Entropy generation versus transition time of heat exchanger during transient processes

Energy ◽  
2020 ◽  
Vol 200 ◽  
pp. 117490 ◽  
Author(s):  
Kezhen Zhang ◽  
Ming Liu ◽  
Yongliang Zhao ◽  
Chaoyang Wang ◽  
Junjie Yan
Keyword(s):  
Heat Exchanger ◽  
Entropy Generation ◽  
Transition Time ◽  
Transient Processes ◽  
Versus Transition

Entropy generation analysis on a heat exchanger with different design and operation factors during transient processes

Energy ◽  
2018 ◽  
Vol 158 ◽  
pp. 330-342 ◽  
Author(s):  
Chaoyang Wang ◽  
Ming Liu ◽  
Yongliang Zhao ◽  
Yongqiang Qiao ◽  
Junjie Yan
Keyword(s):  
Heat Exchanger ◽  
Entropy Generation ◽  
Transient Processes

scholarly journals Research on the Thermal Hydraulic Performance and Entropy Generation Characteristics of Finned Tube Heat Exchanger with Streamline Tube

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5408
Author(s):  
Zuoqin Qian ◽  
Qiang Wang ◽  
Song Lv
Keyword(s):  
Heat Exchanger ◽  
Entropy Generation ◽  
Thermal Performance ◽  
Flow Characteristics ◽  
Hydraulic Performance ◽  
Finned Tube ◽  
Tube Heat Exchanger ◽  
Finned Tube Heat Exchanger ◽  
Overall Performance ◽  
Present Simulation

Thermal hydraulic performance of the fin-and-tube heat exchanger is presented in this paper. The purpose of this investigation was to investigate the heat transfer mechanism and flow characteristics in the finned tube heat exchanger with streamline tube. The streamline tube in this paper had the streamline cross section which was composed of a semicircle and a half diamond. Three-dimensional numerical simulation was presented and validated by the experiment and the other numerical simulation from public articles. The present simulation had good agreement with the experimental results. The difference of the j factor and f factor between the experimental results and present simulation results by k-ε-enhance model was less than 7.6%. The geometrical parameters were considered as every single variable to investigate the thermal hydraulic performance. The results showed that smaller transversal and larger tube pitch provided greater compactness and better thermal performance. Moreover, a larger angle was not only beneficial to enhance the thermal performance, but also helpful to improve the overall performance. Secondly, the effects of angle on the heat transfer performance and fluid flow characteristics were investigated as the perimeter kept constant. It was shown that the overall performance of the streamline tube was better than the circular tube. Lastly, the entropy generation including frictional entropy generation and the thermal entropy generation were analyzed. It can be concluded that by using the streamline tube, the wake region can be obviously reduced, and thermal performance can be improved.

Detailed Design Optimisation of Three-Fluid Parallel-Flow Plate-Fin Heat Exchanger Using Second Law Analysis

2020 ◽  
Author(s):  
Harpreet Kaur Aasi ◽  
Manish Mishra
Keyword(s):  
Heat Exchanger ◽  
Entropy Generation ◽  
Current Flow ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Continuous Variables ◽  
Minimum Entropy ◽  
Louvered Fin ◽  
Counter Current Flow ◽  
Counter Current

Abstract Three-fluid compact heat exchanger of plate-fin type with parallel-flow configuration is optimised for the entropy generation. Four different types of plate fins (plain rectangular, offset strip, corrugated louvered and wavy fin) are embodied within heat exchanger for both co-current and counter-current flow arrangements have been selected for the study. Genetic algorithm is selected as an optimisation tool having apt in handling various continuous variables and discrete variables and the problems with complexities in the objective function as well as in constraints. Validation of the optimization model is carried out by comparing the results with that from experimental results, Particle swarm optimization (without heat duty constraint) and from graphical method (with heat duty constraint). It is observed that for a specified heat duty and given operating conditions corrugated louvered fin with counter-current flow arrangement offers the minimum entropy generation amongst all.

scholarly journals Numerical Study of Nanofluid Irreversibilities in a Heat Exchanger Used with an Aqueous Medium

