I-70 Investigation of startup behaviors of a loop-heat pipe / H. X. Zhang, G. P. Lin, T. Ding, Yu. F. Maydanik, R. G. Sudakov // Journal of Termophysics and Heat Transfer. - 2005. - Vol. 19, № 4. - С. 509-518 Рубрики: ФИЗИКА Кл.слова (ненормированные): HEAT PIPES -- VAPOR/LIQUID DISTRIBUTION -- VAPOR GROOVES Аннотация: The results of ground experiments on startup behaviors of a loop heat pipe are presented. One objective is to investigate the effects of working conditions on the startup of loop heat pipes. Startup behaviors as functions of various parameters, including the vapor/liquid distribution-in the evaporator, startup heat load, sink temperature, and adverse elevation are described and explained. The physical process of startup is described, and the explanation that pressure transfer leads to the saturated temperature rise in the compensation chamber during startup is discussed. The other objective is to investigate the effect of startup on the steady-state operation of loop heat pipes. Test results indicate that evaporation inside the wick tends to occur at low startup heat loads when the evaporator, including the vapor grooves and the evaporator core, is flooded with liquid. Some peculiar phenomena, including evaporation inside the wick, temperature oscillation at the condenser inlet, and reverse flow equilibrium, which lead to higher operating temperatures, were observed during startups |
H 65 High heat flux loop heat pipes / M. T. North, D. B. Sarraf, J. H. Rosenfeld, Yu. F. Maydanik, S. V. Vershinin // 6th European Symposium on Space Environmental Control Systems: Noordwijk, Netherlands, 20-22 may 1997 . - 1997. - Vol. 400. - С. 371-376 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPES -- POWER LOADS -- GRAVITATIONAL HEADS Аннотация: Loop Heat Pipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and gravitational heads. While recent transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m(2). This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m(2) This performance exceeded the known state of the art by a factor of more than six for both conventional heat pipes and for loop heat pipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m(2).K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser |
H 65 High heat flux loop heat pipes / M. T. North, D. B. Sarraf, J. H. Rosenfeld, Yu. F. Maydanik, S. V. Vershinin // SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM (STAIF-97), PTS 1-3: 1ST CONFERENCE ON FUTURE SCIENCE & EARTH SCIENCE MISSIONS; 1ST CONFERENCE ON SYNERGISTIC POWER & PROPULSION SYSTEMS TECHNOLOGY; 1ST CONFERENCE ON APPLICATIONS OF THERMOPHYSICS IN MICROGRAVITY; 2ND CONFERENCE ON COMMERCIAL DEVELOPMENT OF SPACE; - 2ND CONFERENCE ON NEXT GENERATION LAUNCH SYSTEMS; 14TH SYMPOSIUM ON SPACE NUCLEAR POWER AND PROPULSION, ALBUQUERQUE, 26-30 JAN, 1997 . - 1997. - Vol.387. - С. 561-566 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPES -- THERMAL POWER LOADS -- VAPOR FLOW LOSSES Аннотация: Loop Heat Pipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and against high gravitational heads. While recent LHPs have transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m(2). This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m(2). This performance exceeded the known state of the art by a factor of more than six for both conventional heat pipes and for loop heat pipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m(2) K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser |
L 88 Loop Heat Pipes for Cooling Systems of Servers / Yu. F. Maydanik, S. V. Vershinin, V. G. Pastukhov, S. Fried // IEEE Transactions on Components and Packaging Technologies. - 2010. - Vol.33, №2. - С. 416-423 Рубрики: ФИЗИКА Кл.слова (ненормированные): HEAT-TRANSFER DEVICE -- LHPs -- OPTERON CPUs Аннотация: Loop heat pipes (LHPs) are exceptionally efficient heat-transfer devices that employ a closed loop evaporation-condensation cycle that can be used to cool densely packed electronic systems that reject large quantities of heat, including computers and their central processing units (CPUs). Tests were carried out on miniature ammonia LHPs with a CPU thermal simulator using different ways of condenser cooling. The possibility of maintaining the cooled object temperatures between 40°C and 70°C with heat load changing from 100 to 320 W was demonstrated. Subsequent tests of these devices in a 1U computer with dual core advanced micro devices Opteron CPUs, dissipating between 95 and 120 W, have confirmed the advantages and heat transfer efficiency of LHP-based cooling systems used to cool CPU in 1U chassis |
