Heat and mass transfer in heat pipes with noncondensing gas

Abstract

An experimental study is described concerning the performance parameters of heat pipes with noncondensing gas. The test results are found to agree closely with calculations.Heat pipes with noncondensing gas, just as conventional heat pipes, are now widely used in industry.The performance characteristics of a heat pipe with noncondensing gas derive from the fact that the vapor drives the noncondensing gas toward the cold end of the pipe, where a so-called gas lock then forms as a result. Heat pipes with noncondensing gas can be used for thermostatting various heat emitting apparatus components.The purpose of this study was to determine how the amount and the properties of the noncondensing gas affect the transport of energy and mass through heat pipes.It is well known that, as vapor flows through a noncondensing gas, the latter can be trapped in either of three modes: turbulently at high velocities and high pressures, viscously at low velocities and high pressures, or diffusively at low velocities and low pressures [1].When the heat pipe is started, liquid evaporates to form a vapor--gas mixture. From the instant on when the evaporation rate begins to exceed the rate of concentrative and thermal diffusion, the vapor--gas interface gradually shifts toward the condensation zone in the heat pipe. The molar current of vapor is in this case larger than the diffusion current. The condition for a shift of the vapor--gas interface is