JP2013032888A - Heat pump and heat pump hot water supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat pump and a heat pump hot water supply device capable of performing a highly efficient heating operation with simple control.SOLUTION: In the heat pump of a vapor compression type, in which a closed circuit is formed by successively connecting a compression means 1 a radiator 2, a throttle means 3 and an evaporator 4, and the pressure of the refrigerant in the heat radiator 2 during operation exceeds a critical pressure, the radiator 2 is constituted of heat transfer pipes 2a, 2b, 2c which use the interior of the pipes as refrigerant channels and, on at least a part of the heat transfer pipes, a heat loss reduction means 5 for preventing the heat transfer from the part of the heat transfer pipes to other parts of the heat transfer pipe, is disposed on. Thereby, the heat radiation amount from the refrigerant in the radiator 2 to the material to be heated is secured, the temperature of the refrigerant and a specific enthalpy at a radiator 2 outlet can be kept low, the endothermic amount of the refrigerant on the evaporator 4 can be also kept and, consequently, the highly efficient heat pump operation can be performed.

Description

  The present invention relates to a vapor compression heat pump using carbon dioxide as a refrigerant. More specifically, the present invention relates to a heat pump used for hot water supply and a heat pump hot water supply apparatus using the heat pump.

  Conventionally, a vapor compression heat pump including a compressor, a radiator, a throttle means, and an evaporator and using carbon dioxide as a refrigerant is known. And this kind of heat pump is generally utilized for hot-water supply heating (for example, patent document 1). The conventional hot water supply apparatus using the heat pump includes a hot water storage tank and a circulation heating path that takes out the water in the hot water storage tank, heats it with a heat pump, and returns it to the hot water storage tank. That is, the cold water is taken out from below the hot water storage tank, the cold water is caused to flow to the radiator of the heat pump by the circulation pump, the heat is exchanged with the refrigerant compressed to a high temperature and high pressure by the compressor, and the water is heated, and the heated temperature becomes high. The water is returned to the hot water storage tank.

  This type of heat pump cycle using carbon dioxide as a refrigerant is a so-called transcritical cycle in which the pressure of the refrigerant exceeds the critical pressure on the high-pressure side. In such a transcritical cycle, the refrigerant does not condense in the radiator, but dissipates heat and the temperature decreases. Therefore, hot water supply that heats low-temperature water to a high temperature by heat-exchanging the low-temperature water taken out from below the hot water storage tank and the high-temperature and high-pressure refrigerant discharged from the compressor in a counter-current manner in the radiator. Highly efficient heating is possible in the application.

  In addition, an attempt has been made to eliminate the above-mentioned circulation heating path, and instead provide a heat radiator inside the hot water storage tank to directly exchange heat between the refrigerant flowing through the heat radiator and the water stored in the hot water storage tank. (For example, Patent Document 2). By adopting such a configuration, it is not necessary to control the flow rate of the water flowing through the circulating water path, the power consumption of the circulating pump for flowing water through the circulating heating path is unnecessary, and the flow through the circulating heating path The effect of eliminating the problem of water freezing can be expected.

JP 2002-243274 A JP 2006-153307 A

  By the way, in the above-mentioned transcritical cycle, the refrigerant does not condense in the radiator, and the temperature is reduced while radiating heat. Therefore, the difference between the refrigerant temperature on the upstream side of the refrigerant flow path and the refrigerant temperature on the downstream side of the radiator is larger than that in a heat pump cycle that uses a fluorocarbon-based refrigerant with refrigerant condensation in the radiator. In other words, in a heat pump cycle using a fluorocarbon refrigerant that condenses refrigerant during the heat release process of the refrigerant on the high-pressure side, the refrigerant flowing through the radiator condenses and dissipates at a constant temperature, so the temperature of the refrigerant inside the radiator Although the difference is small, in the above-mentioned transcritical cycle, the refrigerant temperature decreases as the heat is released, so the refrigerant temperature difference inside the radiator is large.

  Thus, in the transcritical cycle, since the refrigerant temperature difference inside the radiator is large, for example, when the upstream side refrigerant pipe and the downstream side refrigerant pipe constituting the radiator are in contact with each other, or when the interval between the refrigerant pipes is narrow In this case, heat transfer occurs between the refrigerant tubes, and heat is transferred from the refrigerant on the upstream side of the radiator to the refrigerant on the downstream side. When the heat of the refrigerant on the upstream side of the radiator is transmitted to the downstream side of the radiator, the refrigerant temperature at the outlet of the radiator increases and the specific enthalpy increases. As a result, the refrigerant passes through the throttle means to the evaporator. As a result, the specific enthalpy of the flowing refrigerant increases, the heat absorption amount and the heat dissipation amount of the heat pump decrease, and the efficiency of the heat pump significantly decreases.

  In particular, when the heat pump radiator is provided in the hot water storage tank as in the prior art described in Patent Document 2, the heat exchange between the refrigerant and water does not necessarily flow countercurrently. There is also a problem that the heat of the refrigerant on the side is transferred to the water in the hot water storage tank and retransmitted to the refrigerant on the downstream side of the radiator via the water. As a result, the refrigerant temperature at the outlet of the radiator rises, the specific enthalpy of the refrigerant flowing into the evaporator increases, and the capacity and efficiency of the heat pump are significantly reduced.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a heat pump and a heat pump hot water supply device that can perform a heating operation with simple control and high efficiency.

