The phenomenon of condensation of low-pressure vapor in a horizontal tube was studied.The interactions between heat flux density

vapor pressure

vapor velocity and the coefficient of heat transfer for filmwise condensation in the tube

the overall coefficient of heat transfer were investigated.The relationships between heat flux density and the overall temperature difference

the difference in temperature and pressure drop at the entrance and the exit of the vapor were investigated as well.Analytical relationships were obtained for calculation of the coefficient of heat transfer for filmwise condensation in the tube.The deviation between the experimental value and the calculated value was lower than ±15%.