JP2013024543A - Heat exchanger, and heat pump heating device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat exchanger that can more efficiently heat a fluid and a heat pump heating device using the heat exchanger.SOLUTION: In the heat exchanger 10, which includes a fluid heat transfer tube 1 which permits a heating object fluid to flow, and refrigerant heat transfer tubes 2, 3 which permit refrigerants for providing heat to the fluid to flow, in which the refrigerants flow at or above critical pressures, the fluid heat transfer tube 1 and refrigerant heat transfer tubes 2, 3 are spirally formed contacting each other, and the fluid and refrigerants individually flow facing each other, radii of curvature of the refrigerant heat transfer tubes 2, 3 on an upstream side where the refrigerants flow are set larger than the radii of curvature of the refrigerant heat transfer tubes 2, 3 on a downstream side, bordering a site where a temperature difference between a temperature of the fluid and temperatures of the refrigerants measures minimum when the fluid and the refrigerants flow, in a neighborhood of a middle region between one end and the other end of the refrigerant heat transfer tubes.

Description

  The present invention relates to a heat exchanger and a heat pump type heating apparatus using the heat exchanger.

  For example, in a heat exchanger used in a heat pump type heating device (for example, a water heater) and an outdoor unit of an air conditioner (air conditioner), heat exchange is performed using a refrigerant. Specifically, the heat of the refrigerant is transmitted to the fluid by bringing the refrigerant to be heated into contact with a refrigerant having a large thermal energy through a material having high thermal conductivity. And by doing in this way, fluid can be heated.

  As a specific configuration of such a heat exchanger, for example, Patent Document 1 discloses a water heat transfer tube through which water flows, and a refrigerant heat transfer tube through which one or a plurality of refrigerants flow through one water heat transfer tube. Are in contact with each other in an overall shape such as a substantially cylindrical shape that is spirally wound together, and the water heat transfer tube is closely wound in the axial direction of the cylinder or the like and is spirally wound with almost no gap. A heat exchanger is described in which the shape is a cylinder or the like, and the refrigerant heat transfer tube is spirally wound around the outer periphery or the inner periphery of the water heat transfer tube or the like.

JP 2005-133999 A

  In the heat exchanger described in Patent Document 1, when operation is performed using a refrigerant having a critical pressure or higher, a portion where the temperature difference between the refrigerant temperature and the fluid temperature becomes small may occur. As a result, the efficiency of heat exchange with the fluid by the refrigerant may decrease.

  This invention is made | formed in view of the said subject, The objective is to provide the heat exchanger which can heat a fluid more efficiently, and a heat pump type heating apparatus using the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by changing the radius of curvature of the refrigerant heat transfer tube which is formed in a spiral shape and through which the refrigerant flows. I let you.

  ADVANTAGE OF THE INVENTION According to this invention, the heat exchanger which can heat a fluid more efficiently, and a heat pump type heating apparatus using the same can be provided.

It is a perspective view of the heat exchanger which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the heat exchanger which concerns on 1st Embodiment. It is sectional drawing of the fluid heat exchanger tube in the high temperature side spiral part in the heat exchanger which concerns on 1st Embodiment. It is sectional drawing of the fluid heat exchanger tube in the low temperature side spiral part in the heat exchanger which concerns on 1st Embodiment. It is a schematic diagram of the cycle of the water heater to which the heat exchanger according to the first embodiment is applied. It is a graph which shows the relationship between the refrigerant | coolant pressure and enthalpy in the heat exchanger which concerns on 1st Embodiment. It is a graph which shows the relationship between temperature and enthalpy in the heat exchanger which concerns on 1st Embodiment. It is process drawing at the time of assembling the heat exchanger which concerns on 1st Embodiment. It is a longitudinal cross-sectional view of the heat exchanger which concerns on 2nd Embodiment. It is the figure which expanded the F section in FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention (this embodiment) will be described with reference to the drawings. However, the present embodiment is not limited to the following contents, and may be arbitrarily changed within a range not impairing the gist of the present invention. Can be implemented.

