| 摘要 |
A freeze drying method includes decreasing pressure to a first vacuum pressure and, as a result of reaching the first pressure, a control system automatically activating a heater. The method includes sublimating solid water, increasing pressure to a second vacuum pressure greater than the first pressure, and, as a result of reaching the second pressure, the control system automatically deactivating the heater. As a result, a decrease in pressure, pressure-activated heater activation, material heating, water sublimation, and increase in pressure occur, accomplishing pressure-activated heater cycling. Another freeze drying method includes decreasing a temperature in a chamber to −50° F. or less using a refrigeration system with single-stage compression and sublimating solid water at a vacuum pressure. A freeze drying apparatus includes a chamber, a vacuum pump, a heater, and a control system programmed with instructions operable to accomplish pressure-activated heater cycling. |
| 主权项 |
1. A freeze drying method comprising:
decreasing pressure in a chamber to a first vacuum pressure, the chamber containing a material containing solid water; as a result of reaching the first vacuum pressure, a control system automatically activating a heater and heating the material without melting the solid water; sublimating the solid water to gaseous water and increasing pressure to a second vacuum pressure greater than the first vacuum pressure; cooling an interior surface of the chamber to below the material temperature; condensing and freezing at least a portion of the gaseous water on the interior surface of the chamber; and as a result of reaching the second vacuum pressure, the control system automatically deactivating the heater and, as a result, repeating a decrease in pressure to the first vacuum pressure, pressure-activated heater activation as a result of reaching the first vacuum pressure, material heating, water sublimation, and increase in pressure to the second vacuum pressure and accomplishing pressure-activated heater cycling. |
