WO2012043379A1

WO2012043379A1 - Hot water supply system

Info

Publication number: WO2012043379A1
Application number: PCT/JP2011/071617
Authority: WO
Inventors: 峻浅利; 貴宏図司
Original assignee: 東芝キヤリア株式会社
Priority date: 2010-09-29
Filing date: 2011-09-22
Publication date: 2012-04-05
Also published as: JP5690834B2; JPWO2012043379A1

Abstract

A hot-water pipe (H) is piped to a water heat exchanger (3) of a high-temperature side refrigerating cycle (Ra) and water or hot-water is heated to a predetermined temperature. A second expanding device (12) is provided at a midway portion of a bypass circuit (10) having one end connected between the four-way selector valve (7) of a low-temperature side refrigerating cycle (Rb) and an intermediate heat exchanger (4) and the other end connected between a low-temperature side expanding device (9) and an air heat exchanger (8). During the defrosting operation of the air heat exchanger (8), a control unit (S) controls the four-way selector valves (2, 7) of both refrigerating cycles (Ra, Rb) to switch reversely, controls the evaporating temperature or evaporating pressure of the intermediate heat exchanger (4) by the low-temperature side expanding device (9), and, when detecting that an overheat degree of the inlet refrigerant of a low-temperature side compressor (6) has exceeded a predetermined value, controls the second expanding device (12) of the bypass circuit (10) to open. During the defrosting operation of the air heat exchanger (8) of the low-temperature side refrigerating cycle (Rb), an efficient defrosting operation is thereby executed and the high-temperature side compressor and the low-temperature side compressor are reliably protected.

Description

Hot water system

Embodiment of the present invention relates to a hot water supply system that supplies hot water using a two-way refrigeration cycle.

The high temperature side refrigeration cycle and the low temperature side refrigeration cycle are connected via an intermediate heat exchanger, and the intermediate heat exchanger exchanges heat between the refrigerant circulating in the high temperature side refrigeration cycle and the refrigerant circulating in the low temperature side refrigeration cycle. There is a tendency that a binary refrigeration cycle for obtaining a high compression ratio is frequently used (for example, Japanese Unexamined Patent Publication No. 2000-320914).

And, a water heat exchanger is provided as a condenser constituting the high temperature side refrigeration cycle, and water or hot water is led from a hot water pipe connected to a water supply source, a hot water storage tank or a condensate side buffer tank. The temperature of the water or warm water rises by exchanging heat with the refrigerant in the water heat exchanger. A hot water pipe is connected to the hot water storage tank or the condensate side buffer tank, and hot water raised to a predetermined temperature is supplied.

By the way, in this hot water supply system, the air heat exchanger constituting the low temperature side refrigeration cycle is operated as an evaporator during hot water supply operation. Therefore, it is inevitable that the air heat exchanger is frosted especially during operation under the low outside air temperature condition. If it passes in this state, since the heat exchange efficiency of an air heat exchanger will fall, it is necessary to perform a defrost operation.

During defrosting operation, the four-way switching valve of the high-temperature side refrigeration cycle and the four-way switching valve of the low-temperature side refrigeration cycle are switched in reverse to the hot water supply operation to reverse the refrigerant circulation direction. The heat source for defrosting is water or hot water flowing through the water heat exchanger, and the heat source is abundant, and the hot gas is led directly to the air heat exchanger of the low temperature side refrigeration cycle, so air heat exchange efficiently. Defrost the vessel.

However, if the temperature of the hot water circulating in the hot water piping is high for a long time after the hot water supply operation is switched to the defrosting operation, the refrigerant evaporation temperature in the water heat exchanger acting as an evaporator in the high temperature side refrigeration cycle is also high. Thus, the condensation temperature of the high temperature side refrigeration cycle is also increased.
On the other hand, in the low temperature side refrigeration cycle, the condensation temperature during the defrosting operation until the frost melts is about 0 to 10 ° C. The evaporation temperature at that time is 0 ° C. or less, although it depends on the size and opening of the expansion valve.

Therefore, for example, if the water temperature is about 60 ° C., the evaporation temperature of the high temperature side refrigeration cycle is about 50 ° C., and the condensation temperature is about 60 to 70 ° C., which is higher than that. The degree of superheat is about 50-60K. If the degree of superheat is too large, the density of the refrigerant will be reduced, the amount of circulation will not be secured, and the defrosting time will be prolonged.

Compressor with a high pressure in the hermetic container cools the motor windings with the discharge gas, so if the refrigerant density is low, the motor windings cannot be cooled sufficiently, causing a compressor failure due to winding short-circuit. In addition, as the temperature of the gas refrigerant sucked into the low temperature side compressor rises, there is a problem that the refrigeration oil that lubricates the compression mechanism part deteriorates at an early stage.

The present embodiment is based on the above circumstances, and after providing a binary refrigeration cycle, during the defrosting operation for the air heat exchanger of the low temperature side refrigeration cycle, an efficient defrosting operation is performed, Provided is a hot water supply system capable of reliably protecting a low temperature side compressor.

