U.S. patent application number 15/543289 was filed with the patent office on 2017-12-21 for air-conditioning apparatus.
The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Kohei KASAI, Yohei KATO, Hirokazu MINAMISAKO, Takafumi MITO, Tsubasa TANDA, Shinichi UCHINO, Satoru YANACHI.
Application Number | 20170363332 15/543289 |
Document ID | / |
Family ID | 56689320 |
Filed Date | 2017-12-21 |
United States Patent
Application |
20170363332 |
Kind Code |
A1 |
YANACHI; Satoru ; et
al. |
December 21, 2017 |
AIR-CONDITIONING APPARATUS
Abstract
An air-conditioning apparatus includes a fan configured to
deliver air toward the outdoor heat exchanger, a power unit
configured to supply electric power to the fan, a fan input
detector configured to detect a physical value related to the
electric power supplied to the fan, and a controller configured to
control the four-way valve to switch between a first operation in
which the outdoor heat exchanger functions as an evaporator and a
second operation in which the outdoor heat exchanger functions as a
condenser. The first operation is switched to the second operation
when the physical value detected by the fan input detector is equal
to or larger than a reference value. The controller adjusts the
reference value so that the reference value when refrigerant
flowing through the outdoor heat exchanger has a high temperature
is smaller than the reference value when the refrigerant has a low
temperature.
Inventors: |
YANACHI; Satoru; (Tokyo,
JP) ; KATO; Yohei; (Tokyo, JP) ; KASAI;
Kohei; (Tokyo, JP) ; UCHINO; Shinichi; (Tokyo,
JP) ; MINAMISAKO; Hirokazu; (Tokyo, JP) ;
MITO; Takafumi; (Tokyo, JP) ; TANDA; Tsubasa;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
56689320 |
Appl. No.: |
15/543289 |
Filed: |
February 18, 2015 |
PCT Filed: |
February 18, 2015 |
PCT NO: |
PCT/JP2015/054402 |
371 Date: |
July 13, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F24F 11/86 20180101;
F24F 11/67 20180101; F25B 2700/15 20130101; F25B 49/022 20130101;
F25B 2313/0315 20130101; F24F 11/42 20180101; F25B 13/00 20130101;
F25B 2313/0294 20130101; F24F 2140/60 20180101; F25B 2600/0253
20130101; F24F 11/89 20180101; F24F 11/64 20180101 |
International
Class: |
F25B 13/00 20060101
F25B013/00; F25B 49/02 20060101 F25B049/02 |
Claims
1. An air-conditioning apparatus comprising: a compressor, an
outdoor heat exchanger; an indoor heat exchanger; a switching
device, the switching device being provided closer to a discharge
side of the compressor than the outdoor heat exchanger and provided
closer to the discharge side of the compressor than the indoor heat
exchanger, the compressor, the outdoor heat exchanger, the indoor
heat exchanger, and the switching device being connected one
another; a fan configured to deliver air toward the outdoor heat
exchanger; a power unit configured to supply electric power to the
fan; a fan input detector configured to detect a physical value
correlated to the electric power supplied to the fan; and a
controller configured to control the switching device to switch
between a first operation in which the outdoor heat exchanger
serves as an evaporator and a second operation in which the outdoor
heat exchanger serves as a condenser, wherein the first operation
is switched to the second operation when the physical value
detected by the fan input detector is equal to or larger than a
reference value, and wherein the controller is configured to adjust
the reference value such that the reference value when a
refrigerant temperature flowing in the outdoor heat exchanger is
high to be lower than the reference value when the refrigerant
temperature flowing in the outdoor heat exchanger is low.
2. An air-conditioning apparatus comprising: a compressor; an
outdoor heat exchanger; an indoor heat exchanger; a switching
device, the switching device being provided closer to a discharge
side of the compressor than the outdoor heat exchanger and provided
closer to the discharge side of the compressor than the indoor heat
exchanger, the compressor, the outdoor heat exchanger, the indoor
heat exchanger, and the switching device being connected one
another; a fan configured to deliver air toward the outdoor heat
exchanger; a power unit configured to supply electric power to the
fan; a fan input detector configured to detect a physical value
correlated to the electric power supplied to the fan; and a
controller configured to control the switching device to switch
between a first operation in which the outdoor heat exchanger
serves as an evaporator and a second operation in which the outdoor
heat exchanger serves as a condenser, wherein the first operation
is switched to the second operation when the physical value
detected by the fan input detector is equal to or larger than a
reference value, and wherein the controller is configured to
control the compressor such that frequency of the compressor when a
refrigerant temperature flowing in the outdoor heat exchanger is
high to be higher than the frequency of the compressor when the
refrigerant temperature flowing in the outdoor heat exchanger is
low.
