Re: [TRNSYS-users] COOLING PEAK LOAD CALCULATION

[jeannieboef <jeannieboef@gmail.com>]

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@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 not be used because are average values, or yes...etc.

 

thank you.

Regards.

 

Juan Francisco Belmonte Toledo

Universidad de Castilla-La Mancha (Spain)

_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@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@tess-inc.com

http://www.tess-inc.com
http://www.trnsys.com

_______________________________________________
TRNSYS-users mailing list
TRNSYS-users@cae.wisc.edu
https://mailman.cae.wisc.edu/listinfo/trnsys-users