An experimental and numerical simulation study of an active solar wall enhanced with phase change materials

Solar walls can be used to increase the overall energy efficiency of a building. Phase Change Materials (PCM) are capable of increasing the effective thermal mass of building elements, thus decreasing the overall energy consumption. Recently, the incorporation of PCM in a solar wall has been proposed, aiming to increase the total energy efficiency of the system. The main scope of this work is to investigate the thermal behaviour of a PCM-enhanced solar wall (PCMESW), using experimental and numerical simulation techniques. A prototype PCMESW is installed in a large-scale test facility and is exposed to dynamically changing climate conditions. A broad range of sensors, used to monitor the time-evolution of several important physical parameters, is employed to assess the dynamic response of the PCMESW. In addition, a Computational Fluid Dynamics tool is used to numerically investigate the thermal behaviour of the PCMESW prototype. Predictions of the developing flow- and thermal-field in the PCMESW’s air cavity are validated by means of comparison with the obtained measurements; in general, good levels of agreement are observed. Results of the numerical simulations may support the design optimization process of innovative PCMESW systems

Development and Parametric Evaluation of a Tabulated Chemistry Tool for the Simulation of n-Heptane Low-Temperature Oxidation and Autoignition Phenomena

Accurate modelling of preignition chemical phenomena requires a detailed description of the respective low-temperature oxidative reactions. Motivated by the need to simulate a diesel oil spray evaporation device operating in the “stabilized” cool flame regime, a “tabulated chemistry” tool is formulated and evaluated. The tool is constructed by performing a large number of kinetic simulations, using the perfectly stirred reactor assumption. n-Heptane is used as a surrogate fuel for diesel oil and a detailed n-heptane mechanism is utilized. Three independent parameters (temperature, fuel concentration, and residence time) are used, spanning both the low-temperature oxidation and the autoignition regimes. Simulation results for heat release rates, fuel consumption and stable or intermediate species production are used to assess the impact of the independent parameters on the system’s thermochemical behaviour. Results provide the physical and chemical insight needed to evaluate the performance of the tool when incorporated in a CFD code. Multidimensional thermochemical behaviour “maps” are created, demonstrating that cool flame activity is favoured under fuel-rich conditions and that cool flame temperature boundaries are extended with increasing fuel concentration or residence time