what is ntu in heat exchanger

Nuclear Reactor Engineering: Reactor Systems Engineering, Springer; 4th edition, 1994, ISBN: 978-0412985317, W.S.C. Please watch: "PSU through GATE 2018 by Mech Zone" https://www.youtube.com/watch?v=_SwwKGhvv9o -~-~~-~~~-~~-~- LMTD, NTU, Effectiveness and … (Eq 6)  $q_{max}=C_{min}(T_{h~insert}-T_{c~inlet})$. … In physical terms, the heat exchanger effectiveness can be defined as the ratio of actual heat transferred to the theoretically maximum possible heat transfer between the two sides of heat exchanger. When the heat transfer surface area A of the heat exchanger is known, but the outlet temperatures are not, the effectiveness-NTU method is the preferred method. Calculate the total heat transfer rate. Another approach introduce the definition of heat exchanger … 1) You may use almost everything for non-commercial and educational use. The performances of a heat exchanger can be readily evaluated if the number of transfer … The LMTD method is convenient … Now that the capacity rate of the fluids in the heat exchanger have been determined the NTU value can be found. As heat is transferred from one fluid to another fluid in a heat exchanger one fluid will rise in temperature while the other fluid falls in temperature. On the other hand the temperature graph below shows the temperature profile of the two fluids for simple two pipe heat exchanger when the flow of the two fluids is a counter flow. Another method that can be used is the effectiveness NTU method. Heat capacity ratio of the heat exchanger in the P-NTU method, calculated with respect to stream 1 (shell side = 1, tube side = 2) [-] Ntp: int. Cmin is the capacity rate of the fluid with lowest capacity rate while Cmax is the capacity rate of the fluid with the highest capacity rate. 11.1 Introduction. In the introduction article on heat exchangers the heat transfer between the two fluids was expressed as the following equation. J. R. Lamarsh, A. J. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 0-201-82498-1. In heat exchanger … Glasstone, Sesonske. Invent. Paul Reuss, Neutron Physics. From the two temperature graphs you can see how the temperature of the fluids will change as it passes through the heat exchanger. Addison-Wesley Pub. The simplest heat exchanger is … Li-Zhi Zhang, in Conjugate Heat and Mass Transfer in Heat Mass Exchanger Ducts, 2013. Calculate the capacity rate ratio. To define the effectiveness of a heat exchanger, we must first determine the maximum possible heat transfer rate, qmax, for the heat exchanger. Fundamentals of Heat and Mass Transfer, 7th Edition. Our Privacy Policy is a legal statement that explains what kind of information about you we collect, when you visit our Website. It signifies that the heat transfer capacity of a given heat exchanger. January 1993. Heat exchangers are usually analyzed using either the Logarithmic Mean Temperature Difference (LMTD) or the Effectiveness – Number of Transfer Units (ε-NTU) methods. Calculate the outlet temperatures. Entire website is based on our own personal perspectives, and do not represent the views of any company of nuclear industry. However the LMTD is valid only for heat exchanger … It is the most common type of heat exchanger in oil refineries and other large chemical processes, and is suited for higher-pressure applications. Heat Exchanger Effectiveness (NTU method) If more than one of the inlet and outlet temperature of the heat exchanger is unknown, LMTD may be obtained by trial and errors solution. K. O. Ott, W. A. Bezella, Introductory Nuclear Reactor Statics, American Nuclear Society, Revised edition (1989), 1989, ISBN: 0-894-48033-2. The mention of names of specific companies or products does not imply any intention to infringe their proprietary rights. NTU = ( UA ) / (C)min… Determine NTU. To use the equations you will need to first determine the NTU value, N, of the heat exchanger and you will need to find capacity rate ratio, C, of the heat exchanger.eval(ez_write_tag([[250,250],'sbainvent_com-large-mobile-banner-1','ezslot_1',116,'0','0'])); (Eq 9)  $ε=\frac{1-e^{-N(1-C)}}{1-Ce^{-N(1-C)}}$, (Eq 10) $ε=1-exp\left[ \frac{e^{NCn}-1}{Cn} \right]$, (Eq 11)  $ε = \left[ \frac{1}{1-e^-N} + \frac{C}{1-e^{NC}} – \frac{1}{N} \right]^{-1}$, (Eq 12) $ε = \frac{1}{C}\{1-exp[-C(1-e^{-N}) ] \}$, (Eq 13)  $ε=1-exp\left\{-\frac{1}{C} [1-e^{-NC}] \right \}$, (Eq 14) $ε = 2 \left\{ 1+C+(1+C^2)^{1/2} \left(\frac{1+e^{-N(1+C^2)^{1/2}}} {1-e^{-N(1+C^2)^{1/2}}} \right) \right\}^{-1}$, Privacy Policy | Terms & Conditions | Contact Us | Prepared by S. B. Amirault Founder of S.B.A. The heat-exchanger effectiveness, , is defined by = q/q max, (12) where q is the actual rate of heat transfer from the hot to cold fluid, and q max represents the maximum possible rate of heat transfer… Oten times, another variable is defined called the NTU (number of transfer units): NTU = UA/Cmin. ISBN: 9780071077866. Convective heat transfer from the outer tube wall to the outside fluid. Calculate the heat transfer surface area. ISBN: 9781118137253. Thermal Engineering. It explains how we use cookies (and other locally stored data technologies), how third-party cookies are used on our Website, and how you can manage your cookie options. NTU= 4. When NTU … A heat exchanger is a device used to transfer heat between two or more fluids. The capacity rate ratio of the heat exchanger can be now be found using the following equation. EDP Sciences, 2008. U.S. Department of Energy, Nuclear Physics and Reactor Theory. Lt Ds B Figure 5.20 Dimensions of 1-1 shell-and-tube heat exchanger Dimensions of Shell-and-Tube Heat Exchanger … To find the maximum heat transfer of the heat exchanger equation 1 could be used or the equation below could be used. It does not consider how the two fluid temperatures will change as they pass through the heat exchanger. Resulting in less heat transfer and higher outlet fluid temperatures, which … DOE Fundamentals Handbook, Volume 2 of 3. NTU means number of transfer units. Main purpose of this project is to help the public learn some interesting and important information about engineering and thermal engineering. ISBN: 978-2759800414. The Number of Transfer Units (NTU) Method is used to calculate the rate of heat transfer in heat exchangers (especially counter current exchangers) when there is insufficient information to calculate the Log-Mean Temperature Difference (LMTD). U.S. Department of Energy, Thermodynamics, Heat Transfer and Fluid Flow. McGraw-Hill Education, 2011. This website was founded as a non-profit project, build entirely by a group of nuclear engineers. Clarendon Press; 1 edition, 1991, ISBN: 978-0198520467, G.R.Keepin. The heating is to be accomplished by passing hot engine oil, which is at 160°C, through the shell side of the exchanger… This can be found by using the equation below. The information contained in this website is for general information purposes only. 2) You may not distribute or commercially exploit the content, especially on another website. Co; 1st edition, 1965. Robert Reed Burn, Introduction to Nuclear Reactor Operation, 1988. you would see LMTD method, a solution can be found graphically using an ε-NTU curve for the actual heat exchanger configuration. Finally, the effectiveness of the heat transfer needs to be determined. NTU signifies how much number of units of heat, the given heat exchanger is capable of transferring from one fluid to other. The recommended approach is the effectiveness or -NTU method. In the introduction article on heat exchangers the heat transfer between the two fluids was expressed as the following equation. However, this method requires you to know what the input and output temperature of the fluid is. In NTU method (Number of Transfer Units method) the effectiveness is the ratio between the actual heat transfer rate and the maximum possible heat transfer rate. The greater the value … Depending on how large that change is will effect the accuracy of equation 1. Effectiveness – NTU Method. Below is a list of equations that apply to different situations. This quantity is called the number of transfer units NTU and is expressed as. ANSYS FLUENT provides two heat exchanger models: the macro (ungrouped and grouped) models and the dual cell model. Calculate the length of the tube or heat exchanger Number of transfer units ( NTU ) is calculated using following equation : NTU = U.A/ C Min.