Dear Jeff,
thanks for your answer and for the screen capture
of the system but I have some doubt concerning the use of the type 504 (or
505) to model the air to water heat pump. The type is designed to model a
water to air heat pump so I can't use it to provide the required heating
or cooling to the flow stream! How can I to resolve the problem? I
think that isn't possible that in standard TRNSYS or in TESS libraries there
isn't a similar type! Maybe it's the type 172 or 201 "Electric compression
Heat Pump (M. Hornberger or M. Wetter, T. Afijei)" available for sale in http://sel.me.wisc.edu/trnsys/fr_index.html?/trnsys/components/componen.htm...
It's exact?
With kindest regards,
Maurizio Sorce Department of Energy and Environmental Research
(DREAM) Università degli Studi di Palermo
----- Original Message -----
Sent: Monday, March 22, 2004 8:17
PM
Subject: Re: Heat pumps in TRNSYS
At 12:16 PM 3/22/2004 +0000, Maurizio Sorce wrote:
for my my
year-long simulation I need to use a air-water heat pump, whose role is to
supply temperature (at 50 and 7°C in winter/summery operation) and flowrate
to the type 673 fan coil. I have Standard TRNSYS and TESS Libraries but I
don't understand which is the type that models the heat pump.
Maurizio,
As we have discussed, the simple fan
coil model you are using is probably not the best model for your
studies. The Type 673 fan coil model that you are using takes the KNOWN
building sensible and latent loads and imposes them on the fluid flow stream
that is passing through the fan coil unit. This flow stream could then
be directed to a heat pump model to provide the required heating or cooling to
the flow stream. This simplistic approach completely eliminates the
dynamic interaction between the zone, the fan coil, and the heat pump. A
much better approach would be to use a fan coil model that calculates the air
outlet conditions from the fan coil based on the water and air entering
conditions and then directs this air stream to the building model (which
changes the zone temperatures and an iterative process is commenced). In
this way, you get the interaction between the components that best emulates
what happens in real life.
To study the system in this way requires the
following steps:
1) Eliminate the simple cooling and heating devices in
the zone model (Type 56) and create ventilation inputs into the zone. 2)
Use a fan coil model that takes the inlet air conditions, inlet water
conditions, and fan coil specifics (catalog data, capacities etc.) and
calculates the outlet air and water temperatures and connect this model to the
zone and water stream components. We have such a model that we will
release with version two of the TESS libraries and all of our models are fully
documented. Early versions had the documentation encased in the IISiBat
proforma of the model and latter versions have an additional technical
document (assumptions, algorithms, references etc.) for users looking for a
little more detailed information. 3) Retrieve catalog data for an
air-to-water heat pump from the internet, or a sales rep., that provides the
capacity (sens and lat) and power as a function of the entering water and air
conditions. Then you can use the heat pump models in the TESS libraries
that you have purchased (Types 504 and 505 in the current version).
These models require files of performance that you can easily create from the
catalog data you just obtained. 4) Connect the remaining components
(thermostat, pump, pipes, ducts etc) to reflect the system that you are
studying and investigate the system.
I have attached a screen capture
of a simple system, similar to what you have described, modeled in TRNSYS for
your reference.
1) Maybe type 655 can simulate winter operation but
I'm searching for a type that I can use to cool and heat the fluid and not
only cool it. Type 655 is an air cooled chiller and is
not intended for heating applications.
2) If I
use type 655 I must supply 2 two external data files. The first data file
contains ratios of the capacity to the rated capacity and the COP to the
rated COP as functions of the chilled water set point temperature and the
ambient temperature; the second file must contain the fraction of full-load
power as a function of the part-load ratio on the machine. But for my heat
pump I have only the data presented in the catalogue (ie rated cooling
capacity, rated heating capacity, COP, total fluid flow rate... see in
attachment)!! There are many companies that provide the
information required for the air cooled chiller model - or you can simply use
the default curves provided in the sample data files that came with your
purchase.
With kindest regards,
Jeff
Thornton TESS
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