Condensation pressure drop of HFC-134a and R-404A in a smooth and micro-fin U-tube

Experimental study of the pressure drop during condensation in an inclined smooth tube at different saturation temperatures

“…In this work, it was reported that -6 -heat transfer coefficient decreased with saturation temperature. Patil and Sapali [21], in their experimental study of the condensation of R134a and R404A in both smooth and microfinned U-tubes, reported a decrease in frictional pressure drop with saturation temperature of up to 23.5% and 45.6% in the smooth and microfinned tube respectively. Similarly, Kim et al [22] noted a decrease in pressure drop with an increase in saturation temperature for diabatic CO Ghajar [24]to obtain the void fraction.…”

Heat transfer, void fraction and pressure drop during condensation inside inclined smooth and microfin tubes

“…As mentioned, the pressure penalty factor (PF) is defined as the ratio of the frictional pressure drop of the microfin tube to the frictional pressure of the smooth tube [20,26].…”

“…The heat transfer coefficient enhancement factor for R134a was between 1.5 and 2.5, while that of R404a was between 1.3 and 2.0. In another paper by the same authors [26], they considered microfin U-tubes and found that as the saturation temperature was increased between 35 °C and 60 °C, the frictional pressure drop decreased by up to 23.5% and 45.6% in the smooth tube and the corresponding microfin tube respectively. Colombo et al [27] considered the flow pattern, heat transfer and pressure drop for evaporation and condensation of R134a in two horizontal microfin tubes.…”