JP2007322069A - Coolant heat transfer tube for heat pump type heat exchanger, and gas cooler using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coolant heat transfer tube capable of improving heat transfer performance 1.5 times or more compared to a plain tube even when the amount of lubricating oil for a compressor flowing into a coolant tube for a gas cooler is comparatively large in a gas cooler for a heat pump type heat exchanger using carbon dioxide as a coolant, and to provide a gas cooler using the heat transfer tube. <P>SOLUTION: The coolant heat transfer tube 40 is used in the gas cooler (a water heat exchanger) for the heat pump type heat exchanger using carbon dioxide as the coolant, and it is provided with three small diameter tubes 4 used as fins fixed to an inner face of its outer tube 1. It is characterized by that when an inner diameter of the outer tube 1 is ID, and a height of the fin (the small diameter tube 4) is H<SB>f</SB>, H<SB>f</SB>/ID is 0.1 or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is for refrigerants of heat pump water heaters and heat pump air conditioners that use natural refrigerants (hereinafter, heat pump water heaters and heat pump air conditioners may be collectively referred to as “heat pump heat exchangers”). The present invention relates to a heat transfer tube and a gas cooler, and more particularly to a refrigerant heat transfer tube used in a heat pump heat exchange device using carbon dioxide as a refrigerant, and a gas cooler using the heat transfer tube.

  FIG. 11 is a diagram illustrating the correlation between the heat pump heat exchange device and the refrigerant used therein.

  A heat pump is a system that heats and cools by pumping and moving heat from a heat source (usually inexpensive and abundant resources such as air, groundwater, seawater, etc.) using a compressor (compressor). For example, in an electric heat pump, it is said that heat energy that is nearly three times the power consumption (consumed energy) can be used by using it as a power source that moves heat, instead of directly converting electric energy into heat energy. ing. This is a system that is more efficient and less burdensome on the environment than conventional systems that burn fossil fuels such as petroleum to produce thermal energy. For this reason, heat pump heat exchange devices have been widely used in recent years.

  On the other hand, chlorofluorocarbon-based refrigerants have been conventionally used in general heat exchange devices (such as air conditioners, refrigerators, refrigerators, and water heaters) that use a refrigeration cycle. However, natural refrigerants, particularly carbon dioxide, that have a low environmental impact have recently been attracting attention because of the concern that there is concern about the impact on global warming. For economic and environmental reasons, expectations for a natural refrigerant (particularly carbon dioxide) heat pump heat exchange device combined with the above-described heat pump are rapidly increasing, for example, for eco-cutes and car air conditioners.

  Generally, a heat pump type heat exchange device using a carbon dioxide refrigerant uses a gas cooler (heat radiator) and an evaporator (heat absorber) as heat exchangers. As the heat pipe, a gas cooler refrigerant pipe and an evaporator refrigerant pipe are used.

  For example, in a heat pump water heater using carbon dioxide refrigerant, the gas cooler is also called a water heat exchanger, and in addition to the above two types of heat transfer tubes, another heat transfer tube (gas tube for water cooler) that exchanges heat with the refrigerant. Also used. The technical specifications required for these heat transfer tubes (gas cooler water tube, gas cooler refrigerant tube, evaporator refrigerant tube) are different from each other.

  As a heat exchanger used for such a heat pump type hot water heater using carbon dioxide as a refrigerant, for example, there is a heat exchanger in which inner fins are arranged in a water pipe for a gas cooler for the purpose of improving heat exchange efficiency ( Patent Document 1).

  However, Patent Document 1 does not disclose a configuration or the like that improves the heat exchange efficiency of the refrigerant pipe for the gas cooler.

As an object of improving the heat exchange efficiency of the gas cooler refrigerant pipe, there is a heat exchanger in which the gas cooler refrigerant pipe is a heat transfer pipe with a predetermined inner surface groove (see Patent Documents 2 and 3).
JP 2002-5516 A JP-A-2005-257160 JP 2005-188789 A

  However, carbon dioxide refrigerant flowing in the refrigerant pipe for the gas cooler has a serious problem that heat exchange of the heat transfer pipe is hindered by mixing compressor lubricating oil that is a lubricant for the compressor of the refrigeration cycle. . This is considered because the compatibility between the carbon dioxide refrigerant and the compressor lubricating oil is not good. Moreover, such a problem is a problem that was not found in conventional fluorocarbon refrigerants.

  In heat pump heat exchangers (such as water heaters and air conditioners) that use carbon dioxide refrigerant, polyalkylene glycol oil (PAG oil) is usually used as the lubricating oil for the compressor, and oil is supplied by the differential pressure oil supply method. . At this time, since the differential pressure (pressure difference before and after the compressor) is large as a feature of using the carbon dioxide refrigerant, the absolute amount of oil supply tends to increase, and the compressor lubricating oil flows out to the cycle outside the compressor. (The compressor lubricating oil is mixed in the carbon dioxide refrigerant, and the mixed amount tends to increase).

