Patent Publication Number: US-2015083383-A1

Title: Heat exchanger and heat exchange method

Description:
TECHNICAL FIELD 
     The present invention relates to a heat exchanger and a heat exchange method. 
     BACKGROUND ART 
     As one type of the heat exchanger, a parallel flow type heat exchanger is given. This heat exchanger includes a pair of header pipes, and a plurality of flat pipes provided between those header pipes. This heat exchanger is configured so that after a fluid, which has flowed into one of the headers, flows through the plurality of flat pipes, the fluid flows out to the other of the header pipes. 
     In this parallel flow type heat exchanger, when the pair of header pipes is arranged in a vertical up-and-down direction, due to an influence of the gravity, liquid refrigerant in gas-liquid two phase refrigerant is liable to flow into flat pipes positioned on a relatively lower side, thereby being difficult to equally distribute the refrigerant to the plurality of flat pipes. 
     Therefore, the parallel flow type heat exchanger may have such a structure that the pair of header pipes is horizontally arranged, to thereby suppress the influence of the gravity mutually between the plurality of flat pipes. 
     On the other hand, an existing outdoor unit of an air conditioner may have such a structure that heat exchange surfaces are arranged in a plurality of surfaces of a housing of the outdoor unit. When the above-mentioned parallel flow type heat exchanger having the pair of header pipes horizontally arranged is caused to exert its function in the plurality of surfaces of the housing of the outdoor unit, it is necessary to curve each of the header pipes along the plurality of surfaces. However, when the header pipe is curved into, for example, an L-shape or a U-shape, significant loads are applied, and hence there arise problems in that the apparatus is upsized and cost is increased. 
     To address those problems, for example, a heat exchanger disclosed in Patent Literature 1 is given. In the heat exchanger disclosed in Patent Literature 1, a pair of header pipes has been prepared separately for each of a plurality of surfaces. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] JP 2010-107103 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the above-mentioned heat exchanger disclosed in Patent Literature 1 has employed such a mode that after the refrigerant, which has flowed through a plurality of flat pipes in certain one surface (first surface), is collected to the header pipe on the outflow side of the one surface (first surface), the refrigerant is guided from this header pipe to the header pipe on the inflow side of the next surface (second surface) and distributed through a plurality of flat pipes of the next surface (second surface), and subsequently, the refrigerant is likewise guided to the next surface in sequence depending on the number of surfaces. 
     For this reason, an upstream/downstream relationship is generated among a plurality of heat exchange function surface units, and heat exchange efficiency is more reduced in the surface of the downstream side. In addition, the branch to a plurality of flat pipes and the collection following the branch are repeated, and hence there is a fear in that in the second and subsequent surfaces, the refrigerant after the heat exchange cannot be suitably branched to the plurality of flat pipes again. 
     The present invention has been made in view of the foregoing, and it is therefore an object of the present invention to provide a heat exchanger and the like, each of which is capable of suppressing, even with a plurality of heat exchange function surface units, an influence of the gravity exerted on refrigerant, and suppressing reduction of heat exchange performance in each of the surfaces. 
     Solution to Problem 
     In order to achieve the above-mentioned object, according to one embodiment of the present invention, there is provided a heat exchanger comprising: a plurality of heat exchange function surface units; each of the plurality of heat exchange function surface units having an upper header pipe, a lower header pipe, and a plurality of heat exchange pipes provided between a pair of the upper header pipe and the lower header pipe; the plurality of heat exchange function surface units having a parallel connection relationship; a plurality of the lower header pipes being connected to a lower collection pipe through a branch current adjusting section. 
     Further, in order to achieve the same object, according to another embodiment of the present invention, there is provided a heat exchange method of carrying out heat exchange in a plurality of surfaces, the heat exchange method including: preparing an upper header pipe, a lower header pipe, and a plurality of heat exchange pipes provided between a pair of the upper header pipe and the lower header pipe in each of a plurality of heat exchange function surface units; connecting the plurality of heat exchange function surface units in parallel, and connecting a plurality of the lower header pipes to a lower collection pipe through a branch current adjusting section; and branching, by the branch current adjusting section, refrigerant inside the lower collection pipe in parallel to the plurality of heat exchange function surface units, subjecting the refrigerant to the heat exchange in the each of the plurality of heat exchange function surface units, and causing the refrigerant to flow out from a plurality of the upper header pipes so as to be joined together to an upper side collection pipe. 
