Heat transfer coefficients and pressure drops during in-tube condensation of CO2/DME mixture refrigerant

Local heat transfer coefficients and pressure drops during condensation of pure Dimethyl Ether (DME) and non-azeotropic mixtures of CO2 and DME inside a horizontal smooth tube have been measured experimentally. The mass fractions of CO2 and DME in the mixtures have been varied as CO2/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 CO2 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.