3a and 3b,
the liquid refrigerant flows into the indoor units 10a, 10b, 10c
and 10d through the pipe B.
[0030] In the indoor units 10a, 10b, 10c and 10d, the liquid
refrigerant is expanded and reduced in pressure by the respective
expansion units 11a, 11b, 11c and 11d to become two-phase
gas-liquid refrigerant having a low temperature and a low pressure.
The two-phase gas-liquid refrigerant flows from the indoor units
10a, 10b, 10c and 10d without being subjected to heat exchange at
the use-side heat exchangers 12a, 12b, 12c and 12d. After flowing
from the indoor units 10a, 10b, 10c and 10d, the two-phase
gas-liquid refrigerant re-flows into the outdoor unit 20 through
the pipe A. In the outdoor unit 20, the two-phase gas-liquid
refrigerant passes through the flow-path switching unit 2, and
flows into the accumulator 5. The refrigerant having flown into the
accumulator 5 is separated into liquid refrigerant and gas
refrigerant, and the gas refrigerant is re-sucked into the
compressor 1.
[During Defrost Operation]
[0031] FIG. 4 is a schematic diagram of the heat-source-side heat
exchanger of the air-conditioning apparatus. FIG. 4 illustrates the
heat-source-side heat exchanger 3a as viewed side-on. FIG. 5 is a
diagram illustrating flows of refrigerant in the case where the
solenoid valve for the bypass is opened during the defrost
operation of the air-conditioning apparatus. The heat-source-side
heat exchanger 3a has a structure that plural heat transfer tubes
bent in a hairpin manner are inserted into plural fins in a
direction perpendicular thereto. The bypass 6a is provided to
extend through the lower part of the heat-source-side heat
exchanger 3a. Since the heat-source-side heat exchanger 3a is long
in a step direction, there is a possibility that after the defrost
operation, defrost water will be collected in the part of the
heat-source-side heat exchanger 3a through which the bypass 6a is
provided to extend, and will be refrozen. Therefore, as illustrated
in FIG. 5, in the defrost operation or in a last stage of the
defrost operation, the solenoid valve 4 is opened to cause the
refrigerant in the pipe to flow into the bypass 6a. As described
above, during the defrost operation, the refrigerant in the pipe in
the outdoor unit 20 has a high temperature and a high pressure.
Therefore, by causing the refrigerant to flow into the bypass 6a,
it is possible to enhance heating of the lower part of the
heat-source-side heat exchanger 3a. As a result, frost is prevented
from being re-frozen at the lower part of the heat-source-side heat
exchanger 3a. Similarly, the bypass 6b is provided to extend
through the lower part of the heat-source-side heat exchanger 3b,
and the solenoid valve 4 is connected to the bypass 6b. Therefore,
by opening the solenoid valve 4 in the late stage of the defrost
operation, the refrigerant having a high temperature and a high
pressure flows into the bypass 6b, and frost is prevented from
being refrozen at the lower part.
[0032] In ordinary cases, the defrost operation is ended when it is
confirmed that the entire frost adhering to the heat-source-side
heat exchangers 3a and 3b is completely melted, on the basis of
results of detection by temperature detection units (not shown)
provided at the heat-source-side heat exchangers 3a and 3b. When
the defrost operation is ended, the flow-path switching unit 2 is
switched, and the operation to be performed is returned to the
above heating operation. It is determined to end the defrost
operation, for example, by detecting an increase in the
temperatures of the pipes in the heat-source-side heat exchangers
3a and 3b, which is caused by removal of the entire frost.
[0033] In order to prevent frost from being refrozen after the
defrost operation, there is a case where it is necessary to
consider an influence of an environment in which the
air-conditioning apparatus 100, which causes refrigerant to be
circulated using the bypasses 6a and 6b as illustrated in FIG. 5,
is installed. In many cases, a multi-air-conditioning apparatus for
a building is used in a large-scale building or facility because of
its usage, and a large number of outdoor units are installed on the
rooftop. In this description, such installation of the outdoor
units of the multi-air-conditioning apparatus for a building is
referred to as a dense installation.
