Thermosyphon-assisted cooling system working in the moderate heat flux range

Abstract

• Thermosyphon-assisted cooling system was used to remove moderate heat fluxes; • 25% filling of a thermosyphon with ethanol provides the best cooling efficiency; • A thermally insulated thermosyphon can be used, but with mixed or forced convection; • The efficiency of thermally insulated thermosyphon is lower than that of uninsulated. Ensuring the permissible temperature regime of heat-loaded and energy-saturated equipment is still an urgent problem in heat power engineering and thermal physics. In this work, it is demonstrated that thermosyphons without a boiling coolant on their lower lid can be used in practice as self-regulating heat exchangers ensuring the permissible temperature regime of heat-loaded and energy-saturated equipment. The experiments showed that heat flux in the range of 0.18–2.60 kW·m −2 can be removed from engineering heated surfaces of equipment by a self-regulating thermosyphon-assisted cooling system (TCS) with intense evaporation of a coolant (without boiling) on its lower lid and air cooling of the condenser due to natural convection. Using modern tools for registration of thermophysical and hydrodynamic processes, the effect of the coolant type, the filling ratio of evaporator and the presence of thermal insulation on the side surface of a TCS on its efficiency was studied. To increase the efficiency of the thermally insulated TCS, it is advisable to create mixed or forced convection above the upper lid with the heat transfer coefficient of 22–53 W·m 2 ·K −1 . It was hypothesized that the heat transfer intensity in the TCS characterizing by the temperature distributions and evaporation rates depends on heat transfer and convection in the liquid layer on the lower lid of the TCS.