JP2003262434A - Evaporator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To fully exhibit the capacity of an evaporator for an ejector cycle. <P>SOLUTION: The total refrigerant passage cross-sectional area on the refrigerant inlet 32 side out of a refrigerant passage 31a is made smaller than that on the refrigerant outlet 33 side. A sharp decrease in flow velocity of a refrigerant can thereby be prevented, so that a considerable lowering of a heat transfer rate of the refrigerant and a tube can be prevented to fully exhibit the capacity of the evaporator 30. Furthermore, since the decrease of flow velocity of the refrigerant can be prevented, the refrigerator oil is prevented from sticking to the internal wall of the tube 31, and in its turn, a sufficient quantity of refrigerator oil can be returned to a compressor. The lowering of the heat transfer rate caused by the refrigerator oil sticking to the internal wall can thereby be prevented while preventing the occurrence of defectiveness such as seizure of the compressor. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor compression refrigerator for moving heat on a low temperature side to a high temperature side, converting expansion energy into pressure energy while decompressing and expanding a refrigerant to reduce suction pressure of the compressor. The present invention relates to an evaporator applied to an ejector cycle, which is a vapor compression refrigerator having an ejector to be raised.

[0002]

2. Description of the Related Art In an ejector cycle, as shown in, for example, Japanese Unexamined Patent Publication No. 6-11197, the refrigerant flowing out of the ejector flows into a gas-liquid separator and enters the gas-liquid separator. The liquid-phase refrigerant separated by this is supplied to the evaporator, and the gas-phase refrigerant separated by the gas-liquid separator is sucked into the compressor, so that almost only liquid-phase refrigerant flows into the evaporator of the ejector cycle. To do.

Further, since the refrigerant changes from the liquid phase state to the vapor phase state in the evaporator, if the refrigerant passage cross-sectional area is the same between the refrigerant inlet side and the refrigerant outlet side of the evaporator, the refrigerant flow velocity becomes the refrigerant inlet side. And the refrigerant outlet side are significantly different, and the heat transfer coefficient between the refrigerant and the tube on the refrigerant inlet side and the heat transfer coefficient between the refrigerant and the tube on the refrigerant outlet side are different. Can not be demonstrated to.

In view of the above points, it is an object of the present invention to fully exert its capacity in an evaporator for an ejector cycle.

[0005]

In order to achieve the above object, the present invention is, in the invention as set forth in claim 1, in which expansion energy is converted into pressure energy while decompressing and expanding the refrigerant, and suction pressure of the compressor. An evaporator applied to a vapor compression refrigerator having an ejector (40) that raises
Of the refrigerant passages (31a) from the refrigerant inlet (32) to the refrigerant outlet (33), the total refrigerant passage sectional area on the refrigerant inlet (32) side is smaller than the total refrigerant passage sectional area on the refrigerant outlet (33) side. Is characterized by.

In the evaporator, since the liquid-phase refrigerant changes to the gas-phase refrigerant, the refrigerant volume on the refrigerant outlet (33) side becomes larger than the refrigerant volume on the refrigerant inlet (32) side. Therefore, when it is assumed that the mass flow rate of the refrigerant at the refrigerant inlet (32) and the refrigerant outlet (33) is substantially constant, the refrigerant inlet (32)
Side and the refrigerant outlet (33) side have the same refrigerant passage cross-sectional area, the refrigerant flow velocity on the refrigerant inlet (32) side is significantly lower than the refrigerant flow velocity on the refrigerant outlet (33), and the refrigerant inlet (32) On the side, the heat transfer coefficient between the refrigerant and the inner wall of the refrigerant passage (31a) is greatly reduced.

On the other hand, in the present invention, the refrigerant passage (3
1a) is configured such that the total refrigerant passage cross-sectional area on the refrigerant inlet (32) side is smaller than the total refrigerant passage cross-sectional area on the refrigerant outlet (33) side, so that the refrigerant flow velocity on the refrigerant inlet (32) side. Can be prevented from being greatly reduced, and the heat transfer coefficient between the refrigerant and the inner wall of the refrigerant passage (31a) on the refrigerant inlet (32) side can be prevented from being greatly decreased. Therefore, the capacity of the evaporator can be fully exerted.

