Patent Publication Number: US-10775081-B2

Title: Heat exchanger and air conditioner

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage application of PCT/JP2016/058533 filed on Mar. 17, 2016, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a heat exchanger and an air conditioner including the heat exchanger. 
     BACKGROUND ART 
     A conventionally known heat exchanger includes a pair of headers facing each other horizontally in its upper and lower portions, a plurality of flat heat transfer tubes communicatively connected in parallel with the headers at uniform intervals, and corrugated fins provided in a gap between the flat heat transfer tubes to be brought into intimate contact with the tubes. The heat exchanger causes refrigerant that is a heat exchange medium to be distributed in parallel to the plurality of flat heat transfer tubes simultaneously. 
     When such a heat exchanger is subjected to a heating operation in cold weather as an air conditioner outdoor unit of heat pump type for cooling and heating, frost is formed on the fin and the surface of the heat transfer tube, decreasing a heat exchange efficiency. 
     Japanese Patent Laying-Open No. 09-280754 (PTD 1) discloses a heat exchanger to take a measure against such frost formation. The heat exchanger includes corrugated fins disposed to project windward from flat heat transfer tubes and includes louvers formed only in its leeward portion. 
     CITATION LIST 
     Patent Document 
     PTD 1: Japanese Patent Laying-Open No. 09-280754 
     SUMMARY OF INVENTION 
     Technical Problem 
     Although the heat exchanger described in PTD 1 includes fins projecting windward of a refrigerant flow paths (flat tubes) and can accordingly prevent or reduce the frost formation on the fins located windward, it suffers from a low defrosting efficiency on the fins. For example, the frost on the fin is melted into water through the defrosting operation, and the water is drained through the fins and the heat transfer tubes. However, the fin includes many regions extending horizontally, allowing the water to easily stay on the fin. In particular, water is drained only through the fin in the portion projecting windward in the fin of the heat exchanger, allowing water to easily stay on the fin, which leads to poor drainage efficiency. This results in a low defrosting efficiency of the heat exchanger. 
     The present invention has been made to solve the above problem. At an object of the present invention is to provide a heat exchanger capable of reducing frost formation on a fin and having high defrosting efficiency. 
     Solution to Problem 
     A heat exchanger according to the present invention includes at least one heat transfer tube which is provided to extend in a first direction and in which refrigerant flows, a fin connected to the at least one heat transfer tube and having a first region and a second region which are located windward of the at least one heat transfer tube in a second direction crossing the first direction, and a first guide member provided to extend in the first direction. The first region and the second region are spaced apart from each other in a third direction crossing the first direction and the second direction. The first guide member is disposed between the first region and the second region in the third direction. Among the at least one heat transfer tube and the first guide member, the first guide member is disposed most windward in the second direction. 
     An air conditioner according to the present invention includes a heat exchanger according to the present invention and a fan configured to blow a gas to the heat exchanger in the second direction. 
     Advantageous Effects of Invention 
     The present invention can provide a heat exchanger with high defrosting efficiency capable of preventing or reducing frost formation on a fin. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows a heat exchanger and an air conditioner according to Embodiment 1. 
         FIG. 2  is a schematic view of the heat exchanger according to Embodiment 1. 
         FIG. 3  is a partially enlarged view of the heat exchanger shown in  FIG. 2 . 
         FIG. 4  is a sectional view for illustrating fins of the heat exchanger shown in  FIG. 3 . 
         FIG. 5( a )  is a plan view of one fin and two heat transfer tubes adjacent to each other with the one fin therebetween, namely, a first heat transfer tube and a second heat transfer tube, in the heat exchanger shown in  FIG. 3 .  FIG. 5( b )  is a graph showing the distribution of the temperature of a surface of the fin shown in (a) during heating operation, and the distribution of the temperature of air passing through on the surface.  FIG. 5( c )  is a graph showing the distribution of the amount of heat exchange between the fin and air on the fin shown in (a) during heating operation. 
         FIG. 6  is an end view taken along a line segment VI-VI of  FIG. 5( a )  during defrosting operation. 
         FIG. 7  is an end view taken along a line segment VII-VII of  FIG. 5( a )  during defrosting operation. 
         FIG. 8  is a sectional view showing an example configuration of a first guide member in Embodiment 1. 
         FIG. 9  is a schematic view of an example configuration of the first guide member in Embodiment 1. 
         FIG. 10  is a partially enlarged view of a heat exchanger according to Embodiment 2. 
         FIG. 11  is a partially enlarged view showing a relationship in which a heat transfer tube and a first guide member are connected to a fin in the heat exchanger according to Embodiment 2. 
         FIG. 12  is a partially enlarged view of a heat exchanger according to Embodiment 3. 
         FIG. 13  is a partially enlarged view showing a relationship in which a heat transfer tube and a first guide member are connected to a fin in the heat exchanger according to Embodiment 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings, in which the same or corresponding parts will be designated by the same reference numerals, and a description thereof will not be repeated. 
     Embodiment 1 
     &lt;Air Conditioner&gt; 
     An air conditioner  100  according to Embodiment 1 will be described first with reference to  FIG. 1 . Air conditioner  100  includes a compressor  1 , a four-way valve  2 , an indoor heat exchanger  3 , an expansion valve  4 , an outdoor heat exchanger  5 , an indoor fan  6 , and an outdoor fan  7 . Compressor  1 , four-way valve  2 , indoor heat exchanger  3 , expansion valve  4 , and outdoor heat exchanger  5  constitute a refrigerant circuit in which refrigerant circulates. 