  In the heat pump of the first invention, the compression means, the radiator, the throttle means, and the evaporator are sequentially connected to form a closed circuit, and the vapor compression in which the pressure of the refrigerant in the radiator during operation exceeds the critical pressure of the refrigerant In the heat pump of the type, the radiator is composed of a heat transfer tube having a pipe as a refrigerant flow path, and heat loss reducing means for preventing heat transfer from at least a portion of the heat transfer tube to the other portion of the heat transfer tube Is provided.

  A heat pump according to a second aspect of the present invention is the heat pump according to the first aspect, wherein the radiator is upstream of a folded portion provided in a substantially central portion of the entire length of the refrigerant flow path in the radiator and substantially parallel to the flow direction. A heat loss that includes a side heat transfer tube and a downstream heat transfer tube, and prevents heat transfer from the upstream heat transfer tube to the downstream heat transfer tube at least at a part between the outer surface of the upstream heat transfer tube and the downstream heat transfer tube A reduction means is provided.

  A heat pump according to a third aspect of the present invention is the heat pump according to any one of the first or second aspects of the present invention, comprising a foamed resin heat insulating material that is in close contact with the outer surface of the heat transfer tube as the heat loss reducing means. .

  A heat pump according to a fourth aspect of the invention is the heat pump according to any one of the first to third aspects of the invention, comprising a heat transfer tube holding member that maintains the interval between the heat transfer tubes within a predetermined range as the heat loss reducing means. It is characterized by that.

  A heat pump hot water supply apparatus according to a fifth aspect of the present invention includes the heat pump according to any one of the first to fourth aspects of the present invention and a hot water storage tank for storing water, and the heat transfer pipe of the radiator is inserted and disposed inside the hot water storage tank. The heat exchanger tube is configured to perform heat exchange between the refrigerant in the heat transfer tube and the water in the hot water storage tank.

  According to the heat pump of the first invention, the radiator is configured by a heat transfer tube having a pipe as a refrigerant flow path, and prevents heat transfer from at least a portion of the heat transfer tube to the other portion of the heat transfer tube. Since the heat loss reducing means is provided, it is possible to prevent the heat pump from deteriorating due to heat transferred from the refrigerant upstream of the radiator to the refrigerant downstream of the radiator. That is, by providing the heat loss reducing means, the heat is transferred from the refrigerant upstream of the radiator to the refrigerant downstream of the radiator, thereby increasing the temperature and specific enthalpy of the refrigerant at the radiator outlet, and releasing the heat pump. Decrease in the amount of heat and endothermic amount can be prevented. As a result, the amount of heat released from the refrigerant in the radiator to the object to be heated can be secured, the refrigerant temperature and specific enthalpy at the outlet of the radiator can be kept low, and the heat absorption amount of the refrigerant in the evaporator can also be maintained. An efficient heat pump operation can be performed.

  According to the heat pump of the second invention, the radiator includes a folded portion provided at a substantially central portion of the entire length of the refrigerant flow path in the radiator, an upstream heat transfer tube and a downstream that are substantially parallel to each other and facing the flow direction. And a heat loss reducing means for preventing heat transfer from the upstream heat transfer tube to the downstream heat transfer tube at least partially between the outer surfaces of the upstream heat transfer tube and the downstream heat transfer tube. Therefore, it is possible to prevent the heat pump performance from being reduced due to heat transfer from the refrigerant on the upstream side of the radiator to the refrigerant on the downstream side of the radiator, and it is possible to easily process and assemble the radiator. In addition, when installing a radiator to a container or the like that accommodates an object to be heated, the radiator of the present invention is substantially parallel to the folded portion provided at the substantially central portion of the entire length of the refrigerant flow path in the radiator and Since the upstream side heat transfer tube and the downstream side heat transfer tube are opposed to each other in the flow direction, it can be easily inserted and arranged from a relatively small diameter hole.

  According to the heat pump of the third invention, the heat loss reducing means includes the foamed resin heat insulating material that is in close contact with the outer surface of the heat transfer tube, so that the heat loss reducing means can be easily processed and attached. .

  According to the heat pump of the fourth aspect of the present invention, since the heat transfer tube holding member that maintains the interval between the heat transfer tubes within a predetermined range is provided as the heat loss reducing means, contact between the heat transfer tubes can be prevented. The heat transfer due to the heat transfer tube outer surfaces coming into contact with each other can be prevented. Moreover, since the predetermined gap is provided between the heat transfer tubes, it is possible to prevent the heat transferred from the upstream heat transfer tube to the object to be heated from being retransmitted to the refrigerant in the downstream heat transfer tube.

  According to the heat pump hot water supply apparatus of the fifth aspect of the invention, the apparatus includes a hot water storage tank for storing water, and the heat transfer pipe of the radiator is inserted and disposed inside the hot water storage tank, and the refrigerant in the heat transfer pipe and the water in the hot water storage tank Therefore, there is no need for a circulation heating path or a heating circulation pump that takes out the water in the hot water storage tank and heats it and then returns it to the hot water storage tank. Therefore, the power consumption of the circulation pump is eliminated, the flow rate control of the water flowing through the circulation heating path becomes unnecessary, and the means for preventing the water inside the circulation heating path from freezing is also eliminated. In particular, in the heat pump hot water supply apparatus of the present invention, the heat loss reducing means for preventing heat transfer from the refrigerant on the upstream side of the radiator to the refrigerant on the downstream side of the radiator is provided, so the radiator is provided inside the hot water storage tank. In the configuration, it is possible to keep the refrigerant temperature and specific enthalpy at the radiator outlet low, increase the heat radiation amount and heat absorption amount of the heat pump, and perform highly efficient operation.

