Freeze Drying Hints updated 3/1/2005

1. Tubes collect frost on the outside. This causes inaccuracies in the measurement and in the heat transfer analysis. Wipe down the outside, but try not to affect the temperature.
2. Is it heat transfer limited or mass transfer limited? Convince yourself of this by adding insulation to a few experiments. You can get bubble wrap from Mike Beliveau.
3. Do not put too much liquid into the tubes. You want a thin film.
4. The surface area changes, especially near the end of each experiment. You need to estimate the surface area and cmoe up with a model to describe changes in surface area.
5. The knobs are 3-way valves. Do not turn past the stop.
6. There is a bottle to bottle variation in weight.
7. The bottles are specially ordered to match the experiment, and cost about $30 each. Please be careful not to break these bottles.
8. You can review how dissolved solids change properties by looking in your P-Chem book.
9. Be careful taking the bottle on and off of the experiment. Hold the top of the vials when taking them on or off. Put them at an angle for best results.
10. A lower vacuum pressure can be obtained by pushing back on the valves where you connect the tubes.
11. For best freezing results, make sure that the belt chambe is level. The freezer top is not level with the belt.
12. Do not put too many vials in the shell freezer.
13. Keep the vials clean.
14. Don’t tighten the bottom bolt on the freeze dryer manifold. It will give a better seal with just the top bolt tightened.