Evaporative Coolers?

[PurplePenguin]

My question goes towards making a A/C unit pump out more or colder air on a hot day..

Could you direct a Evaporative Coolers output to a A/C units condenser unit to make the A/C produce colder air?

Again..
I have a few Semi-Truck trailers.. They have 3 3-ton A/C units with the Condenser mounted below the trailer. There is a "skirt" that goes around the trailer to make it look more.. finished instead of like a trailer.

The problem is under that "skirt" it gets quite warm as you could imagine from having 3 3-ton units operating full blast for a few hours on a 100+ degree day.

My question is would putting a Evaporative Cooler under there produce colder air for the condensers to use so that they in turn produce colder air..

Or would the Humidity factor into that and they would end up canceling each other out?

-Eric Peters

 

[rmw]

Evaporative coolers would cool the atmosphere under the trailer, and since the condenser works on sensible temperature no matter what the humidity, it would welcome the cooler air.

The air under your trailer is your heat sink for the A/C units, and anything you can do to reduce the temperature down there helps the efficiency of the A/C.

Good idea.

rmw

 

[quark]

This issue was already discussed in a previous thread. Evaporative cooler idea works fine if the wet bulb depression is more(i.e diff. between DBT and WBT) and at the best you can get reduction of 90% in the wet bulb depression.

Secondly you are not supposed to overcool the air because of obvious problems with liquid entering the compressor. Note that capacity control is not very good with small DX systems and there are more chances of liquid entering your compressor.

Further, I wish not to cool the freon much below its saturation temperature.

Your final temperature in a controlled space depends upon heat load in the room and reduced condensing temperature has little effect on it. You may get some reduction in power consumption.

Just arrange a way to throw out the heated air by some sort of grill arrangement in the skirt.

Regards,

 

[imok2]

In order to save money and maintenace costs might I suggest having louvers on the skirting to take advantage of natural convection

 

[rmw]

I understood that the space he was trying to cool was not the controlled space, but the heat rejection space. If that is so, the louvers are an excellent idea, as is the evaporative cooler.

Make sure I understand it. YOu have the bottom of the trailers skirted, and you have the condensing units inside those skirts?? Which results in the high temperatures under the trailer floor???

You need to get those in the open, or open up some ventilation paths to them so that they can get the coolest ambient air available to operate on. Their efficiency must be terrible.

rmw

 

[Cooky]

There is an easier way.......

Direct a small spray of water onto the surface of the condenser, this will have the same effect as the Evaporative Cooler. To reduce the volume of water used in this process, you could also collect the water condensed on the evaporator coil and return it to the water tank.

Good luck,

Cooky

 

[PurplePenguin]

Yep they are not very efficient. Normally we leave the skirts off for this very reason. But as a practice they are suposed to be on.

Thank you everyone for your reply. I think we are going to add two box fans. One to the front and one to the rear (push & pull) to get some air flowing threw.

The sprayer on the condensers might work also I'll have to try and figure out a easy way to implement this.

Thank You All,
-Eric Peters

 

[pmover]

i do not recommend spraying water on the condensor, unless the water is of good quality (i.e. mineral free) and the atmosphere is dust free. that last thing you need is a fouled condensor.

good luck!
-pmover

 

[rmw]

I agree with Pmover, although one weekend when the supply stores were closed, and the fan motor in a condensing unit in one of units for our house, (the side we sleep in) failed, I put a yard sprinkler inside the (quanset hut shaped) condensing unit, and just let it (the water) run all weekend. It got me through until Monday AM when I could buy a motor. It was summer, and we watered the yard heavily anyway, so the water was useful too.

More to the topic, our outdoors units are rained on all the time, and rain is not exactly pure as you can note from your auto windshield after a rain.

Still, water will leave behind any solids it has in it, dissolved and undissolved as it evaporates off of the condensing unit. So, if you are going to do this, flood it, so that you only get sensible heat transfer, and not evaporation from the coil surfaces.

And, the evaporator condensate is not totally free of contaminates either. What ever is in the atmosphere flowing across the coil gets in the condensate.

rmw