It is a schematic block diagram of the heat pump hot-water supply apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows the structure of the heat radiator which concerns on embodiment of this invention. It is the temperature and enthalpy diagram which showed the heat pump cycle of this invention. It is an external view which shows the bending shape example of the heat radiator which concerns on embodiment of this invention. It is sectional drawing which shows the structure of the hot water storage tank which concerns on embodiment of this invention. It is explanatory drawing which shows the structure of the heat radiator which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the structure of the heat exchanger tube holding member which concerns on the 2nd Embodiment of this invention.

  Hereinafter, a heat pump and a heat pump hot water supply apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a heat pump hot water supply apparatus according to an embodiment of the present invention. The heat pump hot water supply apparatus according to this embodiment includes a heat pump 10 and a hot water storage tank 20.

  The heat pump 10 includes a compressor 1 as a compression means, a radiator 2, an expansion valve 3 as a throttle means, and an evaporator 4, and is closed by a refrigerant pipe so that the refrigerant flows in order through the respective elements. A circuit (refrigerant circuit) is formed. The compressor 1, the expansion valve 3, and the evaporator 4 constituting the heat pump 10 are housed and unitized in one housing (heat pump unit 10a), while the radiator 2 is provided outside the heat pump unit 10a. It has been. The heat pump 10 is filled with carbon dioxide (R744) as a refrigerant. Normally, the heat pump 10 and the hot water storage tank 20 are connected at a site where a hot water supply apparatus is installed by a method described later. However, the heat pump 10 is filled with a refrigerant in the factory, and the heat pump 10 is in a state in which the refrigerant is sealed. Shipped from the factory.

  The compressor 1 is for compressing a low-pressure refrigerant into a high-pressure state. In the heat pump according to the present embodiment, since carbon dioxide is used as the refrigerant, the pressure of the refrigerant discharged from the compressor 1 exceeds the critical pressure of the refrigerant. The compressor 1 is a rotary type two-stage compression type including a first-stage compression element 1a and a second-stage compression element 1b. By adopting the two-stage compression method, the pressure ratio of the compression elements at each stage can be reduced, and the refrigerant can be compressed to a high pressure with high efficiency. As the compressor 1, other known compressors such as a scroll type, a reciprocating type, and a screw type can be used.

  The radiator 2 is a heat exchanger for performing heat exchange between the refrigerant and water that is an object to be heated. Since the refrigerant pressure inside the radiator 2 exceeds the critical pressure, the radiator 2 acts as a gas cooler. That is, the refrigerant does not condense inside the refrigerant flow path of the radiator 2, and its temperature decreases as the heat is radiated to the water and cooled. The structure of the radiator 2 is shown in FIG. The radiator 2 of the present embodiment is composed of a single heat transfer tube (the total length is about 10 m and the outer diameter is about 5 mm) with the inside of the tube as a refrigerant flow path. A portion that becomes / 2 forms a folded portion 2c that is bent into a substantially U shape. The upstream heat transfer tube 2a, which is the upstream side of the folded portion 2c, and the downstream heat transfer tube 2b, which is the downstream side, are substantially parallel to each other and are configured such that the refrigerant flow directions oppose each other.

  In the vicinity of the refrigerant inlet portion and the refrigerant outlet portion of the radiator 2, a fixing fitting 7 for holding the radiator 2 and fixing it to the hot water storage tank 20 is provided. Moreover, the heat exchanger tube which comprises the heat radiator 2 has the double tube structure as shown in FIG.2 (b). The inner sides of the inner pipes 2aI and 2bI are refrigerant flow paths, and the outer sides of the outer pipes 2aO and 2bO are water sides. The gap between the inner pipes 2aI, 2bI and the outer pipes 2aO, 2bO communicates with the outside air side outside the hot water storage tank 20. Thereby, even if an accident such as breakage of the inner pipes 2aI and 2bI occurs, it is possible to prevent the refrigerant and the refrigerating machine oil from entering the hot water storage tank 20.

  The heat transfer tube of the radiator 2 is an annealed copper tube, and has flexibility when the heat pump 10 is shipped, that is, at least before being inserted into the hot water storage tank 20. When the heat pump 10 is shipped, the heat transfer tube shape of the radiator 2 is wound in a coil shape. Thereby, shipping conveyance of the heat pump 10 and the assembly | attachment of the heat radiator 2 to the hot water storage tank 20 can be performed easily. That is, at the site where the hot water supply apparatus is installed, the heat transfer tube of the radiator 2 wound in a coil shape is appropriately extended so that it can be easily inserted into the hot water storage tank 20, and Can be easily inserted inside. The overall shape of the heat transfer tube of the radiator 2 after being inserted into the hot water storage tank 20 is not limited to a linear shape, but a spiral shape as shown in FIG. Any bending shape such as a meandering shape may be used. Also in this case, the upstream heat transfer tube 2a and the downstream heat transfer tube 2b are in a substantially parallel state.

