Plate and frame heat exchangers are the most economical heat exchangers of all the types available. However, the most economical choice comes with the most restrictions on the fluid to be introduced into the heat exchanger. The entering fluid must be exceptionally clean, operating at low pressure, and the fluid temperature ceiling is limited. Violation of any of the operating parameters can and will cause failures and ruin the heat exchanger. Plus, and of great importance, is the little or no variation in the process flow rate. Plate and frame heat exchangers produce extremely high heat transfer rates, which is the main reason for their being the most economical heat exchanger type.