     Compressor  1  has an inlet side and an outlet side which are connected to four-way valve  2 . Four-way valve  2  is provided in the refrigerant circuit so as to switch a refrigerant flow direction. Air conditioner  100  is provided so as to perform heating operation, cooling operation, and defrosting operation by switching the refrigerant flow direction by four-way valve  2 . In  FIG. 1 , a solid line and an arrow F 1  indicate a refrigerant flow path during heating operation, and a broken line and an arrow F 2  indicate a refrigerant flow path during cooling operation and defrosting operation. Four-way valve  2  is provided so as to cause the refrigerant (high temperature and high pressure) discharged from compressor  1  to flow out to indoor heat exchanger  3  during heating operation. Four-way valve  2  is provided so as to cause the high-temperature, high-pressure refrigerant discharged from compressor  1  to flow out to outdoor heat exchanger  5  during cooling operation and defrosting operation. Expansion valve  4  expands the refrigerant flowing from indoor heat exchanger  3  to outdoor heat exchanger  5  during heating operation. Expansion valve  4  expands the refrigerant flowing from outdoor heat exchanger  5  to indoor heat exchanger  3  during cooling operation and defrosting operation. Indoor heat exchanger  3  acts as a condenser during heating operation and as an evaporator during cooling operation and defrosting operation. Outdoor heat exchanger  5  acts as an evaporator during heating operation and as a condenser during cooling operation and defrosting operation. Indoor fan  6  is provided so as to blow air to indoor heat exchanger  3 . Outdoor fan  7  is provided so as to blow air to outdoor heat exchanger  5  in a second direction B, which will be described below. 
     &lt;Outdoor Heat Exchanger&gt; 
     Outdoor heat exchanger  5  will now be described with reference to  FIGS. 1 to 4 . Outdoor heat exchanger  5  performs heat exchange between refrigerant and gas. With reference to  FIGS. 2 and 3 , outdoor heat exchanger  5  mainly includes a heat transfer tube  20 , a heat transfer tube  21 , a first guide member  22 , a second guide member  23 , and a fin  24  (including first and second fin portions  24 ). 
     As shown in  FIGS. 2 and 3 , heat transfer tubes  20  and  21  are, for example, flat heat transfer tubes. Heat transfer tubes  20  and  21  are provided to extend in a first direction A. The refrigerant flows in heat transfer tubes  20  and  21  in first direction A. First direction A may be any direction crossing the horizontal direction, which is the vertical direction, for example. 
     Heat transfer tube  20  and heat transfer tube  21  are spaced apart from each other in second direction B. Second direction B is a direction crossing first direction A and extends in the flow direction of the gas blown to outdoor heat exchanger  5  by outdoor fan  7 . Second direction B is, for example, the horizontal direction. Heat transfer tube  20  is disposed windward of heat transfer tube  21  in second direction B. Heat transfer tubes  20  and  21  are connected to first and second fin portions  24  in a third direction C. Third direction C is a direction crossing first direction A and second direction B. Third direction C is, for example, the horizontal direction and is a direction orthogonal to second direction B. 
     A plurality of through-holes  26  extending in first direction A are provided in heat transfer tube  20 . Through-holes  26  include, for example, six through-holes  26   a ,  26   b ,  26   c ,  26   d ,  26   e , and  26   f . A plurality of through-holes  27  extending in first direction A are provided in heat transfer tube  21 . Through-holes  27  include, for example, six through-holes  27   a ,  27   b ,  27   c ,  27   d ,  27   e , and  27   f . The cross-sections of through-holes  26  and  27  orthogonal to first direction A may have any shape, which is a rectangular shape, for example. Through-holes  26  are connected to a first distributor  10 , which will be described below. This allows the refrigerant to flow in through-holes  26  of heat transfer tube  20 . Through-holes  27  are connected to a second distributor  11 , which will be described below. This allows the refrigerant to flow in through-holes  27  of heat transfer tube  21 . 
     First guide member  22  and second guide member  23  are provided to extend in first direction A. The refrigerant flowing in the refrigerant circuit of air conditioner  100  does not flow in first guide member  22  and second guide member  23 . That is to say, first guide member  22  and second guide member  23  do not constitute the refrigerant circuit of air conditioner  100 . First guide member  22  and second guide member  23  are so-called solid members in which no through-holes are provided, unlike heat transfer tubes  20  and  21 . Through-holes extending in first direction A may be provided inside first guide member  22  and second guide member  23 . It suffices that in this case, the through-holes provided in first guide member  22  and second guide member  23  are not connected to the refrigerant circuit of air conditioner  100 . 
     The material for first guide member  22  and second guide member  23  is, for example, copper (Cu) or aluminum (Al). The material for first guide member  22  and second guide member  23  may be identical to or different from the material for heat transfer tubes  20  and  21 . The material for first guide member  22  and second guide member  23  may be, for example, resin such as hard resins such as polypropylene and a composite material including polypropylene. 
     First guide member  22  and second guide member  23  are spaced apart from each other in second direction B. First guide member  22  is disposed windward of second guide member  23  in second direction B. First guide member  22  and second guide member  23  are connected to first and second fin portions  24  in third direction C. It suffices that first guide member  22  and second guide member  23  are connected to first and second fin portions  24  by any method, which are fixed to first and second fin portions  24  by, for example, brazing. 
