Journal articles: 'Thermosyphon mode'

1

Balunov, Boris, and Mikle Egorov. "High-temperature service life tests of full-size thermosyphons." E3S Web of Conferences 140 (2019): 05009. http://dx.doi.org/10.1051/e3sconf/201914005009.

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During past two decades, at temperature 240-265°C, resource tests were carried out on 19 thermosyphons of full-scale sizes: 45х4 mm in diameter, 4.92 m in length. The thermosyphons were prepared with varying preliminary surface treatment methods, composition of the aqueous solution to be poured into the thermosyphons, location of titanium chips in the perforated capsules under the lid of the thermosyphons. With a period of 1 to 3 years, thermosyphons were removed from testing system for 30 hours to control the vacuum by thermal method that does not require depressurization. At the last control experiment, four thermosyphons are depressurized for the following purposes: to check the condition of their internal surface in different zones along the length; for the chemical analysis of the aqueous solution poured from them; to determine the structure and characteristics of the mechanical properties of the thermosyphon metal. The main aim of the tests is to justify maintaining the structure and mechanical properties of the metal for a long time, keeping a vacuum of 90-95% inside the thermosyphon, ensuring high heat transfer characteristics of the boiling operating mode of thermosyphons.

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Shishido, Ikuro, Yukio Suzuki, Kazufumi Watanabe, and Mutsumi Suzuki. "Development of dual-mode cascaded thermosyphon." KAGAKU KOGAKU RONBUNSHU 15, no. 4 (1989): 868–71. http://dx.doi.org/10.1252/kakoronbunshu.15.868.

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Rodríguez-Bernal, Aníbal, and Erik S. Van Vleck. "Complex Oscillations in a Closed Thermosyphon." International Journal of Bifurcation and Chaos 08, no. 01 (January 1998): 41–56. http://dx.doi.org/10.1142/s0218127498000048.

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The dynamics of a closed thermosyphon are considered. Using an explicit construction, obtained through an inertial manifold, exact low-dimensional models are derived. The behavior of solutions is analyzed for different ranges of the relevant parameters, and the Lorenz model is obtained for a range of parameter values. Numerical experiments are performed for three- and five-mode models.

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Tiwari, G. N., S. N. Shukla, and M. S. Sodha. "Performance of large solar water heating system: Thermosyphon mode." Energy Conversion and Management 25, no. 1 (January 1985): 29–38. http://dx.doi.org/10.1016/0196-8904(85)90066-4.

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Singh, A. K., and G. N. Tiwari. "Thermal evaluation of regenerative active solar distillation under thermosyphon mode." Energy Conversion and Management 34, no. 8 (August 1993): 697–706. http://dx.doi.org/10.1016/0196-8904(93)90105-j.

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Zhang, Hainan, Shuangquan Shao, and Changqing Tian. "Simulation of the Thermosyphon Free Cooling Mode in an Integrated System of Mechanical Refrigeration and Thermosyphon for Data Centers." Energy Procedia 75 (August 2015): 1458–63. http://dx.doi.org/10.1016/j.egypro.2015.07.260.

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Zhang, Hainan, Shuangquan Shao, Hongbo Xu, Huiming Zou, Mingsheng Tang, and Changqing Tian. "Simulation on the performance and free cooling potential of the thermosyphon mode in an integrated system of mechanical refrigeration and thermosyphon." Applied Energy 185 (January 2017): 1604–12. http://dx.doi.org/10.1016/j.apenergy.2016.01.053.

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Kamburova, Veselka, Ahmed Ahmedov, Iliya Iliev, Ivan Beloev, and Ivan Pavlovic. "Numerical modelling of the operation of a two-phase thermosyphon." Thermal Science 22, Suppl. 5 (2018): 1311–21. http://dx.doi.org/10.2298/tsci18s5311k.

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In the recent years, the interest towards the application of two-phase thermosyphons as an element of heat recovery systems has significantly increased. The application of thermosyphons is steadily gaining popularity in a wide range of industries and energy solutions. In the present study, a 2-D numerical modelling of a two-phase gas/liquid flow and the simultaneously ongoing processes of evaporation and condensation in a thermosyphon is presented. The technique volume of fluid was used for the modelling of the interaction between the liquid and gas phases. The operation of a finned tubes thermosyphon was studied at several typical operating modes. A parametric study over a non-ribbed and finned tubes thermosyphon was carried out. The commercial software ANSYS FLUENT 14.0 was used for the numerical analysis. It was proven that the numerical modelling procedure adequately recreates the ongoing flow, heat and mass transfer processes in the thermosyphon. The numerical result from the phase interaction in the thermosyphon was visualized. Otherwise, such visualization is difficult to achieve when only using empirical models or laboratory experiments. In conclusion, it is shown that numerical modelling is a useful tool for studying and better understanding of the phase changes and heat and mass transfer in a thermosyphon operation.

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IPPOHSHI, Shigetoshi, Hideaki IMURA, Akio MUTOH, and Kazuki MOTOMATSU. "K-1613 Study on Heat Transport of a Top-heat-mode Loop Thermosyphon." Proceedings of the JSME annual meeting V.01.1 (2001): 217–18. http://dx.doi.org/10.1299/jsmemecjo.v.01.1.0_217.

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Zhao, Shu Lei, Xiao Tian Ding, Zheng Yuan Wei, and Gui Fang Liu. "Performance Test and Flow Pattern Simulation of Small Diameter Thermosyphons." Advanced Materials Research 634-638 (January 2013): 3782–87. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.3782.

