Multi-objective optimization of shell and tube heat exchangers

The effectiveness and cost are two important parameters in heat exchanger design. The total cost includes the capital investment for equipment (heat exchanger surface area) and operating cost (for energy expenditures related to pumping). Tube arrangement, tube diameter, tube pitch ratio, tube length, tube number, baffle spacing ratio as well as baffle cut ratio were considered as seven design parameters. For optimal design of a shell and tube heat exchanger, it was first thermally modeled using ε–NTU method while Bell–Delaware procedure was applied to estimate its shell side heat transfer coefficient and pressure drop. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II) with continuous and discrete variables were applied to obtain the maximum effectiveness (heat recovery) and the minimum total cost as two objective functions. The results of optimal designs were a set of multiple optimum solutions, called ‘Pareto optimal solutions’. The sensitivity analysis of change in optimum effectiveness and total cost with change in design parameters of the shell and tube heat exchanger was also performed and the results are reported.     

Economic optimization of shell and tube heat exchanger based on constructal theory

In this paper, the new approach of constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger.     

Heat transfer and pressure drop performance of twisted oval tube heat exchanger

Twisted oval tube heat exchanger is a type of heat exchanger that aims at improving the heat transfer coefficient of the tube side and also decreasing the pressure drop of the shell side. In the present work, tube side and shell side heat transfer and pressure drop performances of a twisted oval tube heat exchanger has been experimentally studied. The tube side study shows that the tube side heat transfer coefficient and pressure drop in a twisted oval tube are both higher than in a smooth round tube. The shell side study shows that the lower the modified Froude number Fr_M, the higher the shell side heat transfer coefficient and pressure drop. In order to comparatively analyze its shell side performance of the heat exchanger, a rod baffle heat exchanger with similar size of the twisted oval tube heat exchanger is designed and its performance is calculated with Gentry's method. The comparative study shows that the heat transfer coefficient of the twisted oval tube heat exchanger is higher and the pressure drop is lower than the rod baffle heat exchanger. In order to evaluate the overall performance of the twisted oval tube heat exchanger, a performance evaluation criterion considering both the tube side and shell side performance of a heat exchanger is proposed and applied. The analyze of the overall performance of the twisted oval tube shows that the twisted oval tube heat exchangers works more effective at low tube side flow rate and high shell side flow rate.     

摩托车催化器性能考核台架试验中换热器的研究

催化器性能评价试验中，起燃特性和温度特性是两个重要性能，这两个特性的研究都需要对催化器入口温度进行稳定连续的调节。本文设计了冷轧翅片管、整体轧制式、U型管壳式换热器和单程管壳式换热器，通过比较，选定冷轧翅片管换热器进行温度特性和起燃特性试验，试验结果表明该换热器能够达到设计要求，对温度的控制也比较稳定。     

Exergetic optimization of shell and tube heat exchangers using a genetic based algorithm

In the computer-based optimization, many thousands of alternative shell and tube heat exchangers may be examined by varying the high number of exchanger parameters such as tube length, tube outer diameter, pitch size, layout angle, baffle space ratio, number of tube side passes.In the present study, a genetic based algorithm was developed, programmed, and applied to estimate the optimum values of discrete and continuous variables of the MINLP (mixed integer nonlinear programming) test problems. The results of the test problems show that the genetic based algorithm programmed can estimate the acceptable values of continuous variables and optimum values of integer variables. Finally the genetic based algorithm was extended to make parametric studies and to find optimum configuration of heat exchangers by minimizing the sum of the annual capital cost and exergetic cost of the shell and tube heat exchangers. The results of the example problems show that the proposed algorithm is applicable to find optimum and near optimum alternatives of the shell and tube heat exchanger configurations.     

Performance analysis of finned tube and unbaffled shell-and-tube heat exchangers

This work considers an optimum design problem for the different constraints involved in the designing of a shell-and-tube heat exchanger consisting of longitudinally finned tubes. A Matlab simulation has been employed using the Kern's method of design of extended surface heat exchanger to determine the behavior on varying the values of the constraints and studying the overall behavior of the heat exchanger with their variation for both cases of triangular and square pitch arrangements, along with the values of pressure drop. It was found out that an optimum fin height existed for particular values of shell and tube diameters when the heat transfer rate was the maximum. Moreover it was found out that the optimum fin height increased linearly with the increase in tube outer diameter. Further studies were also performed with the variation of other important heat exchanger design features and their effects were studied on the behavior of overall performance of the shell-and-tube heat exchanger. The results were thereby summarized which would proclaim to the best performance of the heat exchanger and therefore capable of giving a good idea to the designer about the dimensional characteristics to be used for designing of a particular shell and tube heat exchanger.     

