scholarly journals Application of Second Law Analysis in Heat Exchanger Systems

Entropy ◽  
2019 ◽  
Vol 21 (6) ◽  
pp. 606 ◽  
Author(s):  
Seyed Ali Ashrafizadeh
Keyword(s):  
Heat Exchanger ◽  
Objective Function ◽  
Entropy Generation ◽  
Heat Exchangers ◽  
Driving Forces ◽  
Minimum Point ◽  
Second Law ◽  
Source Modeling ◽  
Operational Variables ◽  
Exergy Losses

In recent decades, the second law of thermodynamics has been commonly applied in analyzing heat exchangers. Many researchers believe that the minimization of entropy generation or exergy losses can be considered as an objective function in designing heat exchangers. Some other researchers, however, not only reject the entropy generation minimization (EGM) philosophy, but also believe that entropy generation maximization is a real objective function in designing heat exchangers. Using driving forces and irreversibility relations, this study sought to get these two views closer to each other. Exergy loss relations were developed by sink–source modeling along the heat exchangers. In this case, two types of heat exchangers are introduced, known as “process” and “utility” heat exchangers. In order to propose an appropriate procedure, exergy losses were examined based on variables and degrees of freedom, and they were different in each category. The results showed that “EGM” philosophy could be applied only to utility heat exchangers. A mathematical model was also developed to calculate exergy losses and investigate the effects of various parameters. Moreover, the validity of the model was evaluated by some experimental data using a double-pipe heat exchanger. Both the process and utility heat exchangers were simulated during the experiments. After verifying the model, some case studies were conducted. The final results indicated that there was not a real minimum point for exergy losses (or entropy generation) with respect to the operational variables. However, a logic minimum point could be found for utility heat exchangers with regard to the constraints.

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.

Second-Law Thermodynamic Comparison and Maximal Velocity Ratio Design of Shell-and-Tube Heat Exchangers With Continuous Helical Baffles

2010 ◽  
Vol 132 (10) ◽  
Author(s):  
Qiu-Wang Wang ◽  
Gui-Dong Chen ◽  
Jing Xu ◽  
Yan-Peng Ji
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchangers ◽  
Velocity Ratio ◽  
Second Law ◽  
Maximal Velocity ◽  
Entropy Generation Number ◽  
Shell And Tube ◽  
The Heat Transfer Coefficient ◽  
Exergy Losses

Shell-and-tube heat exchangers (STHXs) have been widely used in many industrial processes. In the present paper, flow and heat transfer characteristics of the shell-and-tube heat exchanger with continuous helical baffles (CH-STHX) and segmental baffles (SG-STHX) were experimentally studied. In the experiments, these STHXs shared the same tube bundle, shell geometrical structures, different baffle arrangement, and number of heat exchange tubes. Experimental results suggested that the CH-STHX can increase the heat transfer rate by 7–12% than the SG-STHX for the same mass flow rate although its effective heat transfer area had 4% decrease. The heat transfer coefficient and pressure drop of the CH-STHX also had 43–53% and 64–72% increase than those of the SG-STHX, respectively. Based on second-law thermodynamic comparisons in which the quality of energy are evaluated by the entropy generation number and exergy losses, the CH-STHX decreased the entropy generation number and exergy losses by 30% and 68% on average than the SG-STHX for the same Reynolds number. The analysis from nondimensional correlations for Nusselt number and friction factor also revealed that if the maximal velocity ratio R>2.4, the heat transfer coefficient of CH-STHX was higher than that of SG-STHX, and the corresponding friction factor ratio kept at constant fo,CH/fo,SG=0.28.

scholarly journals Thermal Performance in Heat Exchangers by the Irreversibility, Effectiveness, and Efficiency Concepts Using Nanofluids

2020 ◽  
Vol 7 (2) ◽  
pp. F1-F7
Author(s):  
E. Nogueira
Keyword(s):  
Heat Exchanger ◽  
Ethylene Glycol ◽  
Heat Exchangers ◽  
Volume Fraction ◽  
Second Law Of Thermodynamics ◽  
Second Law ◽  
Output Data ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Effectiveness And Efficiency

