Heat Exchanger forms an extremely important equipment in chemical, petro-chemical plant and Marine application. The operating cost of a chemical plant depends on the proper selection of the heat transfer equipment. It is desirable to get most optimum design from the professionals in the field. AiIshil, the team of technical experts having extensive experience to their credit, have specialised in Thermal mechanical design process, and fabrication of Heat transfer equipments. The design is optimised to provide most economical and compact equipment for the specific duty, taking fully into consideration the following criteria.
Space limitation
Need for supplementary
equipment and instrumentation
Effects of relaxing limits on pressure drops and fouling factors.
Heat Exchangers
Lube Oil Coolers
Drain Coolers
Oil Heaters
Aishil also offers -- Heat exchangers built and fabricated as per customer's drawings and specifications.
Heat Exchangers
Drain Coolers
Oil Coolers
Oil Heaters
Fresh Water Coolers
Feed Heaters
Economiser Coils
Superheater Elements
Main and Aux. condensers
All products are designed and manufactured as per the requirements confirming to International Standards’ like TEMA, BS 3274 DIN or IS 4503-1967

Heat Exchangers - Type
Advantages Applications  
  • This type has a lower cost per square meter of heat transfer area than floating heat exchanger.
  • It utilizers straight tubes which are easily replaceable and cleaned from inside.
  • As shell is always welded to the tubesheets there is no gasketed or packed joints on the shell side, thus
    leading to fewer leakages points.
  • Any number of tube passes is possible with
    partitions on both the heads.
  • Individual tubes are replaceable without any
  • There is minimum by-passing between tube bundle
    and shell.
Fixed tubsheet models are
universally used except when it is essential to inspect and clean the tube outside. This type of completely closed shell side
circuit is particularly
advantageous for high vacuum operations or when gasket
material is a problem.
Advantages Applications  
  • The tube bundle is easily removable for mechanical cleaning of outside of tubes.
  • It utilise straight tubes which are easily replaceable
  • It is very easy for assembly and inspection.
  • It offers provision for thermal expansion.
  • Any leakage passing through the packing goes through the weep holes to the atmosphere and can be easily detected.
This type of construction is
universally used for cooling of
oils - lube, hydraulic, quench, etc. and generally employed for process heating or cooling where removable bundle is
Advantages Applications  
  • It is recommended for higher temperature and pressures on the shell side with removable tube bundle.
  • Any even number of tube sidepasses are possible.
  • It reduces the clearance between shell and tube bundle cover and thus reduces by-passing.
  • It has all advantages of removable bundle viz.ease of cleaning and inspection, provision for differential
    expansion, replaceable straight tubes, etc.
Its application are fairly
universal and are widely used in petroleum and chemical
Advantages Applications  
  • It is the cheapest heat exchanger construction.
  • There is no internal gasket.
  • The tube bundle can be easily removed. This permits easy acces for cleansing and inspecting of tube from outside.
  • U-bend shape allows each individual tube to expand and contract independently, thus taking care of
    differential expansion.
  • The tube bundle fits very close to the inside of the shell. It minimizers by-passing and utilizes fully the space within the shell.
  • Any practical even number of passes on tube side is possible. Since there is no internal cleaning, a bonnet can be used at the stationery tube end. This offers a saving over more expensive channel with flangers and bolted on cover.
The U - tube exchanger is
particularly recommended for high pressure and temperature
applications. Common uses are for condensing steam inside the tubes or boiling freon or
ammonia The U - tube design is often utilised for integral tower / bottom reboilers (without shells) and for kettle type reboilers. It is widely used in
boilers feed water heater and is frequently employed as a tank suction heater for pre - heating of various products before pumping (shell open at U - bend end).
Advantages Applications  
  • This is a very flexible design as adding a few hair-pins or removing them requires little time.
  • Maintenance time is very much reduced as the hairpin can be dismanted quickly.
  • This model offers true counter flow and hence
    maximum heat transfer efficiency.
  • Both the pipes can be eaisly cleaned.
    Lining is easier.

It is widely used where heat transfer surface required is not large or lining of metals is
required e.g. for dilute sulphuric acid service. It is also used for highly foulinq fluids such as
furnace oils.
Design & Construction Features
Standard Heat Exchangers with Suitable Tubes Dia. upto 25.4 mm and Length upto 500 cm.
Pass Arrangements
Shell - side : 1 or 2: Tube - side : 1, 2, 4 or 8.
Baffles and Baffle Spacing
Type and spacings of baffles are selected to match fluid velocities with pump flow rates. According to pumping rate and the viscosity of the fluid, the type and spacing is so chosen as to give the most efficient heat transfer within the pressure drop limitations. The two important types of baffles used are as shown in the figures.
Tube Layout
Three types of tube layouts, as shown in the figures are commonly used. The final choice would depend upon the pressure drop limitation and fouling characteristics of the fluids.
Heat Exchangers are supplied with fixed tubesheet, packed tube sheet depending upon the terminal temperatures and fouling characteristics of fluids. Tubes are either welded (Fig 1), expanded (Fig. 2), flared
(Fig. 3) or a combination of them or packed with metallic packings tightened with Ferrules (Fig. 4) to form a perfect joint with tubesheet.
Heat Transfer Surface
The range of shell & Tube Exchangers includes as small a unit as having 0.5 sq. meters heat transfer surface and as big a unit as having 200 sq. meters heat transfer surface.
Mechanical Design Features
Packed tubesheet models are available in pressure ratings of 5 Kg/cm²,10 Kg/cm²,20 Kg/cm². Fixed tubsheet and floating tubesheet models are available in the pressure ratings of 5 Kg/cm2,10 Kg/cm2, 20 Kg/cm², 30 Kg/cm², 40 Kg/cm², 50 Kg/cm², and 100 Kg/cm²,
Exchangers are designed and constructed to any of the internationally accepted codes like TEMA, B.S. 3274 DIN or IS 4503 - 1967. Code stampings or Lloyd's certificate are provided if required by the customer.

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