Chilled Water AC

[hgerhardt]

Originally Posted by artrose

...But, with respect to small aircraft, does anyone know where one might find published load calcs for small piston aircraft cabins? I'm really curious to know how the engineering community has approached this problem. How do they handle the sensible and latent loads, solar gains, infiltration loads, and all the other variables that come into play? ....

I doubt there was much of ANY heat-load engineering involved with small airplane AC... all the manufacturers use off-the-shelf aftermarket hot-rod-type automotive components and hope for the best. None of them even approach the sophistication of what's been available in the automotive OEM world in the last 10 years.

Heinrich

[Weasel]

Originally Posted by Paddy

Weasel is right on with the math, except that he understates the btu requirement by a considerable margin (for simplicity's sake) by only considering sensible heat transfer in his example.

12,800 btu/h output should account for total BTU/H (Sensible + Latent heat transfer)

Correct me if I missed something.

Air Flow : 386 CFM measured via traverse of installed system.

Entering air conditions : 84.5 F. dry bulb temp., 65.5 F. wet bulb temp.

Leaving air conditions : 55.5 F. dry bulb temp., 54.8 F. wet bulb temp.


Total BTU/H = delta H x 4.5 x cfm

Enthalpy of entering air is 30.45
Enthalpy of leaving air is 23.07

30.45-23.07=7.38 delta H

7.38 x 4.5 x 386 = 12,819 Total BTU/H

I think ~18,000 (1.5 tons) would be about right for an RV-10 based on 1100+ hrs of flight time with this system.

My definition of "about right" would be, enough capacity that I can dress for Sunday morning worship with a full suit, hop in the RV-10 here in Mississippi, USA. middle of the summer (ambient conditions ~95 deg F. dry bulb / 70 deg F wet bulb) and not sweat anymore in the taxi/climb to altitude than I would in the Toyota driving to church.

[scard]

Originally Posted by Weasel

12,800 btu/h output should account for total BTU/H (Sensible + Latent heat transfer)

Correct me if I missed something.

Air Flow : 386 CFM measured via traverse of installed system.

Entering air conditions : 84.5 F. dry bulb temp., 65.5 F. wet bulb temp.

Leaving air conditions : 55.5 F. dry bulb temp., 54.8 F. wet bulb temp.


Total BTU/H = delta H x 4.5 x cfm

Enthalpy of entering air is 30.45
Enthalpy of leaving air is 23.07

30.45-23.07=7.38 delta H

7.38 x 4.5 x 386 = 12,819 Total BTU/H

I think ~18,000 (1.5 tons) would be about right for an RV-10 based on 1100+ hrs of flight time with this system.

My definition of "about right" would be, enough capacity that I can dress for Sunday morning worship with a full suit, hop in the RV-10 here in Mississippi, USA. middle of the summer (ambient conditions ~95 deg F. dry bulb / 70 deg F wet bulb) and not sweat anymore in the taxi/climb to altitude than I would in the Toyota driving to church.

Sounds about right! The 1.5ton equipment that Mark hung on the back of my shop IS about right. I'm sure it would fit in the RV10 baggage compartment.

[artrose]

Continued curiosity here, and I agree that your numbers would suggest the system will likely work for an average Minnesota summer day, but I wonder about the capacity required to satisfy the load in Atlanta, or Phoenix.

How, and under what actual conditions were those numbers collected? Aircraft in motion, weather, altitude, occupants? You've provided numbers for the air that was moving thru the system itself, but what was the airflow distribution for the envelope? Within reason, it's entirely possible to control short cycle air through a system and come up with a desired result. Were the curtains closed, were the outside air vents closed? I think you know where I'm going.

I could be wrong, but personally, I doubt that a ton, or even a ton and a half would satisfy the requirements of a fully loaded 10 that's been sitting on the ramp all day in the Houston summer sun. It might knock the edge off a little if you can spot cool your face, and maybe that's enough to satisfy most people? I guess it's time to start grazing some ashrae.

People just plain don't like to be too hot, and I get it. I always get a kick out of watching what they'll do, and especially the money they'll spend to fix the issue. I'm sure it's made some people very happy, but I'm still waiting to see some complete and relevant technical data provided in the advertisements by the folks who commercially produce all those little ice chest coolers that so many folks keep trying to duplicate.

[Kyle Boatright]

A cabin cover is probably your best friend in trying to ramp-cool an airplane using an undersized A/C unit. A cover would mean you're climbing into a heat soaked 100F airplane, not a 125F airplane at the get-go...

[Plummit]

Originally Posted by Kyle Boatright

A cabin cover is probably your best friend in trying to ramp-cool an airplane using an undersized A/C unit. A cover would mean you're climbing into a heat soaked 100F airplane, not a 125F airplane at the get-go...

Plus, even if your cooling unit doesn't doing much actual cooling, if it removes water (moisture) from the air it will feel much better in the humid parts of the country.

~Marc