  Incidentally, in a heat pump type heat exchange device using a conventional chlorofluorocarbon refrigerant, the compressor lubricating oil mixed in the chlorofluorocarbon refrigerant has a differential pressure of about 1.5 MPa and is 0.1 to 0.15 mass. It is said to be about%. Further, it is said that the compatibility between the chlorofluorocarbon refrigerant and the compressor lubricating oil is satisfactory (good).

  On the other hand, in a heat pump heat exchange device using a carbon dioxide refrigerant, the differential pressure of the compressor is about 5.5 to 7.5 MPa, which is 4 to 5 times higher than the conventional one. It is conceivable that the concentration of the lubricating oil mixed therein becomes very high. Furthermore, as described above, it is considered that the compatibility between the carbon dioxide refrigerant and the compressor lubricating oil is not good.

  In the heat exchangers described in Patent Documents 2 and 3, the influence of the lubricating oil concentration of the compressor in the refrigerant flowing in the pipe is not examined. For example, in the heat exchanger described in Patent Document 3, if the concentration of the compressor lubricating oil in the refrigerant is high, the effect of improving the heat exchange efficiency cannot be obtained. This is presumably because the fins on the inner surface of the heat transfer tube (grooves on the inner surface of the heat transfer tube) are buried with the lubricating oil of the compressor mixed in the refrigerant, and the contribution of the increase in the heat transfer area is offset.

  In addition, carbon dioxide flowing through the gas cooler refrigerant pipe has a very large Reynolds number Re and is already turbulent in the smooth pipe. Therefore, the turbulent flow effect (the action of generating turbulent flow) by the inner grooved pipe is It has little meaning.

  Accordingly, an object of the present invention is to provide a smooth heat pump type heat exchange device using carbon dioxide as a refrigerant, particularly when there is a relatively large amount of compressor lubricating oil (for example, 0.2% by mass or more) in a refrigerant pipe for a gas cooler. An object of the present invention is to provide a refrigerant heat transfer tube capable of improving heat transfer performance to a tube ratio of 1.5 times or more, and a gas cooler using the heat transfer tube.

In order to achieve the above object, the first aspect of the present invention is a refrigerant heat transfer tube used in a gas cooler of a heat pump heat exchange device using carbon dioxide as a refrigerant, wherein the refrigerant heat transfer tube includes: an outer tube; And a fin fixedly installed on the inner surface of the outer tube, where H _f / ID is 0.1 or more and 0.5 or less, where ID is the inner diameter of the outer tube and H _f is the height of the fin. A refrigerant heat transfer tube is provided.

In the present invention, the height of the fin means the maximum height of the fin in the direction perpendicular to the central axis of the heat transfer tube from the contact portion between the fin material and the heat transfer tube in the direction of the central axis of the heat transfer tube (the center of the cross section). (Thus, the maximum of H _f / ID is 0.5).

The first aspect of the present invention includes the invention having the following features.
(1) The fin is made of a plate material.
(2) The fin is formed of a molded member.
(3) The fin is a hollow fin configured by a plurality of small diameter tubes.
(4) The fin has a thickness equal to or less than a thickness of the outer tube.
(5) The fin is fixedly installed on the inner surface of the outer tube by fitting.
(6) The refrigerant contact area enlargement ratio due to the provision of the fins is 1.5 times or more.
(7) When the height of the fin is H _f and the inner diameter of the outer tube is ID, H _f / ID is 0.2 or more.

  In the present invention, the expansion ratio of the refrigerant contact area due to the provision of the fins means the wetted perimeter with respect to the refrigerant in the cross section perpendicular to the central axis of the heat transfer tube, the same outer diameter and the same pressure resistance as the heat transfer tube. Defined as divided by that of a smooth tube with capacity.

  In order to achieve the above object, the second aspect of the present invention is a refrigerant heat transfer tube used in a gas cooler of a heat pump heat exchange device using carbon dioxide as a refrigerant, and includes an outer tube and an inner surface of the outer tube. Provided is a refrigerant heat transfer tube comprising a plurality of small-diameter tubes whose outer circumferences are fixedly installed.

The second aspect of the present invention includes an invention having the following features.
(1) When the height of the small diameter tube is H _f and the inner diameter of the outer tube is ID, H _f / ID is 0.1 or more. More desirably, H _f / ID is 0.2 or more.
(2) The small diameter tube has a thickness equal to or less than the thickness of the outer tube.
(3) The refrigerant contact area enlargement ratio due to the provision of the small-diameter pipe is 1.5 times or more.