The objective of the work is to obtain the outlet temperatures of the fluids in a shell and tube heat exchanger. The second law of thermodynamics is applied through the concepts of efficiency, effectiveness, and irreversibility to analyze the results. Water flows in the shell, and a mixture of water-ethylene glycol is associated with fractions of nanoparticles flows in the tube. Water enters the shell at 27 °C, and the mixture comes to the tube at 90 °C. The mass flow is kept fixed in the shell, equal to 0.23 kg/s, and varies between 0.01 kg/s to 0.50 kg/s. Volume fractions equal to 0.01, 0.10, and 0.25 were considered for analysis, for both nanoparticles from Ag and Al2O3. Results for Reynolds number, heat transfer rate, efficiency, effectiveness, and irreversibility are presented for critique, discussion, and justification of the output data found. It is shown that the flow regime has a significant effect on the performance of the analyzed heat exchanger. Keywords: thermodynamics, second law, ethylene glycol, volume fraction.

Determination of Optimum Design Parameters of Horizontal Parallel Pipe and Vertical U-Tube Ground Heat Exchangers

2009 ◽  
Author(s):  
Hakan Demir ◽  
Ahmet Koyun ◽  
S¸. O¨zgu¨r Atayılmaz
Keyword(s):  
Thermal Conductivity ◽  
Energy Consumption ◽  
Heat Exchanger ◽  
Objective Function ◽  
Heat Exchangers ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Soil Thermal Conductivity ◽  
Ground Heat Exchangers ◽  
Ground Source

The most important part of a ground source heat pump (GSHP) is the ground heat exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the ground source heat pump. Soil composition, thermal properties and water content affect the length of ground heat exchanger. Another parameter affects the size of the ground heat exchanger is the shape. There are two basic ground heat exchanger configurations: vertical U-tube and horizontal parallel pipe. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. This study covers comparative thermo-economical analysis of horizontal parallel pipe and vertical u-tube ground heat exchangers. An objective function has been defined based on heating capacity, investment and energy consumption costs of ground heat exchanger. Investment and energy consumption costs were taken into account as total cost in the objective function. The effects of the soil thermal conductivity, number of pipes, thermal capacity of ground heat exchanger, pipe diameter and the burial depth on the objective function were examined. The main disadvantage of U-tube ground heat exchanger is higher borehole cost that makes installation cost higher than parallel pipe ground heat exchanger. To make reference functions equal for both type of ground heat exchangers, the borehole cost must be under 20 $/m (now 55 $/m) for a given heating or cooling capacity. The performance of ground heat exchangers depends on the soil characteristics especially the soil thermal conductivity.

The Second Law Analysis of Thermodynamics for the Plate–Fin Surface Performance in a Cross Flow Heat Exchanger

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Mansour Nasiri Khalaji ◽  
Isak Kotcioglu ◽  
Sinan Caliskan ◽  
Ahmet Cansiz
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Fluid Velocity ◽  
Cross Flow ◽  
Design Parameters ◽  
Second Law ◽  
Transfer Unit ◽  
Pin Fins

In this paper, a particular heat exchanger is designed and analyzed by using second law of thermodynamics. The heat exchanger operates with the cross flow forced convection having cylindrical, square, and hexagonal pin fins (tubular router) placed in the rectangular duct. The pin fins are installed periodically at the top and bottom plates of the duct perpendicular to the flow direction, structured in-line, and staggered sheet layouts. The entropy generation in the flow domain of the channels is calculated to demonstrate the rate of irreversibilities. To obtain the efficiencies, irreversibility, thermal performance factor, and entropy generation number (EGN), the heat exchanger is operated at different temperatures and flow rates by using hot and cold fluids. Optimization of the design parameters and winglet geometry associated with the performance are determined by entropy generation minimization. The variation of the EGN with Reynolds number for various tubular routers is presented. The Reynolds number is determined according to the experimental plan and the performance is analyzed with the method of effectiveness—number of transfer unit (NTU). Based on particular designs, it was determined that the increment in fluid velocity enhances the heat transfer rate, which in turn decreases the heat transfer irreversibility.

