JP5802514B2 - Heat pump water heater - Google Patents

Description

  The present invention relates to a heat pump type water heater.

  2. Description of the Related Art Conventionally, there has been known a heat pump type water heater having a boiling function for driving a heat pump cycle using midnight power or the like and heating low temperature water to store hot water at a desired temperature in a hot water storage tank. In such a heat pump type hot water heater, a water-refrigerant heat exchanger provided in a heat pump cycle and a hot water storage tank are connected by piping, and water in the hot water storage tank is circulated in the connected piping. And the heat pump type hot water heater performs boiling by heat exchange between the water in the hot water storage tank and the refrigerant in the refrigeration cycle in the water-refrigerant heat exchanger. For such a heat pump type hot water heater, a refrigeration cycle apparatus has been proposed that uses carbon dioxide as a refrigerant, which has an ozone depletion coefficient of zero and a global warming coefficient that is much smaller than that of chlorofluorocarbons.

  When a refrigerant having a low critical temperature such as carbon dioxide is used in the refrigeration cycle apparatus, condensation does not occur on the high pressure side, and the supercritical cycle is operated at a critical pressure or higher. However, in the operation of the supercritical cycle, the high pressure side and the low pressure that are optimal for operation depend on the external environment conditions such as the outside air temperature, the target boiling temperature, and the incoming water temperature of the water flowing into the water-refrigerant heat exchanger. Because the refrigerant charge amount on the side is different, the refrigerant charge amount that is optimal for operation is different in order to adjust to the optimum refrigerant charge amount, so a refrigerant amount adjustment container such as a buffer refrigerant receiver and an accumulator is provided in the refrigeration cycle, A technique for adjusting the amount of refrigerant is disclosed (Patent Document 1).

Japanese Patent Publication No. 7-18602

  In the case of the technology disclosed in Patent Document 1, it is necessary to provide a refrigerant amount adjusting container such as a refrigerant receiver or accumulator having a large capacity in the refrigeration cycle in order to store the liquid refrigerant.

  Therefore, even if the external environmental conditions such as the outside air temperature, the boiling target temperature, the incoming water temperature of the water flowing into the water-refrigerant heat exchanger, etc. change and the amount of refrigerant optimal for operation changes, the refrigerant receiver and accumulator Therefore, it is considered that a heat pump type water heater capable of performing a boiling operation is desired.

  The present invention does not require the use of a refrigerant amount adjusting container such as a refrigerant receiver or an accumulator even if the refrigerant charge amount that is optimal for operation changes due to changes in various conditions, and performs efficient boiling operation. It is to provide a heat pump type hot water heater that can be used.

The present invention relates to a compressor that compresses a refrigerant, a water-refrigerant heat exchanger that heats water with a high-temperature and high-pressure refrigerant discharged from the compressor, and an inflow from the water-refrigerant heat exchanger through a pressure reducing valve. An evaporator that exchanges heat between the low-temperature and low-pressure refrigerant to be returned to the compressor and an internal heat exchanger that exchanges heat between the refrigerant flowing out of the water-refrigerant heat exchanger and the refrigerant flowing out of the evaporator. In the heat pump type hot water heater provided with no refrigerant amount adjusting means, when the temperature of the water flowing into the water-refrigerant heat exchanger rises, the pressure reducing valve is opened to increase the rotational speed of the compressor.

  According to the present invention, a high-efficiency boiling operation can be performed while maintaining the optimum high-pressure side pressure for boiling operation, and even if the incoming water temperature flowing into the water-refrigerant heat exchanger rises, the low-pressure side is maintained. Since the refrigerant is sent to the evaporator, a refrigerant amount adjusting means such as a refrigerant receiver and an accumulator is unnecessary, and a heat pump type hot water heater in which the apparatus is miniaturized can be provided.