[1. First Embodiment]
First, with reference to FIG.1 and FIG.2, the heat exchanger 10 which concerns on 1st Embodiment is demonstrated.
As shown in FIG. 1, the heat exchanger 10 includes a fluid heat transfer tube 1, an inner refrigerant heat transfer tube 2, and an outer refrigerant heat transfer tube 3. The fluid heat transfer tube 1, the inner refrigerant heat transfer tube 2, and the outer refrigerant heat transfer tube 3 are in contact with each other (line contact) as shown in FIG. That is, the outer refrigerant heat transfer tube 3 is in contact with the outside of the fluid heat transfer tube 1, and the outer refrigerant heat transfer tube 3 is in contact with the fluid heat transfer tubes 1 for two adjacent pitches (two in the sectional view shown in FIG. 2). Yes. On the other hand, the inner refrigerant heat transfer tube 2 is in contact with the inside of the fluid heat transfer tube 1. Note that, unlike the outer refrigerant heat transfer tube 3, the inner refrigerant heat transfer tube 2 is basically in contact with the fluid heat transfer tube 1 only at one location.

  Further, the upper half of the heat exchanger 10 thus formed is formed as a high temperature side spiral portion 4, and the lower half of the paper surface is formed as a low temperature side spiral portion 5. The curvature radius of the high temperature side spiral portion 4 is larger than the curvature radius of the low temperature side spiral portion 5.

  Here, the terms “high temperature side” and “low temperature side” will be described. As the “high temperature side” and the “low temperature side”, the refrigerant temperature starts at the point where the temperature difference between the fluid temperature and the refrigerant temperature is minimized (details will be described later, but the enthalpy H3 shown in FIG. 7 is the boundary). The higher temperature side is set as the “high temperature side”, and the lower temperature side is set as the “low temperature side”. That is, in the direction in which the refrigerant flows, the temperature difference gradually decreases in the high temperature side spiral portion 4, the temperature difference becomes minimum at the boundary, and the temperature difference from the boundary in the low temperature side spiral portion 5. After gradually increasing, it gradually decreases (see FIG. 7).

  In addition, although the kind in particular of the fluid and refrigerant | coolant applicable to the heat exchanger which concerns on this embodiment is not restrict | limited, in this embodiment, water shall be used as a fluid and the carbon dioxide shall be used as a refrigerant | coolant. In the inner refrigerant heat transfer tube 2 and the outer refrigerant heat transfer tube 3, a refrigerant having a critical pressure or higher flows.

Moreover, as shown in FIG. 2, the inner side refrigerant | coolant heat exchanger tube 2 is in contact with the fluid heat exchanger tube 1 for two adjacent pitches in the boundary part of the high temperature side spiral part 4 and the low temperature side spiral part 5. As shown in FIG. However, in the other portions, as described above, the inner refrigerant heat transfer tube 2 and the fluid heat transfer tube 1 are in contact with each other only at one place.
In the first embodiment, the upper half of the heat exchanger 10 is the high temperature side spiral portion 4, and the lower half is the low temperature side spiral portion 5. However, the specific lengths of these boundaries and the respective radii of curvature can be arbitrarily set according to the pressure of the refrigerant, the temperature of the fluid to be heated, the degree of temperature rise, and the like.

  Next, the state of the fluid in the fluid heat transfer tube 1 in the high temperature side spiral portion 4 and the low temperature side spiral portion 5 will be described with reference to FIGS. 3 and 4.

  Normally, the flow from the inlet to the outlet of the spiral structure increases the difference in flow velocity between the inside and outside of the fluid heat transfer tube 1 with respect to the center axis of the spiral structure as the radius of curvature of the spiral structure of the fluid heat transfer tube 1 decreases. Specifically, the inner flow velocity is slower than the outer flow velocity. And in the part with a quick flow, the energy which the fluid has is consumed for velocity energy, and a static pressure falls. Therefore, the static pressure is low on the outside, the static pressure is high on the inside, and a flow from the inside toward the outside is generated inside the pipe.