  The expansion ratio of the refrigerant contact area due to the provision of the small-diameter pipe can be defined as the sum of the inner circumference of the small-diameter pipe divided by the inner circumference of the outer pipe from the above definition (the refrigerant only inside the hollow fin). Is distributed).

The first and second aspects of the present invention include the invention having the following characteristics.
(1) The said gas cooler is used for the heat pump type heat exchange apparatus using polyalkylene glycol oil as lubricating oil of the compressor of a refrigerating cycle.
(2) In the carbon dioxide as the refrigerant, 0.2% by mass or more of lubricating oil of a compressor constituting a refrigeration cycle in the heat pump heat exchange device is mixed.
(3) The gas cooler is a radiator of a heat pump heat exchange device.

  In order to achieve the above object, a third aspect of the present invention provides a gas cooler comprising the refrigerant heat transfer tube according to the present invention.

  According to the present invention, in a heat radiator (gas cooler) of a heat pump heat exchange device using carbon dioxide as a refrigerant (for example, a water heater or an air conditioner), the compressor lubricating oil in the refrigerant pipe for the gas cooler is relatively large. Even in the case (for example, 0.2% by mass or more), it is possible to obtain a refrigerant heat transfer tube capable of improving the heat transfer performance to a smooth tube ratio of 1.5 times or more, and a gas cooler using the heat transfer tube. . In addition, the heat transfer performance in the present invention is defined as an in-tube heat transfer coefficient calculated by an expression described later.

[First embodiment of the present invention]
(Configuration of carbon dioxide refrigerant heat pump water heater)
A hot water heater will be described as an example of a heat pump heat exchange device using carbon dioxide as a refrigerant.

  FIG. 1 shows a schematic configuration of a carbon dioxide refrigerant heat pump water heater in an embodiment of the present invention.

  The carbon dioxide refrigerant heat pump water heater 10 includes a compressor 11, a gas cooler (water heat exchanger) 12, a decompressor 13 and a heat absorber (evaporator) 14, and these are connected by a pipe 15 to constitute a refrigeration cycle. And carbon dioxide refrigerant is enclosed. Here, in the region of “the discharge portion of the compressor 11 → the water heat exchanger 12 → the inlet portion of the decompressor 13”, the refrigerant is in a supercritical state (a state exceeding the critical pressure). For example, polyalkylene glycol oil (PAG oil) is used as the lubricating oil for the compressor.

(Operation of carbon dioxide refrigerant heat pump water heater)
Next, the operation of the carbon dioxide refrigerant heat pump type water heater 10 will be described.
The carbon dioxide refrigerant compressed by the compressor 11 (in this embodiment, for example, about 10 MPa) is transferred to the gas cooler (water heat exchanger) 12 in a state exceeding the critical pressure (about 7.4 MPa) (supercritical state). be introduced.

  The supercritical carbon dioxide refrigerant does not liquefy (does not enter a gas-liquid two-phase state) and is in a high-temperature and high-pressure state, and exchanges heat with water or the like (dissipates heat from the refrigerant) 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 that has become a gas-liquid two-phase state absorbs heat from the air (atmosphere) in the heat absorber 14 to become a gas state (a single-phase state in a gas phase), and is sucked into the compressor 11 again. By repeating such a cycle, the heating action by the heat radiation from the refrigerant in the gas cooler (water heat exchanger) 12 and the cooling action by the heat absorption of the refrigerant in the heat absorber 14 are performed.

(Configuration of refrigerant heat transfer tube)
Next, the refrigerant heat transfer tube of the gas cooler (water heat exchanger) 12 which is a heat exchanger according to the present embodiment will be described.

  FIG. 2 is a cross-sectional view of the refrigerant heat transfer tube according to the first embodiment in which the plate material is a fin material.

  The refrigerant heat transfer tube 20 has a configuration in which the fin material 2 made of a plate material is inserted into the outer tube 1 and the fin material 2 is fixedly installed on the inner surface of the outer tube 1 by fitting (in FIG. 2, the number of fins). Is 2).

When the inner diameter of the outer tube 1 is ID and the height of the fin made of the fin material 2 is H _f , H _f / ID is 0.5 which is 0.1 or more. Further, regarding the refrigerant contact area expansion rate by installing the fins made of the fin material 2, for example, when the outer diameter of the outer tube 1 is 4 mm, and the wall thickness of the outer tube 1 and the fin material 2 are both 0.4 mm, The expansion ratio of the refrigerant contact area is about 1.6 times that is 1.5 times or more. As a result, even if a large amount of compressor lubricating oil flows in the heat transfer tube (for example, about 0.5% by mass or more of the refrigerant amount), heat transfer can be promoted without being affected by the influence. It becomes possible.

