Patent Publication Number: US-2002007646-A1

Title: Condenser

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a condenser suitably used for, for example, a refrigeration system for car air-conditioners.  
       [0003] 2. Description of Related Art  
       [0004] As shown in FIG. 8, a conventional multi-flow type condenser for use in car air-conditioners includes a pair of vertical headers  1  and  1  disposed apart from each other and a plurality of horizontal flat tubes  2  as heat exchanging tubes disposed between the headers at certain intervals in the direction of up-and-down with their opposite ends connected with the headers. One of the headers  1  is provided with a refrigerant inlet  1   a  at the upper end portion thereof, and the other header  1  is provided with a refrigerant outlet  1   b  at the lower portion thereof. Furthermore, the headers  1  are provided with partitions  5  each disposed at a predetermined portion for dividing the inside of the header to thereby group the aforementioned plurality of flat tubes  2  into a plurality of paths P 1  to P 3 .  
       [0005] Thus, in this condenser, the refrigerant introduced from the refrigerant inlet  1   a  passes downwardly through each path P 1  to P 3  in sequence in a meandering manner, and then flows out of the refrigerant outlet  1   b . During passing through these paths, the refrigerant exchanges heat with the ambient air to be condensed into a liquefied refrigerant.  
       [0006] The inventors of the present application analyzed the stagnation of the liquefied refrigerant in the aforementioned condenser by using a thermography. According to the results of the analysis, as shown in FIGS. 9 and 10, the liquefied refrigerant RL tends to stagnate at the downstream lower portion in each path P 1 -P 3 . In detail, in the conventional condenser, the liquefaction of refrigerant has already started at the end portion in the first path P 1 . Therefore, the liquefied refrigerant RL stays at the bottom of the header portion connecting the first and second paths P 1  and P 2 , which may cause the so-called liquid stagnation. Since this stagnated liquefied refrigerant RL blockades the tube-inlets of the lower portion of the second path P 2 , only the liquefied refrigerant RL flows into the lower tubes  2  of the second path P 2 . Similarly, only the liquefied refrigerant RL flows into the lower tubes  2  of the third path P 3 . Since those portions through which only the liquefied refrigerant RL flows cannot perform efficient heat exchanging, an effective heat transfer area decreases, which causes deterioration in the refrigeration performance.  
       [0007] Furthermore, the liquefied refrigerant RL impedes the refrigerant circulation, resulting in an increased refrigerant flow resistance.  
       SUMMARY OF THE INVENTION  
       [0008] It is an object of the present invention to provide a condenser having a decreased refrigerant flow resistance and an improved cooling performance.  
       [0009] According to a first aspect of the present invention, a condenser includes a pair of right and left headers, a plurality of heat exchanging tubes disposed between the headers with opposite ends thereof connected with the headers, at least one partition provided in one of the headers to group the plurality of heat exchanging tubes into a plurality of paths, a refrigerant inlet provided at a lower portion of one of the headers and a refrigerant outlet provided at an upper portion of one of the headers. A refrigerant introduced from the refrigerant inlet passes upwardly through the plurality of paths in sequence in a meandering manner, and flows out of the refrigerant outlet. A cross-sectional area of each of the paths decreases stepwise towards a downstream side of the paths for each path, and that a reduction rate of a cross-sectional area of a downstream side path of adjacent two paths to a cross-sectional area of an upstream side path thereof is 20% or more.  
       [0010] With this condenser, the gaseous refrigerant flowed out of the heat exchanging tubes constituting the upstream side path (lower side path) goes up vigorously in the refrigerant turning portion of the header connecting the adjacent paths, and the rising refrigerant flows into the heat exchanging tubes constituting the downstream side path (upper side path). Thus, the liquefied refrigerant is pushed up by the blow-up effect of this rising refrigerant, and flows into the heat exchanging tubes constituting the downstream side path (upper side path) smoothly. This prevents a stagnation of the liquefied refrigerant, which keeps a large effective heat transferring area of the heat exchanging portion and enables an equally distributed smooth refrigerant flow in each path.  
       [0011] It is preferable that the plurality of paths is comprised of three or more paths including a first path, a second path and a third path through which the refrigerant introduced from the refrigerant inlet passes in sequence, a reduction rate of a cross-sectional area of the second path to a cross-sectional area of the first path is 50% or more, and a reduction rate of a cross-sectional area of the third path to a cross-sectional area of the second path is 40% or more. In this case, the aforementioned refrigerant blow-up effect by the refrigerant turning portion connecting the adjacent paths can fully be obtained, which can assuredly prevent the stagnation of the liquefied refrigerant in the refrigerant turning portion.  
