An assessment of radiation models utilized in CFD for thermal and fluid analysis in interior building spaces with large glazing

Abstract

This paper investigates the effects of using the S2S and the DO method in the CFD simulation of a cavity to identify a convenient model for simulating radiative heat transfer. A 3D model for an office room fitted with a sizeable controllable glass window was developed to carry out a transient analysis of a room's thermal performance when the glass is at its opaque state while accounting for each of the models. A transient user-defined function (UDF) boundary condition, based on radiative heat flux, was set as an incident solar load boundary condition on the dynamic glazing to study the dispersed temperature and the airflow in the room. Various configurations of the enclosed room with initial wall boundary condition and airflow in the room were considered under the effects of different parameters such as thermal properties, Rayleigh (Ra) and Grashof (Gr) numbers, surface emissivity, and absorption. Radiative CFD results were compared, and the importance of accounting for radiation was noted. The S2S displayed good performance, whereas unexpected temperature distribution was observed with the DO method. Although heat transfer depends on the transmitting material's thermal properties, further analysis has shown that the S2S, along with the SST k-ꞷ viscous turbulence model, using piecewise linear approximation, is a reliable CFD model setting for performing a thermal analysis of a highly glazed enclosed room. The results were also compared to a previous 2D analysis of an enclosed space without accounting for radiation. Results had shown that the interior temperature was less than 2% for the S2S when radiation was overlooked. Further study would involve the validation of the computed room temperature with experimental data which will show the efficiency of the two radiation model methods in performing the thermal performance of a building.