JP2009174832A - Heat exchanging system, and hot water storage type heat pump water heater, heater and water heater using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat exchanging system using as a heat transfer tube in which water flows, an internally-grooved tube which can be optimally matched to use conditions. <P>SOLUTION: In this heat exchanging system where the water w flows in the heat transfer tube 20 provided with a plurality of fins 201 on an inner face, and heats the water w by indirect heating by a refrigerant r outside the heat transfer tube 20, a lower limit Reynolds number Red in the beginning of the deterioration of stirring effects is determined by a formula (1) Red=226ä(Hf/D)(b/D)}<SP>(-0.46)</SP>, when a height of the fins of the heat transfer tube 20 is Hf, a maximum inner diameter is D, and an interval between the fins on a cross section is b, and the height Hf of fins of the heat transfer tube 20, the maximum inner diameter D and the interval b are set or the flow of the water w in the heat transfer tube 20 is set so that a Reynolds number Re of the flow of water w in the heat transfer tube 20 becomes more than the lower limit Reynolds number Red. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat exchange system for heating water such as a water heater or an electric water heater, a heat exchange system using an internally grooved pipe as a heat transfer pipe through which water flows, and a hot water storage type heat pump water heater using the same. The present invention relates to a heater and a water heater.

  In recent years, natural refrigerant heat pump water heaters, which have been rapidly spreading, use cheap nighttime electricity as hot water energy required for one day, boil hot water and store it in a tank (hereinafter referred to as hot water storage type). Called heat pump water heater). Since the water is boiled over time at night, the water flow rate is low and the flow becomes laminar. Therefore, to improve the performance as a heat exchanger, improve the heat transfer performance of the water tube (heat transfer tube) that becomes the bottleneck. Is essential.

  As a heat exchanger for improving heat transfer performance, there is a heat exchanger in which a water pipe is used as a core pipe and a refrigerant pipe is wound from the outside (see Patent Document 1). As the core tube, in addition to a smooth tube, a configuration in which a corrugated tube or an internally grooved tube is used, or a configuration in which a torsion plate is inserted into the core tube is disclosed. According to the heat exchanger described in Patent Document 1, it is described that the heat exchanger is effective in terms of ease of manufacture / transport, improvement of heat exchange, reduction of cost, and the like.

  In addition to hot water storage type heat pump water heaters, as a heat exchange system for heating water, a heat exchanger that directly heats circulating water for heating with a high-temperature heat source or a heater obtained by a heat pump, a heat pump water heater, or There are heat exchangers such as electric water heaters that use hot water stored in tanks using nighttime electricity as a heat source to refurbish baths, and heat exchangers that heat circulating water for heating.

  As heat transfer tubes used in a single-phase region through which water flows, as shown in Non-Patent Document 1, there is a study result on performance enhancement of the specifications of the internally grooved tube.

JP 2002-228370 A John R. Thome, "Engineering Data Book III", Wolverine Tube, Inc., Chapter 5 (Chapter 5)

  However, in the heat exchanger described in Patent Document 1, even if the core tube is simply formed into a corrugated shape, desired heat transfer performance may not be obtained, and cost and pressure loss may be increased. Further, when the core tube is an internally grooved tube, even if the heat transfer area is increased, the effect due to the increase of the heat transfer area cannot be sufficiently obtained in a laminar flow region having a low flow velocity. In addition, in order to improve the performance of the heat transfer tube through which the fluid to be heated flows, which constitutes the heat exchange system that heats water, it is commonly used in heat exchangers for air conditioners in which chlorofluorocarbon refrigerant flows. Even if an internally grooved tube is used, or an internally grooved tube that reflects the results examined in Non-Patent Document 1 is reflected in the specifications, if the matching with the operating conditions is not achieved, the performance decreases when the flow velocity decreases Becomes remarkable.

  Accordingly, an object of the present invention is to provide a heat exchange system that uses an internally grooved tube as a heat transfer tube through which water flows so as to optimally match the use conditions in a heat exchange system that heats water in a water heater or an electric water heater. It is to provide. In particular, a heat exchange system capable of improving the heat transfer performance of a heat exchanger even when used in a state where the flow rate of water is always small, such as a hot water storage heat pump water heater, and a hot water storage heat pump using the same An object is to provide a water heater, a heater and a water heater.

