JP2002122390A - Heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a heat exchange efficiency of a water heat exchanger of a hot water supply unit using a supercritical heat pump. SOLUTION: A refrigerant is supplied into many fine tubes 223 to heat- exchange the refrigerant with supplied hot water. Thus, a flowing speed of the refrigerant flowing through the tubes 223 is accelerated to increase a heat transfer rate between the refrigerant and the tubes 223 and a heat transfer area (contact area) of the refrigerant with the tube 223 is increased. Accordingly, the heat transfer rate and the heat transfer area (contact area) can be remarkably increased as compared with that of a simple double cylindrical heat exchanger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger for exchanging heat between fluids, and is applied to a water heater using a supercritical refrigeration cycle in which a refrigerant pressure on a high pressure side is higher than a critical pressure of the refrigerant. Effective.

[0002]

2. Description of the Related Art As a heat exchanger for exchanging heat between a heated high-temperature fluid and a low-temperature fluid, a heat exchanger comprising an inner cylinder and an outer cylinder as disclosed in Japanese Utility Model Registration Publication No. 2553583, for example. Heat exchangers having a double tube structure are well known.

[0003]

By the way, in a heat exchanger having a double tube structure, in order to improve the heat exchange efficiency, at least one of the inner cylinder and the outer cylinder is provided with irregularities such as projections and grooves. Means for increasing the heat transfer area and the heat transfer coefficient between the fluid and the tube are common.

[0004] However, the amount of improvement in heat exchange efficiency by the above means is already technically saturated, and it is difficult to further improve the heat exchange efficiency by means similar to the above means.

In view of the above, an object of the present invention is to improve the heat exchange efficiency by a new means different from the conventional one.

[0006]

In order to achieve the above object, according to the present invention, the first fluid circulates and an inner diameter equivalent dimension is approximately 0.2 mm or more.
A large number of first tubes (223) of 1 mm or less;
A second tube (2) through which a second fluid that exchanges heat with the fluid flows
21), and the two tubes (223, 221) are arranged at positions where they can exchange heat with each other.

As a result, the flow rate of the fluid flowing through the first tube (223) is increased, the heat transfer coefficient between the first fluid and the first tube (223) is increased, and the first fluid and the first fluid are separated. The heat transfer area (contact area) with the first tube (223) increases.

Accordingly, the heat transfer coefficient and the heat transfer area (contact area) can be greatly increased as compared with a simple double-cylindrical heat exchanger.
It is possible to significantly improve the heat exchange efficiency.

According to the second aspect of the present invention, the first fluid flows, and the dimension corresponding to the inner diameter is about 0.2 mm or more.
mm and a first tube (2) in which the fine tube (223) is housed.
23) and a second tube (221) that is arranged coaxially with the first tube (222) while the second fluid that exchanges heat with the first fluid flows.

As a result, the flow rate of the fluid flowing through the fine tube (223) is increased, the heat transfer coefficient between the first fluid and the fine tube (223) is increased, and the first fluid and the fine tube (223) are increased. The heat transfer area (contact area) with (223) increases.

Therefore, the heat transfer coefficient and the heat transfer area (contact area) can be greatly increased as compared with a simple double-cylindrical heat exchanger.
It is possible to significantly improve the heat exchange efficiency.

According to the third aspect of the present invention, the first fluid flows, and the dimension corresponding to the inner diameter is about 0.2 mm or more.
mm and a first tube (2) in which the fine tube (223) is housed.
22), and a second tube (221) through which a second fluid that exchanges heat with the first fluid flows.
22, 221) are characterized in that they are spirally wound in contact with each other.

Accordingly, the flow velocity of the fluid flowing through the fine tube (223) is increased, the heat transfer coefficient between the first fluid and the fine tube (223) is increased, and the first fluid and the fine tube (223) are increased. The heat transfer area (contact area) with (223) increases.