  Between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b of the radiator 2, a heat insulating material 5 as heat loss reducing means is disposed so as to be in close contact with the heat transfer tubes 2a and 2b. The heat insulating material 5 is a foamed resin-based heat insulating material, for example, a foam material made of polyurethane (PUR), polystyrene (PS), polyolefin (PP, PE), chloroprene (CR), silicon (SI) or the like. Can be adopted. Moreover, the heat insulating material 5 is inserted in the space | interval of the heat exchanger tubes 2a and 2b in the state compressed moderately, and is closely_contact | adhered to the outer surface of each heat exchanger tube by the elastic repulsive force. In this way, heat transfer between the heat transfer tubes 2a and 2b is prevented by closely inserting the heat insulating material 5 between the upstream heat transfer tube 2a that becomes high temperature and the downstream heat transfer tube 2b that becomes low temperature during operation. Therefore, the heat pump can be operated with high efficiency.

  Moreover, you may adhere and fix the heat insulating material 5 to the surface of either one of the heat exchanger tubes 2a or 2b as needed. By adhering the heat insulating material 5 to the surface of one heat transfer tube, it is possible to very easily assemble the radiator 2 and prevent the heat insulating material 5 from being displaced, thereby further enhancing the heat loss reduction effect. it can. It is also possible to bond the heat insulating material 5 to the surface of both the heat transfer tubes 2a and 2b. Furthermore, the heat transfer tubes 2a and 2b after the heat insulating material 5 is sandwiched can be fastened and fixed from the outside with a so-called binding band or the like. By these methods, it is possible to prevent the heat insulating material 5 from being displaced or dropped off, so that the processing and assembly of the radiator 2 are facilitated, and the operation of incorporating the radiator 2 into the hot water storage tank 20 can be easily performed. At the same time, the heat loss reducing effect of the heat insulating material 5 can be reliably exhibited.

  In addition, the heat radiator 2 which concerns on this embodiment is made to provide the heat insulating material 5 only in the part near the fixing metal fitting 7, ie, the part with a large temperature difference of the heat exchanger tubes 2a and 2b. Thus, even if the heat insulating material 5 is not provided in the whole heat exchanger tubes 2a and 2b, the heat loss reduction effect can be sufficiently expected. In particular, since the temperature difference between the heat transfer tubes 2a and 2b is small in the vicinity of the folded portion 2c, the heat loss reduction effect of the heat insulating material 5 is small, and the heat transfer area with water can be secured larger if the heat insulating material 5 is not attached. Will be advantageous.

  The fixing bracket 7 has a so-called pipe flange shape including holes 7a and 7b for inserting and holding the upstream heat transfer tube 2a and the downstream heat transfer tube 2b, and a plurality of holes 7c for fixing screws. Yes. The heat transfer tubes 2 a and 2 b of the radiator 2 are joined by brazing after being inserted into the holes 7 a and 7 b of the fixture 7. The radiator 2 to which the fixing bracket 7 is joined is inserted into the hot water storage tank 20 and fixed and held by the fixing bracket 7. That is, a screw is inserted into the hole 7 c of the fixing metal 7 and is fixed to the radiator insertion port 23 of the hot water storage tank 20 with a screw. By adopting such a configuration, the operation of incorporating the radiator 2 into the hot water storage tank 20 can be easily performed. For example, the heat pump of the present invention can be easily additionally installed in an existing hot water storage tank. it can. In addition, the fixing bracket 7 and the radiator insertion port 23 are fixed by using a fixing bracket, a fixing nut, or the like instead of directly fixing the flange-shaped fixing bracket 7 with screws. Also good.

  The fixing bracket 7 and the heat transfer tubes 2a and 2b are fixed by brazing. However, a sealing method using a bite type metal seal ring, a method of sealing and fixing with a seal fixing member such as an O-ring, etc. It is also possible to employ a known method for hermetically holding the tube material. The method of brazing and fixing the heat transfer tubes 2a, 2b to the fixing bracket 7 as in the present embodiment is capable of reliable sealing, is less likely to leak, and the radiator 2 can be firmly fixed. This is advantageous in that there is little risk of the radiator 2 falling off.

  The expansion valve 3 as a throttle means is for reducing the pressure of the refrigerant, which has radiated water with respect to the water by the radiator 2 and having a low temperature, to an evaporation pressure by expansion of the throttle. As the throttle means, a capillary tube, a temperature type expansion valve, an electric expansion valve, or the like can be adopted. In the heat pump 10 according to the present embodiment, an electric expansion valve is used. And the opening degree of the expansion valve 3 is controlled so that the temperature of the refrigerant flowing into the radiator 2 becomes a predetermined value, that is, a temperature suitable for heating water.

  The evaporator 4 is a heat exchanger for absorbing heat from the atmosphere due to the evaporation of the refrigerant, and employs a fin-and-tube heat exchanger. The evaporator 4 includes a fan 4f for supplying air that exchanges heat with the refrigerant. In the evaporator 4, the refrigerant takes heat from the air supplied by the fan 4f and the liquid phase portion evaporates.

