Experimental investigation of CO2 thermosyphon flow and heat transfer in the supercritical region
Experimental investigation of CO2 thermosyphon flow and heat transfer in the supercritical region
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DOI：
10.1016/j.ijheatmasstransfer.2013.03.077
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发表时间：
2013-09
影响因子：
5.2
通讯作者：
Lin Chen;Bili Deng;Xin‐Rong Zhang
中科院分区：
文献类型：
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作者：
Lin Chen;Bili Deng;Xin‐Rong Zhang
由于近临界流体的独特性质，跨临界/超临界CO2自然循环回路（NCL，Thermosyphon）已被广泛应用于太阳能热水器、余热回收、新一代核冷却等能源转换系统中。封闭式热虹吸管是专为高压实验而设计的，其中自然对流仅通过加热和冷却回路中的流体来实现。该系统在近临界区域的压力范围从约6.0至15.0 MPa的宽范围内操作。研究发现，随着系统初始压力的增加，NCL流动将从不稳定的亚临界两相流动转变为稳定的液相流动，然后转变为稳定的超临界循环。分析了稳定流动条件下，主要是超临界区的传热特性。本文介绍了流体温度、质量流量和回路压力的一般变化。在稳定的超临界区域，冷却器的传热性能表现出很小的变化与散装平均流体温度，并在加热器更好的传热被发现的条件接近伪临界点。本文还详细讨论了操作压力对传热的影响及其演变机理。
Due to the unique properties of near-critical fluid, trans-critical/supercritical CO2based natural circulation loop (NCL, or thermosyphon) has been proposed in many energy conversion systems, such as solar heater, waste heat recovery, next generation nuclear cooling, etc. This paper presents an experimental investigation of a near-critical CO2thermosyphon. The closed thermosyphon is specially designed for high pressure experiments, where natural convection is achieved only by heating and cooling of fluid in the loop. The system is operated in wide range of pressures from around 6.0 to 15.0 MPa in the near-critical region. It is found that the NCL flow will change from unstable sub-critical two-phase flow to stable liquid flow, and then become stable supercritical circulation with the increase of system initial pressure. The heat transfer behaviors are analyzed for stable flow conditions mainly for supercritical region. General variations of the fluid temperature, mass flow rate and loop pressure are presented in this paper. In the steady supercritical region, the heat transfer performance of the cooler show very small changes with bulk mean fluid temperature, and at the heater better heat transfer is found for conditions close to the pseudo-critical point. The heat transfer dependency on operation pressure and evolution mechanisms are also discussed in detail in this paper.