In order to satisfy the above object, the hot water supply system of the present embodiment includes a high temperature side compressor, a four-way switching valve, a water heat exchanger, a high temperature side expansion device, and a high temperature side refrigeration cycle that communicates the intermediate heat exchanger via a refrigerant pipe. A low-temperature side compressor, a four-way switching valve, an intermediate heat exchanger, a low-temperature side expansion device, and a low-temperature side refrigeration cycle that communicates an air heat exchanger via a refrigerant pipe, and a refrigerant that is led to the high-temperature side refrigeration cycle A two-way refrigeration cycle is provided that exchanges heat with the refrigerant guided to the low temperature side refrigeration cycle by an intermediate heat exchanger.

FIG. 1 is a configuration diagram of a refrigeration cycle of a hot water supply system according to the first embodiment. FIG. 2 is a configuration diagram of a refrigeration cycle of the hot water supply system according to the second embodiment. FIG. 3 is a configuration diagram of the refrigeration cycle of the hot water supply system according to the third embodiment. FIG. 4 is a diagram for explaining a second expansion device used in the third embodiment. FIG. 5 is a refrigeration cycle configuration diagram of a hot water supply system according to the fourth embodiment.

FIG. 1 is a configuration diagram of the refrigeration cycle of the hot water supply system according to the first embodiment, and particularly shows a refrigeration cycle switching state during a hot water supply operation.
This hot water supply system includes a high temperature side refrigeration cycle Ra, a hot water pipe H, a low temperature side refrigeration cycle Rb, and a control unit (control means) S.

Explaining from the high temperature side refrigeration cycle Ra, the discharge part a of the high temperature side compressor 1 and the first port d1 of the four-way switching valve 2 are connected via the refrigerant pipe P, and the second port d2 of the four-way switching valve 2 is connected. The primary side flow path 3a of the water heat exchanger 3 is connected to the refrigerant heat through the refrigerant pipe P. The third port d3 of the four-way switching valve 2 is connected to the primary flow path 4a of the intermediate heat exchanger 4 via the refrigerant pipe P.

The fourth port d4 of the four-way switching valve is connected to the suction part b of the high temperature side compressor 1 via the refrigerant pipe P. On the other hand, the primary side flow path 3 a of the water heat exchanger 3 is connected to the primary side flow path 4 a of the intermediate heat exchanger 4 through the refrigerant pipe P provided with the high temperature side expansion device 5.

In the high temperature side refrigeration cycle Ra, during the hot water supply operation, the refrigerant compressed and discharged by the high temperature side compressor 1 is:-four-way switching valve 2-primary side flow path 3a of the water heat exchanger 3-high temperature side expansion device 5 -The primary side flow path 4a of the intermediate heat exchanger 4-the four-way switching valve 2-the high temperature side compressor 1-are introduced in this order.
Therefore, the primary side flow path 3a of the water heat exchanger 3 acts as a condenser, and the primary side flow path 4a of the intermediate heat exchanger 4 acts as an evaporator.

During the defrosting operation to be described later, the four-way switching valve 2 is switched, and the refrigerant compressed and discharged by the high-temperature side compressor 1 is: -four-way switching valve 2-primary side flow path 4a of the intermediate heat exchanger 4-high temperature It is led in the order of side expansion device 5-primary side flow path 3 a of the water heat exchanger 3-four-way switching valve 2-high temperature side compressor 1-.
At this time, the primary side flow path 4a of the intermediate heat exchanger 4 acts as a condenser, and the primary side flow path 3a of the water heat exchanger 3 acts as an evaporator.

In the low temperature side refrigeration cycle Rb, the discharge part a of the low temperature side compressor 6 and the first port d1 of the four-way switching valve 7 are connected via the refrigerant pipe P, and the second port d2 of the four-way switching valve 7 is in the middle. The secondary flow path 4b of the heat exchanger 4 is connected via the refrigerant pipe P. The third port d3 of the four-way switching valve 7 is connected to the air heat exchanger 8 via the refrigerant pipe P.

The fourth port d4 of the four-way switching valve 7 is connected to the suction part b of the low temperature side compressor 6 via the refrigerant pipe P. On the other hand, the secondary flow path 4 b of the intermediate heat exchanger 4 is connected to the air heat exchanger 8 through a refrigerant pipe P provided with a low temperature side expansion device 9. A blower fan F is disposed opposite to the air heat exchanger 8.

In the low temperature side refrigeration cycle Rb, during the hot water supply operation, the refrigerant compressed and discharged by the low temperature side compressor 6 is: -four-way switching valve 7 -secondary side flow path 4b of the intermediate heat exchanger 4 -low temperature side expansion device 9 -Air heat exchanger 8-Four-way switching valve 7-Low temperature side compressor 6-
Therefore, the secondary side flow path 4b of the intermediate heat exchanger 4 acts as a condenser, and the air heat exchanger 8 acts as an evaporator.