In order to make the height H _{f of the} fin H _f /ID≧0.1, and further to make the refrigerant contact area expansion ratio 1.5 times or more, the fin provided on the inner surface of the pipe is not based on the conventional rolling process, This can be realized by inserting a plate material and bringing it into intimate contact with the inner surface.

  As a material of the outer tube 1 of the heat transfer tube 20 for the refrigerant, copper alloy, copper alloy, aluminum, aluminum alloy, or the like can be used in consideration of thermal conductivity and mechanical strength.

  As the material of the fin material 2, as with the outer tube 1, copper, copper alloy, aluminum, aluminum alloy, or the like can be used. Further, it is desirable that the thickness of the fin material 2 is equal to or less than the thickness of the outer tube 1. As described above, the carbon dioxide refrigerant has a very high pressure (for example, about 10 MPa). However, since the pressure resistance can be secured by the thickness of the outer tube 1, the plate member to be inserted is thinner than the thickness of the outer tube 1. Is possible. Thereby, the mass increase (with respect to a smooth tube) of the heat exchanger tube 20 for refrigerant | coolants can be suppressed to the minimum.

(Effects of the first embodiment)
According to the present embodiment, the following effects can be obtained.
In a gas cooler of a heat pump heat exchange device (such as a water heater or an air conditioner) that uses carbon dioxide as a refrigerant, if the lubricant in the compressor in the refrigerant pipe for the gas cooler is relatively large (for example, about 0.5% by mass of the refrigerant amount) Even if it is above, the heat exchanger tube for refrigerant | coolants which can improve heat-transfer performance to 1.5 times or more smooth tube ratio is obtained.

[Second Embodiment of the Present Invention]
(Configuration of refrigerant heat transfer tube)
FIG. 3 is a cross-sectional view of a refrigerant heat transfer tube according to a second embodiment in which a molded member is a fin material.

  The refrigerant heat transfer tube 30 has a configuration in which a fin member 3 made of a molded member (cross shape in FIG. 3) is inserted into the outer tube 1 and the fin member 3 is fixedly installed on the inner surface of the outer tube 1 by fitting. (In FIG. 3, the number of fins is 4). In addition, although the manufacturing method of a shaping | molding member is not specifically limited, An extrusion process etc. can be utilized suitably.

When the inner diameter of the outer tube 1 is ID and the height of the fin made of the fin material 3 is H _f , H _f / ID is 0.5 which is 0.1 or more. Further, regarding the refrigerant contact area enlargement ratio due to the installation of fins made of the fin material 3, for example, the outer diameter of the outer tube 1 is 7 mm, and the wall thicknesses of the outer tube 1 and the fin material 3 (cross shape in FIG. 3) are both In the case of 0.7 mm, the refrigerant contact area expansion ratio is about 1.9 times, which is 1.5 times or more. As a result, even if a large amount of compressor lubricating oil flows in the heat transfer pipe (for example, about 0.2 mass% or more of the refrigerant amount), heat transfer can be promoted without being affected by the influence. It becomes possible.

In order to make the height H _{f of the} fin H _f /ID≧0.1, and further to make the refrigerant contact area expansion ratio 1.5 times or more, the fin provided on the inner surface of the pipe is not based on the conventional rolling process, This can be realized by inserting a molding member and bringing it into intimate contact with the inner surface.

  The material of the outer tube 1 of the refrigerant heat transfer tube 30 and the material of the fin material 3 are the same as those of the outer tube 1 and the fin material (plate material) 2 of the refrigerant heat transfer tube 20 of the first embodiment, respectively. As for the thickness of the fin material 3, it is desirable to set it as the thickness below the thickness of the outer tube | pipe 1. FIG. As described above, the carbon dioxide refrigerant has a very high pressure, but since the pressure resistance can be secured by the thickness of the outer tube 1, the inserted molding member can be made thinner than the thickness of the outer tube 1. is there. Thereby, the mass increase (with respect to a smooth tube) of the heat exchanger tube 30 for refrigerant | coolants can be suppressed to the minimum.

  The expansion ratio of the refrigerant contact area due to the installation of fins made of the fin material 3 does not fall below the rate of increase in pressure loss due to the installation of the fin material 3 (pressure loss of the heat transfer tube / pressure loss of the smooth tube). It is preferable. This is to prevent the refrigerant flow passage cross-sectional area in the heat transfer tube from being reduced by the installation of the fin material 3 so that the pressure loss does not increase more than the refrigerant contact area expansion rate. For example, when the thicknesses of the fin material 3 and the outer tube 1 are the same, it is preferably 2.5 times or less. However, when the thickness of the fin material 3 is smaller than the thickness of the outer tube 1, the upper limit of the refrigerant contact area expansion rate is naturally larger than 2.5 times.