     Advantageous Effects of Invention 
     According to one embodiment of the present invention, it is possible to suppress, even with the plurality of heat exchange function surface units, the influence of the gravity exerted on the refrigerant, and suppress the reduction of the heat exchange performance in each of the surfaces. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a structure of a heat exchanger according to a first embodiment of the present invention. 
         FIG. 2  is a perspective view of a lower header pipe, for illustrating a perforated pipe. 
         FIG. 3  is a diagram illustrating liquid distribution characteristics of a lower header pipe as an example for comparing. 
         FIG. 4  is a diagram illustrating liquid distribution characteristics of a perforated pipe built-in type lower header pipe according to the first embodiment of the present invention. 
         FIG. 5  is a view illustrating an external appearance and plan view of a multi-air conditioner outdoor unit for a building according to the first embodiment of the present invention. 
         FIG. 6  is a view illustrating an external appearance and plan view of a package air conditioner outdoor unit according to a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Now, a heat exchanger and a heat exchange method according to embodiments of the present invention are described with reference to the accompanying drawings. Note that, in the drawings, the same reference symbols represent the same or corresponding parts. 
     First Embodiment 
       FIG. 1  is a view illustrating a structure of a heat exchanger according to a first embodiment of the present invention. The heat exchanger of this embodiment functions as an outdoor unit of an air conditioner that is installed in a space of intended use, and carries out heating and cooling. Therefore, the heat exchanger is a parallel flow type heat exchanger in which when the heat exchanger operates as a condenser in a phase of the cooling, refrigerant flows from the top to the bottom as indicated by dotted line arrows in  FIG. 1 , and when the heat exchanger operates as an evaporator in a phase of the heating, the refrigerant flows from the bottom to the top as indicated by solid line arrows in  FIG. 1 . 
     A heat exchanger  1  has a plurality of heat exchange function surface units  3 . Note that,  FIG. 1  illustrates an example in which three heat exchange function surface units  3  are provided. In addition, in the example of  FIG. 1 , the adjacent heat exchange function surface units  3  are structured so as to be directed orthogonal to each other. 
     An upper header pipe  5 , a lower header pipe  7 , and a plurality of heat exchange pipes  9  provided between the pair of upper and lower header pipes  5 ,  7  are provided in each of the heat exchange function surface units  3 . Specifically, a flat pipe is used as the heat exchange pipe  9 . A fin  11  (specifically, a corrugated fin) is provided between the heat exchange pipes  9 . 
     One end of an upper communication pipe  13  is connected to each of the upper header pipes  5 . The other end side of the upper communication pipe  13  is connected to an upper collection pipe  15 . Each of the lower header pipes  7  is connected to a lower collection pipe  19  through a branch current adjusting section  17  described later. In such a manner, the plurality of heat exchange function surface units  3  are arranged in a parallel connection relationship between the upper collection pipe  15  and the lower collection pipe  19 . Note that, although an illustration is omitted, it is assumed that a pair of the adjacent heat exchange function surface units  3  is covered with a blocking member such as a metallic plate so that the fluid to be subjected to the heat exchange is not bypassed. 
     The branch current adjusting section  17  serves to adjust a dryness and a flow rate of the refrigerant to be supplied to the plurality of lower header pipes  7 . Note that, as an example, this embodiment is described in the form of a configuration in which when the refrigerant flows from the bottom to the top in the phase of the heating, gas-liquid two phase refrigerant is supplied to the plurality of heat exchange function surface units  3  with the equal dryness and flow rate. 
     As an example of a configuration for realizing the equalization of such a dryness and a flow rate, the branch current adjusting section  17  includes a distributer  21  and at least one (two in the illustration) flow rate adjusting section  23 . One end side of the distributer  21  is connected to the lower collection pipe  19 , and a plurality of connection ports on the other end side thereof are connected to ends on one side of corresponding lower communication pipes  25 . In addition, ends on the other side of the lower communication pipes  25  are connected to collection side inlet and outlet ports  7   a  of the corresponding lower header pipes  7 , respectively. The distributer  21  connected in such a manner supplies the refrigerant to the plurality of lower communication pipes  25  with the equal dryness. 
     In the illustrated example, a capillary is used as the flow rate adjusting section  23 . Although the flow rate adjusting section  23  is provided between the distributer  21  and the corresponding lower header pipe  7 , that is, in the lower communication pipe  25 , the flow rate adjusting section  23  is not necessarily arranged in all the lower communication pipes  25 . 
