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The natural circulation loop (NCL) consists of a thermal-hydraulic system that convoys thermal energy from a heat source to a heat sink without a pump. Applications of those loops can be found in solar energy, geothermal, nuclear reactors, and electronic cooling. The lattice Boltzmann method is a numerical method that can simulate thermal-fluid dynamics, using a mesoscopic approach based on the Boltzmann equation for the density function. A square NCL model with fixed temperatures at the heater and heat sink sections was developed in a bi-dimensional lattice with double distribution dynamics, one distribution for the hydrodynamic field and the other for the thermal field. The different cooler–heater configurations (vertical or horizontal) were investigated. We found that by positioning the source or sink vertically, the flow direction can be controlled. In contrast, in a loop with symmetric horizontal heater - horizontal cooler configuration where both fluid directions are equally probable. The effectiveness of the loop was studied by calculating the heat sink temperature gradient. The lower value was obtained for the horizontal heater horizontal cooler orientation (0.71) and the higher value for the vertical heater vertical cooler configuration with an increment of 34%; simultaneously, the flow rate (Reynolds number) was reduced by 47%.
end heat exchanger, heater orientation, heat sink orientation, LBM, thermosyphon
[1] Náñez Alonso, S.L., Jorge-Vázquez, J., Echarte Fernández, M.Á. & Reier Forradellas, R.F., Cryptocurrency mining from an economic and environmental perspective. Analy- sis of the most and least sustainable countries. Energies, 14, pp. 4254, 2021. https://doi. org/10.3390/en14144254
[2] de Vries, A., Bitcoin’s growing energy problem. Joule, 2, pp. 801–805, 2018. https:// doi.org/10.1016/j.joule.2018.04.016
[3] Huang, P., Copertaro, B., Zhang, X., Shen, J., Löfgren, I., Rönnelid, M., Fahlen, J., Andersson, D. & Svanfeldt, M., A review of data centers as prosumers in district energy systems: renewable energy integration and waste heat reuse for district heating. Applied Energy, 258, pp. 114109, 2020. https://doi.org/10.1016/j.apenergy.2019.114109
[4] Ju, X., Xu, C., Liao, Z., Du, X., Wei, G., Wang, Z. & Yang, Y., A review of concentrated photovoltaic-thermal (CPVT) hybrid solar systems with waste heat recovery (WHR). Science Bulletin, 62, pp. 1388–1426, 2017. https://doi.org/10.1016/j.scib.2017.10.002
[5] Al-kayiem, H.H., Hybrid techniques to enhance solar thermal: the way forward. Int. J.EQ., 1, pp. 50–60, 2015. https://doi.org/10.2495/EQ-V1-N1-50-60
[6] Satou, A. Madarame, H. & Okamoto, k., Unstable behavior of single-phase natural circulation under closed loop with connecting tube. Experimental Thermal and Fluid Science, 7, 2001.
[7] Misale, M., Bocanegra, J.A., Borelli, D. & Marchitto, A., Experimental analysis of four parallel single-phase natural circulation loops with small inner diameter. Applied Thermal Engineering, 180, pp. 115739, 2020. https://doi.org/10.1016/j.appltherma- leng.2020.115739
[8] Dass, A. & Gedupudi, S., Numerical investigation on the heat transfer coefficient jump in tilted single-phase natural circulation loop and coupled natural circulation loop. International Communications in Heat and Mass Transfer, 120, pp. 104920, 2021. https://doi.org/10.1016/j.icheatmasstransfer.2020.104920
[9] Misale, M., Overview on single-phase natural circulation loops, in: International Con- ference on Advances in: Mechanical & Automation Engineering, Rome, Italy, 2014: p. 13.
