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高质量流速下立式螺旋管内汽液两相传热特性研究 总被引:2,自引:0,他引:2
对高质量流速下立式螺旋管内高压汽液两相流沸腾传热特性进行了试验研究,参数范围为:系统压力8.0~15.0MPa;质量流速2500~4000kg/m2s;壁面热流密度200~1000kW/m2;实验段为Φ14的不锈钢管弯制而成的螺旋管直径比为D/d=30.1的管圈,总长为2.335m,考察了热流密度和质量流速对两相传热的影响,分析核态沸腾和两相强制对流沸腾机理在螺旋管内两相传热中所起的作用,得到了局部传热系数的分布特性和平均传热系数计算关联式,首次发现高质量流速区域内螺旋管内汽液两相传热效果亦趋近于相同条件下直管内的换热系数,并对已有的结论进行了分类比较分析. 相似文献
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采用三维计算流体动力学(CFD)方法对聚变堆液态包层增殖区高温液态铅锂与结构内高压氦气耦合换热进行数值模拟。建立了充放式高压氦气回路和换热实验段,开展了包层典型工况下液态铅锂与氦气多流场耦合换热对比实验验证。研究了氦气压力和增殖区铅锂入口温度、核热功率密度变化时的流动与传热特性及其影响规律,获得了氦气与RAFM钢壁面、液态铅锂与RAFM钢壁面之间的换热系数和换热关联式,为液态包层的设计研发提供了参考依据。 相似文献
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局部热壁面多孔介质方腔内自然对流的数值研究 总被引:1,自引:0,他引:1
本文对上下壁面绝热、左侧壁面长度为b的嵌装加热器部分维持恒定温度T_h而剩余部分绝热,且右侧壁面维持恒定温度T_c的多孔介质方腔内的自然对流换热进行了数值研究.在热壁面无量纲长度B=0.5(B=b/L)的条件下,综合研究了左侧壁面受热部分中心距上壁面的无量纲长度D(D=d/L)、Da数、Ra数和孔隙率对腔体内自然对流换热的影响.数值计算结果表明,左侧壁面受热部分位置的不同对腔体内自然对流换热有很大的影响,D在0.6附近取值时,Na数最大.Da数、Ra数对腔体的自然对流换热影响较大,而孔隙率对换热的影响较小. 相似文献
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In this study, Marangoni flow and heat transfer enhancement in a heat pipe have been investigated. The experiments were carried out at different heat inputs. A constant temperature water bath was used at the condenser section at three temperature levels. Heat transfer coefficients and thermal resistances of the heat pipe were measured for pure water and water/butanol solutions. The experimental results confirmed that the heat pipe filled with butanol solutions showed better thermal performance than the water-filled heat pipe. At maximum heat flux, 25% heat transfer improvement was obtained when 7 wt% butanol solution was used instead of pure water. 相似文献
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以水为介质,建立了液体流动的混合物多相流模型及空化模型,运用CFD方法对水平圆管内伴随有水力空化现象的受迫对流换热过程进行了数值研究,详细分析了管道入口压力、入口温度和限流孔与管道直径比等因素对水力空化及对流换热过程的影响规律。数值模拟结果表明,空化现象出现在圆管喉部(限流孔)壁面附近区域;与相同流量下无空化时的传热相比,在发生空化现象的区域,传热壁面被蒸汽所覆盖导致传热急剧恶化,而在远离空化发生区域的下游位置,由于空化的扰流作用使得加热壁面与流体之间的传热得到明显改善。 相似文献
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The natural gas hydrate plugging problems in the mixed pipeline are becoming more and more serious. The hydrate plugging has gradually become an important problem to ensure the safety of pipeline operation. The deposition and heat transfer characteristics of natural gas hydrate particles in the spiral flow pipeline have been studied. The DPM model (discrete phase model) was used to simulate the motion of solid particles, which was used to simulate the complex spiral flow characteristics of hydrate in the pipeline with a long twisted band. The deposition and heat transfer characteristics of gas hydrate particles in the spiral flow pipeline were studied. The velocity distribution, pressure drop distribution, heat transfer characteristics, and particle settling characteristics in the pipeline were investigated. The numerical results showed that compared with the straight flow without a long twisted band, two obvious eddies are formed in the flow field with a long twisted band, and the velocities are maximum at the center of the vortices. Along the direction of the pipeline, the two vortices move toward the pipe wall from near the twisted band, which can effectively carry the hydrate particles deposited on the wall. With the same Reynolds number, the twisted rate was greater, the spiral strength was weaker, the tangential velocity was smaller, and the pressure drop was smaller. Therefore, the pressure loss can be reduced as much as possible with effect of the spiral flow. In a straight light flow, the Nusselt number is in a parabolic shape with the opening downwards. At the center of the pipe, the Nusselt number gradually decreased toward the pipe wall at the maximum, and at the near wall, the attenuation gradient of the Nu number was large. For spiral flow, the curve presented by the Nusselt number was a trough at the center of the pipe and a peak at 1/2 of the pipe diameter. With the reduction of twist rate, the Nusselt number becomes larger. Therefore, the spiral flow can make the temperature distribution more even and prevent the large temperature difference, resulting in the mass formation of hydrate particles in the pipeline wall. Spiral flow has a good carrying effect. Under the same condition, the spiral flow carried hydrate particles at a distance about 3–4 times farther than that of the straight flow. 相似文献
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在 HL-2M 第一壁传热结构设计中,利用导热管的轴向快速导热特性及较短的传热路径,将面对等离
子体的第一壁表面热量快速传至真空室内壁上。第一壁背板和真空室内壁上分别焊接导热铜块作为冷热连接端,
导热管嵌入其内,导热管与铜块之间增垫导热金属箔并用压板固定压紧,以增强接触界面传热。根据此传热结构
设计,设计加工了相应的传热性能测试试验件。通过对试验件进行传热性能测试及实验条件外推可知,试验件冷
热端面间的最大传热功率为 4kW,端面间最大对流换热系数为 6kW·m‒2。 相似文献