     In each of the heat exchange function surface units  3 , the collection side inlet and outlet port  7   a  of the lower header pipe  7  and a collection side inlet and outlet port  5   a  of the upper header pipe  5  are positioned mutually opposite to each other in a direction in which the header pipe extends. In other words, the collection side inlet and outlet port  7   a  of the lower header pipe  7  is provided on one end side of the lower header pipe  7 , and the collection side inlet and outlet port  5   a  of the upper header pipe  5  is provided on the other end side of the upper header pipe  5 . That is, refrigerant distribution paths between the collection side inlet and outlet port  5   a  and the collection side inlet and outlet port  7   a  are designed so as to be approximately equal in flow path length even via any of the heat exchange pipes  9 . 
     As illustrated in  FIG. 2 , a perforated pipe  27  is provided inside each of the lower header pipes  7 .  FIG. 2  is a perspective view of the lower header pipe, for illustrating the perforated pipe. The plurality of heat exchange pipes  9  and communication holes with the plurality of heat exchange pipes  9 , which are supposed to be positioned above the lower header pipe  7 , are omitted in illustration thereof. 
     The perforated pipe  27  is a block-shaped or pipe-shaped member, and is provided approximately in the vicinity of the center of the space inside the lower header pipe  7  in a state in which the perforated pipe  27  is floated from an inner surface of the lower header pipe  7 . In addition, a large number of distribution holes  29  are formed in the perforated pipe  27 . As an example, the distribution holes  29  are arranged approximately in the lower section of the perforated pipe  27 . 
     A double pipe structure is obtained by a combination of such a perforated pipe  27  and the lower header pipe  7 . Therefore, for example, in the phase of the heating, after the refrigerant, which flows through the lower communication pipe  25 , temporarily flows into the perforated pipe  27 , the refrigerant equally flows out from the large number of distribution holes  29  to the outside of the perforated pipe  27  in a depth direction (in a horizontal direction of the drawing sheet of  FIG. 2 ). Further, the refrigerant is equally dispersed inside the lower header pipe  7  to be equally supplied from the communication holes (not shown) of the upper surface of the lower header pipe  7  to the plurality of heat exchange pipes  9 . 
     Next, a description is made of the effects of the perforated pipe described above.  FIG. 3  is a diagram illustrating liquid distribution characteristics of a lower header pipe as an example for comparing, which is horizontally arranged and does not have the perforated pipe.  FIG. 4  is a diagram illustrating liquid distribution characteristics of a perforated pipe built-in type lower header pipe according to this embodiment, which is horizontally arranged. 
     In addition, in graph parts of  FIG. 3  and  FIG. 4 , an axis of abscissa represents a path number, that is, numbers of flow paths of the heat exchange pipes arranged in the depth direction of the lower header pipe (flow paths of 28 flat pipes vertically inserted into the upper surface of the lower header pipe). An axis of ordinate represents a liquid distribution ratio for each path number. In addition, experimental results of three cases 1, 2, and 3 are shown, in which a refrigerant flow rate Gr [kg/hour] and an inlet port dryness X are changed with respect to the lower header pipes of the example for comparing and this embodiment. 
     First, in the example for comparing illustrated in  FIG. 3 , in the cases 1 and 3 in which the refrigerant flow rates Gr are each 90 [kg/hour] and the inlet port drynesses X are different from each other, the effect is not exhibited that the refrigerant is held in contact with the inside of a lower header pipe  7 ′, and hence does not bounce off the inside of the lower header pipe  7 ′. Therefore, it is understood that the refrigerant directly flows into the heat exchange pipes  9 , and hence the liquid distribution ratio is larger in the downstream region (the path numbers of No. 23 to 28). In addition, in the case 2 exhibiting the flow rate of 180 [kg/hour], which is more than that of each of the case 1 and the case 3, due to the presence of the liquid refrigerant that is abundantly supplied, the effect that the liquid refrigerant bounces off the inside of the lower header pipe  7 ′, or the flow is disturbed provides the tendency to relax imbalance characteristics of the liquid to a certain extent. However, any of the cases is out of an example of an equal distribution line indicated in parallel with the axis of abscissa. 
     On the other hand, in the perforated pipe built-in type lower header pipe of this embodiment illustrated in  FIG. 4 , it is understood that the satisfactory liquid distribution characteristics shown approximately along the equal distribution line are obtained in the three cases 1, 2, and 3 irrespective of the refrigerant flow rate and the inlet port dryness. This results from the following fact. That is, the perforated pipe  27  is inserted into the lower header pipe  7 , and the distribution holes  29  of the perforated pipe  27  are arranged in a downward direction of the perforated pipe  27 . In this way, an operation for stirring a liquid film of the refrigerant, which exists in an annular region surrounded by an inner surface of the lower header pipe  7 , and an outer surface of the perforated pipe  27 , by bubbles ejected from the bottom of the perforated pipe  27  is desirably obtained irrespective of the inlet port dryness and the flow rate. As a result, the equal distribution of the refrigerant is realized. 
