Refrigeration efficiency improvement via heat transfer enhancement

Thiruselvam, R. and Yusof, Mohammad Zainal and Raghavan, Vijay R. (2007) Refrigeration efficiency improvement via heat transfer enhancement. In: 1st Engineering Conference (EnCon 2007), 28 December 2007, Universiti Malaysia Sarawak, Sarawak.

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Abstract

The criticality in the improvement of refrigeration system efficiency has now shifted to heat exchangers that need to work across the least possible temperature difference. With smaller temperature differences across the evaporator and condenser, the compressor work is reduced and energy efficiency is improved. To reduce these temperature differences, techniques of heat transfer enhancement are needed. This forms the basis of the present study in which heat transfer characteristics of enhanced annuli are studied experimentally in a water-cooled condenser. Normally superheated refrigerant vapour enters the condenser in turbulent flow conditions, and exits as subcooled liquid which is in the transition region of flow. The annulus-side coefficients are determined using the Wilson Plot technique. The results for the augmented surface are presented graphically and compared with the non-augmented case. For turbulent flow of vapour in plain annuli, the form of the correlation by Monrad and Pelton was satisfactory. For vapour in enhanced annuli, the correlation of Knudsen and Katz determined the basic form. The enhanced annulus outperforms the plain tube by about 25%-30% for superheated vapour heat transfer coefficient. The new empirical constants resulted in good prediction for turbulent superheated vapour flow in the annulus for both plain and enhanced annuli. For the single phase heat transfer correlation proposed, all predicted data are within +5% of experimental values. Though R-22 has been chosen for the present study, the dimensionless form of presentation of results enables the correlations to be applied to other refrigerants.

Item Type:Conference or Workshop Item (Paper)
Uncontrolled Keywords:heat transfer enhancement; refrigeration systems; energy efficiency improvement
Subjects:T Technology > TP Chemical technology > TP489-498 Low temperature engineering. Cryogenic engineering. Refrigeration. Ice cutting and storage
Divisions:Faculty of Mechanical and Manufacturing Engineering > Department of Aeronautical Engineering
ID Code:4153
Deposited By:Normajihan Abd. Rahman
Deposited On:03 Sep 2013 10:29
Last Modified:21 Jan 2015 15:50

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