Investigation of Refrigerant R134a Two Phase Flow Heat Transfer in Vertical Heat Exchanger Channel
Keywords:Heat transfer, Flow boiling, , Pressure drop, Heat flux
AbstractTwo phase flow boiling heat transfer and pressure drop in the vertical evaporator tube section of refrigeration system have been experimentally investigated using refrigerant R134a as a working fluid. The objective of the present work is to investigate experimentally the effect of heat flux, mass flux, vapor quality and saturation temperature on refrigerant flow boiling heat transfer characteristics in the evaporator of refrigeration system. These investigated parameters have significant impacts to enhance the thermal performance of the evaporator. The experimental investigations were conducted in smooth copper tube with inner diameter 5.8 mm and 600 mm length under different test conditions. The test conditions considered in this study were, for heat flux of 7.718-32.78 kW/m2, mass flux of 97.3-148.7 kg/m2.s , saturation temperature of -20.58 to -15.68 ?C and vapor quality of 0.3-1. It can be concluded from the results that, the average heat transfer coefficient at relatively greater mass flux 148.7 kg/m2.s was higher in range of 21% compared to other mass fluxes at constant test conditions. The relatively higher value of heat transfer coefficient was observed at heat flux 32.78 kW/m2 with average increase of 19% compared to the relatively lower value 23.38 kW/m2. The enhancement in local heat transfer coefficient at saturation temperature -15.68?C was higher by about 12% than that for the relatively lower temperature -20.58?C. The effect of increase in mass flux and heat flux on pressure drop in the evaporator tube was about 9% and 7.5% respectively.
Martin Callizo, Claudi. "Flow boiling heat transfer in single vertical channels of small diameter" Diss. KTH, (2010).
Anwar, Zahid. "Flow boiling heat transfer, pressure drop and dry out characteristics of low GWP refrigerants in a vertical mini-channel" Diss. KTH Royal Institute of Technology, (2014).
Patel, Giteshkumar N. "CFD Simulation of Two-phase and Three-phase Flows in Internal-loop Airlift", (2010).
Chen, L., Y. S. Tian, and T. G. Karayiannis. "Vertical upward flow patterns in small diameter tubes." (2005).
Huo, Y., Tian S., and Karayiannis, T. G. "R134a flow boiling heat transfer in small diameter tubes." RT Edwards Inc., (2007).
Mahmoud, Mohamed M., Tassos G. Karayiannis, and David BR Kenning. "Surface effects in flow boiling of R134a in microtubes." International Journal of Heat and Mass Transfer, 54, pp15-16, (2011).
Ali, Rashid, Björn Palm, and Mohammad H. Maqbool. "Flow boiling heat transfer characteristics of a minichannel up to dryout condition." Journal of Heat Transfer 133.8 (2011): 081501.
Pike-Wilson, Emily A., Mohamed M. Mahmoud, and Tassos G. Karayiannis. "Flow boiling of R134a and R245fa in a 1.1 mm diameter tube." ASME 2013 11th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers Digital Collection, (2013).
Fang, Xiande. "A new correlation of flow boiling heat transfer coefficients based on R134a data." International Journal of Heat and Mass Transfer ,66, (2013).
Mancin, Simone, Andrea Diani, and Luisa Rossetto. "R134a flow boiling heat transfer and pressure drop inside a 3.4 mm ID microfin tube." Energy Procedia, 45, (2014).
Li, Wei, et al. "Effects of heat flux, mass flux and two-phase inlet quality on flow boiling in a vertical super hydrophilic microchannel", International Journal of Heat and Mass Transfer,119, (2018).
Collier J. G. and J. R. Thome, "Convective boiling and condensation", Third ed., Oxford University press, pp. 176, (1994).
Copetti, J. B., Macagnan, M. H., Zinani, F., and Kunsler, N. L., "Flow boiling heat transfer and pressure drop of R-134a in a mini tube: an experimental investigation", Experimental Thermal and Fluid Science, Vol. 35, pp 636-644, (2011).
Ong, C. L., and J. R. Thome. "Macro-to-microchannel transition in two-phase flow: Part 2–Flow boiling heat transfer and critical heat flux." Experimental thermal and fluid science 35.6: 873-886. (2011).