Here, we will cite only those that are immediately useful for design in shell and tube heat exchangers with sensible heat transfer on the shellside. The transport equation for heat exchange is expressed as qua. Duplex metal tube pps graphite tube fouling and scaling effects heat exchanger tube made of duplex metal and pps graphite after only 50 hours foulingresistant test with industrial process water. Full service for metalfree heat exchanger solutions. Heat transfer is a process is known as the exchange of heat from a hightemperature body to a lowtemperature body. Lienhardiv department of mechanical engineering university of houston houston tx 772044792 u. The corrugations of the plates and the small hydraulic diameter enhance the formation of turbulent flow, so that high rates of heat transfer can be obtained for the fluids. 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. These fluids arent either in contact with each other or mixed. Model definitionthe concept used to design a shellandtube heat exchanger is examined by exploring the working model of a straight, crossflow, one pass shellandtube heat exchanger. U a where u is the overall heat transfer coefficient and is the temperature change across the entire layer. The use of mathcad in a convective heat transfer course. In all of these machines, the heat exchanger is a key element.
At this stage the student can begin to apply knowledge of mathematics and computational methods to the problems of heat transfer. In the present section, effectivenessntu approach is used and the features of both approaches are explained. The heat exchanger effectiveness is defined as the ratio of actual heat transfer to the maximum possible heat transfer. Heat exchangers 73 individual thermal resistances of the system. Normally, some aspect in the production of heat exchangers is a task undertaken by chemical engineers since it deals with temperature, pressure, heat transfer. An understanding of the principles that govern heat transfer is essential to an. The use of the equipments is not limited to the experiments described. In heaters, in fridges, in boilers or in condensers of steam turbines. Heat transfer in a fully developed turbulent channel flow wh ctioa nntstw tlemalpuearetr 238 7. Heat transfer 1 heat transfer with phase change evaporators and condensers professor faith morrison department of chemical engineering michigan technological university heat transfer with phase change so far we have discussed heat transfer at a boundary due to a temperature difference between bulk temperatures x bw q ht t a. To generate the heat balance equations two methods are available, one is lmtd approach and other is effectivenessntu ap proach. The overall heat transfer resistance is based on a theoretical conductance ut and a theoretical area at. This would normally be expected to result in smaller, less expensive equipment for a given application. The tutorials are designed to bring the student to a level where he or she can solve problems ranging from basic level to dealing with practical heat exchangers.
Heat transfer in a fully developed turbulent channel flow wh utiomfrni w lah flueaxtl 240 7. In the continuity equation there is no pressure term and in the momentum equation there are only the. The thermal design of heat exchangers is directed to calculate an adequate. Modeling and design of plate heat exchanger intechopen. The overall heat transfer coefficient, u, is an approximate value. Therefore, the following heat equation must be used instead with the use of the latent heat transfer coefficient, h fg. Model of a plate heat exchanger has been described by a set of continuity, momentum and energy equations with a number of simplifying assumptions.
Then the overall heat transfer coefficient of a heat exchanger can be. The overall heat transfer equation for a heat exchanger must be written so that the variable conductance model can be investigated. Heat transfer tutorial 1 conduction this is the first of a series of tutorials on basic heat transfer theory plus some elements of advanced theory. Fluid engine oil sea water inlet temperature, c 65 20 outlet temperature, c 55 25 heat load, kw 117. Reason for heat exchangers a heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another hot and cold fluid. Mixing length closures and the temperature distribution. Heat exchangers jordan university of science and technology. This is the basic equation for heat transfer in a fluid. When a medium undergoes a phase change through the heat exchanger, the following variables behave as follows. Calculate the required heat transfer rate, q, in btuhr from specified information about fluid flow rates and temperatures. This will be covered and used in the following tutorials. In the rare occasion that the heat exchanger is a purely cocurrent parallel flow arrangement, f i and the lmtd is given by.
The rate of convection heat transfer is expressed by newtons law of cooling. Electronics cooling 55 all the basic differential equations can be derived by considering an element control volume inside the laminar region as shown in figure 8. Heat transfer 1 heat transfer with phase change evaporators and condensers professor faith morrison department of chemical engineering. Shell and tube heat exchangers play only a minor role in. In simulation of heat exchanger network, heat balance equations for each heat exchanger will be considered. Heat transfer laboratory annajah national university. Governing equations of fluid flow and heat transfer. This varying local heat transfer coefficient results in an uneven temperature distribution of the heat exchanger. Heat transfer, conduction, convection, radiation contents 1. The manual presents detailed descriptions of experiments.
When the fluid is free to move in the transverse direction, the crossflow is said to be. Shell and tube heat exchanger is designed by trial and error calculations. A major parameter for evaluating heat transfer coef. Lmtd, as seen from the heat exchanger equation, is that a larger lmtd permits a smaller heat exchanger area, a o, for a given heat transfer, q. Mtd mean temperature difference normally, this equation is solved for the surface area or a, since the heat load is known, and the overall heat transfer coefficient and the mtd can be calculated, based on known information. The overall heat transfer coefficient of the exchanger is 300 wm2 k, and the area for heat transfer is 15. The goal of heat exchanger design is to relate the inlet and outlet temperatures, the overall heat transfer coefficient, and the geometry of the heat exchanger, to the. International association of scientific innovation and. As we know heat is a kinetic energy parameter, included by the particles in the given system. Metalfree heat exchanger solutions technoform group. Heat transfer principals in electronics cooling mpe 635. Many of the classical equations of laminar free or forced convective heat transfer are second or thirdorder nonlinear ordinary differential equations, or systems of such equations, that are boundaryvalue problems. As you recall from undergraduate heat transfer, there are three basic modes of transferring heat.