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Thermal transfer behavior of small diameter thermosyphons with different fill ratio, the inner and outer temperature response at start-up, and the calculated vapor-liquid two-phase vertical flow regimes were studied. The thermosyphons were fabricated by different diameter glass tubes. The present study suggests that the best thermal conductive performance is obtained with 26% fill ratio. Inner and outer thermal behaviors were experimentally studied with innovative methods of attaching thermocouples on thermosyphon walls from both inside and outside. Experimental results indicated a very good temperature uniformity of thermosyphons. Furthermore, a 2D, planar CFD modeling using explicit Multi-Fluid VOF model in the Eulerian multiphase model was carried out to model the interaction/interface between gas and liquid as well as fluid flow movement inside the tube. Real-time vapor bubble generation, combination and vapor slug maps were derived from the simulation. A good agreement was observed between CFD acquired data and experimental observations. It is evidenced that CFD is a powerful tool to model and examine the complex flow and heat transfer in a thermosyphon.

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Wu, Zhang, Li, and Xu. "Effect of the Inclination Angle on the Steady-State Heat Transfer Performance of a Thermosyphon." Applied Sciences 9, no. 16 (August 13, 2019): 3324. http://dx.doi.org/10.3390/app9163324.

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A two-phase closed thermosyphon is an efficient heat transfer element. The heat transfer process of this type of thermosyphon includes conduction and convective heat transfer accompanied by phase changes. Variations in the inclination angle of a thermosyphon affect the steady-state heat transfer performance of the device. Therefore, the inclination angle is an important factor affecting the performance of a thermosyphon. In this paper, an equation for the actual heating area variations with respect to the inclination angle is deduced, and a model for the areal thermal resistance of a thermosyphon is proposed by analyzing the main influence mechanisms of the inclination angle on the heat transfer process. The experimental results show that the areal thermal resistance, which accounts for the effect of the actual heating area, does not change with respect to the inclination angle and exhibits a linear relationship with the heat transfer rate. The thermal resistance equation is fit according to the experimental data when the inclination angle of the thermosyphon is vertically oriented (90°), and the predicted values of the thermosyphon’s thermal resistance are obtained when the thermosyphon is inclined. The deviations between the experimental data and predicted values are less than ±0.05. Therefore, the theoretical equation can accurately predict the thermosyphon’s thermal resistance at different inclination angles.

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Lock, G. S. H., and J. D. Kirchner. "Wind-Augmented Heat Transfer in an Open Thermosyphon Tube With Large Length-Diameter Ratios." Journal of Heat Transfer 112, no. 1 (February 1, 1990): 71–77. http://dx.doi.org/10.1115/1.2910367.

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The paper reports an experimental study of the open thermosyphon tube when its heat transfer performance is augmented by the prevailing wind flowing down the inside of an insert tube concentric with the thermosyphon tube. Data are presented for the large length-diameter ratios characteristic of geotechnical applications. A flow model is developed and used to interpret these and other results. Comparisons are made with the performance of liquid-filled thermosyphons.

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Gómez, Miguel A., Sergio Chapela, Joaquín Collazo, and José L. Míguez. "CFD Analysis of a Buffer Tank Redesigned with a Thermosyphon Concentrator Tube." Energies 12, no. 11 (June 5, 2019): 2162. http://dx.doi.org/10.3390/en12112162.

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This study analyzes a buffer tank simulated in both continuous operation mode and heating mode using CFD techniques. The analysis is focused in the thermal behavior of the tank, especially in parameters such as heat exchanged, heating time, and temperature distributions into the tank, in order to propose a better design. The results of the different simulations show that the tank heats water extremely slowly and extremely evenly when producing domestic hot water (DHW), which negatively affects the thermal stratification that is critical for rapidly reaching the DHW temperature. Therefore, the main problem of the tank is an inefficient heat exchange and a poor distribution of temperature. In order to overcome these operational limitations, a new design is proposed by installing a tube inside the tank that encloses the heating coil and sends hot water directly to the tank top region such that high-temperature DHW is rapidly provided, and thermal stratification is improved. Several simulations are performed with different open and closed configurations for the outlets of the inner tube. The different results show that the heating times significantly improve, and the time needed to reach the 45 °C set point temperature is reduced from 44 to 15 min. In addition, the simulations in which the opening and closing of the water outlets are regulated, the outlet DHW temperature is kept within 45–60 °C, which prevents overheating to unsafe use temperatures. Furthermore, the results of the simulation in continuous operation mode show a clear improvement of thermal stratification and an increase in the heat transmitted to the inside of the tank.

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14

Dobson, R. T., and J. C. Ruppersberg. "Flow and heat transfer in a closed loop thermosyphon. Part I – theoretical simulation." Journal of Energy in Southern Africa 18, no. 4 (August 1, 2007): 32–40. http://dx.doi.org/10.17159/2413-3051/2007/v18i4a3389.

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A natural circulation, closed loop thermosyphon can transfer heat over relatively large distances without any moving parts such as pumps and active controls. Such loops are thus considered suitable for nuclear reactor cooling applications where safety and high reliability are of paramount importance. A theoretical basis from which to predict the flow and heat transfer performance of such a loop is present-ed. A literature survey of the background theory is undertaken and the theoretical equations describing the single and two-phase flow as well as heat trans-fer behaviour are given. The major assumptions made in deriving these equations are that the work-ing fluid flow is quasi-static and that its single, two-phase flow and heat transfer behaviour may be cap-tured by dividing the working fluid in the loop into a number of one dimensional control volumes and then applying the equations of change to each of these control volumes. Theoretical simulations are conducted for single phase, single and two-phase and heat pipe operating modes, and a sensitivity analysis of the various variables is undertaken. It is seen that the theoretical results capture the single and two-phase flow operating modes well for a loop that includes an expansion tank, but not for the heat pipe operating mode. It is concluded that the theo-retical model may be used to study transient and dynamic non-linear effects for single and two-phase modes of operation. To more accurately predict the heat transfer rate of the loop however, loop specific heat transfer coefficients need to be determined experimentally and incorporated into the theoretical model.

