I don't know of specific requirements in your country.
That being said, is your AHU providing 100% of the air going through the sterile air filters above the operating table?
Common practice over here is that the air over the filters is 90% recirculated air and only 10% fresh outside air.
If...
When there is a large temperature difference between inside and outside of the room, you will need quite a bit of insulation.
And you have to make sure there are no conducting elements between the inside and the outside because this will cause condensation on the outside. Or even condensation...
ROBATHERM have AHU's that fire gas or oil, but NOT in the airstream.
And it might be energetically more efficient to make heating/ventilation and moisture removal two separate processes.
In addition: If by "direct fired" you mean burning gas directly in the airstream that goes into the space, then you have to take into account that burning gas creates water vapour...
"with a minimum 40% outside air" : you mean 40% of the air needed to heat the space?
The 60% that is recirculated will of course not remove the moisture created from the space.
Based on required inside Absolute Humidity and worst case OA Absolute Humidity you can calculate what volume of...
So, what we are really doing here is cooling 150 m3 of air...
m.c.dT = Volume.density.c.dT = 150 x 1.2 x 1008 x 7.222 = 1,310,359 Joule
13.92 kW = 13,920 Joule/s
1,310,359 / 13,920 = 94 seconds to cool 150 m3 of air 7.222 degrees C
So, your value of 23 seconds is closer to the real answer...
My personal rule of thumb is maximum one air change per hour for leakage when a room is at the correct pressure. If there is more leakage, then construction of the room needs to be checked - cracks filled, door seals adjusted etc.
If rooms with over-pressure leak too much to their surroundings...
Condensation on the pipes carrying the cold water might be an issue.
Therefore dehumidifying the ventilation air might me required. Or dehumidifying the air inside the room itself.
AHU's will be built to the exact specification you need.
AHU's are not a standard product.
Therefore, every component of the AHU is engineered to meet the requirements for temperatures, filters, pressures and sound attenuation.
It is not energy saving that is the main reason, it is the comfort of the people.
In winter, higher than 21 degrees is not needed. And, depending on the outdoor climate you are in, 24 degrees inside in summer might also be too low.
Cold winter air is very dry. Bringing this into the building...
People dress differently in summer and winter.
When it is cold outside (winter) people will wear warmer clothing which they will also wear when going indoors. Therefore, 21 degrees inside is more than enough.
In summer, people dress lightly and 24 degrees is considered comfortable.
Hasni2,
"Just little curious to know about adding humidifiers on the supply air way, if someone could clarify the moist air properties on its route from cooling coils upto the room with moisture being added on the way !!"
When the air after the cooling coil is at 90-95% RH, you can not add a...
And then there's the large difference in pressure loss across the filters in the AHU when they are clean or dirty.
(Assuming you have a return air AHU with filters and some form of heat recovery).
Anyway, what I'm trying to say is that it is worth thinking about the scale of things and seeing...
Maybe you can do a "guesstimate" by guessing that the surface temperature for the light-coloured material might be around 40 degrees C whereas a dark roofingmaterial might get up to 60 degrees C.
Using these temperatures for a transmission heatgain calculation should give you some idea of the...