During the defrosting operation to be described later, the four-way switching valve 7 is switched, and the refrigerant compressed and discharged by the low-temperature side compressor 6 is: -four-way switching valve 7 -air heat exchanger 8 -low-temperature side expansion device 9 -intermediate heat The secondary flow path 4b of the exchanger 4—the four-way switching valve 7—the low temperature side compressor 6—is led in this order.
At this time, the air heat exchanger 8 acts as a condenser, and the secondary flow path 4b of the intermediate heat exchanger 4 acts as an evaporator.

The bypass circuit 10 is provided in such a low temperature side refrigeration cycle Rb. One end of the bypass circuit 10 is connected to the refrigerant pipe P between the four-way switching valve 7 and the secondary flow path 4 b of the intermediate heat exchanger 4, and the other end is connected to the low-temperature side expansion device 9 and the air heat exchanger 8. The bypass pipe 11 connected to the refrigerant pipe P between and the second expansion device 12 provided in the middle of the bypass pipe 11.

One end of the hot water pipe H is connected to a water supply source, a hot water storage tank or a suction side of a condensate side buffer tank, and the other end is connected to a hot water storage tank, a hot water tap or a condensate side buffer tank (all not shown) Connected to.
In the middle part of the hot water pipe H, a water transport pump 13 and a secondary flow path 3 b that is piped into the water heat exchanger 3 are provided. Therefore, the water or hot water led to the hot water pipe H exchanges heat with the refrigerant led to the primary side flow path 3 a in the secondary side flow path 3 b of the water heat exchanger 3.

The control unit S includes

temperature sensors

15a and 15b and

pressure sensors

17a and 17b provided in the discharge part a of the high temperature side compressor 1 and the low temperature side compressor 6, and

temperature sensors

16a and 16b provided on the suction part b side.

Pressure sensors

18a and 18b, a water temperature sensor 19 which is a water temperature detecting means provided on the inlet side of the secondary flow path 3b of the water heat exchanger 3 in the hot water pipe H, and a water temperature sensor which is a water temperature detecting means provided on the outlet side 20 and a detection signal from the flow rate sensor 21 which is a flow rate detection means are received every predetermined time.

Further, the control unit S receives a detection signal from a temperature sensor (not shown) provided in the intermediate heat exchanger 4 and the air heat exchanger 8, and also receives an instruction signal from a remote controller (remote controller: not shown). The control unit S calculates the detection signals received from these sensors and the remote controller and compares them with a stored reference value.

And the control part S controls the operating frequency of the high temperature side compressor 1 and the low temperature side compressor 6, and, at the time of hot water supply operation, the refrigerant temperature (evaporation temperature) of the heat exchanger and the suction side refrigerant temperature of the compressor From the difference, the degree of superheat of the suction side refrigerant is calculated, and the opening / closing and the amount of restriction of the high temperature side expansion device 5 and the low temperature side expansion device 9 are controlled.

During the defrosting operation, in the high temperature side refrigeration cycle, the superheat degree of the suction side refrigerant is calculated from the difference between the refrigerant temperature (evaporation temperature) of the heat exchanger and the suction side refrigerant temperature of the compressor, and the high temperature side expansion The opening and closing of the device 5 and the aperture amount are controlled.

Further, in the low temperature side refrigeration cycle, the condensation pressure increases with the progress of defrosting, but in order to maintain the evaporation pressure (or evaporation temperature) at a predetermined value, the low temperature side expansion device 9 is opened and closed and the amount of throttling is increased. In order to prevent the degree of heating of the suction-side refrigerant from becoming excessive, the opening / closing and the throttle amount of the second expansion device 12 in the bypass circuit 10 are further controlled.

In the hot water supply system configured as described above, the control unit S controls the high temperature side refrigeration cycle Ra and the low temperature side refrigeration cycle Rb to guide and circulate the refrigerant as described above during the hot water supply operation.

In the intermediate heat exchanger 4, the refrigerant condenses in the secondary side flow path 4b on the low temperature side refrigeration cycle Rb side to release the condensation heat, and the refrigerant condenses in the primary side flow path 4a on the high temperature side refrigeration cycle Ra side. Evaporates while absorbing heat.

Therefore, the difference between the evaporation temperature in the air heat exchanger 8 and the condensation temperature in the water heat exchanger 3 becomes large as a whole hot water supply system, and a high compression ratio can be obtained. The water or hot water led to the hot water pipe H is heated from the primary side flow path 3a of the water heat exchanger 3 that performs condensation in the high temperature side refrigeration cycle Ra in the secondary side flow path 3b of the water heat exchanger 3. Absorbs the heat of condensation and increases the temperature efficiently.

In the secondary flow path 3b of the water heat exchanger 3, the water or hot water changes to hot water having a high temperature, and is led from the water heat exchanger 3 to the hot water storage tank or to the buffer tank on the outgoing side, and again to the water heat exchanger 3 And heated to circulate to a hot water storage tank or a buffer tank on the outgoing side. Alternatively, the hot water is directly supplied from the water heat exchanger 3 to the hot water tap.

