Chilled Systems Advice/Calculations

[Rippers]

Hi,

I have a few questions regarding a chilled water system.

How can I determine the Cooling Capacity required for a room? (Data Centre) In tons.

Also, how can I determine the optimum flow of water across the evaporator in the room? is there a set water flow/fan speed calculation or graph.

The temperature difference between chilled water temperature at chiller and the 'in room' evaportator temperature? for example for a AC system its about 10K difference - is that the same with chilled water systems?


Any information would be greatly appreciated - thanks

[frank]

Hi,

I have a few questions regarding a chilled water system.

How can I determine the Cooling Capacity required for a room? (Data Centre) In tons.
You need to calculate the heat gains (both sensible and latent) of the following:
Equipment
Building fabric (solar and transmitted)
Infiltration
Ventilation
Occupancy
Lighting

1 Ton Refrigeration is equal to approximately 3.5kW

Also, how can I determine the optimum flow of water across the evaporator in the room? is there a set water flow/fan speed calculation or graph.

The flow through the evaporator will be derived from the formula Q = m c dt
Where
Q = Cooling duty (kW)
m = Mass flow of water
c = specific heat capacity of the water in kj/kg (4.19 for water)
dt = the temperature difference of the water through the evaporator (entering/leaving)

Your required air volume for the total cooling duty will be derived from the formula
Q = kW x SHR/(t1 - t2) x p
Where
Q = Air volume in m3/s
kW = your total cooling duty
SHR = sensible heat ratio (Sensible load/sensible load + latent load)
t1 - t2 = air on/air off temps of evaporator
p = density of air

The temperature difference between chilled water temperature at chiller and the 'in room' evaportator temperature? for example for a AC system its about 10K difference - is that the same with chilled water systems?
Normal chilled water flow temps for air conditioning are +6C flow, +12C return

Any information would be greatly appreciated - thanks