Heat flux and energy analysis of thermal bridge behaviour at wall and floor panel junctions in prefabricated cold storage systems: Experimental and numerical study

Abstract

Thermal bridges at panel junctions constitute a critical weakness in prefabricated cold storage systems, where localized heat transfer adversely affects energy efficiency, condensation control, and operational reliability. Although modular polyurethane sandwich panels are widely adopted, the thermal behaviour of junction geometries in cold storage environments remains insufficiently addressed in current standards. This study investigates thermal bridge formation and mitigation in prefabricated cold room panels, with particular emphasis on wall–wall, wall–ceiling, and wall–floor junctions. A combined experimental–numerical methodology is employed. Infrared thermography measurements performed on a cold storage test unit at an internal temperature of 273 K are used to validate high-resolution finite element models, achieving a numerical–experimental agreement of approximately 98%. The validated model is subsequently applied to six different joint configurations with identical material properties and boundary conditions, analysed under internal temperatures of 273 K and 255 K. Thermal performance is evaluated using temperature distributions, heat flux vector fields, and dimensionless parameters including normalised temperature and relative heat flux ratio (q∗[jls-end-space/]). While average surface temperatures across different joint geometries are found to vary within a narrow range around 285 K at 273 K internal conditions, the corresponding heat flux values exhibit pronounced differences. Reference flat and Z-type joints show the highest heat flux levels, reaching ∼[jls-end-space/]10 W/m2 at 273 K and ∼[jls-end-space/]13 W/m2 at 255 K, indicating strong thermal short-circuit behaviour. In contrast, stepped and interlocking joint configurations reduce the effective heat flux to below 8 W/m2 at 273 K and approximately 12 W/m2 at 255 K, accompanied by more homogeneous thermal fields. The results demonstrate that surface temperature alone is insufficient to characterize thermal bridge severity, whereas heat flux intensity and relative heat flux provide more sensitive and geometry-dependent performance indicators. The results indicate that thermal bridge mitigation in cold storage envelopes can be effectively enhanced through geometric optimization of panel joints, while maintaining identical panel thickness and material properties. Furthermore, the proposed heat-flux-based, dimensionless evaluation framework provides a physically grounded tool for comparative assessment of joint designs and may support future improvements in cold storage design practices.