(Effect of the second embodiment)
According to the present embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.
It is easy to increase the effective surface area of the fin material compared to the plate material, and higher performance can be achieved.

[Third embodiment of the present invention]
(Configuration of refrigerant heat transfer tube)
FIG. 4 is a sectional view of a refrigerant heat transfer tube according to a third embodiment using a small-diameter tube as a fin material.

  The refrigerant heat transfer tube 40 has a configuration in which three small diameter tubes 4 as fin materials are inserted into the outer tube 1 and the three small diameter tubes 4 are fixedly installed on the inner surface of the outer tube 1 by fitting. (In FIG. 4, the number of fins is three).

When the height of the fins becomes the inner diameter of the outer tube 1 from the ID and the small diameter pipe 4 (hollow fins) and _{H f,} relates H f / ID, for example, in FIG. 4, the outer diameter of the outer tube 1 is 4 mm, the outer tube 1 When the wall thickness of the small diameter tube 4 is 0.1 mm, H _f / ID is 0.43 which is 0.1 or more. The expansion ratio of the refrigerant contact area due to the installation of the fins composed of the three small-diameter pipes 4 is about 1.8 times or more, which is 1.5 times or more (the refrigerant is placed only inside the small-diameter pipes 4). When it is distributed, it becomes about 1.8 times, and when other parts are considered, it becomes 1.8 times or more). As a result, even if a large amount of compressor lubricating oil flows in the heat transfer pipe (for example, about 0.2 mass% or more of the refrigerant amount), heat transfer can be promoted without being affected by the influence. It becomes possible.

In order to make the height H _{f of the} fin H _f /ID≧0.1, and further to make the refrigerant contact area expansion ratio 1.5 times or more, the fin provided on the inner surface of the pipe is not based on the conventional rolling process, This can be realized by inserting the small-diameter pipe 4 and bringing it into close contact with the inner surface to form a hollow fin material.

  The material of the outer tube 1 of the refrigerant heat transfer tube 40 and the material of the small diameter tube 4 are the same as those of the outer tube 1 and the fin material (plate material) 2 of the refrigerant heat transfer tube 20 of the first embodiment, respectively. The thickness of the small diameter tube 4 is preferably set to a thickness equal to or less than the thickness of the outer tube 1. As described above, the carbon dioxide refrigerant has a very high pressure, but the pressure resistance can be secured by the thickness of the outer tube 1, so that the small diameter tube to be inserted can be made thinner than the thickness of the outer tube 1. is there. Thereby, the mass increase (with respect to a smooth tube) of the heat exchanger tube 40 for refrigerant | coolants can be suppressed to the minimum.

  In the third embodiment, a space formed outside the small diameter tube 4 (a first space 5 formed by the outer tube and the small diameter tube, and a second space 6 formed by the small diameter tubes). However, the refrigerant may or may not be circulated, but the refrigerant contact area enlargement ratio (wetting edge length) can be increased by circulating the refrigerant, and the heat transfer area can be effectively utilized.

  On the other hand, the first space 5 and the second space 6 are sealed to prevent the refrigerant from flowing into the first space 5 and the second space 6 (for example, using a brazing material). It is possible to reduce the thickness of the outer tube 1 related to the pressure resistance of the heat transfer tube 40 by the thickness of the small-diameter tube 4 by sealing at both ends of the heat tube 40 (or gas cooler). Thereby, the mass increase (with respect to a smooth tube) of the heat exchanger tube 40 for refrigerant | coolants can be suppressed to the minimum.

(Effect of the third embodiment)
According to the present embodiment, in addition to the effects of the first embodiment, the following effects can be obtained.
Since the contact length between the inner surface of the outer tube and the outer surface of the small-diameter tube can be increased, the variation due to the contact is small and a stable shape can be obtained. In addition, for the same reason, variation related to heat transfer is reduced, and stable heat transfer performance can be obtained.

[Other Embodiments of the Present Invention]
As an embodiment of the present invention, there are various forms in addition to the first to third embodiments described above. Examples include the following forms.
(1) In the third embodiment, the number of the small diameter tubes 4 is three, but may be 2, 4, 5, or 7. In this case (including three cases), the rate of expansion of the refrigerant contact area due to the installation of the small-diameter pipe 4 is the rate of increase in pressure loss due to the installation of the small-diameter pipe 4 (the pressure of the heat transfer pipe). Loss / pressure loss of the smooth tube).

(2) Although the heat pump type hot water heater has been described as an example, the present invention can be similarly applied to a heat pump type air conditioner.

  FIG. 5 shows a schematic diagram of a double-pipe heat exchanger for evaluating heat transfer performance. As shown in FIG. 5, a double pipe heat having a heat transfer pipe 51 for refrigerant as an inner pipe and a water pipe 52 for flowing water for removing heat from the refrigerant in an annular shape (jacket shape) outside the inner pipe. An exchanger 50 was configured.

