thermal loads in factories?

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Hi,

we are currently working on a factory tenement building project in China.
The building has flexible units (manufacturing, warehouse, office space),
which companies starting business in China can rent for light production and
storage.- So we don't know the exact occupancy yet and there is no user, who
can give us information of the intended function/occupancy in the building.

We are looking for realistic specific values for internal thermal loads
(process loads) for various manufacturing occupancies.- Best would be with
schedules.

Please let me know, if you have such values or if you know of relevant
studies.- I would appreciate your help!

Best Regards,
Dirk Schwede

Dr. Dirk A. Schwede's picture
Joined: 2011-10-02
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Dear Dr. Schwede,

In my opinion, there are several issues which affect your design criteria:
1) Manufacturing / process loads can easily exceed 500W / m2. It is
certainly not practical to design a cooling system for this when the actual
load may be 5W / m2!
2) The actual value is rarely known by the client and is difficult to
determine without measurement of a similar, existing installation. A rough
estimate can be obtained by dividing monthly usage by the operating hours,
but this method does not indicate peak loads, just average loads.
3) High electrical loads often affect only the cooling system and many /
most manufacturing occupancies do not provide cooling. The exception to
this is when high amounts of ventilation air are required.
4) For "light production" loads, you may still find that the cooling system
size can vary dramatically. Over-sized systems, of course, do not perform
very well for humidity control and may have shortened life due to high
cycling frequency at the low capacities.

With these in mind, I think that it is helpful for the designer to state
that "The cooling system is capable of maintaining xxC in the space on a
design day with yyyW / m2 of internal loads. The customer is responsible
for providing additional cooling capacity for internal loads higher than
this." In the US, it is common to provide a very basic heating system and
no cooling system for this type of leased / rented industrial facility.
Office areas are provided with a simple cooling system. Any additional
capacity is provided by the customer when they lease the space. This seems
like a good approach for you!

p.s., Since this is a modeling forum, it's worth mentioning that energy use
in a manufacturing facility can easily be 95% manufacturing / process loads
and 5% envelope loads. For buildings with high internal loads, it can even
be beneficial to have NO insulation, since you are trying to reject heat all
year.

James V. Dirkes II, P.E., LEED AP

James V. Dirkes II  P.E.'s picture
Joined: 2011-10-02
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Dear Mr. Dirkes,

Thank you for your answer.- Most of what you write is in line with our
experience in manufacturing projects.- If you don't know what will happen in
the building, it is difficult to decide for a load as design condition. In
our experience the client and other project participants overestimate
internal loads based on installed electric capacities, which are not, as
know we know as building performance engineers, the same as the thermal
loads. - So, we are looking for substantiated experience values to set the
yyyW/m2 value somewhat realistic and to give our client confidence that the
design will meet the demand of most of his later tenants.

"The cooling system is capable of maintaining xxC in the space on a design
day with yyyW / m2 of internal loads. The customer is responsible
for providing additional cooling capacity for internal loads higher than
this."

I have found some load profiles for industry buildings in the draft of the
GBCA (GB Council of Australia) for Industry Buildings
(http://www.gbca.org.au/green-star/rating-tools/green-star-industrial-pilot/
1761.htm), but it would be good to find more information.

Best Regards,
Dirk Schwede

Dr. Dirk A. Schwede's picture
Joined: 2011-10-02
Reputation: 0

My limited experience in this field is that factory production areas use spot cooling with fan coil units directed at the worker?s station only. Worker productivity matters. Ducted exhaust registers could be next to each heat generating machine. There might be ventilation standards depending on pollutants from the industrial process. It is not realistic or practical to offset the large heat gains from machinery with refrigeration. In areas with cold winters the whole factory must be maintained above freezing temperatures to prevent broken pipes.

Factory processes (industrial buildings) vary considerably and a standard for all industrial buildings is not practical. It is in the interest of the factory to be as efficient as possible in all aspects because they are competing with other factories manufacturing the same product. This is not the case with residential and commercial buildings and so they need energy usage standards. For such buildings, equipment loads have to be the same for baseline and proposed. The greater the equipment loads, the smaller the percentage energy savings for LEED credit. Meeting codes and standards is not affected by percentages. Credit is earned for reusing equipment heat gains to save energy with other heating tasks.

Varkie Thomas's picture
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Joined: 2011-09-30
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