Further, in the present invention, the total refrigerant passage sectional area on the refrigerant inlet (32) side of the refrigerant passage (31a) is made small to prevent the refrigerant flow velocity from decreasing.
It is possible to prevent refrigerating machine oil from adhering to the inner wall of the refrigerant passage (31a).

Furthermore, since a sufficient amount of refrigerating machine oil can be returned to the compressor of the vapor compression refrigerating machine, it is possible to prevent problems such as seizure of the compressor from occurring.
It is possible to prevent the heat transfer coefficient from decreasing due to the refrigerating machine oil adhering to the inner wall.

The total cross-sectional area of the refrigerant passage (31a) on the refrigerant inlet (32) side is defined by the refrigerant outlet (3).
When the structure is made smaller than the total cross-sectional area of the refrigerant passage on the 3) side, the refrigerant inlet (32) side of the tubes (31) constituting the refrigerant passage (31a) is defined as in the invention according to claim 2. The passage cross-sectional area of the tube (31) may be smaller than the passage cross-sectional area on the refrigerant outlet (33) side.

Further, as in the invention described in claim 3,
A plurality of tubes (3 forming the refrigerant passage (31a)
1) tube (3) on the refrigerant inlet (32) side
The number of 1) may be smaller than the number of tubes (31) on the refrigerant outlet (33) side.

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

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION (First Embodiment)
The ejector cycle according to the present invention is applied to a vehicle air conditioner, FIG. 1 is a schematic view of the ejector cycle, and FIG. 2A is an external perspective view of an evaporator 30 according to the present embodiment. 2 (b) is a schematic diagram showing a refrigerant flow in the evaporator 30. As shown in FIG.

In FIG. 1, a compressor 10 is a well-known variable displacement type compressor that receives power from a running engine to suck and compress a refrigerant, and a radiator 20 discharges the refrigerant and the outdoor air. Is a high-pressure side heat exchanger for exchanging heat to cool the refrigerant.

By the way, in this embodiment, since Freon is used as the refrigerant, the refrigerant pressure in the radiator 20 is equal to or lower than the critical pressure of the refrigerant, and the radiator 20 condenses the refrigerant.

The evaporator 30 is a low-pressure side heat exchanger that cools the air blown out into the room by evaporating the refrigerant by evaporating the liquid phase refrigerant by exchanging heat between the air blowing out into the room and the liquid phase refrigerant. As shown in FIG. 2A, the evaporator 30 includes a plurality of tubes 31 that form a refrigerant passage.
Together with meandering, the refrigerant passage 31a (see FIG. 2) from the refrigerant inlet 32 to the refrigerant outlet 33 when viewed macroscopically.
The thick arrow in (b) is configured to make a U-turn at least once.

Specifically, as shown in FIG. 2B, a plurality of tubes 31 communicating with an inlet side header tank 34 provided with a refrigerant inlet 32 and an outlet side header tank provided with a refrigerant outlet 33. Multiple tubes 3 communicating with 35
1, and a header tank 36 that communicates with all the tubes 31 and turns the refrigerant passage 31aU when viewed macroscopically,
In addition, thin plate-like fins 37 that increase the heat transfer area with air are mechanically joined to the outer surface of the tube 31 by brazing or expanding, and in this embodiment, the refrigerant inlet 31 of the refrigerant passage 31a. The number of tubes 31 communicating with the inlet-side header tank 34 is equal to the number of tubes 31 communicating with the inlet-side header tank 34 so that the total refrigerant passage sectional area on the 32 side is smaller than the total refrigerant passage sectional area on the refrigerant outlet 33 side. It is less than the number of.

Further, an oil repellent film having oil repellency is formed on the inner wall surface of the tube 31, and this oil repellent film is made of a material having a surface tension smaller than that of refrigerating machine oil. In, the oil repellent film 31a is formed of silicon resin or fluorine resin.

Further, in FIG. 1, the ejector 40 expands the refrigerant under reduced pressure to suck the vapor phase refrigerant evaporated in the evaporator 30, and converts the expansion energy into pressure energy to raise the suction pressure of the compressor 10. It is what makes me.