基于E语言的管壳式换热器设计

管壳式换热器的传统设计过程计算工作量大、效率低。文中在Windows环境中,以E语言为平台,开发管壳式换热器的设计软件,包括工艺设计、热力校核和压降校核,界面友好。计算实例结果表明,所设计换热器的结构和压降都在合理范围内。软件可供工程设计或教学使用,也可为后续换热器的优化设计提供参考。     

Experimental Verification of Selected Artificial Intelligence Algorithms Used for Solving the Inverse Stefan Problem

The article presents a comparative study of three procedures applied for solving the inverse Stefan problem. The investigated problem consists of reconstruction of the unknown boundary condition on the basis of measurement data, and the procedures of solution differ in the way of minimizing the proper functional—in each approach considered, one of three artificial intelligence algorithms (Ant Colony Optimization, Artificial Bee Colony, and Harmony Search) is used. Methods applying the respective algorithms are compared with regard to their velocity and the precision of results.     

Minimizing shell‐and‐tube heat exchanger cost with genetic algorithms and considering maintenance

This paper presents a procedure for minimizing the cost of a shell‐and‐tube heat exchanger based on genetic algorithms (GA). The global cost includes the operating cost (pumping power) and the initial cost expressed in terms of annuities. Eleven design variables associated with shell‐and‐tube heat exchanger geometries are considered: tube pitch, tube layout patterns, number of tube passes, baffle spacing at the centre, baffle spacing at the inlet and outlet, baffle cut, tube‐to‐baffle diametrical clearance, shell‐to‐baffle diametrical clearance, tube bundle outer diameter, shell diameter, and tube outer diameter. Evaluations of the heat exchangers performances are based on an adapted version of the Bell–Delaware method. Pressure drops constraints are included in the procedure. Reliability and maintenance due to fouling are taken into account by restraining the coefficient of increase of surface into a given interval. Two case studies are presented. Results show that the procedure can properly and rapidly identify the optimal design for a specified heat transfer process. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimal geometry and flow arrangement for minimizing the cost of shell‐and‐tube condensers

This paper presents a model for estimating the total cost of shell‐and‐tube heat exchangers (HEs) with condensation in tubes or in the shell, as well as a designing strategy for minimizing this cost. The optimization process is based on a genetic algorithm. The global cost includes the energy cost (i.e. pumping power) and the initial purchase cost of the exchanger. The choice of the best exchanger is based on its annualized total cost. Eleven design variables are optimized. Ten are associated with the HE geometry: tube pitch, tube layout patterns, baffle spacing at the center, baffle spacing at the inlet and outlet, baffle cut, tube‐to‐baffle diametrical clearance, shell‐to‐baffle diametrical clearance, tube bundle outer diameter, shell diameter, and tube outer diameter. The last design variable indicates whether the condensing fluid should flow in the tubes or in the shell. Two case studies are presented and the results obtained show that the procedure can rapidly identify the best design for a given heat transfer process between two fluids, one of which is condensing. Copyright © 2008 John Wiley & Sons, Ltd.     

国标板管间隙对流动与传热的细观影响研究

为了研究国标中规定的板管间隙对管壳式换热器壳程流动与传热的细现影响,运用CFD软件建立管壳式换热器壳程周期模型并进行了数值计算.分析结果表明,当板管间隙小于等于国标Ⅰ级管束规定的最大间隙0.35 mm时,间隙漏流影响的范围很小,折流板之间流体的流动趋近于理想横流,传热效果好;当间隙大于等于国标Ⅱ级管束规定的最大间隙0....     

Optimum Design of Cross-Flow Shell and Tube Heat Exchangers with Low Fin Tubes

This paper presents a simple, efficient, robust, optimum design methodology for the design of a high heat transfer and low pressure drop cross-flow shell and tube heat exchanger with integral low fin tubes. This type of heat exchanger has the potential for application in the design of coolers in hypersonic wind tunnels to cool the air that emerges from the diffuser section of the wind tunnel. The methodology described here allows for the design and optimization of any type of heat exchanger that has constraints on pressure drop, as well as the design of an exchanger for very low pressure drop on the shell side fluid.     

The evaluation of a small capacity shell and tube ammonia evaporator

The use of ammonia as refrigerant is widespread in vapour compression and ammonia/water absorption systems. Ammonia is not actually used in low capacity applications mainly because of the lack of economical available equipment. For this reason, the objective of this study is the numerical and experimental evaluation of a small capacity ammonia shell and tube evaporator with enhanced heat transfer surfaces.An experimental system to evaluate small capacity heat exchangers was developed. A shell and tube evaporator with external low fin tubes was successfully tested. The experimental uncertainty for the evaporator capacity has been estimated within ±5.5%. The experimental results were used to validate a heat exchanger numerical tool that predicts reasonably well the cooling capacity and load outlet temperatures. The methodology presented in this work can be applied to evaluate other refrigerants in similar shell and tube evaporators and to optimize the design of an evaporator for a specific application.     

