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Heat Exchanger Design
Introduction
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| Heat Exchanger Design |
The purpose of heat exchanger after gasifier is to lower the high temperature of output gas to an acceptable range. The syngas produced is still not cleaned, removal of particulates and undesirable gasses is still to be done. The gas cleaning processes requires temperatures lower the gasifier itself due to which there is a necessity to cool the syngas produced. In the present case a typical Shell and Tube heat exchanger is being used for the cooling service.
According to Process Heat Transfer (Kern) the calculation for the heating or cooling of a gas differs in only minor respects from the calculation for liquid-liquid systems.
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Viscosity:
For gases it ranges from 0.015 centipoise to 0.025
Thermal Conductivities:
About 1/5th of the values obtained for liquids
Specific Heat:
Slightly lower than those of organic liquids
There are numerous design procedures and steps available in different literatures, the subject is nearly a century old. Process Heat Transfer by D.Q Kern is one of the pioneer work done on heat transfer equipment. A quite detailed design theory and procedure are presented by Kern But the problem is that the work done is now decades old and nowadays several new features, simplifications and changes have been adopted. Although the basis of calculations will be from the Kern but the design procedure adopted will be from Coulson Richardson Volume 6.
There are three main types of exchangers available for the required duty:
- Double Pipe Heat Exchanger
- Plate and Frame Heat Exchanger
- Shell and Tube Heat Exchanger
The selection will be done on following basis:
- Heat Transfer area
- Application on the basis of approach temperature
- Cost
- Ease of availability
Heat Exchanger Design
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