Heat transfer investigation of PCM pipe bank thermal storage for space heating application

Abstract

Space heating is a major issue in the various cold regions in the world where energy sources are inadequate and unreliable. This study reports an investigation of the heat transfer characteristics of a pipe-bank thermal storage system for space heating applications with sodium acetate trihydrate as a phase change material. The system is engineered for cost-effectiveness, facility of manufacture, and ease of end-use. Temporal measurements of temperatures combined with a simple heat transfer model are used to calculate heat transfer coefficients within the PCM pipes as well as between the pipe skin and air. Effects of variation in inlet air temperatures and inlet air velocities are reported. The heat transfer coefficient between the pipe-skin and air bears a surprisingly simple relationship to velocity as hp=19,400v3.1 (SI units). The developed device gives a total heat release of 0.56 MJ, i.e., 15.8 MJ/m3 of the device. The current system's shortcomings are discussed, and supercooling is identified as the major cause of poor heat release. In the absence of supercooling, the device has the potential to store 79 MJ/m3, and its potential to replace the “Bukhari” braziers for space heating applications is quantitatively investigated.