Mapping the operation of the DMT Continuous Flow CCN counter
Mapping the operation of the DMT Continuous Flow CCN counter
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DOI：
10.1080/02786820500543290
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发表时间：
2006-04-01
影响因子：
5.2
通讯作者：
Nenes, A
中科院分区：
文献类型：
--
作者：
Lance, S;Medina, J;Nenes, A
本文详细分析了一种测量云凝结核的新型商用仪器--液滴测量技术圆柱形连续流向热梯度云凝结核室（CFSTGC）。该仪器可以在0.06%至3%（可能高达6%）的过饱和度下测量CCN浓度，采样率为1 Hz，足以进行机载操作。我们的分析采用了一个完全耦合的数值流动模型来模拟CFSTGC在其整个操作范围内（气溶胶样品流速0.25-2.0 Lmin（-1），温差2-15 K和环境压力100-1000 mb）的水蒸气过饱和度，温度，速度分布和CCN生长。该模型进行了评估，通过比较模拟仪器响应校准气溶胶对实际测量从现有的CCN仪器。该模型被用来评估CCN的检测效率的大范围的环境压力，流速，温度梯度和液滴生长动力学。模拟高估了仪器过饱和时，不考虑跨流动室的壁的热阻。我们已经开发出一种方法来确定的热阻和温度下降的湿壁的流动室，通过结合模拟和校准实验。最后，我们提供了确定热阻，仪器过饱和度和光学粒子计数器的最佳检测阈值的参数。
This work thoroughly analyzes a new commercial instrument for measuring Cloud Condensation Nuclei (CCN), the Droplet Measurement Technologies Cylindrical Continuous- Flow Streamwise Thermal Gradient CCN Chamber (CFSTGC). This instrument can measure CCN concentrations at supersaturations from 0.06% to 3% (potentially up to 6%), at a 1 Hz sampling rate that is sufficient for airborne operation. Our analysis employs a fully coupled numerical flow model to simulate the water vapor supersaturation, temperature, velocity profiles and CCN growth in the CFSTGC for its entire range of operation (aerosol sample flow rates 0.25-2.0 Lmin(-1), temperature differences 2-15 K and ambient pressures 100-1000 mb). The model was evaluated by comparing simulated instrument responses for calibration aerosol against actual measurements from an existing CCN instrument. The model was used to evaluate the CCN detection efficiency for a wide range of ambient pressures, flow rates, temperature gradients, and droplet growth kinetics. Simulations overestimate the instrument supersaturation when the thermal resistance across the walls of the flow chamber is not considered. We have developed a methodology to determine the thermal resistance and temperature drop across the wetted walls of the flow chamber, by combining simulations and calibration experiments. Finally, we provide parameterizations for determining the thermal resistance, the instrument supersaturation and the optimal detection threshold for the optical particle counter.