Thermal oscillations downstream of an elbow in stratified pipe flow

The test geometry, test methodology and the scope of the thermal transient induced pipe stratification studies are explained. Fluid temperature data from elbow inlet and exit plane thermocouples indicates the presence of large amplitude thermal fluctuations for conditions in which the horizontal pipe upstream of the elbow developed stratified flow induced by a pipe entrant thermal transient. Under severe transient conditions, thermal oscillations of amplitude of almost 70 percent of the pipe inlet transient temperature change are observed in the bulk flow. Transient conditions data and accompanying flow visualization test results show that the largest near wall thermal oscillations are located within and immediately downstream of the elbow. The thermal oscillations can cause thermal stripping and thermal fatigue stress cracking in the elbow region. A specially instrumented test section is fabricated to study these thermal fluctuations.