Abstract:
A stack type evaporator for use in an automotive air conditioner comprises generally a first mass which includes first heat exchanging elements, each first heat exchanging element having mutually independent first and second passages; and a second mass which includes second heat exchanging elements, each second heat exchanging element having a generally U-shaped third passage which has first and second ends. The second mass is arranged beside the first mass in such a manner that the first and second heat exchanging elements are aligned on a common axis. An inlet tank passage connects to upper ends of the first passages. An upstream tank passage connects to lower ends of the first passages and the first ends of the third passages. A downstream tank passage connects to lower ends of the second passages and the second ends of the third passages. An outlet tank passage connects to upper ends of the second passages. An inlet pipe connects to the inlet tank passage. An outlet pipe is connected to the outlet tank passage.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates in general to heat exchangers for use in automotive air conditioners, and more particularly to evaporators of a stack type. 
     2. Description of the Prior Art 
     In order to clarify the tasks of the present invention, two conventional stack type evaporators  1  and  1 ′ for automotive air conditioners will be described with reference to FIGS. 24 to  26  and FIGS. 27 to  30 . 
     One of them is shown in FIGS. 24 to  26 , which is described in for example Japanese Patent First Provisional Publication 62-798 and Japanese Patent 2,737,286. 
     As is seen from FIGS. 24 and 25, the first conventional evaporator  1  comprises a core unit  5 . Refrigerant inlet and outlet pipes  3  and  4  are fluidly connected to the core unit  5 , which are held by a coupler  2 . Under operation, a liquid-gaseous refrigerant is led into the core unit  5  through the inlet pipe  3  and evaporates to cool the core unit  5 . With this, air flowing through the core unit  5  is cooled. Gaseous refrigerant produced as a result of the evaporation is led into the outlet pipe  4  and into a compressor (not shown). The evaporator  1  is of a so-called “stack type” which comprises a plurality of elongate flat tubes or heat exchanging elements which are stacked, each including two mutually coupled elongate shell plates. Japanese Patent 2737286 shows an alternate arrangement of two areas for the refrigerant, one being a lower temperature area mainly occupied by a liquid refrigerant and the other being a higher temperature area mainly occupied by a gaseous refrigerant. With this alternate arrangement, the evaporator can exhibit a desired temperature distribution thereon. 
     As is seen from FIG. 25, in assembly of the air conditioner, the evaporator  1  and a heater core  9  are arranged perpendicular to a dash panel  8  by which an engine room  6  and a passenger room  7  are partitioned, and air for conditioning the passenger room is forced to flow in the direction of the arrow “a”, that is, in a direction parallel with the dash panel  8 . Although not shown in the drawing, a duct is provided in the passenger room  7  to assure such air flow. That is, the evaporator  1  and the heater core  9  are installed in the duct. The coupler  2  is exposed to the engine room  6  through an opening  10  formed in the dash panel  8 , so that the evaporator  1  is fluidly connected through pipes to a compressor (not shown) and a condenser (not shown) which are arranged in the engine room  6 . 
     Nowadays, for improving air flow in the passenger room  7 , there has been proposed an arrangement wherein, as is seen from FIG. 26, the evaporator  1  and the heater core  9  are arranged in parallel with the dash panel  8 , and the air for conditioning the room  7  is forced to flow in the direction of the arrow “b”. However, in this case, it becomes necessary to use much longer and complicated pipes as the inlet and outlet pipes  3  and  4  as is easily understood from the drawing. Of course, such arrangement brings about increase in cost of the air conditioner. Furthermore, due to usage of such complicated and longer pipes  3  and  4 , the flow resistance of the refrigerant becomes marked and thus the air conditioner fails to exhibit a satisfied performance. 
     The other conventional stack type evaporator  1 ′ is shown in FIGS. 27 to  30 , which is described in for example Japanese Patent First Provisional Publication 62-798 and Japanese Utility Model First Provisional Publication 7-12778. 
