Heat exchanger network theory pdf

Hot streams are drawn at the top of the grid, and flow from left to right. Mar 26, 2020 platefin heat exchangers have lots of thin metal plates or fins with a large surface area because that exchanges more heat more quickly. Heat exchangers can be classified into four types, according to. Heat exchanger network synthesis including detailed heat. Heat exchangers are used in both cooling and heating processes.

One of the rules used to ensure that the best heat exchanger configuration is found is. We propose mixedinteger linear programming models for utility targeting and heat exchanger network synthesis that account for variable stream temperatures and flow rates as well as unclassified streams and thus can be integrated with process synthesis optimization models. The term heat exchanger applies to all equipment used to transfer heat between two streams. Design of heat exchanger network based on entransy theory. Hot streams are drawn at the top of the grid, and flow from left to. This implies that the maximum number of sizes mse of heat exchangers available is. Steady heat transfer february 14, 2007 me 375 heat transfer 2 7 steady heat transfer definition in steady heat transfer the temperature and heat flux at any coordinate point do not change with time both temperature and heat transfer can change with spatial locations, but not with time steady energy balance first law of. Good practice for heat exchanger selection and design page 1 of 12 good practice for heat exchanger selection and design. In contrast to the parallel flow heat exchanger, the counter flow heat exchanger can have the hottest coldfluid temperature greater than the coldest hotfluid temperatue. The overall heat transfer coefficient of the exchanger is 300 wm2 k, and the area for heat transfer is 15. Heat exchanger seminar ppt with pdf report study mafia.

To heat a cooler fluid by means of a hotter fluid 2. Process design decisions and project economics by dr. Theory and application two fluids, of different starting. Mod05 lec04 pinch technology for heat exchanger network. Plate heat exchangers were first produced in the 1920s and have since been widely used in a great number of sectors a plate exchanger consists of a series of parallel plates that are placed one above the other so as to allow the formation of a series of channels for fluids to flow between them. Grid representation it is convenient to represent a heat exchanger network as a grid. Design of the best heat exchanger network is an optimization problem where the total cost is to be minimized. This is a technique for evaluating the heat flows in any heat exchanger network. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. If outlet temperatures of a network are known we can start with static simulation, that is because effectiveness are known. Boyd street, t335, norman, oklahoma 73072, united states oksolutions, 4017 hatterly lane, norman, oklahoma 73072, united states abstract. On the minimum number of units in heat exchanger networks. Moholkar,department of chemical engineering,iit guwahati. Plate heat exchanger working principle, how a plate heat.

The amount of heat transfer is equal to the maximum heat transfer thermodynamically possible. The heat exchanger network design can be viewed by clicking the open hen grid diagram icon in the hi case view. The concept of heat exchanger efficiency eliminates the need for charts, or complicated performance expressions, providing a convenient approach for solving heat exchanger rating, and sizing problems, as well as network of heat exchangers. Economic simulation of a sample heat exchanger network.

Introduction to whom all correspondence should be addressed heat exchanger networks hens are widely employed in. Steadystate simulations were used to delineate the tradeoff between flexibility and capital costs of networks. A heat exchanger is a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid. Heat exchanger network hen synthesis is a means of utilizing the heat available in a process. Conduction energy is transferred between solids or stationary. Apr 11, 2014 it is convenient to represent a heat exchanger network as a grid. The maximum number of heat exchangers mhe in the network is 8. If the heat exchanger is located at the inlet or discharge of a blower with a pulsating flow, such as a roots type rotary lobe blower, the heat exchanger must be protected from the pulsation by a chambered silencer. As its name implies, this type of heat exchanger consists of a shell a large vessel with a bundle of tubes inside it. Temperature interval method for heat exchanger networks.

The pinch design method ensures that these targets are achieved during the network design. Preheat trains conceived with the wrong flow scheme or. Plate heat exchangers and their design theory r k shah and w w focke. Heuristic rules were proposed to identify the best control strategy for a heat exchanger network. Heat exchanger network design, monitoring and optimization. This paper proposes an optimization model for heat exchanger network synthesis that includes a detailed design for each heat exchanger of the network. Interfacing heat exchanger network synthesis and detailed heat exchanger design. A heat exchanger network obtained using the pinch design method is a network where no heat is transferred from a hot stream whose temperature is above the pinch to a cold stream whose temperature is below the pinch. Simple or composite wall of some kind divides the two. Heat leaves the warmer body or the hottest fluid, as long as there is a temperature difference, and will be transferred to the cold medium. Based on the matches made, the new heat exchanger network configuration is decided.