It is composition explanatory drawing of the heat pump type water heater which concerns on embodiment of this invention. It is a flowchart for demonstrating the procedure in which a control part controls a pressure reducing valve and a compressor at the time of the boiling operation of the heat pump type water heater which concerns on embodiment of this invention. It is a graph which shows the relationship between the target discharge refrigerant | coolant pressure and COP in the heat pump type hot water heater which concerns on embodiment of this invention. It is a graph which shows the relationship between the incoming water temperature, the target discharge refrigerant | coolant pressure, and COP in the heat pump type hot water heater which concerns on embodiment of this invention. It is a graph which shows the relationship between the refrigerant | coolant possession ratio and incoming water temperature in an evaporator in the heat pump type hot water heater which concerns on embodiment of this invention, the ratio of compressor rotation speed, and incoming water temperature. It is a graph which shows the relationship between the internal heat exchanger in the heat pump type water heater which concerns on embodiment of this invention, the refrigerant | coolant holding ratio in a high voltage | pressure side, and incoming water temperature.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. The heat pump type water heater of the present embodiment has a function of suppressing the decrease in the refrigerant amount on the low pressure side by adjusting the opening of the pressure reducing valve when the temperature of the water flowing into the water-refrigerant heat exchanger rises. Is. Specifically, a detection device for detecting the pressure on the high-pressure side is provided, and the compressor discharge pressure target value calculated from the outside air temperature, the boiling target temperature, and the incoming water temperature flowing into the water-refrigerant heat exchanger and the high-pressure side Provided a control function to adjust the opening of the pressure reducing valve so that the pressure values detected by the pressure detection device are the same, and when the temperature of the water flowing into the water-refrigerant heat exchanger rises, The opening of the pressure reducing valve is adjusted so as to move the refrigerant from the side to the low pressure side, and the function of suppressing the decrease in the amount of refrigerant held on the low pressure side as the incoming water temperature rises is provided.

  Below, after demonstrating the whole structure of the heat pump type water heater which concerns on this embodiment, it demonstrates more specifically about an above described function.

  As shown in FIG. 1, the heat pump type water heater includes a heat pump unit 1 and a hot water storage tank unit 2. Incidentally, the heat pump unit 1 and the hot water storage tank unit 2 are structured to be connected by connecting pipes 3a and 3b when the heat pump hot water heater is arranged on the site.

  The refrigeration cycle of the heat pump unit 1 includes a compressor 4, a water-refrigerant heat exchanger 5, an internal heat exchanger 6, a pressure reducing valve 7, an evaporator 8, a blower fan 9, and a heat pump unit control unit 20. And mainly consists of. The compressor 4, the water-refrigerant heat exchanger 5, the internal heat exchanger 6, the pressure reducing valve 7, and the evaporator 8 are annularly connected by piping so that the refrigerant circulates in this order. Note that carbon dioxide is used as the refrigerant in the present embodiment. The heat pump unit 1 uses a supercritical vapor compression heat pump cycle in which the discharge pressure of the refrigerant (carbon dioxide) discharged from the compressor 4 is equal to or higher than the critical pressure.

  The compressor 4 compresses the refrigerant returned from the annular circuit, and sends out the compressed high-temperature and high-pressure gas refrigerant (hereinafter also referred to as hot gas) to the annular circuit again. More specifically, the refrigerant returned from the evaporator 8 is compressed and sent out toward the water-refrigerant heat exchanger 5.

  The capacity of the compressor 4 can be controlled, and when high-temperature hot water storage (for example, 90 ° C.) is performed, the compressor 4 is operated at a higher rotational speed (for example, 3000 to 4000 rotations / minute) than usual. Moreover, when driving | running by normal hot water storage temperature (for example, 65 degreeC), it drive | operates by a comparatively slow rotational speed (for example, 2000-3000 rotation / min). Further, the compressor 4 can control the rotation speed from a low speed (for example, 1000 rotations / minute) to a high speed (for example, 6000 rotations / minute) by PWM control, voltage control (for example, PAM control) and combination control thereof. It has become.

  A pressure sensor 15 for detecting the high-pressure side refrigerant pressure (compressor discharge refrigerant pressure) of the compressor 4 is disposed near the compressor 4 in a pipe connecting the compressor 4 and a water-refrigerant heat exchanger 5 described below. Is provided. Incidentally, this pipe is connected with the inlet of the refrigerant | coolant heat exchanger tube 2a demonstrated below with the water-refrigerant heat exchanger 5. FIG.

  The water-refrigerant heat exchanger 5 functions as a radiator and includes a refrigerant heat transfer tube 5a through which hot gas discharged from the compressor 4 circulates and a water heat transfer tube 5b through which water flows. These refrigerant heat transfer tubes 5a and water heat transfer tubes 5b are provided in close contact so that the refrigerant and water exchange heat with each other. The water-refrigerant heat exchanger 5 may have a structure that is not in close contact (for example, a structure in which the refrigerant heat transfer tube 5a is passed through the water heat transfer tube 5b) as long as the heat can be exchanged between the refrigerant and water. .