     As is seen from the drawings, the second conventional evaporator  1 ′ comprises a core unit  3 ′. The core unit  3 ′ comprises a plurality of elongate flat tubes  10 ′ (or heat exchanging elements) which are stacked, each including two mutually coupled elongate shell plates. Each elongate flat tube  10 ′ has two mutually independent flow passages  2 ′ and  2 ′ defined therein. A plurality of heat radiation fins  11 ′ are alternatively disposed in the stacked elongate flat tubes  10 ′. The two passages  2 ′ and  2 ′ defined in each flat tube  10 ′ have upper and lower tank spaces. By connecting or communicating adjacent flat tubes  10 ′ at the respective upper and lower tank spaces, there are formed a plurality of tank portions  4 ′,  5 ′ and  6 ′. As is seen from FIGS. 28 to  30 , at one end of the core unit  3 ′, there is provided a side tank portion  7 ′ by which the two tank portions  4 ′ and  4 ′ are connected. Under operation, a liquid-gaseous refrigerant is led through an inlet pipe  8 ′ and the inlet tank portion  5 ′ (see FIG. 28) into the core unit  3 ′. The refrigerant flows in the passages  2 ′ and  2 ′ of the core unit  3 ′ while evaporating to cool the core unit  3 ′. During this, the refrigerant flows also in the side tank portion  7 ′. Thus, air flowing through the core unit  3 ′ in the direction of the arrow “α” (see FIGS. 28 to  30 ) is cooled. Gaseous refrigerant produced as a result of the evaporation is led to an outlet pipe  9 ′ and to a compressor (not shown). 
     However, the above-mentioned other conventional stack type evaporator  1 ′ has the following drawbacks due to its inherent construction. 
     First, actually, the side tank portion  7 ′ does not contribute anything to the air cooling because the portion  7 ′ is positioned away from the air passing path. This brings about unsatisfied performance of the air conditioner. 
     Second, as is seen from FIG. 29, under operation of the evaporator  1 ′, due to the nature of the gravity, the liquid-gaseous refrigerant flowing in the upper tank portions  5 ′ and  4 ′ of the core unit  3 ′ is forced to feed a larger amount of refrigerant to upstream positioned flow passages  2 ′ and  2 ′ and a smaller amount of refrigerant to downstream positioned flow passages  2 ′ and  2 ′. The amount of the refrigerant in each area of the flow passages  2 ′ and  2 ′ is indicated by the down-pointed arrows in the drawing. While, due to inertia of the refrigerant, the refrigerant flowing in the lower tank portions  4 ′ and  4 ′ of the core unit  3 ′ is forced to feed a smaller amount of refrigerant to upstream positioned flow passages  2 ′ and  2 ′ and a larger amount of refrigerant to downstream positioned flow passages  2 ′ and  2 ′. The amount of the refrigerant in each area of the flow passages  2 ′ and  2 ′ is indicated by the up-pointed arrows in the drawing. That is, the refrigerant flow rate in the core unit  3 ′ is smaller in the inside portion than the outside portion. Thus, as is seen from FIG. 31, the core unit  3 ′ fails to have a uniformed temperature distribution therethroughout. That is, in the drawing, the outside portions of the core unit  3 ′ indicated by grids are forced to show a low temperature as compared with the inside portions thereof. This means that the air passing through the core unit  3 ′ fails to have a uniformed temperature distribution, which tends to make passengers in the passenger room uncomfortable. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a stack type evaporator which is free of the above-mentioned drawbacks. 
     According to a first aspect of the present invention, there is provided a stack type evaporator which comprises a first mass including first heat exchanging elements, each first heat exchanging element having mutually independent first and second passages; a second mass including second heat exchanging elements, each second heat exchanging element having a generally U-shaped third passage which has first and second ends, the second mass being arranged just beside the first mass in such a manner that the first and second heat exchanging elements are aligned on a common axis; an inlet tank passage connecting to upper ends of the first passages; an upstream tank passage connecting to lower ends of the first passages and the first ends of the third passages; a downstream tank passage connecting to lower ends of the second passages and the second ends of the third passages; an outlet tank passage connecting to upper ends of the second passages; an inlet pipe connected to the inlet tank passage; and an outlet pipe connected to the outlet tank passage. 
