BACKGROUND
1. Technical Field
[0001] The present invention relates to a heat pump water heater.
2. Description of the Related Art
[0002] For example, Chinese Examined Utility Model Application Publication No.
201547955 proposes a conventional heat pump water heater that includes a refrigerant circuit
including a compressor for compressing a refrigerant, a four-way valve for diverting
flow of the refrigerant, a radiator, a decompressor for decompressing the refrigerant,
and an evaporator; a tank for storing water heated by the radiator; and a controller.
In the conventional heat pump water heater noted above, the radiator is located on
the periphery of the tank, and the refrigerant circuit is configured such that, when
heating operation to heat water in the tank is performed, the refrigerant flows in
sequence through the compressor, the four-way valve, the radiator, the decompressor,
the evaporator and the four-way valve.
[0003] In the above prior art, the refrigerant circuit is often configured such that, when
defrost operation to melt the frost on the evaporator is performed, the refrigerant
flows in sequence through the compressor, the four-way valve, the evaporator, the
decompressor, the radiator and the four-way valve. However, details of the technical
specifications are not known.
[0004] Additionally, as the temperature of the tank for storing the hot water increases
during the heating operation, the amount of heat dissipation from the radiator is
reduced. Thus, the refrigerant in the refrigerant circuit from the outlet of the radiator
to the suction side of the compressor through the decompressor, the evaporator and
the four-way valve contains more liquid refrigerant in a gas-liquid two-phase state.
[0005] When the defrost operation is performed in the gas-liquid two-phase state where more
liquid refrigerant is present, the pressures of a high-pressure refrigerant and a
low-pressure refrigerant are equalized by switching the four-way valve, so that the
liquid refrigerant may be sucked into the compressor. This results in the possibility
that the durability of the compressor may be reduced.
[0006] British Patent Application No.
2497171, forming the closest prior art, discloses a building hot water system having a heat
pump and a hot water tank according to the preamble of claim 1.
SUMMARY
[0007] The present invention, which solves the problems in the prior art described above,
is directed to a heat pump water heater that performs defrost operation with improved
durability of a compressor.
[0008] In order to solve the problems in the prior art described above, a heat pump water
heater as defined in claim 1 includes, amongst others, a refrigerant circuit including
a compressor for compressing a refrigerant, a four-way valve for diverting flow of
the refrigerant, a radiator, a decompressor for decompressing the refrigerant, and
an evaporator; a tank for storing water heated by the radiator; and a controller.
When heating operation to heat the water in the tank is performed, the refrigerant
circuit is configured such that the refrigerant flows in sequence through the compressor,
the four-way valve, the radiator, the decompressor, the evaporator, and the four-way
valve. The radiator is wound around a periphery of the tank. The heat pump water further
comprises a tank temperature sensor for detecting a temperature of hot water in the
tank. When defrost operation to melt frost on the evaporator is performed, the controller
selects and performs either a first defrost operation where the refrigerant circuit
is configured such that the refrigerant flows in sequence through the compressor,
the four-way valve, the evaporator, the decompressor, the radiator and the four-way
valve or a second defrost operation where the refrigerant circuit is configured such
that the refrigerant flows in sequence through the compressor, the four-way valve,
the radiator, the decompressor, the evaporator and the four-way valve, the controller
selects and performs the first defrost operation when the temperature of the tank
is less than or equal to a predetermined value, the controller selects and performs
the second defrost operation when the temperature of the tank is greater than a predetermined
value.
[0009] Thus, either the first defrost operation or second defrost operation is selected
based on the state of the refrigerant in the refrigerant circuit from the outlet of
the radiator to the suction side of the compressor through the decompressor, the evaporator
and the four-way valve during the heating operation. Accordingly, the heat pump water
heater that performs defrost operation with improved durability of the compressor
can be provided.
[0010] The present invention can provide a heat pump water heater that performs defrost
operation with improved durability of a compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
FIG. 1 is a schematic diagram of a heat pump water heater according to a first exemplary
embodiment of the present invention;
FIG. 2 is a control flow diagram for switching defrost operation of the heat pump
water heater;
FIG. 3 illustrates a refrigerant circuit during a first defrost operation of the heat
pump water heater; and
FIG. 4 illustrates a refrigerant circuit during a second defrost operation of the
heat pump water heater.
