FLUIDELASTIC INSTABILITY IN A TUBE ARRAY SUBJECTED TO 2-PHASE R-11 CROSS-FLOW

This paper reports on an experimental investigation of flow-induced vi bration in a parallel triangular tube bundle with a pitch to diameter ratio P/D = 1.44. The cantilevered tube bundle was subjected to cross- flow of both single phase and two-phase refrigerant R-ll and the resul ts obtained were analysed to determine the critical flow velocity for fluidelastic instability as well as to observe the nature of the two-p hase flow. The data of other researchers were compared with the result s of the present study by means of dimensionless similitude parameters . The primary contribution of the study is the comparison of the use o f single component two phase mixtures such as R-ll liquid and vapour w ith two component mixtures such as air-water on the response of dynami cally scaled model tube arrays. Some of the results suggest a lower st ability threshold associated with the R-ll two-phase mixtures than sim ilar experiments conducted with air-water two-phase mixtures. It appea rs that commonly ignored factors such as slip between phases and flow regime may have a significant effect on stability behaviour. (C) 1995 Academic Press Limited