[0034] FIG. 6 is a diagram showing an example of dense installation
of the outdoor units in embodiment 1 of the present invention. FIG.
6, (a), illustrates a state of the dense installation of the
outdoor units as viewed side-on. FIG. 6, (b) to (e), illustrate a
state of the dense installation of the outdoor units as viewed from
above. In FIG. 6, (b) to (e), it is assumed that the front surface
of the units are surfaces thereof which faces upward in the figure,
and the rear surfaces of the units are surfaces thereof which face
downward in the figure. Also, in the figure, arrows indicate the
directions of wind.
[0035] As illustrated in FIG. 6, (a), in the dense installation, in
many cases, the intervals at which the outdoor units are arranged
laterally are very short. Of these outdoor units, in an outdoor
unit adjacent to other outdoor units on its both sides, the both
side surfaces of the outdoor unit respectively face side surfaces
of the above adjacent outdoor units, and the front and rear
surfaces of the outdoor unit are exposed to outside air at all
times. Also, in the dense installation, one of the side surfaces of
each of the outermost ones of the outdoor units faces a side
surface of an adjacent outdoor unit, and the other side surface and
the front and rear surfaces of the above each outermost outdoor
unit are exposed to outside air at all times. Therefore, the
influence of wind on the outdoor units varies from one outdoor unit
to another.
[0036] For example, in the case where wind flows as illustrated in
FIG. 6, (b), the front surfaces of the outdoor units are more
greatly influenced by the wind than the other surfaces of the
outdoor units: and in the case where wind flows as illustrated in
FIG. 6, (c), the rear surfaces of the outdoor units are more
greatly influenced by the wind than the other surfaces of the
outdoor units. Furthermore, in the case where wind flows as
illustrated in FIG. 6, (d), the left surface of the outermost left
one of the outdoor units as illustrated in the figure is more
greatly influenced by the wind than the other surfaces of the
outermost left outdoor unit and all the surfaces of the other
outdoor units, and in the case where wind flows as illustrated in
FIG. 6, (e), the right surface of the outermost right one of the
outdoor units as illustrated in the figure is more greatly
influenced by the wind than the other surfaces of the outermost
right outdoor unit and all the surfaces of the other outdoor
units.
[0037] In ordinary cases, in the case where the air-conditioning
apparatus is in the cooling operation or the heating operation, the
air-sending device is operated to cause wind to forcefully pass
through the heat-source-side heat exchangers. However, in the
defrost operation described above, the air-sending devices of the
outdoor units are stopped. During the defrost operation, if wind
flows as illustrated in FIG. 6, (b), a larger amount of outside air
comes into contact with the front surfaces of the outdoor units
than the other surfaces thereof, and if wind flows as illustrated
in FIG. 6, (c), a larger amount of outside air comes into contact
with the rear surfaces of the outdoor units than the other surfaces
thereof. Also, during the defrost operation, if wind flows as
illustrated in FIG. 6, (d), a larger amount of outside air comes
into contact with the left surface of the outermost left one of the
outdoor units as illustrated in the figure than the other surfaces
of the outermost left outdoor unit and all the surfaces of the
other outdoor units, and if wind flows as illustrated in FIG. 6,
(e), a larger amount of outside air comes into contact with the
right surface of the outermost right one of the outdoor units than
the other surfaces of the outermost right outdoor unit and all the
surfaces of the other outdoor units.
[0038] In forced convection, a value obtained by multiplying the
velocity of wind by 0.5 is proportional to a thermal conductivity.
