CRITICAL HEAT-FLUX MEASUREMENTS IN A ROUND TUBE FOR CFCS AND CFC ALTERNATIVES

Critical heat flux (CHF) measurements have been conducted for HFC-134a , HCFC-123, HCFC-22, CFC-12 and CFC-11 in a multi-fluid loop. The test pressures are up to 2 MPa (corresponding to water equivalent pressure of 7-10 MPa) and mass fluxes from 1000 to 4000 kg m-2 s-1. The heated length is adjustable from 0.5 to 1 m, the I.D. of the tubular test se ction is 4.2 mm, and the critical quality varies from 0.07 to 0.6. The parametric trends of test results are examined and the test results s how good agreement with existing CHF prediction methods. It also provi des confirmation that CFC alternatives such as HFC-134a, HCFC-123 and HCFC-22 can be used with confidence as reliable CHF modelling fluids.