Cooling condenser of split with condensate from evaporator

[smileypete]

Hi,

Would pumping condensate over the fins of the condenser in a split air conditioner result in a worthwhile improvement in efficiency?

I'd have thought it would lower the pressure in the condenser and in turn help the compressor to pump more refrigerant vapour and lower the vacuum in the evaporator too.

Also is the condensate likely to corrode the evaporator? I'd have thought not as it's basically distilled water, if the split is a heat pump the condenser in the outdoor unit will be designed to cope with condensate too.

cheers,
Pete.

[Abe]

I would say not worthwhile increase in efficiency, but it wont hurt matters.........

[chemi-cool]

The condensate water will rut the steel on the out door unit.

Do not do it. You will gain nothing.

Chemi

[frank]

Would pumping condensate over the fins of the condenser in a split air conditioner result in a worthwhile improvement in efficiency?

yes it would as the condenser would lose heat adiabatically to evaporate the water.

I'd have thought it would lower the pressure in the condenser[

yes it would.

and lower the vacuum in the evaporator

On systems that operate with the suction in a vacuum, adiabatic cooling is not normally required

Also is the condensate likely to corrode the evaporator?

I thought we were talking about running condensate over the condenser coil?

if the split is a heat pump

Split systems don't normally run with the suction in a vacuum

The problem with using water to cool the condenser is mostly related to Legionella. The water not evaporated tends to collect in a pool below the condenser coil and in certain circumstances Legionella spores can be circulated by the condenser fan.

Is it worth the hassel?

[smileypete]

I thought we were talking about running condensate over the condenser coil?

Oops, quite correct I meant condenser.

Split systems don't normally run with the suction in a vacuum

I see, so the evaporator is at a lower pressure than the condenser, rather than being in a vacuum?

So lowering pressure in the condenser would allow the compressor to pump more refrigerant vapour, in turn lowering pressure in the evaporator.

Still the cooling depends on the amount of liquid refrigerant going through the capilliary/expansion valve, so would the above increase this?

The problem with using water to cool the condenser is mostly related to Legionella. The water not evaporated tends to collect in a pool below the condenser coil and in certain circumstances Legionella spores can be circulated by the condenser fan.

True, although problems only occur when the bacteria is 'aerosolised' such as in a cooling tower, shower head or even peat dust(!). Evaporative coolers could cause problems with legionella but have a history of safety as the water is not turned into a spray.

Is it worth the hassel?

Might be worth trying out with some distilled water on the condenser to see if it lowers the air temperature from the evaporator.

cheers,
Pete.

[coolman]

Some Airconditioners are actually designed for this.
They can be recognized bij a connection on the side of the bottom tray of the condesing unit end the fan is fitted with a ring on the edges op the fanblades.
This ring picks up the water en spray it on to the condensor.

It has a big effect on the capacity.
With extreem hot weather like past days it is a difference of a blazing hot liquid line or a reasonable cold liquid line.

The condensor should not be soaked with water but just lightly moist.

If you want to try it out, take a whatever condensor of a small unit, connect your gauges, take a spraying flask, take the pressure readings, spray some water on the condensor and see how the pressure lowers.

Victor

[frank]

True, although problems only occur when the bacteria is 'aerosolised' such as in a cooling tower, shower head or even peat dust(!). Evaporative coolers could cause problems with legionella but have a history of safety as the water is not turned into a spray.

I think you will find that all evaporative condensers enhance their cooling capacity by the fact that water "spray" is drawn onto the coil by the fans. Adiabatic coolers have water trickled down a series of "filters" where the air passing through the "filters" is cooled adiabatically.

The water that is "misted" onto an evaporative condenser usually passes through some sort of water treatment process to kill the bacteria (mostly UV light) but it is the water that collects under the coil, either in the drain pan or on the floor that "ponds" and that can be the cause of Legionella. This needs to be treated as well.

[frank]

Still the cooling depends on the amount of liquid refrigerant going through the capilliary/expansion valve, so would the above increase this?

The amount of liquid refrigerant passing through the metering device is not increased by the condenser being cooled more. The refrigerant quality is enhanced. With a lower liquid temperature during high ambients you get an increase in refrigeration duty. This can be seen on a Mollier chart.

[rbartlett]

All window rattlers are designed with slinger rings on the condenser fan and condensers are sized accordingly

Unless in a particulary hot climate the addition of water to a clean condenser on a modern 'japanese' type split is totally unncessary -most in the UK are over condensing enough already- as they are all designed to 46 deg'c operation.

The addition of water on an already over efficient condenser will lower the refrigerant pressure/flow, reducing capacity and increase the chance of icing on the evaparator.

This is why most splits need F.S.C for comms rooms etc during winter

Don't do it...don't bother........

Cheers

Richard

[smileypete]

Hi,

Thanks for the replies.

So it looks like cooling the condenser would increase the enthalpy of the refrigerant, but will also reduce the capacity of the system in a conventional split as the pressure forcing refrigerant through the capilliary will be lower.

I expect the newer 'inverter' splits with a linear expansion valve might benefit though.

Also trickling the water over the coil for adiabatic cooling instead of spraying it would give less potential for problems with Legionella.

cheers,
Pete.

[benijoseph]

Hi,

Would pumping condensate over the fins of the condenser in a split air conditioner result in a worthwhile improvement in efficiency?

I'd have thought it would lower the pressure in the condenser and in turn help the compressor to pump more refrigerant vapour and lower the vacuum in the evaporator too.

Also is the condensate likely to corrode the evaporator? I'd have thought not as it's basically distilled water, if the split is a heat pump the condenser in the outdoor unit will be designed to cope with condensate too.

cheers,
Pete.

MR, SIMLY,

WORTH EXPERIMENTING , not to use , if not designed for moist spray, time pass.

beni joseph,

[Stuart]

Hi,

Thanks for the replies.

So it looks like cooling the condenser would increase the enthalpy of the refrigerant, but will also reduce the capacity of the system in a conventional split as the pressure forcing refrigerant through the capilliary will be lower.

I expect the newer 'inverter' splits with a linear expansion valve might benefit though.

Also trickling the water over the coil for adiabatic cooling instead of spraying it would give less potential for problems with Legionella.

cheers,
Pete.

If the ambient temp is high enough for the system to require the condense to be discharged onto the condenser unit then it will surely evaporate before any bacteria can cause a problem.

Also heat pumps produce water in heating mode so provision is made for water to drain away, thus removing the chance of water build up & growth of bacteria.

If the ambient temp is below 30c then there is no need for the condense to be directed onto the condenser, but could in theory aid in high temps providing that the flow was of a suitable level. More than likely it will not be great enough to have any noticeable effect.