[TRNSYS-users] Ventilation VS cooling & heating

[David BRADLEY]

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 and gets at one of 
TRNSYS's strengths. 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 05:12, Chou Shen wrote:
> Hi
>
> Thanks to David and Matt, you messages have helped me a lot. Now I 
> know how to use type 24 & 25 to get monthly summary.
>
> At this time I have some other questions:
> 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. What's the relationships between the two methods?.
>
> 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
>
>
>
>
>
> _______________________________________________
> TRNSYS-users mailing list
> 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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