Compatibility and reliability of heat pipe materials

To predict the long life capabilities of heat pipes, a life test program was begun eight years ago to evaluate potential heat pipe fluids. Fluids tested range from those suitable in cryogenic applications to those of use in high temperature heat pipes. Stainless steel proved to be acceptable for long term use with all common low temperature fluids except water, which requires copper or monel. Failures were usually caused by material incompatibility or improper cleaning and processing, although breakdown of some high molecular weight organic fluids under heat pipe operating conditions was encountered.