I once placed a can of beer in the freezer for an hour. It did not freeze, and it was great.
However, now I need to cool some whipped cream (un-whipped), and the packet says I need to keep it in the fridge for 24h. But I don't have that long; and I'm worried that keeping it for 1h might be too long.
Is there a rule of thumb (perhaps in relation to weight), or do you have experience with how long I should keep this in the freezer?
One could probably figure it out, but imagine the variables: (a) temperature of the liquid before entering the freezer, (b) volume of liquid, (c) shape of container, (d) temperature of freezer, (e) air circulation in freezer, (f) desired final temperature...I would eye-ball it. Give it 30 minutes, check, and proceed one way or the other.
Not the answer you expect.
Cream freezes at 31.5 F. Put it in a covered bowl and float it in ice water. Better yet a cooler with ice water you can close.
Not only do you have an optimal temperature but liquid versus air heat transfer is like 100:1. Liquid density is like 1000:1.
You can drop a beer can in ice water and have a cool refreshment in 10 minutes.
If you insists on fridge / freezer I would do 1 hr rotation fridge (first) then freezer until you get what works. Maybe like 4-6 hours.
It depends on the volume. 15 - 20 minutes for about 250 ml cream should chill it. If you have less time, pour it into a plastic/freeze proof tub with a large surface area. The plastic tubs for cream are generally quite compact. So increasing the surface area will help to cool it.
I've made my own icecream a few times and because I don't have an icecream maker, I pour the cream mixture (about one litre) into a large tub. I then have to take it out at approximately half hourly intervals a few times to stir it. So you need less time than that as you don't want to freeze the cream and also likely you're using a smaller volume.
The reason your beer did not freeze is because it contains alcohol which has a much lower freezing point than water. The lower the alcohol content the closer the freezing point of the drink will be to water/ice.
Chilling whipped cream
After 1h it did not freeze.
However, I then put it in the fridge for an hour, and then in the freezer again, for half an hour. It was a bit frozen, but not entirely.
Chilling beer
An experiment with an IR thermometer, a 0.5l (tiny bit more than a pint) bottle of beer and my -18°C (-0.4°F) freezer. I measured the surface at the widest part of the glass:
After pouring it in a mug and taking away the foam so I could measure the liquid, it was 4°C (39.2°F). The contents were still a bit warmer than the glass surface.
Equation
For purposes of estimating the liquid inside, I used 12.2°C instead of the outside surface 10.2°C at time 30 min. I experimentally found an equation:
T_1 = T_f - (T_f - T_0) * (t ^ -0.1043)
Where T_0 is the initial temperature of the beer, T_1 is the final, T_f is the freezer temperature, and t is the time spent in the freezer. Temperatures work with both degrees Celsius and Fahrenheit (just make them consistent), and time is in minutes.
Doing a similar experiment with a 72cl glass jar of water warming up to room temperature, I got -0.1008 as the exponent instead of -0.1043, so you can judge the accuracy.