In the present work, a new in-tube two phase pressure drop correlation of low GWP refrigerants during condensation and evaporation has been proposed in this paper. This correlation for the prediction of condensation and evaporation pressure drop inside smooth horizontal tube by incorporating the effect of mass velocity, tube geometry and surface tension. By comparing with other existing well-known correlations and the newly proposed correlation of two-phase pressure drop have been used to predict the condensation and evaporation pressure drop of R1234ze(E), R32, R410A, dimethyl ether (DME), CO_2/DME mixtures (10/90, 25/75 and 45/55 weight %) and R1234ze(E)/R32 mixtures (30/70 and 45/55 weight %) inside a horizontal smooth tube. The predicted results have been compared with the available experimental data which is done inside a water heated double tube heat exchanger. The test section is a horizontally installed smooth tube with effective length of 3.6m and inner diameter of 4.35mm. The experiment had been carried out under the conditions of mass flux varying from 147 to 403 kgm~(-2)s~(-1) and the saturation temperatures ranging between 30 and 45°C for condensation and 5-10°C for evaporation, over the vapor quality range 0.00 to 1.00. From the analysis and results of comparison, proposed correlation shows better performance. Proposed correlation can predict all the experimental condensation and evaporation data within ±13.91%.
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