dpb wrote:
wrote:
... How many times do we have to squeeze a bellows to remove 5% of the air
from a window cavity, with a check valve and a vacuum breaker that allow
dry air to replace withdrawn air when the bellows is released, if we want
to lower the cavity dew point from 50 to 10 F?

... 31 times.
...
Didn't read the code but that's "simple" fix anybody is just going to
have the facilities to do just lying around--right!

The parts might cost $25.

At first blush it appears assumed totally dry air which wouldn't be likely

Air from a plastic box with a few desiccant bags would be close.

and doesn't account for mixing so that part of the introduced air
will be withdrawn as well as the initial on every cycle.

But it does. Read the code... a lot of 3rd graders used to speak BASIC :-)

10 P=.5*EXP(17.863-9621/(460+70))'initial cavity vapor pressure ("Hg)
20 W=.62198/(29.921/P-1)'initial humidity ratio (#w/#a)
30 PRINT P,W
40 P10=EXP(17.863-9621/(460+10))'vapor pressure at 10 F and 100% RH
50 W10=.62198/(29.921/P10-1)'10 F humidity ratio
60 W=.95*W'squeeze bellows
70 IF WW10 THEN N=N+1:GOTO 60
80 PRINT N,W,W10

..3741957 7.87707E-03

31 1.525878E-03 1.536647E-03

Nick