Experimental investigation of flow and heat transfer characteristics of R -134A in microchannels
Date of Award
Doctor of Business Administration (DBA)
The purpose of this study was to investigate the flow and heat transfer characteristics of liquid refrigerant R-134a in rectangular microchannels. The research concentrated mostly upon single-phase experiments with limited investigation of boiling phenomenon in microchannels. Tests were performed using rectangular microchannels with hydraulic diameters ranging from 112 μm to 210 μm and aspect ratios varying approximately from 1.0 to 1.5. The Reynolds number in the experiments ranged from 1,200 to 13,000 although most data were collected in the transition and turbulent flow regimes.
The experimental data for friction factor measurement had a similar trend as predicted by macroscale theory but with consistently lower values of friction factor. The uncertainty associated with friction factor measurement varied from 3% to 23.3% for all of the four channel configurations studied, whereas the Reynolds number uncertainty was within 10% for all measurements. The experimental data provided an excellent correlation to predict friction factor for Re > 4000. The heat transfer rate and Nusselt number were found to be much lower, ranging from 5% to 84% lower than theoretical predictions while the uncertainty associated with Nusselt number varied from 20% to 67%, approximately. Two different modes of heat transfer were observed, the larger channels providing a much higher rate of heat transfer compared with the two smaller configurations. A maximum heat flux of 16 W/cm2 was achieved in single-phase experiments associated with a pressure drop of about 653 kPa.
Bari, Abdullahel, "" (2010). Dissertation. 716.