In order to achieve the above object, the present invention provides a heat exchange system in which water is flowed into a heat transfer tube provided with a plurality of fins on the inner surface and heated indirectly by a heating medium outside the heat transfer tube to heat the water. The lower limit Reynolds number Red at which the stirring effect starts to decrease, where Hf is the fin height of the heat transfer tube, D is the maximum inner diameter, and b is the distance between the fins in the cross section, is expressed by the following equation (1).
Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
The fin height Hf, the maximum inner diameter D, and the interval b of the heat transfer tube are set so that the Reynolds number Re of the water flow in the heat transfer tube is equal to or greater than the lower limit Reynolds number Red, or Provided is a heat exchange system in which the flow of water in the heat transfer tube is set.

  The heat exchange system may be provided, and hot water may be boiled by the heat exchange system.

  The above heat exchange system may be provided, and the circulating water for heating may be heated by the heat exchange system.

  The heat exchange system may be provided, and bath water may be reclaimed by the heat exchange system.

  The fins of the heat transfer tube are preferably formed in a spiral shape.

  ADVANTAGE OF THE INVENTION According to this invention, the heat exchange system which can improve the heat transfer performance of a heat exchanger even in the usage form with small flow rate of water like a hot water storage type heat pump type hot water heater, and a hot water storage type heat pump type hot water heater using the same An excellent effect is obtained in that a heater and a water heater can be obtained.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[First embodiment of the present invention]
Hereinafter, a hot water storage heat pump type hot water heater using carbon dioxide as a refrigerant will be described as an example.

  FIG. 1 shows a schematic configuration of a hot water storage type heat pump type hot water heater in the first embodiment of the present invention.

  The hot water storage type heat pump type hot water heater 10 has the heat exchange system of the present embodiment, and the heat exchange system includes a heat pump unit 18 and a hot water storage unit 19.

  The heat pump unit 18 includes a compressor 11, a water heat exchanger (gas cooler) 12, a decompressor (expansion valve, etc.) 13, and a heat absorber (evaporator) 14, and these are connected by a pipe 15-17 to refrigerating cycle. And a natural refrigerant (for example, carbon dioxide refrigerant) r is enclosed and circulated therein.

  Here, in the region “from the discharge part of the compressor 11 through the water heat exchanger 12 to the inlet part of the decompressor 13”, the refrigerant r is in a supercritical state (a state exceeding the critical pressure). The high-temperature and high-pressure refrigerant r and the water w from the hot water storage unit 19 exchange heat in the water heat exchanger 12, and the water w is heated.

  The hot water storage unit 19 includes a hot water storage tank 191 that stores water w or hot water obtained by heating the water w, a cold water pipe 192 and a hot water pipe 193 that connect the hot water storage tank 191 and the hydrothermal exchanger 12, and cold water. A circulation pump 194 for circulating water w and hot water between the hot water storage tank 191 and the water heat exchanger 12 provided in the pipe 192 is provided.

(Operation of hot water storage type heat pump type water heater)
Next, the operation of the hot water storage type heat pump hot water heater 10 will be described.

  The carbon dioxide refrigerant r compressed by the compressor 11 (for example, about 10 MPa in the present embodiment) is in a state (supercritical state) exceeding the critical pressure (about 7.4 MPa), and is a gas cooler (water heat exchanger) 12. Introduced into.

  The carbon dioxide refrigerant r in the supercritical state is not liquefied (does not enter a gas-liquid two-phase state) and is in a high-temperature and high-pressure state and exchanges heat with the water w (dissipates heat from the refrigerant r) in the gas cooler (water heat exchanger) 12. Thereafter, the pressure is reduced by the pressure reducer 13 (in this embodiment, for example, about 3.5 MPa), and a low-pressure gas-liquid two-phase state is obtained and introduced into the heat absorber 14.

