Numerical Parametric Study of Ventilated Shading Plates Energy Performance in Summer
Date Issued
2012
Date
2012
Author(s)
Yeh, Meng-Ying
Abstract
The use of Ventilated Shading Plates or Ventilated wall systems to improve the thermal insulation of vertical walls in buildings has increased in recent years. However, most research on the energy performance of such Ventilated wall has been case studies. Due to the lack of literature reporting the energy performance correlations as functions of numerous parameters, it is difficult to compare the energy performance of Ventilated wall under different sets of parameters. There has been also relatively little research about the influence of radiation emssivity of flow channel surface. The purpose of this study was to investigate the parameters affecting the energy performance of Ventilated Shading Plates by numerical simulation and to provide a general energy performance correlations as functions of numerous parameters. These correlations permit a simple way to compare the energy performance of Ventilated Shading Plate. The simulations were conducted using commercial CFD code, FLUENT. Simulation results were compared with experimental data to validate the simulation model. Results of this study showed that thermal insulaton of Ventilated Shading Plate is increased sensibly as the radiation emssivity of flow channel surface decreased. The heat gain will not change much as the flow channel width increased to a certain extent. The influence of climatic condition on the equivalent thermal resistance of Ventilated Shading Plate was also investigated. We proposed a equivalent thermal resistance correlation with smaller error by the aid of thermal resistance network concept. Then general correlations was proposed by adding more parameters. The presented equivalent thermal resistance correlation and heat gain correlation can be used to estimate the thermal energy performance of Ventilated Shading Plate whose height and width are 3m and greater than 0.1m respectively. The general correlations are functions of absorpted solar radiation Ia, temperature difference between indoor and outdoor ΔT, effective emissivity of flow channel surface ε_eff, and thermal resistance of vertical wall Rw. The sensitivity analysis of heat gain against Ia and ΔT showed that decreasing effective emissivity of flow channel surface ε_eff is a more appropriate strategy in areas with relatively strong solar radiation. It also showed that increasing thermal resistance of vertical wall Rw is a more appropriate strategy in areas with relatively high outdoor temperature. The dynamic simulation results applying equivalent thermal resistance were in good agreement with the results from direct CFD simulations for different climate conditions and different Rw, ε_eff. Therefore, the general equivalent thermal resistance correlation can be used to reduce the computation time of dynamic simulations.
Subjects
Ventilated shading plate
External vertical wall
Numerical simulation
Natural convection
Equivalent thermal resistance
general correlations
Type
thesis
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