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15

Luo, Cheng Long, Ji Hai Xiong, Min Fan, Chong Wei Han, and Li Yuan Sun. "Thermal Effect of Dual-Function Solar Collector on Building in Autumn." Applied Mechanics and Materials 472 (January 2014): 254–58. http://dx.doi.org/10.4028/www.scientific.net/amm.472.254.

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In this study, a numerical study is made on a dual-function solar collector integrated with building when it works in thermosyphon water heating mode with natural circulation. The investigation is achieved to show its thermal effect on the building environment by comparing with cooling/heating loads of the rooms with or without the novel collector for the warm autumn periods. The results show that in autumn the thermal effect of the novel system is not inevitable because the cooling load of the room with the collector has an evidently positive difference and the heating load must reduce.

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16

Arbiyani, Filian. "Numerical Study of a Thermosyphon Cooling System: film condensation." E3S Web of Conferences 42 (2018): 01005. http://dx.doi.org/10.1051/e3sconf/20184201005.

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Studies of condensation in several cooling systems have been conducted. However, the mode of condensation in two-phase cooling systems to achieve a high rate of condensation in compact devices has not been explored. Condensation phenomena, indeed, is a key parameter in designing a thermosyphon water cooled condenser system. The analysis of this condensation phenomena has been done numerically by implementing the governing equations and boundary conditions in commercial MATLAB software. Steady-state laminar film condensation on the radial system is assumed as a condensation phenomenon between vapor and the outer surface of coolant coil. There is a good agreement between experimental and simulation results. Furthermore, for 0.3 LPM 10 °C, it is found the standard deviation of 0.3 %. This small standard deviation indicates the good accuracy of the simulation. At a constant mass flow rate of water, the higher inlet water temperature will result in a higher Nusselt number of water. Furthermore, at the same Nusselt number of water, the lower inlet water temperature obtained a higher film condensation rate. Nusselt number of film condensation increases as the Nusselt number of water decreases at the various constant of mass flow rate of water. Additionally, the lower inlet water temperature will result in a lower Nusselt number of water. The value of Reynold number film condensation increases as Reynold numbers and Nusselt number of water increase. At various constant mass flow rates of the water, at the same Nusselt number of water, the Reynold number of film condensation increases with lower inlet water temperature. The lower inlet water temperature increases the value of Reynold number of film condensation leading to more wavy and turbulent flow. The present study provides guidelines for thermal management engineers to design and fabricate compact cooling systems.

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17

Ma, Guoyuan, Feng Zhou, Ting Liu, Liangbing Wang, Xiaolin Zhang, and Zhongliang Liu. "Study on Optimal Operating Mode of a Thermosyphon Heat Exchanger Unit in a Shopping Center." Journal of Energy Engineering 139, no. 4 (December 2013): 275–80. http://dx.doi.org/10.1061/(asce)ey.1943-7897.0000126.

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18

Zhang, Longcan, Tao Zhang, Gang Pei, and Jie Ji. "Experimental study of the wickless loop thermosyphon solar water heating system under passive and active cycle mode." International Journal of Low-Carbon Technologies 12, no. 3 (February 27, 2017): 256–62. http://dx.doi.org/10.1093/ijlct/ctx001.

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Krasnoshlykov, Alexander. "Numerical investigation of heat transfer in thermosyphon under the emergency mode of operation of lithium-ion batteries of aircraft." MATEC Web of Conferences 141 (2017): 01007. http://dx.doi.org/10.1051/matecconf/201714101007.

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20

Yang, Kai-Shing, Yan-Lin Wu, Yi-Pin Chu, Yu-Lieh Wu, and Shwin-Chung Wong. "Performance Tests on a Novel Un-Finned Thermosyphon Heat Exchanger Requiring Single Charge." Processes 9, no. 6 (June 4, 2021): 995. http://dx.doi.org/10.3390/pr9060995.

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A novel design of an unfinned thermosyphon HPHX having a continuous closed tube loop which requires only a single charge is proposed for industrial waste heat recovery. The HPHX consists of 9×17 straight copper tubes in a staggered arrangement connected by 144 U bends. Without fins, not only are the pressure drops of the cooling air flow limited, but the cost, weight and maintenance effort can be greatly reduced. The thermal performance of this novel thermosyphon HPHX was tested with water at a filling ratio of 40%. The evaporator section is immersed in hot silicone oil, while the condenser section is cooled by air flow. The heat transfer rate (Q) reaches 6.65 kW at a heating pool temperature of 150 °C and a cooling air flow rate (F) of 1600 CMH, when the HPHX attains maximum effective thermal conductivity of 12,798 W/m-K. An ε-NTU theoretical model for single-tube thermosyphons was formulated with the boiling and film condensation modelled by empirical correlations. This model predicts the total resistance Rtot of the HPHX, which decreases with Q and F, with a total error of less than ±10%.

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Mirafiori, Matteo, Marco Tancon, Stefano Bortolin, Alessandro Martucci, and Davide Del Col. "Mechanisms of dropwise condensation on aluminum coated surfaces." Journal of Physics: Conference Series 2177, no. 1 (April 1, 2022): 012046. http://dx.doi.org/10.1088/1742-6596/2177/1/012046.

