0
Research Papers: Thermal Systems

Improved Model for Calculating Instantaneous Efficiency of Flat-Plate Solar Thermal Collector

[+] Author and Article Information
Oussama Ibrahim

Faculty of Engineering,
Lebanese University,
Hadath 1003, Lebanon
e-mail: oibrahimul@hotmail.com

Farouk Fardoun

Department GIM,
University Institute of Technology,
Lebanese University,
Saida 1600, Lebanon
e-mail: ffardoun@ul.edu.lb

Rafic Younes

Faculty of Engineering,
Lebanese University,
Hadath 1003, Lebanon
e-mail: ryounes@ul.edu.lb

Mohamad Ibrahim

Universite Grenoble Alpes, INES,
Grenoble F-38000, France;
Department of Solar Technologies,
CEA, LITEN,
INES,
Le Bourget du Lac F-73375, France
e-mail: mohamad.ibrahim@cea.fr

Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received February 7, 2017; final manuscript received November 7, 2017; published online February 27, 2018. Assoc. Editor: Ali Khounsary.

J. Heat Transfer 140(6), 062801 (Feb 27, 2018) (8 pages) Paper No: HT-17-1067; doi: 10.1115/1.4038827 History: Received February 07, 2017; Revised November 07, 2017

The performance of a flat-plate solar collector is usually assessed by its efficiency. This efficiency is normally defined on a steady-state basis, which makes it difficult to correctly track the instantaneous performance of the collector in various case-studies. Accordingly, this paper proposes an improved definition of instantaneous efficiency of a flat-plate solar collector used as a part of a solar water heating system. Using a predeveloped model by the authors for such a system, the proposed efficiency-definition is examined and compared with the conventional one for specific case studies. The results show that the improved definition of efficiency records reasonable values, i.e., no over-range values are observed contrast to the case of conventional efficiency-definition. Furthermore, this suggested efficiency approximately coincides with the conventional one at a wide range of time, as long as the system is operating in the so-called trans-steady-state phase or when the system is off-operational provided that the instantaneous rate of heat stored in the heat transfer fluid (HTF) is less than or equal to zero. As a result, the improved efficiency-definition yields more realistic results in reflecting the performance of a flat-plate collector in an active solar water heating system and is recommended to be used.

FIGURES IN THIS ARTICLE
<>
Copyright © 2018 by ASME
Your Session has timed out. Please sign back in to continue.

