Bored? Challenge question of the day...

OttoNP · Addict Joined: 13 Jan 2003 Posts: 848 City: MI

Okay, so I have this kegerator and recently I had no place to put a extra keg of guinness, since I knew it wouldn't get over the critical beer temp of 40 outside, I left it outside. Once it started getting colder, I figured it might freeze and would probably just push some beer out as the pressure builds, which it did.

I've moved the keg inside now and my challenge questions is how long will it take for the keg to unfreeze? I know the answer, so this is just if your bored...It's also a good example of why school is important, I need to know how long before I can enjoy the Guinness Goodness.

Nick
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Vaporizor

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

I don't know about the keg problem you are having, but I do know something else you may find interesting.

Fish will reproduce in a lake at an exponential rate in a perfect lake with no size limit. A car will slow down at an exponential rate on a perfect road with no wind. Coffee will cool at an exponential rate until it reaches room temp... Oh yea, A cold beer will warm to room temperature at an exponential rate.

We have this CBL temperature probe here at work and I thought of a good use of it. I wanted to figure out if it is really an advantage to pour a beer in a frozen pint glass or not. Well, it is. I used water in my experiment so as to not waist a beer. I poured water at refrigerator temp. into a frozen pint glass sitting in a room (kitchen). It actually dropped the temperature of the beer a few degrees. But for how long? It took 12mins 23secs until the temp of the water returned to refrigerator temperature. Of course I was not drinking the liquid and I was not holding the glass with my warm hands.

J-Ro · Posted: Jan 29, 2003 10:00 am Post subject:

I have frozen a keg or three in my time. What you do is let it thaw out SLOWLY. Do not tap it in any way and try not to move it much as it thaws. It might taste a little different but you won't care cuz you will have saved some cash. If possible let it thaw in the kegarator so it doesn't get too warm too fast. Very Happy

J-Ro · Posted: Jan 29, 2003 10:05 am Post subject:

Interesting tip on the frozen glass thing. If you are having trouble pouring a pint and it foaming, use a room temp glass. It doesn't foam as much but I don't know why.

ohsix · Posted: Jan 29, 2003 11:04 am Post subject:

Breezer · Outlaw Joined: 17 Jan 2003 Posts: 246 City: Austin

Wes, I think he wants to know is approximately how long. If you are in my kitchen it takes approx. 12 minutes for a cold brew to get back to ref temp if poured into a frozed pint glass.

OttoNP · Addict Joined: 13 Jan 2003 Posts: 848 City: MI

Actually Wes in on the right track. What I'm doing is leaving the keg in the kitchen until it is unfrozen, then I'll put it in the kegerator. I don't want to leave it in the kitchen too long, if it gets too warm the beer will be ruined. Since I'm rarely home and can't watch it, I wanted to figure out about how long it should take to unfreeze. Basic question is how long will it take 13.2 gallons of beer to change from solid ice to liquid at the same temperature. At some point you need to make assumptions, these are the ones I made:

Room temp is 70 (it really is)
Beer is same as water (close, since beer is mostly water)
The keg is made of aluminum, which conducts heat very well, so neglect it
No heat transfer through bottom of keg

Nick
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Vaporgenie

Dan Lee · Newbie Joined: 21 Jan 2003 Posts: 48 City: Scottsdale

typically a keg will be "drinkable" in an aluminum keg for 4 hours. The thick black coated kegs generally last about 1-2 hours longer. 36-38 degrees is the ideal temp for draft beer, it will pour and taste the best. I would estimate that this keg would thaw out in about 10 hours, however the outside will thaw first and there will be a large cylinder shaped cube that will slowly melt until it is gone. I haven't seen that spill over like that before, so I don't know if it's good or not

I ran a company in college that did routine sanitizing of draft beer systems at about 35 bars in my town, and also had some rockin house parties in the WI winters.

ricktrav · Criminal Joined: 15 Jan 2003 Posts: 54 City: san diego

IF YOUR BEER FOAMS WHEN YOU POUR IT WIPE THE SID OF YOUR NOSE WITH YOUR FINGER, TAKE YOUR FINGER AND JUST TOUCH THE FOAM AND IT WILL GO RIGHT DOWN

Mariognarly · Addict Joined: 14 Jan 2003 Posts: 853

wow, all these things I didnt know....pretty interesting...one thing I can share about beer is the slower you pour it and the greater the angle you pour it at, the less head you will get. I pour beer in my part time job, I had to take a course on it and everything, but ya...try it out sometime, it works Smile

......because we all know how us beer drinkers hate head Cool

ohsix · Posted: Jan 30, 2003 12:15 pm Post subject:

OttoNP · Addict Joined: 13 Jan 2003 Posts: 848 City: MI

The oil/grease on your skin is what causes the foam to go down. I'll post the answer to my question tomorrow...

ohsix · Posted: Jan 30, 2003 2:39 pm Post subject:

Adam Greer · Posted: Jan 30, 2003 3:20 pm Post subject:

a little bit of salt will do it too...also if you put salt on your napkin befor you set your wet drink on it the napkin wont stick to the bottom of your glass.

kyle · Guest

i hate guinness

ohsix · Posted: Jan 30, 2003 4:43 pm Post subject:

OttoNP · Addict Joined: 13 Jan 2003 Posts: 848 City: MI

Here is how to figure it out:

Use assumptions from earlier post and approx densitys/temps, you need to figure out two things, find out how much energy it will take to change 13.2 gallons of frozen water to liquid water and how long it will take for it to gain this energy from heat transfer.

Finding the mass of the water is easy, 13.2 gallons is 50 liters, water's mass is around 1000 kg/m^3, so the mass of water is 50 kg. Water's heat of fusion is 79.7 cal/gram, so it needs to gain 3985000 calories. Converting this to Joules at 4.186 joules per calorie gives 16681210 J. The is how much energy must be transfered to the keg via heat transfer.

How long it takes depends on the convective/conduction/radiation constant, how much surface area of the keg is exposed, and the temperature difference. Since a keg has a diameter of 16" and a height of 23", its side surface area is .75 m^2 and its top surface area is .13 m^2. The convective/conduction/radiation constant can be figured out many different ways, a pretty good one from a chart is 4 W/m^2*C. The room temperature of 70 Fahrenheit is 21.1 celsious, putting this together gives a heat transfer rate of:

q=4*(.13+.75)*(21.1-0)
q=73.9 Watts

Now you just have to divide to find the time, 16681210 J/73.9 W= 225608 seconds or about 63 hours, which is about how long it actually took...

Nick
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Coach Purses