S 82 Steady state operation of a copper–water LHP with a flat-oval evaporator / S. Becker, S. V. Vershinin, V. Sartre, E. Laurien, J. Bonjour, Yu. F. Maydanik // Applied Thermal Engineering. - 2011. - Vol.31, №5. - С. 686-695. - Библиогр.: с. 695 (24 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- HEAT TRAHSFER -- EXPERIMENTAL STUDY Аннотация: 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 \\\\expert2\\NBO\\Applied Thermal Engineering\\2011, v. 31, p.686.pdf |
I-70 Investigation of a compact copper–water loop heap pipe with a flat evaporator / Yu. F. Maydanik, S. V. Vershinin, M. Chernysheva, S. Yushakova // Applied Thermal Engineering. - 2011. - Vol.31, №16. - С. 3533-3541. - Библиогр.: с. 3541 (22 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): ELECTRONICS COOLING -- LOOP HEAT PIPE -- FLAT–OVAL EVAPORATOR Аннотация: A compact copper–water loop heat pipe (LHP) with an effective length of 310 mm equipped with a flat–oval evaporator measuring 80 (L) × 42 (W) × 7 (H) has been tested. The vapor line and the condenser had the same internal diameter of 5.4 mm. The internal diameter of the liquid line was 3.4 mm. Tests were conducted with a heat source which had a heating surface of 30 mm × 30 mm. The condenser was cooled by running water with a temperature of 20 °C. In the horizontal position the device has exhibited serviceability in the heat load range from 5 W to 1200 W at vapor temperatures from 26.5 °C to 103.4 °C. The maximum capacity was achieved at a heat source temperature of 143.5 °C, when the LHP thermal resistance was equal to 0.044 °C/W. The corresponding values of thermal resistance for the evaporator and the condenser were at a level of 0.006 °C/W and 0.038 °C/W. A minimum thermal resistance of 0.097 °C/W for the “heat source–LHP–cooling water” system was obtained at a heat load of about 700 W, at which the temperature of the heat source was 87 °C \\\\expert2\\NBO\\Applied Thermal Engineering\\2011, v. 31, p.3533.pdf |
V 50 Vershinin, S. V. Hysteresis phenomena in loop heat pipes / S. V. Vershinin, Yu. F. Maydanik // Applied Thermal Engineering. - 2007. - Vol.27, №5-6. - С. 962-968 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- CAPILLARY METHOD -- EVAPORATION Аннотация: Testing of loop heat pipes (LHPs) has shown that the heat-load dependence of the operating temperature is not always unambiguous. It may have a hysteresis nature. It has been found that temperature hysteresis is connected with changes in the liquid distribution between the compensation chamber (CC) and the condenser. Analysis makes it possible to distinguish three types of temperature hysteresis. In the first case this redistribution is caused by the change in the amount of the parasitic heat flow that penetrates into the CC, which in its turn is a result of heat-transfer hysteresis in the evaporation zone. In the second, temperature hysteresis is connected with the liquid metastable state, which leads to a delay of formation of the vapor phase in the compensation chamber. The reason for hysteresis of the third type is the change of the initial liquid distribution in an LHP during a start-up |
