Cross Reference to Related Applications This application is an application filed under 35 U. S. C. § 111 (a) claiming the benefit pursuant to 35 U. S. C. § 119 (e) (1) of the filing date of Provisional Application No. 60/478,303 filed on June 16,2003 pursuant to 35 U. S. C. § 111 (b).

Technical Field The present invention relates to a refrigeration system for use in a refrigeration cycle or the like using C02 as a refrigerant. It also relates to an evaporator to be preferably used in the refrigeration system, a method of evaporating a refrigerant, and a vehicle equipped with the refrigeration system.

Background Art In a conventional vapor compression type refrigeration cycle, Freon series refrigerants are commonly used. In recent years, however, from the viewpoint of global environment protection, a refrigeration cycle using a natural refrigerant such as carbon dioxide (CO2) has began to attract a great deal of attention.

As evaporators for use in a refrigeration cycle using C02, for example, evaporators disclosed by the following patent documents Nos. 1 and 2 are well- known.

In such an evaporator, introduced into the evaporator is a low-temperature and low-pressure liquid-phase C02 refrigerant passed through a compressor, a cooler (evaporator) such as a gas cooler and a decompressing device such as an expansion valve. The refrigerant introduced into the evaporator exchanges the heat with the ambient air to thereby be heated while passing through the evaporator, causing a gradual increase in vapor quality. Then, it flows out of the evaporator as a gaseous refrigerant.

On the other hand, the following non-patent document No. 1 discloses a relationship between vapor quality and evaporation coefficient of heat transfer during evaporation process of C02 refrigeration. This document reports as follows. In the state in which the CO2 vapor quality is lower than a predetermined value, more specifically, in the state in which the vapor quality is lower than the range of 0.4 to 0.6, the coefficient of evaporation heat transfer can be kept large enough, resulting in high heat exchanging efficiency. To the contrary, in the case in which vapor quality of refrigerant is higher than a predetermined value (a range of 0.4 to 0.6), the coefficient of evaporation heat transfer becomes extremely low, resulting in extremely decreased heat exchanging efficiency.

[Patent Document No. 1] Japanese Unexamined Laid-open Patent Publication No. 2000-81294 [Patent Document No. 2] Japanese Unexamined Laid-open Patent Publication No. 2000-304472 [Non-patent Document No. 1]

J. PETTERSEN, R. RIEBERER, S. T. MUNKEJORD"HEAT TRANSFER AND PRESSURE DROP CHARACTERISTIC OF EVAPORATING CARBON DIOXIDE IN MICROCANNEL TUBES"4"IIR Gustiv Lorentzen Conference on Natural Working Fluids pp. 107-114 (2000) Under the above-mentioned technical background, the present inventors analyzed in detail a change of vapor quality of CO2 refrigerant in conventional evaporators shown in the aforementioned patent documents Nos. 1 and 2, and revealed the fact that in conventional evaporators, sufficient heat exchanging efficiency cannot be obtained in the entire region of the evaporator, causing a deterioration of the heat exchanging performance.

As shown in Fig. 10, in a conventional evaporator 200, the refrigerant immediately after being introduced via the refrigerant inlet 201 is large in ratio of liquid phase refrigerant, and therefore low in vapor quality. However, as the refrigerant advances in the evaporator 200, at the rear half portion of the evaporator passage, the ratio of the gaseous phase refrigerant becomes higher due to the heat exchanging with the ambient air, raising the vapor quality up to the predetermined value (the range of 0.4 to 0.6). Thereafter, the refrigerant is introduced to the refrigerant outlet 202 while increasing the vapor quality. As mentioned above, in the first half of the evaporator passage, the vapor quality of refrigerant is lower than the predetermined value, and therefore large enough coefficient of heat transfer can be secured, which in turn causes efficient heat exchange. However, in the latter half thereof, the vapor quality of refrigerant becomes higher than the predetermined value, and therefore the heat exchanging rate extremely drops, which may cause a deterioration of the heat exchange performance.

The present invention has been made in view of the aforementioned

drawbacks, and aims to provide an evaporator, a refrigeration system, a vehicle equipped with the system, and a method of evaporating a refrigerant capable of preventing the vapor quality of refrigerant in an evaporator passage from being increased and capable of enhancing the heat exchanging performance.

Disclosure of Invention To attain the aforementioned objects, the first invention has the following structure.

[1] An evaporator for use in a refrigeration system, the evaporator includes: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, since the refrigerant high in vapor quality among the refrigerant which is being raised in vapor quality during the evaporation procedure flows out at the intermediate position of the evaporator passage, excessive raising in vapor quality of the refrigerant can be prevented during the evaporation procedure, enabling the heat exchanging of the refrigerant almost at the entire region of the evaporator passage in a state in which the vapor quality of the refrigerant is low. This

prevents a deterioration of the coefficient of heat transfer, resulting in enhanced heat exchanging efficiency and heat exchanging performance.