Second-Law-Based Thermoeconomic Optimization of Two-Phase Heat Exchangers

1987 ◽  
Vol 109 (2) ◽  
pp. 287-294 ◽  
Author(s):  
S. M. Zubair ◽  
P. V. Kadaba ◽  
R. B. Evans
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Unit Cost ◽  
Second Law ◽  
Inlet Temperature ◽  
Two Phase ◽  
Transfer Resistance

This paper presents a closed-form analytical method for the second-law-based thermoeconomic optimization of two-phase heat exchangers used as condensers or evaporators. The concept of “internal economy” as a means of estimating the economic value of entropy generated (due to finite temperature difference heat transfer and pressure drops) has been proposed, thus permitting the engineer to trade the cost of entropy generation in the heat exchanger against its capital expenditure. Results are presented in terms of the optimum heat exchanger area as a function of the exit/inlet temperature ratio of the coolant, unit cost of energy dissipated, and the optimum overall heat transfer coefficient. The total heat transfer resistance represented by (1/U = C1 + C2 Re−n) in the present analysis is patterned after Wilson (1915) which accommodates the complexities associated with the determination of the two-phase heat transfer coefficient and the buildup of surface scaling resistances. The analysis of a water-cooled condenser and an air-cooled evaporator is presented with supporting numerical examples which are based on the thermoeconomic optimization procedure of this paper.

Cost and Entropy Generation Minimization of a Cross-Flow Plate Fin Heat Exchanger Using Multi-Objective Genetic Algorithm

2010 ◽  
Vol 133 (2) ◽  
Author(s):  
Pouria Ahmadi ◽  
Hassan Hajabdollahi ◽  
Ibrahim Dincer
Keyword(s):  
Genetic Algorithm ◽  
Heat Exchanger ◽  
Entropy Generation ◽  
Heat Exchangers ◽  
Annual Cost ◽  
Stream Flow ◽  
Total Annual Cost ◽  
Decision Variables ◽  
Flow Length ◽  
Nondominated Sorting

In the present work, a thermal modeling is conducted for optimal design of compact heat exchangers in order to minimize cost and entropy generation. In this regard, an ε−NTU method is applied for estimation of the heat exchanger pressure drop, as well as effectiveness. Fin pitch, fin height, fin offset length, cold stream flow length, no-flow length, and hot stream flow length are considered as six decision variables. Fast and elitist nondominated sorting genetic algorithm (i.e., nondominated sorting genetic algorithm II) is applied to minimize the entropy generation units and the total annual cost (sum of initial investment and operating and maintenance costs) simultaneously. The results for Pareto-optimal front clearly reveal the conflict between two objective functions, the number of entropy generation units and the total annual cost. It reveals that any geometrical changes, which decrease the number of entropy generation units, lead to an increase in the total annual cost and vice versa. Moreover, for prediction of the optimal design of the plate fin heat exchanger, an equation for the number of entropy generation units versus the total annual cost is derived for the Pareto curve. In addition, optimization of heat exchangers based on considering exergy destruction revealed that irreversibilities, such as pressure drop and high temperature difference between cold and hot streams, play a key issue in exergy destruction. Thus, more efficient heat exchanger leads to have a heat exchanger with higher total cost rate. Finally, the sensitivity analysis of change in the optimum number of entropy generation units and the total annual cost with change in the decision variables of the plate fin heat exchanger is also performed, and the results are reported.

Two Principles of Differential Second Law Heat Exchanger Design

1991 ◽  
Vol 113 (2) ◽  
pp. 329-336 ◽  
Author(s):  
R. B. Evans ◽  
M. R. von Spakovsky
Keyword(s):  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Second Law ◽  
First Principle ◽  
Heat Exchanger Design ◽  
Geometric Average ◽  
Mean Temperature ◽  
Second Law Analysis ◽  
Basic Treatment

In this paper, two fundamental principles of differential Second Law analysis are set forth for heat exchanger design. The first principle defines a Second Law temperature, while the second principle defines a Second Law temperature difference. The square of the ratio of the Second Law temperature difference to the Second Law temperature is shown always to be equal to the negative of the partial derivative of the rate of entropy generation (for heat transfer) with respect to the overall conductance of the heat exchanger. For the basic design of elementary heat exchangers, each of these two Second Law quantities is shown to take the form of a simple geometric average. Nonelementary considerations result in corrected geometric averages, which relate directly to the corrected log-mean temperature difference. Both the corrected log-mean temperature difference (nonelementary considerations) and the uncorrected or just log-mean temperature difference (elementary considerations) are widely used in heat exchanger analysis. The importance of these two principles in both exergy and essergy analysis is illustrated by a unified basic treatment of the optimum design of elementary heat exchangers. This results in a single optimization expression for all flow arrangements (i.e., counterflow, parallel flow, and certain crossflow cases).

