Patent ID: 7621320

Claim:
An internal heat exchanger applied to a vapor compression type refrigerator using carbon dioxide as a refrigerant, having a high pressure passage ( 5 a ) through which a high pressure refrigerant flows and a low pressure passage ( 5 c ) through which a low pressure side refrigerant flows, and conducting heat exchange between said high pressure side refrigerant and said low pressure side refrigerant while the flow of said high pressure side refrigerant and the flow of said low pressure side refrigerant constitute counter-flows, wherein: when the length units are millimeters and a corresponding diameter of said high pressure passage ( 5 a ) is Ψh, a passage length (Lh) of said high pressure passage ( 5 a ) is greater than 9.16/{LN(4.5 −Ψh +1.03)} and smaller than 46/{LN(4.5 −Ψh +1.03)}, and when a length unit is millimeter and a corresponding diameter of said low pressure passage ( 5 c ) is Ψl, a passage length (Ll) of said low pressure passage ( 5 c ) is greater than 9.16/{LN(0.56×6 −Ψl +1.02)} and smaller than 46/{LN(0.56×6 −Ψl +1.02)}.