The second invention has the following structure.

[2] An evaporator for use in a refrigeration system, the evaporator comprises: a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The third invention has the following structure.

[3] An evaporator for use in a refrigeration system, the evaporator comprising : a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of evaporation passages in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage corresponding to a connecting portion between adjacent evaporation passages for discharging a refrigerant high in vapor quality passing through the intermediate portion.

In this invention, in the similar manner as in the above case, effective heat exchanging can be attained almost at the entire region of the evaporator passage in a state in which the vapor quality of refrigerant is low.

In the aforementioned first to third inventions, for the purpose of assuredly restraining the raising of vapor quality of refrigerant during the evaporation process, it is preferable to employ the following structures [4] and [5].

[4] The evaporator as recited in any one of the aforementioned Items 1 to 3, wherein it is configured such that the refrigerant whose vapor quality is 0.5 or higher

flows out of the intermediate outlet.

[5] The evaporator as recited in any one of aforementioned Items 1 to 3, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the vapor quality of the main refrigerant at the intermediate portion of the evaporator passage is adjusted to 0.3 to 0.7 by the flowing of the diversion refrigerant.

[6] The evaporator as recited in any one of aforementioned Items 1 to 3, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

In the invention, in cases where the structure as recited in the aforementioned Item 6 is employed, the refrigerant can be circulated smoothly.

In the aforementioned first to third inventions, as recited in the following structures [7] and [8], it can be preferably used in an evaporator using supercritical refrigerant such as a carbon dioxide (CO2).

[7] The evaporator as recited in any one of aforementioned Items 1 to 3,

wherein a supercritical refrigerant is used as the refrigerant.

[8] The evaporator as recited in any one of aforementioned Items 1 to 3, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The fourth invention has the following structure.

[9] An evaporator for use in a refrigeration system, the evaporator comprising: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gaseous refrigerant among the refrigerant passing through the intermediate portion.

In this invention, since the gas phase component of the refrigerant high in vapor quality among the refrigerant which is being raised in vapor quality during the evaporation procedure flows out of the intermediate position of the evaporator passage, excessive raising in vapor quality of the refrigerant can be prevented during the evaporation procedure, enabling the heat exchanging of the refrigerant almost at the entire region of the evaporator passage in a state in which the vapor quality of the refrigerant is low. This prevents a deterioration of the coefficient of heat transfer, resulting in enhanced heat exchanging efficiency and heat exchanging performance.

The fifth invention has the following structure.

[10] An evaporator for use in a refrigeration system, the evaporator comprising: a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gaseous refrigerant among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The sixth invention has the following structure.

[11] An evaporator for use in a refrigeration system, the evaporator

comprising: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of evaporation passages in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage corresponding to a connection portion between adjacent evaporation passages for discharging a gaseous refrigerant among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

[12] The evaporator as recited in any one of claims 9 to 11, further comprising a gas-liquid separator provided at the intermediate portion of the evaporator passage, wherein it is configured such that a gas phase refrigerant separated by the gas-liquid separator flows out of the refrigerant outlet and a liquid phase refrigerant is led to the refrigerant outlet via the evaporator passage.

In the invention, in cases where the structure as recited in the aforementioned Item 12 is employed, the gas phase refrigerant can be extracted assuredly at the

intermediate portion of the evaporator passage, further improving the heat exchanging efficient.

[13] The evaporator as recited in any one of the aforementioned Items 9 to 11, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

In the invention, in cases where the aforementioned structure as recited in Item 13, the refrigerant can be circulated smoothly.

In the aforementioned first to third inventions, as recited in the following structures [14] and [15], it can be preferably used in an evaporator using supercritical refrigerant such as a carbon dioxide (CO2).

[14] The evaporator as recited in any one of the aforementioned Items 9 to 11, wherein a supercritical refrigerant is used as the refrigerant.

[15] The evaporator as recited in any one of the aforementioned Items 9 to 11, wherein a carbon dioxide (C02) refrigerant is used as the refrigerant.

The preferable structure of the aforementioned fourth to sixth inventions as recited in the aforementioned Items [11] to [15] also can be applied to the

aforementioned first to third inventions.

Furthermore, the preferable structure of the aforementioned first to third inventions as recited in the aforementioned Items [4] to [8] also can be applied to the aforementioned fourth to sixth inventions.

The aforementioned first to third inventions can be preferably applied to a refrigeration system as shown below.

That is, the seventh invention has the following structure.

[16] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The eight invention has the following structure.