References

ASHRAE, 2003, “Methods of Testing to Determine the Thermal Performance of Solar Collectors,” American Society of Heating, Refrigerating, and Air Conditioning Engineers, Atlanta, GA, Standard No. ASHRAE 93.
AENOR, 2006, “Sistemas Solares Térmicos y Components, Captadores Solares,” The Spanish Association for Standardization and Certification, Madrid, Spain, Standard No. UNE: EN 12975.
Rodríguez-Hidalgo, M. C. , Rodríguez-Aumente, P. A. , Lecuona, A. , and Nogueira, J. , 2012, “ Instantaneous Performance of Solar Collectors for Domestic Hot Water, Heating and Cooling Applications,” Energy Build., 45, pp. 152–160. [CrossRef]
Tagliafico, L. A. , Scarpa, F. , and De Rosa, M. , 2014, “ Dynamic Thermal Models and CFD Analysis for Flat-Plate Thermal Solar Collectors—A Review,” Renewable Sustainable Energy Rev., 30, pp. 526–537. [CrossRef]
Shan, F. , Tang, F. , Cao, L. , and Fang, G. , 2014, “ Dynamic Characteristics Modeling of a Hybrid Photovoltaic–Thermal Solar Collector With Active Cooling in Buildings,” Energy Build., 78, pp. 215–221. [CrossRef]
Hamed, M. , Fellah, A. , and Ben Brahim, A. , 2014, “ Parametric Sensitivity Studies on the Performance of a Flat Plate Solar Collector in Transient Behavior,” Energy Convers. Manage., 78, pp. 938–947. [CrossRef]
Muschaweck, J. , and Spirkl, W. , 1993, “ Dynamic Solar Collector Performance Testing,” Sol. Energy Mater. Sol. Cells, 30(2), pp. 95–105. [CrossRef]
Hilmer, F. , Vajen, K. , Ratka, A. , Ackermann, H. , Fuhs, W. , and Melsheimer, O. , 1999, “ Numerical Solution and Validation of a Dynamic Model of Solar Collector Working With Varying Fluid Flow Rate,” Sol. Energy, 65(5), pp. 305–321. [CrossRef]
Villar, N. M. , Lòpez, J. M. C. , Muñoz, F. D. , Garcìa, E. R. , and Andreas, A. C. , 2009, “ Numerical 3-D Heat Flux Simulations on Flat Plate Solar Collectors,” Sol. Energy, 83(7), pp. 1086–1092. [CrossRef]
Cadfalch, J. , 2009, “ A Detailed Numerical Model for Flat-Plate Solar Thermal Devices,” Sol. Energy, 83(12), pp. 2157–2164. [CrossRef]
Martinopoulos, G. , Missirlis, D. , Tsilingiridis, G. , Yakinthos, K. , and Kyriakis, N. , 2010, “ CFD Modeling of a Polymer Solar Collector,” Renewable Energy, 35(7), pp. 1499–1508. [CrossRef]
Dovic, D. , and Andrassy, M. , 2012, “ Numerically Assisted Analysis of Flat and Corrugated Plate Solar Collectors Thermal Performances,” Sol. Energy, 86(9), pp. 2416–3431. [CrossRef]
Kessentini, H. , Castro, J. , Capdevila, R. , and Oliva, A. , 2014, “ Development of Flat Plate Collector With Plastic Transparent Insulation and Low-Cost Overheating Protection System,” Appl. Energy, 133, pp. 206–223. [CrossRef]
Cerón, J. F. , Pérez-García, J. , Solano, J. P. , García, A. , and Herrero-Martín, R. , 2015, “ A Coupled Numerical Model for Tube-on-Sheet Flat-Plate Solar Liquid Collectors. Analysis and Validation of the Heat Transfer Mechanisms,” Appl. Energy, 140, pp. 275–287. [CrossRef]
Oliva, A. , Costa, M. , and Segarra, C. D. , 1991, “ Numerical Simulation of Solar Collectors: The Effect of Nonuniform and Nonsteady State the Boundary Conditions,” Sol. Energy, 47(5), pp. 359–373. [CrossRef]
Cristofari, C. , Notton, G. , Poggi, P. , and Louche, A. , 2002, “ Modelling and Performance of a Copolymer Solar Water Heating Collector,” Sol. Energy, 72(2), pp. 99–112. [CrossRef]
Al Imam, M. F. I. , Beg, R. A. , Rahman, M. S. , and Khan, M. Z. H. , 2016, “ Performance of PVT Solar Collector With Compound Parabolic Concentrator and Phase Change Materials,” Energy Build., 113, pp. 139–144. [CrossRef]
Meteonorm, 2014, “Global Meteorological Database,” Version 7, METEOTEST AG, Bern, Switzerland/Swiss Federal Office of Energy, Bern, Switzerland.
Ibrahim, O. , Fardoun, F. , Younes, R. , and Gualous, H. L. , 2014, “ Optimal Management Proposal for Hybrid Water Heating System,” Energy Build., 75, pp. 342–357. [CrossRef]

Figures

Grahic Jump Location
Fig. 1

Schema of an active solar water heating system employing a flat plat collector

Grahic Jump Location
Fig. 2

Cross section of the flat-plate solar collector

Grahic Jump Location
Fig. 3

Min-values of ambient temperature, wind speed, and solar radiation for June 21 and December 21 in Beirut, Lebanon

Grahic Jump Location
Fig. 4

Hourly hot water consumption profile for a family of four persons during summer and winter days in Lebanon

Grahic Jump Location
Fig. 5

Discretization scheme of a single tube of the flat-plate solar collector

Grahic Jump Location
Fig. 6

Variations with respect to time on June 21 of (a) instantaneous conventional efficiency, (b) temperatures of side-plate, center-plate, tube-wall, HTF and ambient, (c) rate of heat stored in side-plate, center-plate, tube-wall and HTF, and (d) zoom in figure (c)

Grahic Jump Location
Fig. 7

Schematic of energy flows in the studied flat-plate solar collector

Grahic Jump Location
Fig. 8

Variation of the improved efficiency with respect to time on June 21

Grahic Jump Location
Fig. 9

Variation of improved and conventional instantaneous efficiencies with respect to time (a) on June 21; (b) in interval I; (c) in interval II; (d) at beginning of interval VI

Grahic Jump Location
Fig. 10

Variation of the difference between improved and conventional instantaneous efficiencies with respect to time on June 21

Grahic Jump Location
Fig. 11

Variation of improved and conventional instantaneous efficiencies with respect to time on December 21

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In