Very low condensing pressure

[Peter_1]

Anyone already tried/experimented with very low condensing pressures?
Idea (already tested with a small scroll compressor on R404a and a free-ar blowing evaporator) : make an earthcoil in copper (+/- 1,5 m or 5 feet deep), eventually some circuits of 5/8 to a header, condensing at 20°C to 22°C and evaporating at -8°C. Hughe COP. Even a efficient subcooling coil can be made this way.
Selecting TEV according to this little pressure difference must be possible or use of stepper motor EV or PWM Danfoss AKV.

[Andy]

Hi Daliti
We have one NH3 Low Pressure Receiver system (liquid overfeed) running on blast freezer duty that condenses at 10 to 12 deg C during the winter on an evaporative condenser. The condenser was sized for two screw packs but only one was fitted.
What were you thinking of, possibly wasting the heat to a ground loop
Regards. Andy

[Peter_1]

WE also have one client with a similar NH3 compound freezer witch condenses at -12°C (liquid overfeed in the LP tank for the cooling rooms)
Exactly, I was thinking of a vertical ground loop (now tested horizontal) Meaning is to reduce enromous the input power. This is better for the environment, for the clients wallet (is this the correct expression) due to a serious reduced electricity bill and this will create new oppurtunities for us to sell something someone else doesn't.
I'm not really affraid of leaking because copper is fairly resistant to everything (they found intact coins of the Romans), and see some possible solutions (already tested) for oil retun in vertical systems.
We made an offer for a small meat factory. The have to add +/- 80 kW of refr. capacity While there has to be digged in the ground for the construction of the buidling itself, we proposed the owner to burry some horizontal earth coils deep beneath the earth, There will be done also al lot of excavation for the layin-out of a parking. ALso there, there are some possibilities i think.
What do you think? Is it worth a try?
Peter

[chemi-cool]

Hi Dality,
I would advice you to check the acidity of the soil. High acid will make your copper disapear into brown dust.
You could have coat them with epocsy paint for complete protection. I have built a small ac unit 1 ton some 12 years ago. Still runing with no problems.
Good luck.
Chemi

[Andy]

Daliti,
I do a little work for a company that uses the heat from the ground and a heat pump to heat domestic and commercial properties.
The ground loops are made from plastic pipe, the same type used for water supplies.
Several loops are possible, horizonal at about 1.5m down or a vetical loop, which is really a bore well. The bore well will have the warmest water of the two, but only slightly and you are not relying on the soil to carry the heat away. We have not used any bore wells yet so I will have to ask about the configuration.
You have hit on an idea that a lot of us are toying with, but the problem is the cost of instalation, bore wells are not cheap, but if you have another use for the water (cleaning in a meat plant) it may make sense.
For horizontal loops you will need 75M of 1" n.b pipe for each 1 to 1.5kW heat rejection.
Size you heat exchanger for a 4 to 8 deg C Temperature Differerance, the smaller the better.
Keep in touch regards. Andy

[Peter_1]

I already did some trials mith PE pipes.
The big advantage of using copper tubes is the eliminating of a heat exchanger, pumps, water, glycol etc. The second advantage will be that by eliminating a heat exchanger, we can lower appr. 8K the condensing pressure.
I also have almost all the books of the IGSHPA with lot of only practical information.
I agree that drilling the holes is expensive but i was thinking of a smaller (cheaper) drillingmachine for thise purpose, something like http://www.littlebeaver.com/bbpm.htm They also have a movie on there site.
But in my case, there have do be done a lot of ground works with big grues before poring concrete. I can lay without any problem several horizontal loops, widely spread.
In Belgium, it is also forbidden to pump water from the underground (open well) for heat pump applications, unless you drill a second well to pump back the water in the underground.
A closed loop is naturally no problem.

[DaBit]

If you can fit the copper below ground water levels I'd say it is definitely worth a try. It also keeps condensing temperature fairly constant.

I only wonder if the extra piping, refrigerant and installation needed weights up against the advantage. Temperatures in Belgium are not much higher than in The Netherlands, which means that you can keep condensing temps low during the largest part of the year with normal aircooled condenser coils.

[Peter_1]

[QUOTE]Originally posted by DaBit
[B]If you can fit the copper below ground water levels I'd say it is definitely worth a try. It also keeps condensing temperature fairly constant.

The water beneath has the same temperature as the surounding soil. Anyway, the condensing temperature will stay the same because the soil at a depth of >10m is almost inhexhaustible.


I only wonder if the extra piping, refrigerant and installation needed weights up against the advantage.

It surely will be. And we may not think always in terms of saving money. We also have to take care for the environment, the future of our kids. This is where the government should help a lot more those ideas.
The COP increases enormous. We made some time ago a rude calculation for a supermarket (Carrefour, 2 freezer packs of +/- 125 HP and 2 cooling packs of +/- 175 HP) and we could lower the energy cost with +/- 25000 €/year to 30.000 €/year. For such a saving, you can do a lot of work, projected to write the total investment of in 5 years.

Temperatures in Belgium are not much higher than in The Netherlands, which means that you can keep condensing temps low during the largest part of the year with normal aircooled condenser coils.

Sometimes place for this condensors is not available and especially those low noise condensors The regulations concerning noise are very difficult to achive for the moment (< 32dBA@10 m during the nights and 36 dBA from 07:00PM till 10:00 PM,+/- 40 dBA during the day)
And also when you need the most cooling capacity, you have the worst outside temperatures to achieve this.
You also never can condense at constant temperatures of 20°C
to 22 °C. One of the ideas of the technical department of Carrefour was to lower the condensing pressures as low as possible and boost the liquid up with an LAP. (This was in fact how i found this forum by reading an article of Marc of Fridgetech).

[chemi-cool]

hi Daliti,
Check at: http://www.igshpa.okstate.edu/
I belive you can find answers there.
Good luck with the project.

chemi

[Peter_1]

Chech my post of 18-11-2003, two up.