Pool boiling experiments using R-113 were conducted in the microgravity of space on a flat heater consisting of a semitransparent gold film sputtered on quartz substrate. Transient measurements of both the mean heater surface temperature and input heat flux are used to compute the mean heat transfer coefficient at the heater wall. Steady state pool boiling is achieved in microgravity under conditions in which a large vapor bubble somewhat removed from the heater surface is formed, which acts as a reservoir for the nucleating bubbles. The steady nucleate boiling heat transfer is enhanced materially in microgravity relative to that in Earth gravity, while the heat flux at which dryout occurs is considerably less. Using quasi-steady data obtained during periods in which some significant portions of the heater surface were dried out, it was possible to construct two distinct composite approximate microgravity pool boiling curves for R-113, one for the higher level of subcooling and one for the lower level of subcooling.
Pool boiling experiments using R-113 were conducted in the microgravity of space on a flat heater consisting of a semitransparent gold film sputtered on quartz substrate. Transient measurements of both the mean heater surface temperature and input heat flux are used to compute the mean heat transfer coefficient at the heater wall. Steady state pool boiling is achieved in microgravity under conditions in which a large vapor bubble somewhat removed from the heater surface is formed, which acts as a reservoir for the nucleating bubbles. The steady nucleate boiling heat transfer is enhanced materially in microgravity relative to that in Earth gravity, while the heat flux at which dryout occurs is considerably less. Using quasi-steady data obtained during periods in which some significant portions of the heater surface were dried out, it was possible to construct two distinct composite approximate microgravity pool boiling curves for R-113, one for the higher level of subcooling and one for the lower level of subcooling.
Pool boiling experiments using R-113 were conducted in the microgravity of space on a flat heater consisting of a semitransparent gold film sputtered on quartz substrate. Transient measurements of both the mean heater surface temperature and input heat flux are used to compute the mean heat transfer coefficient at the heater wall. Steady state pool boiling is achieved in microgravity under conditions in which a large vapor bubble somewhat removed from the heater surface is formed, which acts as a reservoir for the nucleating bubbles. The steady nucleate boiling heat transfer is enhanced materially in microgravity relative to that in Earth gravity, while the heat flux at which dryout occurs is considerably less. Using quasi-steady data obtained during periods in which some significant portions of the heater surface were dried out, it was possible to construct two distinct composite approximate microgravity pool boiling curves for R-113, one for the higher level of subcooling and one for the lower level of subcooling.
The wetting of pyrolytic boron nitride by molten 99.9999% pure aluminum was investigated by using the sessile drop method in a vacuum operating at approximately 660 pPa at temperatures ranging from 700" to 1000°C. The equilibrium contact angle decreased with an increase in temperature. For temperatures at 900°C or less the equilibrium contact angle was greater than 90". At 1000°C a nonwetting-towetting transition occurred and the contact angle stabilized at 49". [
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