  Since the fluid has a property of flowing in the direction in which the pressure gradient is the largest, a flow (primary flow) is generated along the shortest path connecting from the inside to the outside. That is, the flow crosses the center of the flow path. This triggers a secondary flow from the outside toward the inside along the inner wall of the fluid heat transfer tube 1 to form a vortex. The speed of rotation of the vortex increases as the radius of curvature of the fluid heat transfer tube 1 decreases (ie, the static pressure difference increases). Therefore, the speed at the low temperature side spiral portion 5 (small curvature radius) shown in FIG. 4 is indicated by the thickness of the arrow as compared with the speed at the high temperature side spiral portion 4 (large curvature radius) shown in FIG. It will be big.

  When the rotation of the vortex becomes faster, heat transfer in the pipe is promoted, while the flow energy is consumed for the rotation of the vortex, thereby increasing the pressure loss. When the pressure loss increases, the temperature difference between the fluid and the refrigerant is reduced, so that the heat exchange efficiency is lowered (details will be described later with reference to FIGS. 6 and 7). Therefore, by increasing the curvature radius in the high temperature side spiral portion 4 and decreasing the curvature radius in the low temperature side spiral portion 5, the rotation of the vortex in the high temperature side spiral portion 4 is slowed down, and the pressure in the high temperature side spiral portion 4 is reduced. Loss can be reduced. As a result, an excessive decrease in the temperature difference can be prevented, thereby preventing a decrease in heat exchange efficiency.

  Thus, according to the heat exchanger 10, the pressure loss of the refrigerant flowing in the high temperature side pipe is reduced by making the radius of curvature of the high temperature side spiral structure larger than that of the low temperature side. When the refrigerant operates at a critical pressure or higher, the lowering rate of the refrigerant temperature accompanying the pressure drop in the flow direction of the refrigerant is higher on the high temperature side than on the low temperature side. For this reason, it is possible to prevent a decrease in the refrigerant temperature due to a decrease in pressure loss on the high temperature side, and locally increase the heat exchange temperature difference between the refrigerant and the fluid. Can be achieved.

  Next, with reference to FIG. 5, the structure of the water heater 100 as a heat pump type heating apparatus to which the heat exchanger 10 is applied will be described. In the heat exchanger 10, carbon dioxide is used as a refrigerant and water at about 10 ° C. is used as a fluid.

  The water heater 100 includes a compression means 6, an expansion means 7, an evaporation means 8, a heat exchanger 10, and piping connected to them. Specifically, the heat exchanger 10 is located downstream of the compression means 6, the expansion means 7 is further downstream of the heat exchanger 10, and the evaporation means 8 is further downstream of the expansion means 7. It is connected. The compression means 6 is connected to the downstream side of the evaporation means 8 and the fluid (water) is heated in the heat exchanger 10 by circulating the refrigerant (carbon dioxide) through these paths.

  The compression means 6 is a means for compressing the refrigerant flowing into the heat exchanger 10, and is constituted by, for example, a compressor. The expansion means 7 is a means for expanding the refrigerant discharged from the heat exchanger 10, and an arbitrary one such as an expansion valve, a capillary tube, or an expansion turbine can be used. Furthermore, the evaporating means 8 is means for exchanging heat between the refrigerant discharged from the expansion means 7 and the outside air, and an arbitrary one can be used.

  In the heat exchanger 10, as shown also in FIG. 1 etc., it flows in so that a refrigerant | coolant and a fluid may oppose. That is, as shown by the black arrows in FIG. 1, the fluid flows from the inlet of the fluid heat transfer tube 1 at the lower part of the paper surface and is discharged from the outlet of the upper part of the paper surface. On the other hand, the refrigerant flows in from the inflow port at the upper part of the paper surface and is discharged from the discharge port at the lower part of the paper surface, as indicated by the white arrow in FIG.