     Subsequently, a description is made of a specific application example of the above-mentioned heat exchanger illustrated in  FIG. 1 . Although this embodiment exemplifies such a mode that the refrigerant dryness and the refrigerant flow rate are equally adjusted for the plurality of heat exchange function surface units  3 , an application to a multi-air conditioner outdoor unit for a building is given as the specific application example.  FIG. 5  is a view illustrating an outer appearance and plan view of the multi-air conditioner outdoor unit for a building. The multi-air conditioner outdoor unit for a building is employed as a high-performance apparatus that is larger in size than an outdoor unit for general home use. 
     As illustrated in  FIG. 5 , in a multi-air conditioner outdoor unit  101  for a building, the heat exchange function surface units  3  are allocated to three surfaces of a housing  103 , respectively. In plan view, a propeller fan  105  is arranged at the center of these heat exchange function surface units  3 . In addition, as indicated by arrows  107 , air is drawn into the housing  103  from three side surfaces of the housing  103  and is subjected to the heat exchange in the heat exchange function surface units  3 . Then, as indicated by arrows  111 , the air is ejected from an air outlet formed in a fan guard  109  provided on an upper surface of the housing  103  (top-flow type). 
     Next, a description is made of an operation of the heat exchanger constructed in such a manner and the heat exchange method according to this embodiment. In the phase of the heating operation, the heat exchanger  1  serving as the outdoor unit operates as an evaporator. The gas-liquid two phase refrigerant, which has entered the distributer  21 , becomes a uniform mist flow when passing through an orifice (not shown) to be supplied to each of the lower communication pipes  25 . Then, the uniform mist flow is adjusted in flow rate thereof in each of the flow rate adjusting sections  23  to flow into the lower header pipe  7  of the corresponding heat exchange function surface unit  3 . The refrigerant, which has flowed into the lower header pipe  7  through the collection side inlet and outlet port  7   a  of the lower header pipe  7 , is ejected from the distribution holes  29  of the perforated Pipe  27  to be equally distributed to the heat exchange pipes  9 . In the perforated pipe  27 , when the dryness is large, minute droplets are ejected from the small holes. When the dryness is small, the bubbles are ejected to the liquid part collected in the annular section. Therefore, the equal distribution is realized independently of the dryness and the flow rate. After the refrigerant is subjected to the heat exchange with the air (not shown) when having passed through the heat exchange pipes  9 , the refrigerant flows into the upper header pipe  5  and then flows out through the collection side inlet and outlet port  5   a  on the opposite side to the collection side inlet and outlet port  7   a  of the lower header pipe  7 . The refrigerant, which has flowed out through each of the collection side inlet and outlet ports  5   a , passes through the corresponding upper communication pipe  13  to join another refrigerant in the upper collection pipe  15 . Note that, in the phase of the cooling operation, the heat exchanger  1  operates as the condenser, and hence the flow of the refrigerant is reversed. 
     As has been described so far, according to the heat exchanger and the heat exchange method using the heat exchanger of the present invention, the following advantages are obtained. First, in the heat exchange function surface units, the header pipes are directed in the horizontal direction, and hence the influence of the gravity can be suppressed for the refrigerant distribution, and the refrigerant can be equally distributed to the plurality of heat exchange pipes. In addition, although the header pipes are horizontally arranged in such a manner, a plurality of surfaces can be controlled to exhibit the heat exchange function without being impeded by the actual situation that the curve of the header pipe is difficult to form. Moreover, although the heat exchange is carried out in a plurality of surfaces, the refrigerant is branched in distribution thereof in parallel to the plurality of heat exchange function surface units. Therefore, the upstream/downstream relationship is not generated mutually among the plurality of heat exchange function surface units, and hence the satisfactory heat exchange efficiency can be maintained in each of the heat exchange function surface units. In particular, in this embodiment, after the dryness and the flow rate of the refrigerant have been desirably adjusted depending on the conditions of the heat exchange function surface units through the distributor and the flow rate adjusting section, the refrigerant is supplied to the heat exchange function surface units in a distributive manner. Therefore, the very satisfactory heat exchange performance can be obtained in all the heat exchange function surface units. In addition, the entire heat exchanger does not have such a flow path that the refrigerant, which has been subjected to the heat exchange in the plurality of heat exchange pipes, is collected once, and is branched to the plurality of heat exchange pipes again. Therefore, there is no such problem that the refrigerant cannot be equally supplied to the plurality of heat exchange pipes. In such a manner, according to the heat exchanger and the heat exchange method of this embodiment, even with the plurality of heat exchange function surface units, the influence of the gravity exerted on the refrigerant can be suppressed, and the reduction of the heat exchange performance in each of the surfaces can be suppressed. 
