Agenda What is a compact heat exchanger? Types Advantages and limitations Cost of heat exchangers Care to be taken Environmental Aspects Conclusion Reference
Basic Definitions A heat exchanger is a device built for efficient heattransfer from one medium to another, whether themedia are separated by a solid wall so that they nevermix, or the media are in direct contact.
What is a Compact HeatExchanger? HT Area density greater than 700 m2/m3 for gas orgreater than 300 m2/m3 when operating in liquid ortwo-phase streams. Highly efficient Reduce volume, weight and cost
Types of CHEs Plate and frame heat exchangers: (PHE) PHE Countercurrent.mp4
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 m3/h
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 applyingchemicals.
Welded Plate Heat Exchanger Plates welded together to increase pressure andtemperature limits Materials: stainless steal and nickel based alloys. Canbe 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 concentricspirals Materials: carbon steel, stainless steel and titanium Operation limits:- Temperatures up to 400°C (depends on gasketedmaterials)- Pressures up to 25 bar
Plate Fin Heat Exchanger (PFHE) High area density and handles several streams Materials: aluminum, corrosion and heat resistantalloys, 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 forstainless steel
Printed-circuit heat exchangers(PCHE) Flexibility of design and high strength offered bytechniques of construction Materials: Stainless steel 316, alloys, nickel andtitanium. The etched plates are stacked and diffusion bondedtogether to make the core of Hx Operating limits:- temperature ranges from -200°C to 900°C- pressures up to 600 bar
Compact Shell-and-Tube HeatExchangerTo increase surface area, this equipment has a largenumber of small diameter tubes
Advantages Improved energy efficiency- Closer approach temperatures allows greater energytransfer. Smaller volume and weight Higher efficiency Lower cost Multi-stream and multi-pass configurations Tighter temperature control Power savings Improved safety
Limitations Lack of industrial awarenessCompanies remain aware of technology of CHE Limited choiceParticularly for high-pressure Conservatism in the user industriesProcess industries are reluctant to adopt what theymay seen either as new technologies. Susceptibility to foulingPerception 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 especiallywhen their total installed cost is considered. In some cases the materials used to manufacture isexpensive, but when we consider the cost of unit plusthe installation, the cost is less than equivalent shelland tube.
Care to be taken Fouling:- Use of non-fouling fluids wherever possible is ofcourse recommended, for example clean air orgases, light carbons and refrigerants.- In open systems, check the possible application ofself-cleaning strainers, and the installation of systemsto dose with biocides, scale inhibitors, etc., to controlfouling.- Use self-cleaning filter if possible- Consider chemical cleaning. If this is undertaken, thesystem must be designed to allow the introduction andcomplete removal of cleaning fluids.
Corrosion: In some CHEs, the wall thicknesses are less than in ashell-and-tube heat exchanger, so corrosion rates andallowances need to be accessed carefully Although CHEs are often made from more corrosion-resistant materials than the shell-and-tube units, othercorrosion mechanisms such as cracking mayoccur, and the compatibility of the material with thefluids in the CHE should be checked.
Environmental Aspects Energy conservation and environmentalconsiderations are the driving forces behind changesaimed at reducing both chemical and thermal waste. More efficient use of energy and raw materials Smaller and cheaper plant Ability to handle high-pressure reactions
Application Automobile Marine Aerospace, Aircraft Criogenic systems Refrigeration.Manufacturers in the Market Alfa Laval Gea Ecoflex Sondex Swep Tranter Funke
Conclusion Compact heat exchangers are available in a widevariety of configurations to suit most processes heattransfer requirements. The advantages of CHEs, and associated heat transferenhancement techniques, extend far beyond energyefficiency. Lower capital cost, reduced plant size, and increasedsafety are typical of the benefits arising from the use ofCHEs. Compact heat exchangers can replace some normalsize heat exchangers bringing advantages andperformance.
References ADVANCES IN COMPACT HEAT EXCHANGERS.(n.d.). Retrieved March 5, 2009, fromhttp://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