Second law analysis of a transient hexagonal cavity with a rotating modulator

Abstract

PurposeThe main focus of this article is on analyzing the entropy generation characteristics of an air-filled hexagonal thermo-fluid system with an adiabatic clockwise rotating dynamic modulator through second law analysis. This modulator rotation creates striations that affect natural convection. This convection is generated by the thermal stratification between the top and bottom walls. To fully analyze the system, the study considers both conduction and convection heat transfer by introducing a uniformly thick top wall. Overall, the study looks at the behavior of a conjugate thermo-fluid system. ApproachThe system is solved numerically using non-dimensional Navier Stokes equations as a moving mesh problem by the Arbitrary Lagrangian Euler finite element method. The parameters whose effects have been conceptualized here are 102≤Re≤ 103, 104≤Ra≤ 107, and 103≤Bi≤ 104. Air is chosen to be the working fluid with Pr of 0.71. Effects of these parameters are visualized by spatially averaged total entropy generation, spatially averaged total exergy generation, spatially averaged Bejan's number, and fast Fourier transform analysis. FindingsThe present study indicates a 46.91 % rise in entropy generation for Re ranging from 500 to 1000. Moreover, for the same case, a decrement of 88.31 % is observed in exergy generation with the greatest amplitude in the case of the lowest heat transfer. This phenomenon is further supported by the amplitude of the fundamental frequency, where the thermodynamic configuration with the lowest heat transfer has the highest peak. OriginalityAs far as the authors are aware, no previous research has been conducted to analyze the entropy generation characteristics of a hexagonal conjugate transient system that involves a dynamic modulator stirring the flow. Therefore, this study represents a novel contribution to the existing literature on the subject. LimitationsPresent study focused on only a single type of blade irrespective of its aerodynamic design, size, or thickness. Moreover, the blade is also considered to be a rigid body that is not affected by the hoop stress generated from its own rotation.