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Is heat pipe is effective to evacuate the heat out of the system during heat season ? Answered

I want to maintain a temperature of water feed into an equipment to be  no less than 0 C in winter and no more than 20 C in summer case using a heat pipe technology. The surrounding temp is about -15 C in Winter and 40 C in summer. How is it possible? Please advice !


You will need active cooling to achieve those temps. Even under the most ideal conditions a heat pipe system can't keep temps close to ambient temperature.

Would you please give more details or example to illustrate your point ? Thanks !

You can't pipe heat from a colder place to a hotter place without a PUMP. A PIPE is not a pump.


Heat will always go from hotter to colder unless something is forcing it to go the other way.
@author another option if you have the space/huge project for it - is a heat battery. Basically, build a HUGE underground pool in your back yard, insulated, and filled with gravel and water. In the winter, circulate the contained water through outside radiators to chill it all winter, then use that giant buried block of cold to chill to your requirements in the summer. Alternately, heat the battery all summer and use that heat for the winter; depends on which costs more, heating or cooling in your area.

Why the gravel ? Surely the thermal mass of water is higher than the mixture ?

It's going to be the size of a swimming pool, and if you still want a back yard, you probably want it to have some vertical holding power, especially since it's going to be insulated.

Actually, the instrument is inside a block which is 50x50x120 cm. with adequate insulation system. So, the size is very small.

Another question, is it possible to use soil as a heat source and heat sync depending on the season? In case we use heat pipe.

so long as you are moving heat from hot object to cold soil - or 'hot' soil to cold object, yes.

Think of a heat pipe as a heat conductor - it doesn't do anything special except move heat efficiently. A heat pipe works very similarly to a copper wire - make one and hot and the other end will get warm by conduction. Inside the heat pipe it will move heat by phase change triggered by the temperature difference between the hot side and the sink side.

It is clear that the surrounding environment will have a higher temp ( +40 C ) so it can not act as a heat sync. Now I am considering the soil as a heat sync, yet I am not sure if the soil will have a lower temp than the instrument in summer condition, so we can evacuate the heat to the soil. What do you think ? thanks

Below a certain depth (I don't remember what its called) there is a point at which you reach a temperature that does not change with seasonal temperature; it's something like 6 feet down, where the ground always maintains 5-10C until you start getting really deep (like in a coal mine) that it starts to heat up again.

Depends where you are in the world to some extent though.

I did them forever ago on the back of a napkin, since there is no phase change for most of the world especially if using a glycol additive (for ultra cold climate swings, i.e. here in Canada it can easily go from -45 in a winter to +40 summer peak to peak. The capacity is fairly straightforward as an average specific heat of the combined material...I'd have to do the math again, but if you get that block of water/rock down to ambient in the winter with passive radiators or even positive pumps we figured you could (with a well insulated house) eliminate your cooling bill. For us, heating is much cheaper than cooling - huge natural gas deposits mean gas furnaces are much cheaper and more efficient than electric resistive or heat pumps.

I was thinking about this again. How does the heat capacity versus weight for water and, say, granite per unit weight compare ? Presumably your water glycol mix acts just as the working fluid then.

liquid Water has a specific heat of ~4 J/gºC
Concrete has 0.8J...
Vegetable oil is 2.0
Granite is 0.79

Metals are generally lower, steel is 0.5

Water is the king in this storage war, if we're considering non-gasses.

But since granite is 2.8 x more dense than water, per unit volume, its only half as bad as water. But easier to stand on....

That would explain why wikipedia has a list sortable by specific heat by mass and by constant volume/pressure...It seems now obvious that you need to keep density in anything that operates on mass.

Yeah, but water's easier to pump than liquid granite ;-)

Using a heat pipe is no different then using a large heat sync. Either way a large heat sync is needed. The benefit of the heat pipe is how fast it is able to move the heat away from the source. It also allows you to place the heat sync in a better place where it can get better airflow. Just like a heat sync once it heats up it can only cool as fast as that heat is able to dissipate into the air. So your source will only be able to reach several degrees above ambient temps. In most cases 10 degrees or more. Depending on the heat pipes and how large the heat sync is.

Heat pipes are not the answer your looking for.

Thanks for your answer. My goal is to bring the temp of the system to less than 20 C in summer time given that environment temp is +40 C, . To do so I am considering to dissipate the heat into surrounding air ( my heat sync) using heat pipe. If it is not possible ( heat flows from hotter to colder), what is the alternative ? ( no pumps )..

Buried deeply, and with a low load, ie well insulated, a heat pipe/soil sink (not sync) might work.

Only under better than ideal conditions will the heat pipe be able to bring the block temp to ambient air temp. It can't make the block cooler than the outside air. The heat pipe isn't able to pull enough heat to make it cooler that the outside air it dissipates heat just like a heat sync does. It's just able to move that heat away from the source a bit faster.