Mist/steam cooling in a heated horizontal tube - Part 1: Experimental system

To improve the airfoil cooling significantly for the future generation of a dvanced turbine systems (ATS), a fundamental experimental program has been developed to study the hear transfer mechanisms of mist/steam cooling under highly superheated wall temperatures. The mist/steam mixture was obtained by blending fine water droplets (3 similar to 15 mum in diameter) with the saturated steam at 1.5 bars. Two mist generation systems were tested by usi ng the pressure atomizer and the steam-assisted pneumatic atomizer, respect ively, The test section, heated directly by a DC power supply, consisted of a thin-walled (similar to0.9 mm), circular stainless steel tube with an ID of 20 mm and a length of 203 mm, Droplet size and distribution rt ere meas ured by a phase Doppler particle analyzer (PDPA) system through view ports grafted at the inlet and the outlet of the test section. Mist transportatio n and droplet dynamics were studied in addition to the hear transfer measur ements. The experiment was conducted with steam Reynolds numbers ranging fr om 10,000 to 35,000, wall superheat up to 300 degreesC, and droplet mass ra tios ranging from 1-6 percent. [S0889-504X(00)02402-8].