Abstract Natural gas hydrate sampling technology is an important means to study in situ properties. Currently, there are certain limitations in the application of pressure preservation technology, such as poor sealing and low success rates. Hole-bottom freezing sampling technology has the advantages of a simple structure, large sample size, and high fidelity. To solve the problem of low freezing efficiency, the quality of the cold source was controlled by changing the specific surface area of dry ice, ambient pressure, and temperature difference. The experimental results show that the improvement of heat transfer efficiency by the specific surface area and the temperature difference is mainly reflected in the cold source injection process. At the same time, it changes the viscosity of the cold source to make it easier to adhere, which will cause a large amount of dry ice loss and reduce freezing efficiency. The increase in ambient pressure will inhibit the sublimation of dry ice, reduce the heat transfer rate of phase change, and affect the freezing efficiency. Meanwhile, a solid layer will be formed and the cold source cannot be injected. According to the results, granular dry ice was selected to prepare a cold source with a temperature difference of 105K and ambient pressure of 0.1 MPa.

中文翻译：

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天然气水合物取样孔底冻结技术冻结效率优化——影响干冰相变因素的研究

摘要 天然气水合物取样技术是研究原位性质的重要手段。目前，保压技术的应用存在一定的局限性，如密封性差、成功率低等。孔底冷冻采样技术具有结构简单、样本量大、保真度高等优点。为解决冷冻效率低的问题，通过改变干冰的比表面积、环境压力和温差来控制冷源质量。实验结果表明，比表面积和温差对传热效率的提高主要体现在冷源注入过程中。同时，它改变了冷源的粘度，使其更容易粘附，这会造成大量干冰损失，降低冷冻效率。环境压力的增加会抑制干冰的升华，降低相变传热率，影响冷冻效率。同时会形成固体层，无法注入冷源。根据研究结果，选用粒状干冰制备温差为105K、环境压力为0.1 MPa的冷源。