Further, the control unit S is represented by a difference between the refrigerant evaporation temperature in the primary flow path 4a of the intermediate heat exchanger 4 and the refrigerant suction temperature of the high temperature compressor 1 in the high temperature side refrigeration cycle Ra during the hot water supply operation. The throttle amount of the high temperature side expansion device 5 is optimally controlled so that the degree of superheat is constant.
In the low temperature side refrigeration cycle Rb, the low temperature side expansion device is configured so that the degree of superheat represented by the difference between the refrigerant evaporation temperature in the air heat exchanger 8 and the refrigerant suction temperature of the low temperature side compressor 6 is constant. The aperture amount of 9 is optimally controlled.

Therefore, the refrigerant circulation amount is appropriately maintained in each refrigeration cycle Ra, Rb, and the heat exchange efficiency of the water heat exchanger 3, the intermediate heat exchanger 4, and the air heat exchanger 8 can be improved. As a result, in the secondary side flow path 3b of the water heat exchanger 3, the water guided to the hot water pipe H or the hot water is efficiently heated.

In particular, if the hot water supply operation is continued under a condition where the outside air temperature is low, the air heat exchanger 8 performs an evaporation action of the refrigerant in the low temperature side refrigeration cycle Rb, so that the condensed water generated here is frozen and becomes frost. , May stick as it is. In this case, the thickness of the frost increases with the passage of time, and the heat exchange efficiency in the air heat exchanger 8 decreases.

The control unit S receives a detection signal from a temperature sensor attached to the air heat exchanger 8 and receives a detection signal from other sensors to determine the necessity of a defrosting operation for the air heat exchanger 8. . As a result, the defrosting operation is performed, but the control unit S actually performs the control described below.

That is, the control unit S simultaneously switches and controls the four-way switching valve 2 of the high temperature side refrigeration cycle Ra and the four way switching valve 7 of the low temperature side refrigeration cycle Rb. In each refrigeration cycle Ra, Rb, the refrigerant circulates in the opposite direction to that in the hot water supply operation described above.

In the low temperature side refrigeration cycle Rb, hot gas that is a high-temperature and high-pressure gas refrigerant discharged from the low-temperature side compressor 6 is led to the air heat exchanger 8 through the four-way switching valve 7 and releases high heat. Therefore, the frost adhering to the air heat exchanger 8 is gradually melted and dropped as drain water, and the thickness of the frost decreases with time.

During such a defrosting operation, the control unit S detects a refrigerant evaporation temperature in the primary side flow path 3a of the water heat exchanger 3 that functions as an evaporator in the high temperature side refrigeration cycle Ra, and a high temperature A detection signal is received from a temperature sensor 16 a that detects the suction refrigerant temperature of the side compressor 1.
And the control part S controls the amount of throttling of the high temperature side expansion device 5 so that the degree of superheat represented by the difference between the refrigerant evaporation temperature and the refrigerant suction temperature becomes constant (target value).

If the above defrosting operation is continued, the frost adhering to the air heat exchanger 8 is melted, and the background is partially exposed, and the exposed portion is enlarged. The exposed portion comes into contact with air to exchange heat, and the air heat exchanger 8 is cooled only by natural convection, so that the gas refrigerant guided to the air heat exchanger 8 is not completely condensed. Become.

Therefore, the high pressure in the low temperature side refrigeration cycle Rb rises, and the low pressure rises accordingly. If the low pressure is too high, if the low temperature side compressor 6 is a rotary compressor, the refrigerant circulation amount becomes excessive, the discharge amount of the lubricating oil discharged together with the gas refrigerant increases, and the discharge valve may be cracked. . Moreover, the winding which comprises an electric motor part will be in an overheated state, and there exists a possibility that a short circuit accident may arise.

The control part S is detected by an evaporation temperature obtained by calculating from the evaporation pressure detected by the pressure sensor 18b provided on the suction part b side of the low temperature side compressor 6 or by a temperature sensor provided in the intermediate heat exchanger 4. The evaporating temperature is compared with the reference temperature stored in the control unit S. When it is confirmed that the detected evaporation temperature exceeds a predetermined value (reference temperature), the control unit S performs the following control on the low temperature side refrigeration cycle Rb.

That is, the control unit S adjusts the throttle amount of the low temperature side expansion device 9 so that the refrigerant evaporation temperature in the secondary side flow path 4b of the intermediate heat exchanger 4 functioning as an evaporator becomes constant (target value). Control.
During the defrosting operation, since the refrigerant between the air heat exchanger 8 and the low temperature side expansion device 9 is in a supercooled state, the low temperature side expansion device 9 is controlled so that the refrigerant is in a two-phase state, or the liquid refrigerant is It can be led to the secondary flow path 4 b of the intermediate heat exchanger 4.

Further, the controller S bypasses the superheat degree expressed by the difference between the refrigerant evaporation temperature of the secondary side flow path 4b of the intermediate heat exchanger 4 and the refrigerant suction temperature of the low temperature side compressor 6 so as to be constant. The second expansion device 12 of the circuit 10 is opened to control the throttle amount. The liquid refrigerant condensed in the air heat exchanger 8 is supplied to the refrigerant pipe between the four-way switching valve 7 and the intermediate heat exchanger 4 via the bypass circuit 10.

