Heat transfer in the evaporation zone of aluminum grooved heat pipes

The paper deals with the results of experimental study of heat transfer and visualization of transport processes in the evaporation zone of aluminum heat pipes. Heat pipes had an external diameter equal to 10.0, 12.5, 14.0 and 17.0 mm and a capillary structure shaped as axial grooves of Ω-shaped cross section at their inner surface. Different heat transfer regimes and their emergence as a function of coolant type, geometry of capillary structure shaped as grooves, effective length and heat load level are found. The obtained generalized formulas enable one to calculate heat transfer coefficient in the evaporation zone of ammonia-, acetone- and pentane-fuelled aluminum heat pipes with Ω-shaped longitudinal axial grooves over the range of the heat flux from 0.1 W/cm2 to 8.0 W/cm2. The physical model of thermal and hydraulic processes in the evaporation zone of aluminum heat pipes is proposed.