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Abstract Dropwise condensation (DWC) is a complex phase-change phenomenon involving the formation of randomly distributed droplets on the condensing surface. The promotion of DWC instead of the traditional filmwise condensation (FWC) is a promising solution to enhance the efficiency of heat exchangers by increasing the condensation heat transfer coefficient. The interaction between the condensing fluid and the surface (wettability) is important in defining the condensation mode. On metallic surfaces widely employed in heat transfer applications, the condensing process occurs in filmwise mode. Ideally, an engineered surface designed to achieve high DWC heat transfer coefficients should present low contact angle hysteresis and low thermal resistance. Among the different available techniques to modify the surface wettability, hybrid organic-inorganic sol-gel silica coatings functionalized with hydrophobic moieties (phenyl or methyl groups) have been identified as a feasible solution to promote DWC on metallic surfaces. In the present paper, different aluminum sol-gel coated surfaces have been tested during DWC of steam in saturated conditions. The realized coatings have been characterized by means of dynamic contact angles and coating thickness measurements. Condensation tests have been performed using a two-phase thermosyphon loop operating in steady-state conditions that allows visualization of the condensation process and simultaneous heat transfer measurements. Heat transfer coefficients have been measured by varying the heat flux, at 106 °C saturation temperature and with vapor velocity equal to 2.7 m s−1. A high-speed camera is used for the visualization of the DWC process.

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Yu, Chia-Wang, C. S. Huang, C. T. Tzeng, and Chi-Ming Lai. "Effects of the Aspect Ratio of a Rectangular Thermosyphon on Its Thermal Performance." Energies 12, no. 20 (October 22, 2019): 4014. http://dx.doi.org/10.3390/en12204014.

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The natural convection behaviors of rectangular thermosyphons with different aspect ratios were experimentally analyzed in this study. The experimental model consisted of a loop body, a heating section, a cooling section, and adiabatic sections. The heating and cooling sections were located in the vertical portions of the rectangular loop. The length of the vertical cooling section and the lengths of the upper and lower adiabatic sections were fixed at 300 mm and 200 mm, respectively. The inner diameter of the loop was fixed at 11 mm, and the cooling end temperature was 30 °C. The relevant parameters and their ranges were as follows: The aspect ratios were 6, 4.5, and 3.5 (with potential differences of 41, 27, and 18, respectively, between the cold and hot ends), and the input thermal power ranged from 30 to 60 W (with a heat flux of 600 to 3800 W/m2). The results show that it is feasible to obtain solar heat gain by installing a rectangular thermosyphon inside the metal curtain wall and that increasing the height of the opaque part of the metal curtain wall can increase the aspect ratio of the rectangular thermosyphon installed inside the wall and thus improve the heat transfer efficiency.

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Bieliński, Henryk, and Jarosław Mikielewicz. "Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical side." Archives of Thermodynamics 31, no. 4 (October 1, 2010): 51–59. http://dx.doi.org/10.2478/v10173-010-0027-4.

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Computer cooling using a two phase minichannel thermosyphon loop heated from horizontal and vertical sides and cooled from vertical sideIn the present paper it is proposed to consider the computer cooling capacity using the thermosyphon loop. A closed thermosyphon loop consists of combined two heaters and a cooler connected to each other by tubes. The first heater may be a CPU processor located on the motherboard of the personal computer. The second heater may be a chip of a graphic card placed perpendicular to the motherboard of personal computer. The cooler can be placed above the heaters on the computer chassis. The thermosyphon cooling system on the use of computer can be modeled using the rectangular thermosyphon loop with minichannels heated at the bottom horizontal side and the bottom vertical side and cooled at the upper vertical side. The riser and a downcomer connect these parts. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop is based on mass, momentum, and energy balances in the evaporators, rising tube, condenser and the falling tube. The separate two-phase flow model is used in calculations. A numerical investigation for the analysis of the mass flux rate and heat transfer coefficient in the steady state has been accomplished.

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Harley, C., and A. Faghri. "Complete Transient Two-Dimensional Analysis of Two-Phase Closed Thermosyphons Including the Falling Condensate Film." Journal of Heat Transfer 116, no. 2 (May 1, 1994): 418–26. http://dx.doi.org/10.1115/1.2911414.

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A transient two-dimensional thermosyphon model is presented that accounts for conjugate heat transfer through the wall and the falling condensate film. The complete transient two-dimensional conservation equations are solved for the vapor flow and pipe wall, and the liquid film is modeled using a quasi-steady Nusselt-type solution. The model is verified by comparison with existing experimental data for a low-temperature thermosyphon with good agreement. A typical high-temperature thermosyphon was then simulated to examine the effects of vapor compressibility and conjugate heat transfer.

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Bieliński, Henryk, and Jaroslaw Mikielewicz. "Analysis of Heat Transfer and Fluid Flow in Two-Phase Thermosyphon Loop with Minichannels." Applied Mechanics and Materials 831 (April 2016): 92–103. http://dx.doi.org/10.4028/www.scientific.net/amm.831.92.

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The present paper offers an analysis of heat transfer and fluid flow in two phase thermosyphon loop with minichannels. A one-dimensional model of two-phase flow and heat transfer in a closed thermosyphon loop with minichannels was examined. The created general model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The separate two-phase flow model is used in calculations. The numerical results obtained for the selected heater and cooler using the general model of thermosyphon loop indicate that the mass flux increases with increasing length of the heated section and decreases with increasing length of the cooled section of the loop. It was found that the heat transfer coefficient for flow boiling and flow condensation in the steady state increases with increasing heat flux in the heater and cooler with minichannels, respectively. The design and configuration of heaters and coolers has a considerable impact on the efficiency of thermosyphon loop. These factors make it possible to optimize the computer processor cooling.

