Plate type heat exchanger

brief introduction about PHEx & its types, benefits,limitations etc.

1. Introduction A  heat exchanger  is a piece of equipment built for efficient heat transfer from one medium to another. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing and sewage treatment. In heat exchangers, there are usually no external heat and work interactions. Common examples of heat exchangers are shell-and- tube exchangers, automobile radiators, condensers, evaporators, air preheaters, and cooling towers.

2. Types Of Heat Exchangers

3. 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 .

4. Parts & Their Function 1. Frame The frame is made up of thick steel pressure retaining parts, the fixed cover and the movable cover, that when pulled together with the tightening bolts form the pressure retaining structure for the plates / plate pack . The carrying bar and guide bar act as a carrier and guide to both the plates and the movable cover

5. 2. Plates The heat exchanger plates, which make up the heat transfer surface, are clamped between two plates of steel with the use of the tightening bolts. The heat exchanger construction allows a plate heat exchanger to be easily opened for inspection and cleaning.

6. 3. Gaskets Each plate has a gasket that produces a sealing and channel system through the entire plate pack in which the two heat exchanging media flow in a counter-current direction. The circular portion of the gasket stops the fluid from going across the heat transfer plate and sends it to the next open channel. The remaining portion or field gasket directs the opposing fluid across the heat transfer surface.

7. 4. Flow Arrangement The heat transfer plates with gaskets are arranged in an alternating pattern of left hand flow and right hand flow to direct the fluids in an opposing direction within the heat exchanger. The completed assembly of all the plates and gaskets is called the “plate pack.”

8. 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 unit

9. Classification of Plate Heat Exchanger

10. 1. Plate and frame heat exchangers .

11. Plate and Frame Heat Exchanger Most common type of PHE Consists of plates and gaskets Materials: stainless steel, titanium and non-metallic Operation limits: - temperatures from -35°C to 220°C - pressures up to 25 bar - flow rate up to 5000 m 3 /h

12. 2. Brazed Plate Heat Exchanger (PHE)

13. Brazed Plate Heat Exchanger Operates at higher pressures than gasketed units Materials: stainless steel, copper contained braze Operating limits: From -195°C to 200°C Pressures up to 30 bar It is impossible to clean. The only way is by applying chemicals.

14. 3. Welded Plate Heat Exchanger (PHE)

15. Welded Plate Heat Exchanger Plates welded together to increase pressure and temperature limits Materials: stainless steal and nickel based alloys. Can be made with copper , titanium or graphite Operation Limits: - temperature limits depend on the material - can tolerate pressures in excess of 60 bar

16. BENEFITS OFFERED BY PLATE HEAT EXCHANGERS Lightweight : The PHE unit is lighter in total weight than other types of heat exchangers because of reduced liquid volume space and less surface area for a given application . High-viscosity applications : Because the PHE induces turbulence at low fluid velocities, it has practical application for high-viscosity fluids Saves space and servicing time : The PHE fits into an area one-fifth to one-half of that required for a comparable shell and tube heat exchanger. The PHE can be opened for inspection, mainte - nance . Lower liquid volume: Since the gap between the heat transfer plates is relatively small, a PHE contains only low quantities of process fluids. The benefit is reduced cost due to lower volume Lower cost: PHEs are generally more economical than other types of equivalent duty heat exchangers due to the higher thermal efficiency and lower manufacturing costs. Quick process control: Owing to the thin channels created between the two adjacent plates, the volume of fluid contained in PHE is small; it quickly reacts to the new process condition and is thereby easier to control .

17. LIMITATIONS OF PLATE HEAT EXCHANGERS The maximum allowable working pressure is also limited by the frame strength and plate deformation resistance. Commonly stated limits have been 300°F (149°C) and 300 psi Because of the narrow gap between the plates, high liquid rates will involve excessive pressure drops, thus limiting the capacity. Large differences in fluid flow rates of two streams cannot be handled. The gaskets cannot handle corrosive or aggressive media. Gaskets always increase the leakage risk The standard PHEs cannot handle particulates that are larger than 0.5 mm.

18. Fouling Particulate fouling or silting Solid particles are deposited on the heat transfer surface Biological fouling Deposition and growth of organism on surfaces Chemical reaction fouling Arises from reactions between constituents in the process fluids Freezing or solidification fouling Occurs when the temperature of a fluid passing through a heat exchanger becomes too low

19. Conclusion Plate heat exchangers are available in a wide variety of configurations to suit most processes heat transfer requirements. The advantages of PHEs, and associated heat transfer enhancement techniques, extend far beyond energy efficiency. Lower capital cost, reduced plant size, and increased safety are typical of the benefits arising from the use of P HEs. Plate heat exchangers can replace some normal size heat exchangers bringing advantages and performance.