HEAT EXCHANGER IN PROCESS INDUSTRY

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Heat transfer is perhaps the most important as well as the most applied process in chemical and petrochemical plants. The economics of plant operation often are controlled by the effectiveness of the utilization and recovery of heat. Heat Transfer is a process by which energy in the form of heat is exchanged between bodies or parts of the same body at different temperatures. Heat exchanger is a device, which transfers heat from one medium to another, usually by conduction through a solid barrier.

Types of Heat Exchangers:
          There are two main types of heat exchangers.

Ø  Direct heat exchanger, where both media between which heat is              exchanged are in direct contact with each other. It is taken for granted that the media are not mixed together. An example of this type of heat exchanger is a cooling tower, where water is cooled through direct contact with air.
Ø  Indirect heat exchanger, where both media are separated by a wall through which heat is transferred. Indirect heat exchangers are available in several types.

 Classification Based on the Fluid Paths:       
                   Heat exchangers can be classified depending upon the basis of the fluid paths through the heat exchanger. Difference is made between

Ø Parallel flow: Parallel flows are those devices in which the warmed and cooled fluids flow past each other in the same direction.
Ø Counter flow: With the counter flow where these two flow in the opposite direction.
Ø  Cross flow: In case of a cross flow, fluids flows pass at right angles to each other.

Classification Based on the State of Media:
Ø Liquid-to-liquid exchangers are those in which two liquids interact.
Ø  Gas-to-gas heat exchangers like air pre heaters in steam plants and helium-cooled reactor gas turbine plants.

               

  

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