     According to a second aspect of the present invention, there is provided an arrangement in a motor vehicle having an engine room and a passenger room which are partitioned by a dash panel. The arrangement comprises an evaporator which includes a first mass including first heat exchanging elements, each first heat exchanging element having mutually independent first and second passages; a second mass including second heat exchanging elements, each second heat exchanging element having a generally U-shaped third passage which has first and second ends, the second mass being arranged just beside the first mass in such a manner that the first and second heat exchanging elements are aligned on a common axis; an inlet tank passage connecting to upper ends of the first passages; an upstream tank passage connecting to lower ends of the first passages and the first ends of the third passages; a downstream tank passage connecting to lower ends of the second passages and the second ends of the third passages; an outlet tank passage connecting to upper ends of the second passages; an inlet pipe connected to the inlet tank passage; and an outlet pipe connected to the outlet tank passage; means for placing the evaporator in such a manner that the evaporator is arranged in parallel with the dash panel and that the inlet tank passage and the upstream tank passage are positioned away from the dash panel as compared with the outlet tank passage and the downstream tank passage; and means for producing an air flow through the evaporator in a direction from the dash panel toward the evaporator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is front view of a stack type evaporator according to the present invention; 
     FIG. 2 is a side view of the evaporator of the invention; 
     FIG. 3 is a plan view of the evaporator of the invention; 
     FIG. 4A is a schematic sectional view of one heat exchanging element employed in the evaporator of the invention, which is taken from the direction “IV” of FIG. 1; 
     FIG. 4B is a view similar to FIG. 4A, but showing another exchanging element employed in the evaporator of the invention; 
     FIG. 5A is a sectional view of the heat exchanging element of FIG. 4A, which is taken from the direction “VA” of FIG. 5B; 
     FIG. 5B is a sectional view of the heat exchanging element of FIG. 4A, which is taken from the direction “VB” of FIG. 5A; 
     FIG. 6A is a sectional view of the heat exchanging element of FIG. 4B, which is taken from the direction “VIA” of FIG. 6B; 
     FIG. 6B is a sectional view of the heat exchanging element of FIG. 4B, which is taken from the direction “VIB” of FIG. 6A; 
     FIG. 7 is a schematically illustrated perspective view of the evaporator of the invention, showing the path of refrigerant; 
     FIGS. 8A and 8B are perspective view of two connector constructions employable in the invention; 
     FIGS. 9A,  9 B and  9 C are perspective views of upper portions of three recessed metal plates each being an essential part of a heat exchanging element, the upper portions having connector structures; 
     FIG. 10 is a schematically illustrated perspective view of the evaporator of the invention, showing the path of refrigerant in the evaporator; 
     FIG. 11 is a schematic plan view of a part of a motor vehicle where the evaporator of the invention associated with an air conditioner is operatively arranged; 
     FIG. 12 is a schematic perspective view of the evaporator of the invention, showing the flow condition of refrigerant in the evaporator; 
     FIG. 13 is a schematic view of the evaporator of the invention, showing a temperature distribution possessed by the evaporator; 
     FIG. 14 is a view similar to FIG. 10, but showing a first modification of the evaporator of the present invention; 
     FIG. 15 is a schematic plan view of a part of a motor vehicle where the first modification of the evaporator associated with an air conditioner is operatively arranged; 
     FIG. 16 is a schematic view of a second modification of the evaporator of the present invention, showing the path of refrigerant in the evaporator; 
     FIG. 17 is a schematic perspective view of the second modification of the evaporator of the invention; 
     FIG. 18 is an exploded perspective view of one heat exchanging element and its associated connector structure, which are employed in the second modification of the evaporator of FIG. 17; 
     FIG. 19 is a sectional view of an assembled unit including the heat exchanging element and the associated connector structure of FIG. 18; 
     FIG. 20 is a view similar to FIG. 14, but showing the flow condition of refrigerant in the second modification of the evaporator of the invention; 
     FIG. 21 is a view similar to FIG. 15, but showing a temperature distribution possessed by the second modification of the evaporator of the invention; 
     FIG. 22 is a view similar to FIG. 18, but showing a third modification of the evaporator of the invention; 
     FIG. 23 is a view similar to FIG. 16, but showing a fourth modification of the evaporator of the present invention; 
     FIG. 24 is a perspective view of a first conventional evaporator; 
     FIG. 25 is a plan view of a part of a motor vehicle where the first conventional evaporator associated with an air conditioner is operatively arranged; 
     FIG. 26 is a view similar to FIG. 25, but showing a drawback which is possessed by the first conventional evaporator when the same is arranged in a different way; 
     FIG. 27 is a perspective view of a second conventional evaporator; 
     FIG. 28 is a schematic perspective view of the second conventional evaporator, showing the path of refrigerant in the evaporator; 
     FIG. 29 is a schematic perspective view of the second conventional evaporator, showing flow condition of refrigerant in the evaporator; 
     FIG. 30 is a schematic view of the second conventional evaporator, showing a temperature distribution possessed by the evaporator. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following, the present invention will be described in detail with reference to the accompanying drawings. For ease of understanding, directional terms, such as, right, left, upper, lower and the like are used. However, these directional terms are to be understood with respect to the drawings in which the objective structures or parts are illustrated. 