3. The air-conditioning apparatus of claim 1, wherein the fan input
detector detects a current value or a voltage value applied to an
outdoor side motor configured to drive the fan, or electric power
based on the current value and the voltage value.
4. The air-conditioning apparatus of claim 2, wherein fan input
detector detects a current value or a voltage value applied to an
outdoor side motor configured to drive the fan, or electric power
based on the current value and the voltage value.
Description
TECHNICAL FIELD
[0001] The present invention relates to an air-conditioning
apparatus.
BACKGROUND ART
[0002] A conventional air-conditioning apparatus detects, in a
heating operation, the current value of an outdoor fan motor and
the rotation speed of an outdoor fan, and determines whether to
start a defrosting operation based on whether the current value of
the outdoor fan motor becomes equal to or larger than a reference
current value or the rotation speed of the outdoor fan decreases by
a predetermined rotation speed (refer to Patent Literature 1).
CITATION LIST
Patent Literature
[0003] Patent Literature 1: Japanese Unexamined Patent Application
Publication No. 2009-58222
SUMMARY OF INVENTION
Technical Problem
[0004] In the air-conditioning apparatus disclosed in Patent
Literature 1, the reference current value is determined in advance
and cannot be changed with taken into account decrease in a fan
input due to decrease in the fan rotation speed when the efficiency
of the outdoor fan motor degrades by aging. This configuration
prevents transition to the defrosting operation at appropriate
timing in the heating operation. In other words, defrosting cannot
be performed efficiently.
[0005] The present invention is intended to solve the
above-described problem and provide an air-conditioning apparatus
that performs a defrosting operation more efficiently than
conventionally practiced.
Solution to Problem
[0006] An air-conditioning apparatus according to an embodiment of
the present invention includes, by connecting, a compressor, an
outdoor heat exchanger, an indoor heat exchanger, and a switching
device, the switching device being provided closer to a discharge
side of the compressor than the outdoor heat exchanger and provided
closer to the discharge side of the compressor than the indoor heat
exchanger. The air-conditioning apparatus includes a fan configured
to deliver air toward the outdoor heat exchanger, a power unit
configured to supply electric power to the fan, a fan input
detector configured to detect a physical value related to the
electric power supplied to the fan, and a controller configured to
control the switching device to switch between a first operation in
which the outdoor heat exchanger functions as an evaporator and a
second operation in which the outdoor heat exchanger functions as a
condenser. The first operation is switched to the second operation
when the physical value detected by the fan input detector is equal
to or larger than a reference value. The controller adjusts the
reference value so that the reference value when refrigerant
flowing through the outdoor heat exchanger has a high temperature
is smaller than the reference value when the refrigerant has a low
temperature.
Advantageous Effects of Invention
[0007] The air-conditioning apparatus according to an embodiment of
the present invention includes the controller configured to control
the switching device to switch between the first operation in which
the outdoor heat exchanger functions as an evaporator and the
second operation in which the outdoor heat exchanger functions as a
condenser. The first operation is switched to the second operation
when the physical value detected by the fan input detector is equal
to or larger than the reference value. The controller adjusts the
reference value so that the reference value when the refrigerant
flowing through the outdoor heat exchanger has a high temperature
is smaller than the reference value when the refrigerant flowing
through the outdoor heat exchanger has a low temperature. With this
configuration, a defrosting operation can be started at an
appropriate timing while a heating operation is being performed.
Thus, the defrosting operation can be performed more efficiently
than has been conventionally practiced.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a schematic view illustrating an air-conditioning
apparatus 100 according to Embodiment 1 of the present
invention.
[0009] FIG. 2 is a diagram illustrating change in a frosting amount
and total electric power with elapsed time in the air-conditioning
apparatus 100 according to Embodiment 1 of the present
invention.
[0010] FIG. 3 is a diagram illustrating change in the frosting
amount and total current value with elapsed time in the
air-conditioning apparatus 100 according to Embodiment 1 of the
present invention.
[0011] FIG. 4 is a diagram illustrating change in an electric power
amount with elapsed time in the air-conditioning apparatus 100
according to Embodiment 1 of the present invention.
[0012] FIG. 5 is a diagram illustrating change in a total electric
power amount with elapsed time in the air-conditioning apparatus
100 according to Embodiment 1 of the present invention.
