Effect of flow maldistribution on thermal performance of a solar air heater array with subcollectors in parallel

This paper presents results of a theoretical study carried out to investigate the effect of flow maldistribution, caused by the manufacturing imperfections and tolerances, on the thermal efficiency of a solar air heater array with subcollectors in parallel. The air mass flow rate, ambient temperature, solar insolation and wind heat transfer coefficient have been systematically varied to study the effect under a wide range of these parameters. The collector length, duct height, and plate emissivity were also changed to study their effect. It has been found that the maximum reduction in thermal efficiency due to flow maldistribution is less than about 3% for an array with a commercial grade finish of duct surfaces and ±10% manufacturing tolerance for the duct height.

[1]  H. Buchberg,et al.  Natural Convection in Enclosed Spaces—A Review of Application to Solar Energy Collection , 1974 .

[2]  R. Culham,et al.  The effects of unbalanced flow on the thermal performance of collector arrays , 1984 .

[3]  Rajendra Karwa,et al.  Thermo-hydraulic performance of a solar air heater with n-subcollectors in series and parallel configuration , 2002 .

[4]  W. Swinbank.  Long‐wave radiation from clear skies , 1963 .

[5]  E. Sparrow,et al.  Experiments on turbulent heat transfer in an asymmetrically heated rectangular duct , 1966 .

[6]  R. Shah,et al.  Handbook of single-phase convective heat transfer , 1987 .

[7]  S. Klein.  Calculation of Flat-Plate Collector Loss Coefficients , 1975, Renewable Energy.

[8]  Noam Lior,et al.  Flow distribution in manifolded solar collectors with negligible buoyancy effects , 1994 .

[9]  N. Lior,et al.  Optimal flow configuration in solar collector arrays , 1981 .

[10]  J. Whitelaw,et al.  Convective heat and mass transfer , 1966 .

[11]  Alan Quarmby,et al.  Further calculations on the heat transfer with turbulent flow between parallel plates , 1964 .

[12]  Y. Lee.  Turbulent heat transfer from the core tube in thermal entrance regions of concentric annuli , 1968 .

[13]  K. Hollands,et al.  Optimization of Flow Passage Geometry for Air-Heating, Plate-Type Solar Collectors , 1981 .

[14]  S. C. Solanki,et al.  Thermo-hydraulic performance of solar air heaters having integral chamfered rib roughness on absorber plates , 2001 .

[15]  W. Charters,et al.  An experimental investigation of forced-convective heat transfer for fully-developed turbulent flow in a rectangular duct with asymmetric heating , 1970 .

[16]  P. Niles,et al.  Design and performance of an air collector for industrial crop dehydration , 1976 .

[17]  Andreas Richter,et al.  Flow distribution in solar collectors with laminar flow conditions , 2002 .

[18]  Ho-Ming Yeh,et al.  Solar air heaters with two collectors in series , 1997 .

[19]  R. Shah,et al.  Compact Heat Exchangers , 1990 .

[20]  W. Rohsenow,et al.  Handbook of Heat Transfer , 1998 .

[21]  W. Kays,et al.  HEAT TRANSFER IN ANNULAR PASSAGES. SIMULTANEOUS DEVELOPMENT OF VELOCITY AND TEMPERATURE FIELDS IN LAMINAR FLOW , 1964 .

[22]  W. Kays,et al.  Heat transfer in annular passages—hydrodynamically developed turbulent flow with arbitrarily prescribed heat flux , 1963 .