Numerical and Experimental Study of Thermal Storage Energy in a Building with Various Pipeline Design under Floor—Case Study

This paper presents a comprehensive experimental and numerical investigation of radiant floor heating (RFH) systems integrated with phase change material (PCM)-based thermal energy storage (TES). The study compares two underfloor pipe configurations: double serpentine and spiral. It also looks at how well a paraffin wax PCM system works with compact heat exchanger-type TES units during winter in Iraq. Key performance indicators including discharge temperature, heat transfer rate, liquid fraction evolution, and temperature uniformity were assessed through in situ experimental measurements and ANSYS Fluent simulations. Results demonstrate that the spiral design provides slightly more uniform temperature distribution on the tile surface at an inlet water temperature of 55°C, with an average difference of approximately 0.5%, the serpentine layout exhibits higher slab temperature distribution by about 0.66%. Notably, the serpentine configuration shows superior thermal homogeneity and heat distribution, with a 15.05% increase in heat gain at a 55°C inlet temperature compared to the spiral design. The performance gap between the two layouts narrows as the inlet temperature increases from 50°C in 5°C increments by approximately 4.1%, 3.7%, and 1.7%, respectively. Higher inlet temperatures also improve PCM discharging and charging rates, improving energy storage utilization. The findings provide significant design guidelines for sustainable heating systems for cold climates.