[17] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporation passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The ninth invention has the following structure.

[18] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of evaporation passages in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage corresponding to a connecting portion between adjacent evaporation passages for discharging a refrigerant high in vapor quality passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat

exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

In the seventh to ninth inventions, in the same manner as in the aforementioned first to third inventions, it is preferable to employ the following structure.

[19] The refrigeration system as recited in any one of aforementioned Items 16 to 18, wherein it is configured such that the refrigerant whose vapor quality is 0.5 or higher flows out of the intermediate outlet.

[20] The refrigeration system as recited in any one of aforementioned Items 16 to 18, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the vapor quality of the main refrigerant at the intermediate portion of the evaporator passage is adjusted to 0.3 to 0.7 by the flowing of the diversion refrigerant.

[21] The refrigeration system as recited in any one of aforementioned Items 16 to 18, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

[22] The refrigeration system as recited in any one of aforementioned Items 16 to 18, wherein a supercritical refrigerant is used as the refrigerant.

[23] The refrigeration system as recited in any one of aforementioned Items 16 to 18, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The aforementioned fourth to sixth inventions can be preferably applied to a refrigeration system as shown below.

That is, the tenth invention has the following structure.

[24] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The eleventh invention has the following structure.

[25] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The twelfth invention has the following structure.

[26] A refrigeration system in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of evaporation passages in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage corresponding to a connection portion between adjacent evaporation passages for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

In the tenth to twelfth inventions, in the same manner as in the aforementioned fourth to sixth inventions, it is preferable to employ the following structure.

[27] The refrigeration system as recited in any one of the aforementioned Items 24 to 26, further comprising a gas-liquid separator provided at the intermediate portion of the evaporator passage, wherein it is configured such that a liquid phase refrigerant separated by the gas-liquid separator flows out of the refrigerant outlet and a liquid refrigerant is led to the refrigerant outlet via the evaporator passage.

[28] The refrigeration system as recited in any one of the aforementioned Items 24 to 26, wherein it is configured such that when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

[29] The refrigeration system as recited in any one of the aforementioned Items 24 to 28, wherein a supercritical refrigerant is used as the refrigerant.

[30] The refrigeration system as recited in any one of the aforementioned

Items 24 to 26, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The aforementioned first to third inventions can be preferably applied to a method for evaporating a refrigeration as shown below.

That is, the thirteenth invention has the following structure.

[31] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low at almost the entire region of the evaporator passage.

The fourteenth invention has the following structure.

[32] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises:

a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The fifteenth invention has the following structure.

[33] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; and

an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of evaporation passages in turn, wherein at an intermediate portion of the evaporator passage corresponding to a connecting portion between adjacent evaporation passages, a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion flows out.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

In the thirteenth to fifteenth inventions, in the same manner as in the aforementioned first to third inventions, it is preferable to employ the following structure.

[34] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 31 to 33, wherein the refrigerant whose vapor quality is 0.5 or higher flows out of the intermediate outlet of the evaporator passage.

[35] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 31 to 33, wherein when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the vapor quality of the main

refrigerant at the intermediate portion of the evaporator passage is adjusted to 0.3 to 0.7 by the flowing of the diversion refrigerant.

[36] The method for evaporating a refrigerant evaporator as recited in any one of the aforementioned Items 31 to 33, wherein when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

[37] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 31 to 33, wherein a supercritical refrigerant is used as the refrigerant.

[38] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 31 to 33, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The aforementioned fourth to sixth inventions can be preferably applied to a method for evaporating a refrigeration as shown below.

That is, the sixteenth invention has the following structure.

[39] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises:

a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; and an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet, wherein at an intermediate outlet provided at an intermediate portion of the evaporator passage, a gas phase refrigerant among the refrigerant passing through the intermediate portion flows out.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The seventeenth invention has the following structure.

[40] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises: a pair of header tanks disposed in parallel with each other and provided with a refrigerant inlet and a refrigerant outlet ; a plurality of heat exchanging tubes each having both ends connected to the header tanks in fluid communication and arranged in parallel with each other in a longitudinal direction of the header tank; a plurality of paths formed by grouping the plurality of heat exchanging tubes; an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet by passing the refrigerant through the plurality of paths in turn, and

wherein at an intermediate outlet provided at an intermediate portion of the evaporator passage, a gas phase refrigerant among the refrigerant passing through the intermediate portion flows out.

In this invention, in the same manner as in the above case, effective heat exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

The eighteenth invention has the following structure.

