Showing papers by "D. Yogi Goswami published in 1991"
TL;DR: In this article, a laser-based technique is developed by which it is possible to detect particles as small as 10 angstroms in size using the Rayleigh scattering theory, where particles of size less than one third of the wavelength of the incident radiation will scatter according to this theory, the intensity of the scattered light will be the same in the forward as well as in backward directions.
Abstract: Efficiency of binary power cycles can be improved by expanding the hydrocarbon working fluids through two phase region in a turbine and exiting at saturated or superheated condition. This improvement can be achieved if there is no condensation during the expansion or if there is condensation, the droplet size is extremely small. In order to verify this is a particle sizing technique, for extremely small particles in flow, is needed. In this study, a Laser based technique is developed by which it is possible to detect particles as small as 10 angstroms in size. The basis of the technique is that particles of size less than one third of the wavelength of the incident radiation will scatter according of Rayleigh scattering theory. According to this theory, the intensity of the scattered light will be the same in the forward as well as in the backward directions. Therefore, measurement of the scattered intensity at two or three different angles will confirm the presence of Rayleigh scattering. The size of the particles can, then, be calculated from the measured scattered intensity according to the Rayleigh scattering equation. 13 refs., 14 figs., 3 tabs.
8 citations
TL;DR: In this article, velocity profiles for flow through circular tubes in laminar, turbulent, and transition region flows were analyzed using laser Doppler velocimetry and flow visualization was done using the hydrogen bubble technique.
Abstract: This paper analyzes velocity profiles for flow through circular tubes in laminar, turbulent, and transition region flows and how they affect measurement by flowmeters. Experimental measurements of velocity profiles across the cross-section of straight circular tubes were made using laser Doppler velocimetry. In addition, flow visualization was done using the hydrogen bubble technique. Velocity profiles in the laminar and the turbulent flow are quite predictable which allow the determination of meter factors for accurate flow measurement, However, the profiles can not be predicted at all in the transition region. Therefore, for the accuracy of the flowmeter, it must be ensured that the flow is completely in the laminar regime or completely in the turbulent regime. In the laminar flow a bend, even at a large distance, affects the meter factor. The paper also discusses some strategies to restructure the flow to avoid the transition region.
4 citations