  The carbon dioxide refrigerant r in the gas-liquid two-phase state absorbs heat from the air (atmosphere) in the heat absorber 14 to be in a gas state (gas phase single-phase state), and is sucked into the compressor 11 again. By repeating such a cycle, a heating action by heat radiation from the refrigerant r in the gas cooler (water heat exchanger) 12 and a cooling action by heat absorption of the refrigerant r in the heat absorber 14 are performed.

  On the other hand, in the hot water storage unit 19, water w supplied from a water supply source (not shown) is stored in advance in the hot water storage tank 191, and the water w stored in the hot water storage tank 191 is watered by the circulation pump 194 when the heat pump unit 18 is operated. It is sent to the heat exchanger 12. The water w sent to the water heat exchanger 12 is heated by the heating action of the water heat exchanger 12 and then returned to the hot water storage tank 191. Thereby, hot water is stored in the hot water storage tank 191 (hot water storage).

  Now, as a feature of the hot water storage type heat pump type hot water heater, it is mentioned that hot water is boiled and stored in the hot water storage tank 191 by using cheap night electricity for hot water supply energy required for one day. Therefore, high output as in the case of a combustion type water heater is not required, and for example, if it is operated for about 5 hours at night with an output of 4.5 kW, 370 L of 17 ° C. water can be heated to 65 ° C.

  From this, the heat pump unit 18 of FIG. 1 incorporating the compressor 11 having the same capability as that of a general home air conditioner (room air conditioner) can be used as a heat source device.

  Since the hot water storage type heat pump type hot water heater is premised on such usage, the flow rate of the water w flowing through the water heat exchanger 12 is extremely small. The dimensionless Reynolds number, which is the ratio of the inertia force and the viscous force, which is the product of the flow velocity and the density, is, for example, 2000 to 2000 when it is composed of one heat transfer tube having an outer diameter of 9.52 mm and a wall thickness of 0.6 mm. 7000, which is smaller than the usage conditions (Reynolds number of 10,000 or more) in a heat exchanger in which water flows, such as a chiller, and the stirring effect by turbulent flow is reduced. In particular, in a low temperature range where the viscosity is large, the flow of water becomes a laminar flow, and it is difficult to obtain a stirring effect, and the performance is significantly reduced. Therefore, in order to improve the performance by using an internally grooved tube as a water heat transfer tube, it is necessary to configure the heat transfer tube with an internally grooved tube having a specification matched to the Reynolds number used.

Therefore, in the heat exchange system of the present embodiment, water w flows through the heat transfer tube 20 provided with a plurality of fins 201 on the inner surface, and is heated indirectly by the refrigerant r that forms a heating medium outside the heat transfer tube 20 to heat the water w. And the Reynolds number Re of the flow of water w in the heat transfer tube 20 is obtained. On the other hand, the fin height of the heat transfer tube 20 is Hf, the maximum inner diameter is D, and the distance between the fins in the cross section is b. As the lower limit Reynolds number Red at which the stirring effect starts to decrease, the following formula (1)
Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
The fin height Hf, the maximum inner diameter D, and the interval b of the heat transfer tube 20 are set so that the Reynolds number Re of the flow of water w in the heat transfer tube 20 is equal to or greater than the lower limit Reynolds number Red. Setting or the flow of water w in the heat transfer tube 20 was set.

  Hereinafter, this point will be described.

(Configuration of heat exchanger)
FIG. 2 is an explanatory diagram showing the structure of the heat exchanger according to the first embodiment of the present invention. 2 is upside down from FIG. 1, and the heat pump unit 18 is located on the upper side and the hot water storage unit 19 is located on the lower side in FIG. 2.

  Pipes 15 and 16 of heat pump unit 18 and cold water and hot water pipes 192 and 193 of hot water storage unit 19 are connected to water heat exchanger 12 according to the present embodiment.

  Specifically, the water heat exchanger 12 is a double-pipe heat exchanger, and the heat transfer tube 20 formed from an inner surface grooved tube is used as an inner tube, and the water heat exchanger 12 is disposed outside the heat transfer tube 20 in the radial direction. An outer pipe 31 surrounding the heat pipe 20 is provided, and the refrigerant r flows in an annular path between the heat transfer pipe 20 and the outer pipe 31.

