Chilled Beam

[TeeAr]

Hi Everybody,
New to the forum, hope somebody to help me.

I am dealing with chilled beams and I would be grateful if someone could help me .
I have read past threads concerning this topic, I have visited suggested links.
Nevertheless, I cannot find any indication of how to determine the capacity of a chilled beam. Or, if you consider a reference table, how the value is got when air, water flow and coil are known.
Basically, I see these applications as a common water coil, but I cannot find any reference to confirm it.
I have made some hypothesis, but my result is far from what is presented in catalog.
Please, has anybody tried to make this sizing or knows some references for the chilled beam calculation ?
Many thanks

 

[EnergyProfessional]

you mean the heating/cooling capacity?
you should consult the specific manufacturer to give you the tables.

they likely tell you the minimum flowrate (important to maintain induction) and based on air temp delivered and chilled water temp you can see the cooling capacity. some offer heating too. should be similar to a heating coil in a VAV box.

 

[willard3]

Read about induction units....chilled beam is the same thing with a new name.

 

[ChrisConley]

I've dealt with TWA Panels when selecting beams. They have a selection spreadsheet (with optomization) that allows you to select beams based on size, airflow, water flow, temperatures, etc.

http://www.twapanels.ca

 

[bigAlittlee]

I'm not sure if you are implying that you would like to calculate the capacity theoretically and find water and air side Nusselt numbers or what. If that's what you're going for good luck with that.

If you are looking for a good source for typical data I would recommend the Trox chilled beam design guide.

http://www.troxusa.com/usa/service/...ystems/leaflets/Chilled_Beam_Design_Guide.pdf

Your parameters are going to be:

-Differential of entering chilled water temperature from the room air temperature.
-Differential of primary air temperature and room temperature.
-NOZZLE TYPE! This defines how much room air is induced by your primary air and is critical for balancing the sensible and latent loads.
-Flow rate per linear foot.

Using these you can find the capacity in their tables. That should be easy but designing a chilled beam system is not that simple. It will be a very iterative process and depends heavily on the occupancy and weather. For my first chilled beam system design I used the Trox design guide data to make an Excel sheet with 22 columns of input and output values that applied to each space. Some of those items were excessive but the balancing act that accompanies the disconnection of latent and sensible loads, with different load ratios in each space, takes some attention. When you start playing with air handling units and dew points that will let you match 62.1 ventilation (assuming 100% OA) while satisfying your latent load, things get really fun because with a large building and variety of spaces it won't be consistent, forcing overventilation in a lot of spaces. That's just to do the loads, I couldn't even help you when it comes to modeling the whole system (correctly, as in accounting for the controls and different nozzle types in every space).

What I am basically trying to say, is that in a given system even if all the beams are the same, their capacities will vary depending on how much primary air is supplied, the condition of that primary air, the temperature of the water supplied, the amount of water supplied, and the NOZZLE TYPE.

Generally I think of a chilled beam configuration as being supplied with the minimum ASHRAE 62.1 ventilation air conditioned to a very low dew point with a heat pipe, low temp coil, and desiccant wheel configuration (maybe +30% for that one LEED credit), with demand control CO2 sensors controlling the airflow quantity, and thermostats controling the waterflow quantity. That isn't the only option though, and if it works better to recirculate you can do that too.

If you keep primary air at constant flow and condition and water flow at constant flow and temperature, then along with knowing the NOZZLE TYPE, you will know the amount of air induced, and the corresponding sensible and latent loads that will be satisfied (from the tables).

I would assume most manufacturers have similar data.