Review of experimental investigations of liquid-metal heat transfer

Experimental data of various investigators of liquid-metal heat-transfer characteristics were reevaluated using as consistent assumptions and methods as possible and then compared with each other and with theoretical results. The reevaluated data for both local fully developed and average Nusselt numbers in the turbulent flow region were found still to have considerable spread, with the bulk of the data being lower than predicted by existing analysis. An equation based on empirical grounds which represents most of the fully developed heat-transfer data is nu = 0.625 pe(0.4) where nu represents the Nusselt number and pe the Peclet number. The theoretical prediction of the heat transfer in the entrance region was found to give lower values, in most cases, than those found in the experimental work

Altitude Cooling Investigation of the R-2800-21 Engine in the P-47G Airplane. IV - Engine Cooling-Air Pressure Distribution

A study of the data obtained in a flight investigation of an R-2800-21 engine in a P-47G airplane was made to determine the effect of the flight variables on the engine cooling-air pressure distribution. The investigation consisted of level flights at altitudes from 5000 to 35,000 feet for the normal range of engine and airplane operation. The data showed that the average engine front pressures ranged from 0.73 to 0.82 of the impact pressure (velocity head). The average engine rear pressures ranged from 0.50 to 0.55 of the impact pressure for closed cowl flaps and from 0.10 to 0.20 for full-open cowl flaps. In general, the highest front pressures were obtained at the bottom of the engine. The rear pressures for the rear-row cylinders were .lower and the pressure drops correspondingly higher than for the front-row cylinders. The rear-pressure distribution was materially affected by cowl-flap position in that the differences between the rear pressures of the front-row and rear-row cylinders markedly increased as the cowl flaps were opened. For full-open cowl flaps, the pressure drops across the rear-row cylinders were in the order of 0.2 of the impact pressure greater than across the front-row cylinders. Propeller speed and altitude had little effect on the -coolingair pressure distribution, Increase in angle of inclination of the thrust axis decreased the front ?pressures for the cylinders at the top of the engine and increased them for the cylinders at the bottom of the engine. As more auxiliary air was taken from the engine cowling, the front pressures and, to a lesser extent, the rear pressures for the cylinders at the bottom of the engine decreased. No correlation existed between the cooling-air pressure-drop distribution and the cylinder-temperature distribution

Trends in the Treatment of Adults with Ureteropelvic Junction Obstruction

Background and Purpose: Minimally invasive pyeloplasty is an effective treatment for patients with ureteropelvic junction obstruction that offers quicker convalescence than open pyeloplasty. Technical challenges, however, may have limited its dissemination. We examined population trends and determinants of surgical options for ureteropelvic junction obstruction. Patients and Methods: Using the State Inpatient and Ambulatory Surgery Databases for Florida, we identified adults who underwent ureteropelvic junction obstruction repair between 2001 and 2009. After determining the surgical approach (minimally invasive pyeloplasty, open pyeloplasty, or endopyelotomy), we estimated annual utilization rates and the effects of patient, surgeon, and hospital predictors on surgery type, using multilevel multinomial logistic regression. Results: Rates of minimally invasive pyeloplasty increased 360% (P for monotonic trendPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140371/1/end.2012.0017.pd