Victor W. Goldschmidt

Flapping of a plane jet

Correlations of the instantaneous velocity fluctuations on opposite sides of a subsonic plane jet have been measured. These indicate that there is a measurable flapping of the jet. The frequency of the flapping is estimated by taking the correlation with one signal delayed in time.

Low Reynolds number heat and mass transfer measurements of an overall counterflow, baffled, finned-tube, condensing heat exchanger

Abstract The heat and mass transfer performance of a condensing heat exchanger is characterized. The study is conducted on an indirect contact, direct transfer, overall counterflow, baffled, copper, finned-tube heat exchanger. Heat and mass transfer data are correlated, and a comparison is made to other studies. Interesting behavior and contrasts of the low Reynolds sensible heat transfer in the condensing and non-condensing cases is observed, and a mechanism explaining the physics of these observations is hypothesized.

Structures and flow reversal in turbulent plane jets

The classical description of the longitudinal velocity distribution of fully developed turbulent jets does not conceive of the possible existence of negative velocities. Recent photographs, measurements, and analysis suggest that as far as 60 nozzle widths downstream, there may persist regions of flow reversal which are related to a coherent underlying vortical structure.

Vacuum assisted drying of hydrophilic plates: static drying experiments

Abstract This investigation seeks to identify the effects of partial vacuums on the steady-state drying rate of cotton plates. Five pressure levels between atmospheric pressure and 33.6 kPa (20″ Hg vacuum) were tested in an aluminum vacuum chamber. Improvements in steady state drying rates on the order of 62% were observed at the lowest pressure level. The hoped-for design points were not discovered. Both theoretical and experimental values of the mass transfer rate are developed.

Measurement of aerosol concentrations with a hot wire anemometer

Abstract The use of a hot wire anemometer to measure local mean aerosol concentrations in turbulent flows is discussed. The instrument allows measurement of point particle concentration flux in turbulent shear flows. The extension of the instrument as a size distribution sampler and as a device to determine the kinematics of suspensions is suggested. Experimental calibration results are presented.

Oil concentration in liquid refrigerants: in situ measurement

Abstract The concentration of oil in refrigerants (while in liquid state) can be measured with an acoustic velocity sensor. The transit time for an acoustic signal can be related to the oil concentration and temperature of the liquid mixture. The performance of the sensor is dependent on the properties of the oil and refrigerant, and their miscibility. In general, a thorough calibration becomes necessary. It is shown in this paper that for concentrations less than 10%, an approximation can be made for the estimate of concentration hence eliminating the need for an elaborate calibration procedure.

Conditional (point averaged) temperature and velocities in a heated turbulent plane jet

The conditional (point‐averaged) velocity and temperature profiles in a plane jet of air were measured. The conditional point averages of the mean temperature and velocity were found with respect to the moving interface for five intermittences: γ=0.1, 0.2, 0.3, 0.4, and 0.5, at axial stations of x/D=35, 45, and 50. The results suggest coincidence of the interfaces and a flatter temperature profile within the fully turbulent flow.

The hot wire anemometer as an aerosol droplet size sampler

Abstract The hot wire anemometer is used as a sampler of small liquid droplets. The device is calibrated for droplets of dibutyl phthalate, Sinco prime 70 and safflower, and shown to give a voltage output proportional to the droplet diameter for drops under 200 μm. This is in agreement with analysis presented. An estimate of largest size droplets to hit the wire without shattering and to remain attached without being blown off by the stream is given.

Sensible and Latent Heat Transfer to a Baffled Finned-Tube Heat Exchanger

A straightforward heat exchanger thermal model is presented and verified experimentally. It may be used to predict the performance of a coil that has condensation occurring on the gas side. Experimentally determined heat and mass transfer coefficients are employed in the model Sample data are presented for a wide range of surface wetting conditions. Partially wet heat exchangers are analyzed by employing an area weighting scheme to the dry and wet portions of the coil with moderate success. It is shown that employing a heat / mass transfer analogy in predicting the performance of a condensing heal exchanger may lead to a considerably undersized coil design.

Measurements of the overall heat transfer from combustion gases confined within elliptical tube heat exchangers

Measurements of the overall heat transfer for elliptical cylinders in cross-flow are presented for various flatness ratios and incidence angles. The measurements included the internal convective transfer of confined flowing (hot) gases combined with the external convective transfer. The internal hot gases were created using natural gas flames whereby combustion was completed prior to entering the elliptical test section. Results are reported for three flatness ratios, 0.20, 0.31, and 0.52, in addition to three incidence angles, 0, 45, and 90 degrees. The measurements are compared to round tube measurements and previous studies on elliptical cylinders in cross-flow. Results indicate that a significant flatness (0.30 or less) must be achieved to realize any appreciable (greater than 10 percent) change in the overall heat transfer coefficient. The effect of flattening heat exchanger tubes is presented in terms of the heat transfer enhancement gained without any consideration of the increase in the internal pressure losses.