Enhanced thermal stability of novel helical-finned jacketed stirred tank heater

Abstract

A novel helical finned jacketed (HFJ) stirred tank heater is proposed as a variant of the conventional half-pipe jacketed (HPJ) system for achieving enhanced thermal stability through increased heat transfer area. The HFJ configuration comprises of helical grooves around the vessel, with pitch equal to that of HPJ, that leaves helical fin as a partition between the parallel flow sections.This results in an increase in effective heat transfer area by 2.14 times for equal jacket flow cross-sectional area. The operation of a three-turn HFJ assembly is compared against its HPJ counterpart under different steam flow conditions 1535⩽Re⩽8132 through: (i) a detailed CFD analysis of flow and heat transfer on the jacket side and (ii) linearized state-space model based stability analysis. CFD analysis predicts ~1.98–2.08 times higher rate of heat transfer and ~36% higher estimates of overall heat transfer coefficient, establishing the efficacy of HFJ over HPJ. Estimates of τ based on effective surface area show comparatively lower values for HFJ (~1/4 times), that decrease with increasing Re, implying a faster response behaviour at higher flow rates. The latter is corroborated through a pole analysis which shows a consistent negative shift in poles on the real axis with increasing Re. Finally, the response characteristics for typical step-input on the jacket side reveal a reduced static gain by 50% for HFJ, establishing a lower inherent sensitivity of system hardware to fluctuations in jacket and greater amenability to control strategies.