This process of converting a liquid into a gas and back into a liquid again continues inside the sealed heat pipe as long as the sun shines. Electrochemical behavior of Evacuating flat bottom tanks. In heat pipe evacuated tube collectors, a sealed heat pipe, usually made of copper to increase the collectors efficiency in cold temperatures, is attached to a heat Evacuating flat bottom tanks reflector plate within the vacuum sealed tube. The purpose of these numerical simula. Mater Sci Semicond Process ;16 1: To achieve this goal, a thermo-mechanical 1-way sequential coupling has been used as a solving method.