Requirement of Maintaining Indoor Relative Humidity

[Buildtech2]

Presently, I am designing a HVAC system for the factory. It is strictly required to maintain indoor relative humidity between 55 % to 60 % in raw material processing area in a factory. There is no specific requirement of maintaining space temperature in that space. The factory is located in a desert where the ambient conditions are extremely hot and humid in summer. In peak summer, the outside relative humidity reaches to the saturation lavel.

I would like to know whether a normal split unit can meet the criteria or considering dehumidifiers would be the best option.

Please share your valuable advise.

 

[EnergyProfessional]

it depends on fresh air intake, infiltration, sensible heat, actual climate.... you should hire an engineer considering you are responsible for millions of $ of material destroyed and production stopped.

What desert are you in that is both hot and humid? how is winter? your system has to work in all seasons.

Keeping 55-60% accurately 24/7/365 will require more than a split system and possibly redundancy depending on if those levels can be exceeded for periods of time.

this is stricter than a museum, what factory is that?

 

[Drazen]

no offense, your question shows that you are in beginning phases of gaining your experience.

you cannot maintain humidity in ordinary residential space with "normal" split unit, and in situation where the whole your process depends on narrow range of humidity values, not only that you would need both humidification and dehumidification, but you would need lot of study about how to place sensors, how to separate process area from other areas, solve communications with other areas.

not a something to play with especially if you cannot run away from angry client as you are in a middle of a desert.

 

[Buildtech2]

There is no requirement of fresh air in this space. Basically, its a plastic pallet manufacturing unit involving 60 % polyethylene and 40 % sand. The raw materials will be processed through an automated system to produce the product.

This factory will be built in the Arabian desert where the temperature during the day time may reaches to 50 C and during the evening, the RH may reach to the saturation level but it cannot be hot and humid and the same time.The process area is an enclosed area where there is a requirement of maintaining RH between 55 % to 60 %.

Can we achieve this task by dehumidifiers. Please advise.

 

[EnergyProfessional]

Do you really need to dehumidify in the Arabian desert??? Maybe I'm ignorant, but that sounds like a dry area.

And how does the material arrive, does it come in 55% RH railway cars? I mean does it come dryer or wetter? that also would generate or reduce humidity in the space.
and what place does not have ventilation and infiltration? Don't they open doors to bring hat material in?

you are aware by just getting colder/warmer in the space (even id you do nothing to add or subtract water), RH will change dramatically?

 

[317069]

let say you have space condition as 80F DB, 0.95% RH
if you heat this place by electrical heater (sensible heating) for example to 90F DB, the RH would be about 69%, if you heated to 95F db RH would be about 59%
check psychometric chart

 

[317069]

95% not 0.95%

 

[sprinkler1000]

Humidity control is not an easy task.
Confirm the conditions required.
Is it ok if humidity goes down below 55%?
Otherwise you will need to install humidifiers.

For sure direct expansion splits are not an option.

 

[Drazen]

split systems do not control humidity. they have partial dehumidification as a subset of dry bulb temperature control, but they are not controlled by humidity sensors.

you need good psychrometric calculation to determine your unit size, as well as all other engineering work that makes ac design and cannot be covered in tip.

you certainly need at least some fresh air to be taken into account, even if there are no operators who permanently stay in space

 

[DrRTU]

I bet you are focusing on RH in an effort to minimize condensation on the pallet mold surface. Large cavities collect condensation that cause surface imperfections. This is a big deal with consumer packaging injection molding . I have completed numerous injection molder projects. A few have we completed have had the presses in an enclosure that is temperature and humidity controlled. A good industrial de-humidifier will meet your needs. Based upon your questions, you have very limited HVAC experience. I suggest you contact

http://www.munters.com

or a comparable industrial de-humidifier company. The industrial firms are very good at equipment selection. You can also hire a local HVAC engineering who can assist with the RFP.

 

[Buildtech2]

Infact, this is the first time I came across for such a unique requirement of humidity control. I received some information about this from the specialist supplier as follows.

By using deep cooling unit with humidity sensor that adjust the controller to the required humidity limit, if the RH exceeded the set point the controller will run all the cooling stages to reduce the humidity through deep cooling then after that it will run the heaters to maintain the required room temperature. This a a special unit to cater the requirement of maintaining space relative humidity.

Hope this is the unit which I am looking for.