An experimental study of boiling and condensation co-existing phase change heat transfer in small confined space

摘要

The experimental results of boiling and condensation co-existing phase change heat transfer characteristics in a small confined space are presented. The working medium used is de-ionized water, the heating and cooling surfaces are polished copper. The confined space is a closed chamber that consists of a heating copper block whose top surface is used for boiling, a cooling copper block whose bottom surface is used for condensing and a circular wall made of stainless steel. The distance between the heating and cooling surfaces of the confined chamber is 26 mm, and the water layer thickness in the chamber is set at 10 mm, 12 mm, 14 mm and 16 mm, respectively. Experimental observation and results show that boiling and condensation processes are strongly inter-related and have significant influences over each other. As the water level increases, the boiling heat transfer coefficient increases at first and then decreases. Analysis of the standard deviations of the confined space pressure shows that as the heat flux increases, the pressure fluctuation increases first and then tends to maintain a constant. The experimental results also disclose that there exists an optimum water filling amount at which both the boiling and the condensation heat transfer coefficient acquire their maximum value.