Next, specific refrigerant and fluid flows in the water heater 100 will be described in detail.
The refrigerant is compressed by the compression means 6 to be in a high temperature / high pressure state. Then, the refrigerant in a high temperature / high pressure state flows into the heat exchanger 10. The refrigerant flowing into the heat exchanger 10 transfers heat to the fluid, and the refrigerant itself loses heat and is discharged from the heat exchanger 10. The refrigerant discharged from the heat exchanger 10 is expanded by the expansion means 7 and the pressure is lowered. After heat is applied from the outside air by the evaporation means 8, the refrigerant flows into the compression means 6 again and is compressed again. Such a cycle is repeated. In addition, the fluid heated with the heat exchanger 10 is supplied to a demand end.

With reference to FIG.6 and FIG.7, the cycle of the refrigerant | coolant in the water heater 100 is demonstrated still in detail.
In the cycle shown in FIG. 6, heat exchange is performed in the heat exchanger 10 (temperature decrease) in (i) to (ii). In (ii) to (iii), the expansion means 7 expands the refrigerant (vaporization). Furthermore, in (iii) to (iv), heat is applied from the outside air to the refrigerant in the evaporating means 8 to heat it (however, the temperature is substantially constant). And a refrigerant | coolant is compressed in the compression means 6 by (iv)-(i) (temperature rising).

  In the water heater 100 that heats water (fluid) using carbon dioxide (refrigerant) as in the first embodiment, in order to boil water at about 10 ° C. to about 65 ° C. or higher, the compression means 6, heat A refrigerant pressure higher than the critical point is usually required between the exchanger 10 and the high pressure side (upstream side) of the expansion means 7. In the region where the refrigerant pressure is higher than the critical point pressure (critical pressure), there is a portion where the isotherm moves to the lower enthalpy side as the refrigerant pressure increases (for example, isotherm C).

  In (i)-(ii), when a conventional heat exchanger is applied, a pressure change like A (broken line) is shown. On the other hand, when the heat exchanger 10 is applied, the pressure loss of the high temperature side spiral portion 4 is low and the pressure loss of the low temperature side spiral portion 5 is relatively high as described above. Showing change. When compared with the isotherm C, the enthalpy at which the refrigerant temperature is C is smaller in the enthalpy H1 in B of the heat exchanger 10 than in the conventional enthalpy H2 in A.

  FIG. 7 shows a cycle in which the vertical axis represents temperature without changing the horizontal axis (enthalpy) in FIG. (I) and (ii) in FIG. 7 are the same as (i) and (ii) in FIG. That is, the refrigerant flows through (i) to (ii). Furthermore, fluid (E line) flows through X to Y. And the direction of the arrow of each line has shown the direction through which a refrigerant or fluid flows. Further, the C line shown in FIG. 6 is shown by a straight line.

  FIG. 7 clearly shows that the heat exchanger 10 (enthalpy H1) is lower than the conventional heat exchanger (enthalpy H2) as the enthalpy where the temperature of the refrigerant becomes C. Further, at the time of enthalpy H3, the temperature difference between the refrigerant temperatures T1 and T2 and the fluid temperature T3 is minimized. Since the difference between T1 and T3 is small, the heat exchange efficiency is lowered, and the temperature of the fluid is hardly increased. Therefore, in the conventional heat exchanger, in the vicinity of enthalpy H3, a long flow path and a long time are required in order to raise the temperature of the fluid.

  On the other hand, when the heat exchanger 10 is used, the pressure loss is reduced in the high temperature side spiral portion 4. Therefore, the temperature drop of the refrigerant becomes moderate (see line B in FIG. 7), and the temperature difference in the enthalpy H3 can be enlarged. Accordingly, the length of the flow path required to obtain the same fluid temperature is reduced, and as a result, the heat exchange efficiency can be improved without increasing the amount of heat exchanger material used.

