Heat transfer rate of looped type heat pipes using water and Nak as working fluid under liquid phase flow

The looped type heat pipe which consists of a upward tube and a downward tube, is discussed. Heat is transfered from the heating section in the lower part of the upward tube to the cooling section in the upper part of the downcomer. Driving force for the circulation of the working fluid is given three modes according to the flow in the rise tube: (1) liquid phase flow; (2) two phase flow; and (3) gas phase flow. The heat transfer rate of the looped type heat pipe employing sodium, potassium, mercury, water, etc., as working luid are calculated.