Entropy Generation Performance Research Articles

Examination of convective heat transfer and entropy generation performance in twisted elliptical tubes using response surface method

In this paper, the convective heat transfer (CHT) and flow properties of twisted elliptical tubes (TETs) are numerically simulated within the range of Reynolds numbers (Re) 710 to 4790. The effects of design parameters such as twist ratio (P/D), aspect ratio (A/B), and Re on the CHT and flow resistance properties of TETs are highlighted. The response surface method (RSM) is used to research the effect of interaction between design parameters on the performance of CHT in TETs and establish the relationship between the objective function, i.e., Nusselt number (Nu), friction factor (f), and design parameters. The objective function fitted by RSM are optimized by the non-dominated sequential genetic algorithm (NSGA-II) to obtain the Pareto optimal solution. Besides, the entropy generation minimization principle explores entropy generation characteristics to reveal the mechanism of CHT enhancement in TETs. The results show that the CHT performance, flow resistance, and total entropy generation in TET increase, decrease, and increase with the growth of Re, respectively. They all increase with the reduction of P/D or the growth of A/B. The maximum values of Nu and pressure drop (ΔP) occur when A/B = 2.16 and P/D = 11.90; the minimum value of total entropy generation is reached when A/B = 1.34 and P/D = 26.33; and the Pareto optimal solution corresponds to the best combination of design parameters of Re = 3980, P/D = 13.32, and A/B = 1.82.

Entropy generation and heat transfer performance analysis of a non-Newtonian NEPCM in an inclined chamber with complicated heater inside

The present research deals with thermic energy storage structures based on nano-encapsulated phase change material with a complicated charger inside the storage system. Flow structures, heat transfer, and entropy generation performance are studied using the partial differential governing equations based on non-Newtonian nature of the working medium. Analysis has been performed numerically using the finite element method. Effects of the cavity inclination angle, inner charger structure, power-law index for non-Newtonian nature of the working liquid, Rayleigh number, and nanoparticles volume fraction on flow structures, entropy generation fields and temperature fields have been studied. It has been found that the considered dilatant working fluid is not effective for the heat transfer applications, because Nusselt number decreases with a growth of the power-law index. At the same time, the cavity inclination angle and inner heater structure can be effective parameters to manage the heat transfer and entropy generation.

Effect of arc corrugation initiation on the thermo-hydraulic performance and entropy generation of the corrugated tube

It's important to know which corrugation start provides the best heat transfer performance with the least frictional losses. Thus, the present work focuses on the performance of corrugated tubes with different corrugation initiation. The different types of arc corrugations (outward arc, inward arc, outward arc-inward arc, and inward arc-outward arc) are used for assessing the entropy generation and thermo-hydraulic performance of the tubes under the application of constant wall heat flux. The different corrugation starts have a different effect on the thermo-hydraulic and entropy generation performance. For all the considered flow rates, the outward arc-inward arc configuration has the highest Nusselt number. The combination of inward and outward arc corrugations results in better heat transfer, but this improved heat transfer is at the expense of the pressure drop. The total and heat transfer entropy generation in the corrugated and smooth tubes reduce with an increment in the Reynolds number, while frictional entropy generation enhances. The outward arc-inward arc configuration results in the lowest total entropy generation at the highest Reynolds number and it is 0.398 W/K. All the corrugated tubes have entropy generation number less than unity, which is advantageous because of better heat transfer and lesser system irreversibility.

Influence of structure parameters on entropy generation performance in cross wavy channels with fluid-solid coupled heat transfer

In the present work, the three-dimensional numerical model of the fluid-solid coupled heat transfer between hot gas and compressed cold air in cross wavy (CW) channels is established. Based on the periodic structure of CW channels, three units are adopted instead of the whole channel to research the influence of ratio of pitch to circle radius of air channel (P/R2) and height to circle radius of air channel (H/R2) on entropy generation. In Reynolds number (Re) range of 100–1300, five types of CW channel with fluid-solid coupled heat transfer are analyzed. The simulation results show the thermal entropy generation accounts for a large part of the total entropy generation in gas and air channels. In addition, the smaller P/R2 value leads to the smaller total entropy generation, and the larger H/R2 value leads to the smaller total entropy generation. Therefore, CW channels which have smaller P/R2 value, larger H/R2 value and lower Reynolds number can reduce the total irreversibility to the least under the same flow conditions.

Numerical analysis of heat transfer and flow dynamics in a pipe with square extruded bluff cylinder inserts

This paper presents the computational study of convective heat transfer enhancement and entropy generation performance by using bluff cylinder. A two-dimensional numerical simulation is executed successfully on thermo-hydraulic transport characteristics for a square extruded bluff cylinder placed inside duct. The test fluid, air (Pr 0.707), is used for the experiment. The turbulent SST scheme is engaged for the simulation. The simulation is accomplished with the aim to achieve an understanding of physical performance and activities of the thermo-fluidic flow inside the channel fitted with bluff body at 15D spacing from the inlet under constant temperature conditions at wall. The simulation is done to cover cross flow encompassing both laminar as well as turbulent flow regime in the range of Reynolds number (Re) up to 1×105 and inlet intensities from 5% to 40%. The effects of outlet temperature and Nusselt number is esteemed and considered. No ideal Re has been detected which could reduce the total entropy generation. It is highly promising to be executed in the practical relevance like power and energy industry.