Analysis of the Thermal Performance of Isothermal Composite Heat Accumulators Containing Organic Phase-Change Material

Abstract

This paper presents the results of material tests, experimental tests and statistical analysis of the thermal performance of three types of heat accumulators containing an organic phase-change material and two materials of a higher thermal conductivity: a copper mesh and porous coke recyclate. The aim of the research was to empirically and statistically compare the increase in the PCM heat distribution through a copper conductor and coke recyclate. The research was conducted in accordance with an incomplete central compositional experimental design and using the Statistica software. The studies of the structure and chemical composition of the coke recyclate used and the empirical testing of the finished heat accumulators confirmed an improvement in the distribution and storage of heat by the accumulator with the phase-change material and coke recyclate compared to the pure phase-change material and copper-conductor accumulators, as the holding time of a temperature of 20 °C was extended by seven minutes and nine minutes, respectively. Moreover, the results of the statistical analysis provided answers as to which of the assumed input quantities—initial temperature, battery geometry, and heating temperature—were statistically significant for each of the three battery types considered. The determined approximating functions were verified in terms of the statistical validity of their use for all three types of heat accumulators tested. The results obtained are important answers to the current problems in the design and modification of phase-change heat accumulators applied in the construction industry to reduce the emissivity of structures and increase their energy efficiency.