Air-multiple PCMs for the free cooling and ventilation of buildings

• Main Author: de Carvalho Iten, Muriel
• Published: Coventry University 2015
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.743062

Thermal energy storage (TES) including phase change materials (PCMs), is an important technology to provide free cooling and ventilation in buildings. They have potential advantages over mechanical ventilation systems in terms of energy requirements, economic and environmental benefits. The main aim of this research is to study an air-multiple PCMs unit for the free cooling and ventilation applications relying on the daytime and night-time temperature difference during the summer. The research work carried out and reported in this thesis includes an extensive literature review on TES, incorporating PCMs, experimental investigation of the parameters influencing the charging and discharging time and the air outlet temperature of an air-PCM unit. It has been observed that the heating/cooling rate of PCM is important factor in studying charging/discharging behaviour of a PCM. For this, the determination of the thermophysical properties of the selected PCMs by Differential Scanning Calorimetry (DSC) is carried out. Similar heating rate, as per experimental testing, established better validation results when used in CFD model. The CFD model aims to predict the outlet air temperatures and the PCM temperatures for validation of the experimental data. Further on, parametric study will use the verified CFD model of an air-multiple PCM unit to identify significant parameters affecting the air outlet temperature, the cooling time and the PCM charging time. Finally, this thesis will investigate the potential of an air-multiple PCM unit for free cooling and ventilation of an office building under Portuguese climatic conditions through a CFD model. The experimental study has shown that the air inlet temperature and velocity play a major role on the PCM charging/discharging time and on the air outlet temperature. The numerical and experimental studies show that the developed CFD model has the ability to give good agreement for the prediction of the PCM charging and discharging times and the air outlet temperature with experimental results. Based on the experimental work and numerical analysis, an air-multiple PCM unit is proposed with a cooling load of 1.02 kW for office building. This allowed the reduction of the initial capital cost, the maintenance cost and the environmental benefits when compared to a traditional air conditioning unit.