M 43 Maydanik, Yu. F. Development and tests of ammonia Miniature Loop Heat Pipes with cylindrical evaporators / Yu. F. Maydanik, S. V. Vershinin // Applied Thermal Engineering. - 2009. - Vol.29, №11-12. - С. 2297-2301 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- EVAPORATOR -- CONDENSER Аннотация: Miniature Loop Heat Pipes (MLHPs) are an attractive object for development and investigation as quite a promising means for cooling powerful electronics operating in the temperature range from 50 to 100 °C. The paper generalizes and presents the results of development and tests of 15 different variants of ammonia MLHPs with cylindrical evaporators 5 and 6 mm in diameter, which have an active zone length of 20 mm and are equipped with titanium and nickel wicks. As a result of successive efforts aimed at increasing the MLHPs efficiency, it was possible to achieve values of the heat-transfer coefficient close to 162,000 W/m2 °C at a value of the heat flux of about 100 × 104 W/m2. A maximum heat flux value of about 135 × 104 W/m2 was achieved at the heat-transfer coefficient equal approximately to 75,000 W/m2 °C |
C 51 Chernysheva, M. A. Heat transfer during condensation of moving steam in a narrow channel / M. A. Chernysheva, S. V. Vershinin, Yu. F. Maydanik // International Journal of Heat and Mass Transfer. - 2009. - Vol.52, №11-12. - С. 2437-2443 Рубрики: ФИЗИКА Кл.слова (ненормированные): INTUBE CONDENSATION -- TWO-PHASE FLOW -- LOOP HEAT PIPE Аннотация: The paper presents the results of experimental investigation of heat transfer and hydrodynamics during condensation of moving steam in a narrow channel of square cross-section 2 mm × 2 mm. The channel had a serpentine shape, the channel length was 660 mm. An experimental cell simulated conditions of heat transfer in the condenser of loop heat pipes. The steam velocity at the channel inlet ranged from 13 to 52 m/s, the pressure was 1 atm. The temperature of the cooling water varied from 70 to 95 °C. The annular flow pattern was noted in the whole range of the regime parameters. There was a clear boundary between the condensation zone and the zone occupied by the condensed phase downstream. Temperature has measured along the channel, and the heat-transfer coefficients have been determined. The coefficient values varied from 10,000 to 55,000 W/K m2 depending on the steam velocity at the channel inlet and the cooling temperature. The efficiency of the condenser – heat exchanger has been investigated |
B 27 Bartuli, E. Visual and instrumental investigations of a copper-water loop heat pipe [Электронный ресурс] / E. Bartuli, S. V. Vershinin, Yu. F. Maydanik // International Journal of Heat and Mass Transfer. - 2013. - Vol.61, №1. - P35-40 Рубрики: ФИЗИКА Кл.слова (ненормированные): CONDENSATION -- COPPER-WATER LOOP HEAT PIPE -- FLAT GAP CONDENSER Аннотация: Visual and instrumental investigations of the processes of condensation and redistribution of a working fluid in a loop heat pipe have been carried out. This paper presents the results of an experimental investigation of the heat transfer and hydrodynamics during the condensation of water vapor in a flat gap condenser measuring 80 × 40 × 1 mm. Investigations have been conducted at a condenser cooling temperature of 20, 40 and 60 °. During all operating modes a stratified two-phase flow and film condensation have been observed. The temperature field in the condenser has been measured, and the heat-transfer coefficients and the thermal resistances have been determined |
C 51 Chernysheva, M. A. Copper-water loop heat pipes for energy-efficient cooling systems of supercomputers / M. A. Chernysheva, S. Yushakova, Yu. F. Maydanik // Energy . - 2014. - С. 534-542. - Bibliogr. : p. 542 (16 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): COOLING SYSTEM -- OPERATING TEMPERATURE -- LOOP HEAT PIPE Аннотация: An implementation of a cooling system with a loop heat pipe for thermal control of supercomputers is considered. For this purpose two copper-water loop heat pipes (LHPs) with an effective length of 400mm and ID/OD diameters of the vapor lines of 3/4 and 4/5mm correspondingly were designed and tested. The LHPs were equipped with a flat-oval evaporator with one-sided heat supply. The evaporator had a thickness of 7mm, a length (including the compensation chamber) of 80mm and a width of 42mm. The influence of the cooling temperature of the condenser on the LHP operating characteristics was the central issue of this research. Tests were conducted in the range of the cooling temperature from 20 to 80°C. The heat load supplied to the evaporator was varied from 20 to 600W. A mathematical model for prediction of the LHP's operating temperature has been developed. It takes into consideration three operating modes of a loop heat pipe. Modeling results and their analysis are presented \\\\expert2\\nbo\\Energy\\2014, v. 69, p. 534-542.pdf |