DETAILED DESCRIPTION
[0012] A heat pump water heater as defined in claim 1 and according to a first aspect of
the present invention includes, amongst others, a refrigerant circuit including a
compressor for compressing a refrigerant, a four-way valve for diverting flow of the
refrigerant, a radiator, a decompressor for decompressing the refrigerant, and an
evaporator; a tank for storing water heated by the radiator; and a controller. The
radiator is located on a periphery of the tank. When heating operation to heat the
water in the tank is performed, the refrigerant circuit is configured such that the
refrigerant flows in sequence through the compressor, the four-way valve, the radiator,
the decompressor, the evaporator, and the four-way valve. When defrost operation to
melt frost on the evaporator is performed, the controller selects and performs either
a first defrost operation where the refrigerant circuit is configured such that the
refrigerant flows in sequence through the compressor, the four-way valve, the evaporator,
the decompressor, the radiator and the four-way valve or a second defrost operation
where the refrigerant circuit is configured such that the refrigerant flows in sequence
through the compressor, the four-way valve, the radiator, the decompressor, the evaporator
and the four-way valve.
[0013] Thus, either the first defrost operation or second defrost operation is selected
based on the state of the refrigerant in the refrigerant circuit from the outlet of
the radiator to the suction side of the compressor through the decompressor, the evaporator
and the four-way valve during the heating operation. Accordingly, the heat pump water
heater that performs defrost operation with improved durability of the compressor
can be provided.
[0014] In the first aspect of the present invention, a second aspect of the present invention
further includes a tank temperature sensor for detecting a temperature of hot water
in the tank, and the controller selects and performs the first defrost operation when
the temperature of the tank is less than or equal to a predetermined value.
[0015] Thus, when the refrigerant in the refrigerant circuit from the outlet of the radiator
to the suction side of the compressor through the decompressor, the evaporator and
the four-way valve during the heating operation contains relatively less liquid refrigerant
in a gas-liquid two-phase state, that is, the temperature of the tank is not relatively
increased, a high-temperature refrigerant discharged from the compressor flows directly
into the evaporator through the four-way valve during the defrost operation. As such,
suction of the liquid refrigerant into the compressor can be prevented and the high-temperature
refrigerant discharged from the compressor can flow into the evaporator without heat
dissipation, so that frost can be removed. Accordingly, the heat pump water heater
can be provided that performs defrost operation with improved durability of the compressor.
[0016] In the first aspect of the present invention, a third aspect of the present invention
further includes a tank temperature sensor for detecting a temperature of hot water
in the tank, and the controller selects and performs the second defrost operation
when the temperature of the tank is greater than a predetermined value.
[0017] Suction of the liquid refrigerant into the compressor can be prevented even when
the defrost operation is performed in a state where the refrigerant in the refrigerant
circuit from the outlet of the radiator to the suction side of the compressor through
the decompressor, the evaporator and the four-way valve during the heating operation
contains more liquid refrigerant in a gas-liquid two-phase state, that is, where the
temperature of the tank is increased. Thus, the heat pump water heater can be provided
that performs defrost operation with improved durability of the compressor.
[0018] In the second or third aspect of the present invention, a fourth aspect of the present
disclosure further includes an ambient temperature sensor for detecting an ambient
temperature. The predetermined value to select whether the controller performs the
first defrost operation or the second defrost operation is less at low ambient temperature
than at high ambient temperature.
[0019] Thus, when ambient temperature is low, that is, when the refrigerant in the refrigerant
circuit from the outlet of the radiator to the suction side of the compressor through
the decompressor, the evaporator and the four-way valve during the heating operation
contains more liquid refrigerant, the temperature of the tank to determine whether
the first defrost operation or the second defrost operation is performed is reduced,
so that the suction of the liquid refrigerant into the compressor can be further prevented
even when the defrost operation is performed. Accordingly, the heat pump water heater
that performs defrost operation with improved durability of the compressor can be
provided.
[0020] In the second or third aspect of the present invention, a fifth aspect of the present
invention further includes an ambient temperature sensor for detecting an ambient
temperature. An operating frequency of the compressor is greater at low ambient temperature
than at high ambient temperature.
[0021] Thus, the circulating volume of the refrigerant discharged from the compressor can
be increased when the ambient temperature is low. This accelerates the defrosting
effect and reduces the defrost operation time.
