Two-phase flow pressure drop and heat transfer characteristics of refrigerants in vertical tubes

An experimental study was made of the flow regime, pressure drop, heat transfer coefficient, and critical heat flux of R-114 boiling in a 0.785-in.-ID, 10-ft-long vertical tube. The boiling temperature was varied in the range of 100 to 250 F for all tests except the heat transfer coefficient runs where the range 100 to 200 F was studied. Analytic and experimental techniques were used to investigate the heat transfer and pressure drop characteristics. An improvement in the prediction of the system behavior was obtained and the discrepancies between the behavior of boiling refrigerants and other working fluids was explained. Equations were developed or existing ones verified so that design engineers requiring information on the two-phase flow characteristics of refrigerants in vertical tubes at operating conditions not too different from those studied here may use the equations presented here. The limitations of each equation are also presented.