Compact Heat Exchanger

INTRODUCTION

Heat exchanger is a apparatus that has two streams of fluid that exchange temperatures in order to heat or cool the system.

Basically this Blog focuses on what are compact heat exchangers, the various types, costs, advantages and disadvantages and how fouling may affect.

Area density greater than 700 m²/m³ for gas or greater than 300 m²/m³ when operating in liquid or two-phase streams.

TYPES OF CHE’S

Plane and Frame Heat Exchanger :-(PHE)

         

                                      

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 :-(PHE)

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

Welded Plate Heat Exchanger 

Plates welded together to increase pressure and temperature limits

Materials:

Stainless still 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)

Two long strips of plate wrapped to form concentric spirals

Materials: carbon steel, stainless steel and titanium

Operation limits:

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

Pressures up to 25 bar

Plate Fin Heat Exchanger (PFHE)

High area density and handles several streams

Materials: 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)

Flexibility of design and high strength offered by techniques of construction

Materials: Stainless steel 316L, alloys, nickel and titanium.

Operating limits:

temperature ranges from -200°C to 900°C.

pressures up to 400 bar   

DESIGN

Analysis based on E and Ntu method

Convection and friction coefficients have been determined by Kays and London.

Some data of design can be supplied by manufacturers.

Results for heat transfer and friction factors for circular tube- circular fin and for circular tubes continuous fin.

     

Advantages 

Improved energy efficiency

A closer approach temperature allows greater transfer.

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 awareness

Companies remain aware of technology of CHE

Limited choice

Particularly for high-pressure

Conservatism 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.

Cost Of Compact Heat Exchanger

CONCLUSION

Compact 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.