  Although not shown, it is also possible to provide an accumulator on a pipe connected from the outlet of the evaporator 4 to the compressor 1. The accumulator is for preventing the liquid refrigerant from being sucked into the compressor 1, and has a function of performing gas-liquid separation inside and temporarily storing the liquid refrigerant. Thereby, damage to the compressor 1 due to liquid compression can be prevented, and the durability reliability of the heat pump is improved.

  Further, if necessary, an internal heat exchanger (see FIG. 3) that exchanges heat between the high-pressure liquid refrigerant flowing to the expansion valve 3 and the low-pressure refrigerant flowing out of the evaporator 4 to cool the high-pressure refrigerant and heat the low-pressure refrigerant. (Not shown) can also be provided. In this case, since the low-pressure refrigerant is superheated by the internal heat exchanger, the effect of preventing the compressor 1 from being wet-compressed can be expected as in the accumulator. In addition, by adopting the internal heat exchanger, it is possible to secure a large number of two-phase refrigerant regions having a high heat transfer rate inside the evaporator 4, so that the heat transfer performance of the evaporator 4 is improved and the performance of the heat pump is improved. it can.

  The hot water storage tank 20 stores hot water (hot water) therein. The hot water storage tank 20 according to the present embodiment includes a can body 20a as a container for storing water, a heat insulating material 20c provided on the outer periphery of the can body 20a, and an exterior 20b provided on the outside thereof. The hot water storage tank 20 includes a water supply inlet 21 for introducing water into the tank, a hot water supply outlet 22 for supplying hot water, and a radiator insertion port 23 for inserting and fixing the radiator 2.

  The can 20a is a stainless steel container that stores hot water. The heat insulating material 20c prevents heat dissipation from the can body 20a and improves the efficiency of the hot water supply apparatus. For example, a foamed heat insulating material such as urethane foam and a fiber heat insulating material such as glass wool can be adopted. In the hot water storage tank 20 according to the present embodiment, urethane foam is used as the heat insulating material 20c, and after the outer body 20b is assembled to the can body 20a, the heat insulating material is injected by injecting the foam material between the can body 20a and the outer body 20b. 20c is formed. The exterior 20b is for holding the heat insulating material 20c, and in this embodiment, iron (rolled steel plate) is used as a material.

  The water supply inlet 21 is for introducing water into the hot water storage tank 20, and has a tubular shape inserted into the hot water storage tank 20 from above. The upper end portion (outside of the can) of the water supply inlet 21 has a joint shape (for example, a pipe taper screw) so that a water supply pipe can be connected. On the other hand, the lower end (inside of the can) of the water supply inlet 21 is inserted and opened to the lower side of the hot water storage tank 20. Thereby, the low temperature water supply can be introduced below the can 20a without disturbing the temperature stratification of the hot water (water) stored in the hot water storage tank 20, and the hot and cold water mixing in the hot water storage tank 20 is possible. The heat loss due to can be reduced.

  As shown in FIG. 5, the water supply inlet 21 may be provided below the hot water storage tank 20 (for example, the bottom surface of the can body 20a). Even with such a configuration, low-temperature supply water can be supplied from below the tank, and heat loss due to mixing of cold and hot water in the hot water storage tank 20 can be reduced. The method of providing the water supply inlet 21 above the hot water storage tank 20 as shown in FIG. 1 is excellent in that the hot water storage tank 20 that is heavy in weight can be installed and fixed easily and can be installed in a limited space. The method of providing the water supply inlet 21 below the hot water storage tank 20 as shown in FIG. 5 is excellent in that the pipe portion inserted into the hot water storage tank 20 can be shortened.

  The hot water supply outlet 22 is for sending out the hot water stored in the hot water storage tank 20 to the hot water use side, and has a tubular shape inserted into the hot water storage tank 20 from above. As with the water supply inlet 21, the upper end portion (outside of the can) of the hot water supply outlet 22 has a joint shape so that a hot water supply pipe can be connected. The lower end (inside of the can) of the hot water outlet 22 is open inside the hot water storage tank 20, but the opening position is above the hot water storage tank 20, unlike the hot water inlet 21. That is, the length of the pipe portion inserted into the hot water storage tank 20 is different between the water supply inlet 21 and the hot water supply outlet 22, and the hot water supply outlet 22 is shorter than the water supply inlet 21. Thereby, the hot water stored in the upper part of the hot water storage tank 20 can be supplied to the hot water use side.

  The radiator insert port 23 is for inserting the radiator 2 into the hot water storage tank 20 and fixing and holding the radiator 2. The radiator insertion port 23 includes a hole communicating with the inside of the can body 20 a for inserting the radiator 2 and a screw hole for screwing the fixing bracket 7 attached to the radiator 2. Since the fixing bracket 7 has a piping flange shape, the radiator insertion port 23 also has a flange-like joint shape that matches this. In order to maintain the airtightness of the hot water storage tank 20, a gasket is sandwiched between the joint surface between the fixing metal 7 and the radiator insertion port 23. As described above, other fixing methods can be employed for fixing the fixing bracket 7 and the radiator insertion port 23.

  The radiator insertion port 23 is provided on the upper surface of the hot water storage tank 20. Therefore, the radiator 2 is inserted from above the hot water storage tank 20. Thus, the method of providing the radiator insertion port 23 on the upper surface of the hot water storage tank 20 is excellent in that the installation space for the hot water storage tank 20 can be reduced.