Plate-fin heat exchanger network modeling, design and optimization – a novel and comprehensive algorithm

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Reza Ramezanpour Jirandeh ◽  
Mehrangiz Ghazi ◽  
Amir Farhang Sotoodeh ◽  
Mohammad Nikian
Keyword(s):  
Heat Exchanger ◽  
Objective Function ◽  
Heat Exchangers ◽  
Annual Cost ◽  
Cross Flow ◽  
Total Annual Cost ◽  
Geometrical Parameters ◽  
Heat Exchanger Network ◽  
Content Type ◽  
Decision Variables

Purpose The purpose of this paper is to present a novel and applied method for optimum designing of plate-finned heat exchanger network. Considering the total annual cost as the objective function, a network of plate-finned heat exchanger is designed and optimized. Design/methodology/approach Accurate evaluation of plate-finned heat exchanger networks depends on different fin types with 10 different geometrical parameters of heat exchangers. In this study, fin numbers are considered as the main decision variables and geometrical parameters of fins are considered as the secondary decision variables. The algorithm applies heat transfer and pressure drop coefficients correction method and differential evolution (DE) algorithm to obtain the optimum results. In this paper, optimization and minimization of the total annual cost of heat exchanger network is considered as the objective function. Findings In this study, a novel and applied method for optimum designing of plate-finned heat exchanger network is presented. The comprehensive algorithm is applied into a case study and the results are obtained for both counter-flow and cross-flow plate-finned heat exchangers. The total annual cost and total area of the network with counter-flow heat exchangers were 12.5% and 23.27%, respectively, smaller than the corresponding values of the network with cross-flow heat exchanger. Originality/value In this paper, a reliable method is used to design, optimize parameters and the economic optimization of heat exchanger network. Taking into account the importance of plate-finned heat exchangers in industrial applications and the complexity in their geometry, the DE methodology is adopted to obtain an optimal geometric configuration. The total annual cost is chosen as the objective function. Applying this technique to a case study illustrates its capability to accurate design plate-finned heat exchangers to improve the objective function of the heat exchanger network from the economic viewpoint with the design of details.

HENEA-3: A Second Law Based Expert Assistant for the Synthesis of Heat Exchanger Networks

2006 ◽  
Author(s):  
S. Mastromanno ◽  
J. Petrucci ◽  
E. Sciubba
Keyword(s):  
Heat Exchanger ◽  
Entropy Generation ◽  
Optimization Procedure ◽  
Maximum Energy ◽  
Point Of View ◽  
Optimal Configuration ◽  
Second Law ◽  
Graphic User Interface ◽  
Optimization Criteria ◽  
Minimum Capital

The present paper describes the latest development of an Expert System for the design and optimization of Heat Exchange Networks (HEN). The code described herein, HENEA (acronym for Heat Exchanger Network Expert Assistant) is a Knowledge Based System capable of interacting with a Process Engineer to generate an optimal configuration for a HEN under several different objective functions. Contrary to most of the currently available methods, the code is able to produce such solutions by making explicit use of a set of Second Law Analysis criteria and of some of the basic principles of the “Pinch Method”. With respect to the previous version, HENEA now includes an additional application, “HEN-SPLIT” that accounts for the possibility of splitting one or more of the participating streams according with a general “minimal entropy generation” criterion. In its present version, HENEA can be used both for process design (new HEN) and for process structural optimization (retrofit problems). The optimization procedure is based on Sama’s “Second Law Insight Method” and is directly and explicitly finalized to the reduction of the global entropy generation. The code is also endowed with a cost calculations utility, and can be thus employed to search for the optimum using two alternative optimization criteria: it generates in fact both a Maximum Energy Recovery (MER) and Minimum Exchange Area configuration (MCC, Minimum Capital Cost). Since the code is though intended for practical industrial use, and it is well known that a thermodynamically optimal configuration is not always the “most convenient” one from an engineering point of view, HENEA presents to the user also a certain number of additional sub-optimal configurations. An interactive graphic user interface makes HENEA very user-friendly: furthermore, the user can (indirectly) interrogate HENEA about its choices and understand the underlying physic in an unambiguous and immediate way. Several tests conducted on some of the available benchmarks have proven that the solutions generated by HENEA are always comparable to those produced by other optimization criteria (Pinch Method or Second Law method): in fact, for large problems (many participating streams, several splittings) they are often better than those obtained with its competitors.

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