Effect of Shape of Operating Chamber in the Freeze-drying Process

A RECENT communication1 discusses the freeze-drying process as conducted with the pressure of permanent gas, and the vapour pressure of the ice on the condenser, maintained at very low levels. Research on the application of the process to foodstuffs is being conducted at the Low Temperature Research Station, Cambridge. It seemed likely that the need to operate at extremely low pressures might be undesirable economically in such applications, and accordingly other factors which affect the efficiency of the process have been investigated, including air pressures up to 1 mm. mercury and condenser temperatures of â20° C. and higher. The results show, as will be made clear below, that the design of the space in which freeze-drying is proceeding materially affects efficiency.