  The internal heat exchanger 6 has a function of exchanging heat between the high-pressure side refrigerant and the low-pressure side refrigerant in the refrigeration cycle, and the refrigerant heat transfer tube 6a through which the high-pressure refrigerant flowing out of the water-refrigerant heat exchanger 5 is circulated. And a refrigerant heat transfer tube 6b for circulating the low-pressure refrigerant flowing out of the evaporator 8. These refrigerant heat transfer tubes 6a and refrigerant heat transfer tubes 6b are provided in close contact so that the high-pressure side refrigerant and the low-pressure side refrigerant exchange heat with each other, and the refrigerant flowing out of the water-refrigerant heat exchanger 5 is By cooling with the refrigerant flowing out of the evaporator 8, it has a function of reducing the dryness of the refrigerant at the inlet of the evaporator 8. Conversely, the refrigerant flowing out of the evaporator 8 is heated by the refrigerant flowing out of the water-refrigerant heat exchanger 5, thereby increasing the temperature of the refrigerant sucked by the compressor 4 and improving the performance during the boiling operation. It has a function to make it. Further, the internal heat exchanger 6 may have a structure in which the high-pressure side refrigerant and the low-pressure side refrigerant can exchange heat (for example, a structure in which the high-pressure side refrigerant pipe 6a is passed through the low-pressure side refrigerant pipe 6b). .

  The pressure reducing valve 7 is provided in the middle of a pipe disposed between the internal heat exchanger 6 and the evaporator 8, and an electric pressure reducing valve is used. The pressure reducing valve 7 decompresses the high-pressure refrigerant from the internal heat exchanger 6 and sends it to the evaporator 8 as a low-temperature and low-pressure refrigerant that easily evaporates. The pressure reducing valve 7 can adjust the throttle opening (opening / closing degree), and the heat pump unit controller 19 can change the throttle opening to adjust the high-pressure side pressure in the heat pump unit 1. Using this function, the heat pump unit controller 19 adjusts the refrigerant discharge pressure of the compressor 4 by changing the throttle opening of the pressure reducing valve 7 as will be described later.

  Note that when the evaporator 8 is frosted, the pressure reducing valve 7 also functions to perform defrosting with the throttle opening fully opened.

  The evaporator 8 performs heat exchange between air (air blowing) that has taken in outside air by rotation of the blower fan 9 and low-temperature and low-pressure refrigerant that circulates in the evaporator 8, and pumps up heat from the outside air. Then, the refrigerant is returned from the evaporator 8 to the compressor 4 through the internal heat exchanger 6.

  Reference numeral 18 is a temperature sensor that detects the outside air temperature, and the outside air temperature sensor 18 in this embodiment is upstream of the air flow formed by the blower fan 9 so as to detect the temperature of the air flowing into the evaporator 8. Arranged on the side. As will be described later, the heat pump control unit 19 calculates the target discharge refrigerant pressure value of the compressor 4 using the temperature detected by the outside air temperature sensor 18 as one of reference elements.

  Reference numeral 21 a is a water delivery pipe, and the delivery pipe 21 a sends water heated by the refrigerant to the water-refrigerant heat exchanger 5. One end of the delivery pipe 21 a is connected to the inlet of the water heat transfer pipe 5 b of the water-refrigerant heat exchanger 5. The delivery pipe 21a is connected to the bottom side of the hot water storage tank 11 to be described later through the connection pipe 3a and the pipe 13b to be described later.

  In this delivery pipe 21 a, the circulation pump 12 is disposed on the upstream side of the water-refrigerant heat exchanger 5. In addition, the circulation pump 12 in this embodiment drives so that the water of the hot water storage tank 11 may be sent into the inlet side of the water heat exchanger tube 5b. The circulation pump 12 functions to circulate water in a water circulation path to be described later, and serves as a water circulation device. Incidentally, the circulation pump 12 is configured so that the heat pump unit controller 19 can freely select the flow rate (mass flow rate), flow rate, and pressure of water in the circulation path.

  A heat exchanger inlet water temperature sensor 16 is provided near the water-refrigerant heat exchanger 5 of the delivery pipe 21a. The heat exchanger inlet water temperature sensor 16 detects the temperature of water at the inlet of the water-refrigerant heat exchanger 5. As will be described later, the heat pump control unit 19 calculates the target discharge refrigerant pressure value of the compressor 4 using the temperature detected by the heat exchanger inlet water temperature sensor 16 as one of the reference elements.

