To reduce the internal thermal resistance, twisted and Z-type turbulent flow generators are incorporated into the evaporator tubes. Under this condition, the internal and external thermal resistances on the inside and outside of the evaporator tubes account for up to 73% of the overall thermal resistance. The results show an optimum water height equal to 80% of the tube diameter leading to achieve the highest cooling power. To resolve this issue, we experimentally investigate the performance of a flooded evaporator as a function of water height. In an adsorption chiller, the refrigerant (water) operating pressure is low (0.5e5 kPa) and the cooling power generation of a flooded evaporator is affected by the height of water column. Additionally, it was found that the pressure drop correlation proposed by Kanizawa and Ribatski (2012) is suitable to be used as a design tool because it predicted 99% of the present database within an error band of ☓0%. In general, it was concluded that the use of reduced twist-ratios values provide higher overall heat transfer enhancement factors for intermediary vapor quality. The predictive methods available in the literature were compared against the experimental data obtained in the present study. The experiments were performed for R134a as working fluid covering mass velocities from 75 to 200 kg/m2 s, heat fluxes of 5 and 10 kW/m2 and saturation temperatures of 5 and 15 <. Experimental results were obtained for horizontal 12.7 and 15.9 mm ID tubes without and with twisted-tape for twistratios of 3, 4, 9 and 14. Based on these data, an analysis of the heat transfer enhancement and pressure drop penalty due to the use of twisted-tapes is performed. This paper presents experimental data for pressure drop and heat transfer coefficient for two-phase flows in tubes containing twisted-tape inserts.
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