The Experts below are selected from a list of 174 Experts worldwide ranked by ideXlab platform
F. Farajimoghaddam - One of the best experts on this subject based on the ideXlab platform.
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Effect of working Fluid Inventory and heat input on transient and steady state behavior of a thermosyphon
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: S. M. Sadrameli, D. Forootan, F. FarajimoghaddamAbstract:The effect of working Fluid Inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working Fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working Fluid Inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working Fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different times. The results showed that in startup, in the values of the working Fluid equal to 0.14, 0.18 and 0.24, the evaporator temperature has fluctuated behavior that is indicative of the occurrence of geyser boiling phenomenon. When the volume of the working Fluid was more than 0.24, thermosyphon performance was associated with vibration, indicating a high Fluidity and a lack of proper functioning of the thermosyphon. The amount of optimal working Fluid with respect to the total thermal resistance of thermosyphon is equal to 0.18 that in this case, the efficiency of thermosyphon at different levels of heat input is between 73 and 78%. In addition, in any amount of working Fluid, increase of heat input leads to increment in the evaporator and condenser heat transfer coefficient increases and reduction in the total thermal resistance of thermosyphon.
Frederick R Best - One of the best experts on this subject based on the ideXlab platform.
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acoustic gauge monitoring of Fluid Inventory in a microgravity vortex separator
Measurement Science and Technology, 2006Co-Authors: A Barbu, Michael C Ellis, Cable Kurwitz, Frederick R BestAbstract:The careful monitoring of Fluid Inventory being essential to the successful operation of two-phase vortex separation, the applicability of an ultrasonic acoustic gauge to monitor and maintain this Inventory was demonstrated. Once validated, the hydrodynamic limits for steady vortex operation were determined. Data were collected using NASA's reduced gravity aircraft, the 4'' diameter two-phase vortex separator designed and built by Texas A&M University and an ultrasonic transducer and thickness gauge from Panametrics, Inc. Pearson linear regression was used to determine the correlation of the expected Fluid film thickness with the indicated thickness by the gauge. The feasibility and reliability of the acoustic sensor as an operating volume monitor for the phase separator were affirmed by both the analytical and experimental results, both affirming the accuracy of thickness measurements by the gauge for this application. Operational limits were statistically determined such that the film thickness should be kept between 1.956 cm and an upper limit of 3.175 cm. The applicability of acoustic measurements to monitoring separator Inventory was supported by both analytical modelling and the resulting experiment. An acoustic sensing system in conjunction with control software ensured that the varying liquid volume in the separator remained within determined hydrodynamic limits during operation.
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Development of a Unique, Passive, Microgravity Vortex Separator
Fluids Engineering, 2005Co-Authors: Michael C Ellis, Cable Kurwitz, Frederick R BestAbstract:In the microgravity environment experienced by space vehicles, liquid and gas do not naturally separate as on Earth. This behavior presents a problem for two-phase space systems, such as environment conditioning, waste water processing, and power systems. Furthermore, with recent renewed interest in space nuclear power systems, a microgravity Rankine cycle is attractive for thermal to electric energy conversion and would require a phase separation device. Responding to this need, researchers have conceived various methods of producing phase separation in low gravity environments. These separator types have included wicking, elbow, hydrophobic/hydrophilic, vortex, rotary fan separators, and combinations thereof. Each class of separator achieved acceptable performance for particular applications and most performed in some capacity for the space program. However, increased integration of multiphase systems requires a separator design adaptable to a variety of system operating conditions. To this end, researchers at Texas A&M University (TAMU) have developed a Microgravity Vortex Separator (MVS) capable of handling both a wide range of inlet conditions as well as changes in these conditions with a single, passive design. Currently, rotary separators are recognized as the most versatile microgravity separation technology. However, compared with passive designs, rotary separators suffer from higher power consumption, more complicated mechanical design, and higher maintenance requirements than passive separators. Furthermore, research completed over the past decade has shown the MVS more resistant to inlet flow variations and versatile in application. Most investigations were conducted as part of system integration experiments including, among others, propellant transfer, waste water processing, and fuel cell systems. Testing involved determination of hydrodynamic conditions relating to vortex stability, inlet quality effects, accumulation volume potential, and dynamic volume monitoring. In most cases, a 1.2 liter separator was found to accommodate system flow conditions. This size produced reliable phase separation for liquid flow rates from 1.8 to 9.8 liters per minute, for gas flow rates of 0.5 to 180 standard liters per minute, over the full range of quality, and with Fluid Inventory changes up to 0.35 liters. Moreover, an acoustic sensor, integrated into the wall of the separation chamber, allows liquid film thickness monitoring with an accuracy of 0.1 inches. Currently, application of the MVS is being extended to cabin air dehumidification and a Rankine power cycle system. Both of these projects will allow further development of the TAMU separator.Copyright © 2005 by ASME
Jingtao Liang - One of the best experts on this subject based on the ideXlab platform.