  Reference numeral 21 b is a water return pipe, and one end of the return pipe 21 b is connected to the outlet of the water heat transfer pipe 5 b of the water-refrigerant heat exchanger 5. The return pipe 21 b returns water (hot water) heated by the refrigerant from the water-refrigerant heat exchanger 5 to the hot water storage tank 11. A heat exchanger outlet water temperature sensor 17 that detects the outlet water temperature of the water-refrigerant heat exchanger 5 is provided near the water-refrigerant heat exchanger 5 in the return pipe 21b. The return pipe 21b is connected to the tower top side of the hot water storage tank 11 through the connection pipe 3b and the pipe 14b described later.

  Next, the hot water storage tank unit 2 which comprises a heat pump type hot water heater with such a heat pump unit 1 is demonstrated.

  The tank unit 2 includes a hot water storage tank 11 for storing water (hot water).

  As described above, water (hot water) fed from the outlet of the water heat transfer pipe 5b in the water-refrigerant heat exchanger 5 flows into the tower top of the hot water storage tank 11 via the pipe 14b. From the bottom of the hot water storage tank 11, water flows into the inlet of the water heat transfer pipe 5b of the water-refrigerant heat exchanger 5 through the pipe 13b as described above.

  That is, the pipes 13a, 3a, 21a, 21b, 3b, and 14b are provided so that hot water is sent from the water-refrigerant heat exchanger 5 to the hot water storage tank 11 and water in the hot water storage tank 11 is sent to the water-refrigerant heat exchanger 5. The water-refrigerant heat exchanger 5 and the hot water storage tank 11 are connected to form a water (hot water) water circulation path.

  Further, a water supply source (not shown) such as a water supply is connected to the bottom of the hot water storage tank 11 via a water supply pipe 13a, and hot water in the hot water storage tank 11 is led out to the top of the hot water storage tank 11 to give a predetermined hot water supply. A hot water supply pipe 14a for supplying hot water to a stopper (not shown) is connected. Although not shown, a branch pipe may be provided so as to branch from the water supply pipe 13a and to join the hot water supply pipe 14a via a predetermined hot water mixing valve. According to such a branch pipe, by adjusting the amount of water flowing from the water supply pipe 13a to the hot water supply pipe 14a according to the degree of opening of the hot water / water mixing valve, the temperature of the hot water coming out of the hot water tap is adjusted. Can do.

  The heat pump unit controller 19 includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like, and comprehensively controls the heat pump unit 1 according to the present embodiment in accordance with a program stored therein. It is like that.

  The heat pump unit controller 19 controls the rotational speed of the compressor 4 based on the outlet water temperature of the water-refrigerant heat exchanger 5 detected by the heat exchanger outlet water temperature sensor 17. Specifically, the heat pump unit control unit 19 sets the compressor 4 so that the temperature detected by the heat exchanger outlet water temperature sensor 17 becomes a preset outlet water temperature target value (target hot water temperature). To control the rotation speed. That is, when the detected temperature (measured value) of the heat exchanger outlet water temperature sensor 17 is lower than the target value, the rotational speed of the compressor 4 is increased, and conversely, the detected temperature (measured value) is high. For this, the rotational speed of the compressor 4 is slowed down.

  Further, the heat pump unit control unit 19 controls the amount of water that the circulation pump 12 sends to the water heat transfer pipe 5 b of the water-refrigerant heat exchanger 5 based on the target rotational speed of the compressor 4 that is obtained in advance. Specifically, when the actual rotational speed is slower than the target rotational speed of the compressor 4, the circulation pump 12 is controlled so that the amount of water fed into the water heat transfer pipe 5b is increased. When the actual rotational speed of the compressor 4 is fast, the circulation pump 12 is controlled so that the amount of water fed into the water heat transfer pipe 5b is reduced.

  Then, as will be described in detail later, the heat pump unit control unit 19 determines that the discharge refrigerant pressure of the compressor 4 detected by the pressure sensor 15 is the outside air temperature, the water inlet temperature of the water-refrigerant heat exchanger 5, and the water- The opening degree of the pressure reducing valve 7 is controlled so as to coincide with the target discharge refrigerant pressure value calculated from the target hot water temperature with respect to the outlet water temperature of the refrigerant heat exchanger 5. That is, when the detected pressure (measured value) of the pressure sensor 15 is lower than the target value, the opening degree of the pressure reducing valve 7 is decreased. On the contrary, when the detected pressure (measured value) is high, the pressure reducing valve 7 Increase the opening of 7.