     First guide member  22  is disposed between and connected to a first region  24 F of first fin portion  24 , which will be described below, and a second region  24 G of second fin portion  24 , which will be described below. First guide member  22  has a first surface that is not connected to first and second fin portions  24 . Second guide member  23  has a second surface that is not connected to first and second fin portions  24 . The first surface and the second surface are provided to extend in first direction A. The lower edges of the first surface and the second surface in first direction A are provided so as to efficiently drain the water that has passed through on the first surface and the second surface to reach the lower edges. The lower edges of the first surface and the second surface are connected to, for example, a drain member (not shown) that can drain water out of outdoor heat exchanger  5 . The lower edges of the first surface and the second surface may be spaced apart from, for example, the drain member such as a drain pan above this drain member. 
     With reference to  FIGS. 3, 5 ( a ), and  8 ( a ), the cross-sections of first guide member  22  and second guide member  23  which are perpendicular to first direction A have, for example, an approximately oval shape. First guide member  22  and second guide member  23  are disposed such that, for example, the long axes thereof extend in second direction B. 
     Among heat transfer tubes  20  and  21 , first guide member  22 , and second guide member  23 , first guide member  22  is disposed most windward in second direction B. First guide member  22 , heat transfer tube  20 , second guide member  23 , and heat transfer tube  21  are disposed in order from windward to leeward in second direction B. First guide member  22  and heat transfer tube  20  are spaced apart from each other in the second direction. Heat transfer tube  20  and second guide member  23  are spaced apart from each other in the second direction. Second guide member  23  and heat transfer tube  21  are spaced apart from each other in the second direction. 
     First guide member  22  has a first end  22 A located windward and a second end  229  located leeward. The surfaces of first end  22 A and second end  22 B are provided to extend in first direction A and are not connected to first and second fin portions  24 . The first surface is formed of the surfaces of first end  22 A and second end  22 B. Heat transfer tube  20  has a third end  20 A located windward and a fourth end  20 B located leeward. Second guide member  23  has a fifth end  23 A located windward and a sixth end  23 B located leeward. The surfaces of fifth end  23 A and sixth end  23 B are provided to extend in first direction A and are not connected to first and second fin portions  24 . The second surface is formed of the surfaces of fifth end  23 A and sixth end  23 B. Heat transfer tube  21  has a seventh end  21 A located windward and an eighth end  21 B located leeward. First and second fin portions  24  have a ninth end  24 A located windward and a tenth end  24 B located leeward. 
     A first space  30  is provided between second end  22 B of first guide member  22  which is located leeward and third end  20 A of heat transfer tube  20  which is located windward. That is to say, first space  30  faces a part of the first surface of first guide member  22 . A second space  31  is provided between fourth end  209  of heat transfer tube  20  which is located leeward and fifth end  23 A of second guide member  23  which is located windward. That is to say, second space  31  faces a part of the second surface of second guide member  23 . A third space  32  is provided between sixth end  23 B of second guide member  23  which is located leeward and seventh end  21 A of heat transfer tube  21  which is located windward. That is to say, third space  32  faces a part of the second surface of second guide member  23 . Spaces  30 ,  31 , and  32  face lateral ends  24 E of first and second fin portions  24  in third direction C. 
     First end  22 A of first guide member  22  is provided to be continuous with, for example, ninth ends  24 A of first and second fin portions  24  in third direction C. Eighth end  21 B of heat transfer tube  21  is provided to be continuous with, for example, tenth ends  24 B of first and second fin portions  24  in third direction C. 
     Heat transfer tubes  20  and  21 , first guide member  22 , and second guide member  23  have the same width in, for example, third direction C. The widths of first guide member  22  and second guide member  23  in second direction B are smaller than, for example, the widths of heat transfer tubes  20  and  21  in second direction B. In other words, an area S 1  of the cross-section of first guide member  22  which is perpendicular to first direction A and an area S 2  of the cross-section of second guide member  23  which is perpendicular to first direction A are smaller than areas S 3  and S 4  of the cross-sections of heat transfer tubes  20  and  21  perpendicular to first direction A. Areas S 3  and S 4  also include the areas inside through-holes  26  and  27 . The width of first guide member  22  in second direction B is smaller than the distance between third end  20 A of heat transfer tube  20  and each of ninth ends  24 A of first and second fin portions  24  in second direction B. Although the distance between third end  20 A of heat transfer tube  20  and each of ninth ends  24 A of first and second tin portions  24  in second direction B may have any value as long as the frost on ninth end  24 A can be melted by the heat of the refrigerant flowing in through-hole  26  of heat transfer tube  20  during defrosting operation, this distance preferably has the smallest possible value. 
     Fin  24  includes first fin portion  24  and second fin portion  24  disposed with heat transfer tubes  20  and  21  therebetween in third direction C. First and second fin portions  24  are configured separately. First and second fin portions  24  have, for example, a similar configuration. First and second fin portions  24  are separated from each other in third direction C. First and second fin portions  24  are formed as corrugated fins formed of, for example, a thin film made of metal or the like shaped in a wave form. First fin portion  24  has first region  24 F located windward of heat transfer tube  20  located most windward in second direction B. Second fin portion  24  has second region  24 G located windward of heat transfer tube  20  located most windward in second direction B. First region  24 F and second region  24 G are spaced apart from each other in third direction C. As described above, first guide member  22  is connected to first region  24 F and second region  24 G. 
     First and second fin portions  24  are provided with, for example, a plurality of louvers  25 . Louvers  25  are provided to extend in third direction C and are spaced apart from each other in second direction B. Some of louvers  25  are provided in a portion of fin  24  which is located between adjacent first guide members  22  in third direction C, a portion of fin  24  which is located between adjacent second guide members  23  in third direction C, and a portion of fin  24  which is located between adjacent heat transfer tubes  20  and  21  in third direction C. 
