Abstract: A protective passive oxide layer is formed on the inner surfaces of metal heat pipes or tubes including their end caps, welds and accompanying hardware through the use of an oxygen encapsulation method. After cleaning the tube and its accompanying parts, the tube is reassembled and existing gases within the tube are removed thereby creating a vacuum inside the tube. The tube is then filled with pure oxygen and sealed. After the oxygen is sealed within the tube, the sealed tube is heated thereby forming a passive oxide layer, such as magnetite (Fe.sub.3 O.sub.4) on the inner surface of the tube.

Abstract: A heat pipe heat exchanger utilizing a working fluid such as water incorporates heating means for preventing the freezing of the working fluid when the heat exchanger is non-operational. These heating means are located at or near the heat pipe in the lower region of the heat exchanger so as to prevent the freezing of the working fluid. Trapped gases within the heat pipe caused by the reaction of the working fluid with the metallurgy of the pipe are released by heating the working fluid with the heating means in order to increase the gas pressure within the heat pipe until the pressure is greater than the external pressure of the heat pipe. A venting means is used to vent the trapped gases from the heat pipe due to the force of the pressure within the heat pipe.