  The hot water tank unit control unit 20 includes a CPU, a ROM, a RAM, various interfaces, an electronic circuit, and the like. The heat pump hot water heater according to the present embodiment is comprehensively configured according to a program stored therein. The information stored in the hot water storage tank 11 is obtained from information from a remote controller (not shown) serving as an interface with the user of the heat pump water heater, or from a temperature sensor (not shown) provided in the hot water storage tank 11. The target hot water temperature to be boiled up and the boiling start time are calculated from information on the amount of hot water, etc., and a heating operation start command is issued to the heat pump unit controller 19 and the target hot water temperature is transmitted.

  Next, the operation of the heat pump type water heater according to the present embodiment will be described.

  In this heat pump type hot water supply apparatus, water is supplied to fill the hot water storage tank 11 prior to securing a predetermined amount of hot water at a predetermined temperature in the hot water storage tank 11. At this time, water is added to the hot water storage tank 11 from a water supply source (not shown) via a water supply pipe 13a so as to be added to the remaining hot water. Of course, when the hot water storage tank 11 is empty, all of it is filled with water.

  Hereinafter, the hot water remaining in the hot water storage tank 11 and the newly added water may be simply referred to as “water”.

  And a heat pump type hot water heater implements a hot water storage operation process after the hot water storage tank 11 is filled with water.

  The heat pump type water heater supplies hot gas (high-temperature and high-pressure refrigerant) discharged from the started compressor 4 to the refrigerant heat transfer tube 5a of the water-refrigerant heat exchanger 5 (heat radiator). The hot gas sent to the refrigerant heat transfer tube 5a releases heat to the water in the water heat transfer tube 5b. And the water in the water heat exchanger tube 5b is heated with hot gas.

  Next, the refrigerant sent out from the refrigerant heat transfer tube 5a of the water-refrigerant heat exchanger 5 (radiator) further radiates heat to the low-pressure side refrigerant in the internal heat exchanger 6, and then the pressure reducing valve 7 ( After being depressurized by the pressure reducing valve, it flows into the evaporator 8. The low-temperature and low-pressure refrigerant that has flowed in draws heat from the outside air when it is evaporated by the wind sent from the blower fan 9. Thereafter, the refrigerant further absorbs heat from the high-pressure side refrigerant in the internal heat exchanger 6 and then returns to the compressor 4 to be compressed again.

  On the other hand, the water filled in the hot water storage tank 11 is sent into the water heat transfer pipe 5b of the water-refrigerant heat exchanger 5 through the delivery pipe 21a when the circulation pump 12 is activated. Then, as described above, the fed-in water is heated by the refrigerant to become hot water and flows into the return pipe 21b.

  The hot water flowing into the return pipe 21b returns to the hot water storage tank 11 and is stored. Thus, while water circulates between the hot water storage tank 11 and the water-refrigerant heat exchanger 5, the heat pump hot water heater secures a predetermined amount of hot water at a predetermined temperature in the hot water storage tank 11.

  And when a heat pump type water heater performs the boiling operation of water in this way, the heat pump unit control part 19 controls the compressor 4 and the pressure-reduction valve 7 as follows. Next, FIG. 2 to be referred to is a flowchart for explaining a procedure in which the control unit controls the pressure reducing valve and the compressor during the boiling operation of the heat pump type hot water heater according to the present embodiment.

  In the hot water storage tank unit control unit 20, a target hot water temperature (for example, the above-described 90 ° C. or 65 ° C.) is set, and an operation start command is issued to the heat pump unit control unit 19. At this time, the target hot water temperature includes the temperature of the water sent from the water supply pipe 13a to the hot water storage tank 11, the detected temperature of the outdoor air temperature sensor 18 (the outdoor air temperature), the amount of remaining hot water in the hot water storage tank 11, and the amount of hot water by the user per day. It can be set based on the usage amount and at least one selected from a request value requested by the user from the remote controller.

  The heat pump unit control unit 19 that has received the operation start command starts the boiling operation of the heat pump unit. As shown in FIG. 2, the heat pump unit controller 19 having received the command starts the compressor 4, the fan motor 10, the water circulation pump 12, and the pressure reducing valve 7 with initial values, and then sets the target hot water temperature and the target discharge refrigerant pressure. Set (step S1).

  The target discharge refrigerant pressure is the detected temperature of the heat exchanger inlet water temperature sensor 16 (the temperature of the water sent to the water heat transfer pipe 5b of the water-refrigerant heat exchanger 5 (inlet water temperature)), the aforementioned target hot water temperature, and It can be set based on at least one selected from the detection temperature (outside temperature) of the outside temperature sensor 18.

