Heat load

[Peter_1]

Visited today a customer (restaurant) who installed recently a new dining room.
Dimensions: +/- 12 x 20 x 3,5 m (+/- 36 x 60 x 10 ft)
Place for 250 sitting persons or 150 while dancing.
But.... when I entered, temperature was already +/- 40°C on 11 AM.
But now the clue, the roof is made of a 3 layer polycarbonate plate (with a U value of 2,1 according to the owner)
The plates are opaque, no other sun protection.

I did a quick calculation which gave me +/- 115 kW, needed air volume for this +/- 22.000 m³/u or an air change of +/- 25/hour.
This seems almost impossible..

Any suggestions or corrections?

[chemi-cool]

Hi peter,

Iv'e seen on TV its getting hot your way How many AC's do you have at home?

My suggestion - go away from there, if there is direct radiation of the sun, you can not calculate it.
Ask the owner to install a proper insulated roof and call you again.

chemi

[Abe]

At college they told me the suns energy is increased, radiated plus 80% through a glass roof.........

So Chemi is spot on...........

I would not dream of quoting with confidence any area which receives direct sun input through it

[Peter_1]

Thanks guys.
Aiyub, your avatar is gone
It's indeed very hot but I think these temperatures are rather normal for Chemi in teh Israeli dessert.
In the shadow, I measured this afternoon 35°C.
Serviced this afternoon a compressor with a condensor pressure of 28 bar, liquid was +/- 45°C to 50°C.

That's also what I told the owner already but somebody else gave an offer with a Daikin VRV of 22 kW. I estimated a heat load of 100 kW.

[Andy W]

I reckon on about 98.7 kw, I would do the job but insist on blinds for the ceiling and some knid of extract at the highest point to occassionally take away excessive hot air if a pitched roof.

[Brian_UK]

Or they could add a permanent water feature on the roof to provide heat removal !

[manishjha]

please provide easy heat load calculation format in excel sheet.

Manish Jha

[Magoo]

Rename the restaurant "sauna with foöd " speedo's and bikinis necessary.
magoo

[Makeit go Right]

Just a couple of ideas in case you are able to lower the calc cooling load:
a) At the design peak load (afternoon?) are the 150 dancers dancing already, or does that normally occur in the evening (when it is a bit cooler outside)? Ie at peak load in the afternoon, perhaps the customers are normally just seated, eating their lunch.
b) Are you able to apply some diversity to the customers? Ie is the restaurant always full to capacity at the time of day when the peak cooling load occurs (afternoon?). Maybe it would be sensible (excuse pun) to design on say 75% occupancy (185), or even lower, on the basis that when the place is maxed out (rarely) one would expect the room temp to climb a little outside the design temperature zone.

You have to discuss ways of reducing the solar heat load, of couse. Solar film can be rather effective and practical (go for the max reduction).

[Peter_1]

Original post is already from 2005