As a result, the refrigerant derived from the secondary side flow path 4b of the intermediate heat exchanger 4 and the refrigerant supplied via the bypass circuit 10 are mixed, and the refrigerant suction temperature of the low temperature side compressor 6 is reduced. Cooling is performed so that the superheat of the suction refrigerant is in an appropriate state. The degree of superheat in the low temperature side refrigeration cycle Rb is reduced, and the excessive refrigerant circulation amount is corrected, thereby preventing the above-described problems.

Moreover, at the time of defrosting operation, the primary side flow path 3a of the water heat exchanger 3 in the high temperature side refrigeration cycle Ra functions as an evaporator, and water or hot water led to the secondary side flow path 3b of the hot water pipe H is used. Take away the latent heat of evaporation. However, when the hot water supply operation is continued for a long time and hot water having a relatively high temperature circulates through the hot water pipe H, the refrigerant evaporation temperature in the water heat exchanger primary side flow path 3a becomes higher than a predetermined value.

That is, in the high temperature side refrigeration cycle Ra, the refrigerant evaporation temperature changes according to the hot water temperature circulating through the hot water pipe H and the hot water flow rate. On the other hand, in the low temperature side refrigeration cycle Rb, the refrigerant condensing temperature in the air heat exchanger 8 is about 0 to 10 ° C. due to the property of defrosting operation.

The refrigerant evaporation temperature in the secondary side flow path 4b of the intermediate heat exchanger 4 serving as an evaporator in the low temperature side refrigeration cycle Rb is about 0 ° C., although it depends on the size and opening of the low temperature side expansion device 9. When the temperature of the hot water circulating through the hot water pipe H is about 60 ° C., the refrigerant evaporation temperature in the primary side flow path 3a of the water heat exchanger 3 in the high temperature side refrigeration cycle Ra is about 45 ° C. (target superheat degree: 10K). It is.

Naturally, the refrigerant condensing temperature in the primary side flow path 4a of the intermediate heat exchanger 4 in the high temperature side refrigeration cycle Ra is higher than the refrigerant evaporating temperature (assuming 70 ° C.). Therefore, the degree of superheat of the low temperature side refrigeration cycle Rb is about 60K even if it is estimated to be small, resulting in an excessive state.

If the degree of superheat is too large, the refrigerant density decreases and the refrigerant circulation rate cannot be secured, resulting in prolonged defrosting time. When the low temperature side compressor 6 is a rotary compressor, the refrigerant circulation amount becomes excessive, and the above-described problem may occur.
When the temperature of the hot water circulating through the hot water pipe H reaches about 70 ° C., the refrigerant evaporation temperature is about 55 ° C. and the refrigerant condensation temperature is about 80 ° C. in the high temperature side refrigeration cycle Ra. As a result, the degree of superheat in the low temperature side refrigeration cycle Rb is expected to be about 70K, which causes a significant adverse effect.

As described above, in the hot water supply system employing the two-way refrigeration cycle, the defrosting operation for the air heat exchanger 8 of the low temperature side refrigeration cycle Rb is performed as the temperature of the hot water circulating through the hot water pipe H increases. 6 is a severe condition. Naturally, with the passage of time, the high temperature side compressor 1 of the high temperature side refrigeration cycle Ra is affected, and the same state is caused.

In the above-described situation, the control unit S performs the throttle control by opening the secondary expansion device 12 of the bypass circuit 10 in the low temperature side refrigeration cycle Rb. That is, after the gas refrigerant discharged from the low-temperature side compressor 6 is led to the air heat exchanger 8 and condensed to become liquid refrigerant, a part of the liquid refrigerant is led to the low-temperature side expansion device 9 and the rest The liquid refrigerant is guided to the bypass circuit 10.

In particular, the flow rate of the liquid refrigerant led to the bypass circuit 10 is reduced by the second expansion device 12, the pressure is reduced, the refrigerant is supplied to the refrigerant pipe between the four-way switching valve 7 and the intermediate heat exchanger 4, and the degree of superheat is reduced. The refrigerant is mixed with the refrigerant derived from the secondary side flow path 4b of the intermediate heat exchanger 4 which is large, and the superheat degree of the refrigerant sucked by the low temperature side compressor 6 is cooled to an appropriate state. As a result, it is possible to eliminate all of the increase in the refrigerant circulation amount and the adverse effects associated therewith as described above.

FIG. 2 is a configuration diagram of the refrigeration cycle of the hot water supply system according to the second embodiment.
Here, the bypass circuit 10 is different from that of the second expansion device 12 in series in that the electromagnetic on-off valve 25 is provided, and other configurations are completely the same. Therefore, the same number is attached | subjected to the same component and new description is abbreviate | omitted.

If the electromagnetic on-off valve 25 is closed during the hot water supply operation, the second expansion device 12 does not need to be fully closed, and simplification of control is obtained. In short, it is sufficient that the bypass circuit 10 is not opened during the hot water supply operation. It should be noted that there is no problem even if a check valve is used as a substitute for the electromagnetic opening / closing valve 25.