Table 1 shows the specifications of the evaluated refrigerant heat transfer tubes.
Example 1 is a heat transfer tube according to the third embodiment, and a small-diameter tube (outer diameter 2 mm, wall thickness 0.1 mm) is connected to an outer tube (outer diameter 5.3 mm, wall thickness 0.38 mm). After inserting three, it was produced by performing co-drawing.

  Comparative Examples 1 to 6 are internally grooved tubes, which were produced by conventional rolling. Reference Examples 1 to 3 are smooth tubes.

  The “twist angle” refers to an angle formed by the tube center axis direction and the groove direction in the internally grooved tube. In addition, the “bottom wall thickness” means the wall thickness of the tube at the groove bottom (the thinnest portion of the inner surface grooved tube), and with respect to the pressure resistance of the tube, It is synonymous with the thickness of the outer tube in the heat transfer tube. Therefore, the inner diameter ID of the inner grooved tube is “ID = outer diameter−bottom wall thickness × 2”.

  The heat transfer performance of each refrigerant heat transfer tube shown in Table 1 was measured. Table 2 shows the measurement conditions in the heat transfer performance measurement. The heat transfer coefficient in the pipe was evaluated as the heat transfer performance. Here, in order to suppress the influence of the cross-sectional area of the refrigerant flow path on the heat transfer coefficient in the pipe, the refrigerant mass velocity was made uniform for each outer diameter (φ4, φ5, φ7) of the refrigerant heat transfer tube.

  Moreover, in order to suppress the influence by a heat flux, it measured, adjusting the refrigerant | coolant temperature range (measurement temperature range) for every outer diameter of the refrigerant | coolant heat exchanger tube (divide the refrigerant | coolant inlet temperature-refrigerant | coolant outlet temperature into 5-6 area | regions). The water flow rate was adjusted so that the heat flux in each region was equal).

  The lubricating oil concentration (PAG oil concentration) in the refrigerant is determined by collecting the circulating refrigerant in a sampling container before the refrigerant inlet of the double-pipe heat exchanger, and the volume of the sampling container and the mass of the collected refrigerant. (By the so-called gravimetric method). The accuracy (control / measurement error) under the measurement conditions is about ± 0.3 ° C., pressure is about ± 0.1%, and the refrigerant mass velocity is relative to the values in Table 2 (the values are average values). Is about ± 0.4%, and the PAG oil concentration is about ± 0.1% by mass.

The in-tube heat transfer coefficient α was determined as follows.
Refrigerant inlet temperature T _r2 [unit: K], refrigerant outlet temperature T _r1 [unit: K], water pipe inlet temperature T _w1 [unit: K], outlet of water pipe for each refrigerant temperature range in the double pipe heat exchanger The temperature T _w2 [unit: K] and the mass flow rate G _{w of} water [unit: kg / s] are measured. From the representative temperature (average temperature T _w [unit: K]) calculated from the water inlet / outlet temperature, the constant pressure specific heat Cp _w of the water in the measurement section is obtained, and the heat is calculated from the relationship of the following equations (1) and (2). The flow rate q [unit: kW / m ² ] and the logarithmic average temperature difference ΔT _L [unit: K] are obtained.

Here, A is a heat exchange area (surface area of the refrigerant heat transfer tube in contact with water in the double-tube heat exchanger) [unit: m ² ].

here,

である。

It is.

Further, by dividing the heat flux q in logarithmic average temperature difference [Delta] T _L, the heat transfer coefficient of the double-pipe heat exchanger K ^{[Unit: kW / (m 2 K)} ] is calculated from the following equation (5) be able to.

On the other hand, from the representative temperature (average temperature T _w ) calculated from the inlet / outlet temperature of the water pipe, each physical property value (density, specific heat, viscosity, thermal conductivity λ _w ) of water at that temperature is determined, and the Prandtl number Pr is I want.

Further, the Reynolds number Re is obtained from the physical property value of water and the mass flow rate, and the heat transfer coefficient α _w [unit: kW / (m ² K)] of water can be calculated from the relationship of the following equation (6).

here,
d _e is (a value obtained by dividing 4 times the flow area at the wetted perimeter) equivalent diameter of the annular flow of the water [unit: m]
d _i is the inner diameter of the water pipe [unit: m]
OD is the outer diameter of the refrigerant heat transfer tube [unit: m]
It is.

The heat transfer coefficient α in the tube [unit: kW / (m ² K)] is the heat transfer rate K, the heat transfer coefficient α _{w of} water, the outer diameter OD of the refrigerant heat transfer tube, and the inner diameter ID of the refrigerant heat transfer tube [unit: m] can be calculated as in the following equation (7).

