COMPATIBILITY TESTS OF VARIOUS HEAT PIPE WORKING FLUIDS AND STRUCTURAL MATERIALS AT DIFFERENT TEMPERATURES.

Abstract

Lifetest investigations with ammonia heat pipes, using stainless steel and aluminum as structural materials, and long-term compatibility tests with working fluids for temperatures above 100 degree C together with various structural materials have been carried out. Ammonia heat pipes with aluminum envelope and stainless steel wick showed a rapid and increasing build-up of non-condensible gas. All-aluminum and all-stainless steel heat pipes had an acceptable to excellent long-term performance. Whilst no gas generation could be detected with the stainless steel heat pipes, a minor gas generation occured with the aluminum heat pipes. Major results from other long-term compatibility tests are that copper/water heat pipes can be recommended up to temperatures of about 220 degree C. Diphyl may be used for many purposes in combination with both mild steel and aluminum for temperatures ranging from 180 to 250 degree C, however, it is not compatible with copper. From other organic working fluids octane and, to a lesser degree, decane were found to be compatible with mild steel.