Evaporative cooler for indoor space - air psychrometric

Question

Evaporative cooler for indoor space - air psychrometric

MEP.Learner (Mechanical)

(OP)

18 Sep 23 01:23

Hi Engineers,

I have questions for evaporative cooler application to different indoor spaces (like factories, hospital, wards, offices, public spaces). We are looking to deploy a more sustainable way to cool indoor space (maybe due to certain area with less budget to install aircon, lower operation cost, etc).
I am looking at tropical countries for this evaporative coolers installation.

Anyway, my questions are:
1. how much moisture is too much?
Is it absolute moisture (g/kg) that matters or RH%?

2. How does the air psychrometric work for evaporative cooling?
There is air psychrometric reference / design guide for cooling / air conditioning.

3. how does clothes dry / absorbing moisture work?
is it the RH / partial vapor pressure (which is related to RH%) that matters?
Last thing we want is the clothes / bed sheet / blanket absorbing moisture from evaportive cooler and become a humidity issue.

4. How does mould grow?
is it by RH% or absolute moisture?

Thanks.

LittleInch (Petroleum) · Answer 1 · 2023-09-18 07:27:48

Have you done any research yourself?

RH is key and 40 to 60 % is generally regarded as "comfortable".

Above 70% mould starts to become an issue.

Evaporative coolers need constant air flow to avoid excessive humidity and are generally unsuited to indoor locations.

Tropical countries are generally naturally higher humidity and hence evaporative coolers don't work well or at all in those locations when the air coming out is sent into buildings.

Maybe read this first. https://www.pdhonline.com/courses/m231/m231content...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

nuuvox000 (Mechanical) · Answer 2 · 2023-09-19 22:06:25

This may help: https://www.oxy-com.com/what-is-evaporative-coolin...

MEP.Learner (Mechanical) · Answer 3 · 2023-09-20 01:33:29

Hi @LittleInch and @nuuvox000
Thanks for the reply.
the pdhonline is good.
I have spent fair bit of time looking thru youtube / online design guide / pdf studies on evaporative cooler. The system i will be using is IDEC+DEC.

The area i am operating is south east asia, which the ambient RH is easily 70+%.
On the question when mould is a concern in A/C space, i do remember it is generally taken that anything higher than 70% RH that mould can pull the moisture from air for it to grow. But when i search more on this, i couldnt find more exact answer. Like the SEA region where outdoor is 33 deg C, 70+% RH, why doesn't mould grow everywhere?
So what are the detail that mould actually grow.

nuuvox000 (Mechanical) · Answer 4 · 2023-09-20 14:09:05

Mold usually grows when water gets in walls. Usually if the walls are cold then the water will condense out of the air inside the walls. I'm not super familiar with it but look up vapor drive analysis.
Also: https://iibec.org/wp-content/uploads/2017-04-ricke...

MedicineEng (Industrial) · Answer 5 · 2023-09-21 04:04:22

Another factor for mold growth is air circulation.
If you have good air circulation, then mold will grom slower.

botom line, evaporative cooling in indoors is already challenging to say the least.
In a tropical setting is a definitive no no.

Now, if you live in the desert or in a hot and dry area, then it will work.

LittleInch (Petroleum) · Answer 6 · 2023-09-21 10:37:44

The IDEC DEC systems stil don't work effectively when you're starting with air at 70% RH.

And you might up with skighky cooler air, but it's still at 90%RH.

That's uncomfortable and you need to vent all the air you put in back out again.

You can use it to blow cooler air through your chiller condenser....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Compositepro (Chemical) · Answer 7 · 2023-09-21 22:10:53

Technically mold growth is not affected by "air circulation". It is affected by humidity, which is affected by outside air ventilation. Evaporative cooling is a once through process. You do not want to recirculate humid air. It will not cool any further.

trashcanman (Mechanical) · Answer 8 · 2023-10-03 19:10:39

Evaporative systems work only in dry climates, like Nevada, Saudi Arabia, Iraq, Death Valley, etc. Trying it in SE Asia is a joke. An evaporative system CANNOT, REPEAT CANNOT REDUCE THE AMBIENT AIR RELATIVE HUMIDITY. By definition, it ADDS to the RH.
I think you need to hire a competent HVAC Engineer.

MEP.Learner (Mechanical) · Answer 9 · 2023-10-06 01:36:08

@trashcanman,
thanks for the reply.
Yes, we do know about the general guide that ID/DEC doesn't work in SEA.
However from the trial setup shows that the feedback on thermal comfort is actually positive.
At the moment, i am researching the problems that can arise from the elevated humidity levels.

The indoor space we are looking at are like worker dormitary, workshop, etc.
Generally space those cannot be aircon (due to budget / operating cost), etc.

SAK9 (Mechanical) · Answer 10 · 2023-10-06 11:14:03

As trashcanman said these coolers will not work in SEA.I have worked and travelled throughout SEA and I have never seen them in use anywhere. Do not fool yourself and the poor workers who need to live in this horrible environment!

LittleInch (Petroleum) · Answer 11 · 2023-10-06 11:18:57

Workshop maybe as you can easily exhaust all this humid air and pull in fresh air, but a dormitory!

I think you can A/C a dormitory.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

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Evaporative cooler for indoor space - air psychrometric