| 摘要: |
| 控制预冻阶段的过冷度对冷冻干燥制品品质的均一性以及后期干燥速率有着重要影响。实验和理论研究了主动降压诱发过冷水成核过程中降压速率、预冷温度和终压等因素对小瓶内水结冰现象的影响。研究发现：常压下解除过冷度范围为9～17 ℃，而在降压过程中解除过冷度范围为8～11 ℃；在5～20 kPa/s范围内降压速率对成核影响不大；在100～400 Pa区间内终压越低，检测到的解除过冷度越低。计算分析表明，降压过程中水体表面及附近区域达到的最低温度可能是影响成核的关键因素。 |
| 关键词: 冷冻干燥 预冻 成核 降压 过冷水 |
| DOI： |
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| 基金项目:浙江省文物局文物保护科技项目(2013007)资助。 |
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| Theoretical and Experimental Study on the Effects of Depressurization Process on the Ice Nucleation of Supercooled Water |
|
Huang Gensheng, Chen Guangming, Zhang Shaozhi, Jiang Qing
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| (Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province, Refrigeration and Cryogenic Engineering Institute, Zhejiang University) |
| Abstract: |
| The control of ice nucleation temperature during the freezing stage has significant influences on quality uniformity of freeze-dried products and drying rate of later stages. For active depressurization to induce ice nucleation of supercooled water in vials, the effects of depressurization rate, final pressure level and supercooling degree on the nucleation phenomenon were studied experimentally and theoretically here. The following results were obtained: under atmospheric pressure the range of releasing supercooling degree(RSD) was 9-17 ℃,while during depressurization the range of RSD became 8-11 ℃; in the range of 5-20 kPa/s the depressurization rate had little effect on the nucleation of supercooled water; in the range of 100-400 Pa, lower final pressure led to lower RSD. Through numerical calculation and analysis it was indicated that the lowest temperature of surface water during depressurization maybe the key factor influencing ice nucleation. |
| Key words: freeze drying pre-freezing nucleation depressurization supercooled water |
