Journal of Applied Science and Engineering

Published by Tamkang University Press


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K. S. Ong This email address is being protected from spambots. You need JavaScript enabled to view it.1 and W. L. Tong1

1School of Engineering, Monash University Sunway Campus, Jalan Lagoon Selatan, 46150 Bandar Sunway, Malaysia


Received: March 22, 2012
Accepted: May 23, 2012
Publication Date: June 1, 2012

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System performance of solar water heaters depend upon collector and storage tank design and sizing and weather conditions (solar radiation intensity and ambient temperature). Nocturnal reverse flow and tank insulation dictate the degree of overnight water temperature drop in the storage tank. A tropical country like Malaysia has widely fluctuating and intermittent solar radiation. It is neither practical nor feasible to conduct outdoor tests such as that proposed by International Standards. Indoor collector tests are expensive to conduct and would not provide meaningful information to the domestic or commercial end user. Outdoor system tests would be more informative to consumers who would like to compare the water temperatures that could be achieved in order to choose from the wide range of commercial products available. This paper reports the results of outdoor tests conducted on several evacuated tube solar collectors (U-tube and heat pipe types) under natural and forced convection. Although tested at different times, the long and short term test procedures employed allowed us to compare the performances of the various systems as if they were tested simultaneously side-by-side. It was found that the natural convection heat pipe system performed best among them.

Keywords: Heat Pipe, U-Tube, Solar Water Heater, Natural Convection, Forced Convection


  1. [1] Morrison, G. L. and Tran, N. H., “Long Term Performance of Evacuated Tubular Solar Water Heaters in Sydney, Australia,” Solar Energy, Vol. 32, pp. 785 791 (1984).
  2. [2] Ma, L., Lu, Z., Zhang, J. and Liang, R., “Thermal Performance of the Glass Evacuated Tube Solar Collector with U-Tube,” Building and Environment, pp. 1959 1967 (2010).
  3. [3] Chun, W., Kang, Y. H., Kwak, H. Y. and Lee, Y. S., “An Experimental Study of the Utilization of Heat Pipes for Solar Water Heaters,” Applied Thermal Engineering, Vol. 19, pp. 807817 (1999).
  4. [4] AS/NZS 4445.1: 1997. Solar Heating  Domestic water heating systems  Part 1: Performance rating procedure using indoor test methods (1997).
  5. [5] AS/NZS 2535.1:2007. Test Methods for solar collectors - Part 1: Thermal performance of glazed liquid heating collectors including pressure drop (2007).
  6. [6] Ong, K. S., “Experimental Performance Testing of Solar Water Heaters,” Int. Journal Low Carbon Technology (2011).