C22 -- Operational Characteristics and Performance of Trombe Wall-Design Instructions: A Parametric Study PDF

The use of the Trombe wall as a passive heating element concerns the engineers from the initial stages of the design of a building. So, there is a need for a fast and user-friendly tool in early stages of design to estimate the thermal gains offered by a Trombe wall without having to use specialized software or to develop coding skills. Such a kind of explicit model, which can be materialized in a spreadsheet, it has been developed by the authors of this article. However, this model requires information the air mass flow inside the air-gap and the heat transfer coefficients and for this reason, the authors have developed an implicit energy balance model that calculates these values. In the present work, the energy balance model is initially used to determine the air mass flow inside the air-gap and the heat transfer coefficients during representative days of the heating season accounting the heat storage. With this model, tables with values of operational characteristics are produced, feeding the explicit model and producing the annual thermal gains that the examined Trombe walls can offer. Combining these two models in a unique tool, a very wide parametric study is performed concerning: a) 4 values for the gap width, b) 4 values of Trombe wall thickness, c) 5 values of the distance between the ventilation holes, d) 3 storage wall materials, e) 3 transparent cover materials and f) 4 different climatic regimes. The results of the parametric study yield: (a) adatabase for the air mass-flow rate inside the air-gap in a naturally ventilated Trombe wall as well as the heat transfer coefficients; (b) conclusions on how the design options under consideration affect the important Trombe wall’s operating characteristics; and c) instructions for the optimal Trombe wall design with the climatic conditions under consideration.