The Experts below are selected from a list of 2406 Experts worldwide ranked by ideXlab platform
Yu F Maydanik - One of the best experts on this subject based on the ideXlab platform.
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analysis of heat exchange in the Compensation Chamber of a loop heat pipe
Energy, 2013Co-Authors: M A Chernysheva, V G Pastukhov, Yu F MaydanikAbstract:Abstract A three-dimensional heat–and–mass transfer model of a flat evaporator of a loop heat pipe has been developed for investigating heat–and–mass in a Compensation Chamber filled with a liquid. Numerical simulation was implemented using EFDLab® software package in order to predict the temperature distribution of the flat evaporator of a copper-water LHP (loop heat pipe) as well as the flow streamline and velocity field in the Compensation Chamber as a function of heat load. A computer simulation makes it possible to evaluate the heat exchange at the inner surface of the Compensation Chamber. Heat exchange data were used as a boundary condition in researching the problem of the drying effect of a wick and a transformation of the evaporating front in the active zone of the flat evaporator.
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simulation of thermal processes in a flat evaporator of a copper water loop heat pipe under uniform and concentrated heating
International Journal of Heat and Mass Transfer, 2012Co-Authors: M A Chernysheva, Yu F MaydanikAbstract:Abstract A 3D model has been developed for investigating heat and mass transfer in a flat evaporator of a copper–water loop heat pipe. It takes into account heat-transfer processes in the active zone, the barrier layer of the wick, the wall and the Compensation Chamber. The problem was solved by the finite difference method with the use of a nonuniform grid adapted to the configuration of the flat evaporator and its geometric peculiarities. Investigations have been carried out for understanding the effect of the heating zone size on heat distribution in the evaporator. The heating area was 9 cm2 with a uniform heat supply and 1 cm2 with a concentrated one. Numerical simulation has been performed for a heat load range from 20 to 1100 W. Data have shown that a decrease in the heating area at a fixed heat load results in both increasing temperature on the evaporator wall under the heater and local wick draining in the active zone. The results of the model have been verified using results of experimental tests.
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3d model for heat and mass transfer simulation in flat evaporator of copper water loop heat pipe
Applied Thermal Engineering, 2012Co-Authors: M A Chernysheva, Yu F MaydanikAbstract:This paper presents a three-dimension mathematical model of a flat evaporator of a loop heat pipe which takes into account the peculiarities of the evaporator configuration and the specific character of a one-side heat load supply. All the main structural elements of the evaporator, such as its body, wick, vapor-removal grooves, barrier layer and Compensation Chamber, are included in the model. The intensity of heat-exchange processes during evaporation in the active zone is determined by local drops between the temperature at the wick surface and the vapor temperature. The effects of drying the wick in the evaporation zone are also taken into account. The problem was solved by a numerical method. The results of calculations are presented for a copper evaporator and water as a working fluid in the heat load range from 20 to 1100 W. A comparative analysis of calculated and experimental data has been made.
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steady state operation of a copper water lhp with a flat oval evaporator
Applied Thermal Engineering, 2011Co-Authors: Susanne Becker, S V Vershinin, Valerie Sartre, Eckart Laurien, Jocelyn Bonjour, Yu F MaydanikAbstract:Abstract In order to dissipate the heat generated by electronic boxes in avionic systems, a copper–water LHP with a flat-oval evaporator was fabricated and tested at steady state. The LHP consists of a flat shaped evaporator, 7 mm thick, including Compensation Chamber with attached heat exchanger. The condenser is cooled by forced convection of liquid. The variable parameters are the heat sink and ambient temperatures (20 and 55 °C), the orientation (−90° to +90° in two perpendicular planes) and the power input (0–100 W). Evaporator wall temperatures are higher when the evaporator is placed above the condenser. For heat sink and ambient temperature of 20 °C the evaporator wall temperature does not vary much with heat load for all measured elevations. But it fluctuates at heat sink and ambient temperature equal to 55 °C when the evaporator is placed below the condenser. The LHP total thermal resistance is governed by the condenser resistance. It decreases with increasing heat load, whatever the operating conditions, because the part of the condenser internal surface area used for condensation increases too. A minimum thermal resistance of 0.2 K/W was obtained. The maximum thermal resistance was 2.7 K/W.
