Waste Heat Recovery from Air Using Porous Media and Conversion to Electricity

Abstract

This paper presents a numerical study of waste heat recovery from a fluid stream using thermoelectric devices. The system consisted of a square section duct with spherical porous media placed in its central region. Hot air circulates continuously through the duct and exchanges energy with the solid matrix and subsequently with the thermoelectric modules. The mathematical model of the system was solved using ANSYS/FLUENT software, requiring the implementation of user-defined functions (UDFs) and user-defined scalars (UDS) regarding porous media and thermoelectric generation modelling. From the simulations carried out, global efficiency and electrical power values were obtained in the range of [0.11–4.51] [%] and [0.01–12.77] [W], respectively. Furthermore, for the set of variables analysed, it was observed that the performance of the system is favoured by an increase in the fluid inlet temperature and speed, as well as by a higher external heat transfer coefficient.

Numerical Study of Fluid Flow in a Gyroid-Shaped Heat Transfer Element

“…A larger heat exchange area allows heat to be transferred between hot and cold media over a larger surface area; also, the parameter of the surface area enters the calculation of thermal resistance, a reduction of which will increase the total heat flux transferred through the surface area, as described by Mousa et al [8], Kanojiya et al [9], and Leal et al [10]. The enlargement is mainly done by modifying the geometrical parameters in the form of introducing different forms of fins, plates, and slotting [11,12] or by introducing a porous heat-conducting element [13,14], for example, in the form of a three-dimensional lattice, honeycomb structure, or metal foam [15][16][17][18]. The presented paper focuses on the evaluation of the possibility of using the concept of a three-dimensional element increasing the heat exchange surface of heat exchangers, heat accumulators, heat sinks, etc.…”