Correlating the thermal contact resistance between metal/erythritol interfaces with surface roughness and contact pressure

The thermal contact resistance (TCR) between the interfaces of phase change materials (PCMs) and their encapsulation materials, usually thin-walled metals, have a great impact on the heat storage/retrieval rates of PCM-based latent heat storage (LHS) systems. However, the TCR data beteween metal/PCM interfaces are rarely reported in the literature. In this work, an improved self-designed steady-state apparatus was adopted to measure the TCR between the interfaces of erythritol, a cost-effective sugar alcohol with great potential for medium-temperature LHS, and multiple metals including SS304, nickel silver (a copper-nickel-zinc ternary alloy), and 1060 Al. The metal/erythritol composites were prepared by naturally solidifying molten erythritol on the surface of thin metal plates. The variation of the TCR between metal/erythritol interfaces was measured as a function of the surface roughness (of the metal plates) and the contact pressure applied (between the interfaces). With the decrease of surface roughness, the TCR also decreases due to the better contact between the interfaces as observed by a microscope. Comparing to SS304 and nickel silver, the 1060 Al/erythritol composites exhibit a significant reduction of TCR by similar to 40% when rising the contact pressure from 0 MPa to 7 MPa, for all surface roughness levels tested. The in situ measured sample thickness variations confirmed that upon pressurization, the softer metal, i.e., 1060 Al, experiences more micro-deformation at the interface. In addition, correlations of the TCR data between metal/erthyritol interfaces were proposed with the surface roughness and contact pressure. The results and correlations attained in this work could serve as a reference for the thermal design of LHS units using erythritol. (C) 2021 Elsevier Ltd. All rights reserved.