[0013] FIG. 6 is a schematic view illustrating a state in which
frost exists on an outdoor heat exchanger 3 of the air-conditioning
apparatus 100 according to Embodiment 1 of the present
invention.
[0014] FIG. 7 is a diagram illustrating a relation between a
relative humidity .phi. and a frost density .rho. in the
air-conditioning apparatus 100 according to Embodiment 1 of the
present invention.
[0015] FIG. 8 is a diagram illustrating a relation between a
refrigerant temperature and a necessary defrosting heat amount in
the air-conditioning apparatus 100 according to Embodiment 1 of the
present invention.
[0016] FIG. 9 is a diagram illustrating change in the frequency of
a compressor 1 with elapsed time in the air-conditioning apparatus
100 according to Embodiment 1 of the present invention.
[0017] FIG. 10 is a diagram illustrating change in the frequency of
the compressor 1 with elapsed time in the air-conditioning
apparatus 100 according to Embodiment 1 of the present
invention.
DESCRIPTION OF EMBODIMENTS
Embodiment 1
[0018] An air-conditioning apparatus 100 of the present invention
will be described in detail below with reference to the drawings.
The sizes of components in the drawings are in a relation different
from that of their actual sizes in some cases. In the drawings, any
components denoted by an identical reference sign are identical or
equivalent to each other. This notation applies through the entire
specification. In addition, any configuration of the components
described in the entire specification is merely exemplary, and thus
the present invention is not limited by the description.
[0019] FIG. 1 is a schematic view illustrating the air-conditioning
apparatus 100 according to Embodiment 1 of the present invention.
As illustrated in FIG. 1, the air-conditioning apparatus 100
includes a compressor 1, a four-way valve 2, an outdoor heat
exchanger 3, an expansion valve 4, and an indoor heat exchanger 5.
The compressor 1, the four-way valve 2, the outdoor heat exchanger
3, the expansion valve 4, and the indoor heat exchanger 5 are, for
example, sequentially connected by pipes to form a refrigerant
circuit 90.
[0020] The compressor 1 is a variable capacity compressor
configured to compress sucked refrigerant and discharge the
refrigerant as high-temperature and high-pressure refrigerant. The
four-way valve 2 is a switching device that switches a direction in
which the refrigerant discharged from the compressor 1 flows, in
response to, for example, execution of a heating operation or a
cooling operation. The four-way valve 2 is provided closer to the
discharge side of the compressor 1 than the outdoor heat exchanger
3 and provided closer to the discharge side of the compressor 1
than the indoor heat exchanger 5. FIG. 1 illustrates an exemplary
state in which the four-way valve 2 is switched to perform a
cooling operation. In FIG. 1, a solid line arrow indicates the flow
of the refrigerant when the cooling operation is performed. In FIG.
1, a dashed line arrow indicates the flow of the refrigerant when a
heating operation is performed.
[0021] The outdoor heat exchanger 3 is a heat exchanger configured
to function as a condenser at the cooling operation and function as
an evaporator at the heating operation. An outdoor side fan 31 is
an air-sending unit configured to supply external air to the
outdoor heat exchanger 3 and form airflow. The outdoor side fan 31
is, for example, an axial-flow fan or a centrifugal fan. The
outdoor side fan 31 rotates when an outdoor side motor (not
illustrated) is driven. Heat is exchanged between the air supplied
from the outdoor side fan 31 and the refrigerant flowing inside the
outdoor heat exchanger 3. The outdoor side fan 31 is driven by a
power unit (not illustrated) configured to supply electric
power.
[0022] The expansion valve 4 is used to decompress and expand the
refrigerant flowed out of the outdoor heat exchanger 3 at the
cooling operation, and decompress and expand the refrigerant flowed
out of the indoor heat exchanger 5 at the heating operation.
[0023] The indoor heat exchanger 5 is a heat exchanger configured
to function as an evaporator at the cooling operation and function
as a condenser at the heating operation. An indoor side fan 51 is
an air-sending unit configured to supply indoor air to the indoor
heat exchanger 5 and form airflow. The indoor side fan 51 is, for
example, an axial-flow fan or a centrifugal fan. The indoor side
fan 51 rotates when an indoor side motor (not illustrated) is
driven. Heat is exchanged between the air supplied from the indoor
side fan 51 and the refrigerant flowing inside the indoor heat
exchanger 5.
[0024] An outdoor side refrigerant temperature sensor 32 is a
temperature detection unit configured to detect the temperature of
the refrigerant flowing through the outdoor heat exchanger 3. An
indoor side refrigerant temperature sensor 52 is a sensor
configured to detect the temperature of the refrigerant flowing
through the indoor heat exchanger 5. In the following description,
a "refrigerant temperature" refers to the temperature of the
refrigerant flowing inside the outdoor heat exchanger 3.