       [0012] According to a second aspect of the present invention, a condenser includes a plurality of paths arranged one on the other, each of the paths including a plurality of heat exchanging tubes, a header portion connected to corresponding ends of adjacent upper and lower paths, a refrigerant inlet provided at a lowermost path; and a refrigerant outlet provided at an uppermost path. A refrigerant introduced from the refrigerant inlet goes upwardly from the lowermost path towards the uppermost path while making a U-turn in the header portion, and flows out of the refrigerant outlet. Furthermore, a reduction rate of a cross-sectional area of a downstream side path of adjacent two paths to a cross-sectional area of an upstream side path thereof is 20% or more.  
       [0013] In this case too, the liquefied refrigerant is pushed up by the blow-up effect of the rising refrigerant, and flows into the heat exchanging tubes constituting the downstream side path (upper side path) smoothly. This prevents a stagnation of the liquefied refrigerant, which keeps a large effective heat transferring area of the heat exchanging portion and enables an equally distributed smooth refrigerant flow in each path.  
       [0014] According to a third aspect of the present invention, a condenser includes a first header portion with a refrigerant inlet, a lowermost first path including a plurality of heat exchanging tubes whose one end being connected with the first header portion, a final header portion with a refrigerant outlet, an uppermost final path including a plurality of heat exchanging tubes whose one end being connected with the final header portion, one or a plurality of middle paths each including a plurality of heat exchanging tubes, and a plurality of middle header portions each connecting corresponding one ends of adjacent paths. A refrigerant introduced from the refrigerant inlet flows upwardly through the plurality of paths in sequence in a meandering manner via each of the header portions, and flows out of the refrigerant. Furthermore, a reduction rate of a cross-sectional area of a downstream side path of adjacent two paths to a cross-sectional area of an upstream side path thereof is 20% or more.  
       [0015] With this condenser too, the liquefied refrigerant is pushed up by the blow-up effect of this rising refrigerant, and flows into the heat exchanging tubes constituting the downstream side path (upper side path) smoothly. This prevents a stagnation of the liquefied refrigerant, which keeps a large effective heat transferring area of the heat exchanging portion and enables an equally distributed smooth refrigerant flow in each path. 
     
    
    
     [0016] Other objects and the features will be apparent from the following detailed description of the present invention with reference to the attached drawings.  
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017] The present invention will be more fully described and better understood from the following description, taken with the appended drawings, in which:  
     [0018]FIG. 1 is a front view showing a condenser for use in car air-conditioners according to an embodiment of the present invention;  
     [0019]FIG. 2 is a schematic front view showing a refrigerant circuit arrangement of the condenser according to the embodiment;  
     [0020]FIG. 3 is an enlarged cross-sectional view showing a first refrigerant turning portion and therearound of the condenser according to the embodiment;  
     [0021]FIG. 4 is a schematic cross-sectional view showing a refrigerant circuit arrangement of a condenser for use in car air-conditioners according to a second embodiment of the present invention;  
     [0022]FIG. 5 is a schematic cross-sectional view showing a refrigerant circuit arrangement of a condenser for use in car air-conditioners according to a third embodiment of the present invention;  
     [0023]FIG. 6 is a schematic cross-sectional view showing a refrigerant circuit arrangement of a condenser for use in car air-conditioners according to a comparative example;  
     [0024]FIG. 7 is a graph showing a relationship between a refrigerant flow resistance and a refrigerant circulation amount of the inventive and comparative condensers;  
     [0025]FIG. 8 is a partially omitted front view showing a conventional condenser for use in car air-conditioners;  
     [0026]FIG. 9 is a schematic front view showing a refrigerant circuit arrangement of the conventional condenser; and  
     [0027]FIG. 10 is a schematic cross-sectional view showing a first refrigerant turning portion and therearound of the conventional condenser. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0028]FIGS. 1 and 2 show a multi-flow type condenser for use in car air-conditioners according to an embodiment of the present invention.  
     [0029] As shown in these figures, this condenser has a pair of right and left headers  11  and  11  disposed at a certain distance. Between these headers  11  and  11 , a plurality of flat tubes  12  as heat exchanging tubes are horizontally disposed at certain intervals in the vertical direction with their opposites ends connected to the headers  11  and  11 . Furthermore, corrugate fins  13  are arranged between adjacent flat tubes  12  and disposed on the outermost flat tubes  12 . Furthermore, on the outside of each outermost corrugate fin  13 , a belt-shaped side plate  14  is disposed for protecting the outermost corrugated fin  13 .  
