A comparative study of specific heat extraction rate and absorption for distinct hydride bed configurations under homogeneous conditions

Abstract

The current study examines the absorption performance of the embedded cooling tubes (ECT) and helically coiled tubes (HCT) reactor geometries by keeping the contact surface area and heat exchanger volume identical to determine the bettered bed configuration based on specific heat extraction rate (SHER) and 90 % saturation time. The ECT (comprising sixty straight tubes) and HCT (comprising three helical tubes) of the same diameter (4.75 mm), heat exchange volume (90477 mm³), and contact surface area with the hydride (45245 mm³) are subjected to variations in supply pressure (5, 15, 25 bar), water inlet temperature (278, 288, 298 K), and flow rate (0.1, 0.5, 0.9 kg/s). The HCT reactor demonstrated superior performance to the ECT reactor concerning hydrogen supply pressure, reducing absorption time by 1.5 to 1.6 times. Variations in water inlet temperature resulted in HCT highlighting 34–38 % faster absorption than ECT for an equivalent quantity of hydrogen absorbed. The mass flow rate indicated that absorption was, on average, 30 % faster for HCT compared to ECT. In conclusion, it was observed that the SHER of HCT is nearly double that of ECT across all operating conditions, thus emphasizing the beneficial aspect of utilizing helically coiled tubes.