Therefore, the heat transfer coefficient and the heat transfer area (contact area) can be greatly increased as compared with a simple double-cylindrical heat exchanger.
It is possible to significantly improve the heat exchange efficiency.

The first and second tubes (222, 22)
Since 1) is spirally wound in contact with each other,
It is possible to improve the heat exchange efficiency while reducing the size of the heat exchanger.

According to the fourth aspect of the present invention, the first fluid circulates and the dimension corresponding to the inner diameter is about 0.2 mm or more.
mm and a second tube (22) through which a second fluid that exchanges heat with the first fluid flows.
1), wherein the first tube (223) is wound around the outer wall of the second tube (221).

As a result, the flow rate of the fluid flowing through the first tube (223) is increased, the heat transfer coefficient between the first fluid and the first tube (223) is increased, and the first fluid and the first fluid are separated. The heat transfer area (contact area) with the first tube (223) increases.

Therefore, the heat transfer coefficient and the heat transfer area (contact area) can be greatly increased as compared with a simple double-cylindrical heat exchanger.
It is possible to significantly improve the heat exchange efficiency.

Further, since the first fluid and the second fluid are orthogonally opposed flows, the heat exchange efficiency can be improved.

Incidentally, the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment)
FIG. 1 is an external view of a water heater 100 and FIG. 2 is a schematic diagram of the water heater 100 in which the heat exchanger according to the present invention is applied to a household water heater. In FIG. 2, reference numeral 200 (enclosed by a two-dot chain line) denotes a supercritical heat pump cycle (hereinafter, abbreviated as a heat pump) that heats hot water and generates hot water having a high temperature (about 85 ° C. in the present embodiment). is there.

The supercritical heat pump cycle is
A heat pump cycle in which the refrigerant pressure on the high pressure side is equal to or higher than the critical pressure of the refrigerant, for example, a heat pump cycle using carbon dioxide, ethylene, ethane, nitrogen oxide, or the like as a refrigerant.

Reference numeral 300 denotes a plurality of heat retention tanks for keeping the hot water heated by the heat pump 200 warm and stored. Each of the heat retention tanks 300 is arranged in parallel with the flow of the hot water (hot water). ing.

In FIG. 2, reference numeral 210 denotes a refrigerant (in this embodiment,
The compressor 210 is a compressor that sucks and compresses carbon dioxide). The compressor 210 is an electric compressor in which a compression mechanism (not shown) that sucks and compresses refrigerant and an electric motor (not shown) that drives the compression mechanism are integrated. Machine.

Reference numeral 220 denotes a water heat exchanger (radiator) which applies the heat exchanger according to the present embodiment and exchanges heat between the refrigerant discharged from the compressor 210 and hot water. Inside, the flow of hot water and the flow of refrigerant are opposed to each other. The detailed structure of the water heat exchanger 220 will be described later.

Reference numeral 230 denotes an electric expansion valve (decompressor) for reducing the pressure of the refrigerant flowing out of the water heat exchanger 220.
Evaporates refrigerant flowing out of an electric expansion valve 230 (hereinafter, abbreviated as expansion valve 230) to absorb heat in the atmosphere into the refrigerant, and to accumulate the accumulator 250 described later.
This is an evaporator that discharges the refrigerant toward (the suction side of the compressor 210).

The reference numeral 250 designates a compressor which separates the refrigerant flowing out of the evaporator 240 into a gas-phase refrigerant and a liquid-phase refrigerant and
10 and the heat pump 200
It is an accumulator that stores excess refrigerant inside.

Reference numeral 260 denotes a blower (blowing air amount adjusting means) which blows air (outside air) to the evaporator 240 and can adjust the blowing amount. The blower 260, the compressor 210 and the expansion valve 230 are described later. Is controlled by an electronic control unit (ECU) 270 based on the detection signals of the respective sensors.