     With reference to  FIGS. 3 and 4 , louvers  25  are provided such that louvers  25  located on the ninth end  24 A side with respect to second guide member  23  and louvers  25  located on the tenth end  24 B side with respect to second guide member  23  have line symmetry. 
     For example, a plurality of heat transfer tubes  20 , a plurality of heat transfer tubes  21 , a plurality of first guide members  22 , and a plurality of second guide members  23  are provided. Heat transfer tubes  20  are spaced apart from each other in third direction C. Heat transfer tubes  21  are spaced apart from each other with first or second fin portion  24  therebetween in third direction C. First guide members  22  are spaced apart from each other with first or second fin portion  24  therebetween in third direction C. Second guide members  23  are spaced apart from each other with first or second fin portion  24  therebetween in third direction C. Fin  24  may further include a plurality of fin portions spaced apart from each other in third direction C, in addition to the first and second fin portions. The fin portions are spaced apart from each other with one heat transfer tube  20 , one heat transfer tube  21 , one first guide member  22 , and one second guide member  23  therebetween in third direction C. In this case, a plurality of spaces  30 , a plurality of spaces  31 , and a plurality of spaces  32  are provided in third direction C. 
     It suffices that outdoor heat exchanger  5  has any configuration as long as it has the above configuration. For example, outdoor heat exchanger  5  further includes first distributor  10 , second distributor  11 , and a folded header  12  as shown in  FIG. 2 . 
     The respective lower ends of heat transfer tubes  20  in first direction A are connected to first distributor  10 . First distributor  10  is provided so as to distribute the refrigerant to heat transfer tubes  20 . The respective lower ends of heat transfer tubes  21  in first direction A are connected to second distributor  11 . Second distributor  11  is connected to the respective lower ends of heat transfer tubes  21  in first direction A. Second distributor  11  is provided so as to distribute the refrigerant to heat transfer tubes  21 . First distributor  10  is disposed windward of second distributor  11 . First distributor  10  is connected to expansion valve  4  through, for example, a refrigerant pipe. Second distributor  11  is connected to four-way valve  2  through, for example, a refrigerant pipe. Folded header  12  is connected to the respective upper ends of heat transfer tube  20  and heat transfer tube  21  in first direction A. 
     The respective lower ends and the respective upper ends of first guide members  22  in first direction A are not connected to, for example, all of first distributor  10 , second distributor  11 , and folded header  12 . The respective lower ends and the respective upper ends of second guide members  23  in first direction A are not connected to, for example, all of first distributor  10 , second distributor  11 , and folded header  12 . The lower edge of the first surface may be provided to be in contact with the outer surface of first distributor  10 , which will be described below. The lower edge of the second surface may be provided to be in contact with the outer surface of second distributor  11 , which will be described below. 
     &lt;Operation of Refrigeration Cycle Apparatus&gt; 
     The operations of air conditioner  100  and outdoor heat exchanger  5  will now be described with reference to  FIG. 1 . Air conditioner  100  forms a refrigerant flow path indicated by the solid line and arrow F 1  in  FIG. 1  during heating operation. The refrigerant in a gas-liquid two-phase state, which has been condensed by indoor heat exchanger  3  and expanded by expansion valve  4 , is supplied to first distributor  10  of outdoor heat exchanger  5 . Outdoor heat exchanger  5  is provided with a refrigerant flow path from first distributor  10  through heat transfer tube  20 , folded header  12 , and heat transfer tube  21  to second distributor  11 . 
     With reference to  FIGS. 5( a ) and ( b ) , during heating operation, a partial region of fin  24  located leeward of third end  20 A of heat transfer tube  20  is cooled by refrigerant flowing in through-hole  26  of heat transfer tube  20  to a temperature approximately equal to the temperature of the refrigerant. The surface temperature of fin  24  thus exhibits a uniform temperature distribution on the partial region. 
     In contrast, the other region of fin  24  which is sandwiched between first guide members  22  adjacent to each other in third direction C and is located windward of the partial region, that is, the region of fin  24  located (projecting) windward of heat transfer tube  20  is distant from heat transfer tube  20  through which the refrigerant flows, compared with the partial region. The surface temperature of fin  24  thus exhibits a temperature distribution according to the distance from heat transfer tube  20  in the other region. That is to say, the surface temperature of fin  24  exhibits a temperature distribution in which temperature is highest at ninth end  24 A of fin  24  which is located most distant from third end  20 A of heat transfer tube  20  and gradually decreases as closer to the position at which the surface overlaps third end  20 A of heat transfer tube  20  in third direction C. 
     With reference to  FIG. 5( b ) , during heating operation, the temperature of the air flowing on the surface of fin  24  exhibiting the above temperature distribution exhibits a temperature distribution in which the temperature is higher than the surface temperature of fin  24  and gradually decreases from the ninth end  24 A side (windward side) of fin  24  to the tenth end  24 B side (leeward side) of fin  24 . The vertical axis of  FIG. 5( b )  represents a temperature of the surface of fin  24  or air flowing on the surface, and the horizontal axis of  FIG. 5( b )  represents a position on the surface of fin  24  (a distance from ninth end  24 A of fin  24  in second direction B). The vertical axis of  FIG. 5( c )  represents an amount of heat exchange between refrigerant and air through fin  24 , and the horizontal axis of  FIG. 5( c )  represents a position on the surface of fin  24  (a distance from ninth end  24 A of fin  24  in second direction B). 
