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Modeling Chilled-Water Storage System Components for Coupling to a Small Modular Reactor in a Nuclear Hybrid Energy System

机译：耦合到核混合能源系统中耦合至小型模块化反应堆的冷冻水存储系统组件的建模

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摘要

The intermittency of wind and solar power puts strain on electric grids, often forcing carbonbased and nuclear sources of energy to operate in a load-follow mode. Operating nuclear reactors in a load-follow fashion is undesirable due to the associated thermal and mechanical stresses placed on the fuel and other reactor components. Various Thermal Energy Storage (TES) elements and ancillary energy applications can be coupled to nuclear (or renewable) power sources to help absorb grid instabilities caused by daily electric demand changes and renewable intermittency, thereby forming the basis of a candidate Nuclear Hybrid Energy System (NHES).;During the warmer months of the year in many parts of the country, facility air-conditioning loads are significant contributors to the increase in the daily peak electric demand. Previous research demonstrated that a stratified chilled-water storage tank can displace peak cooling loads to off-peak hours. Based on these findings, the objective of this work is to evaluate the prospect of using a stratified chilled-water storage tank as a potential TES reservoir for a nuclear reactor in a NHES. This is accomplished by developing time-dependent models of chilled-water system components, including absorption chillers, cooling towers, a storage tank, and facility cooling loads appropriate for a large office space or college campus, as a callable FORTRAN subroutine. The resulting TES model is coupled to a high-fidelity mPower-sized Small Modular Reactor (SMR) Simulator, with the goal of utilizing excess reactor capacity to operate several sizable chillers in order to keep reactor power constant.;Chilled-water production via single effect, lithium bromide (LiBr) absorption chillers is primarily examined in this study, although the use of electric chillers is briefly explored. Absorption chillers use hot water or low-pressure steam to drive an absorption-refrigeration cycle. The mathematical framework for a high-fidelity dynamic absorption chiller model is presented. The transient FORTRAN model is grounded on time-dependent mass, species, and energy conservation equations. Due to the vast computational costs of the high-fidelity model, a low-fidelity absorption chiller model is formulated and calibrated to mimic the behavior of the high-fidelity model.;Stratified chilled-water storage tank performance is characterized using Computational Fluid Dynamics (CFD). The geometry employed in the CFD model represents a 5-million-gallon storage tank currently in use at a North Carolina college campus. Simulation results reveal the laminar numerical model most closely aligns with actual tank charging and discharging data. A subsequent parametric study corroborates storage tank behavior documented throughout literature and industry.;Two absorption chiller configurations are considered. The first involves bypassing lowpressure steam from the low-pressure turbine to absorption chillers during periods of excess reactor capacity in order to keep reactor power constant. Simulation results show steam conditions downstream of the turbine control valves are a strong function of turbine load, and absorption chiller performance is hindered by reduced turbine impulse pressures at reduced turbine demands.;A more suitable configuration entails integrating the absorption chillers into a flash vessel system that is thermally coupled to a sensible heat storage system. The sensible heat storage system is able to maintain reactor thermal output constant at 100% and match turbine output with several different electric demand profiles. High-pressure condensate in the sensible heat storage system is dropped across a let-down orifice and flashed in an ideal separator. Generated steam is sent to a bank of absorption chillers. Simulation results show enough steam is available during periods of reduced turbine demand to power four large absorption chillers to charge a 5-million-gallon stratified chilled-water storage tank, which is used to offset cooling loads in an adjacent facility. The coupled TES systems operating in conjunction with an SMR comprise the foundation of a tightly coupled NHES.
机译：风能和太阳能的间歇性给电网带来压力，通常迫使碳基和核能能源以负荷跟随模式运行。由于负载在燃料和其他反应堆部件上的相关热应力和机械应力，不希望以负荷跟随方式运行核反应堆。各种热能存储（TES）元素和辅助能源应用可以与核能（或可再生能源）耦合使用，以帮助吸收因每日电力需求变化和可再生间歇性而导致的电网不稳定，从而构成候选核混合能源系统的基础（ NHES）；；在该国许多地方，一年中的暖月期间，设施空调负荷是每日峰值用电需求增加的重要因素。先前的研究表明，分层的冷冻水储罐可以将高峰制冷负荷转移到非高峰时间。基于这些发现，这项工作的目的是评估使用分层冷冻水储罐作为NHES中核反应堆的潜在TES储罐的前景。这是通过开发与时间相关的冷冻水系统组件的模型来完成的，这些模型包括可吸收的冷却器，冷却塔，储水箱以及适用于大型办公空间或大学校园的设施冷却负荷，作为可调用的FORTRAN子例程。生成的TES模型耦合到高保真mPower尺寸的小型模块化反应堆（SMR）模拟器，其目的是利用多余的反应堆容量来运行多个大型冷水机组，以保持反应堆功率恒定。因此，本研究主要研究了溴化锂（LiBr）吸收式制冷机，尽管简要探讨了电制冷机的使用。吸收式制冷机使用热水或低压蒸汽来驱动吸收-制冷循环。提出了高保真动态吸收式制冷机模型的数学框架。瞬态FORTRAN模型基于与时间相关的质量，种类和能量守恒方程。由于高保真模型的巨大计算成本，因此制定了低保真吸收式冷却器模型并进行了校准以模仿高保真模型的行为。;使用计算流体力学（ CFD）。 CFD模型中采用的几何形状代表了北卡罗来纳州大学校园目前使用的500万加仑的储罐。仿真结果表明，层流数值模型与实际的储罐充放电数据最接近。随后的参数研究证实了整个文献和行业中记录的储罐性能。考虑了两种吸收式制冷机配置。第一种方法是在反应堆容量过大期间将低压蒸汽从低压涡轮机旁路到吸收式冷却器，以保持反应堆功率恒定。仿真结果表明，涡轮控制阀下游的蒸汽条件是涡轮负载的重要函数，并且在降低涡轮需求的情况下，通过降低涡轮脉冲压力会阻碍吸收式制冷机的性能。更合适的配置需要将吸收式制冷机集成到闪蒸容器系统中它与显热存储系统热耦合。显热存储系统能够将反应堆热输出保持恒定在100％，并使涡轮输出与几种不同的电力需求曲线相匹配。显热存储系统中的高压冷凝水通过放气孔滴落，并在理想的分离器中闪蒸。产生的蒸汽被送到吸收式冷却器组。仿真结果表明，在涡轮机需求减少期间，有足够的蒸汽可用于为四个大型吸收式制冷机提供动力，以向一个500万加仑的分层冷水储罐供能，该储罐用于抵消相邻设施中的冷却负荷。与SMR结合使用的耦合TES系统构成了紧密耦合的NHES的基础。

著录项

  • 作者

    Misenheimer, Corey Thomas.;

  • 作者单位

    North Carolina State University.;

  • 授予单位 North Carolina State University.;
  • 学科 Mechanical engineering.;Nuclear engineering.;Energy.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 224 p.
  • 总页数 224
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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