Multiphase Flows in Plate and Shell Heat Exchangers

Abstract

Air–water and air–water–oil flows were analyzed in a complex channel prototype of a plate and shell heat exchanger (PSHE) with the aid of a fast camera. Air–water flows were characterized before the PSHE inlet port by electrical capacitance tomography (ECT). The effects of inlet pipe flow pattern (bubbly, stratified, or slug) and flow direction (upward or downward) on PSHE air–water flows were investigated. The resultant phase distribution within the PSHE channel was determined by imaging analysis. Instantaneous velocity fields projected on the channel frontal plane were obtained with particle image velocimetry (PIV) for the dispersed phase of bubbly flows. Stratified pipe flow pattern results in PSHE channel segregated flow. The thermal analysis of segregated flow patterns occurring in the hot and cold sides of a PSHE reveals that the countercurrent configuration may present worse heat transfer performance than the parallel one. PSHE multiphase flows are characterized by breakup phenomenon: the mixture among phases is intensified even if stratification occurs at the inlet port. Oil–water–air downward flows are characterized by oil–water emulsion at the channel center and by water and air–water streams at the channel external part. Oil–water–air upward flows are characterized by air–water and oil–water emulsions at the channel center and by the water stream at the channel external part.