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Sulin, A. B., D. V. Evdulov, A. M. Ibragimova, and A. I. Semilyak. "Model of an electronic equipment cooling system based on the joint use of high-current thermoelectric semiconductor batteries and a thermal thermosipho." Herald of Dagestan State Technical University. Technical Sciences 47, no. 4 (January 21, 2021): 81–91. http://dx.doi.org/10.21822/2073-6185-2020-47-4-81-91.

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Objective. The objective of the study is to develop a design model of the electronic equipment cooling system based on the combined use of high-current thermoelectric semiconductor batteries of layered design and an evaporative-condensing thermal thermosyphon, as well as to study the thermophysical processes occurring during its operation.Methods. A mathematical model of the electronic equipment cooling system based on the combined use of high-current layered thermoelectric batteries and an evaporative-condensing thermal thermosyphon is presented. The design model includes a description of heat exchange processes in a layered thermoelectric element at various supply currents, determination of the amount of heat transferred through the cross-section of the channel of a thermal thermosyphon per unit of time, and the temperature values at each channel point.Result. A 2D dynamic heat conduction problem is solved for a complex system with rectangular geometry of fragments and heat sources. The temperature distribution of a thermoelement along its longitudinal axis at different values of the supply current and the change in the heat flow along its length in a thermal evaporation-condensation thermosyphon are studied.Conclusion. The results of the research have shown the effectiveness of combined use of high-current layered thermoelectric batteries and a thermal thermosyphon in electronic equipment with dense element packaging. It is shown that to increase the efficiency of electronic equipment and reduce the heat losses that occur in the heat line when the heat-generating element of radio-electronic equipment and thermoelectric semiconductor batteries are separated by a sufficiently large distance (over 0.6 m), it is advisable to use an evaporative-condensing thermal thermosyphon as a heat line.

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Chang, J. M. "Characteristic Heat Removal Efficiency for Thermosyphon Solar Water Heaters During the System Application Phase." Journal of Solar Energy Engineering 126, no. 3 (July 19, 2004): 950–56. http://dx.doi.org/10.1115/1.1753576.

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The overall performance rating of a thermosyphon solar water heater should take into consideration its heat removal efficiency during the system application phase. This study employs a precise on-line operation to first identify physical heat removal patterns of a thermosyphon solar water heater, and then develops an empirical model for deriving its characteristic heat removal efficiency. This empirical model is in the form of a logarithmic curve, and has a high data correlation coefficient of 0.889 to 0.967. Based upon the empirical model, this study defines a characteristic heat removal efficiency parameter for thermosyphon solar water heaters. Finally, this study establishes a storage tank design method which enables the characteristic heat removal efficiency of the complete system to be optimized.

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Zuo, Zheng, and Qing Hai Luo. "Heat Transfer Analysis on a Thermosyphon Radiator." Advanced Materials Research 347-353 (October 2011): 659–63. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.659.

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Heat transfer of a thermosyphon radiator was analyzed, experimental tests with acetone as working fluid have been performed, and good agreement between measurement and calculation with analysis model was obtained. Compared with conventional radiator by means of experiments and analysis, the advantages and disadvantages of the thermosyphon radiator were discussed.

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Ponomarev, Konstantin O., Geniy V. Kuznetsov, Dmitry V. Feoktistov, Evgenia G. Orlova, and Vyacheslav I. Maksimov. "On heat transfer mechanism in coolant layer on bottom cover of a two-phase closed thermosyphon." Tyumen State University Herald. Physical and Mathematical Modeling. Oil, Gas, Energy 6, no. 1 (2020): 65–86. http://dx.doi.org/10.21684/2411-7978-2020-6-1-65-86.

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The authors hypothesize that the intensity of all thermophysical and hydrodynamic processes in a thermosyphon depends, first of all, on the intensity of heat transfer in the coolant layer on the bottom cover and on the free surface of this layer. Based on the experimentally obtained temperature fields in a two phase closed thermosyphon, the authors have formulated a mathematical model of heat transfer in such heat exchangers which differs from the known models by accounting for conduction and convection only in the coolant layer on the bottom cover and conduction in the evaporation section of the thermosyphon. The calculated temperatures in characteristic points of the coolant layer comply with the readings of thermocouples. The results of numerical simulation provide grounds for concluding that the thermogravitational convection in the coolant layer on the bottom cover plays a dominant role in controlling the intensity of heat transfer in the thermosyphon.

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Wu, Yafeng, Zhe Zhang, Wenbin Li, and Daochun Xu. "Evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons." Thermal Science, no. 00 (2021): 166. http://dx.doi.org/10.2298/tsci200825166w.

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Two-phase closed thermosyphons have good thermal conductivity and are widely used in heat transfer applications. It is essential to establish an effective method for evaluating the steady-state heat transfer performance of two-phase closed thermosyphons, as such a method can help to select appropriate designs and to improve the efficiency of these devices. In this paper, the equivalent thermal conductivity is derived by the principle of equal total thermal resistance, in which the influence of the adiabatic length is eliminated. An evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons is established. Test results of three two-phase closed thermosyphons with total lengths of 220 mm, 320 mm and 500 mm show that as the heat transfer rate increases, the equivalent thermal conductivity of these devices decreases by 28.91%, increases by 6.10% and increases by 10.02%, respectively, among which the minimum value is 831.63 W?m-1?K-1and the maximum value is 1694.19 W?m-1?K-1. The decrease (increase) in the equivalent thermal conductivity in the evaluation model indicates a decrease (increase) in the heat transfer performance. The results show that the equivalent thermal conductivity of the model can effectively evaluate the heat transfer performance of two-phase closed thermosyphons.