[0022] Exemplary embodiments according to the present invention will now be described with
reference to the drawings. These exemplary embodiments do not limit the scope of the
present invention.
(First exemplary embodiment)
[0023] FIG. 1 is a schematic diagram of a heat pump water heater according to the present
exemplary embodiment. As illustrated in FIG. 1, a heat pump water heater includes
water storage tank unit 80 and heat pump apparatus 90.
[0024] Water storage tank unit 80 incorporates tank 3 for storing water. A water supply
pipe (not shown), into which water is delivered through a water supply pipe or the
like, is connected to the lower portion of tank 3.
[0025] A hot water supply pipe (not shown) for supplying hot water in tank 3 is connected
to the upper portion of tank 3.
[0026] As the hot water in tank 3 is supplied for use and decreases, water is automatically
supplied to tank 3 through the water supply pipe.
[0027] Tank 3 is provided with a first temperature sensor (i.e., tank temperature sensor
7) for detecting the temperature of the hot water in tank 3 (i.e., hot water storage
temperature). In the present exemplary embodiment, tank temperature sensor 7 is configured
to have a plurality of sensors arranged vertically of tank 3.
[0028] A refrigerant pipe, which is radiator 4 for heating water in tank 3, is wound around
the periphery of tank 3.
[0029] Heat exchange is performed between a high-temperature refrigerant discharged from
compressor 1 and the water in tank 3, and thus hot water at high temperature is produced.
It is configured such that the high-temperature refrigerant flows around the periphery
of tank 3 from bottom to top during heating operation described below.
[0030] Heat pump apparatus 90 includes a refrigerant circuit where compressor 1 for compressing
a refrigerant, four-way valve 2, an expansion device being decompressor 5 for decompressing
the refrigerant, and evaporator 6 for evaporating the refrigerant are annularly connected
by refrigerant piping.
[0031] Decompressor 5 may be an electromagnetic expansion valve capable of controlling the
degree of opening or a capillary tube.
[0032] Evaporator 6 is an air heat exchanger for heat exchange between air blown by a blower
fan (not shown) installed near evaporator 6 and the refrigerant. The refrigerant circulating
through the refrigerant circuit includes a Freon (registered trademark) refrigerant,
such as R410A, R134a, R22, R32, etc., and other refrigerants. The heat pump apparatus
is located outdoors.
[0033] Heat pump apparatus 90 incorporates a second temperature sensor (i.e., ambient temperature
sensor 9), located near evaporator 6, for detecting an ambient temperature. Heat pump
apparatus 90 also incorporates a third temperature sensor (i.e., evaporator temperature
sensor 8) for detecting the temperature of evaporator 6 or of refrigerant piping in
the vicinity of and connected to evaporator 6.
[0034] Temperature output signals detected by the temperature sensors are transmitted to
controller 10. Controller 10 performs a number of operations. The operations include
heating operation for heating the water in tank 3 using radiator 4. The operations
also include defrost operation in which, when the evaporator 6 frosts, the frost is
melted and removed.
[0035] Controller 10 runs and stops the operations based on operating means (not shown)
and the temperatures detected by the temperature sensors. Controller 10 also controls
the motions and operations of compressor 1 and decompressor 5 based on the temperatures
detected by the temperature sensors.
[0036] The operating means (not shown) has a function for a user to indicate run and stop
of the heating operation and a function to set a temperature (setting temperature)
of hot water to be stored in tank 3.
[0037] The controller controls heat pump apparatus 90 so that the temperature of the water
in tank 3 heated by radiator 4 reaches a setting temperature during the heating operation.
[0038] The heating operation of the heat pump water heater according to the present exemplary
embodiment is described below. In heat pump apparatus 90, the refrigerant flows in
the direction of the arrows shown in FIG. 1.
[0039] In heat pump apparatus 90, a high temperature and high pressure refrigerant compressed
by and discharged from compressor 1 flows through four-way valve 2, flows into radiator
4, flows around the periphery of tank 3 from bottom to top, and heats the water in
tank 3. Thus, hot water at high temperature is produced.