[0025] A controller 80 controls the outdoor side motor to control
the rotation speed of the outdoor side fan 31, and controls the
indoor side motor to control the rotation speed of the indoor side
fan 51. The controller 80 controls the outdoor side motor by
changing voltage and current input to the outdoor side motor. The
control of the rotation speed of the outdoor side fan 31 by the
controller 80 allows control of the volume of air passing through
the outdoor heat exchanger 3.
[0026] A rotation speed detection unit configured to detect the
rotation speed of the outdoor side fan 31 may be provided to detect
the current rotation speed of the outdoor side fan 31.
Alternatively, the current rotation speed of the outdoor side fan
31 may be estimated from information on current applied to the
outdoor side motor and voltage applied to the outdoor side motor.
In the following description, a "fan input" refers to a physical
value related to electric power supplied to the outdoor side fan 31
(the outdoor side motor configured to rotate the outdoor side fan
31).
[0027] The controller 80 controls the indoor side motor so that the
outdoor side fan 31 rotates, for example, when the air-conditioning
apparatus 100 starts operating. The controller 80 is, for example,
hardware such as a circuit device or software executed on an
arithmetic device such as a microcomputer or a CPU, which are
configured to achieve this functionality.
[0028] The cooling operation is executed when the controller 80
switches the four-way valve 2 to cooling. The heating operation is
executed when the controller 80 switches the four-way valve 2 to
heating. In the following description, a "defrosting operation"
refers to an operation executed when the controller 80 switches the
four-way valve 2 to cooling and stops the outdoor side fan 31. The
heating operation corresponds to a "first operation" of the present
invention, and the defrosting operation corresponds to a "second
operation" of the present invention.
[0029] The following first describes, with reference to FIG. 1, the
flow of the refrigerant when the air-conditioning apparatus 100 of
the present invention executes the cooling operation. The
refrigerant discharged from the compressor 1 flows into the outdoor
heat exchanger 3. Having flowed into the outdoor heat exchanger 3,
the refrigerant exchanges heat with the air supplied to the outdoor
heat exchanger 3 through rotation of the outdoor side fan, and then
flows out of the outdoor heat exchanger 3. Having flowed out of the
outdoor heat exchanger 3, the refrigerant flows in the expansion
valve 4 and is depressurized therein, and then flows out of the
expansion valve 4 before flowing into the indoor heat exchanger 5.
Having flowed into the indoor heat exchanger 5, the refrigerant
exchanges heat with the air supplied to the indoor heat exchanger 5
through rotation of the indoor side fan, and then flows out of the
indoor heat exchanger 5. Having flowed out of the indoor heat
exchanger 5, the refrigerant flows into the compressor 1.
[0030] The following describes, with reference to FIG. 1, the flow
of the refrigerant when the air-conditioning apparatus 100 of the
present invention executes the heating operation. The refrigerant
discharged from the compressor 1 flows into the indoor heat
exchanger 5. Having flowed into the indoor heat exchanger 5, the
refrigerant exchanges heat with the air supplied to the indoor heat
exchanger 5 through rotation of the indoor side fan, and then flows
out of the indoor heat exchanger 5. Having flowed out of the indoor
heat exchanger 5, the refrigerant flows in the expansion valve 4
and is depressurized therein, and then flows out of the expansion
valve 4 before flowing into the outdoor heat exchanger 3. Having
flowed into the outdoor heat exchanger 3, the refrigerant exchanges
heat with the air supplied to the outdoor heat exchanger 3 through
rotation of the outdoor side fan, and then flows out of the outdoor
heat exchanger 3. Having flowed out of the outdoor heat exchanger
3, the refrigerant flows into the compressor 1.
[0031] FIG. 2 is a diagram illustrating change in a frosting amount
and total electric power with elapsed time in the air-conditioning
apparatus 100 according to Embodiment 1 of the present invention.
FIG. 3 is a diagram illustrating change in the frosting amount and
total current value with elapsed time in the air-conditioning
apparatus 100 according to Embodiment 1 of the present
invention.
[0032] In FIG. 2, the horizontal axis represents elapsed time
[min], and the vertical axis represents the frosting amount [g] and
a total electric power amount [W]. In FIG. 2, a solid line
indicates the frosting amount, and a dashed line indicates the
total electric power. As illustrated in FIG. 2, the frosting amount
increases as time elapses, and the total electric power increases
as time elapses.
