Optimization Investigation of Bionic Fin Structure by Experimental and Numerical Modelling

Purpose To improve the thermal performance of base fluid, nanoparticles of three types are dispersed in the base fluid. A novel theory of non-Fourier heat transfer is used for design and development of models. The thermal performance of sample fluids is compared to determine which types of combination of nanoparticles are the best for an optimized enhancement in thermal performance of fluids. This article aims to: (i) investigate the impact of nanoparticles on thermal performance; and (ii) implement the Galerkin finite element method (GFEM) to thermal problems. Design/methodology/approach The mathematical models are developed using novel non-Fourier heat flux theory, conservation laws of computational fluid dynamics (CFD) and no-slip thermal boundary conditions. The models are approximated using thermal boundary layer approximations, and transformed models are solved numerically using GFEM. A grid-sensitivity test is performed. The accuracy, correction and stability of solutions is ensured. The numerical method adopted for the calculations is validated with published data. Quantities of engineering interest, i.e. wall shear stress, wall mass flow rate and wall heat flux, are calculated and examined versus emerging rheological parameters and thermal relaxation time. Findings The thermal relaxation time measures the ability of a fluid to restore its original thermal state, called thermal equilibrium and therefore, simulations have shown that the thermal relaxation time associated with a mono nanofluid has the most substantial effect on the temperature of fluid, whereas a ternary nanofluid has the smallest thermal relaxation time. A ternary nanofluid has a wider thermal boundary thickness in comparison with base and di- and mono nanofluids. The wall heat flux (in the case of the ternary nanofluids) has the most significant value compared with the wall shear stresses for the mono and hybrid nanofluids. The wall heat and mass fluxes have the highest values for the case of non-Fourier heat and mass diffusion compared to the case of Fourier heat and mass transfer. Originality/value An extensive literature review reveals that no study has considered thermal and concentration memory effects on transport mechanisms in fluids of cross-rheological liquid using novel theory of heat and mass [presented by Cattaneo (Cattaneo, 1958) and Christov (Christov, 2009)] so far. Moreover, the finite element method for coupled and nonlinear CFD problems has not been implemented so far. To the best of the authors’ knowledge for the first time, the dynamics of wall heat flow rate and mass flow rate under simultaneous effects of thermal and solute relaxation times, Ohmic dissipation and first-order chemical reactions are studied.

Thermal and hydraulic performances of the wavy microchannel heat sink with fan-shaped ribs on the sidewall

Optimization study of cross-cut flow control for heat transfer enhancement in wavy fin heat exchangers: Concept of cross-cut reference length

Thermally efficient gas burners can be designed by optimising the parameters associated with combustion and heat transfer mechanisms. The current study presents the thermal analysis of the premixed methane-air flame jets of circular tube gas burner impinging on a target surface. The effect of flame jet parameters such as mixture Reynolds number, equivalence ratio and burner to target surface spacing on heat transfer characteristics is investigated. The thermal performance is quantified in terms of thermal efficiency. The lean and stoichiometric mixtures release maximum amount of thermal energy. However, in lean flames, a part of the energy released is used for rising the temperature of excess air. Though the combustion is incomplete for fuel rich flames, higher heat transfer is achieved because of higher flame height. The optimal thermal performance is observed when the mixture is near stoichiometric and the burner is spaced from the target surface such that the premixed cone tip just touches the surface.

The present numerical study reports the thermal performance of the straight porous fin with temperature‐dependent thermal conductivity, radiation, and magnetic field effects. The heat transfer model comprising the Darcy's law for simulating flow with solid‐fluid interactions in porous medium, Rosseland approximation for heat transfer through radiation, Maxwell equations for magnetic field effect and linearly varying temperature dependent thermal conductivity, results into highly nonlinear ordinary differential equation. The governing equation is solved using a finite difference scheme with suitable boundary conditions. The obtained solutions are physically interpreted by considering the impact of different nondimensional parameters on thermal performance, efficiency, and effectiveness of the system through plotted graphs. A detailed result with regard to the Nusselt number at the fin base is calculated. The results obtained are observed to be in excellent agreement with previous studies. From the study, it is observed that there is a significant effect on the thermal performance of the fin in the presence of porous constraints; also, results reveal that the nonlinear thermal conductivity parameter strengthens the thermal performance, efficiency, and effectiveness of the fin. Furthermore, the results of the study reveal that the rate of heat transfer of the fin increases with the increase in the magnetic parameter and radiation parameter.

