This is an interesting thread...
Quote:
Originally Posted by obxdave
I heard that you could use a frig to chill water to run though a water to air heat exchanger does any one know of this thank you for your help
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obxdave, I wish you'd included a bit more detail about where you're going with this, but...
Yes, you can use a frig or probably more correctly a vapor compression machine to chill water, and then use the water as your transport fluid to carry the heat (or cold in this case) to the place where you want to use it, as you said through a water to air heat exchanger.
Quote:
Originally Posted by Piwoslaw
Yes, you can do that, but it would be more efficient to delete the water part and directly chill the air.
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Piwoslaw is correct that you might be better to go directly from refrigerant-to -air, as you pay a penalty (somewhere around 10%) every time you go through a heat exchanger. In this case you pay the penalty when you go from refrigerant-to-water (10%) and again when you go from water-to-air (10%).
But there are cases when you can't do that, like if you have a centralized vapor-compression machine and you want the heat (or cool) ofice space twenty stories away.
Quote:
Originally Posted by Ryland
Where is the heat from the fridge going? also where is the heat from the pump, the friction of the water flowing in the pipes and all the other losses? [NOTE: this usually runs below 5% (-AC)] All of the energy that a system like this is going to use is going to be turned in to heat, add to that the fact that a fridge is just a heat pump with half of it inside of an insulated box, you are pulling heat out of that box and that keeps your food fresh and cool, ...
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Ryland has a good point of view here because he is considering not only the cold that is produced, but also the heat produced by the vapor compression process.
...this brings up another point that is worth keeping in mind, which is in a vapor compression process where the heat produced is of primary concern, like a house heating heat pump, the heat from the work of the pump is adding to overall efficiency.
But in a vapor compression process where the cold produced is of primary concern, like a refrigerator or an air conditioner, the heat from the work of the pump is subtracting from the overall efficiency.
Quote:
Originally Posted by Piwoslaw
Plus, as Ryland mentioned, you'll have some spare heat to deal with (in fact, you get more waste heat than you get chill), so if you divert that to your hot water tank then it'll definately be worth it.
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Yes, so long as the heat from the frig condenser coils is at a higher temp than the water tank. If the tank is a pre-heater, the temperature difference would defrinitely be greater, so the heat would flow easily. If the tank is the water heater tank and the temp was set high, like maybe 120 F (49 C) it might lower the efficiency of the frig.
Quote:
Originally Posted by Ryland
...the wast heat and the heat that was pulled out of the fridge escapes in to your kitchen, part of why kitchens are one of the warmest rooms in the house.
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Or at least 200 to 300 watts warmer. The stove is really a BIG heat maker.
But consider this: in the winter, when it is cold outside, we use heating to raise the temperature of the house, then we use a frig inside the house to lower the temperature of the inside of the frig box, and the vapor compression not only has to fight the home heating system, it also has to fight off the stove when we are cooking, and it also has to fight its own compressor which is throwing off heat! There's some serious inefficiency there.
Maybe feeling warm and comfy about how the frig keeps us warm, is misplaced gratitude.
Personally I don't think there's anything sacred about a frig... We need to take a whole new look at how we keep food cool, especially in the winter.
Sure, we need to keep food cool in the winter, but do we actually need to use a vapor compression machine? By most estimates, the refrigerator is the largest energy consuming appliance in the home (this is not counting a furnace or a water heater).
Maybe what we need is to use our local climate in a way that uses outside air to do the cooling, and perhaps a bit of inside air when it gets too close to freezing.
Any thoughts?
-AC_Hacker