     [0030] At the lower side of one of headers  11  (right header), a refrigerant inlet  11   a  is provided. On the other hand, at the upper side of the other header  11  (left header), a refrigerant outlet  11   b  is provided.  
     [0031] Furthermore, at a predetermined portion or each header  11 , a partition  16  which divides the interior of the header  11  in the longitudinal direction thereof is provided, to thereby group the aforementioned plurality of flat tubes  12  into three paths, the first path P 1  (lowermost path), the second path P 2  (middle path) and the third path P 3  (uppermost path).  
     [0032] The header portion of the left header  11  which connects the first path P 1  with the second paths P 1  and P 2  constitutes a first refrigerant turning portion T 1 , and the header portion of the right header  11  which connects the second P 2  with the third paths P 3  constitutes a second refrigerant turning portion T 2 .  
     [0033] In the aforementioned embodiment, although the header portion constituting the turning portion T 1  or T 2  is formed by dividing a single cylindrical header  11  with partition  16 , the present invention is not limited to this. For example, each header portion constituting the turning portion T 1  and T 2  may be formed by a separate individual header pipe.  
     [0034] In this embodiment, each path P 1 -P 3  is decreased in cross-sectional area stepwise towards the downstream side path (upper side path) for each path. In the present invention, the reduction rate of the cross-sectional area of the downstream side path (upper side path) of the two adjacent paths to the upstream side path (lower side path) thereof should be set to 20% or more, and it is preferable that the reduction rate is set to 30% or more. The aforementioned reduction rate (%) can be obtained by the following formula: (1−PL/PU)×100(%), where “PU” is a cross-sectional area of the upstream side path and “PL” is that of the downstream side path. If the aforementioned reduction rate is smaller than 20%, an enough flow velocity (vigor) of the refrigerant cannot fully be secured in the refrigerant turning portion T 1  and T 2  in the header  11  between the adjacent paths, resulting in an inefficient refrigerant blow-up effect, which in turn may cause a liquefied refrigerant stagnation.  
     [0035] In the present invention, it is preferably that the aforementioned reduction rate is set to 25% or more in any two adjacent paths. It is more preferable that the reduction rate of the cross-sectional area of the second path to the cross-sectional area of the first path is 50% or more and that the reduction rate of the cross-sectional area of the third path to the cross-sectional area of the second path is 40% or more.  
     [0036] In the condenser of this embodiment, all of the flat tubes  12  have the same structure, and therefore the cross-sectional area of each path P 1 -P 3  is in proportion to the number of tubes of each path P 1 -P 3 . Therefore, the reduction rate of the cross-sectional area between adjacent paths corresponds to the reduction rate of the number of tubes between the adjacent paths. In the condenser of this embodiment, as shown in FIG. 2, the first path P 1  includes 22 flat tubes, the second path P 2  includes 9 flat tubes and the third path P 3  includes 5 flat tubes. Accordingly, the reduction rate of the cross-sectional areas between the first and second paths P 1  and P 2  is 59.1%, and that between the second and third paths P 2  and P 3  is 44.4%.  
     [0037] In the present invention, however, the reduction rate of the cross-sectional areas between adjacent paths may be set such that each path is constituted by the same number of tubes having different cross-sectional area.  
     [0038] In the present invention, although the total number of the paths is not especially limited, it is preferable that the total number is set to 2 to 5, more preferably 3 or 4. The most suitable total number is 3. If the total number of paths is set too much, the reduction rate of the cross-sectional areas between adjacent paths, i.e., the reduction rate of the tube number between the adjacent paths in the aforementioned embodiment, becomes too small, which causes a trouble in securing the aforementioned reduction rate. Thus, an effective refrigerant blow-up effect may not be obtained.  
     [0039] Furthermore, in the present invention, it is preferable that the cross-sectional area of each path is decreased stepwise for every path towards the downstream side (upper side). However, the heat exchange core may include adjacent paths each having the same cross-sectional area. Therefore, it should be understood that the present invention covers such a condenser including adjacent paths each having the same cross-sectional area, unless otherwise clearly defined.  
     [0040] Returning to the condenser of the aforementioned embodiment, the refrigerant introduced from the refrigerant inlet  11   a  passes upwardly through the first to third paths P 1 -P 3  in sequence in a meandering manner, and flows out of the refrigerant outlet  11   b . While passing through these paths, the refrigerant exchanges heat with the ambient air to be gradually condensed and liquefied.  