自激振荡管壳式换热器强化传热的可行性分析

脉动流体能够使管壳式换热器换热系数得到提高,而自激振荡腔在一定的结构参数和运行参数下能够使流体产生脉动。在管壳式换热器前安装自激振荡腔,使流体流经自激振荡腔产生脉动流动,从而实现管壳式换热器的强化传热。分析了将自激振荡腔用于管壳式换热器强化传热可行性。     

Optimization of heat exchanger designs in metal hydride based hydrogen storage systems

Design of the heat exchanger in a metal hydride based hydrogen storage system influences the storage capacity, gravimetric hydrogen storage density, and refueling time for automotive on-board hydrogen storage systems. The choice of a storage bed design incorporating the heat exchanger and the corresponding geometrical design parameters is not obvious. A systematic study is presented to optimize the heat exchanger design using computational fluid dynamics (CFD) modeling. Three different shell and tube heat exchanger designs are chosen. In the first design, metal hydride is present in the shell and heat transfer fluid flows through straight parallel cooling tubes placed inside the bed. The cooling tubes are interconnected by conducting fins. In the second design, heat transfer fluid flows through helical tubes in the bed. The helical tube design permits use of a specific maximum distance between the metal hydride and the coolant for removing heat during refueling. In the third design, the metal hydride is present in the tubes and the fluid flows through the shell. An automated tool is generated using COMSOL-MATLAB integration to arrive at the optimal geometric parameters for each design type. Using sodium alanate as the reference storage material, the relative merits of each design are analyzed and a comparison of the gravimetric and volumetric hydrogen storage densities for the three designs is presented.     

Twisted bundle heat exchangers performance evaluation by CFD (CJ12/5054)

Shell and tube heat exchanger with single twisted tube bundle in five different twist angles, are studied using computational fluid dynamics (CFD) and compared to the conventional shell and tube heat exchanger with single segmental baffles. Effect of shell-side nozzles configurations on heat exchanger performance is studied as well. Heat transfer rate and pressure drop are the main issues investigated in the paper. The results show that, for the same shell-side flow rate, the heat transfer coefficient of heat exchanger with twisted tube bundle is lower than that of the heat exchanger with segmental baffles while shell-side pressure drop of the former is even much lower than that of the latter. The comparison of heat transfer rate per unit pressure drop versus shell-side mass flow rate shows that heat exchanger with twisted tube bundle in both cases of perpendicular and tangential shell-side nozzles, has significant performance advantages over the segmental baffled heat exchanger. Optimum bundle twist angles for such exchangers are found to be 65 and 55° for all shell side flow rates.     

城市污水换热器的方案对比与设计

污水换热器是城市污水源热泵系统中的关键设备。针对污水自身的特点,从工程角度总结了污水换热器必须满足的基本要求和特点;介绍并对比分析了几种常见的污水换热器形式,指出宽流道式换热器将带来阻力增大、能耗增加、投资增长,而壳管式换热器是最科学的污水换热器形式。给出了污水换热器设计的基本方程组,总结给出了工程设计中常见的4种技术条件组合下污水换热器的设计方法。本文提出的换热器结构、性能参数与流道尺寸的普适关系,以及污水换热器的设计方法对污水源热泵工程设计和运行具有指导意义。     

管壳式换热器折流部件优化研究进展

为了提高管壳式换热器的能源利用率,换热器强化传热的研究得到广泛关注。本文从强化传热原理、结构改进和设计优化等三方面对换热器折流部件的优化改进研究进行了分析和总结。其中,强化传热原理主要包括不同折流板通过改变流场的特性影响换热器性能;结构改进包括分段挡板、折流孔板和螺旋挡板的优化进展以及与单弓挡板的对比研究;设计优化包括利用各种新型算法对换热器结构参数的优化和成本的控制。针对管壳式换热器折流部件的强化传热问题,提出了非连续螺旋挡板的研究和结合多目标优化设计的结构改进是未来的重点研究方向。     

An Efficient Method for the Design of Shell and Tube Heat Exchangers

A simple, rapid, and robust algorithm for the design of segmentally baffled shell and tube heat exchangers is presented. The algorithm ensures full use of the maximum allowable pressure drops given typically as design specifications, with no geometric restrictions on the equipment. The core of the algorithm is provided by two compact formulations that relate the pressure drop for each side of the exchanger with the film heat transfer coefficient and the exchanger area. The compact formula for the tube side includes the effects of tube ends while the one for the shell side is based on the Bell-Delaware method. The parameters of the compact formulas are used as search variables in the design algorithm. Two examples are presented that show how the algorithm compares to other reported design methods and how the search for realistic solutions is aided by this method.     

摩托车催化性能考核台架换热器的设计及试验

催化器性能评价试验中,需要调节、控制催化器的入口温度,本文设计了冷轧翅片管、整体轧制式、U型管壳式换热器和单程管壳式换热器,并对四种换热器进行了比较,选定冷轧翅片管换热器进行试验,试验结果表明设计的冷轧翅片管式换热器能够较好的对催化器入口温度进行控制,实用性较好。