20 oz Yeti Fail?

Jeepster47

Several folks have mentioned that they think their Yeti Tumbler has given up the vacuum and is no longer functioning.  So, I've got a proposition ... could be a good test, or could be a bust.  It's easier to measure how fast a hot liquid cools, thus that's the test we'll use.  Here's the graph from my 20 oz Yeti Tumbler ... brand new, so it should be a good benchmark!



Here's the deal ... I tested my tumbler in 75 degree ambient, so you need to adjust the start/stop temps if your room temp is different.  Add 105 degrees to your room temp to come up with your start temp.  Then subtract 40 degrees from your start temp to come up with your end temp.  (A room temp of 60 degrees yields a start temp of 165 degrees and an end temp of 125 degrees.)

Fill the tumbler with hot water that is hotter than your start temp.  Measure the water temp about three inches down from the surface. A Thermopen is great for this usage ... if you're a real nerd, then flip the #2 switch to measure to the nearest 0.1 degree.  When it cools to your start temp, then start a stop watch.  When it cools to your end temp, then stop the watch.  No fancy curves, least squared analysis, nor curve smoothing, etc ... just measure the time it takes to cool down 40 degrees.  Now, if you did it with the top off and your time is 0.7 hrs, then your tumbler is good!  If you did it with the top on and your time is 2.9 hrs, then again your tumbler is good.  If your times are shorter, then your tumbler has lost some efficiency. 

@nolaegghead suggests that the insulating value of a vacuum is R100 and a lost vacuum is about R1.  Thus, if our times are close, then call it good.  If the times are far off, then we might have a good test for determining if your tumbler is good or not.

If you do this test, please report your time. 

SGH

@Jeepster47 - I ran a test not quite as scientific as yours a few days back. I took my Yeti 30 out with me while bush hogging. The day in question was 102 degrees with 92% humidity. The feels like temperature was 124 degrees according to a weather app on my iPhone. I filled the Yeti as full as I could get it with ice followed by water. After 8 hours I still had about a 1/4 cup of ice. For comparison I filled a standard Mason jar (which I normally drink out of) full of ice followed by water as well and sat it outside. The ice was gone in less than 15 minutes in the Mason jar. While this is certainly not a scientific test, it did provide a good overview of how well the Yeti performed against normal everyday cups. And for clarity, the Yeti was in the direct sun sitting in the cup holder on my tractor for the entire time. Never once was it in the shade. I can't say that Yeti makes the best cooler out there as I have not tested them all as of yet, but I can say with 100% certainty that the Yeti cup beats the pants off of my old Mason jar.  

Legume

Math vs country wisdom.  Love it.

SGH

Legume said:

Math vs country wisdom.  Love it.

Never was very good at math. As such, I improvise

MaskedMarvel

Decades ago, a guy named Cecil Adams did a pseudo scientific test to determine the effect of evaporation on a hot cup,of coffee. He literally tested temperature loss between a cup in a freezer and a cup being blasted with a hair dryer. 

The hairdryer cooled the cup dramatically faster than the freezer. 


keep your lid on your yeti. 



And read The Straight Dope. 

nolaegghead

Nice test.  I'd argue as devil's advocate the vapor pressure at higher temps increases the evaporative cooling effects.   So by your rules, if your ambient (Kuwait in summer) is 110, then add 105.....hell, it's boiling before I get there!  Seriously though, the delta from ambient can influence evaporative cooling through relative vapor pressure, and that's also dependent on humidity and barometric pressure.

HOWEVER, your test is perfectly fine to determine if the vacuum is broken.