Therefore, when the wind velocity increases by A times, a heat
radiation amount increases by A times. Therefore, in the defrost
operation mode, if wind flows as illustrated in FIG. 6, (b) or (c),
the heat radiation amounts of the front or rear surfaces of the
outdoor units are higher than those of the other surfaces of the
outdoor units, and heat is removed from the front or rear surfaces,
as a result of which there is a stronger possibility that defrost
water generated by the defrost operation will be refrozen on the
front or rear surfaces. Furthermore, if wind flows as illustrated
in FIG. 6, (d), the heat radiation amount of the left surface of
the outermost left one of the outdoor units as illustrated in the
figure is higher than those of the other surfaces of the outermost
left outdoor unit and all the surfaces of the other outdoor units
radiation rate, and heat is removed from the left surface of the
outermost left outdoor unit, as a result of which there is a
stronger possibility that defrost water generated by the defrost
operation will be refrozen on the left surface of the outermost
left outdoor unit. If wind flows as illustrated FIG. 6, (e), the
heat radiation amount of the right surface of the outermost right
one of the outdoor units as illustrated in the figure is higher
than those of the other surfaces of the outermost right outdoor
unit and all the surfaces of the other outdoor units, and heat is
removed from the right surface of the outermost right outdoor unit,
and there is a stronger possibility that defrost water generated by
the defrost operation will be refrozen on the right surface of the
outermost right outdoor unit.
Embodiment 1
[0039] FIG. 7 is a schematic diagram of a refrigerant circuit of an
air-conditioning apparatus according to embodiment 1 of the present
invention. Structural elements which are the same as those of the
above refrigerant circuit as illustrated in FIG. 1 to 3 will be
denoted by the same reference signs, and their descriptions will
thus be omitted. In the air-conditioning apparatus 200 according to
embodiment 1, the bypass 6a includes an electronic expansion valve
7a serving as a flow-rate adjusting mechanism, and a thermistor 8a
serving as a temperature detection unit. The electronic expansion
valve 7a and the thermistor 8a are provided on a secondary side of
the bypass 6a, with the heat-source-side heat exchanger 3a
interposed between the electronic expansion valve 7a and thermistor
8a and secondary side of the bypass 6a. Similarly, the bypass 6b
includes an electronic expansion valve 7b serving as a flow-rate
adjusting mechanism, and a thermistor 8b serving as a temperature
detection unit. The electronic expansion valve 7b and the
thermistor 8b are provided on a secondary side of the bypass 6b,
with the heat-source-side heat exchanger 3b interposed between the
electronic expansion valve 7b and thermistor 8b and the secondary
side of the bypass 6b. A temperature sensor 9a which detects an
outlet temperature of the heat-source-side heat exchanger 3a, i.e.,
the temperature of an outlet thereof from which refrigerant flows,
is provided at the heat-source-side heat exchanger 3a; and a
temperature sensor 9b which detects an outlet temperature of the
heat-source-side heat exchanger 3b, i.e., the temperature of an
outlet thereof from which the refrigerant flows, is provided at the
heat-source-side heat exchanger 3b.
[0040] When the solenoid valve 4 is opened, and an opening degree
of the electronic expansion valve 7a reaches a predetermined
opening degree, gas refrigerant having a high temperature and a
high pressure starts to flow into the bypass 6a. After flowing into
the bypass 6a, the gas refrigerant having the high temperature and
high pressure exchanges heat with defrost water, at the lower part
of the heat-source-side heat exchanger 3a. As a result, while
liquefying, the gas refrigerant having the high temperature and
high pressure heats the bypass 6a of the heat-source-side heat
exchanger 3a. Thus, the defrost water is prevented from being
refrozen. When the solenoid valve 4 is opened, and the opening
degree of the electronic expansion valve 7b reaches a predetermined
opening degree, the gas refrigerant having the high temperature and
high pressure starts to flow into the bypass 6b. After flowing into
the bypass 6b, the gas refrigerant having the high temperature and
high pressure exchanges heat with defrost water, at the lower part
of the heat-source-side heat exchanger 3b. As a result, while
liquefying, the gas refrigerant having the high temperature and
high pressure heats the bypass 6b of the heat-source-side heat
exchanger 3b. Thus, the defrost water is prevented from being
refrozen.