     Referring to FIGS. 1 to  13  of the drawings, particularly FIGS. 1,  2 ,  3 ,  7  and  10 , there is shown a stack type evaporator  100  according to the present invention. 
     As is seen from FIGS. 1,  2  and  3 , the evaporator  100  has a rectangular core unit  105  which comprises a first group of heat exchanging elements  111 , a second group of heat exchanging elements  112 , and a plurality of hear radiation fins  113  interposed between every adjacent two of the heat exchanging elements  111  and  112 . For ease of description, each of the first group of heat exchanging elements  111  will be referred to first heat exchanging element  111 , and each of the second group of heat exchanging elements  112  will be referred to second heat exchanging element  112 , hereinafter. 
     As is seen from FIGS. 1,  2  and  3 , at an upper middle portion of the core unit  105 , there are provided an inlet pipe connector  114  and an outlet pipe connector  115 . As is understood from FIG. 2, upon arrangement of the evaporator  100  in an associated automotive air conditioner, the evaporator  100  is so oriented as having the pipe connectors  114  and  115  directed against an air flow. The inlet pipe connector  114  is connected to an inlet pipe  103  through which a liquid-gaseous refrigerant is led into the core unit  105 , and the outlet pipe connector  115  is connected to an outlet pipe  104  through which a gaseous refrigerant is discharged from the core unit  105 . 
     As is seen from FIG. 8A, the inlet pipe connector  114  (or outlet pipe connector  115 ) has a circular opening with which an end of the inlet pipe  103  (or outlet pipe  104 ) is engaged and brazed. However, if desired, as is seen from FIG. 8B, the pipe  103  or  104  may have a connector  114  or  115  integrally connected thereto. In this case, a sealing piece  116  is used for shutting the open end of the integrated connector  114  or  115 . 
     Furthermore, as is seen from FIGS. 9B and 9C, the connector  114  or  115  may be integrated with a recessed metal plate  117  which is a part of an associated heat exchanging element  111  or  112 . 
     That is, as is shown in FIGS. 5A and 5B, each of the first group of heat exchanging elements  111  comprises two identical recessed metal plates  117 , only one being shown in the drawings. As is shown in FIGS. 6A and 6B, each of the second group of heat exchanging elements  112  comprises two identical recessed metal plates  118 , only one being shown in the drawings. 
     The two identical metal plates  117  and  117  (or,  118  and  118 ) are coupled in a so-called face-to-face connecting manner to define therebetween a hermetically sealed flat flow passage. More specifically, as is understood from FIGS. 4A and 5B, the first heat exchanging element  111  is constructed to have therein two parallel straight flow passages  120  and  121 , while, as is understood from FIGS. 4B and 6B, the second heat exchanging element  112  is constructed to have therein a U-shaped flow passage  122 , for the reason which will become apparent as the description proceeds. 
     As will be described hereinafter, one of the first and second recessed metal plates  117  and  118  may have such a structure as shown in FIG. 9A,  9 B or  9 C. If the structures as shown in FIGS. 9B and  9 C are used, reduction in number of parts is achieved because of the integrated formation of the connector  114  or  115 . 
     Each of the recessed metal plates  117  and  118  is a clad metal which includes an aluminum alloy core plate of higher melting point having both surfaces laminated with brazing aluminum alloy plates of lower melting point. Usually, adding silicon (Si) to the aluminum alloy lowers the melting point of the alloy. 
     For producing the evaporator  100 , a plurality of coupled metal plates  117  and  117  for the first group of heat exchanging elements  111 , a plurality of coupled metal plates  118  and  118  for the second group of heat exchanging elements  112 , a plurality of heat radiation fins  113 , inlet and outlet pipe connectors  114  and  115  and a pair of side plates  119  are temporarily assembled in a holder (not shown) in such an arrangement as shown in FIG. 1, and then the temporarily assembled unit is put into a brazing furnace (not shown) for a certain time to braze the parts. With this, the parts  117 ,  118 ,  113 ,  103 ,  104 ,  114 ,  115  and  119  are brazed to one another to constitute a fixed unit of the evaporator  100 . 
     As has been mentioned hereinabove, a right half of the stack type evaporator  100  (see FIG. 1) comprises a plurality of the first heat exchanging elements  111  (viz., first group of heat exchanging elements  111 ) and associated heat radiation fins  113 , and a left half of the evaporator  100  comprises a plurality of the second heat exchanging elements  112  (viz., second group of heat exchanging elements  112 ) and associated heat radiation fins  113 . 