C 51 Chernysheva, M. A. Effect of external factors on the operating characteristics of a copper–water loop heat pipe [Electronic resource] / M. A. Chernysheva, S. Yushakova, Yu. F. Maydanik // International Journal of Heat and Mass Transfer. - 2015. - С. 297-304. - Bibliogr. : p. 304 (13 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPES -- OPERATING TEMPERATURE -- COOLING SYSTEM OF COMPUTER SERVERS Аннотация: The paper presents operating characteristics of a copper–water loop heat pipe (LHP) developed for the use in cooling systems of servers for heat transfer from heat-tensioned elements of electronics to peripheral sections or an outer circulation cooling loop beyond the server. The LHP effective length was 400 mm. The device was provided with a flat-oval evaporator. Its thickness, width and length were equal to 7 mm, 42 mm and 80 mm, respectively. The evaporator was equipped with a thermal interface whose heating zone measured 30 mm × 30 mm. The aim of the research work was to determine the effect of external factors such as the device orientation, the condenser cooling temperature and the condition of heat exchange with the surroundings, on the LHP operating performances. The tests were conducted at the unfavorable LHP slopes from 0° to +60° and heat-sink temperatures from 20 °C to 80 °C, and also in different conditions of heat exchange with the outside ambient. The investigation results are presented in the range of heat loads from 20 to 600 W. It has been shown that the slope dependence of the LHP heat-transfer capacity decreases with increasing heat-sink temperature and practically disappears at a value of the latter of 80 °C. In this case the LHP thermal resistance decreases too and reaches a minimum value of 0.02 °C/W in the range of heat loads from 400 to 600 W. \\\\expert2\\nbo\\International Journal of Heat and Mass Transfer\\2015, v. 81, p.297-304.pdf |
I-70 Investigation of startup behaviors of a loop-heat pipe / H. X. Zhang, G. P. Lin, T. Ding, Yu. F. Maydanik, R. G. Sudakov // Journal of Termophysics and Heat Transfer. - 2005. - Vol. 19, № 4. - С. 509-518 Рубрики: ФИЗИКА Кл.слова (ненормированные): HEAT PIPES -- VAPOR/LIQUID DISTRIBUTION -- VAPOR GROOVES Аннотация: The results of ground experiments on startup behaviors of a loop heat pipe are presented. One objective is to investigate the effects of working conditions on the startup of loop heat pipes. Startup behaviors as functions of various parameters, including the vapor/liquid distribution-in the evaporator, startup heat load, sink temperature, and adverse elevation are described and explained. The physical process of startup is described, and the explanation that pressure transfer leads to the saturated temperature rise in the compensation chamber during startup is discussed. The other objective is to investigate the effect of startup on the steady-state operation of loop heat pipes. Test results indicate that evaporation inside the wick tends to occur at low startup heat loads when the evaporator, including the vapor grooves and the evaporator core, is flooded with liquid. Some peculiar phenomena, including evaporation inside the wick, temperature oscillation at the condenser inlet, and reverse flow equilibrium, which lead to higher operating temperatures, were observed during startups |
H 65 High heat flux loop heat pipes / M. T. North, D. B. Sarraf, J. H. Rosenfeld, Yu. F. Maydanik, S. V. Vershinin // 6th European Symposium on Space Environmental Control Systems: Noordwijk, Netherlands, 20-22 may 1997 . - 1997. - Vol. 400. - С. 371-376 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPES -- POWER LOADS -- GRAVITATIONAL HEADS Аннотация: Loop Heat Pipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and gravitational heads. While recent transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m(2). This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m(2) This performance exceeded the known state of the art by a factor of more than six for both conventional heat pipes and for loop heat pipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m(2).K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser |
H 65 High heat flux loop heat pipes / M. T. North, D. B. Sarraf, J. H. Rosenfeld, Yu. F. Maydanik, S. V. Vershinin // SPACE TECHNOLOGY AND APPLICATIONS INTERNATIONAL FORUM (STAIF-97), PTS 1-3: 1ST CONFERENCE ON FUTURE SCIENCE & EARTH SCIENCE MISSIONS; 1ST CONFERENCE ON SYNERGISTIC POWER & PROPULSION SYSTEMS TECHNOLOGY; 1ST CONFERENCE ON APPLICATIONS OF THERMOPHYSICS IN MICROGRAVITY; 2ND CONFERENCE ON COMMERCIAL DEVELOPMENT OF SPACE; - 2ND CONFERENCE ON NEXT GENERATION LAUNCH SYSTEMS; 14TH SYMPOSIUM ON SPACE NUCLEAR POWER AND PROPULSION, ALBUQUERQUE, 26-30 JAN, 1997 . - 1997. - Vol.387. - С. 561-566 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPES -- THERMAL POWER LOADS -- VAPOR FLOW LOSSES Аннотация: Loop Heat Pipes (LHPs) can transport very large thermal power loads, over long distances, through flexible, small diameter tubes and against high gravitational heads. While recent LHPs have transported as much as 1500 W, the peak heat flux through a LHP's evaporator has been limited to about 0.07 MW/m(2). This limitation is due to the arrangement of vapor passages next to the heat load which is one of the conditions necessary to ensure self priming of the device. This paper describes work aimed at raising this limit by threefold to tenfold. Two approaches were pursued. One optimized the vapor passage geometry for the high heat flux conditions. The geometry improved the heat flow into the wick and working fluid. This approach also employed a finer pored wick to support higher vapor flow losses. The second approach used a bidisperse wick material within the circumferential vapor passages. The bidisperse material increased the thermal conductivity and the evaporative surface area in the region of highest heat flux, while providing a flow path for the vapor. Proof-of-concept devices were fabricated and tested for each approach. Both devices operated as designed and both demonstrated operation at a heat flux of 0.70 MW/m(2). This performance exceeded the known state of the art by a factor of more than six for both conventional heat pipes and for loop heat pipes using ammonia. In addition, the bidisperse-wick device demonstrated boiling heat transfer coefficients up to 100,000 W/m(2) K, and the fine pored device demonstrated an orientation independence with its performance essentially unaffected by whether its evaporator was positioned above, below or level with the condenser |
L 88 Loop Heat Pipes for Cooling Systems of Servers / Yu. F. Maydanik, S. V. Vershinin, V. G. Pastukhov, S. Fried // IEEE Transactions on Components and Packaging Technologies. - 2010. - Vol.33, №2. - С. 416-423 Рубрики: ФИЗИКА Кл.слова (ненормированные): HEAT-TRANSFER DEVICE -- LHPs -- OPTERON CPUs Аннотация: Loop heat pipes (LHPs) are exceptionally efficient heat-transfer devices that employ a closed loop evaporation-condensation cycle that can be used to cool densely packed electronic systems that reject large quantities of heat, including computers and their central processing units (CPUs). Tests were carried out on miniature ammonia LHPs with a CPU thermal simulator using different ways of condenser cooling. The possibility of maintaining the cooled object temperatures between 40°C and 70°C with heat load changing from 100 to 320 W was demonstrated. Subsequent tests of these devices in a 1U computer with dual core advanced micro devices Opteron CPUs, dissipating between 95 and 120 W, have confirmed the advantages and heat transfer efficiency of LHP-based cooling systems used to cool CPU in 1U chassis |