  In the illustrated example, an inlet head 311 is attached to one end portion (the right end portion in FIG. 2) of the outer pipe 31, and the inlet head 311 is connected to the discharge portion of the compressor 11 of the heat pump unit 18 via a pipe 15. The An outlet head 312 is provided at the other end (the left end in FIG. 2) of the outer pipe 31, and the outlet head 312 is connected to the inlet of the decompressor 13 of the heat pump unit 18 through the pipe 16.

  The heat transfer tube 20 is disposed concentrically in the outer tube 31 and extends in the tube axis direction, and protrudes to both sides in the tube axis direction through the inlet head 311 and the outlet head 312 of the outer tube 31. One end (the left end in FIG. 2) of the heat transfer tube 20 is connected to the cold water pipe 192 of the hot water storage unit 19, and the other end (the right end in FIG. 2) is connected to the hot water pipe 193 of the hot water storage unit 19. The intermediate portion of the heat transfer tube 20 is accommodated in the outer tube 31, and the water w in the heat transfer tube 20 and the refrigerant r in the outer tube 31 exchange heat through the wall surface of the intermediate portion.

(Configuration of heat transfer tube)
3 to 5 are explanatory views showing the structure of the heat transfer tube according to the first embodiment, FIG. 3 is an overall view, and FIG. 4 is an enlarged sectional view in the IV region of FIG.

  The heat transfer tube 20 is an internally grooved tube in which a plurality of spiral fins 201 are formed on the inner surface by rolling, and constitutes a heat exchanger 20 (for example, a water-refrigerant heat exchanger for a heat pump water heater). It is used as a water pipe. That is, heat exchange is performed between the water flowing inside the heat transfer tube 20 and the refrigerant flowing outside the heat transfer tube 20.

  A plurality of fins 201 are arranged on the inner surface of the heat transfer tube 20 at intervals in the circumferential direction, and each fin 201 extends in the tube axis direction while turning the inner surface of the heat transfer tube 20 in the circumferential direction, and has a predetermined twist angle. It is formed in a β-helix.

As described above, in the heat transfer tube 20 according to the present embodiment, the fin height is Hf, the maximum inner diameter is D, the distance between the fins in the cross section is b, and the lower Reynolds number at which the stirring effect starts to decrease is Red. As the following formula (1)
Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
The number of heat transfer tube passes and the heat transfer tube inner diameter D are selected so as to operate in a region having a Reynolds number greater than or equal to the lower limit Reynolds number Red determined by.

  Specifically, in order to operate the heat exchanger 20 so that the flow in the heat transfer tube 20 is in a region with a Reynolds number greater than or equal to the lower limit Reynolds number Red, a parameter (representative) for setting the Reynolds number Re of the heat transfer tube 20 is used. Length, representative speed, etc.) are determined, and the parameters are set appropriately. As parameters, the length of the heat transfer tube 20, the tube diameter (inner diameter), the flow rate (or flow velocity), and the like can be considered. The length of the heat transfer tube 20 is set, for example, by arranging a plurality of internally grooved tubes in parallel and connecting the ends of these internally grooved tubes with a bend to form a heat transfer tube, and the number of passes of the heat transfer tube It is done by adjusting. The flow rate is set, for example, by adjusting the discharge pressure (or discharge flow rate) of the circulation pump 194 of the hot water storage unit 19 or when the circulation pump 194 is rated at a predetermined discharge flow rate. This is done by adjusting the number of passes and the pipe diameter.

  The above is an example of setting the flow of water w in the heat transfer tube 20 so that the Reynolds number Re of the flow of water w in the heat transfer tube 20 is equal to or greater than the lower limit Reynolds number Red. The invention is not limited to this. Further, the fin height Hf, the maximum inner diameter D, and the interval b of the heat transfer tube 20 may be set according to the Reynolds number Re of the flow of water w in the circulation pump heat transfer tube 20.