(Example 1, Comparative Example 1, Reference Example 1)
FIG. 6 is an evaluation result showing the relationship between the average refrigerant temperature and the heat transfer coefficient in the tube for Example 1, Comparative Example 1 (inner grooved tube) and Reference Example 1 (smooth tube). The average refrigerant temperature is an average temperature in each temperature region obtained by dividing the refrigerant inlet temperature to the refrigerant outlet temperature shown in Table 2 into 5 to 6 regions (average of the refrigerant inlet temperature and the refrigerant outlet temperature in the temperature region). is there. Moreover, the lubricating oil concentration (PAG oil concentration) in the refrigerant was 0.5 mass%.

  From FIG. 6, the heat transfer coefficient in the tube of the heat transfer tube according to the present invention of Example 1 is the heat transfer coefficient in the tube of the smooth tube (Reference Example 1) and the internally grooved tube (Comparative Example 1) in any temperature region. It turns out that it is higher. Further, the heat transfer coefficient in the tube is 1.5 times or more higher than the smooth tube (Reference Example 1) in each temperature region, and the overall average is about 1.7 times.

(Comparative Examples 2-3, Reference Examples 2-3)
For the internally grooved tubes (Comparative Examples 2 to 3) and smooth tubes (Reference Examples 2 to 3) having the specifications shown in Table 1, the heat transfer coefficient in the tube was measured in the same manner as described above. 7 and 8 show the average refrigerant temperature and the heat transfer coefficient in the tube when the PAG oil concentration is 0.5% by mass for Comparative Examples 2-3 (inner grooved tube) and Reference Examples 2-3 (smooth tube). It is the evaluation result which showed the relationship.

  In any heat transfer tube, such as a heat transfer tube (comparative example 2) having a refrigerant contact area expansion ratio of about 2.0 times, or a high torsion angle heat transfer tube (comparative example 3) that greatly improves the condensation performance of a fluorocarbon refrigerant. There is no heat transfer performance exceeding 1.5 times the smooth tube ratio. These are results that cannot be envisaged with chlorofluorocarbon refrigerants, and are considered to be the influence of compressor lubricant mixed in the carbon dioxide refrigerant.

(Example 1, Comparative Examples 4 to 6)
FIG. 9 shows the same evaluation as described above for the in-tube heat transfer coefficient of Example 1 and Comparative Examples 4 to 6 (inner grooved pipe), and unified the refrigerant contact area expansion ratio by about 1.8 times to H _f. FIG. In the figure, the tube heat transfer coefficient smooth tube ratio is the average of the tube heat transfer coefficient in each measured temperature range (average tube heat transfer coefficient), and the average tube heat transfer coefficient of the smooth tube (Reference Example 1). Divided by. Moreover, the lubricating oil concentration (PAG oil concentration) in the refrigerant was 0.5 mass%.

The result of FIG. 9 shows that when the compressor lubricating oil in the refrigerant is relatively large (for example, 0.5% by mass), the heat transfer tube H _f / ID and the tube heat transfer coefficient smooth tube ratio have a strong correlation. Represents. In Comparative Examples 4 to 6 (inner grooved tube), the heat transfer coefficient smooth tube ratio in the tube was small. The fins on the inner surface of the heat transfer tube (grooves on the inner surface of the heat transfer tube) were buried with the lubricating oil of the compressor mixed in the refrigerant. This is considered to be because the contribution of the heat transfer area increase (refrigerant contact area expansion ratio = approximately 1.8 times) is offset. From FIG. 9, it can be seen that at least H _f /ID≧0.1 is necessary to obtain the in-tube heat transfer coefficient smooth tube ratio of 1.5 or more.

In the internally grooved tube by the conventional rolling process, H _f / ID is considered to be about 0.07 to 0.08 at the maximum due to the restriction by the processing method. On the other hand, the heat transfer tube according to the present invention has the characteristics that H _f /ID≧0.1 and further the refrigerant contact area enlargement ratio is 1.5 times or more. An in-tube heat transfer coefficient can be obtained.

  FIG. 10 is a diagram showing the relationship between the PAG oil concentration in the refrigerant and the in-tube heat transfer coefficient smooth tube ratio (ratio with Reference Example 1) for the performance of Example 1 and Comparative Example 1 (inner grooved tube). is there. As can be seen from the figure, in the region where the PAG oil concentration is relatively high (for example, about 0.2% by mass or more), the heat transfer tube according to the present invention has clearly higher heat transfer performance than the conventional inner surface grooved tube. is doing.

