[TRNSYS-users] COOLING PEAK LOAD CALCULATION

[jeannieboef]

This is generally an industry problem. Chillers are often designed  
with a PLR performane optimized at 50% of max load. This is because  
you want it to be most efficient in the area where it will be  
operating most of the time. These performance curves play a major role  
and are quite different from machine to machine. Traditionally we spec  
a max capacity and a COP, when actually we should be looking more  
closely at the part load ratios expected and those of the machine.

Sent from my iPhone

On 03.10.2012, at 19:06, David BRADLEY <d.bradley at tess-inc.com> wrote:

> Juan Francisco,
>   This is a very good question to which there are as many valid  
> responses as there are responders. My feeling is that traditional  
> methods for sizing cooling equipment lead to very over sized  
> equipment and the energy inefficiency that comes with it.  
> Traditional sizing involves a steady-state, worst-case scenario when  
> all the equipment is on, all the lights are on, and all the people  
> are in the building. Some tools also do not account for zone  
> adjacencies; they compute the worst case assuming that all zones are  
> thermally isolated from each other. There is no credit for thermal  
> mass and no credit for shading. That is obviously going to give you  
> the greatest possible cooling load. There are lots and lots of other  
> justifiable methods, some of which you mention. What I have done in  
> the past is to look at what the peak cooling load is under a number  
> of these methods (with normal building operation during an average  
> weather year, including shading, excluding shading, during an  
> "extreme" weather sequence of days, during a "design day" that  
> repeats itself. From multiple tests, you can get an idea of how  
> sensitive the peak cooling load is. You can then do some experiments  
> of limiting the available cooling power in order to see how badly  
> you miss your target cooling temperature. If the overshoot is small,  
> then under sizing the equipment a little bit will create energy  
> savings and the comfort penalty will not be great. With all that  
> information, it is then possible to do an informed sizing the  
> cooling equipment.
> Best,
>  David
>
>
> On 10/3/2012 04:44, JUAN FRANCISCO BELMONTE TOLEDO wrote:
>> Dear users.
>>
>> Any idea how to make a good cooling peak load calculation with  
>> trnsys, in a similar way as max. heat load calculation does in  
>> trnbuild?.
>>
>> I mean hipothesis about Solar radiation (What values we must  
>> consider and where we can find them), temperature (we consider a  
>> sinusoidal wave shape -as EnergyPlus does- or constant  
>> value, ...).., in which months we must simulate (for example i´ve  
>> found many building with higher values in September due to the Sun 
>>  is lower and they had a lot of windows,.. ), , tmy files should n 
>> ot be used because are average values, or yes...etc.
>>
>> thank you.
>> Regards.
>>
>> Juan Francisco Belmonte Toledo
>> Universidad de Castilla-La Mancha (Spain)
>>
>>
>> _______________________________________________
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>> TRNSYS-users at cae.wisc.edu
>> https://mailman.cae.wisc.edu/listinfo/trnsys-users
>
> -- 
> ***************************
> David BRADLEY
> Principal
> Thermal Energy Systems Specialists, LLC
> 22 North Carroll Street - suite 370
> Madison, WI  53703 USA
>
> P:+1.608.274.2577
> F:+1.608.278.1475
> d.bradley at tess-inc.com
>
> http://www.tess-inc.com
> http://www.trnsys.com
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