Abstract
Heat exchanger developments are driven by increase in energetic efficiency and emission reduction. To reach the required standards, new systems are required based on mini-channels along with macro channels also. Mini-channels can be described as tubes with one or more ports extruded in aluminium or any other material like copper, steel etc. with hydraulic diameter in the range of 0.2 to 3 mm. Its use in refrigeration systems became a reality; thanks to the human ability to make micro-scale systems. Some heat exchanger enterprises have some models developed specially for their use in automotive sector, cooling sector and industrial refrigeration without having knowledge of how these reduced geometries affect the most important parameters such as pressure drop and the heat transfer coefficient. To overcome this, an exhaustive literature review of the last two decades has been performed to determinate the state of the research. Among all the publications, several models have been reviewed to check the predicting capacities of them as most of them were developed for macro channels along with single port mini-channel tubes. This work presents a comparative study of existing heat transfer correlations for horizontal flow through mini-channels. Present work total 317 experimental results of condensation heat transfer coefficient obtained from several published literatures and also various condensation heat transfer correlations are reviewed for horizontal flow through mini-channels. Results of condensation heat transfer coefficient obtained for various correlations are compared with the experimental results. Among all correlations used the Bohdalet’s correlation gives value of condensation heat transfer coefficient closer to experimental results and has a mean relative deviation (MRD) of 5.4 % whereas mean absolute relative deviation (MARD) of 20.72%.Hence in present work the effort has been made to find better model to predict the condensation heat transfer coefficient which can fit the experimental data with least MRD and MARD.
Highlights
Nowadays, micro and mini-channels are present in many applications ranging from different heat exchangers in process industry to automotive, electronics and domestic applications
Compactness is a synonym of charge reduction and this is very important in present day refrigeration systems and heat pumps because of the great contribution of HCFC and HFC refrigerants to the direct greenhouse effect
Multi-port mini channels had hydraulic diameters of 1.5, 0.78 and 0.68 mm and they were tested from -5 to 5 oC of saturation temperature
Summary
Micro and mini-channels are present in many applications ranging from different heat exchangers in process industry to automotive, electronics and domestic applications. A good revision of recent condensation heat transfer coefficient and pressure drop in tubes of small and large diameter can be found in English and Kandlikar [7].Yang and Webb [8] studied R12 condensation in plain micro-finned multi-port extruded tubes with hydraulic diameters of 2.637 and 1.564 mm. They compared against the correlations developed by Akers et al [9] and Shah and London [10]. Round single port tubes and multi-port tubes are going to reach the same condensation performance
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