     As is shown in FIG. 4A, each first heat exchanging element  111  has therein two parallel straight flow passages  120  and  121 , and as is shown in FIG. 4B, each second heat exchanging element  112  has therein a U-shaped flow passage  122 . 
     As is seen in FIG. 5B, each metal plate  117  for the first heat exchanging element  111  has at an upper end two (viz., first and second) circular openings  123  and  124 , and at a lower end two (viz., third and fourth) circular openings  125  and  126 , each opening  123 ,  124 ,  125  or  126  being defined in a depressed part of the upper or lower end of the plate  117 . Furthermore, each metal plate  117  has two parallel shallow grooves  127  and  128  which extend between the openings  123  and  125  and between the openings  124  and  126 , respectively. It is to be noted that the shallow groove  127  constitutes the straight flow passage  120  of the first heat exchanging element  111  (see FIG.  4 A), and the other shallow groove  128  constitutes the other straight flow passage  121  of the first heat exchanging element  111 . 
     As has been mentioned hereinabove, the two metal plates  117  and  117  are coupled in a face-to-face contacting manner to constitute the first heat exchanging element  111 . With this coupling, as is seen from FIG. 4A, the element  111  becomes to have at its upper end two (viz., first and second) tank spaces  129  and  130 , and at its lower end two (third and fourth) tank spaces  131  and  132 , the first tank space  129  being defined between the opening  123  of the metal plate  117  and the corresponding opening ( 124 ) of the partner metal plate  117 , the second tank space  130  being defined between the opening  124  of the metal plate  117  and the corresponding opening ( 123 ) of the partner metal plate  117 , the third tank space  131  being defined between the opening  125  of the metal plate  117  and the corresponding opening ( 126 ) of the partner metal plate  117  and the fourth tank space  132  being defined between the opening  126  of the metal plate  117  and the corresponding opening ( 125 ) of the partner metal plate  117 . 
     Furthermore, with the coupling between the two metal plates  117  and  117  for constituting the first heat exchanging element  111 , there are defined in the element  111  (see FIG. 4A) the two parallel straight flow passages  120  and  121 . The passage  120  extends between the first tank space  129  and the third tank space  131 , and the other passage  121  extends between the second tank space  130  and the fourth tank space  132 . 
     As is seen from FIG. 5B, bottom surfaces of the two parallel shallow grooves  127  and  128  of each metal plate  117  are formed with a plurality of studs  133 . Upon coupling between the paired metal plates  117  and  117 , the studs  133  of one metal plate  117  abut against the studs  133  of the partner&#39;s metal plate  117  respectively. These abutting studs  133  become brazed when heated in the brazing furnace. Due to provision of such studs  133 , the coupling between the paired metal plates  117  and  117  is assured and the refrigerant flow in the two flow passages  120  and  121  is suitably diffused. 
     As is seen in FIG. 6, each metal plate  118  for the second heat exchanging element  112  has an upper end two (fifth and sixth) circular openings  134  and  135 , and at a lower end two (viz., seventh and eighth) circular openings  136  and  137 , each opening  134 ,  135 ,  136  or  137  being defined in a depressed part of the upper and lower end of the plate  118 . Furthermore, each metal plate  118  has a U-shaped shallow groove  138  which comprises two parallel shallow groove parts (no numerals) each having one end connected to the seventh or eighth circular opening  136  or  137  and a short shallow groove part (no numeral) connecting the other ends of the two parallel shallow groove parts. It is to be noted that U-shaped shallow groove  138  constitutes the U-shaped flow passage  121  of the second heat exchanging element  112  (see FIG.  4 B). 
     As has been mentioned hereinabove, the two metal plates  118  and  118  are coupled in a face-to-face contacting manner to constitute the second heat exchanging element  112 . With this coupling, as is seen from FIG. 4B, the element  112  becomes to have at its upper end two (viz., fifth and sixth) tank spaces  139  and  140 , and at its lower end two (viz., seventh and eighth) tank spaces  141  and  142 , the fifth tank space  139  being defined between the opening  134  of the metal plate  118  and the corresponding opening ( 135 ) of the partner metal plate  118 , the sixth tank space  140  being defined between the opening  135  of the metal plate  118  and the corresponding opening ( 134 ) of the partner metal plate  118 , the seventh tank space  141  being defined between the opening  136  of the metal plate  118  and the corresponding opening ( 137 ) of the partner metal plate  118  and the eighth tank space  142  being defined between the opening  137  of the metal plate  118  and the corresponding opening ( 136 ) of the partner metal plate  118 . 