As shown in FIG. 3, the ejector 40 converts the pressure energy of the inflowing high-pressure refrigerant into velocity energy to decompress and expand the refrigerant in an isentropic manner. While sucking the vapor phase refrigerant evaporated in the evaporator 30 by the refrigerant flow, the mixing section 42 that mixes with the refrigerant flow injected from the nozzle 41, and the refrigerant injected from the nozzle 41 and the refrigerant sucked from the evaporator 30 The diffuser 43 and the like are configured to increase the pressure of the refrigerant by converting velocity energy into pressure energy while mixing.

Incidentally, in the present embodiment, in order to accelerate the velocity of the refrigerant ejected from the nozzle 41 to a speed higher than the sonic velocity, a Laval nozzle having a throat portion with the smallest passage area in the middle of the passage (Fluid Engineering (The University of Tokyo Press) (See) is adopted.

In the mixing section 42, the nozzle 41
Since the sum of the momentum of the refrigerant flow injected from the and the momentum of the refrigerant flow sucked from the evaporator 30 to the ejector 40 is stored, the static pressure of the refrigerant also rises in the mixing section 42. On the other hand, in the diffuser 43, the dynamic pressure of the refrigerant is converted into the static pressure by gradually increasing the passage cross-sectional area, so in the ejector 40, the refrigerant pressure is increased by both the mixing section 42 and the diffuser 43. . Therefore, the mixing section 42 and the diffuser 43 are generically called a boosting section.

Further, in FIG. 1, the gas-liquid separator 50 receives the refrigerant flowing out of the ejector 40 and separates the inflowing refrigerant into a gas-phase refrigerant and a liquid-phase refrigerant to store the refrigerant therein. The gas-phase refrigerant outlet of the gas-liquid separator 50 is connected to the suction side of the compressor 10, and the liquid-phase refrigerant outlet is connected to the inflow side of the evaporator 30.

FIG. 4 is a p-h diagram showing the macro operation of the ejector cycle as a whole. Since the macro operation is the same as that of the known ejector cycle, in the present embodiment, the ejector cycle as a whole is operated. The description of the macro operation is omitted. By the way, the symbol shown by ● in FIG.
It shows the state of the refrigerant at the symbol position shown by ● shown in FIG.

Next, the features of this embodiment will be described.

In the evaporator 30, since the liquid-phase refrigerant is changed to the vapor-phase refrigerant, the refrigerant volume on the refrigerant outlet 33 side becomes larger than the refrigerant volume on the refrigerant inlet 32 side. Therefore, when it is assumed that the mass flow rate of the refrigerant between the refrigerant inlet 32 and the refrigerant outlet 33 is substantially constant, the refrigerant inlet 32 side and the refrigerant outlet 3
If the refrigerant passage cross-sectional area is the same on the 3rd side, the refrigerant inlet 32
The flow velocity of the refrigerant on the side of the coolant is significantly lower than the flow velocity of the refrigerant on the side of the coolant outlet 33, and the heat transfer coefficient between the coolant and the tube is significantly reduced on the side of the coolant inlet 32.

On the other hand, in this embodiment, the total refrigerant passage sectional area on the refrigerant inlet 32 side of the refrigerant passage 31a is smaller than the total refrigerant passage sectional area on the refrigerant outlet 33 side. It is possible to prevent the refrigerant flow velocity on the refrigerant inlet 32 side from being greatly reduced, and to prevent the heat transfer coefficient between the refrigerant and the tube from being greatly reduced on the refrigerant inlet 32 side. Therefore, the capacity of the evaporator 30 can be fully exerted.

The evaporator for a vapor compression refrigerator (hereinafter referred to as an expansion valve cycle), which depressurizes the refrigerant isosterically by a pressure reducing means such as a temperature type expansion valve, is also applicable.
Similar to the ejector cycle, although the heat transfer coefficient decreases on the refrigerant inlet side, in the expansion valve cycle, the refrigerant in the gas-liquid two-phase state depressurized by the expansion valve flows into the evaporator,
Moreover, about 80% of the flowing refrigerant is a vapor phase refrigerant,
Since the remaining about 20% is the liquid-phase refrigerant, the total refrigerant passage cross-sectional area on the refrigerant inlet side is the same as that of the evaporator for the expansion valve cycle. Even if it is configured to be smaller, a sufficient effect commensurate with the development cost cannot be obtained.