  As described above, in a heat exchange system for heating water such as a water heater or an electric water heater, it is possible to provide a heat exchange system that uses an internally grooved tube that can be optimally matched with a use condition as a heat transfer tube through which water flows. it can. In particular, it is possible to provide a heat exchange system that can improve the heat transfer performance of the heat exchanger even when it is used in a state where the flow rate of water is always small, as in a hot water storage heat pump type hot water heater.

  Next, the derivation of Expression (1) will be described based on FIGS.

  Formula (1) of this embodiment prepares a plurality of test heat transfer tubes provided with a plurality of fins on the inner surface, and each test heat transfer tube has a different fin height Hf, maximum inner diameter D, and interval b. For each test heat transfer tube, the Reynolds number was used as a parameter to determine the relationship between the Reynolds number and the tube friction coefficient, and from these relationships, the lower Reynolds number at which the tube friction coefficient began to decrease was Each of the heat transfer tubes obtained is a product obtained by making the lower limit Reynolds number of each of the obtained heat transfer tubes, the fin height Hf and the interval b of each test heat transfer tube dimensionless and integrating each with the maximum inner diameter D. It is obtained by approximating the correlation with (Hf / D) (b / D) by a power approximation expression.

More specifically, when the fin height of the inner grooved tube of the present invention is Hf, the maximum inner diameter is D, and the distance between the fins in the cross section is b, the lower limit Reynolds number at which the stirring effect starts to decrease is Red. Is the following formula (1)
Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
It was determined by the experiment described below.

  FIG. 6 shows a schematic diagram of a measuring apparatus used in the above experiment according to the present invention. The test section is a double pipe composed of an inner pipe 71 that is a test pipe (test heat transfer pipe) and an outer pipe 72 that surrounds the inner pipe 71. The test section 71 and the test pipe 71 Cold water c and hot water h flow oppositely between the annular path 73 between the outer pipe 72 and the outer pipe 72. As the test tube 71, a smooth tube (No. 1, No. 15), a corrugated tube (No. 3), and an inner grooved tube (No. 7-14, No. 16-17) were used.

  The heat exchange amount of each of the test tube 71 and the annular path 73 was determined, and the experiment was performed in the range of heat balance ± 5%. Thermocouples (copper-constantan wire diameter 0.2 mm) were embedded in a total of six locations, two on the outer peripheral wall of the test tube 71 and two in the vertical direction and three in the tube axis direction, and the tube wall temperature was measured. The pipe heat transfer coefficient Nu / Pr0.4 was obtained by dividing the heat flux on the pipe inner surface reference by the logarithmic temperature difference between the pipe wall temperature average value and the pipe inlet / outlet temperature. For the surface area inside the tube, measured values were used for the smooth tube and the corrugated tube, and the area calculated by the maximum inner diameter was used for the internally grooved tube. The tube friction coefficient f was obtained from the measured value by the Darcy-Weisbach equation. The thermophysical value of water was calculated by PROPATH.

  Table 1 shows the outer diameter DO, the bottom wall thickness Tw, the fin height Hf, the fin number N, and the twist angle β (see FIG. 3-5) of the test tubes (No. 1, No. 7-17).

  No. 1 and no. 15 are φ9.52 and φ12.7 smooth tubes, respectively, which were measured for confirmation of experimental accuracy. It was within ± 10% compared with the heat transfer coefficient calculated by the Petukhov-Gnielinski equation in the turbulent region (Re> 3000).

  No. Nos. 7 to 14 are inner grooved pipes of No. Reference numerals 16 and 17 are φ12.7 inner grooved tubes. Although not shown in Table 1, no. 3 is a φ9.52 corrugated tube.

  In FIG. The measurement result of the heat transfer coefficient Nu / Pr0.4 of 1,3,9,11 is shown. No. No. 9 is No. in the high Reynolds number region. Although the performance of the corrugated tube of 3 is exceeded, the Reynolds number of 2000 is No. The performance is reduced to the same level as that of the 1 smooth tube. No. No. 11 is the specification with the best performance in the lowest Reynolds number region among the internally grooved tubes tested this time. The performance of the 3 corrugated tube is higher than this.