U overall heat transfer coefficient, btuhrsq ft of a surface area, sq ft. Experiences using mathcad in a graduatelevel convective heat transfer course are described. This correction factor is equal to 1 if the heat exchanger has only one pass, otherwise it is described by the following equation. The arrangement and organization provide a convenient means of giving instruction on handling the equipments. Shell and tube heat exchangers basic calculations pdh online. In this example, two fluids pass through the heat exchanger. If the flow pattern is more complex such as the case with most shell and tube heat exchangers, then a correction factor term is used and the. Heat lecture 9 cm3110 1272015 5 geankoplis 4th ed, p285. Where, we get the a overall overall heat transfer area required from the heat transfer rate equation equation 1.
Design a double pipe heat exchanger with bare inner multitubes that can be used to cool engine oil with cold sea water. Mechanisms of heat transfer university of oklahoma. Pdf handout that help students for design of heat exchangers based on kerns. Combining each of these resistances in series gives.
Intermediate heat transfer, a second course on heat transfer for undergraduate seniors and beginning graduate students. The results presented in the transient state are caused by steps of temperature, heat flux or velocity, and in particular show the time evolution of the dynamic and thermal boundary layers, as well of the heat transfer coefficients. Instead of determining h we determine the nusselt number nu, which a dimensionless heat transfer coefficient. Make an initial estimate of the overall heat transfer coefficient, u, based on the fluids involved. Equation is used when simple counter or cocurrent flows exist. Od is the outside diameter of selected tube size l is the total tube length this equation is quite straight forward based on the geometry of the selected shell and tube heat exchanger. Minimum area ac, also referred to at the free flow area. Conduction is the transfer of heat through a medium by virtue of a temperature gradient in the medium.
As a system temperature increases the kinetic energy of. Those heat exchangers are designed to transfer heat and from this experiment, the basic concept of heat exchangers efficiency can be established and implemented in everyday applications. Emperical relations for free convention heat transfer. Heat exchanger network design, monitoring and optimization. Compute heat exchanger heat transfer factor for each exchanger in the network. Whenever it is difficult or not possible to determine the nusselt number analytically. Computer modeling of heat balance in counterflow tube. Whether it is called cooking, baking, drying, sterilizing or freezing, heat transfer is part of the processing of almost every food. A procedures manual was created for the doublepipe heat exchanger. Shellandtube heat exchangers can have multiple passes, such as 11, 12, 14.
The basic component of a heat exchanger can be viewed as a tube with one fluid running through it and another fluid flowing by on the outside. These assumptions also simplify the basic heatexchanger equations. The basic design equation and overall heat transfer coefficient the basic heat exchanger equations applicable to shell and tube exchangers were developed in chapter 1. Convection heat transfer arises when heat is lostgained by a fluid in contact with a solid surface at a different temperature.
Then the overall heat transfer coefficient of a heat exchan. For heat exchangers, a subclass of transient modeling technique was foundii i. Heat transfer formula definition, formula and solved. John richard thome ltcm sgm epfl heat transfer heat exchanger design 1er mars 2008 7 41.
If you are a student using this manual, you are using it without permission. Pdhonline course m371 2 pdh shell and tube heat exchangers. Since the exchanger is custom designed, the tube size can be smaller than nps 18 dn 6 mm that is the smallest size in table c. Consequently, up to 90% of the heat can be recovered, compared to only 50% in the case of shellandtube heat exchangers.
The overall heat transfer coefficient can be selected. It is evident a good accordance of both methods of the heat transfer computation. In a heat exchanger, heat is transported between two working fluids. Pdf heat exchanger lab experiment chemical engineering. Counterflow heat exchanger for crossflow and shellandtube heat exchangers. A 20 mm diameter copper pipe is used to carry heated water. Heat exchangers typical old fashion design 1 define duty. In process calculations, the main objectives of heat exchanger calculations are to determine the heat duty amount of energy to be transferred, temperature.
Selection of heat transfer models and fouling coefficients for shell side and tube side. Heat transfer rate equation has also been included in the energy balance equation to take care of phenomena occurring therein. Heat transfer equipment chapter 22 typesof heat exchangers 22. Consider two heat exchangers with series flow as shown in figure5. The selection of nusselt number to measure the heat transfer. Also note that radiative heat transfer and internal heat generation due to a possible chemical or nuclear reaction are neglected. Q ha t t w q h t t w m conv s conv s 2 the convective heat transfer coefficient h strongly depends on the fluid properties and. Figure5 heat exchangers with series flow arrangement. Computer modeling of heat balance in counterflow tube heat. In applications, to fully simulate the above process inside the tube demands a transient model of the systemi.
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