     Furthermore, with the coupling between the two metal plates  118  and  118  for constituting the second heat exchanging element  112 , there are defined in the element  112  (see FIG. 4B) the U-shaped flow passage  122 . This passage  122  extends between the seventh and eighth tank spaces  141  and  142 . It is to be noted that the passage  122  is isolated from the fifth and sixth tank spaces  139  and  140 , as is seen from the drawing (FIG.  4 B). 
     As is seen from FIG. 6B, a bottom surface of the U-shaped shallow groove  138  of each metal plate  118  is formed with a plurality of studs  133 . Upon coupling between the paired metal plates  118  and  118 , the studs  133  of one metal plate  118  abut against the studs  133  of the partner&#39;s metal plate  118  respectively. The abutting studs  133  become brazed when heated in the brazing furnace. If desired, the fifth and sixth tank spaces  139  and  140  may be removed. However, in this case, it becomes necessary to provide between the upper ends of any adjacent two of the second heat exchanging elements  112  and  112  a distance keeping element. 
     As is seen from FIGS. 3 and 7, upon assembly of the evaporator  100 , the first tank spaces  129  of the first heat exchanging elements  111  are aligned and connected to one another to constitute an inlet tank portion  143 . The inlet tank portion  143  is connected through the inlet pipe connector  114  to the inlet pipe  103 . It is to be noted that the rightmost one of the first metal plates  117  as viewed in FIGS. 1 and 3 has no opening corresponding to the opening  123  (see FIG.  5 B). 
     Furthermore, as is seen from FIGS. 3 and 7, upon assembly of the evaporator  100 , the second tank spaces  130  of the first heat exchanging elements  111  are aligned and connected to one another to constitute an outlet tank portion  145 . The outlet tank portion  145  is connected through the outlet pipe connector  115  to the outlet pipe  104 . It is to be noted that the rightmost one of the first metal plates  117  as viewed in FIGS. 1 and 3 has no opening corresponding to the opening  124  (see FIG.  5 B). 
     As is seen from FIG. 7, upon assembly, the third tank spaces  131  of the first heat exchanging elements  111  and the seventh tank spaces  141  of the second heat exchanging elements  112  are aligned and connected to one another to constitute a refrigerant flow upstream tank portion  146 . It is to be noted that the rightmost one of the second metal plates  118  as viewed in FIG. 7 has no opening corresponding to the opening  136  and the leftmost one of the first metal plates  117  has no opening corresponding to the opening  125 . 
     Furthermore, as is seen from FIG. 7, upon assembly, the fourth tank spaces  132  of the first heat exchanging elements  111  and the eighth tank spaces  142  of the second heat exchanging elements  112  are aligned and connected to one another to constitute a refrigerant flow downstream tank portion  147 . It is to be noted that the rightmost one of the second metal plates  118  as viewed in FIG. 7 has no opening corresponding to the opening  137  and the leftmost one of the first metal plates  117  has no opening corresponding to the opening  126 . 
     In the following, operation of the stack type evaporator  100  of the invention will be described with reference to FIGS. 7 and 10. 
     Under operation of the associated air conditioner, a liquid-gaseous refrigerant, which has been discharged from an expansion valve (not shown), is led into the inlet tank portion  143  through the inlet pipe connector  114  and the inlet pipe  103 . The refrigerant in the inlet tank portion  143  then flows down into the straight flow passages  120  of the first group heat exchanging elements  111  which are arranged at the left-half (as viewed in FIG. 7) and air downstream side of the core unit  105  of the evaporator  100 . The refrigerant in the straight flow passages  120  then flows into a left half part (as viewed in FIGS. 7 and 10) of the refrigerant flow upstream tank portion  146 . 
     The refrigerant led into the left-half part of the refrigerant flow upstream tank portion  146  flows in the portion  146  rightward in the drawing. Then, the refrigerant is led into the U-shaped flow passages  122  of the second group heat exchanging elements  112  which constitute the right-half part of the core unit  105  in the drawings. The refrigerant in the U-shaped flow passages  122  then flows into a right half part of the refrigerant flow downstream tank portion  147 . Then, the refrigerant flows leftward (as viewed in FIGS. 7 and 10) in the tank portion  147  and then flows upward into the straight flow passages  121  of the first groups heat exchanging elements  111 . The refrigerant then flows into the outlet tank portion  145  and then flows into a compressor through the outlet pipe connector  115  and the outlet pipe  104 . 