     [0041] At this time, the liquefaction of the gaseous refrigerant introduced from the refrigerant inlet  11   a  starts at the end portion of the first path P 1 , for example, and the liquefied refrigerant RL flows out of the tube-outlets of the first path P 1  and tends to flow downwards in the first refrigerant turning portion T 1 , as shown in FIG. 3. On the other hand, the gaseous refrigerant RG flows out of the tube-outlets of the first path P 1 , and goes up vigorously in the first turning portion T 1 . This rising gaseous refrigerant RG pushes up the aforementioned liquefied refrigerant RL. Thus, the liquefied refrigerant RL goes up in the first refrigerant turning portion T 1  together with the gaseous refrigerant RG, and this rising mixture of refrigerant will be evenly distributed into each flat tube  12  constituting the second path P 2  smoothly.  
     [0042] In this embodiment, since the cross-sectional area of the second path P 2  is set to the aforementioned specific reduction rate to that of the first path P 1 , the flow velocity of the gaseous refrigerant rising in the first refrigerant turning portion T 1  between the first and second paths P 1  and P 2  can be secured enough. Therefore, a sufficient blow-up effect in the refrigerant turning portion T 1  can be obtained by the rising refrigerant, which in turn can prevent assuredly the stagnation of the liquefied refrigerant RL in the bottom portion of the refrigerant turning portion T 1 .  
     [0043] Regarding the refrigerant which will flow into the third path P 3  through the second refrigerant turning portion T 2  from the second path P 2 , a similar phenomenon can be observed. The gaseous refrigerant RG which goes up vigorously in the second refrigerant turning portion T 2  will push up the liquefied refrigerant RL which tends to flow down, and therefore this rising refrigerant can flow into each flat tube  12  constituting the third path P 3  smoothly. As a result, a liquid stagnation by the liquefied refrigerant can be prevented.  
     [0044] Thus, according to the condenser of this embodiment, since a stagnation of the liquefied refrigerant can be prevented, the whole core surface can be used effectively as a heat exchanging portion, resulting in an improved cooling performance.  
     [0045] Furthermore, since the refrigerant will not stagnate and will pass through the whole region of each path in an evenly distributed manner, the refrigerant flow resistance can be reduced, resulting in a further enhanced heat exchanging performance.  
     [0046] Next, examples according to the present invention and a comparative example will be explained.  
     FIRST EXAMPLE  
     [0047] A condenser was manufactured in accordance with the aforementioned embodiment shown in FIGS. 1 and 2. This condenser has three paths, i.e., the lowermost first path P 1 , the middle second path P 2  and the uppermost third path P 3 . The first, second and third paths P 1 , P 2  and P 3  include twenty-two (22) tubes, nine (9) tubes and five (5) tubes, respectively. In this condenser, the reduction rate of the cross-sectional area of the second path P 2  to that of the first path P 1  is 59.1%, and the reduction rate of the cross-sectional area of the third path P 3  to that of the second path P 2  is 44.4%  
     SECOND EXAMPLE  
     [0048] As shown in FIG. 4, a condenser having three paths, i.e., the lowermost first path P 1 , the middle second path P 2  and the uppermost third path P 3 , was manufactured. The first, second and third paths P 1 , P 2  and P 3  include eighteen ( 1   a ) tubes, nine (9) tubes and five (5) tubes, respectively. Another structure is the same as the condenser of the first example. In this condenser, the reduction rate of the cross-sectional area of the second path P 2  to that of the first path P 1  is 50%, and the reduction rate of the cross-sectional area of the third path P 3  to that of the second path P 2  is 44.4%  
     [0049] In the second embodiment shown in FIG. 4, the same or corresponding reference numeral as in the first example are allotted to the same portion or corresponding portion (Similarly, the same or corresponding reference numeral will be allotted in the following third example shown in FIG. 5 and the following comparative example shown in FIG. 6).  