  Further, as shown in FIG. 5, the radiator insertion port 23 can be provided below the hot water storage tank 20. By providing the radiator insertion port 23 below the hot water storage tank 20 in this manner, the refrigerant at the outlet side of the heat radiator 2 can be cooled by water having a relatively low temperature in the hot water storage tank 20. It becomes possible to reduce the specific enthalpy of the refrigerant. As a result, the heating performance of the heat pump can be further improved.

  Next, the operation of the heat pump according to the first embodiment will be described.

  FIG. 3 is a temperature-specific enthalpy diagram showing the heat pump cycle of the heat pump according to the present invention. The horizontal axis represents the specific enthalpy (kJ / kg) of the refrigerant, the vertical axis represents the refrigerant temperature (° C.), the symbol SL represents the saturated liquid line of the refrigerant, and SV represents the saturated vapor line.

  In this heat pump cycle, the low-temperature refrigerant vapor shown in the state a in FIG. 3 is sucked from the suction port of the compressor 1, compressed by the compressor 1, and discharged as a high-temperature and high-pressure refrigerant (state b). In this embodiment, since carbon dioxide is used as the refrigerant of the heat pump, the pressure of the refrigerant discharged from the compressor 1 exceeds the critical pressure as shown in state b in FIG. In the heat pump according to the present invention, the opening degree of the expansion valve 3 is controlled so that the temperature Tb of the refrigerant discharged from the compressor 1 becomes a predetermined value. Accordingly, the temperature Tb of the refrigerant at the inlet of the radiator 2 is maintained at a suitable value for heating water, so that highly efficient heat pump operation can be performed.

  The refrigerant discharged from the compressor 1 flows into the radiator 2 and is cooled by exchanging heat with the water in the hot water storage tank 20. As shown in FIG. 3, since the pressure of the refrigerant in the radiator 2 exceeds the critical pressure, the refrigerant cooled by the radiator 2 does not condense and its temperature decreases as it is cooled. The refrigerant cooled by the radiator 2 is indicated by a state c. The water heated by the heat radiation of the refrigerant in the radiator 2 is stored above the hot water storage tank 20 and used for hot water supply.

  The refrigerant that has exited the radiator 2 passes through the expansion valve 3, and is subjected to throttle expansion (equal enthalpy expansion) and flows to the evaporator 4. The refrigerant flowing into the evaporator 4 is represented by a state d and is in a low-pressure gas-liquid two-phase state. As described above, the opening degree of the expansion valve 3 is controlled so that the temperature Tb of the refrigerant discharged from the compressor 1 becomes a predetermined value.

  The refrigerant that has flowed into the evaporator 4 exchanges heat with the air supplied by the fan 4f in the evaporator 4, absorbs heat from the air, and the liquid phase portion evaporates. At the outlet of the evaporator 4, the refrigerant is a slightly superheated vapor and is represented by state a.

  The refrigerant that has flowed out of the evaporator 4 flows to the compressor 1. In addition, when the accumulator (not shown) is provided on the pipe | tube connected to the compressor 1 from the exit of the evaporator 4, the refrigerant | coolant which flowed out from the evaporator 4 was reliably gas-liquid-separated in this accumulator. Thereafter, only the vapor refrigerant is sucked into the compressor 1. Then, the refrigerant is compressed again in the compressor 1. As described above, the heat pump cycle operates continuously, absorbs heat from the outside air in the evaporator 4, and dissipates heat in the radiator 2 to heat water. And the water heated in the heat radiator 2 is utilized for a hot-water supply use.

  When an internal heat exchanger (not shown) is provided, in the internal heat exchanger, the high-pressure and low-temperature refrigerant flowing out of the radiator 2 and the low-pressure and low-temperature refrigerant exiting the evaporator 4 Heat exchange is performed between them, the high-pressure refrigerant is cooled, and the low-pressure refrigerant is heated. In this case, since the high-pressure refrigerant is cooled in the internal heat exchanger, the specific enthalpy of the refrigerant flowing into the evaporator 4 is reduced, and a large number of two-phase refrigerant regions having a high heat transfer coefficient can be secured inside the evaporator 4. As a result, the heat transfer performance of the evaporator 4 is improved, and the cycle performance can be improved. Further, since the low-pressure refrigerant is superheated in the internal heat exchanger, the compressor 1 can be prevented from being wet-compressed.

  By the way, in the transcritical cycle in which the refrigerant pressure on the high pressure side exceeds the critical pressure as in the heat pump of the present invention, the refrigerant does not condense inside the radiator 2 and its temperature decreases as it radiates heat. The refrigerant temperature difference increases. That is, there is a large difference between the temperature Tb of the refrigerant flowing into the radiator 2 indicated by the state b in FIG. 3 and the refrigerant temperature Tc at the outlet of the radiator 2 indicated by the state c, and also inside the radiator 2. There is a temperature difference in the refrigerant flow direction. Thus, the large refrigerant temperature difference in the radiator 2 is a point that is greatly different from a heat pump using a CFC-based refrigerant that radiates heat while condensing at a constant temperature, and is a feature of the transcritical cycle heat pump. .