  Next, the heat pump unit control unit 19 detects the discharge refrigerant pressure of the compressor 4 with the pressure sensor 15 (step S2), and whether or not the discharge refrigerant pressure is equal to the target discharge refrigerant pressure (refrigerant pressure = target). Pressure) is determined (step S3). When it is determined that the discharge refrigerant pressure is equal to the target discharge refrigerant pressure (Yes in step S3), the process proceeds to the next step S5, and when it is determined that the discharge refrigerant pressure is not equal to the target discharge refrigerant pressure (step After the opening degree of the pressure reducing valve 7 (see FIG. 1) is corrected so that the discharge refrigerant pressure becomes equal to the target discharge refrigerant pressure (step S4), the process proceeds to the next step S5.

  In step S5, the heat pump unit controller 19 detects the outlet water temperature of the water-refrigerant heat exchanger 5 with the heat exchanger outlet water temperature sensor 17 (step S6), and this outlet water temperature is the target hot water described above. It is determined whether or not it is equal to the temperature (exit water temperature = target hot water temperature) (step S6). When it is determined that the outlet water temperature is equal to the target hot water temperature (Yes in step S6), the process proceeds to the next step S8, and when it is determined that the outlet water temperature is not equal to the target hot water temperature (in step S6). No), after correcting the rotational speed of the compressor 4 so that the outlet water temperature becomes equal to the target hot water temperature (step S7), the process proceeds to the next step S8.

  Thereafter, the heat pump unit control unit 19 determines whether or not the operation command is continued, and returns to step S1 when determining that the operation command is continued (Yes in step S8). And when it is judged that it is not continuing (No of step S8), the heat pump unit 1 stops an operation | movement and a predetermined boiling operation is complete | finished.

  If the incoming water temperature of the water flowing through the water-refrigerant heat exchanger rises or the target hot water temperature is set to a high value at a low outside air temperature, the discharge refrigerant pressure from the compressor and the discharge refrigerant temperature are acceptable. May rise to near the upper limit. In this case, the target rotational speed of the compressor 4 is set so as to increase the opening degree by controlling the pressure reducing valve, or to control the circulation pump to reduce the amount of water flowing through the water-refrigerant heat exchanger. Therefore, the discharge refrigerant pressure and the discharge refrigerant temperature exceed the allowable upper limit pressure calculated from the preset relationship between the compressor speed and the allowable upper limit pressure and the detected compressor rotation speed, and the allowable upper limit temperature. To avoid.

  According to the heat pump type water heater according to the embodiment of the present invention as described above, the following operational effects can be achieved.

  The target discharge refrigerant pressure is set to a pressure at which the coefficient of performance (hereinafter referred to as COP) of the heat pump unit is maximized based on the temperature of the water flowing into the water-refrigerant heat exchanger 5, the target hot water temperature, and the outside air temperature. The FIG. 3 shows the relationship between the discharge refrigerant pressure and the COP when the inlet water temperature is 9 ° C., the target hot water temperature is 65 ° C., and the outside air temperature is 7 ° C. (wet bulb temperature is 6 ° C.). The discharge refrigerant pressure that maximizes the COP is set in advance as the target discharge refrigerant pressure when the inlet water temperature, the target hot water temperature, and the outside air temperature are different with the same capacity. During the boiling operation, the heat pump unit is controlled by controlling the opening of the pressure reducing valve 7 so that the detected discharge refrigerant pressure is within the pressure range A centering on the target discharge refrigerant pressure shown in FIG. It is possible to drive with almost maximum performance.

  Compared with the case where the refrigerant amount adjusting means such as an accumulator is used, in the present embodiment, as shown in FIG. 3, the discharge refrigerant pressure at which the COP becomes maximum decreases, and the COP value at which the maximum COP increases. To do. Even if the refrigerant flowing out of the evaporator is heated by the refrigerant flowing out of the water-refrigerant heat exchanger by the internal heat exchanger, the temperature of the refrigerant flowing into the compressor becomes high and the discharge refrigerant pressure is low. This is because the temperature of the refrigerant discharged from the compressor can be increased. Further, in the pressure range A in the vicinity of the discharge refrigerant pressure at which the COP is maximum, the sensitivity of the discharge refrigerant pressure with respect to the COP can be relaxed according to this embodiment (that is, the peak of the discharge refrigerant pressure with respect to the COP can be made gentle). Can do). Therefore, the heat pump unit can be stably operated with almost maximum performance by the control method including the internal heat exchanger and the discharge refrigerant pressure as a target value.

