Patent ID: 7243703

Claim:
A flexible heat exchanger comprising a pair of flexible multilayer thermoplastic polyimide films each of which comprises an aromatic polyimide substrate film showing no glass transition temperature or a glass transition temperature of 340° C. or higher and a thermoplastic aromatic polyimide surface film showing a glass transition temperature in the range of 190 to 300° C. in which the surface films of the flexible multilayer thermoplastic polyimide films face each other and are in part fused together, whereby producing between the flexible multilayer thermoplastic polyimide films a conduit pattern through which a fluid passes, wherein said flexible multilayer thermoplastic polyimide films have a thickness in the range of 10 to 125 μm and comprises a linear expansion coefficient of MD, a linear expansion coefficient of TD and an average of linear expansion coefficients of MD and TD, in the range of 10×10 −6 to 35×10 −6 cm/cm/° C. at 50-200° C.