Thermocapillary effects on low-g Pool Boiling from microheater arrays of various aspect ratio
Tóm tắt
Pool boiling heat transfer measurements from heaters of varying aspect ratio were obtained in low-g (0.01 g ± 0.025 g) and high-g (1.7 g ± 0.5 g) using the KC-135 aircraft. The heater aspect ratio was varied by selectively powering 2×2, 2×4, 2×6, 2×8, and 2×10 arrays of heaters in a 10×10 heater array containing individual heaters 700×700 μm2 in size. Control circuitry was used to maintain a nominally isothermal boundary condition on the heater surface while the power dissipated by the heater was measured. Steady-state boiling data in low-g and high-g were obtained using FC-72 as the working fluid at two bulk fluid temperatures. At high wall superheats, boiling performance appears to decrease with an increase in aspect ratio. Strong thermocapillary convection was observed for a negligible gas concentration in the liquid. CHF was not observed for the heater used in this study indicating that CHF in low-g may be highly dependent on the surface characteristics of the heater in addition to the heater size.
Tài liệu tham khảo
Viskanta, R. et al: Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies. Topical Report of the National Research Council-Space Studies Board (2000).
DiMarco, P.: Review of Reduced Gravity Boiling Heat Transfer: European Research. Japan Society of Microgravity Application Journal, vol. 20, no. 4, p. 252–263 (2003).
Kim, J.: Review of Reduced Gravity Boiling Heat Transfer: US Research. Japan Society of Microgravity Application Journal, vol. 20, no. 4, p. 264–271 (2003).
Ohta, H.: Review of Reduced Gravity Boiling Heat Transfer: Japanese Research. Japan Society of Microgravity Application Journal, vol. 20, no. 4, p. 272–285 (2003).
H. Merte, H. S. Lee and R. B. Keller: Dryout and Rewetting in the Pool Boiling Experiment Flown on STS-72 (PBE-IIB) and STS-77 (PBE-IIA). NASA/CR-1998-207410 (1998).
Kim, J., Benton, J.F., andWisniewski, D.: Pool Boiling Heat Transfer on Small Heaters: Effect of Gravity and Subcooling. International Journal of Heat and Mass Transfer, vol. 45, p. 3919–3932 (2002).
Straub, J.: Origin and Effect of Thermocapillary Convection in Subcooled Boiling: Observations and Conclusions from Experiments Performed at Microgravity. Ann. New York Acad. Sci. 974, p. 348–363 (2002).
Henry, C.D. andKim, J.: Heater Size, Subcooling, and Gravity Effects on Pool Boiling Heat Transfer. International Journal of Heat and Fluid Flow, vol. 25, no. 2, p. 262–273 (2004).
Rule, T.D. andKim, J.: Heat Transfer Behavior on Small Horizontal Heaters During Pool Boiling of FC-72. Journal of Heat Transfer, vol. 121, no. 2, p. 386–393 (1999).
Bae, S., Kim, M., Kim, J.: Improved Technique To Measure Time-And Space-Resolved Heat Transfer Under Single Bubbles During Saturated Pool Boiling Of FC-72. Experimental Heat Transfer, vol. 12, no. 3, p. 265–278 (1999).