Cement composites with expanded graphite/paraffin as storage heater

The following paper presents the results of research on cement composites with expanded graphite/-paraffin in terms of their application in accumulative heating systems. A novel approach, using expanded graphite simultaneously as an electric conductive and as a phase-change additive, is presented. A complex additive was prepared by means of the impregnation of expanded graphite (EG) with paraffin through porous grains. The EG/paraffin grains were added to cement composites in a ratio of 10-30 wt % of cement. The surface temperature of the composites with EG/paraffin during self-heating was measured to evaluate their heat generation capability. Changes in the surface temperature of the sample and the air temperature in the heat chamber compared to the reference sample were measured during self-heating and cooling to determine thermal storage capability. Thermal and mechanical reliability after 50 cycles of accelerated heating was investigated. The results show that cement composites with EG/paraffin are able to generate high power (even 25.7 kW/m(2)) and possess high heating rate, enabling their use with voltages as low as 10 V. These composites are also capable of maintaining a desirable air temperature in heat chamber for a longer period of time. The air temperature in the heat chamber during the cooling process of the composite with EG/paraffin was about 1.0 degrees C higher than the reference sample after 50 min. Moreover, these composites are characterized by thermal and mechanical reliability. The results revealed that the cement composites with EG/paraffin could be effectively used in accumulative surface heating systems. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study focused on the use of expanded graphite/paraffin as composite additives in cement composites for accumulative heating systems. The results demonstrated high power generation, heating rate, and thermal-mechanical reliability, making them suitable for low voltage applications and maintaining stable temperatures.