Reference numeral 271 denotes a refrigerant temperature sensor (refrigerant temperature detecting means) for detecting the temperature of the refrigerant flowing out of the water heat exchanger 220. Reference numeral 272 denotes a refrigerant temperature sensor for detecting the temperature of hot water flowing into the water heat exchanger. It is a first hot water temperature sensor (first hot water temperature detecting means).

Reference numeral 273 denotes a refrigerant pressure sensor (refrigerant pressure detecting means) for detecting the pressure of the refrigerant flowing out of the water heat exchanger 220 (the refrigerant pressure on the high pressure side).
It is a second hot water temperature sensor (second hot water temperature detecting means) for detecting the temperature of hot water flowing out of the water heater 20. The detection signals of the sensors 271 to 274 are input to the ECU 270.

Here, the refrigerant pressure on the high pressure side refers to the compressor 2
10 means the pressure of the refrigerant present in the refrigerant passage from the discharge side of the expansion valve 230 to the inflow side of the expansion valve 230.
It is substantially equal to 0 discharge pressure (the internal pressure of the water heat exchanger 220). On the other hand, the refrigerant pressure on the low pressure side refers to the pressure of the refrigerant existing in the refrigerant passage from the outlet side of the expansion valve 230 to the suction side of the compressor 210, and the pressure is the suction pressure of the compressor 210 (evaporator 240 Internal pressure).

Reference numeral 400 denotes an electric water pump (hereinafter abbreviated as a pump) for supplying (circulating) hot water to the water heat exchanger 220 and adjusting the amount of hot water. This is a shut-off valve for preventing tap water supplied from a not-shown) from flowing into the water heat exchanger 220. The pump 400 and the shut-off valve 410 are also EC
It is controlled by U270.

Next, the water heat exchanger 220 will be described.

The water heat exchanger 220 is, as shown in FIG.
Copper water tube (second tube) 221 through which hot water (water) flows, and refrigerant tube (first tube) 22 through which a refrigerant that exchanges heat with hot water (heats hot water) flows
The water tube 221 is formed coaxially with the refrigerant tube 222 as shown in FIG.
22 is arranged outside.

By the way, the refrigerant flowing through the refrigerant tube 222 does not flow directly through the refrigerant tube 222, but flows indirectly through the many fine tubes 223 housed in the refrigerant tube 222. Flows through the refrigerant tube 222. The refrigerant tube 22
2 and the fine tube 223 are arranged in a state where they are in close contact with each other (thermally contact).

Here, the fine tube 223 has a sufficiently small cross-sectional area as compared with the water tube 221 and the refrigerant tube 222, and more specifically, has a size equivalent to an inner diameter of 0.2.
mm or more and 1 mm or less (0.5 mm in this embodiment)
Say tube. The equivalent inner diameter refers to a diameter when the passage area is converted into a circle. As in the present embodiment, in a tube having a circular cross section, the inner diameter is equal to the equivalent inner diameter.

Incidentally, the refrigerant tube 2 according to the present embodiment
22 is a first refrigerant tube 22 made of copper which comes into contact with hot water
2a and a second refrigerant tube 222b made of copper in contact with the fine tube 223. The first and second refrigerant tubes 222a are formed by forming a groove extending in the longitudinal direction on the inner wall thereof. Refrigerant tube 222
a, a leakage detection passage 222c that guides the refrigerant leaked from the fine tube 223 between the a and 222b to the outside of the water heat exchanger 220.
Is provided.

The leak detecting passage 222c prevents the refrigerating machine oil (lubricating oil of the compressor 210) contained in the refrigerant leaked from the fine tube 223 from mixing with the hot water. A leak sensor (not shown) for detecting the leaked refrigerant (lubricating oil) is provided downstream (lower end) of the passage 222c.

Then, the refrigerant (lubricating oil) is detected by the leak sensor.
Is detected, the refrigerant side circuit is opened to the atmosphere to release the refrigerant safely.

Next, the features of this embodiment will be described.