If a non-azeotropic refrigerant mixture is used for the low temperature side refrigeration cycle Rb, the evaporating temperature of the refrigerant is not constant, and even if the evaporating temperature of the air heat exchanger 8 is detected by a temperature sensor, detection accuracy cannot be expected. Therefore, the low pressure is read by the pressure sensor 18b, and the control unit S that receives the detection signal calculates and obtains the evaporation temperature, thereby improving the controllability and obtaining the value of the evaporation temperature accurately.

If the pump 13 used for the hot water pipe H is fixed in flow rate, and the flow rate of the hot water led here is constant, the water temperature on the inlet side of the secondary side flow path 3b of the water heat exchanger 3 during the defrosting operation. Accordingly, the evaporation pressure in the primary side flow path 3a of the water heat exchanger 3 as an evaporator changes. That is, the refrigerant evaporating pressure is changed by the temperature of the hot water circulating through the hot water pipe H.

Therefore, if the initial operating frequency of the high temperature side compressor 1 is made constant at the start of the defrosting operation, when the hot water temperature on the hot water pipe H side rises, the refrigerant circulation amount becomes excessive, the high pressure rises, and the high temperature side compressor 1 may stop abnormally. Alternatively, if the hot water temperature is extremely lowered, the refrigerant circulation amount is insufficient and the compression ratio becomes low, and the defrost time for the air heat exchanger 8 becomes long.

As described above, the control unit S receives a detection signal from the water temperature sensor 19 provided on the water inlet side of the water heat exchanger tertiary side flow path 3b every predetermined time. Therefore, at the start of the defrosting operation, the control unit S receives the detection signal from the water temperature sensor 19 and performs calculation, and determines the optimum initial operating frequency of the high temperature side compressor 1 for each temperature of the hot water circulating through the hot water pipe H. Control to do.

Since the pump 13 has a fixed flow rate, it is not necessary to consider the influence of the flow rate of the hot water led to the hot water pipe H when determining the initial operating frequency of the high-temperature compressor 1 at the start of the defrosting operation. Therefore, simplification of control is obtained and stable defrosting operation can always be performed.

Moreover, when the flow rate of the water led to the hot water pipe H or the flow rate of the hot water fluctuates, the heat passage rate and the outlet water temperature in the secondary flow path 3b of the water heat exchanger 3 fluctuate, and the high temperature side refrigeration cycle Ra evaporates. Pressure changes. Therefore, it is necessary to determine an optimal operation frequency for each flow rate of water or hot water in the hot water pipe H.

That is, the inlet side hot water temperature and the hot water flow rate in the secondary flow path 3b of the water heat exchanger 3 in the hot water pipe H are measured, and the initial frequency of the high temperature side compressor 1 is determined according to the values at that time. Thus, a stable defrosting operation can be performed.
Specifically, the pump 13 provided in the hot water pipe H is replaced with a variable flow rate pump. In the hot water pipe H, the water temperature sensor 19 as the water temperature detecting means is provided on the water inlet side of the secondary flow path 3b of the water heat exchanger 3, and the flow rate sensor 21 as the flow rate detecting means is provided on the hot water outlet side. There is no.

As the flow rate detection means, in addition to the flow rate sensor, a water pressure sensor is provided on the water inlet side and the water outlet side of the secondary side flow path 3b of the water heat exchanger 3 in the hot water pipe H, and the water amount is determined from the pressure difference between them. May be calculated by calculation.
The control unit S receives the detection signals from the water temperature sensor 19 and the flow rate sensor 21 at the start of the defrosting operation, performs calculation, and controls the initial operating frequency in the high temperature side compressor 1 as a result. The operating frequency of the low temperature side compressor 6 at this time may be constant.

For example, an operating frequency at which the condensation pressure in the high temperature side refrigeration cycle Ra is constant is determined for each hot water temperature and hot water flow rate. This data is given as an internal parameter and used as a table as shown in [Table 1] below. The unit of inlet water temperature is [° C]. The unit of the compressor initial (operation) frequency is [Hz]. The unit of the water flow rate is [L / min].

Alternatively, an approximate expression based on the hot water temperature and the hot water flow rate is created, and the initial operating frequency of the high temperature side compressor 1 at the start of the defrost operation is determined.
In any case, the initial operating frequency increases as the hot water temperature decreases, but in general, the compressor is not assumed to operate at an extremely high rotational speed. For this reason, when the rotational speed of the electric motor part constituting the compressor is too large, the efficiency is remarkably deteriorated, and the mechanical efficiency of the compression mechanism part tends to be deteriorated.

For example, operation at a high rotational speed exceeding 100 rps should be avoided. Therefore, the initial operating frequency of the high temperature side compressor 1 is suppressed as much as possible so that the target condensing temperature is gradually lowered as the hot water temperature decreases.

Alternatively, it is desirable to control the initial operating frequency of the high-temperature side compressor 1 to reduce the total amount of refrigerant circulation by simultaneously reducing the initial operating frequency of the low-temperature side compressor 6 depending on the hot water temperature. After the high temperature side compressor 1 is operated at the initial operating frequency, the control target is determined and controlled toward the target to complete the defrosting operation.

