Metal contraction in freezer 2

[Bob1uk]

I have two questions if I may
1-If an aluminum housing with a steel spool valve is placed in a freezer is it likely to be covered in frost on removal after several hours ?
2- Depending on the answer to (1) would this be a valid test for hanging spool valve when ambient temperature is cold?

Thanking you in anticipation

Bob Ryan

 

[hydtools]

The appearance of frost would not indicate spool hanging. That indicates humidity in the air condensing and freezing on the housing and that the housing temperature is at or below freezing temp of water. Not being able to move the spool would be an indication that the spool is stuck. The aluminum housing will shrink more than the steel spool as the temperature is lowered. If there is not enough spool clearance to allow the spool to remain smaller than the cold aluminum bore, the spool will hang or stick.

Ted

 

[Bob1uk]

Thank you Ted, you have confirmed my thoughts.
One more question if I may. Would placing the housing in the freezer while it is still warm encourage a coating of frost? I notice some aluminum housings do get covered in a light coating of frost while others do not.

 

[BrianPetersen]

Frost will get on the surface when you take it out of the cold area and expose it to normal ambient temperature and humidity. (The cold surfaces are freezing moisture out of the air. In order for that to happen, the object needs to be below freezing and the air needs to have some moisture in it - normal ambient-conditions will have more than enough).

The other mechanism for frost formation is having the object sitting outside in near-freezing temperatures but exposed to the night sky under clear conditions. Thermal radiation from the surface causes it to to below freezing and draw moisture out of the air and freeze it. Same thing can happen in the freezer if the conditions are right.