Investigation of Heat Exchangers for a Solar Domestic Hot Water System

Abstract

This study evaluates the hydraulic and thermal performance of three heat exchangers used in hot water solar systems: shell and tube, shell and twisted tube, and brazed plate. The shell and tube heat exchanger is provided by Thermo Dynamics Ltd., while the brazed plate (type M14A) and shell and twisted tube (type PL45) models are supplied by SEC Ltd. SEC Ltd.'s data for the Brazed Plate and Shell and Twisted Tube heat exchangers are intended for high-power applications of 12 kW and above, however, this study investigates their performance at lower power levels, up to 3 kW. In addition to these three heat exchangers, the study also includes a comparative analysis with a shell and coil heat exchanger, as studied by (Gharbia, 2010). In the experimental setup, a 40% propylene glycol solution is circulated through one side of each heat exchanger, with water flowing through the other due to buoyancy-induced flow. The heat exchangers vary in surface area: Shell and Tube (0.36 m²), Shell and Twisted Tube (0.15 m²), Brazed Plate (0.14 m²). The study indicates that the brazed plate heat exchanger has superior thermal performance compared to both the shell and twisted tube as well as shell and tube configurations. However, it exhibits lower performance in comparison to the shell and 4-coils heat exchanger, which is currently used by Thermo Dynamics Ltd. for hot water solar systems.