To understand the basic operation of heat exchangers. Base your calculation on the outside area of the inside pipe. 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. Heat exchanger analysis using effectiveness ntu method. With eri corporation this process become understandable and simple. A procedure for use of the equipment and the software was outlined.
Depending on the degree of details availableneeded, the calculations might be simple or. The results of heat transfer experiments show that the shellside heat transfer coefficient of the improved heat exchanger increased by 18. Lmtd for counter flow heat exchanger heat exchanger heat. It depends on heat exchanger arrangement and value of ch and cc. It is designed to ensure the ratio of heat recovery and pressure loss is at an optimum, i. The added resistance to heat transfer caused by corrosion is called fouling. Equation is used when simple counter or cocurrent flows exist. The second heat transfer process is convection, or heat transfer due to a flowing fluid. Heat exchangers are typically classified according to flow arrangement and type of construction. Log mean temperature difference lmtd calculation for a shell and tube exchanger for countercurrent, cocurrent flow checalc chemical engineering calculations to assist process, plant operation and maintenance engineers. Counter flow heat exchanger international journal of innovative. Pdf design of heat exchangers exchanger design methodology. However, it is possible to obtain q by combining eq. The simplest heat exchanger is one for which the hot and cold fluids move in the same or opposite directions.
A shellandtube heat exchanger must be designed to heat 2. Fire the boiler as per instructions in the boiler manual. Counterflow heat exchanger for crossflow and shellandtube heat exchangers. Counterflow heat exchanger an overview sciencedirect. Chemical engineering calculations to assist process, plant operation and maintenance engineers. Download the excel spreadsheet templates in this article to make preliminary heat exchanger design calculations. Counter flow heat exchanger in counter flow heat exchangers the fluids enter the exchanger from opposite ends. The major types of heat exchanger include double pipe, shelltube, plate and shell, plate fin, and phase change heat exchangers. Consider a parallelflow or counterflow heat exchanger consisting of fluid 1, fluid 2, and the wall separating these two fluids. Theoretical and numerical analysis of counterflow parallel. Pdf design and development of parallel counter flow heat.
Temperature distributions in a counterflow heat exchanger of singlephase fluids temperature distributions in a parallelflow heat exchanger of singlephase fluids evaluation of an average temperature difference is necessary for calculation of heat transfer rate. Fouling factor, r 1udirty 1uclean forced convection in coiled tube heat exchangers. A schematic of a counterflow heat exchanger is shown in figure 18. Overall heat transfer coefficient essential requirement for heat exchanger design and performance calculations contributing factors convection between the two fluids and solid conduction of the solid separator potential use of fins in one or both sides timedependent surface fouling general expression c and h cold. Asee 2014 zone i conference, april 35, 2014, university of. Compact vex340 unit with energyefficient counter flow heat. Calculate the required heat transfer area based on values needed. John richard thome ltcm sgm epfl heat transfer heat exchanger design 1er mars 2008 6 41 the cross. In process calculations, the main objectives of heat exchanger calculations are to determine the heat duty amount of energy to be transferred, temperature changes within the exchanger, and pressure drops. 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. Sometimes determining sufficient excess heat transfer area or additional heat exchangers to take into account the effects of rapid fouling processes can make up a significant part of the whole heat exchanger design problem. The temperature differential is nowhere near as high as at the start of the parallel heat exchanger. The heat exchange duty a llows calculation of the log mean. Heat exchanger analysis 3 the lmtd method for a singlepass counterflow heat exchanger the design value ua follows from ua q.
Analysis of a counter flow parallelplate heat exchanger. 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. Hence, they are the most widely used heat exchangers. In addition, the overall heat transfer equation for the exchanger must be solved simultaneously. For an area of m2 and overall heat transfer coefficient of 340 wm2. Fluid temperature changes along channel centerlines. Heat exchanger calculations and design with excel spreadsheet. Overall heat transfer coefficient for doublepipe heat. Although the helical passages increase the heat transfer and reduce the size of the device, 3d print build constraints mandate that the passages are constructed with a lean angle for structural support that also increases. However, lmtd method can be extended to more complex heat exchanger designs e. The vex340 counter flow heat exchanger is made of aluminium. In other words, heat exchangers are used in both cooling and heating processes. Amjed ahmed example 1 in a counter flow heat exchanger, water is being chilled by a sodium chloride brine. A slight variation of a doublepipe heat exchanger is a tripletube heat exchanger, shown in figure 4.
