Experimental investigation of an inclined-condenser wickless heat pipe charged with water and an ethanol–water azeotropic mixture

Abstract

This paper examines the advantages of using the ethanol–water azeotrope as a wickless heat pipe working fluid and the suitability of an inclined condenser structure for a horizontal evaporator operation. Water has, also, been tested as a working fluid for the heat pipe for comparison with the azeotrope results. The tested wickless heat pipe, or as sometimes is referred to as two-phase closed thermosyphon (TPCT), is made from copper with a condenser section that is 12° inclined from the evaporator section. Ethanol–water azeotrope is chosen as a TPCT working fluid as of the expected benefits and thermal characteristics enhancements of this azeotropic mixture is thought to bring. A variable output electrical heater was used to heat the evaporator section. The condenser section was cooled using an enhanced heat exchanger equipped with a twisted 304 stainless steel tape to cause the cooling water to spiral around the condenser section wall. The effect of the evaporator inclination angle, working fluid and power throughputs on the temperature distribution along the heat pipe and the TPCT overall thermal resistance have been investigated. The TPCT was found to function normally under all the considered evaporator inclination angles (including the horizontal position). In addition, many advantages for the use of the ethanol–water azeotrope have been discovered and reported.