EXPERIMENTAL APPARATUS FOR MEASURING IN TUBE CONDENSATION HEAT TRANSFER COEFFICIENT AND PRESSURE DROP USING SMOOTH AND MICRO-FIN TUBES FOR HFC REFRIGERANTS

An experimental test facility is designed and built to calculate condensation heat transfer coefficients and pressure drops for HFC-134a, R-404A, R-407C, R-507A in a smooth and micro-fin tube. The main objective of the experimentation is to investigate the enhancement in condensation heat transfer coefficient and increase in pressure drop using micro-fin tube for different condensing temperatures and further to develop an empirical correlation for heat transfer coefficient and pressure drop, which takes into account the micro-fin tube geometry, variation of condensing temperature and temperature difference (difference between condensing temperature and average temperature of cooling medium). The experimental setup has a facility to vary the different operating parameters such as condensing temperature, cooling water temperature, flow rate of refrigerant and cooling water etc and study their effect on heat transfer coefficients and pressure drops. The hermetically scaled reciprocating compressor is used in the system, thus the effect of lubricating oil on the heat transfer coefficient is taken in to account. This paper reports the detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure. It also covers the comparative study of experimental apparatus with the existing one from the available literature survey. The condensation and pressure drop of HFC-134a in a smooth tube are measured and obtained the values of condensation heat transfer coefficients for different mass flux and condensing temperatures using modified Wilson plot technique with correlation coefficient above 0.9. The condensation heat transfer coefficient and pressure drop increases with increasing mass flux and decreases with increasing condensing temperature. The results are compared with existing available correlations for validation of test facility. The experimental data points have good association with available correlations except Cavallini-Zecchin Correlation