An important parameter in the hydraulic design of refrigeration and air-conditioning systems is the two-phase flow pressure drop. In this paper, the authors compare the numerical results obtained by using seven two-phase pressure-drop models with the experimental results found in the scientific literature, for the condensation of R600a and R717 (Ammonia = NH3) in horizontal tubes. Different mass flow rates and different conditions have been considered in order to see which correlation is applicable under specific operation conditions.
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