Entropy ◽  
2020 ◽  
Vol 22 (1) ◽  
pp. 86
Author(s):  
Guillermo Efren Ovando-Chacon ◽  
Sandy Luz Ovando-Chacon ◽  
Abelardo Rodriguez-Leon ◽  
Mario Diaz-Gonzalez ◽  
Jorge Arturo Hernandez-Zarate ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Aqueous Medium ◽  
Entropy Generation ◽  
Numerical Study ◽  
Oil Extraction ◽  
Hot Water ◽  
Bejan Number ◽  
Extraction Properties ◽  
And Performance

Heat exchangers play an important role in different industrial processes; therefore, it is important to characterize these devices to improve their efficiency by guaranteeing the efficient use of energy. In this study, we carry out a numerical analysis of flow dynamics, heat transfer, and entropy generation inside a heat exchanger; an aqueous medium used for oil extraction flows through the exchanger. Hot water flows on the shell side; nanoparticles have been added to the water in order to improve heat transfer toward the cold aqueous medium flowing on the tube side. The aqueous medium must reach a certain temperature in order to obtain its oil extraction properties. The analysis is performed for different Richardson numbers (Ri = 0.1–10), nanofluid volume fractions (φ = 0.00–0.06), and heat exchanger heights (H = 0.6–1.0). Results are presented in terms of Nusselt number, total entropy generation, Bejan number, and performance evaluation criterion. Results showed that heat exchanger performance increases with the increase in Ri when Ri > 1 and when reducing H.

scholarly journals Statistical analysis of entropy generation in longitudinally finned tube heat exchanger with shell side nanofluid by a single phase approach

2016 ◽  
Vol 37 (2) ◽  
pp. 3-22 ◽  
Author(s):  
Pavan Kumar Konchada ◽  
Vinay Pv ◽  
Varaprasad Bhemuni
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Single Phase ◽  
Pure Water ◽  
Finned Tube ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Phase Approach ◽  
Finned Tube Heat Exchanger

AbstractThe presence of nanoparticles in heat exchangers ascertained increment in heat transfer. The present work focuses on heat transfer in a longitudinal finned tube heat exchanger. Experimentation is done on longitudinal finned tube heat exchanger with pure water as working fluid and the outcome is compared numerically using computational fluid dynamics (CFD) package based on finite volume method for different flow rates. Further 0.8% volume fraction of aluminum oxide (Al2O3) nanofluid is considered on shell side. The simulated nanofluid analysis has been carried out using single phase approach in CFD by updating the user-defined functions and expressions with thermophysical properties of the selected nanofluid. These results are thereafter compared against the results obtained for pure water as shell side fluid. Entropy generated due to heat transfer and fluid flow is calculated for the nanofluid. Analysis of entropy generation is carried out using the Taguchi technique. Analysis of variance (ANOVA) results show that the inlet temperature on shell side has more pronounced effect on entropy generation.

scholarly journals Second Law Analysis for the Experimental Performances of a Cold Heat Exchanger of a Stirling Refrigeration Machine

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 215 ◽  
Author(s):  
Steve Djetel-Gothe ◽  
François Lanzetta ◽  
Sylvie Bégot
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Mass Flow ◽  
Hydraulic Diameter ◽  
Entropy Generation Rate ◽  
Second Law ◽  
Water Mixture ◽  
Fluid Friction ◽  
Refrigeration Machine

The second law of thermodynamics is applied to evaluate the influence of entropy generation on the performances of a cold heat exchanger of an experimental Stirling refrigeration machine by means of three factors: the entropy generation rate N S , the irreversibility distribution ratio ϕ and the Bejan number B e | N S based on a dimensionless entropy ratio that we introduced. These factors are investigated as functions of characteristic dimensions of the heat exchanger (hydraulic diameter and length), coolant mass flow and cold gas temperature. We have demonstrated the role of these factors on the thermal and fluid friction irreversibilities. The conclusions are derived from the behavior of the entropy generation factors concerning the heat transfer and fluid friction characteristics of a double-pipe type heat exchanger crossed by a coolant liquid (55/45 by mass ethylene glycol/water mixture) in the temperature range 240 K < TC < 300 K. The mathematical model of entropy generation includes experimental measurements of pressures, temperatures and coolant mass flow, and the characteristic dimensions of the heat exchanger. A large characteristic length and small hydraulic diameter generate large entropy production, especially at a low mean temperature, because the high value of the coolant liquid viscosity increases the fluid frictions. The model and experiments showed the dominance of heat transfer over viscous friction in the cold heat exchanger and B e | N S → 1 and ϕ → 0 for mass flow rates m ˙ → 0.1 kg.s−1.

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