Numerical simulation of flow and heat transfer characteristics of nanofluids in built-in porous twisted tape tube

Study on the Effective Well Depth of Single U-Shaped Vertical Buried Pipes Based on Temperature Difference Analysis

A heat transfer model of a single U-shaped vertical buried pipe similar to an actual scenario is established, and the accuracy of the model is verified by experiments. The model is used to analyze the heat transfer performance of vertical buried pipe heat exchangers with well depths of 200, 160, 120, and 80 m. This includes the heat transfer per unit well depth, temperature change of the well wall and fluid along the pipe length, heat transfer coefficient, and section heat transfer validity. With the increase in well depth, the heat exchange per unit well depth decreases, and the proportion of heat exchange in the inlet section to the total heat exchange increases. When the well depths are 200, 160, 120, and 80 m, the last 10 m pipe sections have 30, 40.3, 53.7, and 66.4% of the heat exchange efficiencies of the initial 10 m pipe section, respectively. To obtain a reasonably effective well depth of a single U-shaped vertical buried pipe, it is necessary to comprehensively consider the heat exchange per unit well depth, the temperature difference between the well wall and the fluid, and the energy efficiency of the buried pipe section. Moreover, it should be analyzed in combination with economic factors.

A review of different twisted tape configurations used in heat exchanger and their impact on thermal performance of the system

Heat transfer in water with the help of solar energy is an effective way to harness renewable energy and reduce reliance on non-renewable sources of energy. The utilization of turbulent promoters is an efficient solution to ameliorate the performance of heat exchangers (HE). The current work summarizes the experimental and numerical behaviour of HE reported in the literature, including the thermal examinations of HT and fluid flow characteristics with various turbulent promoters and tube arrangements. This article reviews multiple studies in which different twisted tape (TT) geometry enhances the HT rate in various HE tubes. The current work also compares the thermal performance (η) of TT configurations in HE tubes using correlations developed by different investigators. Maximum heat transfer and minimum friction factor concerning fluid utilized in the system may also produce the optimal form for twisted tapes.

Comprehensive Investigation of Thermal and Flow Features of Alloy Based Nanofluid Considering Shape and Newtonian Heating Effects via New Fractional Approach

The core purpose of this work is the formulation of a mathematical model by dint of a new fractional modeling approach to study the dynamics of flow and heat transfer phenomena. This approach involves the incorporation of the Prabhakar fractional operator in mathematical analysis to transform the governing system from a conventional framework to a generalized one. This generalized model evaluates the improvement in thermal efficacy of vacuum pump oil because of the inclusion of aluminum alloy nanoparticles. The flow of the under-observation nanofluid starts due to the combined effects of natural convection and the ramped velocity function at the boundary. Meanwhile, an analysis of the energy equation is conducted by taking the Newtonian heating mechanism into consideration. The characteristics of platelet-, brick-, cylinder-, and blade-shaped alloy nanoparticles are incorporated into the primary system using shape-dependent relations for thermal conductivity and viscosity. Both the classical and generalized models are solved to derive the exact solutions by first inserting some dimension-independent quantities and then operating the Laplace transform on the succeeding equations. These solutions are utilized for the development of graphical illustrations to serve the purpose of covering all features of the problem under consideration. Furthermore, changes in energy and flow functions due to the dominant influences of the relevant contributing factors are delineated with appropriate physical arguments. In addition, the numerical results of the skin friction coefficient and Nusselt number are displayed via multiple tables to analyze the disturbance in shear stress and discuss the contribution of the fractional parameters, the volume concentration of the considered nanoparticles, and the shape factor in the boost of the thermal potential of the considered nanofluid. The findings imply that aluminum alloy nanoparticles have the ability to produce a 44% enhancement in the thermal effectiveness of vacuum pump oil. Moreover, the flow velocity is reduced as the loading range of the nanoparticles rises.

MHD mixed convection and entropy generation of CNT-water nanofluid in a wavy lid-driven porous enclosure at different boundary conditions

In this study, Galerkin Finite Element Method or GFEM is used for the modeling of mixed convection with the entropy generation in wavy lid-driven porous enclosure filled by the CNT-water nanofluid under the magnetic field. Two different cases of boundary conditions for hot and cold walls are considered to study the fluid flow (streamlines) and heat transfer (local and average Nusselt numbers) as well as the entropy generation parameters. Richardson (Ri), Darcy (Da), Hartmann angle (γ), Amplitude (A), Number of peaks (N), Volume fraction (φ), Heat generation factor (λ), Hartmann number (Ha) and Reynolds number (Re) are studied parameters in this study which results indicated that at low Richardson numbers (< 1) increasing the inclined angle of magnetic field, decreases the Nu numbers, but at larger Richardson numbers (> 1) it improves the Nu numbers.