Effectiveness and lmtd correction factor of the cross flow exchanger. A literature very wellknown stagewise superstructure is used, but isothermal mixing assumption is not made and a timesharing procedure is adopted. Simulation of heat exchangers and heat exchanger networks. Introduction the heat exchanger network hen design method is a. Two examples are provided to illustrate this procedure. In fact, fouling has been recognised for a long time, and research on heat exchanger fouling was conducted as early as 1910 and the first practical application of this research was implemented in the 1920s. At either side of the pinch, the divided heat loads on each stream are combined and then matched according to a systematic procedure derived from simple pinch analysis. Examples are water cooling towers and jet condensers in. The heat exchanger network hen synthesis problem based on entransy theory is analyzed. A heat exchanger is a component that allows the transfer of heat from one fluid liquid or gas to another fluid. Effectiveness and lmtd correction factor of the cross flow. Chapter 3 literature survey heat exchanger network and. Heat exchanger network synthesis hens is an important field in thermal engineering and has been the subject of a considerable amount of research over the past 50 years.

Heat exchanger is a device for transferring heat from one medium to another. A procedures manual was created for the doublepipe heat exchanger. The theories of transient heat transfer in doublepipe heat exchangers were explained and followed by literature correlations. It is a device that is used to transfer thermal energy from one body or fluid stream to another. The key decision variables are the cleaning of a specific heat exchanger in a specific period. Heat exchangers are used to transfer heat between two sources. Heat exchanger networks are designed to reach energy targets obtained by the problem table analysis with the help of the pinch design method. Then is a heat exchanger network synthesis program that was developed by professor knopf at louisiana state university knopf,1989. A shell and tube heat exchanger is a class of heat exchanger. Plate heat exchanger, how it works working principle hvac industrial engineering phx heat transfer duration.

Sep 26, 2012 use the temperature interval method to determine minimum energy requirements in designing a heat exchanger network. Nls s 1 wherenisthenumberofunits,n s isthetotalnumberofhotand cold streams as well as utilities, l is the number of independent loops, and s is the number of independent subsystems that can. Unit operations lab heat exchanger 12 theory notes 1. In this method, a global heat exchanger is divided into several sub heat exchangers in seriesandparallel arrangement 14. In another recent study of the optimization of the shell and tube heat exchanger, 2 proposed a method, motivated by constructed theory. Pdf interfacing heat exchanger network synthesis and. Good practice for heat exchanger selection and design.

So, we are back again in our course on heat exchanger. Heat transfer theory heat can be transferred by three methods. In this chapter we will examine the basic theory of heat exchangers and consider many applications. The objective function serves to minimize the operating cost. Heat exchangers are devices used to transfer heat between two or more. The process streams are drawn as horizontal lines, with the stream numbers shown in square boxes. Synthesis of optimal heat exchanger networks s k rastogi j shankara and j srinivasan. By projecting temperature information onto a fixed discrete temperature grid, the model remains linear even under variable. Keywords heat exchanger networks, degrees of freedom analysis, control strategy determination. Heat exchanger network optimization and controllability using.

Literature survey heat exchanger network and mass transfer equipment network 3. Heat exchanger network synthesis with detailed heat exchanger. Heat exchangers may be classified according to transfer process, construction, flow arrange ment, surface compactness, number of fluids and heat transfer mechanisms as shown in fig. A heat exchanger follows this principle in its endeavour to reach equalisation. Pdf step by step for designing an optimum heat exchanger.

Hence, the design of such networks is an important aspect of chemical process design. To reduce the temperature of a hot fluid by means of a cooler fluid 3. They will also calculate the number of tubes needed for a shell and tube heat exchanger and to calculate the pipe length needed for a double pipe heat exchanger. Designing a heat exchangers network hen by application of pinch analysis is an effective technique for energy integration. Starts with the introduction of heat exchangers and is concerned with the detailed classification of heat exchangers according to contact types, surface compactness, number of fluids, flow arrangement and. The output of this model is the optimal cleaning schedule. Heat exchanger network synthesis provides engineers, designers, and industrial practitioners with a howto manual for understanding the methodology for conserving energy through process integration. Ht1 introduction to engineering heat transfer these notes provide an introduction to engineering heat transfer.

The transport of energy in chemical plants and petroleum refineries is accomplished by means of heat exchanger networks hens. With a plate type heat exchanger, the heat penetrates the surface, which separates the hot medium from the cold one very easily. Heat exchanger seminar ppt with pdf report heat exchangers are found widely scattered throughout the food process industry. Efficiency analysis of heat exchangers and heat exchanger. In this section, economic simulation of a sample hen was performed to monitor e of all hes. On the minimum number of units in heat exchanger networks miguel bagajewicz, and gary valtinson university of oklahoma, 100 e.

However, some constraints depend on the statistical regression results for each heat exchanger in the network. Designing a crude unit heat exchanger network a welldesigned crude and vacuum unit cduvdu heat exchanger network is essential to meet product yield, product quality, unit reliability and crude processing flexibility objectives when processing heavy crudes. Made by faculty at the university of colorado boulder department of chemical and. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural. Aug 31, 2016 in this paper an optimization model is presented for the synthesis of a heat exchanger network hen for multiperiod operations. Heat transfer processes set limits to the performance of aerospace components and systems and the subject is one of an enormous. Simultaneous process and heat exchanger network synthesis.