  Next, an assembly method of the heat exchanger 10 will be described with reference to FIG. The fluid heat transfer tube 1 and the inner refrigerant heat transfer tube 2 are previously formed in a spiral shape (not shown). Then, as shown in FIG. 8A, the inner refrigerant heat transfer tube 2 is inserted into the fluid heat transfer tube 1 and then brazed to fix the fluid heat transfer tube 1 and the inner refrigerant heat transfer tube 2 (FIG. 8 ( b)). At this time, the tube at the lower end of the high temperature side spiral portion 4 of the inner refrigerant heat transfer tube 2 (the tube 2a in FIG. 8B) is connected to the tube of the high temperature side spiral portion 4 and the low temperature side spiral portion 5 of the fluid heat transfer tube 1. By designing so as to contact both of them, the inner refrigerant heat transfer tube 2 can be installed at a desired position simply by being inserted all the way into the fluid heat transfer tube 1. Therefore, the heat exchanger can be easily assembled as compared with the case where the curvature radius of the spiral structure is constant.

  Thereafter, as shown in FIG. 8 (c), the outer refrigerant heat transfer tube 3 is wound from the outside so as to come into contact with the fluid heat transfer tube 1 for two pitches, and brazed to fix the outer refrigerant heat transfer tube 3. The heat exchanger 10 can be assembled. In addition, since the assembly order does not relate to performance, the inner refrigerant heat transfer tube 2 may be inserted after the outer refrigerant heat transfer tube 3 is wound around the fluid heat transfer tube 1.

  In the first embodiment, the fluid heat transfer tube 1, the inner refrigerant heat transfer tube 2, and the outer refrigerant heat transfer tube 3 are round tubes. Even if it is configured in a rectangular shape, the performance can be improved. By configuring each tube using a square tube in this manner, the contact area between the tubes can be increased (surface contact), and heat exchange can be performed more efficiently.

[2. Second Embodiment]
Next, the heat exchanger 20 according to the second embodiment will be described with reference to FIGS. 9 and 10.
In the heat exchanger according to the present embodiment, the radius of curvature of the high temperature side refrigerant heat transfer tube is longer than the radius of curvature of the low temperature side refrigerant heat transfer tube. Therefore, the specific shape is not particularly limited as long as it has such a configuration. Therefore, in addition to the one shown in FIG. 1, for example, the heat exchanger 20 having the shape shown in FIG. 9 can be used.

  As shown in FIG. 9, the heat exchanger 20 is obtained by continuously changing the radius of curvature of the spiral structure with respect to the axial direction. In the heat exchanger 20, the fluid heat transfer tubes 1 for two adjacent pitches are in contact with all the inner refrigerant heat transfer tubes 2. The outer refrigerant heat transfer tube 3 is in contact with the adjacent two pitch fluid fluid transfer tubes 1. A gap space 15 is formed between the adjacent two-pitch fluid heat transfer tubes 1 and the outer refrigerant heat transfer tubes 3 (see FIG. 10).

  FIG. 10 shows a state in which the vicinity of the gap space 15 is enlarged (F portion). Since the thermal conductivity of air is usually not good, as shown in FIG. 10, in the heat exchanger 20, the gap space 15 is filled with wax (high heat transfer material). The wax can be filled through the groove 14 provided outside the fluid heat transfer tube 1 so as to communicate with the gap space 15.

  Although not shown, the gap space formed between the two fluid heat transfer tubes 1 and the one inner refrigerant heat transfer tube 3 is similarly filled with wax.

  In the heat exchanger 20, since the fluid heat transfer tubes 1 for two adjacent pitches are in contact with all the inner refrigerant heat transfer tubes 2, the number of contact portions of the tubes is larger than that of the heat exchanger 10. Therefore, the heat transfer performance is further improved. Further, when the heat exchanger 20 is assembled, the gap space 15 is filled with the high thermal conductivity wax (high heat transfer material) by pouring the wax into the space portion 15 through the groove portion 14, so that the heat transfer performance is improved. Further improve.

