A heat exchanger is used in a vapor-compression type refrigerator where a pressure
of a refrigerant at a high-pressure portion reaches and exceeds a critical pressure.
A low-pressure refrigerant flows through the heat exchanger. The heat exchanger
comprises a flat tube; refrigerant channels included in the tube; and inner pillars
disposed between the refrigerant channels. A tensile strength of material of the
tube is defined as S [N/mm2]; of one of the refrigerant channels, a
dimension approximately parallel with a major-axis direction of the tube, as Wp
[mm]; and, of one of the pillars, a thickness approximately parallel with the major-axis
direction of the tube, as Ti [mm]. Here, [447Wp/{10^(1.54log10S)}-;533/{10^(1.98log10S)}]Ti[447Wp/{10^(1.54log10S)}-;533/{10^(1.98log10S)}]2.3.
