Solar thermal collectors for buildings use a heat transfer fluid passing through heat exchange channels in the absorber. Flat plate absorbers may pass the fluid through a tube bonded to a thermally conducting plate or achieve lower thermal resistance and pressure drop by using a flooded panel or microchannel design. The pressure drop should be low to minimise power input to the circulating pump.A method is presented for choosing the optimum channel hydraulic diameter subject to geometric similarity and pumping power constraints; this is an important preliminary design choice for any solar collector designer. The choice of pumping power is also illustrated in terms of relative energy source costs.Both microchannel and serpentine tube systems have an optimum passage diameter, albeit for different reasons. Double-pass and flooded panel designs are considered as special microchannel cases. To maintain efficiency, the pumping power per unit area must rise as the passage length increases. Beyond the optimum pumping power the rise in operating cost outweighs the increase in collector efficiency.
Bibliographical noteReference text: Abdel-Khalik, S.I., Heat removal factor for a flat plate collector with a serpentine tube, Solar Energy, Vol. 18, pp 59-64, 1976
Akgun, M.A., Heat removal factor for a serpentine absorber plate, Solar Energy Vol. 41, No. 1, pp 109-111, 1988
Agrawal, S. and Tiwari, G.N., Energy and exergy analysis of hybrid microchannel photovoltaic thermal module, Solar Energy 85 (2011) 356-37021
Arunachala, U.C., Bhatt, M.S. and Sreepathi, L.K., Analytical and experimental investigation to determine the variation of Hottel-Whillier-Bliss constants for a scaled forced circulation flat-plate solar water heater, ASME Journal of Solar Energy Engineering, Oct 2015, vol 137 article 051011
Aste, N., Del Pero, C. and Leonforte, F., Optimization of solar thermal fraction in PVT systems, Energy Procedia 30 (2012) pp8-18
Bracamonte, J and Baritto, M., Optimal aspect ratios for non-isothermal flat plate solar collectors for air heating, Solar Energy 97 (2013) 605-613
Caffell, A., Low flow-rate pump, US patent 5,769,069, June 1998, retrieved from https://patentimages.storage.googleapis.com/pdfs/US5769069.pd
Cerón, J.F., Pérez-García, J., Solano, J.P., García, A. and Herrero-Martín, R., A coupled numerical model for tube-on-sheet flat-plate solar liquid collectors. Analysis and validation of the heat transfer mechanisms. Applied Energy 140 (2015) pp275-287
Chamoli, S., Chauhan, R., Thakur, N.S. and Saini, J.S., A review of the performance of double pass solar air heater, Renewable and Sustainable Energy Reviews 16 (2012) pp481-492
Chen, Z., Furbo, S., Perers, B., Fan, J. and Andersen, E., Efficiencies of flat plate solar collectors at different flow rates Energy Procedia 30 (2012) 65 – 7
Chen, I.Y., Lai, Y.K. and Wang, C-C., Frictional performance of U-type wavy tubes, Journal of Fluids Engineering, Vol 125, Sept 2003, pp880-886.
Colangelo, G., Favale, E., Miglietta, P., de Risi, A., Milanese, M. and Laforgia, D., Experimental test of an innovative high concentration nanofluid solar collector, Applied Energy 154 (2015) pp 874-881
Deng, Y., Zhao, Y., Wang, W., Quan, Z., Wang, L. and Yu, D., Experimental investigation of performance for the novel flat plate solar collector with microchannel heat pipe array (MHPA-FPC), Applied Thermal Energy 54 (2013) 440-449
Del Col, D., Padovan, A., Bortolato, M., Pré, M.D. and Zambolin, E., Thermal performance of flat plate solar collectors with sheet-and-tube and roll-bond absorbers, Energy Vol. 58, Sept 2013, pp 258-269
Do Ango, M., Medale, M. and Abid, C., Optimization of the design of a polymer flat plate solar collector, Solar Energy 87 (2013) 64-75
Dubey, S. and Tiwari, G.N., Analysis of PV/T flat plate water collectors connected in series, Solar Energy 83 (2009) 1485-1498
Duffie, J.A. and Beckman, A., Solar Engineering of Thermal Processes, Wiley, 2013.
Eisenmann W., Vajen, K. And Ackermann, H., On the correlations between collector efficiency factor and material content of parallel flow flat-plate solar collectors, Solar Energy 76 (2004) 381-387
El-Sebaii, A.A., Aboul-Enein, S., Ramadan, M.R.I., Shalaby, S.M. and Moharram, B.M., Thermal performance investigation of double pass-finned plate solar air heater, Applied Energy 88 (2011) pp1727-1739
Evola, G. and Marletta, L., Exergy and thermoeconomic optimization of a water-cooled glazed hybrid photovoltaic/thermal (PVT) collector, Solar Energy 107 (2014) pp12-15
Farahat, S., Sarhaddi, F. and Ajam, H., Exergetic optimisation of flat plate solar collectors, Renewable Energy 34 (2009) 1169-1174
Hassoon, H.M., Pressure drop in 180° bends, Building Services Engineering Research, May 1982, Vol. 3, Issue 2, pp70-74.
