## 3 Helix-Cyclone in Situ Separator Experimental System Construction
### Main Unit Components of the Experimental System
#### 3.1.2 Data Monitoring Module  
Data detection units mainly include electromagnetic flowmeters, pressure sensors, and a paperless recorder. As shown in Figure 4a, the electromagnetic flowmeter is an intelligent display type manufactured by Hangzhou Meikong Automation Technology Co., Ltd., Hangzhou, China. with a flange installation method. The electromagnetic flowmeter can output a 4-20 mA signal, and the electromagnetic flowmeter output data can be directly transmitted to the paperless recorder.  
Figure 4: Physical diagrams of the electromagnetic flowmeter, pressure sensor, and paperless recorder.  
Figure 3: Experimental system schematic and fluid circulation system site photo.  
The pressure transmitter, shown in Figure 4b, is also from Hangzhou Meikong Automation Technology Co., Ltd., Hangzhou, China. with the pressure data collection points on the separator pre-machined with threads for the direct connection of the pressure sensors at the inlet and outlet of the separator to measure real-time pressure inside the separator. The paperless recorder, as shown in Figure 4c, is the HR1000 series from Beijing Huake Yi Technology Co., Ltd., Beijing, China. used to record pressure and flow parameters during the experiment. The signals collected by the recorder are processed using the DMR post-processing software. The DMR 3.12.0 software works by processing input data that typically include high-frequency measurements of system parameters. The input data are analyzed using advanced signal processing algorithms and machine learning models to identify patterns, trends, or anomalies. The output data include processed results, such as predictions, diagnostic insights, or optimized parameters, which support decision-making processes.  
Due to the special conditions of hydrate formation, it is difficult to carry out direct experiments with mixed slurries of natural gas hydrates under real conditions, considering that the working principle of the separator is to separate media of different densities by the generated centrifugal force. Based on this, pellets of different sizes made of polyethylene material, which has a density similar to that of the hydrate's solid-phase particles, were selected in this study as a substitute for the hydrate's solid particles. Quartz sand powder with a density of 2650 kg/m\({}^{3}\) was used to replace the sand in the hydrate slurry, and this replacement sample was stable and well dispersed at room temperature. Salted tap water was used as a replacement for seawater, which was then mixed with polyethylene pellets to simulate hydrate particles. Based on the analysis of sediment samples from natural gas hydrate drilling in the South China Sea, the sediment is mainly composed of powdered sand (4-63 \(\upmu\)m), a small amount of clay (4 \(\upmu\)m), and fine sand (63-250 \(\upmu\)m) [18; 19]. Therefore, quartz sand (with a particle size of 74 \(\upmu\)m), whose particle size is similar to that of the mud/sand in the real gas hydrate reservoir, was selected and mixed with water, the mass of solid-phase dry sand weighed was set to be \(m_{\mathrm{s}}\), and the mass of water was set to be \(m_{\mathrm{w}}\), so that the concentration of mud/sand in the mixed slurry is as follows.  
\[C=\frac{m_{\mathrm{s}}}{m_{\mathrm{w}}+m_{\mathrm{s}}} \tag{1}\]