It is a schematic block diagram of the heat pump type water heater in one embodiment of this invention. It is sectional drawing of the heat exchanger tube for refrigerant | coolants which concerns on 1st Embodiment which used the board | plate material as the fin material. It is sectional drawing of the heat exchanger tube for refrigerant | coolants which concerns on 2nd Embodiment which used the shaping | molding member as the fin material. It is sectional drawing of the heat exchanger tube for refrigerant | coolants which concerns on 3rd Embodiment which used the small diameter tube as the fin material. It is a schematic diagram of the double-pipe heat exchanger for evaluating heat transfer performance. It is the evaluation result which showed the relationship between average refrigerant | coolant temperature and a heat transfer coefficient in a pipe | tube about Example 1, the comparative example 1 (inner surface grooved pipe), and the reference example 1 (smooth pipe). It is the evaluation result which showed the relationship between average refrigerant | coolant temperature and the heat transfer coefficient in a pipe | tube about the comparative example 2 (inner surface grooved pipe) and the reference example 2 (smooth pipe). It is the evaluation result which showed the relationship between average refrigerant | coolant temperature and the heat transfer coefficient in a pipe | tube about the comparative example 3 (inner surface grooved pipe | tube) and the reference example 3 (smooth pipe | tube). It is the figure which unified the refrigerant _| coolant contact area expansion rate by 1.8 time, and arranged by _Hf / ID about the performance of Example 1 and Comparative Examples 4-6 (inner surface grooved pipe). It is the figure which showed the relationship between the PAG oil density | concentration and the heat transfer coefficient smooth tube ratio in a pipe | tube about the performance of Example 1 and Comparative Example 1 (inner surface grooved pipe). It is the figure which illustrated the correlation with a heat pump type heat exchange apparatus and the refrigerant | coolant used there.

Explanation of symbols

1: outer tube 2: fin material made of plate material 3: fin material made of molded member 4: small diameter tube 5: first space formed by outer tube and small diameter tube 6: second space 10 formed by small diameter tubes : Heat pump type water heater 11: Compressor 12: Gas cooler (water heat exchanger)
13: Pressure reducer 14: Heat absorber (evaporator)
15: Piping 20, 30, 40: Refrigerant heat transfer tube 50: Double tube heat exchanger 51: Refrigerant heat transfer tube 52: Water tube

Claims (15)

A refrigerant heat transfer tube used in a gas cooler of a heat pump heat exchange device using carbon dioxide as a refrigerant, wherein the refrigerant heat transfer tube includes an outer tube and a fin fixedly installed on the inner surface of the outer tube. The refrigerant heat transfer tube is characterized in that H _f / ID is 0.1 or more and 0.5 or less, where ID is the inner diameter of the outer tube and H _f is the height of the fin.   The refrigerant heat transfer tube according to claim 1, wherein the fin is made of a plate material.   The refrigerant heat transfer tube according to claim 1, wherein the fin is formed of a molded member.   The refrigerant heat transfer tube according to claim 1, wherein the fin is a hollow fin configured by a plurality of small-diameter tubes.   The refrigerant heat transfer tube according to any one of claims 1 to 4, wherein the fin has a thickness equal to or less than a thickness of the outer tube.   The refrigerant heat transfer tube according to any one of claims 1 to 5, wherein the fin is fixedly installed on an inner surface of the outer tube by fitting.   The refrigerant heat transfer tube according to any one of claims 1 to 6, wherein an expansion ratio of the refrigerant contact area due to the provision of the fins is 1.5 times or more.   A refrigerant heat transfer tube used in a gas cooler of a heat pump heat exchange device using carbon dioxide as a refrigerant, an outer tube, and a plurality of small-diameter tubes whose outer periphery is fixedly installed on the inner surface of the outer tube; A refrigerant heat transfer tube. The refrigerant heat transfer tube according to claim 8, wherein the small diameter tube has a height _Hf and an inner diameter of the outer tube ID, and _Hf / ID is 0.1 or more.   The refrigerant heat transfer tube according to claim 8 or 9, wherein the small-diameter tube has a thickness equal to or less than a thickness of the outer tube.   The refrigerant heat transfer tube according to any one of claims 8 to 10, wherein an expansion ratio of the refrigerant contact area due to the provision of the small-diameter tube is 1.5 times or more.   The said gas cooler is used for the heat pump type heat exchange apparatus which used polyalkylene glycol oil as lubricating oil of the compressor of a refrigerating cycle, The any one of Claims 1 thru | or 11 characterized by the above-mentioned. Heat transfer tube for refrigerant.   The carbon dioxide as the refrigerant contains 0.2% by mass or more of lubricating oil of a compressor constituting a refrigeration cycle in the heat pump heat exchange device. The heat exchanger tube for refrigerant | coolants of any one of these.   The refrigerant heat transfer tube according to any one of claims 1 to 13, wherein the gas cooler is a radiator of a heat pump heat exchange device.   A gas cooler comprising the refrigerant heat transfer tube according to any one of claims 1 to 14.

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