Computer modeling of heat balance in counterflow tube. Figure 9 represents the directions of fluid flow in the parallel and counterflow exchangers. The software gives the possibility to make choice of heat exchanging according to your individual demands. Tlm the f correction factor is found from design graphs. Calculates the length of a concentric counterflow heat exchanger using the same parameters as in sizing a heat exchanger. Calculate the overall effectiveness of this heat exchanger considering both sections. The fluid velocity, reynolds number, overall heat transfer coefficient, baffle spacing, number of baffles, pressure drop, lmtd, helix angle of tubes. Tlm however, in process engineering practice most heat exchangers are not of this type, having several shell passes and tube passes. The overall heat transfer coefficient of the exchanger is 300 wm2 k, and the area for heat transfer is 15. Overall heat transfer coefficient for doublepipe heat exchanger. Computer modeling of heat balance in counterflow tube heat. For these designs a correction factor f is applied, using. For a parallelflow heat exchanger, n 0, and for a counterflow heat exchanger, n 1.
What is parallelflow and counterflow heat exchanger. Epfl heat transfer heat exchanger design 1er mars 2008 22 41. Counter flow heat exchangers are the most efficient of the three types. Temperature courses in the counterflow heat exchanger we have used the computed analytical solutions for simulation of fluids heating and cooling. Heat exchanger problem calculation lmtd and effectiveness. The fluid velocity, reynolds number, overall heat transfer coefficient, baffle spacing, number of baffles, pressure drop, lmtd, helix angle of tubes plays very. A counterflow heat exchanger is one in which the direction of the flow of one of the working fluids is opposite to the direction to the flow of the other fluid. Pdf design and development of parallel counter flow. Then we would have to calculate q from ua lmtd and. Counter flow heat exchangers provide the maximum heat transfer rate for a given surface area. The principal disadvantages of the plate fin geometry are.
Counterflow heat exchanger an overview sciencedirect topics. Cfd analysis and performance of parallel and counter flow in. The results were compared between each model and between parallel and counter flow with fouled piping. T this temperature difference only depends on inlet temperatures hot side. To demonstrate the basic equations of heat exchanger operation. This means that as the hot fluid enters from the right, it cools against the already warmed up cold fluid from the left.
Calculate the required heat transfer rate, q, in btuhr from specified information about fluid flow rates and temperatures. Compact vex340 unit with energyefficient counter flow. Conjugate counterflow heatexchangers are widely used in thermal and. Note that in a counterflow heat exchanger the outlet temperature of the cold fluid can exceed the outlet temperature of the hot fluid but this cannot happen in a parallel flow system. In convection heat transfer, the heat is moved through bulk transfer of a nonuniform temperature fluid. Background a heat exchanger is a heat transfer device whose purpose is the transfer of energy from one moving fluid stream to another moving fluid stream. The double pipe heat exchanger is one heat exchanger pipe inside another larger pipe for either counter flow or parallel flow pattern. The flow in a heat exchanger can be arranged as parallel flow, counter flow, and cross flow. Rotary, crossflow, counterflow plate heat exchanger calculation implemented by eri corporation s.
This heat exchanger consists of two concentric pipes of different diameters. Pdhonline course m371 2 pdh shell and tube heat exchangers. 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. 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 heat exchanger effectiveness for parallel flow, counterflow, and crossflow is plotted in figures 5. Often manufacturers choose to present heat exchanger performance in. A heat exchanger is a device used to transfer heat between two or more fluids. Aug 26, 2002 a procedures manual was created for the doublepipe heat exchanger. Temperature profiles in a counterflow and b parallel flow single pass heat exchangers. Effectiveness of platetype heat exchangers is between 45% and 65%, as compared to 60% and 80% for rotary regenerators heinrich, and franzke, 1993. It is evident a good accordance of both methods of the heat transfer computation. John richard thome ltcm sgm epfl heat transfer heat exchanger design 1er mars 2008 20 41. Asee 2014 zone i conference, april 35, 2014, university.
Calculate the heat transfer area of the double pipe heat exchanger in the lab. In a counter flow heat exchanger, water is being chilled by a sodium chloride brine. Calculation of convection heat transfer coefficient h after calculating nusselt no. Turbulent flow was also analyzed during the development of the heat exchangers to determine its effect on heat transfer. Balanced counter flow heat exchanger assuming and cc, then the lmtd becomes undefined as. In this type of heat exchanger, product flows in the inner annular space, whereas the heatingcooling medium flows in the inner tube and outer annular space. 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. In a parallel flow exchanger, both fluids in the heat exchanger flow in the same direction.
Cfd analysis and performance of parallel and counter flow. If you are a student using this manual, you are using it without permission. Although the helical passages increase the heat transfer and. Parallel and counter flow designs heat exchangers engineers. Make an initial estimate of the overall heat transfer coefficient, u, based on the fluids involved. The oil provides an average convection coefficient ho 400 wm2k on the outside of the tubes.
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