Experimental investigation of PCMs for the hot side of a vapour compression heat pump to adjust tariff rates

摘要

An experimental energy storage system has been designed and tested using a longitudinally finned inner tube and an outer shell heat exchanger incorporating a paraffin wax phase change material (PCM) with a melting point of 60 °C. This research forms part of a wider study of investigating the suitability of employing a phase change material (paraffin wax) to take advantage of off-peak electricity tariff. The system consisted of a 98 kg paraffin wax filling the shell side of the system, a PID controlled water heater to supply heat to the PCM and a wet radiator to discharge heat stored to the ambient. The results presented provide the thermal response in the longitudinally finned PCM and the heat transfer characteristics using isotherm plot and temperature time curves during charging and discharging of heat energy from the PCM. Using the experimentally measured data, the quantitative amounts of energy charged and discharged through a wet radiator as well as the heat transfer coefficients have been reported. Final isotherm plot indicated uneven heat distribution with upper section recording higher temperatures fuelled by the effect of buoyancy. The charge and discharge rates averaged 0.6 and 0.2 kW respectively prompting the need for a more efficient heat transfer technique to improve charge and discharge rates.