HVAC solution and calculation emergency help needed 1

[jakaodrz]

Hi and greetings to all of You.
As e new one I have a serious problem:

1. I have 2 systems to compare: The one is 100% fresh air (input), with build in coil recovery energy loop on exit side. The second is a system with 20% of fresh air with no energy recovery device on it.

How to make a decision which one is a better (this HVAC system are two different solutions for our pharmaceutical factory with class 100.000).
I've searched thru this forum, and find something, but as a new, i did not understand your units (american vs euro), and the way you calculate the difference between this systems.
The only thing I have to do is to calculate (formulas and suggestions)energy needed for heating (cooling) input air, to make a constant temperature of app. 22 degrees centigrades, and RH of 50%.

Maximum summer and winter temperatures are -20 and +40 degrees centigrades.

Also I've DL PSYCHROMETRIC ANALYZER, and tried to calculate it, but it do not include the energy of energy loop.
I have to mention that this is only for this time and no need for further comparement than this one.

Any help is a very big help to me.

Thanx in advance.

 

[jakaodrz]

To Quark:

OK, I did some calc:

The values of H1-H2-H3 are taken from Psychrometric analyzer, for altitude of 423 m. (If they are wrong, correct me).
Input:
H1: T=40C/50%RH, equal of 104.0048 kJ/kg
H2: T=25C/50%RH, equal of 51.6318 kJ/kg
H3: T=22C/40%RH, equal of 39.6764 kJ/kg

100% fresh air:

4.5x(104.0048-39.6754)x630=182385.18 (kJ*m3)/(kg*h)

90% recirc air:

4.5x(51.6318-39.6764)x900=48419,37 (kJ*m3)/(kg*h)


Is is the correct value above ? What gives (kJ*m3)/(kg*h)precisely ?

The 2nd:

What happens if I'm heating the air ?

I got negative value for 100% fresh air:

Outdoor temperature is: -10C/35%RH

4.5x(-8.6005-39.6764)x630=-1368650.1 (or maybe I have to to opposite process to substract from 39.6764 value of 8.6005)?


Anyway, I still can't find the "catch" in solution of 100% fresh air. simply, knowing people that are working on their solution, there must be some trick in their solution of HVAC.

Greets,

 

[quark]

The other values seem to be ok but not the H3, for the coil outlet condition should essentially be saturated(or near to saturation). That means the RH should be nearer to 100.

Secondly, 22C coil outlet temperature is quite high even for comfortable cooling application. If your area deals with any of liquid injectables, granulation, coating or capsulation areas, the moisture load will be a bit high.

My equations can't be used with metric units. However, you can download an excellent unit conversion program 'Uconeer' written by Katmar, a fellow member of eng-tips, from the following link.

http://www.katmarsoftware.com/uconeer.htm

Yu should also consider heat gain in return ducting when you deal with recirculatory system. But as far as the primary comparision is concerned, the procedure is ok. The whole idea is to show that fresh air systems always prove you costly.

Regards,

 

[jakaodrz]

TO: Quark

Yes, You are right, I've made mistake in calcs about the output temp of air at coil exit. The real values are: 15C/97%RH or 19.3217 BTU/lb.

So the calcs are:

100% fresh air:
4.5*(47.1503-19.3217)*370.8=46434.802

90% recirc air:
4.5*(22.1977-19.3217)*529.72=6855.636

This means system with 100% fresh air is more expensive then with 90% recirc.

QUOTED:
"Yu should also consider heat gain in return ducting when you deal with recirculatory system. But as far as the primary comparision is concerned, the procedure is ok. The whole idea is to show that fresh air systems always prove you costly"

Ok, can we do these considerations too ? How much it changes the calcs vs. the one we have done here (above?) Is it ok to do calcs with choosen H2 values as an air with 30C/60%RH, there should be some additional calcs, independent from those above ? I think this can be done too, because, we have to proove that even using such concentrated output air, and power needed for conditioning is still cheaper, than using 100% fresh air with heat recovery.

How to consider (course of opinion-thinking)the factors such as using outdoor air conditions in some periods od the year for saving energy (ex. similar condition of outdoor air 15C/50-55%RH like the air needed for input in rooms, for making adequate room conditions). In one word: Any possibilities for saving power (much more, or simply more)if we have conditions of out air similar to needed conditioned air, in way of not using chillers or additional sources of heating/cooling devices?

Thanx for your link. I'd rather die then finding such this wonderfull program. God bless you

Greets,