[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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