     During the above-mentioned flow in the core unit  105 , the refrigerant makes a heat exchanging with the air which flows through the core unit  105  in the direction of the arrow “α” of the drawings. Thus, the air is cooled by a certain degree. 
     As is easily understood from FIG. 10, due to the above-mentioned unique arrangement of the refrigerant flow passages, the refrigerant can flow evenly in both the air flow downstream part and the air flow upstream part of the core unit  105 . That is, the flow passages  120  through which the lowest temperature refrigerant flows are arranged just behind the flow passages  121  through which the highest temperature refrigerant flows, and the intermediate temperature refrigerant flows in the U-shaped flow passages  122  which extend between the air flow upstream and downstream parts of the core unit  105 . 
     Furthermore, as is understood from FIGS. 12 and 13, under operation, the inside side section “X” of the air flow downstream left-half part of the evaporator  100  is permitted to let a larger amount of liquid-gaseous refrigerant flow therethrough, and the outside section “Y” of the air flow upstream left-half part of the evaporator  100  is permitted to let a larger amount of gaseous refrigerant flow therethrough. It is to be noted that these two sections “X” and “Y” are not overlapped with respect to the direction in which the air “α” flows. This means that a relatively low temperature zone of the flow passages  120  and a relatively high temperature zone of the flow passages  121  are overlapped to each other with respect to the air flowing direction. 
     Thus, the core unit  105  of the evaporator  100  can have an even temperature distribution therethroughout. This provides the air passing through the core unit  105  with a uniformed temperature distribution, which makes the passengers comfortable. Furthermore, such even temperature distribution of the core unit  105  brings about an effective heat exchanging between the refrigerant flowing in the core unit  105  and the air passing through the core unit  105 . 
     In each of the right and left half parts (as viewed in FIGS. 7 and 10) of the core unit  105 , higher temperature refrigerant flows in the air flow upstream part of the core unit  105  and lower temperature refrigerant flows in the air flow downstream part of the unit  105 . This promotes the uniformed temperature distribution of the air passing through the core unit  105 . 
     As is described hereinabove, the evaporator  100  of the present invention is so oriented as having the pipe connectors  114  and  115  directed against the air flow. Thus, as is seen from FIG. 11, even when the evaporator  100  is arranged in parallel with the dash panel  8 , the connection of the inlet and outlet pipes  103  and  104  to the coupler  2  held by the dash panel  8  is readily and simply made, which brings about a low cost production of the automotive air conditioner as well as a smoothed air flow passing through the evaporator  100 . 
     Furthermore, since the evaporator  100  has no structure corresponding the side tank portion  7 ′ (see FIG. 28) possessed by the conventional evaporator  1 ′, lowering in heat exchanging performance caused by such side tank portion  7 ′ does not occur. 
     Referring to FIGS. 14 and 15, there is shown a first modification  100 A of the evaporator  100 . 
     In this first modification  100 A, the inlet pipe  103  is connected to a left end portion (as viewed in FIG. 14) of the core unit  105 , and the outlet pipe  104  is connected to a right end portion (as viewed in FIG. 14) of the core unit  105 . For this arrangement, the inlet tank portion  143  extends throughout the width of the core unit  105 , as shown. That is, in this modification  100 A, the first tank spaces  129  (see FIG. 7) of the first heat exchanging elements  111  and the fifth tank spaces  139  of the second heat exchanging elements  112  are connected to constitute the inlet tank portion  143 . The outlet tank portion  145  is arranged at a right half air flow upstream side of the core unit  105 , as shown in the drawing. 
     As is seen from FIG. 15, even when the modified evaporator  100 A is arranged in parallel with the dash panel  8 , the connection of the inlet and outlet pipes  103  and  104  to the coupler  2  is readily and simply made, which brings about a low cost production of the automotive air conditioner and a smoothed air flow passing through the evaporator  100 A. 
     Referring to FIGS. 16 to  21 , there is shown a second modification  100 B of the evaporator  100 . 