  Similarly, when the temperature of the water flowing into the water-refrigerant heat exchanger 5 rises, the target discharge refrigerant pressure set value is determined from the relationship of the discharge refrigerant pressure at which the COP becomes maximum with respect to each incoming water temperature. The FIG. 4 shows, as an example, the relationship between the incoming water temperature, the target discharge refrigerant pressure, and the COP when the target hot water temperature is high. In this embodiment, instead of the refrigerant amount adjusting means such as the refrigerant receiver and the accumulator, by installing an internal heat exchanger for exchanging heat between the refrigerant flowing out of the water-refrigerant heat exchanger and the refrigerant flowing out of the evaporator, The target discharge refrigerant pressure can be set to a lower value than when the refrigerant amount adjusting means is provided. In addition, when the amount of water that occupies most of the boiling operation time is low, the COP can be increased, so that a stable boiling operation can be performed with less power consumption.

  As the incoming water temperature rises, the temperature of the refrigerant flowing out of the water-refrigerant heat exchanger 5 rises, and when the internal heat exchanger is not provided, the dryness of the refrigerant flowing into the evaporator decreases. The amount of refrigerant that can be held in the evaporator decreases, and the pressure on the high-pressure side in particular increases greatly so that the relationship between the refrigerant charge amount and the internal volume occupied by the refrigerant is satisfied.

  When refrigerant amount adjusting means such as a refrigerant receiver or an accumulator is installed, the excess refrigerant amount is stored to enable boiling operation when the incoming water temperature rises.

  In the present embodiment, an internal heat exchanger 6 for exchanging heat between the refrigerant on the high pressure side and the low pressure side of the refrigeration cycle is provided. The action of the internal heat exchanger 6 is that the refrigerant flowing out of the water-refrigerant heat exchanger 5 is cooled by the refrigerant flowing out of the evaporator 8 to reduce the dryness of the refrigerant at the inlet of the evaporator 8, thereby Is to increase the amount of refrigerant that can be held in When the incoming water temperature rises, the pressure reducing valve is opened to increase the amount of refrigerant moved from the high pressure side to the low pressure side. In other words, the opening of the pressure reducing valve is adjusted so as to move the refrigerant from the high pressure side to the low pressure side, thereby suppressing the decrease in the refrigerant holding amount on the low pressure side as the incoming water temperature rises. Here, as indicated by the alternate long and short dash line in FIG. 5, in this embodiment, when the incoming water temperature rises, the rotational speed of the compressor is increased to maintain the heating capacity. When the rotation speed of the compressor is increased, the moving amount of the refrigerant from the low pressure side to the high pressure side increases. On the other hand, if the heating capacity is not maintained when the incoming water temperature rises (for example, if the rotation speed of the compressor is not changed), the amount of refrigerant moving to the low pressure side increases by opening the pressure reducing valve. The refrigerant holding ratio on the low pressure side (mainly the evaporator) will increase. In this embodiment, when the incoming water temperature rises, the pressure reducing valve is opened, and the rotation speed of the compressor is increased to maintain the heating capacity. When the increase / decrease in the movement amount of the opposite refrigerant due to such control is added, the movement amount of the refrigerant from the low pressure side to the high pressure side due to the increase in the rotation speed of the compressor is changed from the high pressure side to the low pressure side by opening the pressure reducing valve. By slightly increasing the amount of movement of the refrigerant, as shown by the solid line in FIG. 5, the refrigerant holding ratio on the low pressure side (mainly the evaporator) slightly decreases as the incoming water temperature rises. Conversely, the refrigerant holding ratio on the high-pressure side increases as the incoming water temperature increases as shown by the solid line in FIG.

  FIG. 5 shows the relationship between the refrigerant holding ratio in the evaporator (= refrigerant holding quantity / refrigerant filling quantity in the evaporator) and the incoming water temperature when an internal heat exchanger is installed as in this embodiment. And the case where an internal heat exchanger is not installed is shown. As described above, as the incoming water temperature rises, the amount of refrigerant held by the evaporator decreases, but it can be seen that more refrigerant can be held by the evaporator as compared to the case where the internal heat exchanger is not set. Note that refrigerant amount adjusting means such as a refrigerant receiver and an accumulator may be installed in the refrigeration cycle, and these allow the boiling operation when the incoming water temperature rises by storing excess refrigerant amount. Even if these refrigerant receivers and accumulators are not provided, the evaporator performs substantially the same function.