  The heat exchanger 20 can be assembled in the same manner as the heat exchanger 10 described with reference to FIG. That is, the fluid heat transfer tube 1, the inner refrigerant heat transfer tube 2, and the outer refrigerant heat transfer tube 3 are formed in a spiral shape in advance. And it can assemble easily by inserting the fluid heat-transfer tube 1 and the inner-side refrigerant heat transfer tube 2 from the upper part of the outer side refrigerant heat transfer tube 3 in this order. In addition, the groove part 14 can be formed in the fluid heat transfer tube 1 by forming notches or grooves at an arbitrary pitch before being spirally wound.

  As described above, the heat exchanger 20 has both the ease of assembly and the high heat transfer performance by continuously changing the curvature radius of the spiral structure.

[3. Example of change]
Although the heat exchanger according to the present embodiment has been described with reference to two specific examples, the heat exchanger according to the present embodiment is not limited to the above contents. Accordingly, the present invention can be arbitrarily changed and implemented without departing from the gist of the present invention.

  For example, in the heat exchangers 10 and 20, two pipes through which the refrigerant flows are provided, but only one pipe may be provided, or three or more pipes may be provided. In FIG. 1, the fluid flows in from the lower part of the paper and is discharged from the upper part of the paper. However, the direction in which the fluid flows may be reversed. The same applies to the refrigerant, and the radius of curvature may be changed corresponding to the direction in which the refrigerant flows.

  In this embodiment, water is used as the fluid and carbon dioxide is used as the refrigerant. However, the types of the fluid and the refrigerant are not limited to these.

  Furthermore, the direction in which the heat exchangers 10 and 20 are installed is not limited to the direction shown in FIG.

  Moreover, the heat pump type heating apparatus to which the heat exchanger according to the present embodiment is applied is not limited to a hot water heater, and may be appropriately determined according to the type of fluid.

  Furthermore, although the above-mentioned groove part is provided in the heat exchanger 20, it can also be provided in the heat exchanger 10 similarly. Therefore, a high heat transfer material (such as wax) can be filled in the gap space generated in the heat exchanger 10 in the same manner.

1 Fluid Heat Transfer Tube 2 Inner Refrigerant Heat Transfer Tube (Refrigerant Heat Transfer Tube)
3 Outer refrigerant heat transfer tube (refrigerant heat transfer tube)
4 High temperature side spiral part 5 Low temperature side spiral part 6 Compression means 7 Expansion means 8 Evaporation means 10 Heat exchanger 14 Groove part 15 Crevice space 20 Heat exchanger 100 Water heater (heat pump type heating device)

Claims (6)

A fluid heat transfer tube through which the fluid to be heated flows;
A refrigerant heat transfer tube through which a refrigerant that provides heat to the fluid flows, and
The refrigerant flows above the critical pressure,
The fluid heat transfer tube and the refrigerant heat transfer tube are each formed in a spiral shape and are in contact with each other,
The fluid and the refrigerant are heat exchangers that flow in opposition to each other,
When the fluid and the refrigerant flow, in the vicinity of the intermediate portion between the one end and the other end of the refrigerant heat transfer tube, the boundary is a point where the temperature difference between the temperature of the fluid and the temperature of the refrigerant is minimized. A heat exchanger, wherein a curvature radius of the upstream refrigerant heat transfer tube through which the refrigerant flows is configured to be larger than a curvature radius of the downstream refrigerant heat transfer tube. The heat exchanger according to claim 1, wherein the refrigerant heat transfer tube is in contact with the fluid heat transfer tubes for two adjacent pitches. The heat exchanger according to claim 2, wherein a radius of curvature of the refrigerant heat transfer tube continuously changes with respect to an axial direction of the spiral structure. The heat exchanger according to claim 2 or 3, wherein a gap space formed between the fluid heat transfer tube and the refrigerant heat transfer tube is filled with a heat transfer material. The fluid is water;
The heat exchanger according to any one of claims 1 to 4, wherein the refrigerant is carbon dioxide. The heat exchanger according to any one of claims 1 to 5,
Compression means for compressing the refrigerant flowing into the heat exchanger;
Expansion means for expanding the refrigerant discharged from the heat exchanger;
Evaporating means for exchanging heat between the refrigerant discharged from the expansion means and outside air;
A heat pump type heating device comprising:

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