FIG. 3 is a refrigeration cycle configuration diagram of the hot water supply system according to the third embodiment.
Here, one end portion of the bypass circuit 10 in the low temperature side refrigeration cycle Rb is connected to a midway portion of the refrigerant pipe P that communicates the fourth port d4 of the four-way switching valve 7 and the suction portion b of the low temperature side compressor 6. . The other end of the bypass circuit 10 is connected to the middle part of the refrigerant pipe P that communicates the low temperature side expansion device 9 and the air heat exchanger 8 without change.

Further, a direct acting electronic expansion valve using a rare earth magnet is used as the second expansion device 12 of the bypass circuit 10.
Other configurations are exactly the same. Therefore, the same number is attached | subjected to the same component and new description is abbreviate | omitted.

Rare earth magnets are suitable for miniaturization because of their high magnetic flux density. Also, the electronic expansion valve has good controllability, is small and inexpensive, and is optimal for providing in the bypass circuit 10 that does not require much flow. Since the direct acting type is less expensive than the gear type, it is advantageous for cost reduction and space saving.

However, the rare earth magnet has a characteristic that the residual magnetic flux density and the coercive force are greatly reduced by the temperature rise. When a neodymium magnet is used as the rare earth magnet, the temperature coefficient of residual magnetic flux density is about -0.1% / K, and the temperature coefficient of coercive force is about -0.5% / K. When a samarium cobalt magnet is used, the temperature coefficient of residual magnetic flux density is -0.03% / K, and the temperature coefficient of coercive force is about -0.2% / K (20 ° C.). In order to prevent failure of the electronic expansion valve due to demagnetization, the refrigerant temperature must be kept low.

The other end of the bypass circuit 10 is connected between the inlet of the air heat exchanger 8, the intermediate heat exchanger 4, and the four-way switching valve 7. Therefore, if the low temperature side expansion device 9 is fully opened for some reason during the hot water supply operation, the discharge gas from the low temperature side compressor 6 flows into the second expansion device 12 of the bypass circuit 10.

As a case where the second expansion device 12 is energized during the hot water supply operation, for example, it may occur in a situation where a predetermined capacity is not obtained even though the hot water supply system is operating at a compressor frequency as required. Since the electronic expansion valve is open-loop control, there may be a difference between the actual opening and the required opening. Even if the electronic expansion valve is fully closed at the end of the defrosting operation, it may actually be opened.

At this time, the amount of refrigerant guided to the intermediate heat exchanger 4 is reduced and the heating capacity is reduced. Therefore, when the defrosting operation is finished and the required capacity is not reached after a lapse of a predetermined time, it is expected that the second expansion device 12 is first tightened and fully closed.

FIG. 4 shows the state at this time.
The lower side change is the low temperature side refrigeration cycle Rb, and the upper side change is the high temperature side refrigeration cycle Ra. Td is the refrigerant discharge temperature of the compressor, Ts is the refrigerant suction temperature of the compressor, Tc is the refrigerant condensation temperature, and Te is the refrigerant evaporation temperature. In the high temperature side refrigeration cycle, R245fa is used as the refrigerant, and in the low temperature side refrigeration cycle, R410A is used as the refrigerant.

The refrigerant discharge temperature Td of the compressor greatly exceeds 60 ° C. and becomes 80 ° C. or higher depending on conditions. If the second expansion device 12 is energized in this state, it may cause irreversible demagnetization. In an electronic expansion valve that is generally used, since the allowable upper limit temperature of the refrigerant is 60 to 70 ° C., the second expansion device (electronic expansion valve) 12 may be damaged by energization.

Therefore, the connection destination of one end of the bypass circuit 10 is changed as shown in FIG. Even if the bypass circuit 10 is opened during the hot water supply operation, since the pressure difference is small because of the low pressure lines, almost no refrigerant flows. And since it is a refrigerant | coolant of the expansion-decompression decompression state in the low temperature side expansion apparatus 9, the refrigerant | coolant temperature is low and the reliability as a direct acting type electronic expansion valve is securable.

FIG. 5 is a refrigeration cycle configuration diagram of a hot water supply system according to the fourth embodiment.
Here, the electromagnetic on-off valve 27 and the capillary tube 28 constituting the second expansion device are connected in series to the bypass circuit 10 in the low temperature side refrigeration cycle Rb. And the gas-liquid separator 30 is provided in the middle of the refrigerant | coolant piping P which connects the 4th port d4 of the four-way switching valve 7, and the suction part b of the low temperature side compressor 6. FIG.

Other configurations are exactly the same. Therefore, the same number is attached | subjected to the same component and new description is abbreviate | omitted.
The control unit S controls to close the electromagnetic on-off valve 27 during normal hot water supply operation and to open the electromagnetic on-off valve 27 during defrosting operation. As a result, the same effect as described above can be obtained.

