Faculty Publications

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Performance score based multi-objective optimization for thermal design of partially filled high porosity metal foam pipes under forced convection
(Elsevier Ltd, 2022) Jadhav, P.H.; Trilok, G.; Gnanasekaran, N.; Mobedi, M.
Optimization study in flow through metal foams for heat exchanging applications is very much essential as it involves variety of fluid flow and structural properties. Moreover, the identification of best combinations of structural parameters of metal foams for simultaneous improvement of heat transfer and pressure drop is a pressing situation. In this work, six different metal foam configurations are considered for the enhancement of heat transfer in a circular conduit. The foam is aluminum with PPI varying from 10 to 45 and almost the same porosity (0.90-0.95). The aluminum foams are chosen from the available literature and they are partially filled in the conduit to reduce the pressure drop. For a constant heat flux condition, the goal is to find out the efficient metal foam and configurations when air is considered as a working fluid. A special attention is paid to the preference between pressure drop and heat transfer enhancements. That is why TOPSIS optimization techniques with five different criteria (contains the combination of the weightage/priority of heat transfer and pressure drop) is used. Based on the numerical results of heat and fluid flow in conduit, it is found that when an equal importance is given to both heat transfer and friction effect, 30 PPI aluminum foam with 80% filling on the inner lateral of the pipe provides the best score as 0.8197. The best configuration and PPI for different preferences between friction and heat transfer enhancements is discussed in details. The Reynolds number varies from 4500 to 16500. © 2021 Elsevier Ltd
Numerical assessment of thermal characteristics of metal foams of orderly varied pore density and porosity under different convection regimes
(Elsevier Masson s.r.l., 2022) Trilok, G.; Kumar, K.K.; Gnanasekaran, N.; Mobedi, M.
The present study is done to analyze heat transfer and fluid flow in a channel with orderly varied pore density and porosity combination of foam samples. Darcy Forchheimer flow and LTNE thermal models are considered to estimate heat transfer characteristics. Considering the effect of orderly varied combinations of the dual structural properties, forced convection over a range of flow velocities and natural convection phenomenon are studied numerically in the channel housing porous samples. Two limiting solutions for Nusselt number (Nu) i.e., Nun (for natural convection) and Nuf (for forced convection) for Ri→∞ and Ri→0 respectively, as a function of independent variable Richardson number (Ri) with structural properties pore density and porosity are obtained with the help of local thermal non-equilibrium (LTNE) thermal model and Darcy-Forchheimer flow model. Further these asymptotic solutions are blended using technique illustrated in the literature in order to obtain solution for Nusselt number for mixed convection (Num). Correlations for Nusselt number as a function of combination of porosity and pore density are obtained emphasizing on the varied significance of these parameters in different convection regime. The present study not only emphasizes on effect of combination of structural properties of metal foams on heat transfer characteristics, but also illustrates a technique that enables to arrive at suitable correlation for an intermediate phenomenon existing between two other extremes, with zero computational cost. Effect of pore density on heat transfer characteristics at a given porosity, is found to be not much influencing in natural convection dominant regime. However, in mixed and forced convection dominant scenario it is illustrated that, effect of variation in pore density and porosity plays a significant role in expressing distinguishable heat transfer characteristics, along with other well-known independent parameters such as porosity and Reynolds number. © 2021 Elsevier Masson SAS
Inverse estimation of heat flux under forced convection conjugate heat transfer in a vertical channel fully filled with metal foam
(Elsevier Ltd, 2022) Trilok, G.; Vishweshwara, P.S.; Gnanasekaran, G.
In this work, for the first time, a heat flux at the boundary is estimated for a conjugate heat transfer under forced convection in the presence of high porosity metal foams. For the forward problem a vertical channel experimental set up reported in the literature is considered. The metal foam placed in the vertical channel is subjected to constant heat flux through aluminum plate and airflow of various velocities is passed through vertical channel for removal of heat from the high porosity metal foam placed in the vertical channel. Six different velocities are considered and the required temperature distribution of the aluminum plate is obtained by solving Darcy extended Forchheimer and Local Thermal non-equilibrium models for metal foams. The forward problem, created using computational fluid dynamics in ANSYS-FLUENT, is substituted with Neural Network for faster computation of the forward problem. The maximum errors between the computational fluid dynamics and Artificial Neural Network models for the heat flux values of 466.66, 666.66 and 1133.3 W/m2 are found to be 0.086, 0.043, 0.092 respectively. The heat flux to the forward problem is treated as unknown and the same is estimated using an inverse method that couples Particle Swarm Optimization with Bayesian framework. The result of inverse estimation of exact temperature data shows that for a heat flux of 1266.64 W/m2 the error is found to be 1.6e−4%. Similarly, for the noise added temperature data, the absolute % error in heat flux of 599.985, 733.315 and 1266.635 W/m2 is 4.80e−2%, 2.20e−2%, 2.30e−2% respectively. © 2022 Elsevier Ltd

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