A new experimental technique to determine heat transfer coefficient and pressure drop in smooth and micro-fin tube

Abstract

An experimental test facility is designed and built to calculate condensation heat transfer coefficients and pressure drops for HFC-134a in a 10.21 mm ID smooth and 8.56 mm ID 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 develop an empirical correlation for heat transfer coefficient and pressure drop, which takes into account, variation of condensing temperature and mass flux of refrigerant. 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 sealed 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, experimental procedure and data reduction technique. 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 the values of condensation heat transfer coefficients for different mass flux and condensing temperatures were obtained 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 few available correlations. The condensation and pressure drop of HFC-134a in a micro-fin tube are also measured and the values of condensation heat transfer coefficients obtained. The enhancement and penalty factors of HFC-134a are 1.24 - 2.42 and 1 - 1.77 respectively. Key words: Experimental technique, micro-fin tube, condensation heat transfer, pressure drop, heat transfer enhancement.