Study On Heat Transfer Performance Of Flat-plate Solar Collector Integrated With Micropore Surface

Solar energy is considered as one of the most promising green energy for its advantages such as pollution-free and economic,and is considered to have great potential in adaptability to renewable energy building integration.Using solar water heater to produce hot water is widely applied in green buildings.Flat-plate solar collector for solar collection is common in many countries.However,the low conductivity of pure water leads to poor heat transfer performance in collector.In order to enhance heat transfer in collector,a flat-plate solar collector using Vshape plate as absorber and metal foams as filler is presented.For the V-shape absorbing plate,Ni-Al₂O₃ coating with micropore structure is applied.And there is no heat water tank,which saves installation space.By analyzing the mechanism of selective absorptivity of the surface with micropore and combining the basic principle of solar radiation,the theoretical calculation model of the energy yield of V-shape absorbing plate is established.The relationship of energy yield of V-shape absorbing plate with V-shape inclination,installation inclination and installation orientation at different latitudes are analyzed.Compared with traditional absorber,the most annual energy yield is obtained with V-shape inclination at 45°.If the collector is installed on the roof,it shall be installed facing south.Suggestted installation angle is close to latitude within ±5° If the collector is installed on the wall,it shall be installed facing south.Suggestted installation angle is 75°.The theoretical calculation model of energy yield of V-shape absorbing plate provides data for the numerical simulation of heat transfer of collector.A numerical model was proposed to describe the heating process of flat-plate solar collector with metal-foam filler.Local-thermal-equilibrium model was applied.The fluid was considered as Newtonian fluids and under Boussinesq approximation.The flow was laminar,following Darcy's law and the viscous dissipation of fluid is ignored.The impact of metal-foam filler of different structural parameters,with porosity in the range of 0.8991-0.9546 and PPI?pores per inch?of 5,10 and 20,are discussed.The application of metal foam filler inside the flat plate collector influenced the heat transfer in tube greatly.The solar collector with metal foams gains higher water temperature.The structural parameters of porosity and PPI have impact on the performance of vacuum tube solar collector.With porosities in the range of 0.8991-0.9546 and PPI of 5,10 and 20,the porosity at about 0.9 is recommended to apply to the design of solar collector.A flat-plate solar collector using water as medium and metal foams as filler is designed and fabricated.The test platform of V-shape absorbing plate solar collector is established.Experiment of the heating process of solar collector is conducted.The experiment results are in good agreement with the simulation.Outdoor efficiency test is conducted The instantaneous efficiency curve measured by the outdoor efficiency test is?=-3.99T^*_i + 0.682 .