[41] A method for evaporating a refrigerant using an evaporator, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; a plurality of evaporation passages for causing the refrigerant to evaporate by passing the refrigerant therein; and an evaporator passage for leading the refrigerant introduced via the refrigerant inlet to the refrigerant outlet via by passing the refrigerant through the plurality of evaporation passages in turn, and wherein at an intermediate outlet provided at an intermediate portion of the evaporator passages corresponding to a connection portion between adjacent evaporation passages, a gas phase refrigerant among the refrigerant passing through the intermediate portion flows out.

In this invention, in the same manner as in the above case, effective heat

exchanging can be attained in a state in which the vapor quality of refrigerant is low almost at the entire region of the evaporator passage.

In the sixteenth to eighteenth inventions, in the same manner as in the aforementioned fourth to sixth inventions, it is preferable to employ the following structure.

[42] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 39 to 41, wherein the evaporator further comprises a gas-liquid separator provided at the intermediate portion of the evaporator passage, wherein a gas phase refrigerant separated by the gas-liquid separator flows out of the refrigerant outlet and a liquid refrigerant is led to the refrigerant outlet via the evaporator passage.

[43] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 39 to 41, wherein when the refrigerant flowing out of the intermediate outlet of the evaporator passage is defined as a diversion refrigerant and the refrigerant to be led from the intermediate portion of the evaporator passage to the refrigerant outlet is defined as a main refrigerant, the diversion refrigerant is merged with the main refrigerant at a vicinity of the refrigerant outlet.

[44] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 39 to 41, wherein a supercritical refrigerant is used as the refrigerant.

[45] The method for evaporating a refrigerant as recited in any one of the aforementioned Items 39 to 41, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The invention can be preferably applied to an evaporator for use in vehicles as will be explained below.

That is, the nineteenth invention has the following structure.

[46] An evaporator for use in a vehicle refrigeration, the evaporator comprising: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

The twentieth invention has the following structure.

[47] An evaporator for use in a vehicle refrigeration system, the evaporator comprising: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant;

an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

The aforementioned nineteenth or twentieth invention can be preferably applied to the following structure.

[48] The evaporator for use in a vehicle refrigeration system as recited in the aforementioned Item 46 or 47, wherein a supercritical refrigerant is used as the refrigerant.

[49] The evaporator for use in a vehicle refrigeration system as recited in the aforementioned Item 46 or 47, wherein a carbon dioxide (CO2) refrigerant is used as the refrigerant.

The twenty-first invention has the following structure.

[50] A refrigeration system for use in vehicles in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises:

a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant passing through the intermediate portion.

The twenty-second invention has the following structure.

[51] A refrigeration system for use in vehicles in which a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

In the aforementioned refrigeration system for use in vehicles, the following

structure can be preferably applied.

[52] The refrigeration system for use in vehicles as recited in the aforementioned Item 50 or 51, wherein a supercritical refrigerant is used as the refrigerant.

[53] The refrigeration system for use in vehicles as recited in the aforementioned Item 50 or 51, wherein a carbon dioxide (C02) refrigerant is used as the refrigerant.

The twenty-third invention has the following structure.

[54] A vehicle equipped with a refrigeration system, wherein in the refrigeration system, a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, and wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a refrigerant high in vapor quality among the refrigerant

passing through the intermediate portion.

The twentieth-fourth invention has the following structure.

[55] A vehicle equipped with a refrigeration system, wherein in the refrigeration system, a high-temperature and high-pressure refrigerant compressed by a compressor is cooled by a cooler, a low-temperature and high-pressure refrigerant cooled by the cooler is decompressed by a decompressor, and then the refrigerant decompressed by the decompressor is evaporated by an evaporator and returned to the compressor, and wherein the evaporator comprises: a refrigerant inlet for introducing a refrigerant; a refrigerant outlet for discharging the refrigerant; an evaporator passage for causing the refrigerant introduced via the refrigerant inlet to evaporate and leading the refrigerant to the refrigerant outlet ; and an intermediate outlet provided at an intermediate portion of the evaporator passage for discharging a gas phase refrigerant among the refrigerant passing through the intermediate portion.

In the aforementioned vehicle according to the invention, the following structure can be preferably applied.

[56] The vehicle equipped with a refrigeration system as recited in the aforementioned Item 54 or 55, wherein a supercritical refrigerant is used as the refrigerant.

[57] The vehicle equipped with a refrigeration system as recited in the aforementioned Item 54 or 55, wherein a carbon dioxide (C02) refrigerant is used as the refrigerant.