[0040] The refrigerant flowing out from radiator 4 is decompressed by decompressor 5, transitions
to a low temperature and low pressure state, and flows into evaporator 6. The refrigerant
flowing into evaporator 6 absorbs heat from the air blown by the blower fan (not shown)
and evaporates. Then, the refrigerant flows into compressor 1 and is compressed again.
Such a process is repeated and the refrigerant circulates through the refrigerant
circuit.
[0041] Controller 10 controls heat pump apparatus 90 so that the temperature of the refrigerant
discharged from compressor 1 is at a predetermined temperature.
[0042] The heating operation starts when controller 10 detects that the temperature of tank
temperature sensor 7 falls below a predetermined temperature (i.e., heating start
temperature). The heating operation can be stopped when it is detected that the temperature
of tank temperature sensor 7 reaches or exceeds a predetermined temperature (i.e.,
heating stop temperature).
[0043] In this case, preferably, the heating operation starts when the temperature of tank
temperature sensor 7 located relatively upward falls below the heating start temperature,
and the heating operation is stopped when the temperature of tank temperature sensor
7 located relatively downward reaches or exceeds the heating stop temperature.
[0044] The defrost operation of the heat pump water heater according to the present exemplary
embodiment is then described below.
[0045] FIG. 2 is a control flow diagram for switching the defrost operation. FIG. 3 illustrates
a refrigerant circuit during a first defrost operation, and FIG. 4 illustrates a refrigerant
circuit during a second defrost operation. In heat pump apparatus 90, the refrigerant
flows in the direction of the arrows shown in FIGS. 3 and 4.
[0046] If the heating operation is performed under the operating condition at a low ambient
temperature, moisture around evaporator 6 through which a low temperature and low
pressure refrigerant flows is cooled, and the surface of evaporator 6 may be frosted.
When controller 10 determines the frosting condition on evaporator 6 based on the
fact that the temperature of evaporator temperature sensor 8 is less than or equal
to a predetermined temperature, the defrost operation is performed for melting and
removing the frost.
[0047] In FIG. 2, the controller determines, during the heating operation, whether the defrost
operation is possible or not (step S1). If the defrost operation is not needed ("NO"
at step S1), the heating operation is continued. If controller 10 determines that
the defrost operation is needed ("YES" at step S1), controller 10 starts the defrost
operation.
[0048] When the defrost operation is started, the temperature of hot water in tank 3 is
first detected by tank temperature sensor 7. Thus, when the defrost operation is started,
controller 10 determines, based on a reading of tank temperature sensor 7, whether
the refrigerant in the refrigerant circuit from radiator 4 to evaporator 6 contains
more liquid refrigerant in a gas-liquid two-phase state (step S2). If the reading
of tank temperature sensor 7 is less than or equal to a predetermined value ("YES"
at step S2), controller 10 performs the first defrost operation. If the reading of
tank temperature sensor 7 is greater than the predetermined value ("NO" at step S2),
controller 10 performs the second defrost operation. After the defrost operation is
completed, the heating operation is employed.
[0049] Controller 10 changes the predetermined value described above to a lower value when
the ambient temperature detected by ambient temperature sensor 9 is low rather than
high, so that the suction of the liquid refrigerant into the compressor can be prevented
even at a low ambient temperature at which more liquid refrigerant is present.
[0050] For the first defrost operation, the refrigerant circuit is configured such that
the refrigerant flows in sequence through compressor 1, four-way valve 2, evaporator
6, decompressor 5, radiator 4 and four-way valve 2, as illustrated in FIG. 3. This
allows a high-temperature refrigerant discharged from the compressor to flow into
the evaporator without heat dissipation, and thus frost can be removed.
[0051] For the second defrost operation, the refrigerant circuit is configured such that
the refrigerant flows in sequence through compressor 1, four-way valve 2, radiator
4, decompressor 5, evaporator 6 and four-way valve 2, as illustrated in FIG. 4.
[0052] In the first and second defrost operations, controller 10 increases the operating
frequency of compressor 1 when the ambient temperature detected by ambient temperature
sensor 9 is low rather than high, so that the circulating volume of the refrigerant
discharged from compressor 1 is increased when the ambient temperature is low. This
accelerates the defrosting effect and reduces the defrost operation time.