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operating temperature and distribution of a working fluid in lhp
International Journal of Heat and Mass Transfer, 2007Co-Authors: M A Chernysheva, S V Vershinin, Yu F MaydanikAbstract:Abstract One of the main factors that influence the operating temperature of a loop heat pipe (LHP) is the distribution of a working fluid in the device. The paper presents the classification of LHP operating modes on the basis of the criterion of presence or absence of the working-fluid vapor phase in the Compensation Chamber (CC). It gives a description of method of calculating the LHP operating temperature for every operating mode and shows the characteristic features, advantages and disadvantages of every mode.
Hongxing Zhang - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on transient characteristics of a dual Compensation Chamber loop heat pipe subjected to acceleration forces
Applied Thermal Engineering, 2018Co-Authors: Yongqi Xie, Dongsheng Wen, Yang Zhou, George Haritos, Hongxing ZhangAbstract:In this article, an experimental study has been conducted to provide better understanding of the transient characteristics of a dual Compensation Chamber loop heat pipe (DCCLHP) subjected to the acceleration force. A new acceleration test rig was set up to provide the acceleration up to 11 g with three different directions. The heat load on the evaporator ranging from 25 W to 300 W was applied with the acceleration force simultaneously. Experimental results indicated that the DCCLHP could start up at a small heat load of 25 W and the startup behavior was different under acceleration direction conditions because of the vapor-liquid distribution change in the evaporator and Compensation Chambers (CCs). Under the current operating conditions, the effect of acceleration force was significant to the operating performance at small heat loads whereas was weak at large heat loads. Experimental results also clearly showed that both acceleration magnitude and direction can alter the operating mode. What’s more, it was found that temperature oscillation, reverse flow and evaporation in the evaporator core phenomena occurred under acceleration conditions.
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Mathematical modeling of steady-state operation of a loop heat pipe
Applied Thermal Engineering, 2009Co-Authors: Hongxing ZhangAbstract:A steady-state mathematical model of a loop heat pipe is established and compared with experimental results in this work. The modeling of the evaporator wick includes not only the single-layer wick, but also the two-layer compound wick. The annular flow model is adopted in the modeling of the condenser, in which the effect of surface tension of liquid and the interaction between the liquid and vapor phases including both frictional and momentum-transfer shear stresses are considered. The model can predict the decreasing length of the condenser two-phase zone under the constant conductance mode caused by the volume expansion of the liquid in the Compensation Chamber, and is in good agreement with the experimental data. It also shows that the application of the two-layer compound wick can improve the performance of the loop heat pipe operating under the variable conductance mode, due to the reduction of heat leak from the evaporator to the Compensation Chamber. A parametric study of the effect of heat sink temperature, ambient temperature, adverse elevation, and working fluid inventory on the operating temperatures of the loop heat pipe is also conducted, which further contributes to the understanding of the steady-state operating characteristics of loop heat pipes.
Roger R. Riehl - One of the best experts on this subject based on the ideXlab platform.
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mathematical model of a loop heat pipe with cylindrical evaporator and integrated reservoir
Applied Thermal Engineering, 2008Co-Authors: Valeri V Vlassov, Roger R. RiehlAbstract:Abstract This paper presents a mathematical model of a loop heat pipe (LHP), which has been validated with experimental results. The LHP behavior was then predicted as a thermal control component of a satellite under different scenarios of orbital heat fluxes impression on the condenser–radiator. The mathematical model features the monitoring of the vapor–liquid front in the condenser, as well as the rate of flooding in the Compensation Chamber. The features of eventual entering of vapor phase in the liquid line and partial condensing of vapor in the vapor line is also embedded in the model. In the LHP condenser, the condensate film thickness in the tube is determined by the solution of the conjugate equations of energy, momentum and mass balance in the control volume, considering shear stress at the interface. Evaporator and Compensation Chamber are both described by a few transient nodes with generalized thermal and mass links, where the key parameters were adjusted by experimental test results. The evaporator, integrated with Compensation Chamber, consists of cylindrical stainless steel case with inserted an ultra-high molecular weight (UHMW) polyethylene primary wick and the secondary wick is made with stainless steel mesh. The condenser is a coiled tube thermally connected to an aluminum plate, having a radiator function; acetone was used as the working fluid. The tests conditions have been reproduced in the mathematical model and its parameters were adjusted in order to improve the model capacity to represent the real LHP operation.