According to this embodiment, since the refrigerant and the hot water are heat-exchanged by circulating the refrigerant through the many fine tubes 223, the flow velocity of the refrigerant flowing through the fine tubes 223 increases. Then, the refrigerant and the fine tube 22
3 and the heat transfer area (contact area) between the refrigerant and the fine tube 223 increases.

Therefore, the heat transfer coefficient and the heat transfer area (contact area) can be greatly increased as compared with a simple double-cylindrical heat exchanger.
It is possible to significantly improve the heat exchange efficiency.

FIG. 5 is a test result showing the relationship between the heat exchange performance and the diameter of the fine tube 223. Then, as is clear from FIG. 5, the heat exchange performance is maximized when the diameter is 0.2 mm, and the heat exchange performance decreases at the peak of 0.2 mm. Therefore, in the present embodiment, the equivalent diameter is set to 0.2 mm (preferably, 0.5 mm) or more in consideration of foreign matter clogging the fine tube 223.

By the way, a refrigerant in a supercritical state is circulating in the fine tube 223. In the supercritical state, the density of the refrigerant is high and the fluidity of the refrigerant is low. The heat transfer coefficient with the fine tube 223 is reduced.

On the other hand, in the present embodiment, as described above, the heat transfer coefficient and the heat transfer area (contact area) are increased by flowing the supercritical refrigerant through the fine tube 223. , The heat exchanger on the high pressure side of the supercritical heat pump cycle (in this embodiment, the water heat exchanger 22
0) is effective.

The equivalent diameter of the fine tube 223 is
Since the pressure is 0.2 mm or more and 1 mm or less, the stress generated in the fine tube 223 can be reduced even when the supercritical high-pressure refrigerant flows through the fine tube 223. Therefore, since the pressure resistance of the water heat exchanger 220 can be improved, the water heat exchanger 220 (water heater 10
0) The durability can be improved.

(Second Embodiment) In the first embodiment, hot water is circulated outside the refrigerant flow passage. However, in this embodiment, as shown in FIG. 6, hot water is supplied inside the refrigerant flow passage. It is made by circulating water.

(Third Embodiment) In the above-described embodiment, the part through which the refrigerant flows and the part through which the hot water flows are divided into two parts. In this embodiment, as shown in FIGS. The refrigerant and the hot water are circulated in three or more parts.

In this embodiment, the refrigerant circulates through the fine tube 223 and the other sections (FIGS. 7 and 8).
The hot water flows in the white part of ().

(Fourth Embodiment) In the above embodiment, the first and second tubes 221 and 222 and the fine tube 223 are used.
Are arranged in a substantially straight line so that the axial directions are parallel to each other. However, in the present embodiment, as shown in FIG.
1, 222 are brought into contact with each other so as to overlap each other,
The first and second tubes 221 and 222 are spirally wound as shown in FIG. 10 by regarding the one 224 contacted so as to overlap with each other as one tube.

Accordingly, the heat exchange capacity of the water heat exchanger 220 can be increased while the water heat exchanger 220 is downsized.

(Sixth Embodiment) In this embodiment, as shown in FIG. 11, a fine tube 223 is wound around the outer wall of a first tube 221.

Each of the micro tubes 225a and 225b is connected to an end of the micro tube 223 in the longitudinal direction.
3 and a header tank 225.
“a” distributes and supplies the refrigerant to each fine tube 223, and the header tank 225b collects and collects the refrigerant that has finished heat exchange.

Then, the header tanks 225a and 225b
Are separated into a plurality of spaces by a separator (not shown), hot water flows into the first tube 221 from the direction of FIG. 11A, and refrigerant flows into the header tank 225a from the direction of FIG. 11B. By flowing the hot water flow and the refrigerant flow, the heat exchange efficiency is improved by making the flow of the hot water flow orthogonal to the flow of the refrigerant.

Incidentally, in this embodiment, the fine tube 2
23 are independent one by one, but the present embodiment is not limited to this, and a large number of extruded tubes such as a multi-hole tube used for a condenser of a vehicle air conditioner are used. May be integrated.

