Experimental Investigation of Nucleate Boiling on a Thermal Capacitive Heater Under Variable Gravity Conditions
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In the present work the behavior of single vapor bubbles of FC-72, generated on a thermal capacitive heater element, has been investigated during microgravity. A newly developed heater design allows temperature measurements by highspeed infrared thermography on the backside of the heater surface at a distance of approx. 800 nm from the fluid/heater-interface. The employed heater was manufactured by Physical Vapor Deposition (PVD) of a chromium based layer for better emissivity (Slomski et al., Mater Sci Technol 41:161–165, 2010) and a pure chromium heating layer supplying the energy required for bubble generation and sustainment by electrical heating. The thermal diffusivity of the employed Calcium Flouride (CaF) heater substrate is comparable to the thermal diffusivity of stainless steel, which makes this heater design very close to technical applications. The acquired transient temperature fields of the heater surface allow numerical determination of the local heat flux from the heater surface to the fluid. A local temperature drop and high heat fluxes have been observed in the vicinity of the 3-phase contact line. This effect has already been reported by former publications for thin stainless steel foil heaters (Stephan and Hammer, Int J Heat Mass Transfer 30:119–125, 1994; Wagner et al., Int J Heat Mass Transfer 42:875–883, 2006) and is also confirmed for heaters with significantly higher thermal capacities.
KeywordsNucleate boiling Microgravity 3-phase contact line Microregion Infrared thermography
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- Cole, R., Shulman, H.L.: Bubble departure diameters at subatmospheric pressures. In: Chemical Engineering Progresses Symposium Series 62, pp. 6–16 (1969)Google Scholar
- Cole, R., Rohsenow, W.M.: Correlation of bubble departure diameters for boiling saturated liquids. In: Chemical Engineering Progresses Symposium Series 65, pp. 211–213 (1968)Google Scholar
- Fritz, W.: Berechnung des Maximalvolumens von Dampfblasen. Phys. Z. 36, 379–388 (1935)Google Scholar
- Schweizer, N.: Multi-Scale Investigation of Nucleate Boiling Phenomena in Microgravity, pp. 63–73, 82–87, TU Darmstadt, Darmstadt (2010)Google Scholar
- Slomski, E.M., Scheerer, H., Trossmann, T., Berger, C.: Effect of PVD process parameters on nucleation and structure of CrN layer. Mater. Sci. Technol. 41, 161–165 (2010)Google Scholar
- Stephan, P., Hammer, J.: A new model for nucleate boiling heat transfer. Int. J. Heat Mass Transfer 30, 119–125 (1994)Google Scholar
- Straub, J., Zell, M., Vogel, B.: Boiling under microgravity conditions. In: First European Symposium “Fluids in Space”, Ajaccio, France (1991)Google Scholar