On the other hand, in the ejector cycle,
Since almost only the liquid-phase refrigerant flows into the evaporator 30, it is possible to obtain a large effect as compared with the expansion valve cycle, that is, a sufficient effect commensurate with the development cost.

By the way, the refrigerating machine oil that lubricates the interior of the compressor 10 is mixed with the refrigerant and supplied to the compressor 10.
When the flow velocity of the refrigerant in the evaporator 30 is low, the refrigerating machine oil adheres to the inner wall of the tube 31, so that a sufficient amount of the refrigerating machine oil cannot be returned to the compressor 10, causing a problem such as seizure of the compressor 10. May occur.

On the other hand, in this embodiment, the total refrigerant passage cross-sectional area on the refrigerant inlet 32 side of the refrigerant passage 31a is made small to prevent the refrigerant flow velocity from decreasing, so that the refrigerating machine oil is cooled by the tube 31. Can be prevented from adhering to the inner wall of the.

In addition, a sufficient amount of refrigerating machine oil is supplied to the compressor 1
Since it can be returned to 0, it is possible to prevent a problem such as seizure of the compressor 10 from occurring and prevent the heat transfer coefficient from being lowered by the refrigerating machine oil adhering to the inner wall.

Further, in this embodiment, since the oil repellent film is provided on the inner wall of the tube 31, the refrigerating machine oil is used as the tube 3
It can be surely prevented from adhering to the inner wall of 1.

(Second Embodiment) In this embodiment, as shown in FIG. 5, the number of tubes 31 communicating with the inlet header tank 34 is the same as the number of tubes 31 communicating with the outlet header tank 35. In this state, by making the passage sectional area of the tube 31 on the refrigerant inlet 32 side smaller than the passage sectional area on the refrigerant outlet 33 side, the total refrigerant passage sectional area of the refrigerant passage 31a on the refrigerant inlet 32 side becomes It is configured to be smaller than the total refrigerant passage cross-sectional area on the outlet 33 side.

As a result, like the first embodiment, a sufficient amount of refrigerating machine oil can be returned to the compressor 10 while the capacity of the evaporator 30 is fully exerted.

(Other Embodiments) In the above-described embodiment, the vapor compression refrigerator using the ejector according to the present invention is applied to a vehicle air conditioner, but the application of the present invention is not limited to this. .

Further, in the above embodiment, the tube 31
However, the present invention is not limited to this, and may be made of, for example, an aluminum alloy.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an ejector cycle according to an embodiment of the present invention.

FIG. 2A is a perspective view of an evaporator applied to the ejector cycle according to the first embodiment of the present invention, and FIG.
FIG. 3 is a schematic diagram showing a refrigerant flow of an evaporator applied to the ejector cycle according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram of an eject according to an embodiment of the present invention.

FIG. 4 is a p-h diagram.

FIG. 5 is a schematic diagram showing a refrigerant flow of an evaporator applied to an ejector cycle according to a second embodiment of the present invention.

[Explanation of symbols]

30 ... Evaporator, 31 ... Tube, 32 ... Refrigerant inlet, 33
... Refrigerant outlet, 34 ... Inlet side header tank, 35 ... Outlet side header tank, 36 ... Header tank, 37 ... Fins.

Claims (3)

[Claims] 1. An evaporator applied to a vapor compression refrigerator having an ejector (40) for converting expansion energy into pressure energy while decompressing and expanding the refrigerant to increase suction pressure of the compressor, the refrigerant comprising: Of the refrigerant passages (31a) from the inlet (32) to the refrigerant outlet (33), the total refrigerant passage sectional area on the refrigerant inlet (32) side is smaller than the total refrigerant passage sectional area on the refrigerant outlet (33) side. An evaporator characterized by the following. 2. The passage cross-sectional area of the tube (31) on the refrigerant inlet (32) side among the tubes (31) constituting the refrigerant passage (31a) has a passage cutoff on the refrigerant outlet (33) side. The evaporator according to claim 1, which is smaller than an area. 3. The number of the tubes (31) on the refrigerant inlet (32) side among the plurality of tubes (31) forming the refrigerant passage (31a) is the number on the refrigerant outlet (33) side. Evaporator according to claim 1, characterized in that it has less than the number of tubes (31).