A Backward Monte Carlo Study of the Multiple Scattering of a Polarized Laser Beam

A backward Monte Carlo estimator is developed to describe the multiple scattering of a polarized, narrow light beam by a plane-parallel medium. The case of a right circularly polarized beam is analyzed in this paper. Results indicate that the diffuse light field is partially polarized even at significant optical radii from the incident light beam. The degree of polarization of the diffuse light field is dependent on the optical thickness of the medium and the size parameter of the scatterers

Optimum Angles for a Polarimeter: Part II

The four sets of two optimum rotation angles for a polarimeter consisting of a quarter-wave plate in conjunction with a linear polarizer, both of which are free to rotate, are determined. These angles are obtained by maximizing the determinant of the system measurement matrix. The determinant for this system is approximately twice the value of the determinant when only the quarter-wave plate is free to rotate. In addition, the condition numbers of the measurement matrix decrease with the additional consideration of a rotatable linear polarizer

Optimum Angles for a Mueller Matrix Polarimeter

The four optimum rotation angles for a Mueller matrix polarimeter consisting of a quarter wave plate in conjunction with a linear polarizer, are found. This is done by using the determinant and condition numbers of the system measurement matrix as objective functions in a minimization procedure. The four angles so found result in the polarimeter\u27s estimate of the incident Stokes vector to have a minimum sensitivity with respect to fluctuations in the detected flux and errors in the angular position of the optical components constituting the polarimeter. Four optimal angles are presented. These four angles also retain a simplicity of form for the measurement matrix

A Backward Monte Carlo Estimator for the Multiple Scattering of a Narrow Light Beam

A backward Monte Carlo estimator is derived for the multiple scattering of a narrow light beam of arbitrary spatial distribution incident on a plane parallel layer. A means of obtaining an error estimate which provides an upper bound on the actual error is suggested. The intuitively clear result that the higher order intensities asymptotically approach each other for all optical radii was observed. It is observed that at reasonably modest optical distances from the beam, consideration of only the first or second orders of scatter in the evaluation of the diffuse light field will lead to erroneous results

Experimental study on evaporation of pentane from a heated capillary slot

An experimental investigation of evaporation of a pentane meniscus from a heated capillary slot is presented. A novel aspect of this study is that both the wicking height and steady state evaporation mass flow rate are measured simultaneously. Based on a macroscopic force balance, the apparent contact angle of the evaporating meniscus is experimentally estimated from the wicking height and mass flow rate. This is compared with the results obtained using evaporating thin-film theory. The experimentally estimated contact angle is slightly larger than that obtained from the thin-film model but both show similar trends. Further, it is found that the reduction in the meniscus height is primarily due to an increase in the apparent contact angle. The liquid and vapor pressure drops in the capillary are insignificant relative to the capillary pressure. (C) 2015 Elsevier Ltd. All rights reserved

Experimental studies on a miniature loop heat pipe with flat evaporator with various working fluids

The goal of this paper is to experimentally study the thermal behavior of a miniature loop heat pipe (LHP) with flat evaporator and correlate the findings with visualization studies of the working fluid within the compensation chamber (CC). A miniature LHP with flat evaporator was fabricated and tested with four working fluids - acetone, methanol, n-pentane and ethanol for various heat inputs till deprime at two different sink temperatures. The CC of the LHP is provided with a glass view port for visualization of the working fluid using a high speed camera. The results show that among the fluids tested, n-pentane has the lowest operating temperature, whereas methanol has the broadest heat load range. Visualization studies with all the four fluids at both sink temperatures reveal that there is no bubble generation in the CC for any heat input level prior to deprime. It was also observed that during deprime, there is explosive nucleation in the CC due to intense heat leak into it, accompanied by a rapid rise in the operating temperature due to cessation of fluid flow in the loop

Effect of Heat Pipe Figure of Merit on an Evaporating Thin Film

The performance of a two-phase heat transport device such as the loop heat pipe is influenced by the evaporative heat transfer coefficient in the evaporator. From previous experiments with loop heat pipes, it has been observed that fluids with a high heat pipe figure of merit have a high heat transfer coefficient. Considering an evaporating extended thin film, this paper theoretically corroborates this experimental observation by deriving a direct link between the evaporative heat flux at the interface and the fluid figures of merit (namely interline heat flow parameter and heat pipe figure of merit) in the thin film. Numerical experiments with different working fluids clearly show that a fluid with high figure of merit also has a high cumulative heat transfer in the microregion encompassing the evaporating thin film. Thus, a loop heat pipe or heat pipe that uses a working fluid with a high interline heat flow parameter and heat pipe figure of merit will lead to a high evaporative heat transfer coefficient