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Bieliński, Henryk. "Validation of the generalized model of two-phase thermosyphon loop based on experimental measurements of volumetric flow rate." Archives of Thermodynamics 37, no. 3 (September 1, 2016): 109–38. http://dx.doi.org/10.1515/aoter-2016-0023.

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AbstractThe current paper presents the experimental validation of the generalized model of the two-phase thermosyphon loop. The generalized model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The theoretical analysis and the experimental data have been obtained for a new designed variant. The variant refers to a thermosyphon loop with both minichannels and conventional tubes. The thermosyphon loop consists of an evaporator on the lower vertical section and a condenser on the upper vertical section. The one-dimensional homogeneous and separated two-phase flow models were used in calculations. The latest minichannel heat transfer correlations available in literature were applied. A numerical analysis of the volumetric flow rate in the steady-state has been done. The experiment was conducted on a specially designed test apparatus. Ultrapure water was used as a working fluid. The results show that the theoretical predictions are in good agreement with the measured volumetric flow rate at steady-state.

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Bieliński, Henryk, and Jarosław Mikielewicz. "Application of a two-phase thermosyphon loop with minichannels and a minipump in computer cooling." Archives of Thermodynamics 37, no. 1 (March 1, 2016): 3–16. http://dx.doi.org/10.1515/aoter-2016-0001.

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AbstractThis paper focuses on the computer cooling capacity using the thermosyphon loop with minichannels and minipump. The one-dimensional separate model of two-phase flow and heat transfer in a closed thermosyphon loop with minichannels and minipump has been used in calculations. The latest correlations for minichannels available in literature have been applied. This model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser and the falling tube. A numerical analysis of the mass flux and heat transfer coefficient in the steady state has been presented.

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Lock, G. S. H., and D. Ladoon. "Heat Transfer Characteristics of the Single-Phase, Elbow Thermosyphon." Journal of Heat Transfer 115, no. 1 (February 1, 1993): 173–77. http://dx.doi.org/10.1115/1.2910644.

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This paper describes the results of single-phase experiments on a right-angled, or elbow, thermosyphon with the cooled section upright and the heated section horizontal. For diameter-based Rayleigh numbers less than 107.6, the data indicate the existence of two flow regimes: fully mixed and impeded. A flow model is used to suggest how the cooled section and heated section flow patterns are coupled together. This model satisfactorily explains the effect of geometry on heat transfer, as revealed in the usual plots of Nusselt number versus Rayleigh number. Thermal performance was found to be comparable to that of the linear thermosyphon.

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K. Jasim, Ayoob, Basim H. Abbood, and Mohammed H. Alhamdo. "INVESTIGATIVE STUDY OF THERMAL PERFORMANCE OF THERMOSYPHON SOLAR COLLECTOR." Journal of Engineering and Sustainable Development 25, no. 02 (March 1, 2021): 46–57. http://dx.doi.org/10.31272/jeasd.25.2.6.

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Experimental and Numerical investigation has been performed to improve the thermosyphon thermal performance. Optimization process concentrated on both the water and the operating liquid temperature inside the tank and the thermosyphon. For this purpose, three different models of improvement methods have been studied that depend on increasing the surface area with no changing in the volume of operating liquid. The first one (case-A-) is by add ten ring fins about the absorber pipe. The second method (case-B-) is by add twenty ring fins about the absorber pipe. While, the third way (case-C-) is by add ten ring fins with ten grooves about the absorber pipe. The thermosyphon thermal performance was compared between the traditional model and experimental model. Moreover, numerical simulate for all cases were done with computational fluid dynamic (CFD), ANSYS 19.R3. It was observed through the results that a good convergence between the numerical and, experimental results. Furthermore, the thermal performance for case-A- is found greater than all other cases under study.

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Reed, J. G., and C. L. Tien. "Modeling of the Two-Phase Closed Thermosyphon." Journal of Heat Transfer 109, no. 3 (August 1, 1987): 722–30. http://dx.doi.org/10.1115/1.3248150.

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A comprehensive model is developed to predict the steady-state and transient performance of the two-phase closed thermosyphon. One-dimensional governing equations for the liquid and vapor phases are developed using available correlations to specify the shear stress and heat transfer coefficients. Steady-state solutions agree well with thermosyphon flooding data from several sources and with film thickness data obtained in the present investigation. While no data are available with which to compare the transient analysis, the results indicate that, for most systems, the governing time scale for system transients is the film residence time, which is typically much longer than the times required for viscous and thermal diffusion through the film. The proposed model offers a versatile and comprehensive analysis tool which is relatively simple.

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Wu, Liangyu, Yingying Chen, Suchen Wu, Mengchen Zhang, Weibo Yang, and Fangping Tang. "Visualization Study of Startup Modes and Operating States of a Flat Two-Phase Micro Thermosyphon." Energies 11, no. 9 (August 30, 2018): 2291. http://dx.doi.org/10.3390/en11092291.