  Therefore, in order to examine the specifications of the internally grooved tube that can achieve high performance in the low Reynolds number region, the Reynolds number of the internally grooved tube tested this time, which starts to decrease in the low Reynolds number region, is used as the tube friction coefficient. Organize with attention.

  FIG. 11 is a measurement result of heat transfer coefficient Nu / Pr0.4 of 11 and 17 and pipe friction coefficient f. As the Reynolds number decreases, there is a point at which the friction coefficient decreases. From this point, it can be seen that when the Reynolds number decreases, the flow transitions to laminar flow and the heat transfer coefficient begins to decrease.

  Therefore, in order to compare each inner grooved tube relatively, the Reynolds number (lower limit Reynolds number) Red whose performance starts to decrease is reduced by 10% from the maximum value of the friction coefficient (maximum value−minimum value). It is defined as

  In order to consider the relationship between the fin shape and Red, three dimensionless numbers s / D (where s is the pipe axis pitch of one spiral groove, D is the maximum inner diameter ID), b / D (b is the distance between the fin and the fin) FIG. 9 shows the results organized by Hf / D.

  From FIG. 9, it can be inferred that b / D and Hf / D have a correlation. Therefore, FIG. 10 shows the correlation between the product of (b / D) and (Hf / D) and Red. The correlation in FIG. 10 can be expressed by the following equation (1) which is a power approximation equation.

Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
Therefore, according to the formula (1), the inner grooved tube used as the heat transfer tube in the heat exchanger for heating water is selected according to the use conditions of the heat exchange system, or the inner grooved It can be seen that a heat exchange system (path, flow rate, pipe diameter, etc.) that allows the pipe to perform sufficiently can be selected.

  Next, another embodiment of the present invention will be described with reference to FIGS.

  The heat exchange systems according to the second and third embodiments described below are mainly different from the above-described first embodiment in the configuration of the water heat exchanger of the heat pump unit 18, and the others are the same. Yes. Therefore, only the configuration of the water heat exchanger will be described, and description of other configurations will be omitted. The same elements as those in the first embodiment are designated by the same reference numerals in the drawings, and detailed description thereof is omitted.

[Second Embodiment of the Present Invention]
(Configuration of heat exchanger)
11 and 12 are explanatory views showing the structure of the heat exchanger according to the second embodiment of the present invention.

  The heat exchanger 40 according to the present embodiment is a triple-pipe heat exchanger, and the heat transfer tube (inner grooved tube) 20 according to the first embodiment of the present invention described above is used as an inner tube. A leak detection tube 42 provided with a leak detection groove 41 is disposed in contact with the inner periphery of the smooth tube so that a leak detection portion is formed on the outer periphery of the heat tube 20, and the outer tube 31 is further outside the leak detection tube 42. It is arranged so that the refrigerant r flows through an annular path between the leak detection pipe 42 and the outer pipe 31.

  In the illustrated example, the heat transfer tube 20 is fitted into the leak detection tube 42, and the outer peripheral surface of the heat transfer tube 20 and the inner peripheral surface of the leak detection tube 42 abut. A plurality of leak detection grooves 41 extending in the pipe axis direction are formed at intervals in the circumferential direction on the inner peripheral surface of the leak detection pipe 42, and the leak detection unit is formed by the leak detection grooves 41 and the outer peripheral surface of the heat transfer pipe 20. A compartment is formed. The leak detection unit is connected to a leak sensor 63 (for example, a moisture sensor or a pressure sensor), and the leak sensor 63 detects water w leaked from the heat transfer tube 20 to the leak detection unit, a pressure change due to the leak, or the like.

  In this embodiment, the same effect as that of the above-described embodiment can be obtained, and furthermore, leakage of water can be detected early and easily.

[Third embodiment of the present invention]
(Configuration of heat exchanger)
FIG. 13 is an explanatory view showing the structure of a heat exchanger according to the third embodiment of the present invention.

  The heat exchanger 50 according to the present embodiment is configured by winding a spiral heat transfer tube 51 for circulating refrigerant around the outer surface of the heat transfer tube 20 according to the first embodiment described above. If necessary, the outer surface of the heat transfer tube 20 and the helical heat transfer tube 51 may be fixed by brazing or the like.