Brief Description of Drawings Fig. 1 is a perspective view showing an evaporation apparatus of a refrigeration system for use in vehicles to which an evaporator according to an embodiment of this invention is applied; Fig. 2 is an exploded perspective view showing the lower header tank portion of the evaporator according to the embodiment; Fig. 3 is a perspective view showing the lower header tank portion of the evaporator according to the embodiment; Fig. 4 is a cross-sectional view showing the evaporator according to the embodiment; Fig. 5 is an exploded perspective view showing the upper header tank portion of the evaporator according to the embodiment; Fig. 6 is a perspective view showing the partitioning plates of the evaporator according to the embodiment; Fig. 7 is a perspective view showing a gas-liquid separator applied to the evaporation apparatus according to the embodiment; Fig. 8 is a refrigeration passage circuit showing the flow of refrigerant in the evaporation apparatus according to the embodiment; Fig. 9A is a block diagram showing the relationship between the liquid phase refrigerant and the gas phase refrigerant in the evaporator according to the

embodiment; Fig. 9B is a graph showing the relationship between the vapor quality of refrigerant and the evaporation coefficient of heat transfer in the evaporator according to the embodiment; Fig. 10A is a block diagram showing the relationship between the liquid phase refrigerant and the gas phase refrigerant in a conventional evaporator; and Fig. 10B is a graph showing the relationship between the vapor quality of refrigerant and the evaporation coefficient of heat transfer in the evaporator according to the embodiment.

Best Mode for Carrying Out the Invention Figs. 1 to 5 show an evaporation apparatus to be applied to a refrigeration system for use in vehicles which is an embodiment of the present invention. As shown in these figures, this evaporation apparatus is an apparatus to be applied to an vapor compressing type refrigeration cycle using C02 as a refrigerant, and includes an evaporator 100 and a gas-liquid separator 70 provided at a part of a refrigerant passage of the evaporator 100.

The evaporator 100 is provided with, as fundamental structural components, a pair of upper and lower flat header tanks 10 and 30, flat heat exchanging tubes 1 a and 1b disposed between the pair of header tanks 10 and 30 with both ends thereof connected to the pair of header tanks 10 and 30 in fluid communication, arranged in parallel with each other in the longitudinal direction (right and left direction) of the header tank, and arranged in two rows in the widthwise direction (fore and aft direction) of the header tank, and corrugated fins each disposed between adjacent

tubes 1 a and 1 b.

As shown in Figs. 2 to 4, the lower header tank 10 is provided with a header tank main body 11 and a cover plate 20.

The header tank main body 11 is provided with a total of six refrigerant passages 12a and 12b extending in the longitudinal direction of the header tank main body 11 therein and disposed in parallel in the fore and aft direction.

Formed on the flat upper surface of the header tank main body 11 are a plurality of tube connecting apertures 14a and 14b each having an elongated configuration corresponding to the end face configuration of the heat exchanging tube 1a and 1 b and arranged at predetermined intervals in the longitudinal direction of the header tank 10.

Also formed on the upper surface of the header tank main body 11 are round communication apertures 15a disposed between adjacent refrigerant passages 12a among the front three refrigerant passages 12a and between adjacent front side tube connecting apertures 14a, and round communication apertures 15b disposed between adjacent refrigerant passages 12b among the rear three refrigerant passages 12b and between adjacent rear side tube connecting apertures 14b. Each communication aperture 15a (15b) and each tube connecting aperture 14a (14b) are communicated with corresponding refrigerant passages 12a (12b). The front side communication apertures 15a and the front side tube connecting aperture 14a cause the front side three refrigerant passages 12a to be communicated with each other, and the rear side communication apertures 15b and the rear side tube connecting aperture 14b cause the rear side three refrigerant passages 12b to be communicated with each other.

On the lower side of each end of the header tank main body 11 is formed cut

portion 16 continuing from the front face of the main body 11 and to the rear face thereof and crossing the six refrigerant passages 12a and 12b.

Further formed on the lower surface side of the intermediate portion of the header tank main body 11 is a cut portion 16a continuing from the front face of the main body 11 to the intermediate portion thereof and crossing the front side three refrigerant passages 12a.

The cover plate 20 has a size corresponding to the upper surface of the header tank main body 11. Formed in this cover plate 20 are a plurality of elongated tube insertion apertures 24a and 24b corresponding to the tube connecting apertures 14a and 14b and disposed in two rows at certain intervals in the longitudinal direction of the cover plate.

This cover plate 20 is fixed on the upper surface of the header tank main body 11 with the tube insertion apertures 24a and 24b aligned with the tube connecting apertures 14a and 14b in a laminated manner, thereby closing the communication apertures 15a and 15b.

As shown in Figs. 4 and 5, the upper side header tank 30 is provided with a header tank main body 31 and a cover plate 40.

In the header tank main body 31, in the same manner as mentioned above, a total of six refrigerant passages 32a and 32b, tube connecting apertures 34a and 34b and communication apertures 15a and 15b are formed.

Furthermore, as shown in Fig. 1, in the upper surface side of both end portions of the upper side header tank main body 31, cut portions 36b are formed.

