When one of the fluid in Heat Exchanger is undergoing a change of phase like,. Statement I : A counter flow heat exchanger is more effective than a parallel flow heat exchanger. In the counter-flow heat exchanger, the hot fluid passes in the direction opposite to cold fluid. Using the LMTD method in order to find out the area of the heat exchanger, for the same mass flow rate and same inlet and outlet conditions of temperature the LMTD of the counter-flow heat exchanger will be more compared to the parallel flow heat exchanger as the flow is in opposite direction.
Start Learning. Answer Detailed Solution Below Option 3 : a counter flow heat exchanger. Explanation: In case of the counter-flow heat exchanger when the heat capacities of both the fluids are the same. It consists of a tube or pipe fixed concentrically inside a larger pipe or tube. It is used when flow rates of fluid are less and heat duty is small. For better heat transfer rate, fins are placed as it increases the heat transfer area.
The hot and cold fluid flow in alternate passages and thus cold fluid stream is surrounded by two hot fluid stream. Heat transfer capacity is enhanced by adding more plates in series. Tubes are relatively cheaper to fabricate than the shell body, therefore it is preferred to use corrosive or fouling fluid service on the tube side.
The viscous fluid is generally kept in the shell side. Get Started for Free Download App. Both the fluids at inlet are in their hottest state Both the fluids at exit are in their hottest state One fluid in hottest state and the other in coldest state Any combination possible depending heat exchanger design. Explanation: In counter-flow heat exchangers, the hot and cold fluids enter the heat exchanger at opposite ends and flow in opposite directions.
In counter-flow heat exchangers, the arrangement can be seen graphically. Parallel flow type Counter flow type Regenerator type Cross flow type. Explanation : Cross-flow : It is a cross-flow type. Parallel flow: When the fluids enter and leave at the same end as it is in concentric tube arrangement then the flow is known as parallel-flow.
Counterflow: In the counterflow configuration, the fluids enter and leave at the opposite end. In recent time, the thermal design is carried out by the process team using engineering software. However, the logic behind the calculations should be clearly understood. The shell and tube heat exchanger design calculations are based on initial selection of a preliminary exchanger configuration and certain initial decisions like.
Once the requirements are met, a process datasheet is developed indicating all process design parameters of shell and tube heat exchanger design. The following table Table-1 provides general guidelines for shell and tube side fluid allocation in a shell and tube heat exchanger:. High fluid velocities increases heat transfer coefficients and reduces fouling but causes erosion and increases pressure drop.
So velocity selected should be just enough to prevent settling of suspended soilds. Typical fluid velocities considered for the design of shell and tube heat exchangers are given the following table Table-2 :.
The most popular software used for thermal design of shell and tube heat exchanger are listed below. Mechanical design of shell and tube heat exchangers consist of calculation of shell thickness, flange thickness, etc. The following design guidelines can be followed:. Depending on user experience and manufacturer guidelines, shell and tube heat exchangers should be inspected at regular intervals. A shell and tube heat exchanger can fail by one or more of the following factors:.
Following preventive maintenance steps at regular intervals can reduce the risk of equipment failure. Following maintenance steps can be followed to enhance shell and tube heat exchanger performance:. I am a Mechanical Engineer turned into a Piping Engineer. I am very much passionate about blogging and always tried to do unique things.
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Congratulations Great presentation with very easy explanation to understand the fundamentals of heat exchanger Thank you. Very Nice Presentation. Thanks for a detailed information. Requesting you to also describe details related to its piping arrangement. Guidelines to be taken if the heat exchanger is located on the ground or on platforms above.
Hi Anup. Very Good presentation. Do you have a presentation on maintenance of shell tube heat exchangers? Thanks for this presentation. Do you know or have any write up that can help me to know the size of the heat exchanger that i can use for some specified inlet and outlet pressure and temperature. The study was carried out in the range of Reynolds number varying from 10 to in both the papers.
Liquid coolants used in the test were water and poly-alpha-olefin PAO , for which the Prandtl number ranges from 3 to They found that the Colburn factor for air is approximately twice the Colburn factor for the liquids at the same Reynolds number. The air model over predicts the heat transfer coefficient for liquids. The results of the two studies showed that the Prandtl number has a significant effect on heat transfer in OSF channel. Although Fig. The effects of fin geometries as heat transfer surface with larger JF factor has the better non-dimensional forms on heat transfer and pressure drop overall thermal—hydraulic characteristic.
The effect of flow were investigated, for this study 18 different OSFs were angle on f and j was studied and angle at which JF is used. Respective asymptotes for f and j were correlated by maximum was also determined. After the analysis two correlations Bhowmik et al. Results were compared from the data exchanger. Water was the heat transfer medium and the Re obtained by other researchers in the deep laminar and fully ranged from 10 to Fluent version 6.
A turbulent regions. Correlations can be acceptable when segregated solver was used to solve out the governing comparing the results of the expressions to the experimental integral equations for conservation of mass, momentum and data obtained by Kays and London.
Also it was indicated energy. Data Reduction Technique to Evaluate Fanning The setup consisted of RTD and thermocouples for Friction Factor and Colburn Factor temperature measurement, Coriolis mass flow meter to To study the pressure drop and heat transfer in an offset fin, measure mass flow rate. Constant heat flux was provided by Colburn factor and fanning friction factor can be calculated two 2 KW electrical heater. Two measures were taken to using following procedure [10]. The thermal hydraulic considered to calculate heat transfer coefficient of fluid.
Air models over U is calculated by predict the j factor for liquids. The Prandtl number have little effect on the Fanning friction factor. Shah, D. M ech. M anglik, A. Patankar, C.
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