The relative contributions of the fundamental mechanisms accounting for the enhanced heat transfer in nucleate boiling are difficult to quantify analytically or experimentally. A comprehensive model was developed that permits some accurate insights into this problem. An essential feature involved the numerical mapping of the complicated geometry to a plane where the bubble and wall boundaries lie along constant coordinate lines. The results show that microlayer evaporation accounts for 87 percent of the enhanced wall heat transfer during saturated boiling of water at 1 atm and 8.5 K wall superheat. In contrast, enhanced convective effects were essentially nonexistent during growth and minimal following departure. The analysis predicts an extremely nonuniform thermal boundary layer around the bubble, and shows that the wall thermal boundary layer regenerates almost immediately following departure.

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Many of the improvements in wind-electric stock water pumping systems are attributable to advanced controller strategies and hardware that maximize performance over a range of wind speeds. The cost of the early and more complex controllers was of the order of one quarter of the whole system. Sophisticated yet inexpensive-programmable micro-controllers are now being introduced that enhance both performance and reliability. This study utilized a micro-programmable logic controller (PLC) to place a variable auxiliary load in the form of a stock water heater in parallel with the pump motor. This improves the system’s economic viability on the Northern High Plains by mitigating stock tank freezing to help extend the grazing season. For the variable auxiliary load, the PLC uses long period pulse width modulation to drive a 3-phase solid-state relay. This continuously variable load strategy was designed to both increase the power factor when the pump is operating, and to extract resistive heating power in wind regimes not suitable for operating the pump. This paper reports on the preliminary but encouraging field studies directed toward optimizing the low wind speed water heating performance of this multi-tasking controller when the pump motor is inoperable.

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A'hnlichhkeitstransformationen benutzt und das sich ergebende System gewohnlicher Differentialgleichungen wird numerisch integriert. Die zweiten und dritten asymptotischen Losungen werden stetig crngepaJt, wobei nur die Anjangsbedingungen der erzwungenen Konuektion systernatisch geandert werden. Numerische Ergebnisse in [I'afelform (fur zwei Crashof-Zahlen und eine P r a n d t l -Z a h l ) werden gegeben fur die Temnperaturverteilung und fiir die Drehstriimung, die nunmehr mit der freien und der erzwungenen Konuektion gekoppelt ist. This paper is the second and concluding part of a n investigation into the heat transfer to rotating laminar flows over fixed ground when the effects due to a combination of forced and free convections are included. The analytical methods that are employed are similarity transformations and subsequent integration of the ordinary differential system by continuously joining second and third order asymptotic approximations with forward numerical integrations that were obtained by perturbing the initial conditions for the solutions for forced convection alone. Numerical results for the thermal distribution and for the hydrodynamics that differ from that the forced convetive case due to coupling are tabulated for two C r a s h o f numbers and a fixed P r a n d t l number.HpennaraeMaR p a 6 o~a conepmm B ce6e B KaYecTBe nToporo II nocJreAHero p a a~e n a rnccnenosaHHe Temo-o~M~I I :~, IIccnegosanue naMmrapHoro BpauaTemHoro TeqeIIun Han T B~~A L I M OmoBameM I? ticcjieRoBaHIie . AeiiCTI3IIll BbIHYHEneHHOk II CB060nHOg KOHBeK~IIII. AJIII PeIIIeHAR CllCTeMLI nH@@epeHUIIaJIb€lLIX YpaBHeHkliI B 'IaCTHbIX rIpOII3BOfiHLIx MCIIOJIb3YIOTCH IlpeO6pa30BaHIIH 11ono6a~ II IIOJIy'IaW4aHWI CIICTeMa 06bIIFIIO-HeIlIIbIX flEI@@epeH~MaJIInHbIX YpaBHeHMa gMCJIeHHO IIHTerpIIpyeTCfI. BTopOe II TpeTLe ~CIIMIITOTIIYeCIiIle ]?elIIeHII51 IIOCTOIIHHO COXpaHRlOTCH IIOAxOAfI4llMII, B TO BJ)eMR, I i a K CHCTeMaTH'IeCKII I?3MeHRIOTCFI TOJILIEO Ila9aJIbHble YCJIOBMR BbIHYmfEAeHHOfi KOHBeK~IIII, YHCneHHbIe pe3yJIbTaTbI IlpHBOHHTCR B BMHe Ta6JlIIUbl HOrO TeYeHIIR, I