Further formed in the lower surface side of the intermediate portion of the header tank 31 is a cut portion 36b continuing from the rear face of the header tank to the widthwise middle portion and crossing the rear side three refrigerant passages 32b.

A cover plate 40 disposed on the lower surface of the upper side header tank main body 31 is provided with tube insertion aperture 44a and 44b in the same manner as mentioned above.

This cover plate 40 is fixed to the lower surface of the header tank main body 31 with the tube insertion apertures 44a and 44b aligned with the tube connecting apertures 34a and 34b in a laminated manner, thereby closing the communication apertures 15a and 15b.

In the upper side header tank 30, since other structures are essentially the same as those of the aforementioned lower header tank 10, overlapping explanation will be omitted by allotting corresponding reference numerals to the same or corresponding portions.

On the other hand, the heat exchanging tube 1a (1b) is constituted by an article formed by an extrusion method or a drawing method, and has a flat cross- sectional shape. Formed in the heat exchanging tube 1 a (1 b) are a plurality of tube apertures 2 extending in the longitudinal direction of the tube and arranged in the widthwise direction thereof. In this embodiment, the tube aperture 2 constitutes a heat exchanging passage.

The upper and lower end portions of the plurality of heat exchanging tubes 1 a and 1 b are inserted in the tube insertion apertures 24a and 24b of the cover plate 20 and 40 of the aforementioned header tank 10 and 30 and then inserted in and connected to the tube connecting apertures 14a, 14b, 34a and 34b of the header tank main body 11 and 31.

Thus, between the upper and lower header tanks 10 and 30, a plurality of heat exchanging tubes 1a and 1b are disposed in parallel with each other along the widthwise direction of the evaporator in two rows.

Between the adjacent heat exchanging tubes 1 a and 1 b, a corrugated fin 5 is disposed.

Thus, the front side refrigerant passages 12a and 32a of the header tanks 10 and 30 are communicated with each other via the front row side heat exchanging tubes 1a, while the rear side refrigerant passages 12b and 32b are communicated with each other via the rear row side heat exchanging tubes 1 b.

As shown in Figs. 1 and 6, in the cut portions 16,16a, 36 and 36a of each header tank 10 and 30, partition plates 51 to 56 are fitted so as to partition each refrigerant passage 12a, 12b, 32a and 32b.

The partition plate 51 positioned at one end portion (right side end portion) of the upper header tank 30 has a refrigerant inlet 51 b at a position corresponding to the rear side refrigerant passages 32b. The remaining area is closed.

The partition plate 52 (53) positioned at the intermediate portion of the header tank 10 (30) is entirely closed.

The partition plate 53 positioned at the other end portion (left side end portion) of the upper header tank 30 has an upper side external communication portion 53b at a position corresponding to the rear side refrigerant passages 32b. The remaining area is closed.

The partition plate 54 positioned at the other end portion of the lower header tank 10 has a lower side external communication portion 54a at a position corresponding to the front side refrigerant passages 12a. The remaining area is closed.

The partition plate 56 positioned at one end portion of the lower header tank 10 has a refrigerant outlet 56a at a position corresponding to the front side refrigerant passages 12a. The remaining area is closed.

As shown in Figs. 1 and 7, an end portion of the refrigerant inlet tube 61 b inserted into the one end rear portion of the upper header tank 30 is connected to the refrigerant inlet 51 b. Thus, the inlet tube 61 b is connected to the rear side refrigerant passages 32b of the upper side header tank 30.

The refrigerant outlet tube 61 a disposed along the front side of one end face of the evaporator 100 in the up-and-down direction has a lower end portion bent toward the lower side header tank 10. The lower end portion is inserted from the front side of one end face of the lower header tank 10 to be connected to the refrigerant outlet 56a. Thus, the refrigerant outlet tube 61 a is connected to the front side refrigerant passage 12a of the lower side header tank 10 in fluid communication.

On the other hand, the gas-liquid separator 70 is disposed along the other end face of the evaporator 100 in the up-and-down direction. Connected to the refrigerant inlet 71 of this gas-liquid separator 70 is an end of a first connecting tube 81. The other end of the connecting tube 81 is inserted from the rear portion of the other end face of the upper header tank 30 and connected to the upper side external communication portion 53b in fluid communication. Thus, the refrigerant inlet 71 of the gas-liquid separator 70 is connected to the rear side refrigerant passage 32b in a fluid communication via the first connecting tube 81.

Connected to the liquid phase outlet 72 of the gas-liquid separator 70 is an end of a second connecting tube 82. The other end of the connecting tube 82 is inserted from the front portion of the other end face of the lower header tank 10 and connected to the lower side external communication portion 54a. Thus, the liquid phase outlet 72 of the gas-liquid separator 70 is connected to the front side refrigerant passage 12a of the lower header tank 30 in fluid communication.