S 82 Steady state operation of a copper–water LHP with a flat-oval evaporator / S. Becker, S. V. Vershinin, V. Sartre, E. Laurien, J. Bonjour, Yu. F. Maydanik // Applied Thermal Engineering. - 2011. - Vol.31, №5. - С. 686-695. - Библиогр.: с. 695 (24 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- HEAT TRAHSFER -- EXPERIMENTAL STUDY Аннотация: 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 \\\\expert2\\NBO\\Applied Thermal Engineering\\2011, v. 31, p.686.pdf |
I-70 Investigation of a compact copper–water loop heap pipe with a flat evaporator / Yu. F. Maydanik, S. V. Vershinin, M. Chernysheva, S. Yushakova // Applied Thermal Engineering. - 2011. - Vol.31, №16. - С. 3533-3541. - Библиогр.: с. 3541 (22 ref.) Рубрики: ФИЗИКА Кл.слова (ненормированные): ELECTRONICS COOLING -- LOOP HEAT PIPE -- FLAT–OVAL EVAPORATOR Аннотация: A compact copper–water loop heat pipe (LHP) with an effective length of 310 mm equipped with a flat–oval evaporator measuring 80 (L) × 42 (W) × 7 (H) has been tested. The vapor line and the condenser had the same internal diameter of 5.4 mm. The internal diameter of the liquid line was 3.4 mm. Tests were conducted with a heat source which had a heating surface of 30 mm × 30 mm. The condenser was cooled by running water with a temperature of 20 °C. In the horizontal position the device has exhibited serviceability in the heat load range from 5 W to 1200 W at vapor temperatures from 26.5 °C to 103.4 °C. The maximum capacity was achieved at a heat source temperature of 143.5 °C, when the LHP thermal resistance was equal to 0.044 °C/W. The corresponding values of thermal resistance for the evaporator and the condenser were at a level of 0.006 °C/W and 0.038 °C/W. A minimum thermal resistance of 0.097 °C/W for the “heat source–LHP–cooling water” system was obtained at a heat load of about 700 W, at which the temperature of the heat source was 87 °C \\\\expert2\\NBO\\Applied Thermal Engineering\\2011, v. 31, p.3533.pdf |
V 50 Vershinin, S. V. Hysteresis phenomena in loop heat pipes / S. V. Vershinin, Yu. F. Maydanik // Applied Thermal Engineering. - 2007. - Vol.27, №5-6. - С. 962-968 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- CAPILLARY METHOD -- EVAPORATION Аннотация: Testing of loop heat pipes (LHPs) has shown that the heat-load dependence of the operating temperature is not always unambiguous. It may have a hysteresis nature. It has been found that temperature hysteresis is connected with changes in the liquid distribution between the compensation chamber (CC) and the condenser. Analysis makes it possible to distinguish three types of temperature hysteresis. In the first case this redistribution is caused by the change in the amount of the parasitic heat flow that penetrates into the CC, which in its turn is a result of heat-transfer hysteresis in the evaporation zone. In the second, temperature hysteresis is connected with the liquid metastable state, which leads to a delay of formation of the vapor phase in the compensation chamber. The reason for hysteresis of the third type is the change of the initial liquid distribution in an LHP during a start-up |
M 43 Maydanik, Yu. F. Development and tests of ammonia Miniature Loop Heat Pipes with cylindrical evaporators / Yu. F. Maydanik, S. V. Vershinin // Applied Thermal Engineering. - 2009. - Vol.29, №11-12. - С. 2297-2301 Рубрики: ФИЗИКА Кл.слова (ненормированные): LOOP HEAT PIPE -- EVAPORATOR -- CONDENSER Аннотация: Miniature Loop Heat Pipes (MLHPs) are an attractive object for development and investigation as quite a promising means for cooling powerful electronics operating in the temperature range from 50 to 100 °C. The paper generalizes and presents the results of development and tests of 15 different variants of ammonia MLHPs with cylindrical evaporators 5 and 6 mm in diameter, which have an active zone length of 20 mm and are equipped with titanium and nickel wicks. As a result of successive efforts aimed at increasing the MLHPs efficiency, it was possible to achieve values of the heat-transfer coefficient close to 162,000 W/m2 °C at a value of the heat flux of about 100 × 104 W/m2. A maximum heat flux value of about 135 × 104 W/m2 was achieved at the heat-transfer coefficient equal approximately to 75,000 W/m2 °C |