     In addition, in each of the heat exchange function surface units, the inlet and outlet port of the lower header pipe and the inlet and outlet port of the upper header pipe are arranged on opposite sides to each other. Therefore, even when the refrigerant passes through any of the heat exchange pipes, the pressure losses become approximately equal to each other, that is, the equal distribution of the gas-liquid two phase flow can be realized. In addition, the perforated pipe is provided inside the lower header pipe, with the result that the minute droplets or the bubbles are ejected from the distribution holes to the annular section of the double structure, to thereby also promote the equal distribution of the gas-liquid two phase refrigerant. Moreover, in this embodiment, the number of distributions to the heat exchange pipes is increased, and the number of times of the distribution is suppressed low (in the example described above, the number of times of the distribution is only one). Therefore, although innumerable heat exchange pipes are used in order to prepare the plurality of heat exchange function surface units, the refrigerant pressure loss can be suppressed low relative to the number of heat exchange pipes. Therefore, in particular, low-pressure refrigerant (such as refrigerant exhibiting a large refrigerant pressure loss), for example, HFO1234yf, HFO1234ze, or R134a can also be effectively utilized. 
     Second Embodiment 
     A description is made of a second embodiment of the present invention with reference to  FIG. 6 . The first embodiment described above exemplifies such a mode that the refrigerant dryness is equally adjusted for the plurality of heat exchange function surface units, and the refrigerant flow rate is changed depending on the heat loads (mainly depend on the passing air velocity in the heat exchange section), which are different from one another in the heat exchange function surface units. However, the present invention is not limited to that mode. That is, the present invention also encompasses such a mode that the refrigerant drynesses and/or the refrigerant flow rates are adjusted so as to be different from one another in the plurality of heat exchange function surface units. As a specific application example, an application to a package air conditioner outdoor unit is given.  FIG. 6  illustrates an external appearance and plan view of the application to the package air conditioner outdoor unit. 
     As illustrated in  FIG. 6 , in a package air conditioner outdoor unit  201 , the heat exchange function surface units  3  are allocated to a side surface and a back surface of a housing  203 , respectively. By rotation of a propeller fan  205 , as indicated by arrows  207 , the air is drawn into the housing  203  from the side surface and the back surface of the housing  203 , and is subjected to the heat exchange in the heat exchange function surface units  3 . Then, as indicated by arrows  211 , the air is ejected from an air outlet provided in the front surface of the housing  203 . 
     According to the second embodiment as well, similarly to the first embodiment, even with the plurality of heat exchange function surface units, the influence of the gravity exerted on the refrigerant can be suppressed, and the reduction of the heat exchange performance in each of the surfaces can be suppressed. 
     The details of the present invention have been described above specifically with reference to the preferred embodiments, but it is apparent that a person skilled in the art may employ various modifications based on the basic technical thoughts and teachings of the present invention. 
     For example, although in the perforated pipe described above, the large number of distribution holes have been described as being provided in the downward direction, the mode of formation of the distribution holes is not limited thereto, and the orientation, the number, and the hole shape of the distribution holes may be suitably changed. In addition, the structure of the branch current adjusting section described above is also merely an example, and hence may be suitably changed. For example, there may also be used a branch current adjusting section having such a mode that height positions of a plurality of outlet port side branching pipes such as Y-shaped branching pipes or low-pressure loss distributers are made different from one another, a rate of a branch current of a liquid phase is changed by an influence of the gravity, and the dryness and the flow rate are simultaneously adjusted. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  heat exchanger,  3  heat exchange function surface unit,  5  upper header pipe,  7  lower header pipe,  5   a ,  7   a  collection side inlet and outlet port,  9  heat exchange pipe,  17  branch current adjusting section,  19  lower collection pipe,  21  distributer,  23  flow rate adjusting section,  25  lower communication pipe,  27  perforated pipe,  29  distribution hole.