     THIRD EXAMPLE  
     [0050] As shown in FIG. 5, a condenser having four paths, i.e., the lowermost first path P 1 , the lower middle second path P 2 , the upper middle third path P 3  and the uppermost fourth path P 4 , was manufactured. The first, second, third and fourth paths P 1 , P 2 , P 3  and P 4  include thirteen (13) tubes, nine (9) tubes, six (6) tubes and four (4) tubes, respectively. Another structure is the same as the condenser of the first example. In this condenser, the reduction rate of the cross-sectional area of the second path P 2  to that of the first path P 1  is 30.8%, the reduction rate of the cross-sectional area of the third path P 3  to that of the second path P 2  is 33.3% and the reduction rate of the cross-sectional area of the fourth path P 4  to that of the third path P 3  is 33.3%. In FIG. 5, the reference numeral T 4  denotes a fourth refrigerant turning portion (the same numeral will be used in FIG. 6)  
     COMPARATIVE EXAMPLE  
     [0051] As shown in FIG. 6, a condenser having four paths, i.e., the uppermost first path P 1 , the upper middle second path P 2 , the lower middle third path P 3  and the lowermost fourth path P 4 , was manufactured. The first, second, third and fourth paths P 1 , P 2 , P 3  and P 4  include thirteen (13) tubes, nine (9) tubes, six (6) tubes and four (4) tubes, respectively. Another structure is the same as the condenser of the first example. This condenser according to the comparative example has a symmetrical configuration rotated by 180 degrees to the aforementioned condenser according to the third example. Accordingly, in this condenser, the reduction rate of the cross-sectional area of the second path P 2  to that of the first path P 1  is 30.8%, the reduction rate of the cross-sectional area of the third path P 3  to that of the second path P 2  is 33.3% and the reduction rate of the cross-sectional area of the fourth path P 4  to that of the third path P 3  is 33.3%.  
     [0052] &lt;Evaluation on a Stagnated Liquid Refrigerant&gt; 
     [0053] In the aforementioned examples and comparative example, it was observed whether or not a liquefied refrigerant (low-temperature refrigerant) stagnates based on the temperature distribution of a thermography image. According to the observation, in the condensers of the first to third examples, the refrigerant temperature decreased gradually towards the downstream portion in each path, there was no variation in temperature distribution, and no stagnation of a liquefied refrigerant was observed. Furthermore, in the condenser according to the comparative example, a low-temperature region existed in the lower portion in each path, and a stagnation of the liquefied refrigerant was observed in the lower portion.  
     [0054] &lt;Evaluation on Refrigerant Flow Resistance&gt; 
     [0055] The relation between the refrigerant flow resistance (kPa) and the refrigerant circulation amount (kg/h) in each condenser of the aforementioned examples and comparative example were measured. The measured results are shown in the graph of FIG. 7. In this graph, “A 1 ,” “A 2 ,” and “A 3 ” denote the first, second and third examples, respectively, and “B” denotes the comparative example.  
     [0056] As will be apparent from this graph, in the condenser according to the first to third examples A 1 -A 3 , the refrigerant flow resistance to a predetermined refrigerant circulation amount was decreased as compared with the condenser according to the comparative example.  
     [0057] Among these three examples, especially the first and second examples A 1  and A 2  were able to reduce flow resistance remarkably. The reason is considered as follows: since the reduction rate of the cross-sectional area of the second path P 2  to the cross-sectional area of the first path P 1  is set to 50% or more and the reduction rate of the cross-sectional area of the third path P 3  to the cross-sectional area of the second path P 2  is set to 40% or more, the refrigerant blow-up effect between adjacent paths could fully be obtained and therefore the circulation of the refrigerant could be performed much more smoothly.  
     [0058] Therefore, between adjacent paths, when the refrigerant flowed out of the upstream side path (lower side path) goes up and flows into the downstream side path (upper side path), the liquefied refrigerant is pushed up by the blow-up effect of the rising refrigerant and introduced into the downstream side path (upper side path). As a result, a stagnation of the liquid refrigerant can be prevented, securing an enough effective area of the heat exchanging portion, which enables an enhanced cooling performance. Furthermore, since the liquefied refrigerant passes through the entire region of each path without stagnating therein, the refrigerant flow resistance can be reduced, resulting in an enhanced performance. In cases where the reduction rate of the cross-sectional area between the predetermined adjacent paths is specified, the aforementioned effects can be obtained assuredly.  
     [0059] This application claims priority to Japanese Patent Application No. 2000-183966 filed on Jun. 20, 2000, the disclosure of which is incorporated by reference in its entirety.  
     [0060] The terms and descriptions in this specification are used only for explanatory purposes and the present invention is not limited to these terms and descriptions. It should be appreciated that there are many modifications and substitutions without departing from the spirit and the scope of the present invention which is defined by the appended claims. A present invention permits any design-change, unless it deviates from the soul, if it is within the limits by which the claim was performed.