The gas-liquid separator 30 has an excessive amount of cooling liquid and cannot secure the degree of superheat, and even when the liquid refrigerant flows into the suction line of the low temperature side compressor 6, it can be prevented from being backed and damaged. The reliability of the compressor 6 can be improved.

It should be noted that a check valve may be provided in place of the electromagnetic on-off valve 27, and a piping configuration that allows communication only during the defrosting operation may be used. The electromagnetic open / close valve 27 and the check valve are less expensive than the electronic expansion valve as the second expansion device 12 described in the first to third embodiments.

Both the electromagnetic on-off valve 27 and the check valve guarantee that the allowable temperature of the refrigerant is 100 ° C. or higher. Therefore, as described above in the third embodiment (FIG. 3), one end of the bypass circuit 10 is located between the fourth port d4 of the four-way switching valve 7 and the suction portion b of the low temperature side compressor 6. It is possible to connect to the most convenient place according to the piping design.

Further, since the gas-liquid separator 30 is provided on the suction side of the low-temperature side compressor 6, particularly when a high-pressure shell type rotary compressor is used as the low-temperature side compressor 6, the motor part rotor by liquid back is used. This eliminates the possibility of wear and damage to the compressor.

As mentioned above, although this embodiment was described, the above-mentioned embodiment is shown as an example and does not intend limiting the range of embodiment. The novel embodiment can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims

High-temperature side compressor, four-way switching valve, water heat exchanger, high-temperature side expansion device, high-temperature side refrigeration cycle communicating the intermediate heat exchanger via refrigerant piping, low-temperature side compressor, four-way switching valve, intermediate heat exchanger A low-temperature side expansion device, a low-temperature side refrigeration cycle that communicates an air heat exchanger via a refrigerant pipe, a refrigerant that is led to the high-temperature side refrigeration cycle, and a refrigerant that is led to the low-temperature side refrigeration cycle, A binary refrigeration cycle for heat exchange with the intermediate heat exchanger;
A hot water pipe that is piped to the water heat exchanger of the high temperature side refrigeration cycle, heat-exchanges the circulating water or hot water and the refrigerant guided to the high temperature side refrigeration cycle, and raises the water or hot water to a predetermined temperature;
One end is connected to the refrigerant pipe between the four-way switching valve of the low temperature side refrigeration cycle and the intermediate heat exchanger, and the other end is connected to the refrigerant pipe between the low temperature side expansion device of the low temperature side refrigeration cycle and the air heat exchanger. A bypass circuit connected and having a second expansion device in the middle;
At the time of defrosting operation for the air heat exchanger of the low-temperature side refrigeration cycle, the four-way switching valve of the high-temperature side refrigeration cycle and the four-way switching valve of the low-temperature side refrigeration cycle are switched in the opposite direction to those during hot water supply operation, When the low temperature side expansion device of the low temperature side refrigeration cycle controls the evaporation temperature or evaporation pressure of the intermediate heat exchanger, and when it is detected that the superheat degree of the suction refrigerant of the low temperature side compressor exceeds the predetermined value, the bypass Control means for controlling the opening of the second expansion device of the circuit;
A hot water supply system comprising:
Furthermore, the control means includes
During hot water supply operation, in the high temperature side refrigeration cycle, the high temperature side expansion device is controlled so that the degree of superheat represented by the difference between the evaporation temperature in the intermediate heat exchanger and the suction temperature in the high temperature side compressor is constant, In the low temperature side refrigeration cycle, the low temperature side expansion device is controlled so that the degree of superheat represented by the difference between the evaporation temperature in the air heat exchanger and the suction temperature in the low temperature side compressor is constant,
During the defrosting operation, in the high temperature side refrigeration cycle, the high temperature side expansion device is controlled so that the degree of superheat represented by the difference between the evaporation temperature in the water heat exchanger and the suction temperature in the high temperature side compressor is constant. The low temperature side expansion device is controlled so that the evaporation pressure in the intermediate heat exchanger is constant in the low temperature side refrigeration cycle, and is expressed by the difference between the evaporation temperature of the intermediate heat exchanger and the suction temperature of the low temperature side compressor. The hot water supply system according to claim 1, wherein the second expansion device of the bypass circuit is controlled so that the degree of superheat becomes constant.
The hot water pipe is provided with water temperature detecting means on the water inlet side,
Further, the control means performs control for determining an initial operation frequency in the high temperature side compressor of the high temperature side refrigeration cycle based on a detection signal from the water temperature detection means at the start of the defrosting operation. The hot water supply system according to claim 1.
The hot water pipe has a flow rate variable pump and water temperature detection means on the water inlet side, and a flow rate detection means on the water inlet side or hot water outlet side,
Further, the control means performs control for determining an initial operation frequency in the high-temperature side compressor of the high-temperature side refrigeration cycle based on detection signals from the water temperature detection means and the flow rate detection means at the start of the defrosting operation. The hot water supply system according to claim 1, wherein
The hot water supply system according to any one of claims 1 to 4, wherein the second expansion device provided in the bypass circuit is an electronic expansion valve using a rare earth magnet.