[Bldg-sim] A question of TRNSYS

David BRADLEY d.bradley at tess-inc.com
Mon Dec 19 10:31:36 PST 2011


Chou,
   In Type56/TRNBuild the term "VENTILATION" just means a flow of air 
whether it is hot, cold, or neutral. It isn't necessarily tied in any 
way to the HVAC system. The "HEATING" and "COOLING" types are used to 
calculate sensible loads for the space. Those types don't have anything 
to do with how that energy is delivered to the space.

   Typically, there are two kinds of simulations that I do with Type56:

Early on in a project, I need to determine the peak heating and cooling 
loads for the space and I need to get a very basic idea of how much 
energy the building will consume over the year. In order to do this, I 
use VENTILATION types to put the outdoor (fresh) air requirements into 
the zone. and I use HEATING and COOLING types to define set points. I 
allow the "system" to have unlimited power because all I really care 
about is the maximum hourly value and the annual sum. The annual sum 
gives a very rough idea of how much energy is required by the building. 
You have to do one of two things in order to get how much energy is 
required by the HVAC system: either define a simple COP for the heating 
and cooling system or use other TRNSYS models that take heating and 
cooling load as an input and return the power consumed (note, there are 
very few of these components)

The second kind of simulation is much more common in TRNSYS. In this, 
you use the VENTILATION type to deliver hot or cold air to the space and 
you use a thermostat model (such as Type108) to turn on and off 
equipment that controls the flow of air. In this case, you disable the 
HEATING and COOLING types because you don't care about loads. The 
equipment of the system (fans, pumps, heat pumps, furnaces, chillers, 
etc.) will compute their source energy requirements as a function of 
their inlet conditions and the building will simply react to the 
ventilation air that it receives.

Kind regards,
  David

On 12/18/2011 05:21, Chou Shen wrote:
> Hi everyone
>
> I began to learn TRNSYS a couple of days ago and I came across some 
> questions right now. I wonder if somebody happens to know TRNSYS 
> well.The questions are:
> 1. When Editing type 56, in the Ventilation lable, the Heating and 
> Cooling option can be set up by defining airchange rate and 
> temperature & RH of air flow; while in both the Cooling lable and 
> Heating lable, the cooling and heating option can be set up by 
> defining cooling / heating power (does that mean I need to estimate 
> the cooling / heating load before set this block up?), and the 
> setpoint temperature & RH. As a result, type 56 provides two methods 
> to define HVAC system. Do I need to set up both the labes to get it 
> work?.
>
> 2. In addition to adding the information of HVAC in type 56, do I need 
> to creat the HVAC system in to get the information of energy 
> consumption of HVAC system?
>
> Thanks!
>
> -- 
> Chou Shen
> Graduate Research Assistant
> Department of Civil, Architectural & Environmental Engineering
> Missouri University of Science and Technology
>
>
>
>
>
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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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