ScienceDirect is a registered trademark of Elsevier B.V. Click here to go back to the article page. The editor and reviewer's affiliations are the latest provided on their Loop research profiles and may not reflect their situation at the time of review. Figure 8A shows the variation of total temperature difference of heat pipe under the different heating power conditions. This model does not directly calculate the vapor flow in the vapor space, however, the evaporation, the condensation, and vapor flow rate can be obtained using the simplified method mentioned in Section 2.2.2. doi:10.1007/s11431-021-1874-0, Lee, C. S., Lee, D. I., and Bonilla, C. F. (1969). Oxford, United Kingdom: Butterworth-Heinemann. For example, the network model cannot consider the nonuniform heat transfer between the heat pipe and the environment. Meanwhile, the nonstandard operation during the experiment will also lead to uncertainty of the results.
Poston, D. I. Meanwhile, to ensure the safety of heat transport, there are a large number of high-temperature heat pipes in the reactor core. FIGURE 11. Lumped Parameter Model of Sintered Heat Pipe: Transient Numerical Analysis and Validation. However, the proposed model can consider the nonuniformity of temperature on contact surface. Zuo divided the heat pipe into several subregions, and the lumped temperature was used to represent the real temperature of specific subregions. 90, 547552. From that, it can be concluded that there is a slight difference between the two results, and proposed model is suitable for the analysis of heat pipe cooled reactor system. This type of reactor system has the advantages of having a compact structure and high safety. Heat Pipe Failure Accident Analysis in Megawatt Heat Pipe Cooled Reactor. This is because heat pipes absorb less power, leading to the increase of Na inventory in the reactor (Poston, 2017). 
Figure 13 shows the axial distribution of power density obtained by Monte Carlo code RMC. here Thermodynamic and Transport Properties of Sodium Liquid and Vapor. (A) T = 0.0s. When the reactor shuts down, decay heat can be taken out of the reactor core through the decay heat exchanger. Using a high-temperature adhesive, all K-type armored thermocouples are fixed in the groove (Figure 5A). Tech. 139, 2534. 
Then, the temperature is recorded with the increase of heating power. For radiation of wall, it is treated as the radiant heat transfer to infinite space (Eq.
CFD Simulation on the Heat Transfer and Flow Characteristics of a Microchannel Separate Heat Pipe under Different Filling Ratios. The Clausius-Clapeyron equation is chosen to describe the relationship between temperature and pressure (Brown, 1951): Changing Eq. 
Ohse, R. W. (1985). unpublished data. J. In this paper, the super thermal conductivity model (STCM) for high-temperature heat pipe is proposed, which simplifies the vapor flow and heat transport in vapor space into heat conductance. Heat Mass Transfer 57 (2), 642656. CFD modeling and calculation have gradually become the main method for heat pipe analysis. (1967). (2020). Thermionic Conversion Specialist Conference, This article is part of the Research Topic, https://doi.org/10.3389/fenrg.2022.819033. Copyright 2022 Guo, Su, Li and Wang. doi:10.2298/tsci100331023a, Asmaie, L., Haghshenasfard, M., Mehrabani-Zeinabad, A., and Nasr Esfahany, M. (2013). Three-dimensional CFD model of the experimental system. Benefiting from the reactivity feedback of fuel, fission power gradually decreases to slow the rate of temperature rise. Heat Transfer 114 (Nov), 10281035. Parameter description of sodium heat pipe. (A) Temperature distribution of heat pipe (B) Wall temperature variation with time. who will be happy to help. The difference between two results can be approximately considered to be caused by the uncertainty of parameters used in the model and the uncertainty of the experimental system.
Front. So far, proposed conceptual designs of heat pipe cooled reactor systems include the kilopower reactor system (McClure et al., 2020a), the Heatpipe-Operated Mars Exploration Reactor (HOMER) system (Poston, 2001), and the Heat Pipe-segmented Thermoelectric Module Converters Space Reactor (HP-STMCs) system (El-Genk and Tournier, 2004). Therm. For load-following transient calculation, calculated results are in good agreement with the experimental results, showing the applicability of the proposed model to this type of reactor system. From Figure 8B, it can also be found that although there is an insulating layer wrapped outside the adiabatic section, the high-temperature vapor will still be partially condensed in this section, resulting in the reduction of vapor flow rate in vapor space. Considering the high temperature of the condenser section, not only the natural convection, but the radiation heat transfer also exist. Experimental Investigation and CFD Analysis of a Air Cooled Condenser Heat Pipe. Reay, D., McGlen, R., and Kew, P. (2013). Wang, C., Sun, H., Tang, S., Tian, W., Qiu, S., and Su, G. (2020). Sci. Even if the power is high enough, generated vapor can quickly transport heat to the condenser, meaning the heat pipe shows excellent isothermal property and efficient heat transfer capability. In this model, the recommended equations for heat transfer limitations are adopted (Busse, 1973; Levy, 1968; Deverall et al., 1970; Tien and Chung, 1979): Pv is the vapor pressure, Av is the cross-sectional area of vapor space, is the specific ratio, Rv is the gap constant, is the surface tension coefficient, rc is the capillary radius, is the angle of inclination, fl is the friction coefficient of liquified working medium, and fv is the friction coefficient of vapor. Heat generated in the reactor core is absorbed by high-temperature heat pipes. Numer. All authors contributed to manuscript revision, read, and approved the submitted version. At about T = 300.0s, fuel reaches the peak temperature of about 1,080.3K. At about T = 2,200.0s, the reactor reaches the new steady state. 1), S13S30. Heat Mass Transfer 41 (11), 14731484. The heating system for high-temperature heat pipe is established to validate this model. Proc. Tech. Schematic diagram of heating system. The difference between the two values is the heat leakage through shield. The complex two-phase flow and heat transfer also brings challenges to the numerical calculation of heat pipe. KRUSTY Reactor Design. When heating power is 1600W, it takes about 13min to enter the quasi-steady state; when heating power is 3000W, it takes only about 7min. The uncertainty of an experimental system is inevitable. Creative Commons Attribution License (CC BY). Basic constitution of a heat pipe cooled reactor (Mcclure, 2015).
