Heat transfer coefficients and pressure drops during in-tube condensation of CO 2/DME mixture refrigerant

Abstract

Local heat transfer coefficients and pressure drops during condensation of pure Dimethyl Ether (DME) and non-azeotropic mixtures of CO 2 and DME inside a horizontal smooth tube have been measured experimentally. The mass fractions of CO 2 and DME in the mixtures have been varied as CO 2/DME (39/61, 21/79 mass%) and the refrigerant mass fluxes have been varied from 200 to 500 kg m −2 s −1. The increase of mass fraction of CO 2 in the mixture decreases the heat transfer coefficient and the pressure drop. At the high refrigerant mass flux, the effect of mass transfer resistance on the heat transfer is decreased. Existing prediction method for condensation of binary refrigerant mixtures, which considered the vapor core mass transfer resistance, has been used to predict the present experimental data. Changing of the two-phase frictional multiplier in that prediction method has improved the prediction of the present experimental data.