Heat exchanger designs vary based on throughput, thermal duty, local maintenance requirements, size requirements, heat transfer media, the chemical state of the materials (liquid or gas) and physical properties of the materials (e.g., specific heat, viscosity, specific gravity, fouling factors). Each design incorporates all of these factors. After looking at heat transfer requirements, the designer takes the following into consideration:
- Tube Size – smaller diameter tubes mean more surface area and increased fluid turbulence but also higher pressure drop.
- Tube Count – more tubes mean more surface area but there might not be enough room in the given diameter.
- Tube Length – longer tubes mean more surface area but plant space or pressure drop may limit the final length of a specific design.
- Process Stream Velocity – higher velocity (usually created in a design by increasing the number of passes) increases heat exchange but is limited by materials of construction, viscosity of the process stream and available pressure drop.
- Baffles – increasing the number of baffles increases heat transfer and pressure drop.
- Shell Diameter – increasing diameter allows more tubes but greatly increases the cost.
- Materials of Construction – stainless steel, higher alloy steels, carbon steel affect the performance of the exchanger due to the thermal conductive properties of each material.
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