[0053] If evaporator 6 is determined to be frosted based on the temperature of evaporator
temperature sensor 8, controller 10 transmits a signal to perform the defrost operation
and the second defrost operation is started. Thereafter, decompressor 5 is adjusted
so that a low temperature and low pressure refrigerant is changed to a high temperature
and high pressure refrigerant while maintaining the refrigerant circuit comprised
in sequence of compressor 1, four-way valve 2, radiator 4, decompressor 5, evaporator
6, and four-way valve 2.
[0054] This allows the refrigerant flowing into evaporator 6 during the heating operation
to flow into evaporator 6 at a high temperature, and thus frost can be removed. When
making the adjustment using decompressor 5, it is preferable to increase the degree
of opening as much as possible.
[0055] As the water in tank 3 is heated during the heating operation and the water temperature
rises, a state of the refrigerant varies from a state of the gas-liquid two-phase
flow to a state where more liquid refrigerant is present in the refrigerant circuit
incorporating radiator 4, decompressor 5, and evaporator 6.
[0056] When the first defrost operation is performed in the state where more liquid refrigerant
is present, the high pressure refrigerant flows into the low pressure refrigerant
and the pressure is equalized, and thus the liquid refrigerant is sucked into compressor
1.
[0057] Due to the above phenomenon, liquid lock is more likely to occur when compressor
1 operates, and there is a possibility that compressor 1 may be stopped or the durability
of compressor 1 may be reduced.
[0058] Here, when the refrigerant transitions from the state of the gas-liquid two-phase
flow to the state where more liquid refrigerant is present, the liquid refrigerant
can be prevented from being sucked into compressor 1 by performing the second defrost
operation.
[0059] In this manner, the first defrost operation or the second defrost operation is selected
based on the state of the refrigerant in the refrigerant circuit from the outlet of
radiator 4 to the suction side of compressor 1 through decompressor 5, evaporator
6 and four-way valve 2 during the heating operation, that is, on the temperature of
hot water in the tank, so that the heat pump water heater that performs defrost operation
with improved durability of the compressor can be provided.
[0060] As described above, a heat pump water heater according to the present invention,
which performs defrost operation with improved durability of a compressor, is useful
not only for a residential heat pump water heater, but also for a commercial heat
pump water heater or the like.
1. Wärmepumpen-Wassererhitzer, umfassend:
einen Kältemittelkreislauf mit einem Kompressor (1) zum Komprimieren eines Kältemittels,
einem Vierwegeventil (2) zum Umlenken des Kältemittelstroms, einem Heizkörper (4),
einem Dekompressor (5) zum Dekomprimieren des Kältemittels und einem Verdampfer (6);
einen Behälter (3) zum Speichern von durch den Heizkörper (4) erwärmtem Wasser; und
eine Steuervorrichtung (10),
wobei die Steuervorrichtung dafür konfiguriert ist, einen Heizvorgang zum Erwärmen
des Wassers im Tank (3) durchzuführen, wobei der Kältemittelkreislauf so konfiguriert
ist, dass das Kältemittel der Reihe nach durch den Kompressor (1), das Vierwegeventil
(2), den Heizkörper (4), den Dekompressor (5), den Verdampfer (6) und das Vierwegeventil
(2) strömt;
dadurch gekennzeichnet, dass der Heizkörper (4) um einen Umfang des Tanks (3) gewickelt ist,
der Wärmepumpen-Wassererhitzer ferner einen Tanktemperatursensor (7) zum Erfassen
einer Temperatur von heißem Wasser im Tank (3) umfasst,
die Steuervorrichtung (10) dafür konfiguriert ist, entweder einen ersten Abtauvorgang
zum Schmelzen von Reif auf dem Verdampfer (6) auszuwählen und auszuführen, wobei der
Kältemittelkreislauf so konfiguriert ist, dass das Kältemittel der Reihe nach durch
den Verdichter (1), das Vierwegeventil (2), den Verdampfer (6), den Dekompressor (5)
den Heizkörper (4) und das Vierwegeventil (2) strömt, oder einen zweiten Abtauvorgang
zum Schmelzen von Reif auf dem Verdampfer (6), wobei der Kältemittelkreislauf so konfiguriert
ist, dass das Kältemittel nacheinander durch den Kompressor (1), das Vierwegeventil
(2), den Heizkörper (4), den Dekompressor (5), den Verdampfer (6) und das Vierwegeventil
(2) strömt,
die Steuervorrichtung (10) dafür konfiguriert ist, den ersten Abtauvorgang auszuwählen
und auszuführen, wenn die Temperatur des Tanks (3) kleiner oder gleich einem vorbestimmten
Wert ist,
die Steuervorrichtung (10) dafür konfiguriert ist, den zweiten Abtauvorgang auszuwählen
und auszuführen, wenn die Temperatur des Tanks (3) über dem vorbestimmten Wert liegt.