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investigation on optimal working Fluid Inventory of a cryogenic loop heat pipe
International Journal of Heat and Mass Transfer, 2013Co-Authors: Yanan Zhao, Jingtao LiangAbstract:Abstract The optimal working Fluid Inventory of a prototype of a cryogenic loop heat pipe (CLHP) is studied in this paper. The CLHP prototype operates within a temperature range of 77–126 K with nitrogen as the working Fluid. The possible Fluid Inventory range is calculated based on analysis of phase distribution of vapor and liquid within the loop in a normal operation mode. Furthermore, a series of experiments are carried out with various filling pressures of the gaseous nitrogen at room temperature for validation of the Fluid Inventory range and identification of the optimal Fluid Inventory. The experimental results are compared with the calculation results, and the effect of different filling pressure on the performance of the CLHP is analyzed.
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operational performance of a cryogenic loop heat pipe with insufficient working Fluid Inventory
International Journal of Refrigeration-revue Internationale Du Froid, 2006Co-Authors: Qing Mo, Jingtao LiangAbstract:Abstract A cryogenic loop heat pipe (CLHP) has been developed for future aerospace applications at the Technical Institute of Physics and Chemistry (TIPC). It has been demonstrated that this CLHP, when placed horizontally, can operate in liquid-nitrogen temperature range and have a heat transfer capability of up to 12 W with proper working Fluid Inventory. This paper presents some particular characteristics of the CLHP when the compensation chamber is half-filled with liquid-phase working Fluid before startup. The device has been tested at different orientations using nitrogen as the working Fluid in order to compare its thermal behavior, specially related to the heat transfer capability, the operation temperature and the thermal resistance, as well as to investigate its operational characteristics under power level as low as 1 W. Tests were performed for the CLHP at horizontal position and with the liquid line 3.4 and 6.4 cm below the vapor line, respectively. The experimental results show the operationability of the CLHP tested at three orientations and tests with the liquid line 6.4 cm below the vapor line show lower operation temperatures and higher heat transfer capability.
S. M. Sadrameli - One of the best experts on this subject based on the ideXlab platform.
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Effect of working Fluid Inventory and heat input on transient and steady state behavior of a thermosyphon
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: S. M. Sadrameli, D. Forootan, F. FarajimoghaddamAbstract:The effect of working Fluid Inventory and heat input on the performance of thermosyphon is investigated in this paper. First, a thermosyphon with diameter of 16 mm made of steel with toluene as working Fluid and the length of the evaporator, adiabatic and condenser section 10, 23 and 17 cm was considered, respectively. The working Fluid Inventory was considered 0.1, 0.14, 0.18 and 0.24 of total volume of thermosyphon and in each case 54–235 W of heat input applied to the evaporator area also. In order to evaluate the transient behavior of the thermosyphon, in any amount of working Fluid, 28 W of heat input was considered and temperature of the evaporator area were recorded at different times. The results showed that in startup, in the values of the working Fluid equal to 0.14, 0.18 and 0.24, the evaporator temperature has fluctuated behavior that is indicative of the occurrence of geyser boiling phenomenon. When the volume of the working Fluid was more than 0.24, thermosyphon performance was associated with vibration, indicating a high Fluidity and a lack of proper functioning of the thermosyphon. The amount of optimal working Fluid with respect to the total thermal resistance of thermosyphon is equal to 0.18 that in this case, the efficiency of thermosyphon at different levels of heat input is between 73 and 78%. In addition, in any amount of working Fluid, increase of heat input leads to increment in the evaporator and condenser heat transfer coefficient increases and reduction in the total thermal resistance of thermosyphon.
F. S. Gunnerson - One of the best experts on this subject based on the ideXlab platform.
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Heat Transfer Analysis of an Inclined Two-Phase Closed Thermosyphon
Journal of Heat Transfer-transactions of The Asme, 1995Co-Authors: F. S. GunnersonAbstract:This note presents a numerical model of inclined thermosyphon performance. Liquid-vapor interfacial shear stress and effects of working Fluid Inventory at various inclination angles are included within. Two important limiting mechanisms, dry-out and flooding, are related to the behavior of performance parameters
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Numerical modeling of the steady-state two-phase closed thermosyphon
International Journal of Heat and Mass Transfer, 1994Co-Authors: F. S. GunnersonAbstract:Abstract The steady-state performance of the gravity-assisted, two-phase, closed thermosyphon was modeled from first principles. Liquid-film momentum advection and axial normal stress, typically neglected by previous investigators, were included and shown to be important to the thermosyphon performance. The model presented also expanded previous analyses to include both temperature and heat-flux controlled thermosyphons and thermosyphons with mixed or other external boundary conditions. Numerical techniques were incorporated to solve the nonlinear governing equations and respective boundary conditions. A series of thermosyphon experiments were conducted. Predictions from the model agree well with experimental results. The parametric effects of operating temperatures, geometry, working Fluid Inventory and condenser thermal capacity were studied. The model presented could be used for optimization studies and design of thermosyphons.