Static flow instabilities in plate-fin heat exchangers

Pressure drops in plate-fin heat exchangers with a single phase stream and a boiling stream heated by a single phase stream are investigated. The heat flux of these systems is generally not constant along the heat exchanger. A new methodology named as approximative integral solution is developed to investigate the heat transfer and pressure drop equations of these systems analytically. It is shown that there are instances where the slope of the total pressure drop can be negative, both, for single phase and boiling fluids. Stability criteria are derived by setting the derivatives of the pressure drop equal to zero. All results are compared and verified with results obtained by the commercial heat exchanger software MUSE, which is used worldwide to design and simulate plate-fin heat exchangers.