2. Wärmepumpen-Wassererhitzer nach Anspruch 1, ferner einen Umgebungstemperatursensor
(9) zum Erfassen einer Umgebungstemperatur umfassend,
wobei der vorbestimmte Wert zur Auswahl, ob die Steuervorrichtung (10) den ersten
Abtauvorgang oder den zweiten Abtauvorgang ausführt, bei einer niedrigen Umgebungstemperatur
niedriger ist als bei einer hohen Umgebungstemperatur.
3. Wärmepumpen-Wassererhitzer nach Anspruch 1 oder 2, ferner einen Umgebungstemperatursensor
(9) zum Erfassen einer Umgebungstemperatur umfassend,
wobei eine Betriebsfrequenz des Kompressors (1) bei einer niedrigen Umgebungstemperatur
höher ist als bei einer hohen Umgebungstemperatur.
1. Chauffe-eau à pompe à chaleur comprenant :
un circuit de fluide frigorigène comprenant un compresseur (1) pour comprimer un fluide
frigorigène, une vanne à quatre voies (2) pour dévier l'écoulement du fluide frigorigène,
un radiateur (4), un décompresseur (5) pour décompresser le fluide frigorigène et
un évaporateur (6) ;
un réservoir (3) pour stocker l'eau chauffée par le radiateur (4) ; et
un dispositif de commande (10),
le dispositif de commande étant conçu pour effectuer une opération de chauffage pour
chauffer l'eau dans le réservoir (3), le circuit de fluide frigorigène étant conçu
de telle sorte que le fluide frigorigène s'écoule en séquence à travers le compresseur
(1), la vanne à quatre voies (2), le radiateur (4), le décompresseur (5), l'évaporateur
(6) et la vanne à quatre voies (2) ;
caractérisé en ce que le radiateur (4) est enroulé autour d'une périphérie du réservoir (3),
le chauffe-eau à pompe à chaleur comprend en outre un capteur de température de réservoir
(7) pour détecter une température d'eau chaude dans le réservoir (3),
le dispositif de commande (10) est conçu pour sélectionner et effectuer soit une première
opération de dégivrage pour faire fondre le givre sur l'évaporateur (6),
le circuit de fluide frigorigène étant conçu de telle sorte que le fluide frigorigène
s'écoule en séquence à travers le compresseur (1), la vanne à quatre voies (2), l'évaporateur
(6), le décompresseur (5), le radiateur (4) et la vanne à quatre voies (2), soit une
deuxième opération de dégivrage pour faire fondre le givre sur l'évaporateur (6),
le circuit de fluide frigorigène étant conçu de telle sorte que le fluide frigorigène
s'écoule en séquence à travers le compresseur (1), la vanne à quatre voies (2), le
radiateur (4), le décompresseur (5), l'évaporateur (6) et la vanne à quatre voies
(2),
le dispositif de commande (10) est conçu pour sélectionner et effectuer la première
opération de dégivrage lorsque la température du réservoir (3) est inférieure ou égale
à une valeur prédéterminée,
le dispositif de commande (10) est conçu pour sélectionner et effectuer la deuxième
opération de dégivrage lorsque la température du réservoir (3) est supérieure à la
valeur prédéterminée.
2. Chauffe-eau à pompe à chaleur selon la revendication 1, comprenant en outre un capteur
de température ambiante (9) pour détecter une température ambiante,
la valeur prédéterminée pour sélectionner si le dispositif de commande (10) effectue
la première opération de dégivrage ou la deuxième opération de dégivrage étant inférieure
à une température ambiante basse qu'à une température ambiante élevée.
3. Chauffe-eau à pompe à chaleur selon la revendication 1 ou 2, comprenant en outre un
capteur de température ambiante (9) pour détecter une température ambiante,
une fréquence de fonctionnement du compresseur (1) étant supérieure à une température
ambiante basse qu'à une température ambiante élevée.