(Other Embodiments) In the above-described embodiment, the refrigerant flows through the fine tube 223. On the contrary, hot water may flow through the fine tube 223.

As shown in FIG. 12, a fine tube 223 may be disposed in the first tube 221 and hot water or the like may be flowed into the fine tube 223.

In the above-described embodiment, the present invention is applied to the water heat exchanger of the heat pump water heater, but the present invention is not limited to this, and can be applied to other uses. Incidentally, a heat exchanger of the type shown in FIG. 12 is applied to a so-called internal heat exchanger that exchanges heat between a high-pressure side refrigerant (a refrigerant before being decompressed) and a refrigerant sucked into a compressor. Effective.

Further, in the above embodiment, the first,
Although the two tubes 221 and 222 and the fine tube 223 are configured, the present invention is not limited to this, and may be formed of other materials such as an aluminum alloy, iron, and stainless steel.

Further, in the above-described embodiment, the refrigerant tube 222 has a double structure and the leak detection passage 222c is provided. However, the present invention is not limited to this. The space inside the tube 222 may be used as the leak detection passage 222c.
Further, the leakage detection passage 222c may be omitted.

[Brief description of the drawings]

FIG. 1 is an external view of a water heater according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a water heater according to the first embodiment of the present invention.

FIG. 3 is an external view of the water heat exchanger according to the first embodiment of the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a graph showing a relationship between a diameter of a fine tube and heat exchange performance in the water heat exchanger according to the first embodiment of the present invention.

FIG. 6 is a sectional view of a water heat exchanger according to a second embodiment of the present invention.

FIG. 7 is a sectional view of a water heat exchanger according to a third embodiment of the present invention.

FIG. 8 is a sectional view of a water heat exchanger according to a third embodiment of the present invention.

FIG. 9 is a sectional view of a water heat exchanger according to a fourth embodiment of the present invention.

FIG. 10 is an external view of a water heat exchanger according to a fourth embodiment of the present invention.

FIG. 11 is a perspective view of a water heat exchanger according to a fourth embodiment of the present invention.

FIG. 12 is a cross-sectional view of a water heat exchanger according to another embodiment of the present invention.

[Explanation of symbols]

221: water tube (second tube), 222: refrigerant tube (first tube), 223: fine tube.

Continued on the front page (72) Inventor Takeshi Okinoya 1-1-1 Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (Reference) 3L103 AA36 BB43 CC02 CC40 DD05 DD09 DD38

Claims (4)

[Claims] 1. A first fluid circulates, and a large number of first tubes (223) having an inner diameter equivalent size of approximately 0.2 mm or more and 1 mm or less, and a second fluid that exchanges heat with the first fluid circulates. A heat exchanger, comprising: a second tube (221) that performs heat exchange between the two tubes (223, 221). 2. A plurality of fine tubes (223) having an inner diameter equivalent size of about 0.2 mm or more and 1 mm or less while a first fluid circulates, and a first tube containing the fine tubes (223) therein. It has a tube (223) and a second tube (221) that is arranged coaxially with the first tube (222) while a second fluid that exchanges heat with the first fluid flows. And heat exchanger. 3. A plurality of fine tubes (223) having an inner diameter equivalent dimension of about 0.2 mm or more and 1 mm or less while a first fluid flows therein, and a first tube containing the fine tubes (223) therein. A tube (222), and a second tube (221) through which a second fluid that exchanges heat with the first fluid flows, wherein the first and second tubes (222, 221) spiral while contacting each other. A heat exchanger characterized by being wound in a shape. 4. The first fluid flows, and a large number of first tubes (223) having an inner diameter equivalent dimension of about 0.2 mm or more and 1 mm or less, and a second fluid that exchanges heat with the first fluid flows. And a second tube (221) that performs the second tube (22).
A heat exchanger wound around the outer wall of 1).