  As described above, in the transcritical cycle, since the temperature difference in the flow direction of the refrigerant in the radiator 2 is large, the heat transfer tubes 2a and 2b constituting the radiator 2 are in contact with each other, When the interval between the heat sinks 2b is narrow, heat is transferred from the upstream heat transfer tube 2a of the radiator 2 having a high temperature to the downstream heat transfer tube 2b having a low temperature, and the refrigerant on the upstream side of the radiator 2 is cooled, and the downstream side The refrigerant is heated. If it does so, temperature Tc of the refrigerant | coolant which leaves the heat radiator 2 and flows into the expansion valve 3 will become high, and specific enthalpy will become large. When this is seen in the cycle shown in FIG. 3, the refrigerant flowing to the expansion valve 3 moves from the point indicated by the state c in the upper right direction (on the isobaric line of the diagram) to the state c2, and its temperature is , Tc rises to Tc2. Then, the state of the refrigerant at the evaporator inlet changes from the state d to the state d2, and the specific enthalpy increases by an amount corresponding to dh. As a result, the amount of heat transferred from the refrigerant to water in the radiator 2 is reduced (corresponding to dh), the amount of heat absorbed by the refrigerant in the evaporator 4 is also reduced, and the capacity and efficiency of the heat pump are significantly reduced.

  In particular, when the radiator 2 is provided in the hot water storage tank 20 and the water side is not forcedly circulated as in the heat pump hot water supply apparatus of the present invention, the water side flow becomes natural convection by heating, It is difficult to exchange heat with water countercurrently, so that problems due to heat transfer between the heat transfer tubes 2a and 2b are likely to occur. That is, the water around the heat transfer tube 2a is heated by the refrigerant in the upstream heat transfer tube 2a having a high refrigerant temperature, and the heated water flows slowly by natural convection, so that the heat of the water is transferred to the upstream heat transfer tube 2a. In parallel with this, the refrigerant is retransmitted to the refrigerant in the downstream heat transfer tube 2b having a low temperature. The heat loss due to heat transfer between the heat transfer tubes is remarkable in the vicinity of the radiator insertion port 23 where the temperature difference between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b becomes large.

  In the heat pump according to the present embodiment, as described above, the heat insulating material 5 is provided as the heat loss reducing means between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b. Since heat transfer to the heat pipe 2b can be prevented and the temperature and specific enthalpy of the refrigerant at the outlet of the radiator 2 can be kept low, the heating capacity and heating efficiency of the heat pump can be maintained high. Therefore, it is possible to perform a highly efficient hot water supply operation with simple control without requiring water flow rate control or the like according to the boiling temperature unlike the hot water circulation system.

  Next, a heat pump and a heat pump hot water supply apparatus according to a second embodiment which is another embodiment of the present invention will be described in detail with reference to the drawings.

  The heat pump according to the second embodiment includes a heat transfer tube holding member 30 as heat loss reducing means. This point is different from the heat pump according to the first embodiment. About another structure, since it has the same effect | action and effect with the same structure as the heat pump which concerns on 1st Embodiment already demonstrated, the description is abbreviate | omitted and only the difference with 1st Embodiment is demonstrated in detail. explain.

  Drawing 6 is an explanatory view showing radiator 2 which is a component of the heat pump concerning a 2nd embodiment, and its assembly structure. In FIG. 6, the same number is attached | subjected about the component which has the same or similar effect | action and effect as the heat pump which concerns on 1st Embodiment. A heat transfer tube holding member 30 is attached to the radiator 2 according to this embodiment as heat loss reducing means. The heat transfer tube holding member 30 is provided between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b, and supports and fixes the tubes to each other in the form described later. As a result, contact between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b can be prevented, and the distance between the tubes can be maintained within a predetermined range (in this embodiment, the distance between the axes is about 15 mm). Heat transfer between 2a and 2b can be prevented.

  FIG. 7 is an explanatory view showing the structure of the heat transfer tube holding member 30. Fig.7 (a) is the figure which looked at the heat exchanger tube holding member 30 from the axial direction of heat exchanger tube 2a, 2b with which this is mounted | worn, and FIG.7 (b) is seen from the side surface. FIG. 7C shows a state where the heat transfer tubes 2a and 2b are attached to the heat transfer tube holding member 30. FIG. The heat transfer tube holding member 30 includes two heat transfer tube holding portions 31 that hold the heat transfer tubes 2a and 2b with a predetermined interval therebetween. The shape of the heat transfer tube holding portion 31 is an arcuate concave shape that contacts the outer surfaces of the heat transfer tubes 2a and 2b, and the inner diameter of the arc surface is the same as or slightly smaller than the outer diameter of the heat transfer tubes 2a and 2b. The dimension of the opening 32 is smaller than the outer diameter of the heat transfer tubes 2a and 2b.

  The material of the heat transfer tube holding member 30 is a resin material having water resistance and heat resistance, and has a slight flexibility. For example, materials such as polyethylene (PE), polypropylene (PP), fluororesin (PTFE), polyamide (PA), and polyacetal (POM) can be employed. The heat transfer tubes 2 a and 2 b are mounted from the opening 32 of the heat transfer tube holding portion 31, and the heat transfer tubes 2 a and 2 b mounted on the heat transfer tube holding portion 31 are pressed so as to be sandwiched by the elastic repulsion force of the heat transfer tube holding member 30. The support is fixed. By adopting the heat transfer tube holding member 30 in such a form, the heat transfer tubes 2a and 2b can be easily attached to the heat transfer tube holding member 30, so that the assembly work efficiency of the radiator 2 can be improved.

