Design Considerations for Plate Type Heat Exchanger
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A plate type heat exchanger consists of corrugated metal plates clamped together in a frame. Fluids flow between the plates, which have a high surface area and induce turbulence, allowing for efficient heat transfer. Key advantages are compact size, ability to handle low flow rates, and the option to perform multiple duties with one unit. Design involves selecting the number and dimensions of plates based on flow rates, properties of the fluids, and heat transfer correlations or manufacturer charts.
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Design Considerations for Plate Type Heat Exchanger
- 1. DESIGN CONSIDERATIONS FOR PLATE TYPE HEAT EXCHANGER Arun S CHEMICAL ENGINEERING
- 2. What is a plate type heat exchanger? It’s a type of Heat Exchanger which consists of many corrugated stainless-steel sheets separated by polymer gaskets and clamped into a steel frame •Plate heat exchangers transfer heat by placing thin, corrugated metal sheets side by side and connecting them by gaskets. •Flow of the substances to be heated and cooled takes place between alternating sheets allowing heat to transfer through the metal sheets.
- 3. Assembly Instead of pipe passing through chamber, there are two alternate chambers separated by a corrugated plate Plates are usually spaced by rubber gaskets The plates are pressed to form troughs at right angles to the direction of flow of liquid which runs through the channel Plates produce a large surface area ensuring maximum heat transfer The number and size of the plates are determined by the flow rate, physical properties of the fluids, pressure drop, and temperature Mainly two forms of corrugations are seen ◦ Intermating corrugations ◦ Chevron corrugations
- 4. The frame and the channel plates have portholes that allow process fluids to enter altenating flow patterns These narrow gaps and high number of contact points which change fluid flow direction combine to create a very high turbulence between the plates. For a liquid-liquid heat exchanger whose usual fluid velocity is 0.2 to 1 m/s, the Reynolds No will be< 2100, but due to the presence of corrugations the turbulent characteristics are achieved even at NRe say about 400-500. Evidence of Turbulent characteristics is obtained by measuring heat transfer coefficient which varies with 0.6 to 0.8 power of flow rate and pressure which varies with 1.7 to 2 power of the flow rate General Dimensions of PHE
- 5. Why Plate Heat Exchanger? High heat transfer area High heat transfer coefficient Compact and has lower floor space requirements. By increasing the number of plates the area of heat exchange can be increased Most suitable type heat exchangers for lower flow rates and heat sensitive substances. Multiple duties can be performed by a single un
- 6. Design using correlations From the APV heat transfer handbook- Design and Application of Paraflow- Plate Heat exchangers there are following correlations for PHEs: Where Np is the number of passages w is the width of the plate W is the mass flow rate G is the mass velocity
- 7. Design using charts Only limited design correlations are available for the design of Plate heat exchanger So the preliminary design is on the basis of certain charts by the manufacturers. As per designing of plate and frame filter press by Christopher Haslego, they introduced a set of certain charts which form the basis of preliminary design. The use of the charts were on the basis of following points: ◦ Applicable for liquid-liquid design ◦ Valid for only single pass units ◦ Thermal conductivity of wetted material is same as that of SS ◦ For fluids with viscosity between 100cP to 500 cP , the 100 cP line in the graph should be used.
- 8. A = q/U LMTDF. the number of plates from, N=A/Ap, where A, is the area of a plate
- 11. Plate Fin Type Exchanger
- 12. Limitations….. Cost factor is on the higher side as most of the parts are made of SS. Not suitable for liquids with high viscosity and suspended matters. Often Fouling in plates, leads to requirement of intermittent cleaning and this reduces the life of gaskets. Large difference in fluid flow rates cannot be handled.
- 13. Applications Widely used in diary and food processing industries A whole heat exchange network can be condensed to a plate heat exchanger Pasteurisation of milk uses the plate heat exchanger with three- four sections Also used in food and cosmetics industries.
- 14. References Perry’s Chemical Engineering Handbook ,8th Edition,Don.W.Green, Robert.H Perry Unit Operations of Chemical Engineering, Seventh Edition, Warren.L.McCabe, Julian.C.Smith Designing Plate and Frame Heat Exchanger, Christopher Haslego and Graham Polley