  In addition, although the refrigerant is also held in the internal heat exchanger and the connection piping system necessary for the installation by installing the internal heat exchanger, as shown in FIG. 6, the internal heat exchanger and its connection piping system The amount of refrigerant held in the tank is as small as several percent of the refrigerant charge amount, and further decreases as the incoming water temperature rises. Therefore, it can be said that the excessive refrigerant amount generated when the incoming water temperature rises is mainly held in the evaporator.

  Another function of the internal heat exchanger 6 is that the refrigerant flowing out of the evaporator 8 is heated by the internal heat exchanger 6 with the refrigerant flowing out of the water-refrigerant heat exchanger 5, thereby flowing into the compressor. The purpose is to increase the temperature or dryness. When the compressor suction pressure and the discharge refrigerant temperature are the same, the discharge refrigerant pressure can be reduced and the target discharge refrigerant pressure that maximizes the COP is set to a lower value than when no internal heat exchanger is provided. Can do.

  Due to the action of the internal heat exchanger 6 and the operation of the pressure reducing valve 7 for controlling the target discharge refrigerant pressure, even when the incoming temperature of the water flowing through the water-refrigerant heat exchanger rises, the pressure rise on the high pressure side is kept low, The boiling operation can be performed stably while satisfying the required boiling temperature.

  In addition, when the incoming temperature of the water flowing through the water-refrigerant heat exchanger rises and the discharge refrigerant pressure from the compressor and the discharge refrigerant temperature rise to the vicinity of the allowable upper limit, While maintaining the target hot water temperature by controlling the opening of the pressure reducing valve to maintain the allowable upper limit pressure calculated from the relationship of the allowable upper limit pressure and reducing the amount of water flowing through the water-refrigerant heat exchanger The boiling operation can be performed stably.

  According to the heat pump type water heater of the present embodiment, it is not necessary to provide a refrigerant amount adjusting means such as a refrigerant receiver or an accumulator, but a refrigerant amount adjusting means is added in order to improve the driving capability or perform finer control. It does not prevent. Even when the refrigerant amount adjusting means is added to the present embodiment, the increase in the size of the device can be prevented or the increase in size can be significantly suppressed.

DESCRIPTION OF SYMBOLS 1 Heat pump unit 2 Hot water storage tank unit 3a, 3b Connection piping 4 Compressor 5 Water-refrigerant heat exchanger 6 Internal heat exchanger 7 Pressure reducing valve 8 Evaporator 9 Blower fan 10 Fan motor 11 Hot water storage tank 12 Water circulation pump 13 Water supply piping 14 Hot water supply Piping 15 Compressor discharge refrigerant pressure sensor 16 Water-refrigerant heat exchanger inlet water temperature sensor 17 Water-refrigerant heat exchanger outlet water temperature sensor 18 Outside air temperature sensor 19 Heat pump unit controller 20 Hot water tank unit controller

Claims (3)

A compressor that compresses the refrigerant, a water-refrigerant heat exchanger that heats water with a high-temperature and high-pressure refrigerant discharged from the compressor, and a low-temperature and low-pressure refrigerant that flows from the water-refrigerant heat exchanger through a pressure reducing valve. an evaporator back to the compressor refrigerant by air heat exchange, the water - and an internal heat exchanger the refrigerant flowing out from the refrigerant to the evaporator flowing from the refrigerant heat exchanger to heat exchange, the refrigerant amount In a heat pump type water heater that does not have an adjustment means ,
A heat pump type hot water heater that opens the pressure reducing valve to increase the rotational speed of the compressor when the temperature of the water flowing into the water-refrigerant heat exchanger rises . In the heat pump type water heater according to claim 1,
When the temperature of the water flowing into the water-refrigerant heat exchanger rises, if the pressure on the high pressure side rises to the vicinity of the allowable upper limit pressure, the pressure reducing valve is moved to move the refrigerant from the high pressure side to the low pressure side. While maintaining the boiling temperature by adjusting the opening and suppressing the decrease in the amount of refrigerant held on the low pressure side as the incoming water temperature rises, the flow rate of water flowing into the water-refrigerant heat exchanger is reduced. The heat pump water heater that suppresses the pressure rise on the high pressure side . The heat pump type hot water heater according to claim 1 or 2, wherein the refrigerant is carbon dioxide .