[10] Misale, M., Devia, F. & Garibaldi, P., Experiments with Al2O3 nanofluid in a single- phase natural circulation mini-loop: Preliminary results. Applied Thermal Engineering, 40, pp. 64–70, 2012. https://doi.org/10.1016/j.applthermaleng.2012.01.053
[11] Garibaldi, P. & Misale, M., Experiments in single-phase natural circulation miniloops with different working fluids and geometries. J. Heat Transfer, 130, pp. 104506, 2008. https://doi.org/10.1115/1.2948393
[12] Vijayan, P.k., Experimental observations on the general trends of the steady state and stability behaviour of single-phase natural circulation loops. Nuclear Engineering and Design, 215, pp. 139–152, 2002. https://doi.org/10.1016/S0029-5493(02)00047-X
[13] Misale, M., Experimental study on the influence of power steps on the thermohydraulic behavior of a natural circulation loop. International Journal of Heat and Mass Transfer, 99, pp. 782–791, 2016. https://doi.org/10.1016/j.ijheatmasstransfer.2016.04.036
[14] Misale, M. & Frogheri, M., Influence of pressure drops on the behavior of a single- phase natural circulation loop: preliminary results. International Communications in Heat and Mass Transfer, 26, pp. 597–606, 1999. https://doi.org/10.1016/S0735- 1933(99)00046-9
[15] Cheng, H., Lei, H. & Dai, C., Thermo-hydraulic characteristics and second-law analy- sis of a single-phase natural circulation loop with end heat exchangers. International Journal of Thermal Sciences, 129, pp. 375–384, 2018. https://doi.org/10.1016/j.ijther- malsci.2018.03.026
[16] Misale, M., Bocanegra, J.A. & Marchitto, A., Thermo-hydraulic performance of con- nected single-phase natural circulation loops characterized by two different inner diam- eters. International Communications in Heat and Mass Transfer, 125, p. 105309, 2021. https://doi.org/10.1016/j.icheatmasstransfer.2021.105309
[17] Arumuga Perumal, D. & Dass, A.k., Simulation of flow in two-sided lid-driven square cavities by the lattice Boltzmann method, in: The New Forest, Uk, 2008: pp. 45–54. https://doi.org/10.2495/AFM080051
[18] Bocanegra Cifuentes, J.A., Borelli, D., Cammi, A., Lomonaco, G. & Misale, M., Lattice Boltzmann method applied to nuclear reactors—a systematic literature review. Sustain- ability, 12, p. 7835, 2020. https://doi.org/10.3390/su12187835
[19] Sousa, A.C.M., Hadavand, M. & Nabovati, A., Three-dimensional simulation of slip- flow and heat transfer in a microchannel using the lattice Boltzmann method, in: Tal- linn, Estonia, pp. 75–85, 2010. https://doi.org/10.2495/HT100071
[20] Guo, Z., Shi, B. & Zheng, C., A coupled lattice BGk model for the Boussinesq equa- tions. Int. J. Numer. Meth. Fluids, 39, pp. 325–342, 2002. https://doi.org/10.1002/ fld.337
[21] Succi, S., The Lattice Boltzmann Equation for Fluid Dynamics and Beyond, Clarendon Press, Oxford, England, 2001.
[22] Succi, S., Benzi, R. & Massaioli, F., A review of the Lattice Boltzmann method. Inter- national Journal of Modern Physics C, 4, pp. 409–415, 1993.
[23] Arumuga Perumal, D. & Dass, A.k., A review on the development of lattice Boltzmann computation of macro fluid flows and heat transfer. Alexandria Engineering Journal, 54, pp. 955–971, 2015. https://doi.org/10.1016/j.aej.2015.07.015
[24] Latt, J., Malaspinas, O., kontaxakis, D., Parmigiani, A., Lagrava, D., Brogi, F., Bel- gacem, M.B., Thorimbert, Y., Leclaire, S., Li, S., Marson, F., Lemus, J., kotsalos, C., Conradin, R., Coreixas, C., Petkantchin, R., Raynaud, F., Beny, J. & Chopard, B., Pala- bos: Parallel Lattice Boltzmann Solver. Computers & Mathematics with Applications, p. S0898122120301267, 2020. https://doi.org/10.1016/j.camwa.2020.03.022
[25] Cheng, H., Lei, H., Zeng, L. & Dai, C., Theoretical and experimental studies of heat transfer characteristics of a single-phase natural circulation mini-loop with end heat exchangers. International Journal of Heat and Mass Transfer, 128, pp. 208–216, 2019. https://doi.org/10.1016/j.ijheatmasstransfer.2018.08.136
[26] Vijayan, P.k., Sharma, M. & Saha, D., Steady state and stability characteristics of single-phase natural circulation in a rectangular loop with different heater and cooler orientations. Experimental Thermal and Fluid Science, 31, pp. 925–945, 2007. https:// doi.org/10.1016/j.expthermflusci.2006.10.003
[27] Chen, L., Zhang, X.-R. & Jiang, B., Effects of heater orientations on the natural circula- tion and heat transfer in a supercritical CO2 rectangular loop. Journal of Heat Transfer, 136, p. 052501, 2014. https://doi.org/10.1115/1.4025543