     The surface temperature of fin  24  and the temperature of the air flowing on the surface of fin  24  exhibit the temperature distributions as shown in  FIG. 5( b ) , and accordingly, the amount of heat exchange between the refrigerant and the outdoor air through fin  24  exhibits an almost uniform distribution from ninth end  24 A to tenth end  24 B of firm  24 , as shown in  FIG. 5( c ) . As shown in  FIG. 4 , thus, the frost formation amount on fin  24  can be made almost uniform from ninth end  24 A of fin  24  to tenth end  24 B of fin  24  during heating operation. 
     Air conditioner  100  forms a refrigerant flow path indicated by the broken line and arrow F 2  shown in  FIG. 1  during cooling operation and defrosting operation. The high-temperature, high-pressure refrigerant in a gas single-phase state, which has been evaporated by indoor heat exchanger  3  and compressed by compressor  1 , is supplied to second distributor  11  of outdoor heat exchanger  5 . Outdoor heat exchanger  5  is provided with a refrigerant flow path from second distributor  11  through heat transfer tube  21 , folded header  12 , and heat transfer tube  20  to first distributor  10 . Since a frost formation amount on the fin  24  during heating operation is made uniform in second direction B during defrosting operation, the frost on fin  24  is melted efficiently irrespective of its position in second direction B. 
     With reference to  FIGS. 3, 6, and 7 , the frost melted during defrosting operation described above turns into water W and is drained, and is subsequently removed from outdoor heat exchanger  5 . Outdoor heat exchanger  5  has three drain flow paths for the frost that has been removed. A first drain flow path is a drain flow path passing through the surface of fin  24  and louver  25  and running from above to below vertically. A second drain flow path is a drain flow path passing through third end  20 A and fourth end  20 B of heat transfer tube  20  and seventh end  21 A and eighth end  21 B of heat transfer tube  21  and running from above to below vertically. A third drain flow path is a drain flow path passing through first end  22 A and second end  22 B of first guide member  22  and fifth end  23 A and sixth end  23 B of second guide member  23  and running from above to below vertically. 
     Outdoor heat exchanger  5  thus has a drainage efficiency higher than that of an outdoor heat exchanger having no first guide member  22 , that is, an outdoor heat exchanger having no third drain flow path passing through first guide member  22  and having only the first drain flow path and the second drain flow path. In particular, outdoor heat exchanger  5  has a high drain efficiently in a region of fin  24  which is located windward of heat transfer tube  20 . This allows outdoor heat exchanger  5  to reduce a time for defrosting operation more than the above outdoor heat exchanger. In addition, outdoor heat exchanger  5  prevents water from staying on fin  24  and also prevents the water which has stayed on fin  24  even after defrosting operation from forming frost again during heating operation, and accordingly has high heat exchange efficiency during heating operation. 
     &lt;Function and Effect&gt; 
     Outdoor heat exchanger  5  according to Embodiment 1 includes heat transfer tubes  20  and  21 , first guide member  22 , and fin  24 . Heat transfer tube  20  is provided to extend in first direction A, in which refrigerant flows. Fin  24  is connected to heat transfer tubes  20  and  21 . Fin  24  has first region  24 F and second region  24 G located windward of heat transfer tube  20  in second direction B. First region  22 F and second region  24 G are spaced apart from each other in third direction C. First guide member  22  is disposed between first region  24 F and second region  24 G in third direction C. Of heat transfer tubes  20  and  21 , first guide member  22  is disposed most windward. First guide member  22  has first end  22 A and second end  22 B as a first surface which extends in first direction A and is not connected to fin  24 . Refrigerant does not flow in first guide member  22 . 
     In outdoor heat exchanger  5 , fin  24  has first region  24 F and second region  24 G located windward of heat transfer tube  20  in second direction B. This allows outdoor heat exchanger  5  to prevent or reduce frost formation on first region  24 F and second region  24 G of fin  24  during heating operation in which outdoor heat exchanger  5  acts as an evaporator, thus making the frost formation amount on fin  24  uniform in third direction C. Thus, outdoor heat exchanger  5  can efficiently melt the frost on fin  24  during defrosting operation. In addition, outdoor heat exchanger  5  includes first guide member  22  connected to first region  24 F and second region  24 G of fin  24 , and thus can efficiently drain the water, generated on first region  24 F and second region  24 G during defrosting operation, downward in first direction A through first end  22 A and second end  22 B of first guide member  22 . That is to say, outdoor heat exchanger  5  prevents or reduces frost formation on fin  24  and has high defrosting efficiency. 
     In outdoor heat exchanger  5 , the first surface of first guide member  22  has a surface of second end  22 B of first guide member  22  which is located leeward in second direction B. This allows outdoor heat exchanger  5  to have a drainage efficiency higher than that of an outdoor heat exchanger in which the first surface has only the surface of first end  22 A of first guide member  22  which is located windward. 
     In outdoor heat exchanger  5 , fin  24  includes first fin portion  24  and second fin portion  24  disposed with heat transfer tubes  20  and  21  therebetween in third direction C. First region  24 F is formed on first fin portion  24 , and second region  24 G is formed on second tin portion  24 . This allows outdoor heat exchanger  5  to efficiently drain the water, generated on first region  24 F and second region  24 G of the corrugated fin during defrosting operation, downward in first direction A through first end  22 A and second end  22 B of first guide member  22  even when, for example, first and second fin portions  24  are formed of corrugated fins or the like. 
