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Composite Phase Change Materials

Mantec has undertaken a study grant funded through the BEIS, to address the issue of high energy use at peak power times ie when demand for electricity or gas from the grid is at its highest point.

The research has several domestic and commercial application but in this study we aimed at designing a baffle-type phase change heat storage electric heating device.

The device uses a number of materials (Graphite, nitrates and nitrides paraffin (PA) as the heat storage medium and encapsulates the composite phase change materials (CPCM) in a rectangular slab that is directly heated using an electric heating source.

To investigate the impact of the number and thickness of the rectangular plates on the thermal storage and exothermic performance of the device, we performed three-dimensional numerical simulations.

We then made performance and simulation test comparisons with the commonly used shell-and-tube and concentric tube types. In addition, the designed device was optimized by adding fines to the CPCMs using the orthogonal test method. To verify the heating effectiveness of the device, we simulated the temperature field, PMV (Predicted Mean Vote), and PPD (Predicted Percentage Dissatisfied) of the heating room to represent a household application.

Our investigation confirms continuous heat release of the device for 7 h during the day which meets home heating requirements. It is also shown that the heat storage and exothermic efficiency reach to 85.83% and 90.1%, respectively, after the device is optimized, the storage and exothermic efficiency increased by 8.15% and 6.43% respectively, and the real-time outlet temperature has increased by 4.98 °C compared with that before the optimization; the average indoor temperature of the heating room is 22.49 °C, PMV is 0.55, and PPD is 15.3% in line with the thermal comfort requirement guidelines.

The device can both heat and store heat at the same time when the power is low and during the peak period, grid power supply is turned off and the heating is directly supplied by CPCM.

Compared with direct electric heating systems used at peak times CPCMs can reduce users’ electricity costs significantly, resulting in a call for energy from the grid only at low peak times ie used at peak times or when energy level requirements are low which in turn, switches peak and valley time use resulting in significant cost saving on energy usage for a household.

The research Mantec undertook provides a reference for the design and optimization of heat storage devices and their application in practical engineering.

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