We’re planning an episode for our January 23rd/26th show all about energy, spurred on by the Spark community’s discussion about energy use and all our electronic tools/toys. As part of that, here’s a riddle sent to us by email from one of our listeners, Bruce MacDougall:
“A refrigerator sits in a perfectly insulated room, plugged in, with both the freezer and fridge doors wide open. Will the room get cooler, hotter, or stay the same temperature?”
What do you think? Personally, I have absolutely no idea, but I’m curious!
Leave your answer in the comments. Ten people will get a Spark reuseable grocery bag for posting! (don’t worry, you don’t need the right answer to win)
I think the room will get warmer.
In a “regular” room, the heat that is given off by the refrigerator would get vented away. This heat is a combination of the heat removed from the inside of the refrigerator plus the heat from the compressor.
In a perfectly insulated room this venting wouldn’t happen so the extra heat that is generated by the compressor will slowly raise the temperature of the room.
I’m with Colin – the room will heat up. Plus, that’s gotta be the answer to a question posed on a show about saving energy….
A refrigerator moves heat from one region (the ice box) to another (the room). But here, since both ice box and room are the same place, the temperature will stay the same, because there’s no where to shift the heat.
I agree. I think it will make the room hotter.
J.
I do not know the answer, but my thought is that the part about the environment being sealed is going to mean there is no change.
I suspect that the heat given off by the compressor and the cool air coming out the open doors will cancel each other out and the room will stay the same.
If there refrigerator were an ideal 100% efficient device, there would be no change at all given the purpose of the refrigerator is to transfer heat from the inside to the outside.
Unfortunately no real-word device is 100% efficient, and the inefficiencies (friction of motors, etc) will transfer the input electricity to heat.
Moxy Fruvus explains this well:
http://www.fruvous.com/b-lyr.html#entropy
*smile*
It’s tempting to think that the temperature will stay the same since the room is defined as “perfectly insulated” which means no heat can leave or enter. However energy is entering the room in the form of electricity. I doubt that a fridge compressor is a 100% perfect remover of heat… i.e. normally a fridge will generate more heat into the room than it removes from it’s interior. So I’d guess that the electric energy will ultimately convert to heat and raise the temperature.
I tend to agree with Colin Longman. The room will get warmer. His thoughts are echoed by most of the comments on this site about the same topic: http://www.funtrivia.com/askft/Question24894.html
Well, I can see the logic of the room getting warmer. Hmmm….
I think the room will get warmer – the real question is, who’s going to change the light bulb when it burns out?
As mentioned above, since there is a certain loss of energy in the compresor I tend to agree that the room will get warmer. Of course, the little light that’s on with the doors wide open gives off heat as well.
I think the room will get warmer. I was in the “stay the same” camp until I read Andrew Higg’s comment about the extra factor: electricity coming into the room.
Warmer. So sez I.
the temperature will raise, conservation of energy determines that. Because a fridge isn’t 100% efficient it will pull energy in to run the compressors and light’s. The energy going into the fridge will be more then is used to cool the room. if only 30% of the energy is used to cool the room then that leaves another 70% unaccounted for, most of that would be given off as heat. including the fact that all that a fridge does is move “temperatures” using a compressor the “coolness” of the fridge and freeze will be equally given off as heat, plus the extra heat energy given off as waste due to electrical and mechanical inefficiencies. So the room will get warmer(if it is perfectly insulated and isolated from outside).
The room gets warmer.
The refrigerator/freezer is a red herring; all a fridge/freezer does is move heat energy from one place to another. Since it is only moving it INSIDE a perfectly insulated room, the total heat energy inside that closed system stays the same from the refrigeration.
However, the system is only closed with regards to HEAT energy (the perfect insulation). Energy is flowing into the room in the form of electricity, and is being converted into heat by the mechanical action of the compressor, the heating of the wiring, and possibly the lights in the fridge/freezer.
Thus there is a net gain of heat energy within the room.
I’m enclined to agree with all of the previous comments ,that the room will get warmer. Maybe it will be colder at first and then warm up until the compresser dies from exhaustion and gives up
Hmmm. I think the room will get colder at first and the freezer/refrigerator interior will get warmer at first- because once the doors are opened, a temperature difference is caused within the room/refrigerator boundary. Think of this boundary as a membrane. Continue this analogy by considering how ATP is formed chemiosmotically by chloroplasts. Instead of protons being pumped across the thylakoid membrane from the stroma which makes the interior more acidic thus creating a pH difference, the air molecules escaping out of the interior of the refrigerator/freezer are “more colder” thus creating a temperature difference in the same way. In the choloroplast, the protons eventually diffuse back into the stroma to balance the difference. Therefore, the warm air molecules in the room will diffuse into the refrigerator and the cold air molecules will diffuse out of the refrigerator until a balaning in a final room temperature which will be the same as we began with. Remember too, that when cold and warm air meet, fog is produced and this requires energy.
Ah, you people have all missed it! The room will stay the same temperature, but it has nothing to do with how heat is transfered… Every fridge made has a fail safe that turns off the cooler when the doors are open for too long. The manufacturers realize that there is no point in removing heat from inside if the doors are open! Since the doors in this scenario are kept open, the fridge will turn itself off and thus not affect the room at all.
The room will have a dual temperature zone , since cool air falls and heat rises there will be a conflict where the 2 areas fight to balance out each other .
But the floor will be cooler than the ceiling .
I’m currently finishing off the final design for a new ECO fridge that will suprise many engineers because some of the old concepts
had a perfect solution for some features but as the fridge evolved the good ideas got lost in mass production and appearence issues .
I took all the good ideas and worked them into a Accessible-ECO concept that will help people right from the toddlers to the seniors with special needs , my compressor will be a new Oil-free version that runs at about 50% of the power for a current model of equal size.
The compressor , condenser, evaporator and electrics have been moved around to solve some the heat issues that also needed a second fan to cool the motor area from the heat build up just to cool the fridge interior.
I hope to have a complete patented version once my Industrial design application is approved and posted on the CIPO website , the actual working model will be an example for Manufacturers to make a License agreement with me to build it under their NamePlate.
There are a few areas in my design that can be annoying for the odd person but I designed it to be affordable at the $1500.00 range befor any Government rebates for Home improvements to save energy.
Actually, there's not enough info for a real answer. If the room began at 50,000degrees F the addition of some 110+F 'heat' escaping from the fridge pump could actually have a net cooling effect. Not a real likely scenario…but the net temperature change DOES relate to the initial temperature, it is not just an incremental 'sum' of heat sources.
Greetings. Very first I need to say that I actually like your blog, just found it last week but I’ve been reading it increasingly since then.
I look to consent with most of your respective thoughts and beliefs and this post is no exception.
Thank you for any excellent blog and I hope you keep up the excellent function. If you do I will carry on to look over it.
Use a wonderful evening.