     Outdoor heat exchanger  5  includes heat transfer tubes  20  and  21  spaced apart from each other in second direction B, and at least one second guide member  23  provided to extend in first direction A and spaced apart from two heat transfer tubes  20  and  21  adjacent to each other in second direction B among heat transfer tubes  20  and  21  between the two adjacent heat transfer tubes  20  and  21 . Second guide member  23  has a second surface which extends in first direction A and is not connected to fin  24 . Alternatively, three or more heat transfer tubes may be spaced apart from each other in second direction B. In this case, a second guide member is preferably disposed between two heat transfer tubes adjacent to each other in second direction B. Consequently, the region of fin  24  which is located between the two heat transfer tubes adjacent to each other in second direction B and is not connected to heat transfer tubes is connected with second guide member  23  having the second surface. Outdoor heat exchanger  5  including second guide member  23  can thus increase the efficiency of draining water from the relevant region on fin  24 . 
     Air conditioner  100  according to Embodiment 1 includes outdoor heat exchanger  5  as described above, outdoor fan  7  that blows gas to outdoor heat exchanger  5  in second direction B, and four-way valve  2  capable of switching the flow direction of the refrigerant flowing through heat transfer tubes  20  and  21  of outdoor heat exchanger  5 . Air conditioner  100  can thus have high efficiency during heating operation and defrosting operation. 
     First guide member  22  and second guide member  23  may have any configuration as long as they have the first surface and the second surface.  FIGS. 8( b ) to ( i )  show the examples of the sectional shapes of first guide member  22  and second guide member  23  perpendicular to first direction A, other than the example of  FIG. 8( a ) . 
     As shown in  FIGS. 8( b ) to ( e ), ( g ), and ( h ) , first guide member  22  may have a sectional shape in which an indentation  40 ,  41 ,  42  is provided between first end  22 A and second end  22 B in the longitudinal direction of first guide member  22  shown in  FIG. 8( a ) . Indentation  40 ,  41 ,  42  is provided to extend in first direction A (see  FIGS. 2 and 3 ). In first guide member  22  described above, the inner circumferential surface of indentation  40 ,  41 ,  42  can also be a surface which is provided to extend in first direction A and is not connected to fin  24 . First guide members  22  shown in  FIGS. 8( b ) to ( e ), ( g ), and ( h )  accordingly have a large surface area of the first surface of first guide member  22  and a high efficiency of draining the water through the first surface, compared with first guide member  22  shown in  FIG. 8( a ) . 
     As shown in  FIGS. 8( b ) and ( e ) , first guide member  22  may be provided with indentation  40  only on one outer surface side extending in its longitudinal direction. As shown in  FIGS. 8( c ) and ( d ) , first guide member  22  may be provided with indentation  41  on one outer surface side extending its longitudinal direction as well as indentation  42  on the other outer surface side. As shown in  FIGS. 8( g ) and ( h ) , at least one of indentation  41  and indentation  42  may be plural. The cross-sections of indentation  40 ,  41 ,  42  may have any shape, which may be, for example, a rectangular shape or triangular shape. Indentation  41  and indentation  42  may be provided to have line symmetry with the center line of first guide member  22  extending longitudinally therebetween as shown in  FIG. 8( c ) , or may be provided to have point symmetry about the center of the cross-section of first guide member  22  as shown in  FIG. 8( d ) . 
     As shown in  FIGS. 8( f ) and ( i ) , the cross-section of first guide member  22  perpendicular to first direction A may be provided such that the portion thereof located leeward of first end  22 A, that is, the portion thereof located at the side closer to second end  22 B with respect to first end  22 A has a great width in third direction C compared with first end  22 A located windward. First guide member  22  as described above can lessen the colliding resistance of a gas generated by the collision of the gas blown from outdoor fan  7  to outdoor heat exchanger  5  with first guide member  22 . First end  22 A is provided, for example, linearly to extend in first direction A. As shown in  FIG. 8( f ) , second end  22 B may be provided to have the greatest width in first guide member  22 . As shown in  FIG. 8( i ) , second end  22 B is also provided linearly to extend in first direction A similarly to first end  22 A, and portions wider than first end  22 A and second end  22 B may be provided at the portions located between first end  22 A and second end  22 B. Alternatively, as shown in  FIG. 8( i ) , first guide member  22  may be provided to be in line contact with lateral end  24 E of fin  24  (see  FIG. 3 ). In first guide member  22  shown in  FIG. 8( i ) , the entire surface of the portion other than the widest portion in third direction C (see  FIG. 3 ) can form the first surface which extends in first direction A and is not connected to fin  24 . 
     Although the example configurations of first guide member  22  have been described with reference to  FIGS. 8( h ) to ( i ) , second guide member  23  can have a similar configuration. 
     With reference to  FIG. 8( j ) , first guide member  22  and second guide member  23  may be formed of a base material  43  and a coating film  44  covering base material  43 . In this case, the material for coating film  44  is, for example, a resin such as amide compound, vinyl alcohol, epoxy resin, or acrylic resin which is typically highly hydrophilic, and is preferably more hydrophilic than the material for the surface of fin  24 . In contrast, the material for base material  43  may be any appropriate material. Herein, the state in which an angle of contact between water and the surface of first guide member  22  is 0° or more and less than 90° is referred to as a highly hydrophilic state. 