     As is seen from FIGS. 16 and 17, in this second modification  100 B, refrigerant inlet and outlet pipes  152  and  153  are connected through a connector  154  (see FIG. 18) to an upper portion of one side end of the core unit  105 . For this arrangement, the inlet tank portion  143  and the outlet tank portion  145  extend throughout the width of the core unit  105 . That is, the first tank spaces  129  of the first heat exchanging elements  111  and the fifth tank spaces  139  of the second heat exchanging elements  112  are connected to constitute the inlet tank portion  143 , and the second tank spaces  130  of the first heat exchanging elements  111  and the sixth tank spaces  140  of the second heat exchanging elements  112  are connected to constitute the outlet tank portion  145 . 
     As is seen from FIGS. 18 and 19, the connector  154  is secured to the outermost one of the second heat exchanging elements  112 . More specifically, as is seen from FIG. 19, the connector  154  is secured to the outside one of the paired recessed metal plates  118  of the element  112 . For this connection, the outside metal plate  118  is formed with two openings  155  and  156  which are respectively communicated with the fifth tank spaces  139  and the sixth tank spaces  140  of the core unit  105 . The inlet and outlet pipes  152  and  153  held by the connector  154  are respectively mated with the openings  155  and  156  of the outside metal plate  118 . The inlet pipe  152  extends to an expansion valve and the outlet pipe  153  extends to a compressor. 
     As is seen from FIGS. 20 and 21, also in this second modification  100 B, under operation, the inside side section “X” of the air flow downstream left-half part of the evaporator  100 B is permitted to let a larger amount of liquid-gaseous refrigerant flow therethrough, and the outside section “Y” of the air flow upstream left-half part of the evaporator  100 B is permitted to let a larger amount of gaseous refrigerant flow therethrough. Like in the case of the above-mentioned evaporator  100 , the two sections “X” and “Y” are not overlapped with respect to the direction in which the air “α” flows. That is, also in this second modification  100 B, a relatively low temperature zone of the flow passages  120  and a relatively high temperature zone of the flow passages  121  are overlapped to each other with respect to the air flowing direction. Thus, the core unit  105  of the evaporator  100 B can have an even temperature distribution therethroughout. 
     Furthermore, since, in this second modification  100 B (see FIG.  20 ), the inlet and outlet pipes  152  and  153  are aligned with the inlet and outlet tank portions  143  and  145  of the core unit  105 , the inflow of the refrigerant into the inlet tank portion  143  and the outflow of the refrigerant from the outlet tank portion  145  are smoothly carried out and thus the refrigerant flow resistance of the evaporator  100 B can be reduced. 
     Referring to FIG. 22, there is shown a third modification  100 C of the evaporator  100 . 
     Since this modification  100 C is similar in construction to the above-mentioned second modification  100 B, only parts different from those of the second modification  100 B will be described. 
     That is, as is shown in the drawing, a side plate  119 ′ provided with an extra side tank  158  is employed for reducing the dynamic pressure possessed by the refrigerant just fed to the core unit  105 . As shown, a passage  159  defined in the extra side tank  158  has one end connected to the inlet tank portion  143  and the other end connected to the refrigerant inlet pipe  152 . In this case, the dynamic pressure possessed by the refrigerant just fed to the core unit  105  is effectively reduced and thus undesired drift of the refrigerant flow in the flow passages  120  of the first heat exchanging elements  111  is suppressed or at least minimized. Even in this modification  100 C, the refrigerant outlet pipe  153  should be aligned with the outlet tank portion  145  because the gaseous refrigerant flowing in the outlet tank portion  145  is easily affected in flow resistance by the complication in structure of the flow passage as compared with the liquid-gaseous refrigerant fed into the core unit  105 . 
     Referring to FIG. 23, there is shown a third modification  100 D of the evaporator  100 . 
     As shown, in this fourth modification  100 D, refrigerant inlet and outlet pipes  152  and  153  are connected to laterally opposed ends of the core unit  105 . Furthermore, in this modification  100 D, the outlet tank portion  145  is provided at only one half part of the core unit  105 . That is, the second tank spaces  130  of the first heat exchanging elements  111  located at a right half (as viewed in FIG. 23) of the core unit  105  are connected to constitute the outlet tank portion  145 . 
     The entire contents of Japanese Patent Application P10-317145 (filed Nov. 9, 1998) and Japanese Patent Application P11-189273 (filed Jul. 2, 1999) are incorporated herein by reference. 
     Although the invention has been described above with reference to an embodiment of the invention and modifications of the same, the invention is not limited to such the embodiment and modifications as described above. Much larger modifications and variations of the invention described above will occur to those skilled in the art, in light of the above teachings.