PLATE HEAT EXCHANGER

VIKAS SAINI B.Tech(ME)

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.

Types Of Heat Exchangers

Double pipe heat exchangerShell and tube heat exchangerPlate heat exchanger

Plate and shell heat exchangerPlate fin heat exchangerSpiral heat exchangers

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.

Parts & Their Function

1. FrameThe 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

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.

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.

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.”

Why Plate Heat Exchanger?

High heat transfer areaHigh heat transfer coefficientCompact and has lower floor space requirements.By increasing the number of plates the area of heat

exchange can be increasedMost suitable type heat exchangers for lower flow

rates and heat sensitive substances.Multiple duties can be performed by a single unit

Classification of Plate Heat Exchanger

Gasketed plate heat exchangers (plate and

frame heat exchangers)

Brazed plate heat exchangers

Welded plate heat exchangers

1. Plate and frame heat exchangers

.

Plate and Frame Heat Exchanger

Most common type of PHEConsists of plates and gasketsMaterials: stainless steel, titanium and non-metallicOperation limits:

- temperatures from -35°C to 220°C- pressures up to 25 bar- flow rate up to 5000 m3/h

2. Brazed Plate Heat Exchanger (PHE)

Brazed Plate Heat Exchanger

Operates at higher pressures than gasketed unitsMaterials: stainless steel, copper contained brazeOperating limits:

- From -195°C to 200°C- Pressures up to 30 bar

It is impossible to clean. The only way is by applying chemicals.

3. Welded Plate Heat Exchanger (PHE)

Welded Plate Heat Exchanger

Plates welded together to increase pressure and temperature limitsMaterials: stainless steal and nickel based alloys. Can be made

with copper , titanium or graphiteOperation Limits:

- temperature limits depend on the material- can tolerate pressures in excess of 60 bar

BENEFITS OFFERED BY PLATE HEAT EXCHANGERS

Lightweight: The PHE unit is lighter in total weight than other types of heat exchangers.

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, maintenance any time.

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.

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.

Fouling

Particulate fouling or siltingSolid particles are deposited on the heat transfer surface

Biological foulingDeposition and growth of organism on surfaces

Chemical reaction foulingArises from reactions between constituents in the process fluids

Freezing or solidification foulingOccurs when the temperature of a fluid passing through a heat exchanger becomes too low

ConclusionPlate heat exchangers are available in a wide variety of

configurations to suit most processes heat transfer requirements.

Lower capital cost, reduced plant size, and increased safety are typical of the benefits arising from the use of PHEs.

Plate heat exchangers can replace some normal size heat exchangers bringing advantages and performance.