Heat exchanger

Abstract

In a heat exchanger, each of flat tubes ( 31 ) has an end portion inserted in a header-collecting pipe ( 70 ). When the heat exchanger functions as an evaporator, a refrigerant in a gas-liquid two-phase state upwardly flows in a subspace ( 71 a ) located in the header-collecting pipe ( 70 ). An effective cross-sectional area A of the subspace ( 71 a ) in the header-collecting pipe ( 70 ) is set based on a mass flow rate of the refrigerant flowing into the subspace ( 71 a ) in the header-collecting pipe ( 70 ). The effective cross-sectional area A is obtained by subtracting a projected area A 1 which corresponds to a portion of each flat tube ( 31 ) located in the subspace ( 71 a ) and is projected onto a plane perpendicular to an axial direction of the header-collecting pipe ( 70 ) from an area A 0 of a cross section of the subspace ( 71 a ) which is perpendicular to the axial direction of the header-collecting pipe ( 70 ).

1 . A heat exchanger comprising:
 a plurality of flat tubes; a first header-collecting pipe having inserted therein an end portion of each of the flat tubes; a second header-collecting pipe having inserted therein the other end portion of each of the flat tubes; and a plurality of fins joined to the flat tubes, the heat exchanger provided in a refrigerant circuit configured to perform a refrigerating cycle, wherein   the second header-collecting pipe forms flow spaces which communicate with the plurality of flat tubes and in which a refrigerant being in a gas-liquid two-phase state flows upwardly when the heat exchanger functions as an evaporator,   an effective cross-sectional area of the flow spaces is an area obtained by subtracting a projected area which corresponds to a portion of each flat tube located in a corresponding one of the flow spaces and which is projected onto a plane perpendicular to an axial direction of the second header-collecting pipe, from an area of a cross section of the corresponding one of the flow spaces which is perpendicular to the axial direction of the second header-collecting pipe, and   the effective cross-sectional area of the flow spaces is set based on a mass flow rate at which the refrigerant flows into the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         2 . The heat exchanger of  claim 1 , wherein
 a value included in a variation range of the mass flow rate at which the refrigerant flows into the flow spaces when the heat exchanger functions as the evaporator is determined as a reference mass flow rate M R  [kg/h], and   the effective cross-sectional area A [mm 2 ] of the flow spaces is equal to or greater than (1.91M R −22.7) and equal to or smaller than (1.96M R +30.8).   
     
     
         3 . The heat exchanger of  claim 1 , wherein
 a value included in a variation range of the mass flow rate at which the refrigerant flows into the flow spaces when the heat exchanger functions as the evaporator is determined as a reference mass flow rate M R  [kg/h], and   the effective cross-sectional area A [mm 2 ] of the flow spaces is equal to or greater than (1.96M R −25.0) and equal to or smaller than (1.96M R +30.0).   
     
     
         4 . The heat exchanger of  claim 2 , wherein
 the reference mass flow rate M R  [kg/h] is an upper limit value of the variation range of the mass flow rate at which the refrigerant flows into the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         5 . The heat exchanger of  claim 1 , wherein
 the first header-collecting pipe and the second header-collecting pipe are in an upright position, and   the heat exchanger is configured such that the refrigerant flows into a lower end portion of each of the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         6 . The heat exchanger of  claim 3 , wherein
 the reference mass flow rate M R  [kg/h] is an upper limit value of the variation range of the mass flow rate at which the refrigerant flows into the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         7 . The heat exchanger of  claim 2 , wherein
 the first header-collecting pipe and the second header-collecting pipe are in an upright position, and   the heat exchanger is configured such that the refrigerant flows into a lower end portion of each of the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         8 . The heat exchanger of  claim 3 , wherein
 the first header-collecting pipe and the second header-collecting pipe are in an upright position, and   the heat exchanger is configured such that the refrigerant flows into a lower end portion of each of the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         9 . The heat exchanger of  claim 4 , wherein
 the first header-collecting pipe and the second header-collecting pipe are in an upright position, and   the heat exchanger is configured such that the refrigerant flows into a lower end portion of each of the flow spaces when the heat exchanger functions as the evaporator.   
     
     
         10 . The heat exchanger of  claim 6 , wherein
 the first header-collecting pipe and the second header-collecting pipe are in an upright position, and   the heat exchanger is configured such that the refrigerant flows into a lower end portion of each of the flow spaces when the heat exchanger functions as the evaporator.