[0033] In FIG. 3, the horizontal axis represents elapsed time
[min], and the vertical axis represents the frosting amount [g] and
a total current value [A]. In FIG. 3, a solid line indicates the
frosting amount, and a dashed line indicates the total current
value. As illustrated in FIG. 3, the frosting amount increases as
time elapses, and the total current value increases as time
elapses.
[0034] FIG. 4 is a diagram illustrating change in an electric power
amount with elapsed time in the air-conditioning apparatus 100
according to Embodiment 1 of the present invention. FIG. 5 is a
diagram illustrating change in the total electric power amount with
elapsed time in the air-conditioning apparatus 100 according to
Embodiment 1 of the present invention. FIGS. 4 and 5 illustrate a
case in which the fan input is the electric power amount, which is
the product of current value applied to an outdoor fan motor and
voltage value applied to the outdoor fan motor. Processing
illustrated in FIGS. 4 and 5 is performed at the heating
operation.
[0035] First, as illustrated in FIG. 4, the controller 80 detects
the fan input and calculates the amount of change in the fan input
at each elapse of a predetermined time. Specifically, for example,
when the fan input at time (t-1) is represented by W(t-1) and the
fan input at time t is represented by W(t), the controller 80
calculates .DELTA.W(t) as the difference between the fan inputs
through Expression (1.1) below.
.DELTA.W(t)=W(t)-W(t-1) (1.1)
[0036] Subsequently, as illustrated in FIG. 5, the controller 80
calculates .DELTA.Wtotal by summing .DELTA.W(t) according to
Expression (1.2) below.
.DELTA.Wtotal=.SIGMA..DELTA.W(t) (1.2)
[0037] Then, the controller 80 determines whether .DELTA.Wtotal is
equal to or larger than a threshold .alpha. as in Expression (1.3)
below. When having determined that .DELTA.Wtotal is equal to or
larger than the threshold .alpha., the controller 80 controls the
four-way valve 2 to start the defrosting operation. When having
determined that .DELTA.Wtotal is smaller than the threshold
.alpha., the controller 80 continues the heating operation.
.DELTA.Wtotal.gtoreq..alpha. (1.3)
[0038] The threshold .alpha. varies with the refrigerant
temperature. Specifically, for example, it is assumed that the
density of frost on the outdoor heat exchanger 3 is larger at
.alpha. higher refrigerant temperature, and thus the controller 80
decreases the value of a accordingly. When the value of .alpha. is
decreased in this manner, .DELTA.Wtotal becomes equal to or larger
than .alpha. at earlier timing and the defrosting operation is
started earlier. For example, it is assumed that the density of
frost on the outdoor heat exchanger 3 is smaller at a lower
refrigerant temperature, and thus the controller 80 increases the
value of .alpha. accordingly. When the value of .alpha. is
increased in this manner, .DELTA.Wtotal becomes equal to or larger
than .alpha. at later timing and start of the defrosting operation
is delayed. In the above description, the fan input is the electric
power, but the present invention is not limited thereto. For
example, the fan input may be the current value applied to the
outdoor fan motor or the voltage value applied to the outdoor fan
motor.
[0039] FIG. 6 is a schematic view illustrating a state in which
frost exists on the outdoor heat exchanger 3 of the
air-conditioning apparatus 100 according to Embodiment 1 of the
present invention. As illustrated in FIG. 6, the frost on the
outdoor heat exchanger 3 has a height Hf_total [mm], and adjacent
fins 3b are apart from each other by a distance Fp [mm]. It is
assumed that wind blows from one end of each fin 3b in the
longitudinal direction thereof to the other end. Since frost exists
on the outdoor heat exchanger 3 as illustrated in FIG. 6, a wind
speed ua decreases, and thus heat exchange at the outdoor heat
exchanger 3 is hindered as compared to a case in which no frost
exists on the outdoor heat exchanger 3.
[0040] In the heating operation, frost exists on a heat transfer
tube 3a and the fins 3b included in the outdoor heat exchanger 3.
As the frost grows, draft resistance increases and input of the
outdoor side fan 31 increases. The frost has a lower density as the
heat transfer tube 3a and the fins 3b have lower temperatures. In
other words, the frost density is smaller at a lower refrigerant
temperature.
[0041] Thus, when the fins 3b is blocked, the amount of frost on
the outdoor heat exchanger 3 differs for different frost densities.
In other words, the defrosting operation needs different defrosting
heat amounts for an identical blockage state of the outdoor heat
exchanger 3 and an identical amount of increase in the fan input.
