Temperature reduction in shaded versus unshaded area under the Sun 7

[solidspaces]

The Steam for humidification of supply air is injected in the supply Air Duct by a standalone humidifier at the Roof that is open to the Sun.
The maximum ambient temperature for the electronic controls of this humidifier as specified by the manufacturer is 40C.
The ambient temperature at the location actually goes to above 52 degrees centigrade, therefore this humidifier must be housed in a shaded portion to bring down the temperature.
Would it be sufficient to simply enclose this humidifier in a non air conditioned but louvered steel enclosure as the means for reducing the temperature from 50 degrees to 40 degrees, or must some air conditioning be provided to bring the ambient temperature down? Would an insulation lining in the weather box (but without any air-conditioning or forced ventilation) be sufficient?

 

[IRstuff]

I'm confused by your terminology. Is the 52°C actually the "ambient" or the temperature within your box exposed to solar load? If it's actually the air temperature of the environment, then shading will not drop the temperature, but even forced ventilation will at least increase the heat flow to mitigate the problem.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[solidspaces]

The ambient temperature is the temperature outside of the box. The humidifier will be housed in a sheet metal box so that it will not be exposed directly to the Sun. The external (atmospheric) temperature outside of the box is 52 degrees celcius.
The concern is about the electronic control circuitry portion of the humdifier which should not be in more than 40 degrees temperature.
I am not sure whether putting the controls inside this metal enclosure alone will bring the outside air temperature to the required 40 degrees C or not.

 

[IRstuff]

Heat can't travel uphill, so if the atmosphere is at 52°C, the inside of the box will be higher, if there is no active cooling.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[willard3]

Basic thermodynamics....heat goes from the warmer place to the cooler place.

 

[DRWeig]

solidspaces,

They're trying to say that your box temperature cannot fall below 52°C if the temperature outside is 52°C, unless you put an air conditioner in it. Shade does not help.



Good on ya,

Goober Dave

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[solidspaces]

When the ambient temperature is 52 Degrees C in unshaded atmosphere, what would be the approximate temperature at sea level, still air conditions under a shade? How can this be calculated or is this purely empirical?

 

[IRstuff]

Duh??? AMBIENT means AMBIENT, meaning EVERYWHERE; shade or otherwise.

Is this for school?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[willard3]

Definition of AMBIENT

: existing or present on all sides : encompassing

 

[SAK9]

The Carrier Design Manual reckons it is 5F cooler in the shade as compared to the ambient.The shade in this instance refers to the unconditioned space in a proper building and therefore will not apply to the shade created by a "metal enclosure".

I had to deal with a similar issue with variable speed drives on the roof exposed to the sun that were tripping out on high temperature days.Shielding with scraps of ducwork were tried and did not work.We ended up relocating them indoor.

Though the metal enclosure may cut out the radiant component for a while,it will get heated up above ambient in a while and will start radiating to the protected body as well probably worsening your situation.Maybe a black umbrella might work!

 

[IRstuff]

Let's not confuse solar loading with AIR temperature. Yes, YOU will be cooler in the shade than if the sun was beating down on you, but the air temperature does not change.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[DRWeig]

I'll volunteer to confuse the issue some more: if it can catch radiation from the sun in the day, it can radiate to the cold night sky as well, and the box can dip below ambient when it's dark and starry outside, IF the internal heat generation is not enough to overcome the external radiation.

Good basic heat tranfer lessons to be learned. I suggest that solidspaces study them thoroughly.



Good on ya,

Goober Dave

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[IRstuff]

And not just "dip below," it can actually freeze

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[ChasBean1]

Although this may further compound the issue, you won’t need the humidification equipment to operate unless it’s winter, so your high ambient temperature limits might lose importance if the devices with the temperature limitations do not need to operate.

 

[solidspaces]

ChasBean 1 is correct in the general case, but we have low relative humidity (about 15-30%) all year round. So our Building management system monitors humidity and brings it in service regardless of the calendar season.

 

[IRstuff]

"Would it be sufficient to simply enclose this humidifier in a non air conditioned but louvered steel enclosure as the means for reducing the temperature from 50 degrees to 40 degrees, or must some air conditioning be provided to bring the ambient temperature down? Would an insulation lining in the weather box (but without any air-conditioning or forced ventilation) be sufficient?
"
OK, try again

> No. Shade will help keep the box temperature from EXCEEDING 52°C
> Yes. You have air at 52°C. You need AC to get down to 40°C
> That will make it infinitely worse. The objective, to reiterate, is to reject heat from the electronics into an ambient of no greater than 40°C. Insulation increases the thermal resistance.



TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[tys90]

What are the inside temperature and humidity requirements? Unless they are both higher than normal, you shouldn't have to use the humidifier until outside temp is less than 98F, worst case. Why can't the humidifier go inside?

 

[317069]

- Is this an exisiting system or in design stage?
- did you talk with manufucturer?
- use two termometers, one under the sun the other in sahded area and check the difference
- you said your box will be louvered, will you use a fan too or just two louvers?
- if maufucturer limit is 40C then you may be have choosen the wrong product,this product may be for in house use only.

 

[solidspaces]

The responses from IR STUFF, TYS90 AND 317069 and the others earlier on, provided the needed insights to address the problem at hand.
Thanks a lot to all who responded

 

[marcoh]

Should note that official temperatures are shaded temperatures. Unshaded temperature will be higher due to direct radiation (ie solar radiation and from surroundings).

Therefore proving a simple shading structure may not reduce the temperature below the ambient temperature of 52 degrees but will prevent the equipment from heating up above 52 degrees which is what would happen if is was not shaded and located in direct sunlight.