Monisha Roy

Analysis of Entropy Generation for Mixed Convection in a Square Cavity for Various Thermal Boundary Conditions

Finite element simulations were carried out to analyze entropy generation during mixed convection inside square enclosures with an isothermally hot bottom wall, adiabatic top wall, and isothermally cold side walls (case 1) or linearly heated side walls (case 2), or linearly heated left wall with isothermally cold right wall (case 3) for Pr = 0.015–7.2, Re = 1–100, and Gr = 103–105. Local entropy maps are studied in detail, and the dominance of thermal (Sθ,l) and frictional (Sψ,l) irreversibility is studied using Bejan number maps. In addition, variation in total entropy generation (Stotal), average Bejan number (Beav), and average Nusselt number at the bottom wall with Gr are analyzed to correlate irreversibility and the overall heat transfer rate of the system or process. It is found that, for Pr = 0.015 and 7.2, Re = 100 may be the optimal level for higher convective heat transport with minimum entropy generation in all the cases for Gr = 103–105.

Analysis of Entropy Generation During Mixed Convection in Porous Square Cavities: Effect of Thermal Boundary Conditions

Computational studies on entropy generation during laminar mixed convection in porous square enclosures have been carried out based on Darcy–Brinkman–Forchheimer model using the penalty finite element method. Finite element simulations are performed for the isothermally hot bottom wall, adiabatic top wall, and isothermally cold side walls (case 1) or linearly heated side walls (case 2) or linearly heated left wall with isothermally cold right wall (case 3) for a wide range of modified Darcy numbers (10−5 ≤ Dam ≤ 10−2), Grashof numbers (Gr = 103 − 105), and modified Prandtl numbers (Prm = 0.026 and 7.2). Further, the effects of Dam on the total entropy generation (Stotal), average Bejan number (Beav), and average Nusselt number are discussed. It is found that Re = 100 is preferred over Re = 1 based on larger heat transfer rate with minimum entropy generation for Prm = 0.026 and 7.2, 10−5 ≤ Dam ≤ 10−2 at Gr = 105 for all the cases.

Analysis of entropy generation during natural convection in tilted triangular enclosures with various base angles

ABSTRACT This paper presents a study of entropy generation during natural convection in a triangular enclosure with various configurations (cases 1 and 2 symmetric about Y-axis, and case 3 symmetric about X-axis) for the linearly heated inclined walls. The detailed analysis and comparison for the various base angles (φ = 45° and 60°) of the triangular enclosures have been carried out for Pr = 0.015 − 1,000 and Ra = 103 − 105. The results show that, case 3 configuration with the tilt angle φ = 60° may be the optimal shape based on the minimum total entropy generation (Stotal) with the high heat transfer rate at Ra = 105, irrespective of Pr.

Analysis of entropy generation for mixed convection within porous square cavities: Effects of various moving walls

ABSTRACT The aim of the present investigation is to analyze the effect of the motion of horizontal (cases 1a–1d) and vertical walls (case 2a–2c) on the entropy generation and heat transfer in a porous square cavity during mixed convection. The cavity is subject to the thermal boundary conditions such as the hot bottom wall, cold side walls, and thermally insulated top wall. Analysis has been done for various fluids with Prandtl number, Prm = 0.026–7.2, Grashof number, Gr = 105, Reynolds number, Re = 10–100, and Darcy number, Dam = 10−4–10−2. Numerical results are presented using streamfunction (ψ), local entropy generation due to fluid friction (Sψ), isotherms (θ), and local entropy generation due to heat-transfer (Sθ) contours. In addition, the total entropy generation (Stotal), average Bejan number (Beav), and overall heat-transfer rate at the hot bottom wall are analyzed and discussed.

Role of various moving walls on entropy generation during mixed convection within entrapped porous triangular cavities

ABSTRACT The aim of the present investigation is to analyze the effect of the motion of horizontal walls on the entropy generation and heat transfer rates in an entrapped triangular porous cavity during mixed convection. Two different thermal boundary conditions are considered as follows: (i) hot inclined walls and cold horizontal walls and (ii) cold inclined walls and hot horizontal walls. Overall, Re = 100 may be recommended at Prm = 0.026, 7.2, Gr = 105, and Dam = 10−4 to 10−2 within the upper and lower cavities for cases 1 and 2.