FIGURE 3. In this section, the proposed model will be used for numerical simulation of KRUSTY reactor. Heat pipes using alkali metal can realize efficient heat transport in special environments with high temperature (Faghri, 2014). (Please check your downloads folder shortly for your download). It includes the iron-chrome wire heater, the holding device, the angle controlling derive, and the temperature data collection.
Phys. FIGURE 9.
Ann. (A) Proposed model. to go back to the article page.Or contact our KRUSTY Experiment: Reactivity Insertion Accident Analysis. Meanwhile, the detailed information about this experiment is inadequate, and the three-dimensional modeling and the setting of boundary conditions may not be accurate enough. The uncertainty of boundary conditions will directly lead to the deviation of calculated temperature. (2020).
is the density, C is the heat capacity, is the thermal conductivity coefficient, is the porosity, the subscripts of equ means the equivalent value, f means the fluid value, and wc is the wick mesh value. doi:10.1016/j.net.2019.06.021, Yan, B. H., Wang, C., and Li, L. G. (2020). Both the self-diffusion model and the plat-front model consider the two-phase flow and heat transfer in the pipe. The applicability of this model will be discussed. 25 into the differential form: The heat transfer length along the axial direction is selected as the effective length of heat pipe (Reay et al., 2013): Combining Fouriers Law, the equivalent thermal conductivity in vapor space can be obtained: During the operation of heat pipe, the possible heat transfer limitations include the viscosity limit, the sonic limit, the entrainment limit, and the capillary limit. FIGURE 2. Moreover, for reactor systems with higher power density and more complex heat pipe arrangement, it can be expected that the temperature non-uniform effect of the contact surface will have a more significant impact on the operation of the reactor.
Washington, DC: Hemispere Publishing Corporation. The typical heat pipe cooled reactor named KRUSTY is chosen as the research object. Lemont, IL, United States: Argonne National Lab, Guo, Y. C., Li, Z. G., Wang, K., and Su, Z. doi:10.5098/fhp.5.1, Ferrandi, C., Iorizzo, F., Mameli, M., Zinna, S., and Marengo, M. (2013). During the experiment, heat pipe is firstly heated to 1200W to ensure the full startup of heat pipe. The thermophysical properties are determined by two materials. Nucl. To simplify the modeling, the lift table and support structure are all ignored; only the reactor is established (Figure 11). Combined with the recommended heat transfer limitation model (Busse, 1973; Levy, 1968; Deverall et al., 1970; Tien and Chung, 1979), the fast calculation of heat pipe performance and the evaluation of heat pipe safety are realized. Backflow calculation using network model. HPTAMheatpipe Transient Analysis Model: an Analysis of Water Heat Pipes. Transfer 49 (5), 667678. For example, for wick with a mesh type, the density, specific heat capacity, and thermal conductivity can be approximately described by Eqs 57 (Chi, 1976). doi:10.1007/s00231-013-1110-6, Brown, O. L. I. The reason for this phenomenon is the uneven power distribution in space. With the development of high-performance computers, there are more studies on heat pipe simulation using the CFD method (Annamalai and Ramalingam, 2011; Asmaie et al., 2013; Lin et al., 2013; Yue et al., 2018). It directly affects the actual temperature distribution of the core (Figure 13). Temperature distribution of heat pipe (3000W). The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation. In total, eight sodium heat pipes are used to transport heat to the generators. (2014). Thermal Performance Analysis of Nanofluids in a Thermosyphon Heat Pipe Using CFD Modeling. Sci. (1993). The heating experiments with different heating powers is tested.
Therefore, it is important for the numerical calculation of heat pipe cooled reactor to obtain the accurate temperature distribution as much as possible. Nucl. No use, distribution or reproduction is permitted which does not comply with these terms. Energ. The physical processes such as heat conduction, evaporation, condensation, and vapor flow in the heat pipe can be modeled and calculated. From Figure 7B, it can also be seen that with the continuous increase of heating power, operating temperature of heat pipe will be higher, resulting in the faster response of heat pipe. Alkali metal has the characteristics of having a high boiling point and large latent heat of vaporization.