Abstract
In order to achieve the numerical model of a transpired solar collector (TSC) with integrated phase changing materials (PCM) it is mandatory to study the impact of the orifice geometry on the entire system. The numerical simulation of the entire solar collector absorber metal plate (1000x2000mm and 5000 orifices) is not feasible thus resulting a huge number of cells for the numerical grid for which we will need very high computational resources and a very large amount of time to be solved. By taking these aspects into account we decided to simulate only four equivalent orifices and then to transpose the results to the actual case for further studies. The present paper aims to analyse the mesh independency study for an elementary perforated panel with four equivalent lobed orifices which is part of a real case TSC. This analysis represents one of the most important stages within the construction of the TSC numerical model and doesn't need an experimental validation. The study was conducted in Ansys Fluent CFD software and the results were processed directly by using Tecplot software. Six different meshes were analysed (from 0.2 to 7.3 million cells), boundary conditions were imposed, and k-ε RNG turbulence model was used according to the literature. After comparing velocity and temperature fields in longitudinal and transverse planes we concluded that from 5.3 million cells the solution is independent of the meshing quality.
Highlights
1.1 ObjectiveRegardless of their type, the operating principle of air solar collectors is the same [1]
In the case of an opaque solar collectors, the heat is usually captured by a planar metal panel or a black perforated panel, it is released to the air which is collected at the top of the solar collector and introduced into the room by a fan
In order to be able to perform the numerical modelling of the solar collector with lobed perforations and integrated phase changing materials (PCM) in a feasible period of time, we have simplified as much as possible the geometry of the absorber plate that is part of the solar collector, starting from the premise of the thermal transfer phenomena symmetry and velocity fields symmetry
Summary
Regardless of their type, the operating principle of air solar collectors is the same [1]. Solar radiation is captured by an absorbent element (generally a metal plate) that transfers the heat to the airflow within the collectors’ air cavity. In the case of an opaque solar collectors, the heat is usually captured by a planar metal panel (absorber) or a black perforated panel, it is released to the air which is collected at the top of the solar collector and introduced into the room by a fan (in winter or during transition periods). Transpired solar collectors (TSCs) typically have a lower investment costs and high efficiency in the case of heating systems, fresh air preheating systems or drying systems [2] and they have lower lifetime costs [3]. Opaque solar collectors are typically used for applications where the required temperature is lower [4] and side winds are not very strong [5]
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