  Further, the heat transfer tube holding member 30 fits inside a virtual circle G (virtual cylinder G) having a minimum diameter that is inscribed in the outer surfaces of the heat transfer tubes 2a and 2b in a state where the heat transfer tubes 2a and 2b are mounted. It has a shape. Since the heat transfer tube holding member 30 after mounting the heat transfer tubes 2a and 2b does not have a portion that protrudes outward from the virtual circle G in this way, it is easy to insert the radiator 2 from the radiator insertion port 23 of the hot water storage tank 20. Can be done. In the present embodiment, the virtual circle G has a diameter of about 20 mm.

  As described above, since the heat transfer tubes 2a and 2b are held by the elastic repulsion force of the heat transfer tube holding member 30, there is no need for a separate fixture or the like for supporting the heat transfer tubes 2a and 2b. After the heat transfer tubes 2a and 2b are attached to 30, the heat transfer tubes 2a and 2b may be fastened and fixed from the outside by a so-called binding band or the like (not shown). Thereby, since the drop-off of the heat transfer tube holding member 30 can be prevented, the effect of reducing the heat loss can be surely exhibited.

  As described above, the heat pump according to the present embodiment prevents contact between the heat transfer tubes 2a and 2b between the upstream heat transfer tube 2a and the downstream heat transfer tube 2b, and provides a predetermined inter-tube distance. Since the heat transfer tube holding member 30 that supports and fixes the heat tubes 2a and 2b is provided, heat transfer from the upstream heat transfer tube 2a to the downstream heat transfer tube 2b can be reduced. That is, because the upstream heat transfer tube 2a and the downstream heat transfer tube 2b are separated by a predetermined distance, the amount of heat transfer due to heat conduction decreases, and the temperature of the water around the outer surface of the upstream heat transfer tube 2a increases. However, since the high-temperature water after the heating is transported by natural convection and is replaced or mixed with the surrounding water, the temperature of the water around the outer surface of the downstream heat transfer tube 2b can be prevented from increasing, Heat transfer from the water to the refrigerant inside the downstream heat transfer tube 2b can be prevented. As a result, since the temperature and specific enthalpy of the refrigerant at the outlet of the radiator 2 can be kept low, a highly efficient heat pump heating operation can be performed.

  Moreover, in the heat pump which concerns on this embodiment, since the area which the heat exchanger tube holding member 30 and the heat exchanger tubes 2a and 2b contact is small compared with the case where the heat insulating material 5 which concerns on 1st Embodiment is provided, the heat exchanger tube 2a. It is possible to secure a large heat transfer area between 2b and water, and to perform highly efficient heat exchange in the radiator 2.

  The above-described embodiment shows a specific example of the present invention. Therefore, the embodiment of the present invention is not limited to this, and various modifications can be made.

  The heat pump and the heat pump hot water supply apparatus of the present invention can be used for hot water supply for various purposes including general households. Moreover, it can be used not only for hot water supply but also for hot water heating. Furthermore, the heat pump of the present invention can also be used in applications in which an object other than water is heated as an object to be heated.

1. Compressor (compression means)
2 .... Radiator 2a ... Upstream heat transfer tube (heat transfer tube)
2b ... Downstream heat transfer tube (heat transfer tube)
2c ... turn-up part (heat transfer tube)
3 ... Expansion valve (throttle means)
5 .... Heat insulation (foamed resin heat insulation, heat loss reduction means)
DESCRIPTION OF SYMBOLS 10 ... Heat pump 20 ... Hot water storage tank 30 ... Heat-transfer tube holding member (heat loss reduction means)

Claims (5)

In the vapor compression heat pump in which the compression means, the radiator, the throttle means, and the evaporator are sequentially connected to form a closed circuit, and the pressure of the refrigerant in the radiator during operation exceeds the critical pressure of the refrigerant,
The radiator is composed of a heat transfer tube having a pipe as a refrigerant flow path, and at least a portion of the heat transfer tube is provided with a heat loss reducing means for preventing heat transfer from the portion to the other portion of the heat transfer tube. Features heat pump.   The radiator includes a folded portion provided at a substantially central portion of the entire length of the refrigerant flow path in the radiator, an upstream heat transfer tube and a downstream heat transfer tube that are substantially parallel to each other and face in the flow direction. The heat loss reducing means for preventing heat transfer from the upstream heat transfer tube to the downstream heat transfer tube is provided at least at a part between the outer heat transfer tube and the outer surface of the downstream heat transfer tube. Heat pump.   The heat pump according to any one of claims 1 to 2, further comprising a foamed resin heat insulating material that is in close contact with an outer surface of the heat transfer tube as the heat loss reducing means.   The heat pump according to any one of claims 1 to 3, further comprising a heat transfer tube holding member that maintains the interval between the heat transfer tubes within a predetermined range as the heat loss reducing means.   A hot water storage tank for storing water is provided, and the heat transfer tube of the radiator is inserted and arranged inside the hot water storage tank, and heat exchange is performed between the refrigerant in the heat transfer tube and the water in the hot water storage tank. A heat pump water heater using the heat pump according to any one of claims 1 to 4, wherein the heat pump water heater is used.

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