Heat exchanger and refrigerant cycle device using the same

Abstract

A heat exchanger usable as an evaporator in a refrigerant cycle device includes a heat exchanging portion configured to perform heat exchange between refrigerant and air so as to evaporate the refrigerant. A thermal deformation member is provided in en entire range on a surface of the heat exchanging portion, to be deformed bordering on a predetermined temperature when the surface of the heat exchanging portion is frosted to produce ice. The thermal deformation member is deformed by a temperature change between a first temperature lower than the predetermined temperature and a second temperature higher than the predetermined temperature, to cause distortion between the surface of the heat exchanging portion and the ice when the ice is attached to the surface of the heat exchanging portion. Thus, the ice attached to the surface of the heat exchanging portion can be effectively removed while heat energy for removing the ice can be reduced.

1 . A heat exchanger usable as an evaporator in a refrigerant cycle device, the heat exchanger comprising:
 a heat exchanging portion configured to perform heat exchange between refrigerant and air so as to evaporate the refrigerant; and   a thermal deformation member provided in en entire range on a surface of the heat exchanging portion, to be deformed bordering on a predetermined temperature when the surface of the heat exchanging portion is frosted to produce ice, wherein   the thermal deformation member is deformed by a temperature change between a first temperature lower than the predetermined temperature and a second temperature higher than the predetermined temperature, to cause distortion between the surface of the heat exchanging portion and the ice when the ice is attached to the surface of the heat exchanging portion.   
     
     
         2 . The heat exchanger according to  claim 1 , wherein the predetermined temperature is lower than freezing point. 
     
     
         3 . The heat exchanger according to  claim 1 , wherein
 the thermal deformation member includes plural thermal deformation parts which are arranged separately in dispersion in the entire range of the surface of the heat exchanging portion.   
     
     
         4 . The heat exchanger according to  claim 3 , wherein a distance between adjacent thermal deformation parts at an upstream portion of an air flow is larger than a distance between adjacent thermal deformation parts at a downstream portion of the air flow, on the surface of the heat exchanging portion. 
     
     
         5 . The heat exchanger according to  claim 1 , wherein the thermal deformation member has an angle portion on its outer surface. 
     
     
         6 . The heat exchanger according to  claim 1 , wherein the thermal deformation member is made of a shape memory alloy. 
     
     
         7 . The heat exchanger according to  claim 6 , wherein
 the thermal deformation member includes a first, member having a transformation temperature, and a second member having a transformation temperature lower than that of the first member,   when temperature of the thermal deformation member is increased from a temperature lower than the transformation temperature of the first member to a temperature higher than the transformation temperature of the first member, the first member becomes in a memorized shape and the second member is deformed by the memorized shape of the first member, and   when the temperature of the thermal deformation member is decreased from a temperature higher than the transformation temperature of the first member to a temperature lower than the transformation temperature, the first member is deformed by elastic force of the second member.   
     
     
         8 . The heat exchanger according to  claim 1 , wherein the thermal deformation member is made of an organic material or a complex material which is deformable by a temperature change bordering on the predetermined temperature. 
     
     
         9 . The heat exchanger according to  claim 1 , wherein the thermal deformation member is made of a bimetal. 
     
     
         10 . The heat exchanger according to  claim 3 , wherein the thermal deformation parts at an upstream portion of an air flow are respectively larger than the thermal deformation parts at a downstream portion of the air flow, on the surface of the heat exchanging portion. 
     
     
         11 . The heat exchanger according to  claim 10 , wherein the sizes of the thermal deformation parts are gradually reduced from an upstream air side to a downstream air side. 
     
     
         12 . The heat exchanger according to  claim 1 , wherein
 the heat exchanging portion includes a plurality of tubes and a plurality of fins which are alternately arranged in an arrangement direction, and   the thermal deformation member is provided on at least one of the tubes and the fins.   
     
     
         13 . A refrigerant cycle device comprising:
 a compressor configured to discharge refrigerant;   a refrigerant radiator in which the refrigerant discharged from the compressor radiates heat;   a decompression device configured to decompress the refrigerant flowing out of the refrigerant radiator;   the heat exchanger according to  claim 1 , adapted as an evaporator for evaporating the refrigerant flowing out of the decompression device; and   a control portion configured to repeatedly change a surface temperature of the heat exchanging portion between a first temperature lower than the predetermined temperature and a second temperature higher than the predetermined temperature.   
     
     
         14 . The refrigerant cycle device according to  claim 13 , wherein the control portion is configured to repeatedly change the surface temperature by changing a refrigerant discharge capacity of the compressor. 
     
     
         15 . The refrigerant cycle device according to  claim 14 , wherein the control portion causes the compressor to be switched between a first operation, in which a discharge capacity of the compressor is lower than that of a normal operation, and a second operation in which the discharge capacity of the compressor is higher than the discharge capacity of the compressor in the first operation, when the surface of the heat exchanging portion of the evaporator is frosted in the normal operation. 
     
     
         16 . The refrigerant cycle device according to  claim 13 , further comprising:
 a bypass passage through which a part of high-temperature refrigerant higher than the refrigerant flowing into the evaporator is introduced to the evaporator; and   a switching portion configured to open or close the bypass passage,   wherein the control portion repeats the opening and closing of the switching portion so as to repeatedly change the surface temperature of the heat exchanging portion, when the surface of the heat exchanging portion is frosted.   
     
     
         17 . The refrigerant cycle device according to  claim 16 , wherein the bypass passage is configured such that a part of the refrigerant after flowing through the evaporator and before flowing into a refrigerant suction side of the compressor is introduced to a refrigerant inlet side of the evaporator.