[P-man]

I was thinking of venting the heat into the thermal room directly. It's kinda hard to explain without a drawing. Here I'll attach this rough sketch. Maybe it'll help. Anyways thanks for teaching me to learn.

[Borek]

Sketch?

OK, there is no one, but I think I know enough to ask you two questions.

First - what is planned temperature of your heat source?

Second - you wrote somewhere that you expect thermal room to be really hot, as you need to use high temperatures resistant insulator. So - what is your planned internal temperature of the thermal room? Is it higher than your heat source?

[P-man]

The fuel cell being the source of heat, PEMs function at around 200^oC. I don't mean to change that temperature.

OK, here is the sketch. I didn't have the right extention last time.

[buckminsterfullerene]

The fuel cell being the source of heat, PEMs function at around 200^oC. I don't mean to change that temperature.

OK, here is the sketch. I didn't have the right extention last time.

you mean 200^oF which would be equivalent to about 93.3^oC.

[P-man]

Sorry, I got confused. Wow, that's annoying. We'll need an accumulation of heat, then. A way to accumulate heat to raise the temperature. Anyone got any ideas?

[Borek]

OK, here goes your thermal room in more acceptable format.

As for your question - I doubt there exists method of changing the temperature to store the heat that will meet your criteria - small, fast and efficient. Commonly used device is unit as used in freezers and heat pumps. However, to be efficient it must be bulky and it needs additional energy to operate.

Note that the fact such a device doesn't exist doesn't mean it was not invented yet, it is rather effect of very fundamental aspects of thermodynamics. Units used in freezers and heat pumps are developed for at least 80 years (perhaps even longer, no exact idea) and they are as efficient as it is possible. They can be made to work faster but they will neeed more energy operate and the energy is what you are trying to conserve.

[billnotgatez]

Many people on this forum are well read in chemistry and not well read in physics. Many facets of thermodynamics seem to be lacking in replies here. Since I can not count my self as well read in any of the above, my response herewith is from intuition (gut feeling) based on discussions I have seen elsewhere.

The process of capturing and concentrating heat energy takes energy. Therefore a net gain in energy may not be cost effective. There is a rule about not being able to make a perpetual motion system.

It is difficult to get meaningful work out of a low-grade heat waste.  That is why they use low-grade heat to do other things. An example would be using waste steam from a power plant to heat a greenhouse in the winter.

Again I am not an authority on this topic and I do not know of a physics room that is as good as this chemistry forum. In the meantime it may be better to approach this project piecemeal and make your fuel cell first and worry about waste heat later.

[buckminsterfullerene]

you are right it will take lots of energy to get meaning ful heat directed to any one place from the small amounts produced in this fuel cell system, that is the ideaology behind a air conditioning which defies some laws by making the heat go to a place where it will set it of balance compared to the environment and that of a fridge or cooler, and they require large amounts of energy to operate.  the point is that it will not be easy because the heat will have a tendency to disperse and go to where there is less energy and disperse, unless you are building a large system capable of producing in the hundreds of degrees celcius i do not see how this will work in a fuel cell....

i would see all options first and then think if it will be possible to direct the heat flow to whatever you will be doing with it.  but yeah plan how the cell will work first.

[P-man]

This is where I am stuck. How do I get the heat tothe thermal room? If I insulated the fuel cell so the heat can't escape and only left the vents uninsulated, would theheat travel to them, and then to the thermal room?

[billnotgatez]

There is an experiment in thermodynamics that shows how heat energy flows.

Take one body that is cold and one that is hot. Put them in contact with each other and they will both become the same temperature that is midway between.

The above is an abbreviated explanation of the experiment.

[constant thinker]

Remember you don't get more energy out of something than you put in it (I don't know of any machines that are equal to or more than 100% efficient).

The question that also needs to be asked how much energy will it take to get the heat into the room by either blowers or w/e means necassary and will this produce enough energy to offset what is consumed and the extra weight that'll come from the extra parts (if used in car/moving object).

Maybe a reverse air conditioner might work. By this I mean in a normal case your taking heat out of the room your in and sending it to a different (semi) isolated area and cause the heat gradient to be higher outside of the room your in. Well why not take that and flip it around so your pulling heat into your "room". The heat would obviously come from the fuel cell or whatever is generating a significant amount of heat. As 3.3.141592653 says it'll take a lot of energy. I think one of the only ways to know how well this will work is to build a working model and see if you can get enough out of it to offset the consumption.

[Borek]

Maybe a reverse air conditioner might work.

The idea you are referring to is called heat pump and I have already mentioned it.

I think one of the only ways to know how well this will work is to build a working model and see if you can get enough out of it to offset the consumption.

No. Much simpler way will be to calculate heat pump energy consumption and efficiency, this is simple question that any engineer working in freezers/air conditioners industry will solve in 5 minutes - if not faster. These 5 minutes of thinking can save kdollars needed for serious prototype building.

In real life nobody is going to finance prototype building if such calculations were not done - unless it is a thermodynamical idiot believing in miracles.

[constant thinker]

Ooo. Sorry Borek I never put the two together. Yea your right about the calculating it. I think though it's a good bet if the calculations work out.

[P-man]

Thanks for everything.

I am now realizing the problems of making the heat go to the room. Yet in the common fuel cell they vent the heat out anyways. So why can't I just stick the room on instead of having the heat fly out? If I insulate the whole fuel cell except for the vents, won't the heat be automatically moved towards there. If I have one small spot in the thermal room that is a bit cooler, the heat might get attracted to it. Then close off connection to the fuel cell for a while and the equilibrium won't happen. Will the thermal room get hotter? Here is where the calculations come in. Unfortunately, I can't do them. HElp?

But now that I think of it, why not just insulate the fuel cell to make the stirling engine work?

Life is all about trial and error.