Abstract
Possibility of enhancement of boiling heat transfer under subatmospheric pressure is examined experimentally. The range of pressure is between atmospheric pressure to 5kPa. The heat transfer coefficient decreases dramatically at the pressure of 5kPa. This tendency is not reliant on types of heat transfer surfaces and working fluids, and differences in heat transfer are almost diminished between those obtained by smooth surface using pure water and by using extended surfaces or surfactant solutions. The experimental heat transfer of smooth surface using pure water is nearly agreed with Labountzov’s correlation. Heat transfer performances of pyramid 2.5mm and copper sintering surfaces are rather good at the pressure of 5kPa, and both performances are almost similar except at atmospheric pressure. Sodium myristate is one of the promising surfactant and shows stable performance under low pressure condition. Heat transfer coefficient of smooth surface using pure water increases linearly with decrease in liquid height. However, reduction in liquid height shows tendency to change to film boiling at an early stage.