     First guide member  22  and second guide member  23  may be provided such that their lengths in the cross-sections of the first surface and the second surface which are perpendicular to first direction A increase toward downward in first direction A. Such a configuration widens the first surface of first guide member  22  and the second surface of second guide member  23  toward downward in first direction A. Since the water melted from the portion of fin  24  located above lower portions of the first surface and the second surface flows in the lower portions, the flow rate of the water flowing on the first surface and the second surface increases toward downward. The drain efficiency owing to the first surface and the second surface can be increased further when the first surface of first guide member  22  and the second surface of second guide member  23  are wider toward downward in first direction A. 
     It suffices that first guide member  22  and second guide member  23  are adjacent to fin  24  in outdoor heat exchanger  5 . Herein, the state in which first guide member  22  and second guide member  23  are adjacent to fin  24  refers to the state in which first guide member  22  and second guide member  23  are connected to fin  24  as described above or the state in which first guide member  22  and second guide member  23  are spaced apart from fin  24  at a minute interval therebetween and are not connected to fin  24 . First guide member  22  and second guide member  23  may be spaced apart from lateral end  24 E of fin  24  in third direction C at such an interval as to allow the water on lateral end  24 E to contact first guide member  22  and second guide member  23 . In this case, first guide member  22  and second guide member  23  may be positioned with respect to the component other than fin  24  in outdoor heat exchanger  5 . Also with such a configuration, the water that has reached lateral end  24 E in fin  24  is efficiently drained by first guide member  22  and second guide member  23 . An outdoor heat exchanger including such first guide member  22  can achieve effects similar to those of outdoor heat exchanger  5  according to Embodiment 1. In this case, as shown in  FIG. 9( a ) , the first surface has a surface of lateral end  22 E of first guide member  22  in third direction C. The second surface has a surface of lateral end  23 E of second guide member  23  in third direction C. Alternatively, as shown in  FIG. 9( b ) , first guide member  22  may be provided such that the area of a cross-section perpendicular to first direction A increases toward downward in first direction A. In this case, the width of first guide member  22  in third direction C may be provided to be uniform in first direction A, and the width of first guide member  22  in second direction B may be provided to increase toward downward in first direction A. Similarly, second guide member  23  may be provided such that the area of a cross-section perpendicular to first direction A increases toward downward in first direction A. Also with such a configuration, the first surface of first guide member  22  and the second surface of second guide member  23  can be widened toward downward in first direction A, which increases the drainage efficiency by the first surface and the second surface. 
     First guide member  22  and second guide member  23  may be fixed by press Fitting to outdoor heat exchanger  5  to which heat transfer tubes  20  and  21  and fin  24  are fixed by brazing. 
     Embodiment 2 
     A heat exchanger according to Embodiment 2 will now be described with reference to  FIGS. 10 and 11 . The heat exchanger according to Embodiment 2 basically has a configuration similar to that of the heat exchanger according to Embodiment 1 but differs therefrom in that fin  24  is provided with a first cut-away portion  51  capable of receiving first guide member  22  and that the first surface of first guide member  22  is disposed in first cut-away portion  51 . 
     Fin  24  is, for example, a flat fin. A plurality of fins  24  are layered in first direction A. Fins  24  have, for example, the same configuration. First cut-away portion  51  is provided in each of fins  24  layered in first direction A. First cut-away portions  51  have, for example, the same configuration. First cut-away portions  51  are provided to overlap one another in, for example, first direction A. 
     First cut-away portion  51  faces ninth end  24 A of fin  24  and is provided to extend in second direction B. It suffices that first cut-away portion  51  has any configuration as long as it can receive first guide member  22 . The width of first cut-away portion  51  in second direction B is equal to, for example, the width of first guide member  22  in second direction B. The width of first cut-away portion  51  in third direction C is equal to, for example, the width of first guide member  22  in third direction C. In this case, first region  24 F and second region  24 G located windward of heat transfer tube  20  in second direction B are disposed with first cut-away portion  51  therebetween in third direction C. 
     Second end  22 B of first guide member  22  is fitted with, for example, the end of first cut-away portion  51  which is located leeward without any gap. First end  22 A of first guide member  22  is provided to be continuous with, for example, ninth end  24 A of fin  24 . First end  22 A may project windward of, for example, ninth end  24 A. First guide member  22  is provided with indentation  40  as shown in, for example,  FIG. 8( b ) . In this case, the inner circumferential surface of indentation  40  of first guide member  22  is provided to extend in first direction A and is not connected to fin  24 . In outdoor heat exchanger  5  according to Embodiment 2, thus, the first surface has the surface of first end  22 A and the inner circumferential surface of indentation  40 . 
     Each of fins  24  may be provided with a third cut-away portion  53  capable of receiving heat transfer tube  20 . Third cut-away portion  53  faces tenth end  24 B of fin  24  and is provided to extend in second direction B. It suffices that third cut-away portion  53  has any configuration as long as it can receive heat transfer tube  20 . The width of third cut-away portion  53  in second direction B is equal to, for example, the width of heat transfer tube  20  in second direction B. The width of third cut-away portion  53  in third direction C is equal to, for example, the width of heat transfer tube  20  in third direction C. 
     Third end  20 A of heat transfer tube  20  is fitted with, for example, the end of third cut-away portion  53  which is located windward without any gap. Fourth end  20 B of heat transfer tube  20  is provided to be continuous with, for example, tenth end  24 B of fin  24 . Fourth end  20 B may project leeward of, for example, tenth end  24 B. 