Optimizing cleaning schedules of heat exchanger networks. Pinch analysis is a methodology for minimising energy consumption of chemical processes by calculating thermodynamically feasible energy targets or minimum energy consumption and achieving them by optimising heat recovery systems, energy supply methods and process operating conditions. Rev 01 a l ling rev 03 viska mulyandasari checked by. It is therefore possible to heat or cool fluids or gases which have minimal energy levels. Boundary layer theory 46 thermal boundary layer 49 dimensionless parameters 50. Radiation heat transfer radiation differs from conduction and convection heat t transfer mechanisms, in the sense that it does not require the presence of a material medium to occur. Pinch analysis combined with exergoeconomic analysis was used for determining optimal minimum approach temperature.

It integrates the networks of heat exchangers, boilers, condensers and furnaces for best energy utilization. Analysis of heat exchanger network for temperature fluctuation. In a 2 cold stream, 2 hot stream and 2 stages network problem. The basic process heat and material balance is now in place, and the heat exchanger network the third layer can be designed.

Streams are matched and heat exchangers are added until all required heat transfer is accomplished. The natural laws of physics always allow the driving energy in a system to flow until equilibrium is reached. Heat exchangers jordan university of science and technology. Temperature distributions and heat exchanger effectiveness. Radiation energy is transferred by electromagnetic radiation. Heat exchanger selection and sizing engineering design guideline author. Energy transfer by radiation occurs at the speed of light and suffers no attenuation in vacuum. The exchange can take place between a process stream and a utility stream cold water, pressurized steam, etc, a process stream and a power source electric heat, or between two process streams resulting in energy integration and reduction of external heat sources. However, the term is commonly used to equipment in which two process streams exchange heat with each other. Jul 01, 2016 heat can flow only from hotter to cooler fluids, as per the second law of thermodynamics. In addition, we will examine various aspects of heat exchanger design and analysis. Subscripts h and c refer to the hot and cold fluids, respectively, and subscripts i and o refer to the inlet and outlet of the heat exchanger, respectively. The efficiency of all heat exchangers is determined from a single algebraic expression.

The cold streams are drawn at the bottom, and flow from right to left. The approach is based on the use of genetic algorithms to determine the heat exchanger network. Targets can also be set for the utility loads at various levels e. Suppose, the modular heat exchangers sizes available are 10, 50, 100, 200, 500. According to the characteristics of entransy representation of thermal potential energy, the entransy. This implies that the maximum number of sizes mse of heat exchangers available is 6. R sekulib university of kentucky introduction a heat exchanger is a device that is used for transfer of thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a. Heat exchanger network pinch point posted in student. A heat exchanger is a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. A heat exchanger is a system used to transfer heat between two or more fluids. Download the excel spreadsheet templates in this article to make preliminary heat exchanger design calculations. The heat exchanger theory article provides you with information about the fundamentals of a heat exchanger and will be useful for a heat exchanger inspection concept to describe this theory, you may know we need to heat or to cool process fluids in industrial plants to facilitate process reactions. Each individual heat exchanger in the network can be designed by the methods. It uses pinch technology as the basis for designing a network.

The method is adapted to allow tradeoffs between energy, number of units, and capital. Calculate the required heat transfer area based on values needed. It is the most common type of heat exchanger in oil refineries and other large chemical processes. Cost of the exchanger is directly related to the heat exchange area. We now show a complete analysis of an atmospheric crude. Request pdf heat exchanger network optimization and controllability using design reliability theory for a given heat exchanger network hen it is often necessary to determine its behaviour to.

Heat transfer surface area internal and external surface area, respectively, of a heat exchanger tube target for minimum heat transfer area in a heat exchanger network constant in capital cost equation for heat exchangers, equation 8. One example is the heating of the earth by the sun. The thermal resistance network associated with this heat transfer process involves two convection and one conduction resistances, equating both. This paper addresses the control of heat exchanger networks and it shows the importance of dynamic simulations in the synthesis of workable control structures. The process utility system may be a part of a centralised sitewide utility system. A heat exchanger networks hen is an arrangement of heat exchangers.

The same procedure is done below the pinch, except that the criterion is 9. In this chapter we will examine the basic theory of heat exchangers. The remaining heating and cooling duties are handled by the utility system the fourth layer. More discussion on all components of the software will be presented in the context. The heat exchanger network chemical engineering projects. Oct 11, 2018 plate heat exchanger, how it works working principle hvac industrial engineering phx heat transfer duration. Heat exchanger network optimization for multiple period. The heat exchanger must be isolated from system vibrations using flexible piping connections and isolation pads on the mounting feet. Heat exchanger networks may include splitters, heat exchangers, and coolers. Heat exchanger network optimization and controllability. The minimum number of units in a network has been proposed to be obtained using a very simple formula using. Counter flow heat exchangers are the most efficient of the three types. A minlp problem is solved separately for each period of operation. The model takes into account the optimization of the exchanger units and their geometric and operational constraints from the synthesis stage.

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