Printable View
Room Size: 168 m3, Air change/Hr: 20, CFM: 1975, Outside Temp:104 F, Room Required temp: 71 F, Outside RH: 85%, Expected RH: 22%, system required 20 % fresh air and 80 % return air.
So, Sensible Heat: 1.085X1975X(104-71)/12000 = 5.87 Ton
& Latent Heat: 4.840X1975X (139 - 31.43)/12000 = 86 Ton,
if I overlook other heating load, then total load = 91.87 Ton, but I don't think so, its too much for 168 m3 room, what was my problem with the calculation? Please help?
Try electrcal loading from lights, computers, fans, and people loadings. Heat gain from solar effect on windows. heat gain from structure loads, ceilings walls and floors.
Your problem is that you are probably calculating whole air as fresh air, not mixed!
You need to handle only 20% of total air flow as fresh air.
.....................
http://i55.tinypic.com/331impc.jpg
http://i54.tinypic.com/b5jm2v.jpg
Thanks to you, you always help me lot.
Can you please provide me the software or the source of the software or how can I calculate it my self?
Waiting for your kind replay.
Windows Psychrometrics Calculator £28.00
http://www.marcobrien.org.uk/
ok I will do it.................Quote:
Originally Posted by nike123
Some problem with the calculation......
1. Supply air dry and wet bulb temperature is not correct our expected temperature 22 Deg C and 22% RH
That is exactly what I entered as return air.
Return air is actual state of air in room.
Supply air is mixing with air alredy in room.
Check your home air-conditioner suply air and room air.
But this is not a total summary. Where is my 20% fresh air load and at the starting time room temperature and humidity are same as outside so how can I summaries total scenario?Its a pharmaceuticals plant......
My point is (Room Size: 168 m3, Air change/Hr: 20, CFM: 1975, Outside Temp:104 F, Room Required temp: 71 F, Outside RH: 85%, Expected Room RH: 22%, system required 20 % fresh air and 80 % return air.) if I want to calculate from the beginning what will be the steps?
1. Sensible Heat: cfmX1.085X (Tout-Tin)/12000 = (0.00 Ton)
2. Latent Heat: cfmX0.69143X(G1-G2)/12000 = (0.00 Ton)
Then add lighting, man, machine, sunlight, .........etc load, but problem is at normal condition and initial condition load is not safe so how can I summarized total thing that can help me to predict system total load and buy a AHU.
20% fresh air is in the calculation.Quote:
Originally Posted by Bashir01219
What is not in calculation:
-Latent load from people
-Heat gain from the supply air fan
-Heat gain from the return air fan
-Heat gain from supply air ductwork portion in unconditioned space
- Heat gain from return air ductwork in unconditioned space
- Infiltration (sensible & latent) if any
- Heat gain from lights
- Heat gain from plant equipment
- Heat gain from walls, floors, ceilings and windows
etc...
Also, you need to establish what is required time frame to lower your temperature from starting conditions.
Than , you could calculate aditional cappacity needed for that task.
In the chart Mixed Air Return, for Supply Air, you take DB:12.3, WB: 11.3, RH:95 why? Is it not what for the room design? RH: 22, Temp.: 22 Deg C.