  In the heat exchanger 50 of this embodiment, heat exchange is performed between the water flowing in the heat transfer tube 20 and the refrigerant flowing in the spiral heat transfer tube 51 in contact with the outer periphery of the heat transfer tube 20.

  Also in this embodiment, the same effect as the above-described embodiment can be obtained.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications and application examples can be considered.

  For example, in the above-described embodiment, the heat exchange system of the present invention is applied to a hot water storage type heat pump water heater that boils hot water using the heat exchange system. However, the present invention is not limited to this, and the heat exchange system is a heat exchange system. The present invention may be applied to a heater for heating circulating water for heating, a water heater for chasing hot water in a bath by a heat exchange system, or the like.

  Further, the heating medium is not limited to a natural refrigerant (such as a carbon dioxide refrigerant) for a heat pump, and various heating media are conceivable. For example, the heating medium may be chlorofluorocarbon, which is a heat pump refrigerant, and may be hot water, steam, a heater, or the like in addition to the heat pump refrigerant.

FIG. 1 is a schematic configuration diagram of a hot water storage type heat pump type hot water heater. FIG. 2 is an explanatory diagram of the structure of the heat exchanger according to the first embodiment of the present invention. FIG. 3 is an explanatory diagram of the structure of the heat transfer tube according to the first embodiment of the present invention. FIG. 4 is a detailed view of a region IV in FIG. FIG. 5 is an explanatory diagram of the structure of the heat transfer tube according to the first embodiment of the present invention. FIG. 6 is a schematic view of a measuring apparatus used in the experiment. FIG. 7 shows the heat transfer coefficient measurement results of the internally grooved tube. FIG. 8 shows the heat transfer coefficient and pressure loss measurement results of the internally grooved tube. FIG. 9 shows the result of arranging the lower limit Reynolds number Red at which the stirring effect is reduced by three dimensionless numbers s / D, b / D, and Hf / D. FIG. 10 shows the correlation between the product of (b / D) and (HF / D) and the lower limit Reynolds number Red. FIG. 11 is an explanatory diagram of the structure of the heat exchanger according to the second embodiment of the present invention. 12 is a cross-sectional view taken along line XII-XII in FIG. FIG. 13 is an explanatory diagram of the structure of the heat exchanger according to the third embodiment of the present invention.

Explanation of symbols

10 Hot Water Storage Heat Pump Water Heater 11 Compressor 12 Gas Cooler (Water Heat Exchanger)
13 Pressure reducer 14 Heat absorber (evaporator)
20 Inner grooved tube 30 Double tube heat exchanger 31 Outer tube of double tube heat exchanger 40 Triple tube heat exchanger 41 Leak detection groove 42 Leak detection tube 50 Heat exchanger 51 Spiral heat transfer tube

Claims (5)

In a heat exchange system in which water is flowed into a heat transfer tube provided with a plurality of fins on the inner surface and heated indirectly by a heating medium outside the heat transfer tube, the water is heated.
The lower limit Reynolds number Red at which the stirring effect starts to decrease, where Hf is the fin height of the heat transfer tube, D is the maximum inner diameter, and b is the distance between the fins in the cross section, is expressed by the following equation (1).
Red = 226 {(Hf / D) (b / D)} ^(−0.46) (1)
Determined by
The fin height Hf, the maximum inner diameter D, and the interval b of the heat transfer tube are set such that the Reynolds number Re of the water flow in the heat transfer tube is equal to or greater than the lower limit Reynolds number Red, or the heat transfer A heat exchange system characterized by setting the flow of water in the pipe.   A hot water storage type heat pump type hot water heater comprising the heat exchange system according to claim 1, wherein hot water is boiled by the heat exchange system.   A heating machine comprising the heat exchange system according to claim 1 and heating the circulating water for heating by the heat exchange system.   A water heater comprising the heat exchanging system according to claim 1, and chasing hot water in the bath by the heat exchanging system.   The heat exchange system according to claim 1, wherein the fin of the heat transfer tube is formed in a spiral shape.

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