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mathematical model of a loop heat pipe with cylindrical evaporator and integrated reservoir
Applied Thermal Engineering, 2008Co-Authors: Valeri V Vlassov, Roger R. RiehlAbstract:Abstract This paper presents a mathematical model of a loop heat pipe (LHP), which has been validated with experimental results. The LHP behavior was then predicted as a thermal control component of a satellite under different scenarios of orbital heat fluxes impression on the condenser–radiator. The mathematical model features the monitoring of the vapor–liquid front in the condenser, as well as the rate of flooding in the Compensation Chamber. The features of eventual entering of vapor phase in the liquid line and partial condensing of vapor in the vapor line is also embedded in the model. In the LHP condenser, the condensate film thickness in the tube is determined by the solution of the conjugate equations of energy, momentum and mass balance in the control volume, considering shear stress at the interface. Evaporator and Compensation Chamber are both described by a few transient nodes with generalized thermal and mass links, where the key parameters were adjusted by experimental test results. The evaporator, integrated with Compensation Chamber, consists of cylindrical stainless steel case with inserted an ultra-high molecular weight (UHMW) polyethylene primary wick and the secondary wick is made with stainless steel mesh. The condenser is a coiled tube thermally connected to an aluminum plate, having a radiator function; acetone was used as the working fluid. The tests conditions have been reproduced in the mathematical model and its parameters were adjusted in order to improve the model capacity to represent the real LHP operation.
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Heat transport capability and Compensation Chamber influence in loop heat pipes performance
Applied Thermal Engineering, 2005Co-Authors: Roger R. Riehl, Tulio C. P. A. SiqueiraAbstract:The development of the loop heat pipe technology for application in future space missions requires that certain aspects related to the operation of this device in regard to the heat transport, geometry and selected working fluid must be carefully considered. As efforts have been focused in the construction of loop heat pipes able to manage up to 80 W of applied heat using an alternative working fluid, designing and testing these devices have shown important results. Two loop heat pipes have been built and tested, where they differ from each other on their Compensation Chamber geometry and use high grade acetone as working fluid, in substitution of the so-used ammonia. Life tests have shown reliable operation for both loop heat pipes with successful startups and continuous operation without temperature overshoot or evaporator dryout. The life tests results investigation have generated important data that has been applied on the design and construction of loop heat pipes toward their use in future space applications.
M A Chernysheva - One of the best experts on this subject based on the ideXlab platform.
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analysis of heat exchange in the Compensation Chamber of a loop heat pipe
Energy, 2013Co-Authors: M A Chernysheva, V G Pastukhov, Yu F MaydanikAbstract:Abstract A three-dimensional heat–and–mass transfer model of a flat evaporator of a loop heat pipe has been developed for investigating heat–and–mass in a Compensation Chamber filled with a liquid. Numerical simulation was implemented using EFDLab® software package in order to predict the temperature distribution of the flat evaporator of a copper-water LHP (loop heat pipe) as well as the flow streamline and velocity field in the Compensation Chamber as a function of heat load. A computer simulation makes it possible to evaluate the heat exchange at the inner surface of the Compensation Chamber. Heat exchange data were used as a boundary condition in researching the problem of the drying effect of a wick and a transformation of the evaporating front in the active zone of the flat evaporator.
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simulation of thermal processes in a flat evaporator of a copper water loop heat pipe under uniform and concentrated heating
International Journal of Heat and Mass Transfer, 2012Co-Authors: M A Chernysheva, Yu F MaydanikAbstract:Abstract A 3D model has been developed for investigating heat and mass transfer in a flat evaporator of a copper–water loop heat pipe. It takes into account heat-transfer processes in the active zone, the barrier layer of the wick, the wall and the Compensation Chamber. The problem was solved by the finite difference method with the use of a nonuniform grid adapted to the configuration of the flat evaporator and its geometric peculiarities. Investigations have been carried out for understanding the effect of the heating zone size on heat distribution in the evaporator. The heating area was 9 cm2 with a uniform heat supply and 1 cm2 with a concentrated one. Numerical simulation has been performed for a heat load range from 20 to 1100 W. Data have shown that a decrease in the heating area at a fixed heat load results in both increasing temperature on the evaporator wall under the heater and local wick draining in the active zone. The results of the model have been verified using results of experimental tests.
