Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our User Agreement and Privacy Policy.

Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. If you continue browsing the site, you agree to the use of cookies on this website. See our Privacy Policy and User Agreement for details.

Successfully reported this slideshow.

Like this presentation? Why not share!

3,570 views

May. 04, 2016

No Downloads

Total views

3,570

On SlideShare

0

From Embeds

0

Number of Embeds

16

Shares

0

Downloads

327

Comments

0

Likes

7

No notes for slide

- 1. GASKETED PLATE HEAT EXCHANGER MME 9516 HVAC 1 PROJECT PRESENTATION BY - SALEEM MOHAMMED HAMZA (250873614)
- 2. OVERVIEW INTRODUCTION CONSTRUCTION FLOW PATTERN IN A PHE PLATES PLATE MATERIALS DESIGN LOGIC FOR HEAT EXCHANGERS MEAN FLOW GAP CHANNEL HYDRAULIC DIAMETER HEAT TRANSFER COEFFICIENT CHANNEL MASS VELOCITY PRESSURE DROP OVERALL HEAT TRANSFER COEFFICIENT HEAT TRANSFER SURFACE AREA
- 3. INTRODUCTION Heat exchangers are devices that provide the flow of thermal energy between two or more fluids at different temperatures without mixing with each other. A Plate Heat Exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. Applications: Power Plants Process Industries Chemical & Food Industries Air Conditioning & Refrigeration Waste Heat Recovery Space Application
- 4. CONSTRUCTION The main elements of plate heat exchanger (PHE) are fixed frame and compression plate, connecting ports, plates. The heat transfer surface is composed of series of plates with parts for fluid entry and exit in the four corners. The plate pack is tightened by means of either a mechanical or hydraulic tightening device. The warmer medium will give some of its heat energy through the thin plate wall to the colder medium on the other side. Leakage from the plates to the surroundings is prevented by using gaskets.
- 5. FLOW PATTERN IN A PHE The hot fluid flows through one channel and the cold through the other channel. The fluids flow between alternative passages formed between two packed plates. The flow through the plates is controlled by using gaskets. The corrugated pattern on the plate induces turbulence and thus enhances heat transfer.
- 6. PLATES Most of the commercial plates in PHE are chevron type, which have a surface corrugation pattern called washboard. In chevron type, adjacent plates are assembled such that the flow channels provides swirling motion to the fluids. This promotes turbulence by continuously changing flow direction and velocity of the fluids. The corrugated pattern has an angle 𝛽, which is referred to the chevron angle. The chevron angle is reversed on adjacent plates so that when plates are clamped together, the corrugations provide numerous contact points. The chevron angel varies between the extremes of about 65⁰ and 25⁰ and determines the pressure drop and heat transfer characteristics of the plate.
- 7. PLATE MATERIALS Plates are made from all malleable materials. The most common materials are stainless steel, titanium, titanium-palladium, aluminum, aluminum brass, etc. Plate material is chosen depending on the type of heat transfer fluids, type of application and the environment of use. For example: Titanium plates are used in sea water and marine applications to prevent corrosion of plates by the saline water. The table shows the different types of plate material and their thermal conductivity.
- 8. DESIGN LOGIC FOR HEAT EXCHANGER The corrugations increase the surface area of the plate as compared to the original flat area. This is expressed as the surface enlargement factor, φ which is defined as the ratio of the actual effective area as specified by the manufacturer, A1, to the projected plate area A1p Where, and ; Here DP is the port diameter. Φ is between 1.15 and 1.25. In practical application it is assumed to be 1.17
- 9. MEAN FLOW GAP Flow channel is the conduit formed by two adjacent plates between the gaskets. The mean channel spacing, b, is defined as 𝒃 = 𝒑 − 𝒕 where p is the plate pitch or the outside depth of the corrugated plate and t is the plate thickness. Channel spacing, b is required for calculating mass velocity and Reynolds number which is not usually specified for manufacturer. The plate pitch is not to be confused with the corrugation pitch. Plate pitch is found by: Where, Nt is total number of plates and Lc is compressed plate pact length.
- 10. CHANNEL HYDRAULIC DIAMETER The hydraulic diameter of the channel Dh is defined as, with approximation b<<Lw The heat transfer coefficient will strongly depend on the chevron inclination 𝜷 relative to flow direction. Heat Transfer and friction factor increases with 𝜷. Nusselt Number, 𝑁𝑢 = ℎ𝐷ℎ 𝑘
- 11. HEAT TRANSFER COEFFICIENT
- 12. CHANNEL MASS VELOCITY The channel mass velocity is given by: where, Ncp is the number of channels per pass and is obtained from where, Nt is the total number of plates and Np is the number of passes. Hence Reynolds number can be found using, 𝑅𝑒 = 𝐺 𝑐 𝐷ℎ 𝜇
- 13. PRESSURE DROP The total pressure drop is composed of the friction channel pressure drop ΔPc and the port pressure drop ΔPp. The friction factor, f is obtained from the above table and Leff is the effective length of the fluid flow path between inlet and outlet ports. The pressure drop in the port ducts Δpp can be roughly estimated as, Where, Therefore, Total pressure drop, ΔPT = ΔPc + ΔPP
- 14. OVERALL HEAT TRANSFER COEFFICIENT The overall heat transfer coefficient for a clean surface is and under fouling conditions (fouled or service overall heat transfer coefficient) is Where h and c stand for hot and cold streams respectively.
- 15. HEAT TRANSFER SURFACE AREA The required heat duty, Qr , for cold and hot streams is On the other hand, the actually obtained heat duty, Qf , for fouled conditions is defined as Where A is total area of effective plates, F is the fouling factor and the true mean temperature difference. ΔTm, for the counter flow arrangement is given as Where ΔT1 and ΔT2 are the terminal temperature differences at the inlet and outlet.
- 16. ADVANTAGES The gasket design minimizes the risk of internal leakage. Any failure in the gasket results in leakage to the atmosphere which is easily detectable on the exterior of the unit. Flexibility of design through a variety of plate sizes and pass arrangements. Efficient heat transfer, high heat transfer coefficient for both fluids because of turbulence and a small hydraulic diameter. Very compact (large heat transfer area to volume ratio) and low in weight in spite of their compactness. The heat losses are negligible and no insulation is required as only the plate edges are exposed to the atmosphere. Plate units exhibits low fouling characteristics due to high turbulence.

No public clipboards found for this slide

Be the first to comment