Quote:
Originally Posted by Drake
I would really like to have the the heat transfer directly into an insulated tank on the radiant side and am trying to find out if there is a proper exchanger to do that with refrigerents.
|
Well, if I'm understanding your quandry correctly, the heat pump I built, and then one I am building now are just a refrigeration compressor, a cap tube, and two brazed plate heat exchangers, hooked up in a circuit.
Regarding the heat exchangers, one is on the "source" side, which I usually call the ground loop side. This is where the heat comes from. It has water running through the odd-numbered channels, and refrigerant running through the even-numbered channels. Just before the refrigerant enters this exchanger, it emerges from the metering device, in my case this is a cap tube. When it emerges from the cap tube, it passes from a region of high pressure and enters a region of low pressure. In that region of low pressure, the refrigerant instantly changes from a liquid to a vapor and becomes very cold, much colder than the loop water that is circulating through this exchanger, so heat from the water migrates from the water to the refrigerant.
The other heat exchanger is on the "sink" side, this is the side where the useful heat is available. It also has water running through the odd-numbered channels, and refrigerant running through the even-numbered channels. The vapor that had picked up heat from the first HX (above) is routed through the compressor where it is squeezed to a point that is close to condensing, but the vapor is too hot to condense. This hot pressurized vapor is then routed through the second HX, which in your case has water from the PEX floor circulating through it. The PEX water is cooler than the hot compressed refrigerant vapor, so heat migrates from the vapor to the PEX water. As the heat from the vapor begins to migrate into the water the vapor cools enough so that condensation happens inside the heat exchanger. This condensation releases very large amounts of heat which also migrates into the PEX water.
* * *
So, getting back to your original question, "
...trying to find out if there is a proper exchanger to do that with refrigerents...", the answer is yes, there are many kinds of heat exchangers that can be used, but the best because of efficiency and also small size are brazed plate heat exchangers. They are usually too expensive for experimenters like us to buy, but the Chinese have come to our rescue by cranking out brazed plate heat exchangers by the millions.
Now, it turns out that making beer at home has become a popular hobby by people whose love of beer often exceeds their income. So to support these people in their quest for cheap beer, suppliers of the paraphernalia for beer making have started offering cheap brazed plate heat exchangers for sale on ebay.
This is where we come in...
I bought two for $70 each for my first prototype heat pump and they worked great, beyond my wildest expectations. Now, a couple of years later, I'm building a bigger heat pump and I just bought two more heat exchangers from the
same ebay guy, and the new HXs are 50% bigger and @ $79.95 each they are cheaper per BTU. As a bonus, some of the HXs are now even available with sweat fittings for brazing refrigeration line onto. If you don't find exactly what you want, he can do custom orders.
I couldn't be happier if I was actualy drinking beer!
-AC_Hacker