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3d model for heat and mass transfer simulation in flat evaporator of copper water loop heat pipe
Applied Thermal Engineering, 2012Co-Authors: M A Chernysheva, Yu F MaydanikAbstract:This paper presents a three-dimension mathematical model of a flat evaporator of a loop heat pipe which takes into account the peculiarities of the evaporator configuration and the specific character of a one-side heat load supply. All the main structural elements of the evaporator, such as its body, wick, vapor-removal grooves, barrier layer and Compensation Chamber, are included in the model. The intensity of heat-exchange processes during evaporation in the active zone is determined by local drops between the temperature at the wick surface and the vapor temperature. The effects of drying the wick in the evaporation zone are also taken into account. The problem was solved by a numerical method. The results of calculations are presented for a copper evaporator and water as a working fluid in the heat load range from 20 to 1100 W. A comparative analysis of calculated and experimental data has been made.
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operating temperature and distribution of a working fluid in lhp
International Journal of Heat and Mass Transfer, 2007Co-Authors: M A Chernysheva, S V Vershinin, Yu F MaydanikAbstract:Abstract One of the main factors that influence the operating temperature of a loop heat pipe (LHP) is the distribution of a working fluid in the device. The paper presents the classification of LHP operating modes on the basis of the criterion of presence or absence of the working-fluid vapor phase in the Compensation Chamber (CC). It gives a description of method of calculating the LHP operating temperature for every operating mode and shows the characteristic features, advantages and disadvantages of every mode.
Dongsheng Wen - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on transient characteristics of a dual Compensation Chamber loop heat pipe subjected to acceleration forces
Applied Thermal Engineering, 2018Co-Authors: Yongqi Xie, Dongsheng Wen, Yang Zhou, George Haritos, Hongxing ZhangAbstract:In this article, an experimental study has been conducted to provide better understanding of the transient characteristics of a dual Compensation Chamber loop heat pipe (DCCLHP) subjected to the acceleration force. A new acceleration test rig was set up to provide the acceleration up to 11 g with three different directions. The heat load on the evaporator ranging from 25 W to 300 W was applied with the acceleration force simultaneously. Experimental results indicated that the DCCLHP could start up at a small heat load of 25 W and the startup behavior was different under acceleration direction conditions because of the vapor-liquid distribution change in the evaporator and Compensation Chambers (CCs). Under the current operating conditions, the effect of acceleration force was significant to the operating performance at small heat loads whereas was weak at large heat loads. Experimental results also clearly showed that both acceleration magnitude and direction can alter the operating mode. What’s more, it was found that temperature oscillation, reverse flow and evaporation in the evaporator core phenomena occurred under acceleration conditions.
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experimental investigation of a dual Compensation Chamber loop heat pipe
International Journal of Heat and Mass Transfer, 2010Co-Authors: Guiping Lin, Lizhan Bai, Dongsheng WenAbstract:Abstract This work performs a fundamental study of a Dual Compensation Chamber Loop Heat Pipe (DCCLHP) through partial visualization of the flow phenomenon inside its Compensation Chambers and the condenser. Both startup and steady-state performance of the DCCLHP and the influence of initial vapor–liquid distribution, startup heat load, heat sink temperature and relative orientations on the performance of the DCCLHP are studied. The result shows a typical ‘V’ curve operation temperature at heat loads over 50 W at the steady-state, and reveals some unique phenomena during the startup of the DCCLHP such as bubble generation in the liquid core, reverse flow, fluctuated flow and liquid re-distribution between the Compensation Chambers and the external loop, which are caused mainly by the radial heat leak from the evaporator. Some unstable phenomena during the startup, steady-state operation and unloading period of the DCCLHP are also revealed in this study including temperature fluctuations, temperature hysteresis and transient penetration of vapor.