Specifically, at a higher refrigerant temperature, a larger amount
of heat is needed to melt frost on the outdoor heat exchanger
3.
[0042] FIG. 7 is a diagram illustrating a relation between a
relative humidity .phi. and a frost density .rho. in the
air-conditioning apparatus 100 according to Embodiment 1 of the
present invention. In FIG. 7, the horizontal axis represents the
relative humidity .phi. [%], and the vertical axis represents the
frost density .rho. [kg/m.sup.3]. FIG. 7 illustrates cases with the
refrigerant temperature Ts [degrees C.] at -30 degrees C. and -20
degrees C.
[0043] As illustrated in FIG. 7, the frost density .rho. decreases
as the relative humidity .phi. increases. The frost density .rho.
is larger when the refrigerant temperature Ts is -20 degrees C.
than when the refrigerant temperature Ts is -30 degrees C. In other
words, the frost density .rho. increases as the refrigerant
temperature Ts increases. A defrosting duration increases as the
frost density .rho. increases, and a larger defrosting capacity is
needed as the frost density .rho. increases. Thus, the defrosting
duration increases as the refrigerant temperature Ts increases.
[0044] FIG. 8 is a diagram illustrating a relation between the
refrigerant temperature and a necessary defrosting heat amount in
the air-conditioning apparatus 100 according to Embodiment 1 of the
present invention. As illustrated in FIG. 8, the necessary
defrosting heat amount is proportional to the temperature of the
refrigerant flowing through the refrigerant circuit 90 inside the
outdoor heat exchanger 3.
[0045] As illustrated in FIG. 8, the defrosting duration increases
as the refrigerant temperature Ts increases. Specifically, for
example, a minimum defrosting duration is one minute when an
average refrigerant temperature is -40 degrees C. to -30 degrees C.
For example, the minimum defrosting duration is three minutes when
the average refrigerant temperature is -10 degrees C. to -5 degrees
C. For example, the minimum defrosting duration is five minutes
when the average refrigerant temperature is -5 degrees C. to 0
degrees C.
[0046] Although FIG. 8 illustrates, for sake of simplicity of
description, the proportional relation between the necessary
defrosting heat amount and the refrigerant temperature Ts, the
present invention is not limited to such a relation. The amount of
increase in the necessary defrosting heat amount for increase in
the refrigerant temperature Ts does not need to be constant.
[0047] FIG. 9 is a diagram illustrating change in the frequency of
the compressor 1 with elapsed time in the air-conditioning
apparatus 100 according to Embodiment 1 of the present invention.
FIG. 10 is a diagram illustrating change in the frequency of the
compressor 1 with elapsed time in the air-conditioning apparatus
100 according to Embodiment 1 of the present invention.
[0048] In FIGS. 9 and 10, the horizontal axis represents elapsed
time, and the vertical axis represents the frequency of the
compressor 1. In FIGS. 9 and 10, a solid line indicates change in
the frequency of the compressor 1 when the refrigerant temperature
is relatively high, and a dashed line indicates change in the
frequency of the compressor 1 when the refrigerant temperature is
relatively low.
[0049] The defrosting operation can be performed in a shorter time
at a relatively low refrigerant temperature than at a relatively
high refrigerant temperature. However, efficient execution of the
defrosting operation requires a time for melting frost on the
outdoor heat exchanger 3 and a time for allowing melted frost to
drop from the outdoor heat exchanger 3. Thus, melted frost
potentially freezes again when the duration of the defrosting
operation at a relatively low refrigerant temperature is shorter
than the duration of the defrosting operation at a relatively high
refrigerant temperature. For this reason, in Embodiment 1, the
operation is performed with identical defrosting durations at a
relatively low refrigerant temperature and a relatively high
refrigerant temperature and with a low frequency of the compressor
1, which will be described below.
[0050] The following describes, with reference to FIG. 9, an
example in which the frequency of the compressor 1 is changed based
on the refrigerant temperature in the defrosting operation. In FIG.
9, Interval (a) refers to an interval in which the heating
operation is executed, Interval (b) refers to an interval in which
the defrosting operation is executed, and Interval (c) refers to an
interval in which the heating operation is executed after the
defrosting operation.
[0051] As illustrated in FIG. 9, in Interval (a), the controller 80
controls the compressor 1 so that the compressor 1 has a
predetermined frequency while the four-way valve 2 is switched to
heating. After the compressor 1 is operated at the predetermined
frequency for a predetermined time, the controller 80 controls the
compressor 1 to decrease the frequency thereof. Then, when the
frequency of the compressor 1 becomes zero (t11), the controller 80
switches the four-way valve 2 to cooling and starts the defrosting
operation.
