CHARACTERISTICS OF FLOW-RATE TRANSIENTS IN SLUG FLOW

A study of the effect of flowrate transients within the slug flow regi me was carried out in the WASP Facility at Imperial College. The test section consisted of a 36 m long, nominal 3-inch diameter stainless st eel pipe. Air and water were used as the test fluids and the response to a change for flowrate of either phase was measured using a series o f conductivity probes, pressure transducers and a gamma densitometer. When the gas flowrate was increased, the pressure was found to peak ab ove the new steady state value before recovering. In addition, a tempo rary period of intense slugging was observed, particularly at higher l iquid superficial velocity, as well as a decrease in holdup. When the gas flowrate was decreased, a rarefaction in the inlet pressure was ob served together with a period of stratified flow, even though conditio ns were such as to cause slug flow in both the initial and final stead y states. The period of stratified flow was observed to be longer for lower liquid flowrates. For an increase or a decrease in the gas flowr ate, the amplitude of the pressure peak was observed to increase with the ratio of the higher to the lower gas flowrate. In contrast, change s in liquid flowrate were accommodated by smooth transitions between t he corresponding steady states. (C) 1998 Elsevier Science Ltd. All rig hts reserved.