B. H. Sage

Thermal and material transfer from spheres: Prediction of local transport

Abstract From a review of the available experimental data upon local thermal and material transport from spheres, expressions were developed to permit the prediction of such transport as a function of Reynolds number, intensity of turbulence, and polar angle. It was found that the effect of Reynolds number was more pronounced in the separated flow found in the aft hemisphere than in the boundary flows of the forward hemisphere. On the other hand, the intensity of turbulence exerted a much more profound effect on the local transport in the forward hemisphere than in the aft hemisphere. The results are presented in terms of the Frossling number.

Thermal and material transport from spheres: Prediction of macroscopic thermal and material transport

Abstract From a review of the available information concerning the effect of the molecular properties of the fluid, conditions of flow, and level of turbulence, a correlation of the Frossling number for the macroscopic or space average transport from spheres has been prepared. The effect of level of turbulence is most marked at a Reynolds number of 40000, and becomes relatively unimportant at Reynolds numbers above 250000. Analytical expressions, empirical in nature, were developed to describe the influence in Reynolds number, levels of turbulence, and the molecular properties of the fluid upon the Frossling number. The accuracy of prediction of the Frossling number is probably comparable to the accuracy of the experimental data. The ratio of the kinematic viscosity of the free stream to that at the interface raised to a power has been found a useful, although empirical, method of correcting for the changes in the molecular properties throughout the boundary flows. The results are presented in graphical and tabular form.

Thermal and material transfer in turbulent gas streams—A method of prediction for spheres

The thermal and material transport from spheres in turbulent air streams have been reduced to analytical expressions taking into account the Reynolds number of the flow, the level of turbulence of the air stream, and the diameter of the sphere. The coefficients for these expressions are based upon experimental work ranging from drops to spheres of about 1 ft in diameter. The range of Reynolds numbers involved extends from 2 to 1.33 × 106. The standard error of estimate for all the experimental measurements was about 15 per cent, while the standard error of estimate for measurements for a much smaller range of sphere diameters was approximately 4 per cent.

A Method of Control of a Predetermined Flow Rate

The accurate control and determination of small rates of displacement of fluids are of interest in many experiments. Such problems are of particular importance in nonequilibrium investigations involving diffusion, flow of fluids, and other studies in which time is a primary variable. A relatively simple device for the predetermination and control of the rate of displacement of fluids at atmospheric and elevated pressures is described. It is believed that the rate of displacement may be maintained at a prescribed value with an uncertainty of not more than 0.05 percent and the error in the actual value of the rate is not more than twice as great.

Micromanometer of High Sensitivity

A sensitive micromanometer based on the observation of the movement of a bubble of air in a precisionbore, horizontal capillary tube was constructed. The sensitivity was varied by connecting different‐sized chambers which had nominal diameters of 1, 2, and 3 in. The sensitivity could be varied between 2×10−5 in. and 2×10−6 in. of manometer fluid.

Experience with Piston‐Cylinder Balance for Pressure Measurements

A piston‐cylinder balance has been found to be a satisfactory means of measuring pressures. Laboratory experience over a fourteen‐year period in the use of such an instrument suitable for measurements up to 10 000 pounds per square inch, is presented. It was found that over a period of ten years the calibration changed by less than four parts in 10 000. This small change in calibration during nearly continuous service of the apparatus is an indication of the suitability of piston‐cylinder balances for routine measurements.

High Pressure Manometer

A manometer which measures differential pressures involving a total head of as much as 1 atm with a precision of 0.002 in. Hg is described. The calibration of the manometer is relatively insensitive to pressure and does not involve any direct or indirect means of visual observation of the mercury‐fluid interface. Application of the instrument is limited to fluids which do not react with mercury.

Manostat for High-Pressure Operations

The maintenance of isobaric conditions at pressures of the order of 10 000 lb/in.2 is sometimes a difficult operation in transport studies. A manostat has been devised which will maintain isobaric conditions with a precision of about 1 part in 100 000 at pressures from 500 to 10 000 lb/in.2. The equipment functions satisfactorily as a pressure transducer for control purposes.

A Laboratory Compressor for Higher Pressures

A compressor suitable for the delivery of air at pressures up to 12,000 p.s.i. is described. This unit employs a piston‐cylinder combination sealed by oil rather than a packed piston rod. This type of construction has been found to operate satisfactorily over a period of years and furnishes a supply of air at elevated pressures for the operation of equipment used in the investigation of the thermodynamic properties of fluids.