Abstract：[Objective] Rectangular channels are widely used in energy power, petroleum, and chemical systems due to their compact structure and high heat exchange efficiency. In heat exchangers and reactor cores that use rectangular flow channels, the channels are separated from each other, which could result in instability phenomena under certain working conditions. Existing research shows that the coupling structure can distribute heat among the channels based on their respective heat transfer characteristics. Heat conduction through the wall can reduce the wall temperature fluctuations, reduce peak wall temperatures in the dried-out state, and improve the stability of the system. Given the fact that wall coupling heat transfer between parallel channels improves system stability, this study aims to explore the influence of coupled heat transfer on the flow instability of parallel rectangular channels, which has high research value.[Methods] In this paper, the thermal-hydraulic program REALP5/MOD3.3 was used to analyze the flow instability characteristics of the parallel channel, and the independent and coupled heating conditions were realized by changing the thermal components. The objects used in this paper are parallel rectangular channels with a heating length of 1 000 mm and a cross-section of 40.0 mm×2.0 mm; a coupled heat transfer wall with 40.0, 2.0, and 1 000.0 in width, thickness, and height, respectively; an axial grid size of 40 mm in size; and a grid size of 0.5 mm in the direction of the thickness of the coupled heat transfer wall. The influence of the coupled heat transfer on the flow instability of parallel channels was studied based on the ratio of heat transfer of the coupling wall and the heat transfer inside the fluid medium during a flow oscillation cycle. Accordingly, the influence of thermal parameters such as system pressure, mass flow rate, and inlet subcooling of the parallel-channel system coupled with heat transfer on the flow instability boundary parameters was studied.[Results] (1) The heat transfer through the coupling heat transfer wall was less than that of the fluid in the unstable process, making it difficult to eliminate the flow instability between channels. (2) The instability boundary of the coupled rectangular channel was slightly higher than that of the separation channel due to the influence of heat transfer through the wall, and the stability of the system was higher before instability occurred. (3) The boundary power increased almost linearly as the mass flow rate increased. This was primarily because the length of the single-phase section and the proportion of frictional pressure drop increased with an increase in the mass flow rate, enhancing the overall stability of the system. (4) Given the same pressure and flow rate, the difference in the density of the fluid at the inlet and outlet of the rectangular channel and the accelerated pressure drop decreased, and the stability of the parallel rectangular channel was enhanced with an increase in the inlet subcooling degree. (5) Given the same inlet subcooling degree and flow, with the increase in system pressure, the density and kinematic viscosity differences and frictional pressure drop of the vapor and liquid phases decreased, and the overall stability of the system was enhanced with an increase in the system pressure.[Conclusions] The instability boundary parameters of the coupled and separated rectangular channels are similar; however, the system stability of the coupled rectangular channels is higher before instability occurs. The influence of thermal parameters on the instability boundary is similar for coupled heat transfer parallel rectangular channels and separated channels. Furthermore, increasing the system pressure, mass flow rate, and inlet subcooling can enhance the stability of the system.
胡钰文, 闫晓, 宫厚军, 王艳林, 周磊. 耦合传热并联矩形通道流动不稳定性数值研究[J]. 清华大学学报（自然科学版）, 2023, 63(8): 1257-1263.
HU Yuwen, YAN Xiao, GONG Houjun, WANG Yanlin, ZHOU Lei. Numerical study on flow instability in parallel rectangular channels with coupled heat transfer. Journal of Tsinghua University(Science and Technology), 2023, 63(8): 1257-1263.