On the other hand, connected to the gas phase outlet 73 of the gas-liquid

separator 70 is one end of a bypass pipe 83. The other end of the bypass pipe 83 is connected to the aforementioned refrigerant outlet pipe 61 a. Thus, the gas phase outlet 73 of the gas-liquid separator 70 is connected to the refrigerant outlet pipe 61 a in fluid communication via the bypass pipe 83.

In this embodiment, the gas phase outlet 73 of the gas-liquid separator 70 constitutes an intermediate outlet.

The evaporation apparatus of this embodiment having the aforementioned structure forms a refrigeration system using CO2 together with a compressor, a cooler (condenser) such as a gas cooler and a decompressor such as an expansion valve.

In this refrigeration system, the high-temperature and high-pressure gas phase refrigerant compressed by a compressor is cooled by a condenser.

Thereafter, the low-temperature and high-pressure refrigerant (liquid refrigerant) is expanded and decompressed by the expansion valve to be a low-temperature and low-pressure refrigerant. This low-temperature and low-pressure liquid phase refrigerant is introduced into the one end side half portion (right side half portion) of the rear side refrigerant passage 32b in the upper header tank 30 of the evaporator 100.

The introduced refrigerant flows downward through a plurality of heat exchanging tubes 1 b (first path P1) disposed at the one end side half portion (right side half portion) among the rear row heat exchanging tubes 1 b to be introduced into the one end side half portion (right side half portion) of the rear row side refrigerant passage 12b of the lower header tank 10.

The refrigerant introduced into the one end side half portion of the lower rear side refrigerant passage 12b is introduced into the other end side half portion (left side half portion) via the rear side refrigerant passage 12b. The refrigerant introduced

into the other end side half portion of the lower rear side refrigerant passage 12b flows upward through a plurality of heat exchanging tubes (second path P2) disposed at the other end side half portion (left side half portion) among the rear row heat exchanging tubes 1b to be introduced into the other end side half portion of the rear side refrigerant passage 32b in the upper header tank 30.

The refrigerant introduced into the other end side half portion of the upper rear side refrigerant passage 32b is introduced into the gas-liquid separator 70 via the upper side external communication portion 53b and the first connecting tube 81.

The refrigerant introduced into the gas-liquid separator 70 is separated into a gas phase refrigerant and a liquid phase refrigerant. Only the liquid phase refrigerant is introduced into the other end side half portion (right side half portion) of the front side refrigerant passage 12a in the lower header tank 10 via the liquid phase outlet 72 and the second connecting tube 82.

The refrigerant introduced into the other end side half portion (left side half portion) of the lower front side refrigerant passage 12a flows upward through a plurality of heat exchanging tubes (third path P3) disposed at the other end side half portion (left side half portion) among the front row heat exchanging tubes 1a to be introduced into the other end side half portion of the front side refrigerant passage 32a in the upper header tank 30.

The refrigerant introduced into the other end side half portion of the upper front side refrigerant passage 32a is introduced into one end side half portion via the refrigerant passage 32a.

Thus, the refrigerant introduced into one end side half portion of the upper front side refrigerant passage 32a flows downward through a plurality of heat exchanging tubes (fourth path P4) disposed at one end side half portion (right side

half portion) among the front row heat exchanging tubes 1 a to be introduced into one end side half portion of the front side refrigerant passage 32a in the lower header tank 10.

Thus, the liquid phase refrigerant exchanges heat with the ambient air to be heated and evaporated while passing through the first path (P1) to the fourth path (P4).

This evaporated gas phase refrigerant flows out of the refrigerant outlet 56a and the refrigerant outlet tube 61 a.

On the other hand, the gas phase refrigerant separated by the gas-liquid separator 70 is introduced into the bypass pipe 83 via the gas phase outlet 73. Then, the gas phase refrigerant is introduced into the refrigerant outlet pipe 61 a via the bypass pipe 83.

Thus, the dispersion refrigerant bypassed the third and fourth paths P3 and P4 is merged with the main refrigerant passed the third and fourth paths P3 and P4 in the refrigerant outlet pipe 61 a. Thereafter, the merged refrigerant will be returned to the compressor.

In this embodiment, the entire refrigerant passage from the refrigerant inlet 51 b of the evaporation apparatus to the refrigerant outlet 56a forms an evaporator passage.

