ambiant temperature and condensation

[fatshlink]

I keep reading that condensation occures anytime you get below ambiant temperature. this isent true. their wont be condensation until dewpoint which will very near freezing. my minifrige has a freezing trey, and the rest of it doesent condensate. you could easly put a res inside my frige and not have the rest of it condensate. why do people keep telling other people that condensation occures under ambiant???

[Tiger]

The impression one gets from many of the posts is that dewpoint is some fixed temperature depending on who is saying it and I have seen temps ranging from 13C to freezing.
Well the truth is that its a moving target as dewpoint is actually dependent on the relative humidity of the air. So when there are high humidity levels, and particularly when it is around the 100% level, dewpoint can be at ambient because the air is saturated. With declining levels dewpoint temps will be lower.
Go to http://www.unc.edu/depts/cmse/nature/dewpoint.html for more info.
If you want to find out what temp dewpoint is for your area in the US is on any given day go here http://205.156.54.206/tdl/lamp/analysis_pages/DWPF.shtml
The reason why you won't see much condensation in your refrigerator is because most of the water has condensed out already. The air in fridges is quite dry for this reason. You will also notice that in areas with high humidity that the freezer tends to ice-up quicker.
Hope this clarifies this subject.
There was another post recently regarding the same issue and I made the suggestion that perhaps keeping the air warm around the waterblock would reduce the risk of condensation. I said this because warm air holds more water. I was flamed for the suggestion so made no further comment.

[ButcherUK]

The problem with the warm air around the waterblock is when it contacts the cool surface it cools down and condensation forms - thus dumping more water than if the air was cool.

As for fridges, they do get condensation but most fridges and freezers have what's known as auto-defrost, basically the condensed water is collected in a tray and evaporated off by the heat of the condenser on the back of the fridge (least I think that's how it works), net result is very dry air.

[Tiger]

Originally posted by ButcherUK
The problem with the warm air around the waterblock is when it contacts the cool surface it cools down and condensation forms - thus dumping more water than if the air was cool.
Not if (a) the air is moving because it doesn't have time to cool ( remember air is a poor conductor) and (b) the surface is lagged to prevent direct contact.
Ideally the w/b surface should be lagged to enhance the cooling.