Heat transfer characteristics of phase change materials in double-layer packed bed under dynamic thermal boundary

Abstract

Dynamic thermal boundary conditions have a significant impact on the thermal storage performance of phase change materials (PCMs) in packed beds. In this paper, an unsteady numerical heat transfer model of a double-layer packed bed is established and verified. The heat storage characteristics of the four PCM combination schemes are calculated and compared, and the sinusoidal wave heat source is used as an input parameter to study the influence of wave amplitude and period changes on the thermal performance of the system. The study shows that when the volume ratio of PCM 1 to PCM 2 is 1/3:2/3, the melting time is shorter and the heat storage rate is faster. The long-period fluctuation can significantly shorten the melting time and improve thermal performance. When the period is 120 min, the melting time is shortened by about 15.2 % compared with the steady state, and the heat storage rate is increased by 19.6 %. The larger the amplitude of the heat source, the stronger the promotion effect on melting. When the amplitude is 16 °C, the melting time is shortened by about 17.7 % compared with the steady state, and the heat storage rate is increased by 16.7 %. The research results can provide some reference for the design of a double-layer packed bed under the dynamic heat source.