     First cut-away portion  51  and third cut-away portion  53  are spaced apart from each other in second direction  13 . The end of first cut-away portion  51  which is located leeward is located windward of the end of third cut-away portion  53  which is located windward. From a different perspective, fin  24  includes first fin portion  24  and second fin portion  24  formed with first cut-away portion  51  and third cut-away portion  53  therebetween in third direction C. First and second tin portions  24  are configured integrally. That is to say, fin  24  has a portion located between first cut-away portion  51  and third cut-away portion  53  in second direction B, and first fin portion  24  and second fin portion  24  are connected to each other with this portion therebetween. First guide member  22  is disposed between first region  24 F formed on first fin portion  24  and second region  24 G formed on second fin portion  24 . 
     First guide member  22  and fin  24  can be positioned with respect to each other by, for example, first guide member  22  inserted into first cut-away portion  51 . Heat transfer tube  20  and fin  24  can be positioned with respect to each other by, for example, heat transfer tube  20  inserted into third cut-away portion  53 . 
     Also with such a configuration, fin  24  has first region  24 F and second region  24 G located windward of heat transfer tube  20  in second direction B, and the frost formation on first region  24 F and second region  24 G of fin  24  can accordingly be prevented or reduced during heating operation in which outdoor heat exchanger  5  serves as an evaporator, resulting in uniform frost formation amount on fin  24  in third direction C. This allows outdoor heat exchanger  5  to efficiently melt the frost on fin  24  during defrosting operation. Further, since outdoor heat exchanger  5  includes first guide member  22  connected to first region  24 F and second region  24 G of fin  24 , the water generated on first region  24 F and second region  24 G during defrosting operation can be efficiently drained downward in first direction A through first end  22 A of first guide member  22  and indentation  40 . That is to say, outdoor heat exchanger  5  according to Embodiment 2 can achieve effects similar to those of outdoor heat exchanger  5  according to Embodiment 1. 
     It suffices that at least a part of the portion of first guide member  22  which is received in first cut-away portion  51  is configured appropriately as long as an interval can be formed between first cut-away portion  51  and first guide member  22 . First guide member  22  may have, for example, any of the configurations shown in  FIGS. 8( c )  to ( i ). 
     Embodiment 3 
     An outdoor heat exchanger according to Embodiment 3 will now be described with reference to  FIGS. 12 and 13 . The outdoor heat exchanger according to Embodiment 3 basically has a configuration similar to that of outdoor heat exchanger  5  according to Embodiment 2 but differs therefrom in that fin  24  is provided with a second cut-away portion  52  connected to first cut-away portion  51 . 
     Second cut-away portion  52  is provided in each of fins  24  layered in first direction A. Second cut-away portions  52  have, for example, the same configuration. Second cut-away portions  52  are provided to overlap one another in, for example, first direction A. 
     Second cut-away portion  52  is provided leeward of, for example, first cut-away portion  51 . The end of second cut-away portion  52  which is located windward is connected to the end of first cut-away portion  51  which is located leeward. Second cut-away portion  52  is not provided so as to receive first guide member  22 . The width of the end of second cut-away portion  52  which is located windward in third direction C is smaller than the width of first guide member  22  in third direction C. 
     The surface of a part of second end  22 B of first guide member  22  inserted into first cut-away portion  51  faces second cut-away portion  52  of fin  24 . The surface of the part of first guide member  22  which faces second cut-away portion  52  is provided to extend in first direction A and is not connected to fin  24 . That is to say, the first surface of first guide member  22  has the surface of first end  22 A and the surface of the part of first guide member  22 . 
     The outdoor heat exchanger according to Embodiment 3 can thus achieve effects similar to those of the outdoor heat exchanger according to Embodiment 2. 
     Although second cut-away portion  52  is preferably connected to first cut-away portion  51  leeward of first cut-away portion  51 , it may be connected to any location of first cut-away portion  51 . 
     The outdoor heat exchangers according to Embodiment 2 and Embodiment 3 may further include a heat transfer tube leeward of heat transfer tube  20 . For example, a heat transfer tube and a fin that have configurations similar to those of heat transfer tube  20  and tin  24  shown in  FIGS. 10 to 13  may be disposed leeward of heat transfer tube  20  and fin  24 . Also with such a configuration, the effects similar to those of the outdoor heat exchangers according to Embodiment 2 and Embodiment 3 can be achieved. 
     Although the heat exchangers (outdoor heat exchangers) according to Embodiments 1 to 3 are suitable for air conditioners as described above, the present invention is not limited thereto. The heat exchanges according to Embodiments 1 to 3 are applicable to, for example, apparatuses that employ a heat pump that compresses refrigerant by a compressor and circulates the compressed refrigerant, such as a heat pump water heater or a refrigerator. 
     It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. It is therefore intended that the scope of the present invention is defined by claims, not only by the embodiments described above, and encompasses all modifications and variations equivalent in meaning and scope to the claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention is particularly advantageously applied to an air conditioner which is subjected to heating operation in cold weather and a heat exchanger included in the air conditioner. 
     REFERENCE SIGNS LIST 
       1  compressor,  2  four-way valve,  3  indoor heat exchanger,  4  expansion valve,  5  outdoor heat exchanger,  6  indoor fan,  7  outdoor fan,  10  first distributor,  11  second distributor,  12  folded header,  20 ,  21  heat transfer tube,  20 A third end,  20 B fourth end,  21 A seventh end,  21 B eighth end,  22  first guide member,  22 A first end,  22 B second end,  23  second guide member,  23 A fifth end,  23 B sixth end,  24  fin,  24 A ninth end,  24 B tenth end,  25  louver,  40 ,  41 ,  42  indentation,  43  base material,  44  coating film,  51  first cut-away portion,  52  second cut-away portion,  53  third cut-away portion.