[0052] As illustrated in FIG. 9, in Interval (b), when the
refrigerant temperature is relatively high, the controller 80
controls the compressor 1 so that the compressor 1 has a
predetermined frequency fmax while the four-way valve 2 is switched
to cooling. After the compressor 1 is operated at the predetermined
frequency fmax for a predetermined time, the controller 80 controls
the compressor 1 to decrease the frequency of the compressor 1.
Then, when the frequency of the compressor 1 becomes zero (time
t14), the controller 80 switches the four-way valve 2 to heating
again and starts the heating operation.
[0053] As illustrated in FIG. 9, in Interval (b), when the
refrigerant temperature is relatively low, the controller 80
controls the compressor 1 so that the compressor 1 has the
predetermined frequency fmax while the four-way valve 2 is switched
to cooling. After the compressor 1 is operated at the predetermined
frequency fmax for a predetermined time (time t12), the controller
80 controls the compressor 1 to decrease the frequency thereof so
that the compressor 1 has a predetermined frequency f1. After the
frequency of the compressor 1 is decreased to the predetermined
frequency f1 (time t13), the controller 80 operates the compressor
1 at the predetermined frequency f1 for a predetermined time. After
the compressor 1 is operated at the predetermined frequency f1 for
the predetermined time (time t13), the controller 80 controls the
compressor 1 to decrease the frequency of the compressor 1. Then,
when the frequency of the compressor 1 becomes zero (time t14), the
controller 80 switches the four-way valve 2 to heating again and
starts the heating operation.
[0054] As illustrated in FIG. 9, in Interval (c), the controller 80
controls the compressor 1 so that the frequency thereof has a
predetermined frequency while the four-way valve 2 is switched to
heating.
[0055] The following describes, with reference to FIG. 10, an
example in which the frequency of the compressor 1 is changed based
on the refrigerant temperature in the defrosting operation. In FIG.
10, Interval (a) refers to an interval in which the heating
operation is executed, Interval (b) refers to an interval in which
the defrosting operation is executed, and Interval (c) refers to an
interval in which the heating operation is executed after the
defrosting operation. In FIG. 10, change in the frequency of the
compressor 1 as time elapses in Interval (a) and Interval (c) is
identical to that in FIG. 9, and thus description thereof will be
omitted.
[0056] As illustrated in FIG. 10, in Interval (b), when the
refrigerant temperature is relatively high, the controller 80
controls the compressor 1 so that the compressor 1 has the
predetermined frequency fmax while the four-way valve 2 is switched
to cooling. After the compressor 1 is operated at the predetermined
frequency fmax for a predetermined time, the controller 80 controls
the compressor 1 to decrease the frequency of the compressor 1.
Then, when the frequency of the compressor 1 becomes zero (time
t24), the controller 80 switches the four-way valve 2 to heating
again and starts the heating operation.
[0057] As illustrated in FIG. 10, in Interval (b), when the
refrigerant temperature is relatively low, the controller 80
controls the compressor 1 so that the compressor 1 has a
predetermined frequency f2 while the four-way valve 2 is switched
to cooling. After the compressor 1 acquires the predetermined
frequency f2 (time t22) and has operated for a predetermined time
(time t23), the controller 80 controls the compressor 1 to decrease
the frequency of the compressor 1. Then, when the frequency of the
compressor 1 becomes zero (time t24), the controller 80 switches
the four-way valve 2 to heating again and starts the heating
operation.
[0058] As described above, in the air-conditioning apparatus 100
according to Embodiment 1, the compressor 1, the outdoor heat
exchanger 3, the indoor heat exchanger 5, and the four-way valve 2
provided closer to the discharge side of the compressor 1 than the
outdoor heat exchanger 3 and provided closer to the discharge side
of the compressor 1 than the indoor heat exchanger 5 are connected
with each other. The air-conditioning apparatus 100 includes the
fan 31 configured to deliver air toward the outdoor heat exchanger
3, the power unit configured to supply electric power to the fan
31, a fan input detector configured to detect a physical value
related to the electric power supplied to the fan 31, and the
controller 80 configured to control the four-way valve 2 to switch
between the first operation in which the outdoor heat exchanger 3
functions as an evaporator and the second operation in which the
outdoor heat exchanger 3 functions as a condenser. The first
operation is switched to the second operation when the physical
value detected by the fan input detector is equal to or larger than
a reference value. The controller 80 adjusts the reference value so
that the reference value when the refrigerant flowing through the
outdoor heat exchanger 3 has a high temperature is smaller than the
reference value when the refrigerant has a low temperature. With
this configuration, the defrosting operation can be started at
appropriate timing when the heating operation is performed.
