subcooling liquid line

[mac_J]

Hello
Is there a improvement in systems performance, when a liquid line is clipped tightly to the suction line and both are insulated together.

This is related to DX heatpumps using 410a gas, with capacities around 14kW, suction lines would be 22mm and liquid line 10 mm, length. of lines would be approx 15 metres. Condensing temp would be 40 degrees C and evaporating would be minus 5C

Regards
johnf4@mac.com

[taz24]

Hello
Is there a improvement in systems performance, when a liquid line is clipped tightly to the suction line and both are insulated together.

This is related to DX heatpumps using 410a gas, with capacities around 14kW, suction lines would be 22mm and liquid line 10 mm, length. of lines would be approx 15 metres. Condensing temp would be 40 degrees C and evaporating would be minus 5C

Regards
johnf4@mac.com


Direct expansion?
You will have to expand on where the expansion is taking place.
Is the sytem purely a heat pump or is it reverse cycle air conditioning / heat pump.
It depends on where the metering / expansion device is.

Cheers taz.

[BigJon3475]

The thought is that the small area of the liquid line in contact with the suction line will help subcool the liquid even more. I think it's called aftercooler. It's suppose to add capacity in certain cases.

[gonefishing]

Not on a heat pump, ever. That suction line will be the discharge
line in the heat mode. The liquid line remains the liquid line.

Probably give all kinds of problems getting the system to feed
properly in the summer, and will flash all your liquid in the winter.

Keep them separated on heat pumps........always.

GF

[chillyblue]

Hi

You used to be able to strap both lines together (in the old days on cooling only units) as the expansion device was in the indoor unit, and in effect you could subcool the liquid before entering the expansion device.
Most expansion devices are now in the outdoor unit so strapping them together has no advantage.

Cheers
CB

[mac_J]

Re: sub cooling liquid and super heating suction

Please note the Heat Pumps are geothermal units direct expansion, there are used for heating only. The evaporator is a group of 3/8 x 250 feet long copper pipe loops, buried 4 feet deep. Number of loops vary from 8 to 14 depending on size of heat pump. The loops are fed by a distributor, the expansion takes place there and is located in the loop field. There is a suction manifold which picks up the returns from the ground loops.

I would assume the performance would be enhanced by clipping suction and liquid line together. By sub cooling liquid would give a greater refrigeration effect, super heating the suction would increase heat of the rejection, this heat is used to heat domestic hot water and underfloor heating in a brazed plate heat exchanger.

All comments and advice appreciated.

mac_J.

[SteinarN]

There is little to nothing to gain in to strap the suction and liquids pipes together on a R410A system. If it had been R404A for instance there would have been something to gain. Also to be avare of with R410A is that you get rather high discharge temperatures which is further increased with increased suction temperatures. However at -5/+40 that shouldnt be a problem anyway.