Experimental Study on Pool Boiling Heat Transfer of Cr-coated Zirconium Cladding
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摘要: 铬(Cr)涂层锆合金包壳被认为是最有前途的耐事故燃料(ATF)包壳材料之一,这种材料的表面状态对传热性能的影响程度将极大地影响着涂层锆包壳的工艺优化方向。本文在常压下的Cr涂层锆合金包壳池式沸腾实验装置中对不同工艺方法下制备的Cr涂层锆合金包壳进行实验,研究了粗糙度等表面状态对传热的影响规律及其机制。结果表明,表面粗糙度的提高能降低汽化核心产生的条件,在相同壁面过热度下可显著强化传热。在本文研究参数范围内,随着传热表面粗糙度的提高,临界热流密度(CHF)相应地呈上升趋势,增加表面粗糙度能有效提高CHF值。在此基础上,本文还建立了粗糙度对传热系数影响的预测关系式。
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关键词:
- 耐事故燃料(ATF) /
- 铬(Cr)涂层锆合金包壳 /
- 粗糙度 /
- 沸腾曲线 /
- 临界热流密度
Abstract: Chromium (Cr) coated zirconium alloy cladding is considered as one of the most promising cladding materials for accident tolerant fuel (ATF). The degree of influence of the surface state of this material on the heat transfer performance will greatly affect the process optimization direction of coated zirconium cladding. In this paper, experiments are conducted on the Cr-coated zirconium alloy claddings prepared under atmospheric pressure in the pool boiling experimental device for Cr-coated zirconium alloy cladding. The influence law and mechanism of surface states such as roughness on heat transfer are studied. The results show that the improvement of surface roughness can reduce the conditions for the formation of vaporization core and significantly enhance heat transfer under the same wall superheat degree. Within the range of parameters studied in this paper, with the increase of heat transfer surface roughness, CHF shows an upward trend accordingly. Increasing the surface roughness can effectively improve the CHF value. On this basis, the prediction relational expression of the influence of roughness on heat transfer coefficient is also developed in this paper. -
表 1 实验段主要参数
Table 1. Main Parameters of Experimental Section
参数名 参数值 实验段总长/mm 260 实验段被加热段长度/mm 100 实验段外径/mm 9.52 实验段壁厚/mm 0.58 氧化铝陶瓷层外径/mm 8.36 氧化铝陶瓷层内径/mm 6 导热铜片外径/mm 6 导热铜片通孔直径/mm 1 铜排截面积/mm2 400 表 2 Cr涂层锆合金包壳粗糙度
Table 2. Roughness of Cr-coated Zirconium Alloy Cladding
样件号 平均粗糙度/μm B1 0.641 B2 0.443 B3 0.339 B4 0.355 表 3 直接测量参数不确定度
Table 3. Uncertainties of the Direct Measurement Parameters
测量参数 仪表精度 不确定度/% 温度 0.3℃ 0.27 电流 1.0 A 0.14 电压 0.015 V 0.12 表 4 间接测量参数不确定度
Table 4. Uncertainties of the Indirect Measurement Parameters
测量参数 不确定度/% 包壳传热面积 0.1 实验段功率 0.18 表面热流密度 0.21 传热系数 4.6 表 5 核态沸腾起始点的壁面过热度和热流密度
Table 5. Wall Superheat and Heat Flux at Onset of Nucleate Boiling (ONB)
样件号 壁面过热度/℃ 热流密度/(kW·m−2) B1 0.820 5.070 B2 1.642 6.594 B3 1.859 6.752 B4 1.582 6.534 表 6 Cr涂层锆合金包壳CHF值
Table 6. CHF Value of Cr-coated Zirconium Cladding
样件号 CHF/(kW·m−2) B1 914.722 B2 726.705 B3 647.189 B4 651.358 -
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