Hegazy A.A., Optimization of flow-channel depth for conventional flat plate solar air heaters, Renewable Energy vol 7, No. 1 (1996) pp15-21
Hegazy A.A., Optimizing the thermohydraulic performance of plate solar air heaters operating with variable pumping power, Renewable Energy 18 (1999) 283-304
Henshall, P, Eames, P., Arya, F., Hyde, T., Moss, R. and Shire, S., Constant temperature induced stresses in evacuated enclosures for high performance flat plate solar collectors, Solar Energy 127 (2016) pp250-26122
Hernández, A.L. and Quiñonez, J.E., Analytical models of thermal performance of solar air heaters of double-parallel flow and double-pass counter flow, Renewable Energy 55 (2013) pp380-391
Ho, C-D., Chuang, Y-J. and Tu, Y-J, Double-pass flow heat transfer in a parallel-plate channel for improved device performance under uniform heat fluxes, International Journal of Heat and Mass Transfer 50 (2007) pp2208-2216
Hottel, H.C. and Whillier, A., Evaluation of Flat-Plate Collector Performance. Trans. of the Conference on the Use of Solar Energy, Vol 2., P.I.74, University of Arizona Press (1958).
Hussien, A.A., Abdullah, Mohd Z., Al-Nimr, Moh’d A., Single-phase heat transfer enhancement in micro/minichannels using nanofluids: Theory and applications, Applied Energy 164 (2016) pp733-755
Kakac, S., Shah, R.K. and Aung, W., Handbook of single-phase convective heat transfer, John Wiley & Sons, 1987
Lorenzini, M. And Morini, G.L., Poiseuille and Nusselt numbers for laminar flow in microchannels with rounded corners, 2nd Micro and nano Flows Conference, London, September 2009 http://bura.brunel.ac.uk/bitstream/2438/6936/1/MNF2009.pdf (accessed 8/9/2015)
Lund, K. O’Ferrall, General thermal analysis of serpentine-flow flat plate solar collector absorbers, Solar Energy Vol. 42, No. 2, pp 133-142, 1989
Mansour, M.K., Thermal analysis of novel mini channel-based solar flat plate collector, Energy 60 (2013) 333-343
Massey, B., Mechanics of Fluids, Chapman & Hall 1989.
Nikoofard, S., Ugursal, V.I. and Beausoleil-Morrison, I., An investigation of the technoeconomic feasibility of solar domestic hot water heating for the Canadian housing stock, Solar Energy 101 (2014) pp308-320
Notton, G., Motte, F., Cristofari, C. and Canaletti, J-L., Performances and numerical optimization of a novel thermal solar collector for residential building, Renewable and Sustainable Energy Reviews 33 (2014) pp 60-73
Othman, M.Y., Yatim, B., Sopian, K. and Bakar, M.N.A., Double-Pass Photovoltaic-Thermal Solar Collector, Journal of Energy Engineering, 2006, 132(3) pp121-126
Oyinlola, M.A., Shire, G.S.F and Moss. R.W. (2015a), The significance of scaling effects in a solar absorber plate with microchannels, Applied Thermal Engineering 90 (2015) 499-508
Oyinlola, M.A., Shire, G.S.F and Moss. R.W. (2015b), Investigating the effects of geometry in solar thermal absorber plates with microchannels, International Journal of Heat and Mass Transfer 90 (2015) pp552-560.
Oyinlola, M.A., Shire, G.S.F and Moss. R.W. (2015c), Thermal analysis of a solar collector absorber plate with microchannels, Experimental Thermal and Fluid Science, Vol. 67, Oct 2015, pp 102-10
Radwan, A, Ookawara, S. and Ahmed, M, Analysis and simulation of concentrating photovoltaic systems with a microchannel heat sink. Solar Energy 136 (2016) pp35-48
Roberts, D.E., A figure of merit for selective absorbers in flat plate solar water heaters, Solar Energy 98 (2013) 503-510
Sharma, N. and Diaz, G., Performance model of a novel evacuated-tube solar collector based on minichannels, Solar Energy 85 (2011) 881-890
Sopian, K., Yigit, K.S., Liu, H.T., Kakaç, S and Veziroglu, T.N., Performance analysis of photovoltaic thermal air heaters, Energy Conversion Management Vol. 37, No. 11, pp 1657-1670, 1996.
Sun, X., Wu, J., Dai, Y. and Wang, R., Experimental study on roll-bond collector/evaporator with optimized channel used in direct expansion solar assisted heat pump water heating system. Applied Thermal Engineering 66 (2014) pp 571-579
Visa, I., Duta, A., Comsit, M., Moldovan, M., Ciobanu, D., Saulescu, R. and Burduhos, B., Design and experimental optimisation of a novel flat plate solar thermal collector for facades integration, Applied Thermal Engineering 90 (2015) pp432-443
Xu, P., Shen, J., Zhang, X., He, W. and Zhao, X., Design, Fabrication and Experimental Study of a Novel Loop heat-pipe based Solar Thermal Facade Water Heating System, Energy Procedia 75 (2015) 566-57123
Zhang, H-F and Lavan, Z., Thermal performance of a serpentine absorber plate, Solar Energy Vol. 34, No. 2, pp 175-177, 1985
- Solar collector
- solar absorber
- single pass
- double pass
- flat panel
- heat transfer
- pressure drop
- pumping power