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The flat two-phase thermosyphon has been recognized as a promising technique to realize uniform heat dissipation for high-heat-flux electronic devices. In this paper, a visualization experiment is designed and conducted to study the startup modes and operating states in a flat two-phase thermosyphon. The dynamic wall temperatures and gas–liquid interface evolution are observed and analyzed. From the results, the sudden startup and gradual startup modes and three quasi-steady operating states are identified. As the heat load increases, the continuous large-amplitude pulsation, alternate pulsation, and continuous small-amplitude pulsation states are experienced in sequence for the evaporator wall temperature. The alternate pulsation state can be divided into two types of alternate pulsation: lengthy single-large-amplitude-pulsation alternated with short multiple-small-amplitude-pulsation, and short single-large-amplitude-pulsation alternated with lengthy multiple-small-amplitude alternate pulsation state. During the continuous large-amplitude pulsation state, the bubbles were generated intermittently and the wall temperature fluctuated cyclically with a continuous large amplitude. In the alternate pulsation state, the duration of boiling became longer compared to the continuous large-amplitude pulsation state, and the wall temperature of the evaporator section exhibited small fluctuations. In addition, there was no large-amplitude wall temperature pulsation in the continuous small-amplitude pulsation state, and the boiling occurred continuously. The thermal performance of the alternate pulsation state in a flat two-phase thermosyphon is inferior to the continuous small-amplitude pulsation state but superior to the continuous large-amplitude pulsation state.

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Ramos, J. I., and F. Dobran. "Stability analysis of a closed thermosyphon model." Applied Mathematical Modelling 10, no. 1 (February 1986): 61–67. http://dx.doi.org/10.1016/0307-904x(86)90011-9.

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Siqueira, Antônio Marcos de Oliveira, Alexandre Gurgel, Zeji Ge, Fernando Ariel Colque, and Gabriel Siqueira Silva. "A new model for sizing thermosiphon solar heating systems." Research, Society and Development 9, no. 8 (July 9, 2020): e382985673. http://dx.doi.org/10.33448/rsd-v9i8.5673.

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The purpose of this work is to present a simple methodology which enables to size a thermosyphon system without always having to resort to a computational simulation. As a result of many system simulations using the TRNSYS software, whereby several project and equipment parameters were varied, a group of expressions were obtained which allow the determination of the system thermal daily efficiency (monthly average). The developed correlation includes geometric and thermal aspects related to the collector, the storage tank and the connecting pipes, as well as operational data such as thermal load, solar radiation and room temperature. This model is able to optimize several variables that comprise thermosyphon solar water-heating systems for the requirements of particular applications. The resulting correlation shows that the efficiency is a linear function of meteorological conditions, collector quality and parameters related to storage tank volume, volume load (consumption profile) and collector area. The correlation is very useful since it is a simple, fast alternative for the calculation of system efficiency without depending on experimental determination or numerical simulation results. The determination and sizing of the collector area and the volume storage tank that satisfy the required thermal load can be appropriately performed in a simple and fast way by using the proposed correlation.

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Czerwiński, Grzegorz, and Jerzy Wołoszyn. "Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon." Energies 14, no. 12 (June 18, 2021): 3634. http://dx.doi.org/10.3390/en14123634.

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With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

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Huang, B. J., and S. C. Du. "A Performance Test Method of Solar Thermosyphon Systems." Journal of Solar Energy Engineering 113, no. 3 (August 1, 1991): 172–79. http://dx.doi.org/10.1115/1.2930489.

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A method of test for the thermal performance rating of thermosyphon systems is developed in the present study. It is suggested that the overall performance rating of a solar thermosyphon system should include (1) system efficiency test during the energy collecting phase and (2) system cooling loss test during the cooling phase. Both the tests are performed outdoors. The cooling loss test is performed right after the efficiency test. A semi-empirical system efficiency model with a variable (Ti−Ta)/Ht is derived to correlate the daily efficiency test results; while a simple first-order model with a cooling time constant τc is used to evaluate the loss parameter in cooling phase. A method of test is then proposed and an expert system is designed to perform the outdoor tests. It is shown that very good correlation for the system efficiency model is obtained and the system parameters obtained can be used to rate the thermal performance in energy collecting phase; while the thermal performance in cooling phase is rated by examining the time constant τc of the cooling loss model.

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Zanardi, M. A., and N. G. C. Leite. "THEORETICAL MODELING OF A TWO-PHASED THERMOSYPHON ASSUMING THE LIQUID RESERVATORY." Revista de Engenharia Térmica 6, no. 1 (June 30, 2007): 74. http://dx.doi.org/10.5380/reterm.v6i1.61820.

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A theoretical modeling using the mass, momentum and energy conservation equations, about the intrinsic phenomena in the working of a cylindrical geometry two-phase thermosyphon operating on vertical was performed. The conservation equations were solved in steady-state operation for all the phases of the thermosyphon. Then model also assumed the presence of a liquid reservatory whose valves of the coefficient of heat transfer that determine the operation of functioning in the reservatory, were obtained from the correlation published in literature. The set of conservation equations was solved by using the method of finite volumes. The results achieved were checked with experimental data from literature and also from specific experiments performed in laboratory. In a general view, the theoric results matched reasonably well with those ones from the experiments, and the observed deviation were assumed by a inadequate prevision of the reservatory model used, besides keeping a stable level of the reservatory of liquid.

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Zhang, Guoyan, Shengyong Liu, Jie Lu, Jiong Wang, and Yongtao Ma. "Numerical Simulation of Diffusion Absorption Refrigerator." E3S Web of Conferences 233 (2021): 01044. http://dx.doi.org/10.1051/e3sconf/202123301044.

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Based on Fluent software, a mathematical model of thermosyphon pump is established and numerical simulation is carried out to study the influence of riser tube length, tube diameter and immersion ratio on liquid lifting capacity and efficiency. The results showed that: the liquid lifting volume increased with the increase of immersion ratio, whereas the lifting efficiency showed a trend of increasing followed by decreasing. The highest lifting efficiency for a 340mm long, 6mm diameter riser achieved when the immersion ratio is 0.35. With the increasing of the height in riser, the velocity of the gas phase close to the wall in the thermosyphon pump was higher than the velocity along the radial direction. In order to enhance fluid interchange, corners of the refrigeration box were designed to be arc-shaped with a higher corner speed and lower temperature.

