Abstract
Evacuated Tube Solar Water Heaters (ETSWHs) have superior thermal performance in Northern Maritime Climates compared with Flat Plate Solar Water Heaters (FPSWHs) delivering 5% to 15% more energy per annum. ETSWHs with heat pipe absorbers are especially suited for use in Northern Maritime Climates due to their freeze tolerance and self-regulating thermal diode characteristics. ETSWHs have a higher capital cost than FPSWHs and have yet to be extensively tested and optimised under Northern Maritime climatic conditions. The adoption of thermosyphon fluid circulation in conjunction with ETSWHs has the potential to reduce capital and maintenance costs whilst increasing reliability, without affecting thermal performance. Previous research has reported that inclining thermosyphons influences flow structure and only focused on inclined cylindrical manifolds with a single orifice, and the inlet and outlet located at the same end of the inclined manifold. Other research into enclosed natural convection has focused on inclined rectangular cavities. This paper describes the construction of a truncated, 5-pin fin system, laboratory model of a proprietary ETSWH manifold. This manifold has separate orifices for the inlet and outlet, with an irregularly shaped 6-sided, rather than cylindrical or rectangular manifold cross section. This was incorporated into a collector loop and storage tank mimicking an operational thermosyphon solar water heating system. A range of existing empirical relationships for natural convection within enclosed horizontal cavities was compared to the experimental data. It was found that the best agreement was obtained for the case of natural convection from inclined horizontal smooth cylinders
| Original language | English |
|---|---|
| Title of host publication | Renewable energy in maritime island climates, conference proceedings REMIC 2 |
| Place of Publication | Abingdon, UK |
| Publisher | International Solar Energy Society |
| Pages | 369-374 |
| ISBN (Print) | 0 90496372 1 |
| Publication status | Published (in print/issue) - 28 Apr 2006 |
Bibliographical note
Reference text: Beikircher T, Goldemund G, Benz N, 1996, Gas heat conduction in an evacuated tube solar collector, Solar Energy, volume 58 issue 4-6, pp. 213-217.Behnia M and Morrison G, 1991, An experimental investigation of inclined open thermosyphons, Solar Energy, volume 47, pp.313-326.
Cengel Y A, 1998, Heat transfer A Practical Approach, McGraw-Hill.
Cesini G, Paroncini M, Cortella G and Manzan M, 1999, Natural convection from a horizontal cylinder in a rectangular cavity, International Journal of Heat and Mass Transfer, Volume 42, pp.1801-1811.
DTI Energy Statistics, 2005, Department of Trade and Industry (DTI) Energy Statistics: Total Energy.
Gaa F, Behnia M and Morrison G, 1996, Experimental study of flow rates through inclined open thermosyphons, Solar Energy, volume 57, pp.401-408.
Harding G and Zhiqiang Y, 1985, Thermosyphon circulation in solar water heaters incorporating evacuated tubular collectors and a novel water-in-glass manifold, Solar Energy, volume 34, pp. 13-18.
Incropera F P and Dewitt D P, 1996, Fundamentals of Heat and Mass transfer, John Wiley and Sons, 4th ed.
Lacroix M and Joyeux A, 1996, Coupling of Wall conduction with Natural Convection from heated Cylinders in a rectangular Enclosure, International Communications in Heat and Mass Transfer, volume 23, Issue 1, pp.143-151.
Lee J H and Goldstein R J, 1988, An experimental Study on natural Convection heat Transfer in an Inclined Square Enclosure Containing Internal Energy Sources, Journal of Heat Transfer.
Mathioulakis E and Belessiotis V, 2001, A new heat-pipe type solar domestic hot water system, Solar Energy, volume 72, issue 1, pp.13-20.
Morgan V T, 1975, The Overall Convective heat transfer from smooth circular cylinders, Advances in heat transfer, volume 11, pp.199-264
Morrison G, Budihardjo I, Behnia M, 2004, Water-in-glass evacuated tube solar water heaters, Solar Energy, volume 76, issues 1-3, pp. 135-140.
Morrison G, Budihardjo I, Behnia M, 2005, Measurement and Simulation of Flow Rate in a Water-in-glass evacuated tube solar water heater, Solar Energy, volume 78, pp.257-267.
Morrison G, Tran N, McKenzie D, Onley I, Harding G, Collins R, 1984, Long-term performance of evacuated tubular solar water heaters in Sydney, Australia, Solar Energy, volume 32, pp.785-791.
Murphy J M, Sexton D M H, Barnett D N, Jones G S, Webb M J, Collins M and Stainforth D A, 2004, Quantification of modelling uncertainties in a large ensemble of climate change simulations, Nature, volume 430, pp.768-772.
Norton B, Eames P C and Lo S, 2001, Alternative approaches to thermosyphon solar energy water heater performance analysis and chararacterisation, Renewable and Sustainable Energy Reviews, pp79-96, volume 5, issue 1.
Sezai I and Mohamad A A, 2000, Natural Convection from a discrete heat source on the bottom of a horizontal enclosure, International Journal of Heat and Mass Transfer, volume 43, pp2257-2266.
Tso C P, Jin L F, Tou S K W, Zhang X F, 2004, Flow pattern evolution in natural convection cooling from an array of discrete heat sources in a rectangular cavity at various orientations, International Journal of Heat and Mass Transfer, volume 47, pp.4061-4073.
Zhiqiang Y, Harding G, Craig S, Collins R and Window B, 1985, Comparative study of fluid-in-metal manifolds for heat extraction from single ended evacuated glass tubular collectors, Solar Energy, volume 35, pp.81-91.
Zhukauskas A, 1972, Heat transfer from tubes in cross flow, Advances in Heat Transfer, volume 8, academic press.
Keywords
- natural convection
- solar energy
- fluid flows