[0041] FIG. 8 is a control block diagram of the air-conditioning
apparatus 200. A controller 201 controls the entire
air-conditioning apparatus 200. The temperature sensor 9a, a
temperature sensor 9b, the thermistor 8a and a thermistor 8b are
connected to the controller 201. Also, the solenoid valve 4, the
electronic expansion valve 7a and an electronic expansion valve 7b
are connected to the controller 201. The controller 201 outputs a
signal for opening the solenoid valve 4 to the solenoid valve 4,
when the outlet temperature of the heat-source-side heat exchanger
3a detected by the temperature sensor 9a becomes a predetermined
temperature or higher immediately after start of the defrost
operation or after elapse of a predetermined time from the start of
the defrost operation. Also, the controller 201 detects the
temperature of the thermistor 8a to determine the opening degree of
the electronic expansion valve 7a, and outputs a control signal
based on the result of the determination to the electronic
expansion valve 7a. Similarly, the controller 201 outputs a signal
for opening the solenoid valve 4 to the solenoid valve 4, when the
outlet temperature of the heat-source-side heat exchanger 3b
detected by the temperature sensor 9b becomes the predetermined
temperature or higher. Also, the controller 201 detects the
temperature of the thermistor 8b to determine the opening degree of
the electronic expansion valve 7b, and outputs a control signal
based on the result of the determination to the electronic
expansion valve 7b. To be more specific, the opening degrees of the
electronic expansion valves 7a and 7b are determined on the basis
of the differences (.DELTA.T=T*+T) between target temperatures T*
and the detected temperatures T of the thermistors 8a and 8b,
respectively. When .DELTA.T>0, the controller 201 outputs
control signals for increasing the opening degrees of the
electronic expansion valves 7a and 7b, and when .DELTA.T<0, the
controller 201 outputs control signals for decreasing the opening
degrees of the electronic expansion valves 7a and 7b.
[0042] As described above, according to embodiment 1, in addition
to control of opening of the solenoid valve 4, control of the
opening degrees of the electronic expansion valves 7a and 7b based
on the detection results of the thermistors 8a and 8b is performed,
and the flow rates of refrigerant to the bypasses 6a and 6b are
adjusted in accordance with ambient environments of the
heat-source-side heat exchangers 3a and 3b. In other words, the
defrosting capacities of the heat-source-side heat exchangers 3a
and 3b are adjusted in accordance with the ambient environments
thereof. Therefore, the flow rates of the refrigerant to the
bypasses 6a and 6b can be optimized in accordance with defrosting
loads on the bypasses 6a and 6b. As a result, even if the
influences of wind of outside air upon the surfaces of the
heat-source-side heat exchangers 3a and 3b vary in accordance with
the positions of the outdoor units in the dense installation as
described with reference to FIG. 6, (a) to 6(e), it is possible to
reliably prevent defrost water from being refrozen in accordance
with the influences.
Embodiment 2
[0043] FIG. 10 is a schematic diagram of a refrigerant circuit of
an air-conditioning apparatus according to embodiment 2 of the
present invention. With respect to this embodiment, structural
elements which are the same as those of the refrigerant circuit as
illustrated in FIG. 1 to 3 will be denoted by the same reference
signs, and their descriptions will thus be omitted. In an
air-conditioning apparatus 300 according to embodiment 2, a pipe
resistor 15a is provided in the bypass 6a, and a pipe resistor 15b
is provided in the bypass 6b. The pipe resistors 15a and 15b are,
for example, capillary tubes. The inflow rate of refrigerant to the
bypass 6a is determined in accordance with the pipe resistor 15a.
The inflow rate of the refrigerant to the bypass 6b is determined
in accordance with the pipe resistor 15b. Flow resistances of the
pipe resistors 15a and 15b to the flow of the refrigerant are set
different from each other to cause the flow rates of the
refrigerant to the bypasses 6a and 6b to differ from each
other.