Thermal performance assessment of self-rotating twisted tapes and Al2O3 nanoparticle in a circular pipe

This study investigated the heat transfer and fluid flow characteristics of laminar and turbulent regimes in microchannels using a combined experimental and numerical approach. The objective of the study was to evaluate the influence of Reynolds number on thermal and hydraulic performance and to assess the applicability of conventional heat transfer correlations at microscale dimensions. An experimental setup consisting of a heated microchannel test section, controlled flow delivery system, and precision temperature and pressure measurement instruments was employed to obtain data for a wide range of Reynolds numbers covering both laminar and turbulent flow regimes. Complementary computational fluid dynamics simulations were conducted using appropriate governing equations and boundary conditions to predict velocity, temperature, and pressure fields within the microchannel. The results showed that the Nusselt number increased with Reynolds number in both flow regimes, with turbulent flow exhibiting significantly higher heat transfer rates than laminar flow. However, the turbulent regime was also associated with substantially higher friction factors and pressure drops, indicating increased pumping power requirements. The experimental and numerical results demonstrated close agreement, validating the reliability of the numerical model. The study further revealed that microscale effects such as entrance length influence and enhanced convection caused deviations from classical theoretical predictions developed for macroscale channels. Overall, the findings established that optimal microchannel thermal performance was achieved at moderate turbulent Reynolds numbers, where heat transfer enhancement outweighed hydraulic penalties. The study provided valuable insights for the design and optimisation of microchannel heat exchangers used in electronics cooling, energy systems, and other high heat flux applications.

Numerical study on convective heat transfer and friction characteristics of molten salts in circular tubes

Numerical study on thermal and hydraulic performance of a stacked-plate jet-impingement/microchannel heat sink

Experimental investigation of effect of different tube row-numbers, fin pitches and operating conditions on thermal and hydraulic performances of louvered and wavy finned heat exchangers

Iraq's high climatic temperature affects buildings' thermal performance, leading to increased electrical energy consumption due to population growth. Researchers are exploring methods to reduce this consumption, such as heat gain reduction, heat transfer prevention, thermal insulators, high-thermal resistance materials, positive building design, useful orientation, and clean energies. The study investigates solar heat transfer in Iraqi air-conditioned spaces using nine models to analyze the impact of building elements on residential walls and their cross-section shape. The aim is to determine the best model for the Iraqi climate and the optimal approach for achieving optimal solar heat transfer. The study reveals that Model A has negative thermal performance, while Model C and I offer superior thermal performance. Model C offers 47.34% energy savings and Model I 43.99%, aligning with the global trend for green buildings and low energy expenditure in Iraqi residential units.

Fins are surface extensions used to increase the rate of heat transfer from a heated surface to the surrounding cooler fluid or from a heated fluid to the surface. In this article, we describe new families of straight and pin fins for which the temperature distribution along the fin as well as fin effectiveness and efficiency can be computed in closed form. The profile of the new straight fin is a circular arc centered on the fin’s longitudinal axis, while the profile of the new pin fin is a more complex concave parametric curve. Although the pattern of temperature distribution in these fins is remarkably similar to that in the classic straight and pin fins of constant thickness, the geometry of the new fins is strikingly different; in particular, the maximum length of the new fins is finite. We also discovered that both classic fins of constant thickness and novel fins described in this work have the following equivalence property: if the ratio of the heat transfer coefficient on the fin’s tip to that on the lateral surface is not too high, then the temperature distribution for a fin with a non-adiabatic boundary condition at the tip is identical to that for a longer fin of the same kind with adiabatic tip. Our analysis of heat transfer by fins is only based on standard homogeneity, steady-state, and one-dimensionality assumptions. In particular, we completely dispense with the “length-of-arc” assumption that underlies most of the previous works.

Thermal enhancement of rectangular channels using hook-shaped fins and dimples

The impact of wall movements in different directions on mixed convection flow and thermal performance in a wavy chamber is reported. The wavy wall of the chamber is heated non-uniformly, and the upper wall is kept at a constant cold temperature, while the vertical walls of the chamber are adiabatic. Four different cases, namely Case-1, Case-2, Case-3 and Case-4, are considered on the basis of multi-directional movements of the walls of the chamber. Mathematical model of the flow physics consists of the Navier–Stokes (N-S) equations in streamfunction ( $$\psi$$ ) —vorticity ( $$\zeta$$ ) formulation including the energy transport equations which are solved by higher-order compact (HOC) scheme on curvilinear grids Pandit SK, Chattopadhyay A.(Comput Math Appl 74(6):1414–34 2017) [45]. It is found that the fluid flow and thermal performance are both influenced by the direction of moving lids and the undulations of the wavy bottom surface of the chamber. Optimum thermal performance is noticed when the wavy bottom surface of the chamber is employed with one undulation at low Richardson number (Ri). Moreover, for $$Ri=0.01$$ , Case-2, in which the upper lid is moving in left direction and the left lid is moving in upward direction, gives better heat transfer rate with maximum value of average Nusselt number for one undulation. Furthermore, it is noticed that among all the cases, the cases (Case-2 and Case-4) in which upper lid is moving in left direction produce minimum entropy generation for every undulations of the wavy surface with each of the Ri values. So, on the basis of better heat transfer rate and the minimum entropy generation, Case-2 and Case-4 may be recommended as optimum configurations.

Thermal management of the lithium-ion battery by the composite PCM-Fin structures