Accordingly, the defrosting operation can be performed more
efficiently than conventionally practiced.
[0059] In the air-conditioning apparatus 100 according to
Embodiment 1, the compressor 1, the outdoor heat exchanger 3, the
indoor heat exchanger 5, and the four-way valve 2 provided closer
to the discharge side of the compressor 1 than the outdoor heat
exchanger 3 and provided closer to the discharge side of the
compressor 1 than the indoor heat exchanger 5 are connected with
each other. The air-conditioning apparatus 100 includes the fan 31
configured to deliver air toward the outdoor heat exchanger 3, the
power unit configured to supply electric power to the fan 31, the
fan input detector configured to detect a physical value related to
the electric power supplied to the fan 31, and the controller 80
configured to control the four-way valve 2 to switch between the
first operation in which the outdoor heat exchanger 3 functions as
an evaporator and the second operation in which the outdoor heat
exchanger 3 functions as a condenser. The first operation is
switched to the second operation when the physical value detected
by the fan input detector is equal to or larger than a reference
value. The controller 80 controls the frequency of the compressor 1
so that the frequency of the compressor 1 when the refrigerant
flowing through the outdoor heat exchanger 3 has a high temperature
is higher than the frequency of the compressor 1 when the
refrigerant has a low temperature. With this configuration, the
defrosting operation can be performed in accordance with the
frosting amount more appropriately than conventionally practiced.
Accordingly, the defrosting operation can be performed more
efficiently than conventionally practiced.
Embodiment 2
[0060] In Embodiment 2, unlike Embodiment 1, the timing of
execution of the defrosting operation is determined based on a
frosting amount Mf, and the frequency of the compressor 1 in the
defrosting operation is determined based on the frosting amount Mf.
In Embodiment 2, any characteristic is same as that of Embodiment 1
unless otherwise stated, and any identical function and
configuration will be described by using identical reference
signs.
[0061] The frosting amount mf(t) is given based on a surface area
A0 [m.sup.2], the frost density .rho.f [kg/m.sup.3], and a frost
height Hf(t) through Expression (2.1) below.
mf(t)=A0.times..rho.f(t).times.Hf(t) (2.1)
[0062] Expression (2.1) below assumes that frost uniformly exists
on the outdoor heat exchanger 3. The surface area A0 [m.sup.2] is a
heat exchange surface area of the outdoor heat exchanger 3. The
frost density .rho.f [kg/m.sup.3] is the density of frost on the
outdoor heat exchanger 3, which is affected by a cooling surface
temperature and a relative humidity. The frost height Hf(t) is the
height of frost on the outdoor heat exchanger 3.
[0063] The frosting amount Mf is given based on the frosting amount
mf(t) through Expression (2.2) below.
Mf=.SIGMA.m(t) (2.2)
[0064] A defrosting heat amount Qf [kJ] is given based on the
frosting amount Mf [kg] and a latent heat .DELTA.H [kJ/kg] through
Expression (2.3) below.
Qf=Mf.times..DELTA.H (2.3)
[0065] A defrosting duration Tf [sec] is given based on the
defrosting heat amount Qf [kJ] and a defrosting capacity P [kW]
through Expression (2.4) below.
Tf=Qf/P (2.4)
[0066] As described above, the controller 80 of the
air-conditioning apparatus 100 according to Embodiment 2 determines
the defrosting duration in accordance with the frosting amount.
Accordingly, the defrosting operation can be performed more
efficiently than conventionally practiced.
[0067] The outdoor side fan 31 corresponds to a "fan" of the
present invention.
REFERENCE SIGNS LIST
[0068] 1 compressor 2 four-way valve 3 outdoor heat exchanger 3a
heat transfer tube 3b fin 4 expansion valve 5 indoor heat exchanger
31 outdoor side fan 32 outdoor side refrigerant temperature sensor
51 indoor side fan 52 indoor side refrigerant temperature sensor 80
controller 90 refrigerant circuit 100 air-conditioning apparatus A0
surface area f1, f2, fmax predetermined frequency Hf frost height
Mf frosting amount mf frosting amount P defrosting capacity Qf
defrosting heat amount t11, t12, t13, t14, t21, t22, t23, t24 time
Tf the defrosting duration Ts surface temperature ua wind speed
.DELTA.H latent heat .alpha. threshold .rho. frost density .rho.f
frost density .phi. relative humidity
* * * * *