Hi Todd, The RH goes up as air cools, but past a certain point (past freezing) the humidity in the air begins to crystallize out and the air becomes drier. This is the principle that is used in freeze drying... when the temp continues to be very cold, the air becomes so dry that frozen moisture sublimates out of the objects in the freezer, transitioning into vapour without melting first. Science is so 'cool'! (Sorry, couldn't resist), Linda R
On Wed, Dec 19, 2018, 2:34 PM Todd Holmberg <[email protected] wrote: > Hello All- > > Just a follow up to confirm- we placed the sensor in a test box with > objects, and the results were much better like you suggested. The defrost > cycle spikes were greatly minimized. > > I do have another question though that I wonder if any of you might be > able to chime in on. I still have moments when I can't seem to wrap my > brain around Temp/RH- It's interesting to see these charts from the > freezer. I am used to seeing an inverse relationship between Temp and > RH%. As air warms, it can hold more moisture, so the RH% goes down, and as > air cools it can hold less moisture so the RH% grows larger. In these > charts though, it looks like as the air warms during the spikes, the RH % > rises up along with it... Does anyone have any thoughts on this?- Does > Temp/RH in a freezing environment have a different set of rules? I will be > looking around in the meantime to see if I can find sources to better > understand this. Most of the sites/resources that I've found > discussing Temp/RH relationships use language and visuals that are hard for > me to really fully grasp. That's obviously not the fault of the site, they > are just speaking the facts, it's my brain that is having the trouble. > Given the nature of my job though, it is something though that I wish I had > a better handle on to better answer questions that I am occasionally asked. > > During the defrost cycle when the temp rises, can anyone tell me why the > RH% also rises (shouldn't it go down as the air warms)? > > FYI- it can be a little hard to understand the chart depending on your > computer monitor. The line showing RH% is blue corresponding to the right > vertical axis, and the temp line is black according to the left vertical > axis. > > Thanks, > Todd > > On Thu, Dec 13, 2018 at 12:25 PM [email protected] <[email protected]> > wrote: > >> Hello, All >> >> Agreeing with what has been mentioned. Our freezer experience is the same >> as others are mentioning. We set our temp to -35, and find that there are >> consistent temperature spikes in ambient air, but only above -22 for short >> periods of time (~20min). >> >> We also add 1 or 2 additional loggers into items we freeze (in a >> furniture drawer, in the center of a textile tube, in the pocket of a >> garment bag, inside a box with a frame) and our experience is the same as >> Alans: the temperature changes are significantly less when buffered inside >> of something - there was no cause for concern with the temperature spikes. >> >> Julie >> >> >> >> On Wednesday, December 12, 2018 at 2:22:45 PM UTC-8, Todd Holmberg wrote: >>> >>> Hello Pestlist, >>> >>> I have a question related to freezing treatment temperatures. >>> >>> At the museum I work at, we recently put a data logger in our freezer. >>> We took the readout this morning, and now have our first chart showing the >>> temperature conditions inside over the course of a full 7-day week. >>> Something came up on the readout that I wanted to run past this group and >>> see if anyone had any opinions on it. >>> >>> The "base/normal" temp in the freezer is -28 F, and it holds that pretty >>> steady. There were 8 temp spikes though. The doors remained shut the >>> entire week, and my guess is the spikes are related to a defrost cycle. >>> The spikes were all virtually identical and lasted 55 minutes. The temp >>> went from -28 to -14, then back to -28, with about 20-25 minutes of temps >>> warmer than -22 (I have heard -22 F is a significant temp relating >>> to freezing effectiveness- is that true?). >>> >>> Does anyone have an opinion on whether or not spikes where >>> the temp rises between -22 F and -14 F for 20-25 minutes would have a >>> significant affect on a freezing treatment? My guess is there will be >>> approx. 10 of these spikes per week, but we will see about that as >>> more weekly charts come in. >>> >>> If anyone has an opinion or thoughts they would be appreciated. >>> >>> Thanks, >>> Todd >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "Museumpests" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To post to this group, send email to [email protected]. >> Visit this group at https://groups.google.com/group/pestlist. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/pestlist/dd2219e5-2a0c-450d-8e9e-cec13df5e844%40googlegroups.com >> <https://groups.google.com/d/msgid/pestlist/dd2219e5-2a0c-450d-8e9e-cec13df5e844%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> > -- > You received this message because you are subscribed to the Google Groups > "Museumpests" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at https://groups.google.com/group/pestlist. > To view this discussion on the web visit > https://groups.google.com/d/msgid/pestlist/CAMxAh%2BjnqUB65JUBJ7SzV7%3Dm9xkkUucOx98ve30%2Btrb15Unr%2BA%40mail.gmail.com > <https://groups.google.com/d/msgid/pestlist/CAMxAh%2BjnqUB65JUBJ7SzV7%3Dm9xkkUucOx98ve30%2Btrb15Unr%2BA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Museumpests" group. 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