Compact Heat Exchangers, HARSHAD KANGANE.

M.E. Thermal.Sem- II.

AgendaWhat is a compact heat exchanger?TypesAdvantages and limitationsCost of heat exchangersCare to be takenEnvironmental AspectsConclusionReference

Basic DefinitionsA heat exchanger is a device built for

efficient heat transfer from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact.

What is a Compact Heat Exchanger?HT Area density greater than 700 m2/m3 for

gas or greater than 300 m2/m3 when operating in liquid or two-phase streams.

Highly efficient

Reduce volume, weight and cost

Types of CHEsPlate and frame heat exchangers: (PHE)PHE Countercurrent.mp4

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

Brazed Plate Heat Exchanger (PHE)

Brazed Plate Heat ExchangerOperates 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.

Welded Plate Heat Exchanger (PHE)

Welded Plate Heat ExchangerPlates welded together to increase pressure

and temperature limitsMaterials: 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

Spiral Heat Exchanger (SHE)Spiral HX for Liquid-Liquid.mp4

Spiral Heat Exchanger (SHE)Two long strips of plate wrapped to form

concentric spiralsMaterials: carbon steel, stainless steel and

titaniumOperation limits:

- Temperatures up to 400°C (depends on gasketed materials)

- Pressures up to 25 bar

Plate Fin Heat Exchanger (PFHE)

Plate Fin Heat Exchanger (PFHE)High area density and handles several

streamsMaterials: aluminum, corrosion and heat

resistant alloys, and stainless steel (available in titanium)

Operation limits:- Temperature limits depend on the material

- cryogenic temperature up to 100°C (aluminum)

- stainless steel up to 650°C- Pressures up to 100 bar for aluminum and 90 bar for stainless steel

Printed-circuit heat exchangers (PCHE)

Printed-circuit heat exchangers (PCHE)Flexibility of design and high strength offered

by techniques of constructionMaterials: Stainless steel 316, alloys, nickel

and titanium.The etched plates are stacked and diffusion

bonded together to make the core of HxOperating limits:

- temperature ranges from -200°C to 900°C- pressures up to 600 bar

Compact Shell-and-Tube Heat Exchanger

To increase surface area, this equipment has a large number of small diameter tubes

AdvantagesImproved energy efficiency

- Closer approach temperatures allows greater energy

transfer.Smaller volume and weight Higher efficiencyLower costMulti-stream and multi-pass configurationsTighter temperature controlPower savingsImproved safety

LimitationsLack of industrial awareness

Companies remain aware of technology of CHELimited choice

Particularly for high-pressureConservatism in the user industries

Process industries are reluctant to adopt what they may seen either as new technologies.

Susceptibility to fouling Perception that small passages are likely to foul.Expensive.Blockages can occurs very easily.

Cost of compact heat exchangers

Compact heat exchanger tend to be cheaper especially when their total installed cost is considered.

In some cases the materials used to manufacture is expensive, but when we consider the cost of unit plus the installation, the cost is less than equivalent shell and tube.

Cost of compact heat exchangers

Care to be takenFouling:

- Use of non-fouling fluids wherever possible is of course recommended, for example clean air or gases, light carbons and refrigerants.- In open systems, check the possible application of self-cleaning strainers, and the installation of systems to dose with biocides, scale inhibitors, etc., to control fouling.- Use self-cleaning filter if possible- Consider chemical cleaning. If this is undertaken, the system must be designed to allow the introduction and complete removal of cleaning fluids.

Corrosion:In some CHEs, the wall thicknesses are less

than in a shell-and-tube heat exchanger, so corrosion rates and allowances need to be accessed carefully

Although CHEs are often made from more corrosion-resistant materials than the shell-and-tube units, other corrosion mechanisms such as cracking may occur, and the compatibility of the material with the fluids in the CHE should be checked.

Environmental AspectsEnergy conservation and environmental

considerations are the driving forces behind changes aimed at reducing both chemical and thermal waste.

More efficient use of energy and raw materials

Smaller and cheaper plantAbility to handle high-pressure reactions

ApplicationAutomobileMarineAerospace, AircraftCriogenic systemsRefrigeration.

Manufacturers in the MarketAlfa LavalGea EcoflexSondexSwepTranterFunke

ConclusionCompact heat exchangers are available in a

wide variety of configurations to suit most processes heat transfer requirements.

The advantages of CHEs, 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 CHEs.

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

ReferencesADVANCES IN COMPACT HEAT EXCHANGERS.

(n.d.). Retrieved March 5, 2009, from http://www.rtedwards.com/books/164/index.html

 http://

www.chemkb.com/equipments/heat-exchangers/printed-circuit-heat-exchanger-pche

 http://www.alfalaval.com

http://www.wikipedia.com

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