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Experimental P erformance of U nglazed T ranspired S olar C ollector for A ir H eating

Experimental P erformance of U nglazed T ranspired S olar C ollector for A ir H eating. Hoy-Yen Chan Supervisors: Prof. Saffa Riffat and Dr. Jie Zhu Department of Architecture and Built Environment University of Nottingham, UK. Background .

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Experimental P erformance of U nglazed T ranspired S olar C ollector for A ir H eating

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  1. Experimental Performance of Unglazed Transpired Solar Collector for Air Heating Hoy-Yen Chan Supervisors: Prof. SaffaRiffat and Dr. Jie Zhu Department of Architecture and Built Environment University of Nottingham, UK

  2. Background • Space heating: major energy consumption in cold countries. • UK: 50% of the service sector energy consumption • More heaters to satisfy thermal comfort • Higher energy demand • More power stations • More CO2 emissions • Therefore, renewable energy has become vital energy sources for heating and cooling; e.g. solar energy

  3. Introduction: the concept Fan Warm air Solar radiation Fan Room Ambient air Transpired metal plate Insulated wall Forced into cavity by fan Convection heat loss

  4. Research problems Transpired plate heat transfer correlation (Nu) since 1980s (Jet impingement cooling) Ratio of pitch/diameter: small Not suitable for solar collector Transpired plate heat transfer correlation (Nu) for solar collector (Experimentally and modelling) Effects: hole designs /geometry, porosity, thickness, wind Tout Fan Normal flow Sandtile wall Plate height <1.0m Vertical flow: NO heat transfer Acknowledge heat transfer might occur Vertical flow Ta Vertical flow heat transfer Height= 3.0-6.0m Effect of plenum depth Heat transfer from back-of-plate could take place Simulation results based on CFD without experimental verification Ti Present study: Height= 2.0m No wind condition Vertical flow heat transfer & thermal performance Tp

  5. Results: vertical flow • Vertical flow contributes 40-50% of total temperature rise (3-10K) • Modified Nusselt numbers: Normal flow: Nu=0.004Re1.33 , 260 Re 470 Vertical flow: Nuf,L= 0.182Ref1.25 , 1100< Ref < 2000 (laminar) Nuf,T= 0.0026Ref1.7 , Ref 2300 (turbulent)

  6. Thermal performance: Temperature rise Vs. Solar radiation Tout Fan Sandtile wall Ta Ti Tp

  7. Thermal performance: Temperature rise Vs. Mass flow rate Tout Fan Sandtile wall Ta Ti Tp

  8. Thermal performance: Efficiency & Heat exchange effectiveness Tout Fan Sandtile wall Ta Ti Efficiency= mcp(Tout-Ta)/AI x 100% Heat exchange effectiveness= (Tout-Ta)/(Tp-Ta) x 100% Tp

  9. Conclusions • Vertical flow heat transfer is inappropriate to be neglected • Thermal performance increases with solar radiation but decreases with suction flow rate

  10. Conclusions- cont. Benefits: • Building integrated • CO2 emissions reduction not only helps to meet the international building emission targets but also createsmore green energy construction jobs • Suitable for building retrofit applications due to the system simplicity • High efficiency of the system enable colours other than black can be used to better fit into the architectural plan of the buildings • Low cost material. Metal material used in this design • i.e. aluminium sheet cost only about 15£/m2compare to the glazing material for most of the existing passive solar technologies which costs about 33£/m2 • It is a maintenance free solution • The transpired collector has porosity less than 1%. The actual air velocity in the holes is several meters per second which is high enough to keep dust from the building in the holes. • Due to the small hole size (1.2mm) and low porosity, only little rainwater can get through the holes. • The transpired metal plate is durable and can be easily to re-spray paint.

  11. THANK YOU Department of Architecture & Built Environment, University of Nottingham Email: laxhyc@nottingham.ac.uk

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