[1] LEDINEGG M. Instability of flow during natural and forced circulation[J]. Die Wärme, 1938, 61(8):891-898.(查阅网上资料,未找到对应的期号信息,请确认) [2] BOURE J A, BERGLES A E, TONG L S. Review of two-phase flow instability[J]. Nuclear Engineering and Design, 1973, 25(2):165-192. [3] SAHA P, ISHII M, ZUBER N. An experimental investigation of the thermally induced flow oscillations in two-phase systems[J]. ASME Journal of Heat Transfer, 1976, 98(4):616-622. [4] FUKUDA K, KOBORI T. Classification of two-phase flow instability by density wave oscillation model[J]. Journal of Nuclear Science and Technology, 1979, 16(2):95-108. [5] KAKAC S, BON B. A review of two-phase flow dynamic instabilities in tube boiling systems[J]. International Journal of Heat and Mass Transfer, 2008, 51(3-4):399-433. [6] 陈冲, 高璞珍, 谭思超, 等. 窄矩形通道内Ledinegg不稳定性实验研究[J]. 原子能科学技术, 2014, 48(8):1411-1415. CHEN C, GAO P Z, TAN S C, et al. Experimental study on Ledinegg flow instability in rectangular narrow channel[J]. Atomic Energy Science and Technology, 2014, 48(8):1411-1415. (in Chinese) [7] 王艳林, 陈炳德, 黄彦平, 等. 平行窄隙矩形通道间脉动演化过程的实验研究[J]. 核动力工程, 2011, 32(5):75-79. WANG Y L, CHEN B D, HUANG Y P, et al. Experimental research on evolvement of density wave oscillation in parallel narrow rectangular channels[J]. Nuclear Power Engineering, 2011, 32(5):75-79. (in Chinese) [8] 余志庭. 摇摆条件下窄矩形通道内流动不稳定性研究[D]. 哈尔滨:哈尔滨工程大学, 2016. YU Z T. Study of flow instabilities in a rectangular mini-channel under rolling motion condition[D]. Harbin:Harbin Engineering University, 2016. (in Chinese) [9] 唐瑜, 陈炳德, 熊万玉, 等. 矩形并联双通道第一类密度波流动不稳定性实验研究[J]. 核动力工程, 2014, 35(3):26-30. TANG Y, CHEN B D, XIONG W Y, et al. Experimental study on type Ⅰ density wave oscillation in parallel twin rectangular channels under forced circulation[J]. Nuclear Power Engineering, 2014, 35(3):26-30. (in Chinese) [10] 唐瑜, 陈炳德, 熊万玉, 等. 倾斜条件下并联矩形通道流动不稳定性实验研究[J]. 原子能科学技术, 2016, 50(9):1600-1605. TANG Y, CHEN B D, XIONG W Y, et al. Experimental investigation on flow instability in parallel rectangular channel on inclined condition[J]. Atomic Energy Science and Technology, 2016, 50(9):1600-1605. (in Chinese) [11] 陈娟, 周涛, 齐实, 等. 矩形通道自然循环流动不稳定性实验研究[J]. 核动力工程, 2017, 38(2):51-55. CHEN J, ZHOU T, QI S, et al. Experimental study of natural circulation flow instability in rectangle channels[J]. Nuclear Power Engineering, 2017, 38(2):51-55. (in Chinese) [12] 孙汝雷, 张大林, 周健成, 等. 窄矩形通道两相流动沸腾压降特性实验研究[J]. 原子能科学技术, 2020, 54(9):1537-1549. SUN R L, ZHANG D L, ZHOU J C, et al. Experimental study on two-phase flow boiling pressure drop characteristics in narrow rectangular channel[J]. Atomic Energy Science and Technology, 2020, 54(9):1537-1549. (in Chinese) [13] 陈冲. 单矩形通道内自然循环流动特性实验研究[J]. 舰船科学技术, 2021, 43(21):139-142. CHEN C. Experimental study on flowcharacteristics of natural circulation in a single rectangular channel[J]. Ship Science and Technology, 2021, 43(21):139-142. (in Chinese) [14] 吴廉巍, 陈冲, 吴炜, 等. 摇摆对窄矩形通道内流量波动特性的影响[J]. 舰船科学技术, 2021, 43(13):74-77. WU L W, CHEN C, WU W, et al. Effects of rolling motion on fluctuation characteristics of flow rate in a rectangular narrow channel[J]. Ship Science and Technology, 2021, 43(13):74-77. (in Chinese) [15] FLYNN R D, FOGG D W, KOO J M, et al. Boiling flow interaction between two parallel microchannels[C]//Proceedings of the ASME 2006 International Mechanical Engineering Congress and Exposition. Chicago, USA:ASME, 2006:317-322. [16] VAN OEVELEN T, WEIBEL J A, GARIMELLA S V. The effect of lateral thermal coupling between parallel microchannels on two-phase flow distribution[J]. International Journal of Heat and Mass Transfer, 2018, 124:769-781. [17] JIN Q, WEN J T, NARAYANAN S. Temperature synchronization across parallel microchannels during flow boiling[J]. International Journal of Thermal Sciences, 2020, 156:106476. [18] CHISHOLM D. A theoretical basis for the Lockhart-Martinelli correlation for two-phase flow[J]. International Journal of Heat and Mass Transfer, 1967, 10(12):1767-1778. [19] LOCKHART R W, MARTINELLI R C. Proposed correlation of data for isothermal two-phase, two-component flow in pipes[J]. Chemical Engineering Progress, 1949, 45(1):39-48. [20] COLEBROOK C F. Turbulent flow in pipes, with particular reference to the transition region between the smooth and rough pipe laws[J]. Journal of the Institution of Civil Engineers, 1939, 11(4):133-156. [21] ZIGRANG D J, SYLVESTER N D. A review of explicit friction factor equations[J]. Journal of Energy Resources Technology, 1985, 107(2):280-283.
2023, Vol. 63 