As mentioned above, in the evaporation apparatus of the present embodiment, while the vapor quality of the refrigerant is raised gradually by the heat exchanging while passing through the first and second paths P1 and P2, the refrigerant <BR> <BR> component high in vapor quality, i. e. , a gas phase refrigerant, among the refrigerant raised in vapor quality is made to be flown out. This flowage of this gas phase component (component high in vapor quality) causes deterioration of the vapor quality

as the entire refrigerant. Thus, since the refrigerant low in vapor quality can be passed through the third and fourth paths P3 and P4, heat exchanging can be performed by the low vapor quality refrigerant through out the entire paths P1 to P4.

In other words, as shown in Fig. 9, according to the evaporation apparatus of this embodiment, the gas phase refrigerant high in vapor quality is discharged at a part of the evaporator passage. Thus, as shown in Fig. 9A, it becomes possible to prevent deterioration of the rate of the liquid refrigerant with respect to the gas phase refrigerant. As a result, as shown in Fig. 9B, in the evaporator passage, heat exchanging can be performed almost at the entire region of the evaporator passage at lower vapor quality in a state in which the refrigerant vapor quality does not largely exceed a predetermined value, resulting in an enhanced heat exchanging efficiency and heat exchanging performance.

In this embodiment, it is preferable to discharge (flow out) the gas phase refrigerant at the time when the vapor quality of the refrigerant passing through the first and second paths P1 and P2 reaches the range of 0.3 to 0.7, more preferably 0.4 to 0.6.

In other words, in cases where the discharge timing of the gas phase refrigerant is too late, there is the possibility that the vapor quality of the refrigerant before discharging the gap phase refrigerant becomes higher than a predetermined value, deteriorating the heat exchanging efficiency. To the contrary, in cases where the discharge timing of the gas phase refrigerant is too early, it is not preferable because there is the possibility that the vapor quality of the refrigerant becomes higher than a predetermined value after discharging the gap phase refrigerant, deteriorating the heat exchanging efficiency.

Furthermore, in order to adjust the refrigerant vapor quality in the third and

fourth paths P3 and P4 so as to fall within the aforementioned preferable range, it is preferable to flow out a refrigerant whose vapor quality is 0.5 or higher, more preferably 0.6 or higher.

By the way, in the embodiment, it is preferable to provide a gas-liquid separator before the evaporator 100 so that only the liquid phase refrigerant is introduced into the evaporator 100 and the gas phase refrigerant is merged with the refrigerant passed in the evaporator passage at the vicinity of the evaporator outlet.

That is, in this structure, since only the liquid phase refrigerant low in vapor quality can be introduced into the evaporator 100, the raising of refrigerant vapor quality in the evaporator passage can be prevented more assuredly, further enhancing the heat exchanging efficiency. Furthermore, since only the liquid phase refrigerant can be introduced into the header tank, the refrigerant can be sufficiently filled in the longitudinal direction of the header tank, enhancing the dispersiblity in the heat exchanging passages, which further enhances the heat exchanging performance.

In the aforementioned embodiment, the explanation is directed to the case in which only one intermediate outlet (gas phase outlet 73) for discharging the refrigerant high in vapor quality is provided. However, the present invention is not limited to the above, and two or more intermediate outlets can be provided.

Furthermore, in the aforementioned embodiment, the explanation is directed to the case in which the intermediate outlet is provided between the second path and the third path. However, the present invention is not limited to the above, and the intermediate outlet can be provided at any portion on the evaporator passage. For example, the intermediate outlet can be provided between the first and second paths, or the third and fourth paths. Needless to say, the number of paths is not limited to the aforementioned embodiment, and can be less than three or more than five.

In the aforementioned embodiment, the explanation is directed to the case in which the present invention is applied to the header type evaporator. However, the present invention is not limited to the above, and can be applied to another evaporators, such as a serpentine tube type evaporator, a laminate tube type evaporator, a drawn cup type evaporator, or an evaporator having plate fins.

As mentioned above, in this invention, since the refrigerant high in vapor quality among the refrigerant which is being raised in vapor quality during the evaporation procedure flows out at the intermediate position of the evaporator passage, excessive raising in vapor quality of the refrigerant can be prevented during the evaporation procedure, enabling the heat exchanging of the refrigerant almost at the entire region of the evaporator passage in a state in which the vapor quality of the refrigerant is low. This prevents deterioration of the coefficient of heat transfer, resulting in enhanced heat exchanging efficiency and heat exchanging performance.

The terms and expressions which have been employed herein are used as terms of description and not of limitation, and there is no intent, in the use of such terms and expressions, of excluding any of the equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed Industrial Applicability The present invention can be utilized in a refrigeration system for use in a refrigeration cycle or the like using C02 as a refrigerant. It also can be utilized in an evaporator to be employed in the refrigeration system, a method of evaporating a refrigerant and a vehicle equipped with the refrigeration system.