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Bar-Cohen, A., and H. Schweitzer. "Thermosyphon Boiling in Vertical Channels." Journal of Heat Transfer 107, no. 4 (November 1, 1985): 772–78. http://dx.doi.org/10.1115/1.3247503.

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The high heat flux capability and modest temperature differences associated with boiling heat transfer make immersion cooling one of the primary candidates for VHSIC and VLSI microelectronic component thermal control. While the literature contains many references to pool boiling heat transfer from single integrated circuit packages or transistor cans, there is as yet little information on ebullient thermal transport from vertical arrays of parallel, densely packaged Printed Circuit Boards or ceramic modules. The present study represents an attempt to explore the thermal performance of such ebullient cooling systems by analytically and empirically investigating boiling heat transfer in water from a pair of flat, isoflux plates. Experimental results for wall temperature as a function of axial location, heat flux, and plate spacing are presented. A theoretical model for liquid flow rate through the channel is developed and used as a basis for correlating the rate of heat transfer from the channel walls.

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44

Den Braven, Karen R. "Two-Phase Heat Transfer in Thermosyphon Evacuated-Tube Solar Collectors." Journal of Solar Energy Engineering 111, no. 4 (November 1, 1989): 292–97. http://dx.doi.org/10.1115/1.3268324.

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This work analyzes the heat transfer within a tilted thermosyphon and its use in a heat pipe evacuated-tube solar collector. A detailed examination is made of the laminar film condensation process, including the effects of interfacial shear due to the moving vapor. Effects of film surface waves are later included. Including the shear term in the constitutive equations changes the predicted film thickness in the condenser portion of the device by less than one percent, depending on location along the surface. This change causes only a slight increase in the predicted heat transfer. Accounting for surface waves increases the heat transfer rate 10 percent to 50 percent in the Reynolds number range studied. The condenser results are combined with a simple trough model for the evaporator portion of the thermosyphon to give the effective heat-transfer coefficient for the entire tube. Predicted performances of the condenser, the evaporator, and the entire tube compare favorably with available data.

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Kishor, Nand, Mihir Kr Das, Anirudha Narain, and Vibhaw Prakash Ranjan. "Fuzzy model representation of thermosyphon solar water heating system." Solar Energy 84, no. 6 (June 2010): 948–55. http://dx.doi.org/10.1016/j.solener.2010.03.002.

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Jiménez-Casas, A. "A coupled ODE/PDE system governing a thermosyphon model." Nonlinear Analysis: Theory, Methods & Applications 47, no. 1 (August 2001): 687–92. http://dx.doi.org/10.1016/s0362-546x(01)00212-7.

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Azzolin, Marco, Andrea Mariani, Lorenzo Moro, Andrea Tolotto, Paolo Toninelli, and Davide Del Col. "Mathematical model of a thermosyphon integrated storage solar collector." Renewable Energy 128 (December 2018): 400–415. http://dx.doi.org/10.1016/j.renene.2018.05.057.

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Huang, Cho-Ning, Kuan-Lin Lee, Calin Tarau, Yasuhiro Kamotani, and Chirag R. Kharangate. "Computational fluid dynamics model for a variable conductance thermosyphon." Case Studies in Thermal Engineering 25 (June 2021): 100960. http://dx.doi.org/10.1016/j.csite.2021.100960.

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Cammarata, L., A. Fichera, and A. Pagano. "Designing an optimal controller for rectangular natural circulation loops." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 217, no. 3 (August 1, 2003): 171–80. http://dx.doi.org/10.1243/095440803322328845.

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Controlling the dynamics of natural circulation loops represents a major task for the widespread use of this kind of system in safe industrial applications. This paper aims to design an innovative model-based optimal controller for the suppression of unstable oscillations and flow reversals, which affect the dynamical behaviour of a closed-loop thermosyphon at high heating rate. The key idea is to define a multivariable control law aiming to minimize an objective function taking into account both the stability of the system and the cost of control. The design of the proposed controller has been based on a model approximating to the first three modes of the dynamics of rectangular circulation loops with imposed heat fluxes at the boundaries. The capability of the proposed controller in suppressing undesired dynamics has been experimentally demonstrated.

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Iliev, Iliya, Angel Terziev, Hristo Beloev, and Christiyan Iliev. "Specifics in the operating modes of thermosyphon air heater of steam generators №1 and №2 in TPP "Republika" at fuel switch from coal to natural gas." E3S Web of Conferences 85 (2019): 01003. http://dx.doi.org/10.1051/e3sconf/20198501003.

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A fuel switch is motivated both by the necessity of increasing energy efficiency and the compliance with the ever-stricter regulations regarding the release of harmful emissions in the environment. In this paper a thorough financial and energy analysis on the fuel switch from coal to natural gas is carried out, in particular with respect to waste heat recovery systems (two phase thermosyphons). As a result of the calculation of the heat transfer coefficients for both fuels, it is established that the system running on natural gas has a lower value, due to the lower air velocity, caused in turn by the lower requirement for excess air. The heat transfer coefficients of the evaporation and condensation zones respectively are established hfgas=104.9 И hair=84.9 (W/m2.K) for coal and hfgas И hair =84.7 (W/m2.K) respectively for gas. A numerical study is also carried out and a methodology for the analysis of the efficiency of two phase thermosyphons with complex geometry is presented.

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Journal articles on the topic 'Thermosyphon mode'

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