[0044] The following description is given by referring to by way of
example the case where the plural outdoor units 20 in the
multi-air-conditioning apparatus for a building are densely
installed, and wind of outside air flows in the direction indicated
in FIG. 6, (b) or (c). FIG. 9 is a schematic diagram illustrating
heat-source-side heat exchangers in embodiment 2 of the present
invention as viewed from above. The heat-source-side heat
exchangers 3a and 3b are L-shaped, and are provided to form a frame
that is substantially rectangular as viewed from above in the
housing of the outdoor unit 20. The heat-source-side heat exchanger
3a is provided on the front surface of the outdoor unit 20. In FIG.
9, the front surface of the outdoor unit 20 faces downward in the
figure. Also, referring to FIG. 9, an inlet 13a and an outlet 13b
are an inlet and an outlet of the bypass 6a of the heat-source-side
heat exchanger 3a, respectively; and an inlet 14a and an outlet 14b
are an inlet and an outlet of the bypass 6b of the heat-source-side
heat exchanger 3b, respectively. In the case where wind of outside
air flows in the direction indicated in FIG. 6, (b) or (c), a
surface 16a of the heat-source-side heat exchanger 3a is a surface
thereof onto which the wind flows, and a surface 16b of the
heat-source-side heat exchanger 3a is a surface thereof onto which
the wind flows.
[0045] The inlet 13a of the bypass 6a of the heat-source-side heat
exchanger 3a is located close to the surface 16a onto which the
wind flows. Refrigerant gas having a high temperature flows into
part of the surface 16a of the heat-source-side heat exchanger 3a.
On the other hand, the inlet 14a of the bypass 6b of the
heat-source-side heat exchanger 3b is located on a side of a side
surface thereof which is orthogonal to the surface 16b onto which
the wind flows. The refrigerant gas passes through part of the side
surface of the heat-source-side heat exchanger 3b, and flows into
part of the surface 16b. Thus, the temperature of the refrigerant
gas flowing into the part of the surface 16b of the
heat-source-side heat exchanger 3b lowers, as compared with the
temperature of the refrigerant gas flowing into the part of the
surface 16a of the heat-source-side heat exchanger 3a. Therefore,
the defrosting capacity of the heat-source-side heat exchanger 3b
needs to be set higher than the defrosting capacity of the
heat-source-side heat exchanger 3a. In embodiment 2, the flow
resistance of the pipe resistor 15b is set lower than the flow
resistance of the pipe resistor 15a.
[0046] In such a manner, according to embodiment 2, in the dense
installation in the multi-air-conditioning apparatus for a
building, in the case where it is known which of the defrosting
capacities requisite for the heat-source-side heat exchangers 3a
and 3b of each of the outdoor units 20 is greater or smaller, pipe
resistors 15a and 15b whose flow resistances are set in accordance
with the requisite defrosting capacities are provided.
[0047] According to embodiment 2, it is possible to reduce
increasing of the number of components. Therefore, in the dense
installation, in the case where it is known which of defrosting
capacities which are requisite for the heat-source-side heat
exchangers 3a and 3b in accordance with the position of each of
installed outdoor units is greater or smaller, the defrost water at
the heat-source-side heat exchangers 3a and 3b can be prevented
from being refrozen, at the same time as the product cost is
reduced.
TABLE-US-00001 Reference Signs List 1 compressor 2 flow-path
switching unit 3a heat-source-side heat exchanger 3b
heat-source-side heat exchanger 4 solenoid valve 5 accumulator 6a
bypass 6b bypass 7a electronic expansion valve 7b electronic
expansion valve 8a thermistor 8b thermistor 9a temperature sensor
9b temperature sensor 10a indoor unit 10b indoor unit 10c indoor
unit 10d indoor unit 11a expansion unit 11b expansion unit 11c
expansion unit 11d expansion unit 12a use-side heat exchanger 12b
use-side heat exchanger 12c use-side heat exchanger 12d use-side
heat exchanger 13a inlet 13b outlet 14a inlet 14b outlet 15a pipe
resistor 15b pipe resistor 16a surface 16b surface 20 outdoor unit
100 air-conditioning apparatus 200 air-conditioning apparatus 201
controller 300 air-conditioning apparatus.
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