TBAB包络化合物浆潜热输送的固液两相流流动与传热模拟
文献类型：学位论文
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| 作者 | 宋文吉 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-27 |
| 授予单位 | 中国科学院广州能源研究所 |
| 授予地点 | 广州能源研究所 |
| 导师 | 冯自平 |
| 关键词 | TBAB CHS 潜热输送 固-液两相流模拟 流动 对流传热 |
| 其他题名 | Solid-liquid Two-phase Flow Simulation of TBAB Clathrate Hydrate Slurry using for Latent Heat Transportation |
| 中文摘要 | The Tetra-n-Butyl-Ammonium Bromide (TBAB) Clathrate Hydrate Slurry (CHS) is one of promising media for latent heat transportation.It can be used as substitute secondary coolant in centralized air-conditioning systems and district cooling systems. Because CHS releases its latent heat during phase change at atmosphere pressure in the temperature range of 5~12℃, it can carry more cold energy per unit. Based on that, CHS latent heat transportation could cut energy consumption of pumps because of downsizing pipeline diameters, and then realize the aim of energy saving. There are six main parts in this paper. Firstly, the related references about the latent heat transportation applications of TBAB CHS were summarized and analyzed comprehensively. And it shows that the fundamental researches about momentum transfer and heat transfer mechanism are still not exhaustive. One theoretical model for CHS flow and heat transfer, from the aspect of solid-liquid two-phase flow, will be significant supplement. Secondly, based on above, one 3-D theoretical model for CHS flow in horizontal pipe was established, which could give better expression to the solid-liquid two-phase flow characteristics. In the model, the effect gravity forced on solid particles was included, and slip velocity between particles and liquid was used to describe interphase forces. Solid viscosity expression made control equations complete. Turbulent flow was based on RNG k-ε model, and two different expressions were used for laminar sublayer and vigorous turbulent region separately. One simplified 2-D theoretical model for CHS convective heat transfer with constant heat flux in horizontal pipe was established. Mass transfer and heat transfer between solid and liquid phase were coupled with source items in continuity equations and energy equation. Source enhancement and field coordination theory, deduced from energy equation, could give better explanation to heat transfer enhancement phenomenon for TBAB CHS. Then, in order to verify our numerical calculation, one experiment stand was set up, and pressure drop and mean convective heat transfer characteristics of CHS in pipe flow were investigated experimentally. Comparison between experimental and numerical results in the range of χ<30%, show that 3-D model for CHS flow behaviors and 2-D model for CHS convective heat transfer characteristics present good agreement within a maximum error equal to ±12%. After that, the flow behaviors of CHS were analyzed in detailed from the aspect of solid-liquid two-phase flow. The velocity profile shows a flow pattern transform tendency from shear flow to plug flow with the increasing of solid fraction in laminar flow region, which can owe to its non-Newtonian as single phase fluid. The solid concentration distribution profiles indicate that obvious stratified flow appears in sublayer at laminar flow region, and it disappears when flow velocity increases. Based on the results of orthogonal analysis, mean flow velocity is the most important factor for flow resistant of CHS, solid fraction is the second and pipe diameter is the last. In the range of CHS particle size distribution, particle diameters show little effects on pressure drop of CHS pipe flow, and it can be neglected. Meanwhile, the convective heat transfer characteristics of CHS pipe flow were discussed comprehensively. Contrast to TBAB aqueous solution (χ=0), CHS could enhance heat transfer up to 1.5~3.5 times. The section temperature profiles express thermal transfer process from tube wall to fluids. In laminar region, conductivity is the main way for thermal transfer, and the releasing of latent heat of CHS particles increases temperature difference along radial direction. In turbulent region, turbulent kinetic enhances heat transfer in core flow region and its thermal resistant concentrates in sublays, and the releasing of latent heat decreases wall temperature. Along axis direction, there exist three regions—non-melting region, melting region and melted region, and boundaries among them were obtained. Among parametric variations effecting CHS convective heat transfer, the mean flow velocity is the most crucial factor, solid fraction and latent heat value are second class, and heat flux shows little effect on heat transfer coefficient. In the range of CHS particle size distribution, particle diameters show a bit better effect in turbulent region than that in laminar region. Lastly, two main applications in latent heat transportation were introduced by use of the established solid-liquid two-phase model. Critical deposition velocities, which stand for transformation from moving bed flow to heterogeneous flow, were obtained for type A and type B CHS separately. These could ensure the safe transportation for CHS. Another application is optimizing pump power consumption by adjusting solid fraction in CHS and flow velocity. For type B CHS, contrast to cold water, there exists an optimum solid fraction range (around χ=26%), in which the power consumption for transportation could be minimum. |
| 语种 | 中文 |
| 公开日期 | 2011-07-14 ; 2011-07-15 |
| 页码 | 113 |
| 源URL | [http://ir.giec.ac.cn/handle/344007/5830]  |
| 专题 | 中国科学院广州能源研究所 |
| 推荐引用方式 GB/T 7714 | 宋文吉. TBAB包络化合物浆潜热输送的固液两相流流动与传热模拟, Solid-liquid Two-phase Flow Simulation of TBAB Clathrate Hydrate Slurry using for Latent Heat Transportation[D]. 广州能源研究所. 中国科学院广州能源研究所. 2009. |
入库方式： OAI收割
来源：广州能源研究所
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