Numerical Investigation Of Heat Transfer Enhancement Characteristics In A Solar Air Heater With Multi V-shaped Ribs On The Absorber Plate

Solar energy is a kind of energy that is clean and renewable,and the efficient use of solar energy is an important measure for saving and reducing emissions,protecting the environment,resolving the energy crisis,and improving climate change.A solar air collector is a device that uses air as a heat collection medium to convert solar radiation energy into heat energy.Providing fins in the collector can enhance the heat exchange between the cold fluid and the hot fluid on the heat absorption plate.In the results of the current stage of research,multiple V-shaped ribs in the collector have a good heat transfer effect,but because the geometric parameters of the ribs in the collector affect the flow field in the channel,it may also affect the most Since the number of ribs in the width direction is preferable,the number of ribs in the channel width direction needs to be selected when multiple V-shaped ribs are used.However,there is no report on the effect of the rib geometric parameters on the optimal number of ribs in the collector width direction.The model was meshed ?grid quality test and grid independence test by the ICEM software.Fluent software was adopted for numerical simulation calculation.We study the effect of the rib pitch,rib height,rib angle of attack and the number of V-shaped ribs in the channel width direction on average Nu number,frictional factor,and thermal performance factor under the condition that the channel width,rib thickness and Re were constant.According to the analysis of numerical simulation results,the average Nu number,frictional factor and thermal performance factor of the solar air collectors increase first and then decrease with the increase of the number of fins,and there is a maximum value.With the rib angle increases,the maximum value of the thermal performance factor of the collector continues to decrease,and the optimal number of ribs corresponding to the maximum thermal performance factor also decreases.With the rib pitch increases,the maximum value of the thermal performance factor of the collector first increases and then decreases,and the optimal number of fins corresponding to the maximum thermal performance factor also gradually decreases.With the rib height increases,the maximum value of the thermal performance factor of the collector first increases and then decreases,and the optimal number of fins corresponding to the maximum thermal performance factor first increases and then decreases.the maximum thermal performance factor first increases and then decreases.When the geometric parameters of the rib angle,pitch,height are changed,The factors affecting the thermal performance factors such as the strength and pitch of main vortex which is generated in the channel of the solar air collector,and length of thermal boundary layer between adjacent ribs.because the thermal performance factor is also affected by the number of ribs.Therefore,with the change of the rib angle,pitch,and rib height are changed,optimal number of ribs corresponding to the maximum thermal performance factor also changes.