The Homemade Heat Pump Manifesto

[abogart]

Wow, thanks for crunching the numbers for me, AC! A lot of the calculations required for this stuff eludes me , I'm more of a trial-and-error kind of guy.

I figured it was worth a shot to throw the idea out there. The idea came from a system that was installed at the foundry that I worked at. They acquired a large (like swimming pool size) water tank, dropped it into a pit below the floor, and used it to collect the return water from an evaporative cooler unit. This was the system that provided cooling water for the water jackets of gas-fired molding machines. I'm not sure how much this setup helped, but it must have had some effect in the summer, when temps in the shop easily got into the 100's. From all of the machines, there must have been millions of BTU's per hour that the system had to remove. I do recall that the supply water from the tank was significantly cooler than on the old production line, which only had a large radiator-type cooler. But this might have just been due to using the evaporative cooler.

[AC_Hacker]

Originally Posted by abogart

From all of the machines, there must have been millions of BTU's per hour that the system had to remove. I do recall that the supply water from the tank was significantly cooler than on the old production line, which only had a large radiator-type cooler. But this might have just been due to using the evaporative cooler.

Yeah, most likely the evaporative cooler...

Whenever water changes state, in this case goes from a liquid to a gas (evaporation) a very large amount of heat is absorbed in the process.

This same principle is at work in refrigeration devices... a compressor forces the refrigerant to change from liquid to gas and back again. This causes a very large amount of heat to be absorbed (freezer) or released (heat pump).

Even though I have been working with this stuff for a few years now, it still seems like a miracle to me...

-AC_Hacker

[cbearden]

Originally Posted by AC_Hacker

I am repeatedly amazed at how much energy we are all using, and how completely unaware we are of the huge amount consumed.

Heck, yeah. This is exactly what I've been thinking for years.
Hats off to you on this quote!

[randen]

Well the first little heat-pump (version 1.0) left me a little chilled in the shop. The 2 ton maintained the shop around 58 F degs. My guess of 2 tons for the shop was a little shy of heat energy. But if it was able, the cost of heating the area would have been peanuts. Here we go again I've started the 3.5 ton unit. Using the CNC machine to make the 4 way valve and having another pc of stainless steel, one would be crazy not to make a spare. In one of the past posts someone was concerned about the heat energy transfer (conduction)through the stainless valve body reducing the effiency but the fluid is not in contact very much stainless, as the internal diverter is nylon. I know some may be a little hesitant about building a GSHP without having a machine shop. But I know that all these machine parts can be subsituted with tees,hose-barbs,compression fittings a number of ball valves and check valves.
The tube in shell was a very effective heat exchanger so I will use that tech again only a little larger. This time the outer shell is 1 3/8 ID and I will use 2 lenghts of 3/8 OD copper tube for the condensor. With this I can twist the two tubes together causing turbulence in the HX helping to remove the heat. The length is 15 ft. and this almost doubles the area used for the 2T shell & tube HX.
For the evaporator I'm going to use three 3/8" OD copper tubes because the doner cap tube has 6 capilleries so I will braze two into one 3/8" copper tube. The outer shell is a PVC tube used for hot tubs. Inexpensive but who knows how long it could last. The pressure used for the water/glycol is 30-40 PSI. Copper would last a very long time but the cost for 1 1/4" dia, wow and I would have difficulty coiling it.
The compressor is in very good shape. It hasn't operated very many hrs. These GSHP can operate for many years. I have an friend that has a commercial unit that has been heating the house for more than 25 yrs and has never been touched. I will post more pictures as I progress.

Randen

[Geo NR Gee]

Randen,
Thats great that you can make your own parts and put this thing together. I can't wait to hear how the finished product works.

[hydronics]

Hi all,

I thought I'd share my work a couple of years ago connecting a water-source heat pump to a large water heater.... the piping issues dealing with stratification and mixing I thought might be useful to those in the design phase. Have fun!

sites.google.com/site/alternativewaterheater/

[Vlad]

randen, Why are you so convinced to 4 way valves ?
And second You never mentioned what kind of metering device you used in your HP.

[AlanE]

Hey Vlad, welcome back. If you get the time I would really be appreciative if you could post some more photos of your drilling rig, as detailed as possible, because I'm going to try to build one and your specs and photos and wisdom could really help me. Standing on the shoulders of the wise men who traveled the road before me and all that.

Also, how did your flooring experiment work out?

I was so disappointed that you fell off the map before I joined the board. I read this entire thread and found a mountain of good information but while AC Hacker is still around and is actively sharing his knowledge you were the only one who went full-out with a drilling rig and for people who want to travel that route, there was no one else who did what you did (I'm not interested in drilling by hand like AC did, sorry AC.)

[randen]

Vlad

The reason for the 4 way valve was to have a counterflow of glycol/water with the refrigerant. The counterflow in the shell & tube heat exchanger is able to ensure the glycol/water has absorbed all the heat-energy before exiting. The switching from heating to cooling of both evaporator and condensor via the 4 way valve would always be counterflow. In an application of air to air its not necessary which direction the refrigerant is entering or exiting the heat-exchanger.

The metering device used was the capillery tube that came from the original doner unit. The temperature of the ground loop and the out going heat exchange is very constant therefore the refrigerant charge can be tuned for the most effective heat transfer being that the temps are uniform the presures stay in the sweet zone.

Even though my guess was a little shy on the amount of heat necessary for my shop the heat-pump is working very well. Its maintaining a shop temp of 14-17 Deg C. and the infloor office area is 20 Deg.C. The ground loop is a 4 ton install and the temps now are still 8 Deg. C. in and 7 Deg out to the loop. Although the unit runs 24/7 thats a lot of bang for the buck. The cost for heating with oil would have been $3000.00 using the heat conservatively. I beleive the little 2 Ton GSHP will get me through this mild winter for less than $800.00 and thats what its all about. I have started a 3.5 Ton HP but work has gotten in the way. Hopefully I can get it finished and installed before the heating season is over and I can compare the performance.

Randen

[Vlad]

I don't want to spam home made heat pump discussion with drilling and floors. It took me few hours to read through. If somebody could direct me where to post this things I will do so. I do have interesting info about flooring, because it is working great.

randen, the reasons I asked you this 2 questions are

1. If you look at WSHP used in many office buildings they do not have 4 way valve for water circuit.
2. Because you used some stock parts (compressor, metering device (MD), etc) you have to follow some basic rules:
a. pressure drop across MD (changes capacity of MD)
b. superheat (lowers COP but saves compressor, necessary evil)
c. sub-cooling (changes capacity of MD, COP)
d. you have to consider refrigerant state (liquid, sub-cooled liquid, saturated gas, superheated gas, etc)
When you reverse water flow you change evaporator(condenser) capacity, may be you do not need it.
Most water cooled walk-in coolers freezers have water regulating valve (which regulates water flow and condenser capacity ). If you crank it wide open the discharge pressure will drop and your system will get off balance. Your MD will stop feeding refrigerant.....because it was designed for particular pressure drop.

I am not an ac guru by any means but basics are basics.

Lets combine science and our eager to invent things and we will have better results.