Liquid resupply effects in macrolayer-controlled nucleate boiling
Previous studies of the high-heat-flux nucleate boiling regime have made widely varying assumptions about the state of the macrolayer at the beginning of the hovering period of the mushroom bubbles overlying the macrolayer. The uncertainty in the initial state of the macrolayer is largely because little is known about the nature of liquid resupply to the near-heater area following the departure of the mushroom bubble. An assessment of the effect of the differences in liquid resupply mechanisms by experimental means is extremely difficult because of the microscopic length and time scales involved. The present study investigates this using numerical means. A transient three-dimensional computer program was developed and used to simulate various possible resupply mechanisms and consequently different possible initial temperature profiles in the macrolayer. The results show that in commonly used heater materials such as copper, the initial temperature profile in the macrolayer has very little effect on the boiling curve (surface- andtime-averaged heat flux and temperature). For higher average surface temperatures observed for low-thermal-conductivity heater materials such as nickel, the boiling curve could shift by a few degrees depending on the initial thermal profile in the macrolayer. Initial thickness of the macrolayer does have an effect on the boiling curve for small values of initial thickness; however, for large initial thicknesses, the effect on the boiling curve is small. It also is shown that changes in the time elapsed between replenishment of the macrolayer (hovering period) do not affect the boiling curve significantly as long as localized dryout of the macrolayer does not occur.
- Research Organization:
- Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 10148854
- Report Number(s):
- LA-UR-93-1056; CONF-931121-3; N-6-93-R113; ON: DE93011273
- Resource Relation:
- Conference: Annual winter meeting of the American Society of Mechanical Engineers, New Orleans, LA (United States), 28 Nov - 3 Dec 1993; Other Information: PBD: [1993]
- Country of Publication:
- United States
- Language:
- English
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