[TRNSYS-users] why the cooling load is so small and much smaller than the heating load

[David BRADLEY]

Zhou,
   I don't think you've done anything incorrect in your project. I think 
there are a few reasons for your low cooling load.

1. there is only one window in the building allowing solar heat gains 
into the space.
2. the internal gains (equipment, lighting) are very small (50W in the 
sun and back zones). This means that the building internal temperature 
isn't being driven up by much.
3. the floor slab is uninsulated and coupled directly to a constant 10C 
temperature all year round (this provides some free cooling).
4. all three zones have 0.5 airchanges per hour of infiltration (ambient 
air). While that is not unreasonable, infiltration typically increases 
heating loads and decreases cooling loads.

I would also recommend raising the zone thermal capacitance values to 5 
times their default. The default accounts only for the thermal 
capacitance of the air in the zone. It neglects the capacitance of the 
furnishings. I would also recommend setting the humidity capacitance 
multiplier to 10 instead of 1; a value of 1 indicates that only the air 
in the zone has any ability to absorb and desorb moisture. These will 
have secondary effects on your cooling load.

Regards,
  David


On 11/8/2010 06:56, jw_zhou wrote:
> dear sir,
> I send files of  "***.tpf" and "***.bui" to you for your help to find 
> out why the sensible cooling energy demand is so small and much 
> smaller than sensible heating energy demand. For you quick understand 
> of my projrct, some brief information about the project are listed below:
> 1. there are three zone from south to north, the sunzone is face to 
> south, the backzone to north, and the midzone, which is modeled as the 
> hall way, is adjacent to both the sunzone and backzone. all of the 
> zones have same size and 48m^2.
> 2. I want to get the building load of the sunzone, so I added 
> an internal heating(set points=20?) and cooling(set points=27?),  
> also add a ventilation type--newwind which air chang rate is 0.6 per 
> hour.
> 3. the main outputs of sunzone are NTYPE1, 10,30, 31 which are zone 
> air temperarue(?), latent energy demand(W/m^2), sensible cooling 
> energy(W/m^2), sensible heating energy(W/m^2).
> 4. According to results, there are two unreasonable points: heating 
> load is much larger the cooling load;  the latent energy damand had 
> taken a large part of whole cooling load. would I omited something or 
> these results are right?
> hope for your reply, and thank you very much.
> 2010-11-08
> ------------------------------------------------------------------------
> jw_zhou
>
>
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-- 
***************************
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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