trnsystor

A python scripting language for TRNSYS.

Create .dck files from stratch in an object-oriented python structure. Add components, specify parameters, connect components together and more throught python code.

Installation

pip install trnsystor

Usage

Since TRNSYS 18, type proformas can be exported to XML schemas. trnsystor builds on this easy to read data structure to easily create TrnsysModels using the most popular scripting language in the data science community: Python.

From the xml file of a type proforma, simply create a TrnsysModel object by invoking the from_xml() constructor:

>>> from trnsystor import TrnsysModel
>>> xml = "tests/input_files/Type951.xml"
>>> pipe1 = TrnsysModel.from_xml(xml)

Calling pipe1 will display its Type number and Name:

>>> pipe1
Type951: Ecoflex 2-Pipe: Buried Piping System

Then, pipe1 can be used to get and set attributes such as inputs, outputs, parameters and external files. For example, to set the Number of Fluid Nodes, simply set the new value as you would change a dict value:

>>> pipe1.parameters['Number_of_Fluid_Nodes'] = 50
>>> pipe1.parameters['Number_of_Fluid_Nodes']
NNumber of Fluid Nodes; units=-; value=50
The number of nodes into which each pipe will be divided. Increasing the number of nodes will improve the accuracy but cost simulation run-time.

Since the Number of Fluid Nodes is a cycle parameter, the number of outputs is modified dynamically:

calling [pipe1.outputs` should display 116 Outputs.

The new outputs are now accessible and can also be accessed with loops:

>>> for i in range(1,50):
...    print(pipe1.outputs["Average_Fluid_Temperature_Pipe_1_{}".format(i)])
Average Fluid Temperature - Pipe 1-1; units=C; value=0.0 celsius
The average temperature of the fluid in the specified node of the first buried pipe.
... *skipping redundant lines*
Average Fluid Temperature - Pipe 1-49; units=C; value=0.0 celsius
The average temperature of the fluid in the specified node of the first buried pipe.

Connecting outputs with inputs

Connecting model outputs to other model inputs is quite straightforward and uses a simple mapping technique. For example, to map the first two ouputs of pipe1to the first two inputs of pipe2, we create a mapping of the form mapping = {0:0, 1:1}. In other words, this means that the output 0 of pipe1 is connected to the input 1 of pipe2 and the output 1 of pipe1 is connected to the output 1 of pipe2. Keep in mind that since python traditionally uses 0-based indexing, it has been decided that the same logic in this package even though TRNSYS uses 1-based indexing. The package will internally assign the 1-based index automatically when saving to file.

For convenience, the mapping can also be done using the output/input names such as mapping = {'Outlet_Air_Temperature': 'Inlet_Air_Temperature', 'Outlet_Air_Humidity_Ratio': 'Inlet_Air_Humidity_Ratio'}:

# First let's create a second pipe, by copying the first one:
pipe2 = pipe1.copy()
# Then, connect pipe1 to pipe2:
pipe1.connect_to(pipe2, mapping={0:0, 1:1})

Equations

In the TRNSYS studio, equations are components holding a list of user-defined expressions. In trnsystor a similar approach has been taken: the Equation class handles the creation of equations and the [EquationCollection` class handles the block of equations. Here's an example:

First, create a series of Equation by invoking the [from_expression` constructor. This allows you to input the equation as a string.

>>> from trnsystor import Equation
>>> equa1 = Equation.from_expression("TdbAmb = [011,001]")
>>> equa2 = Equation.from_expression("rhAmb = [011,007]")
>>> equa3 = Equation.from_expression("Tsky = [011,004]")
>>> equa4 = Equation.from_expression("vWind = [011,008]")

One can create a equation block:

>>> equa_col_1 = EquationCollection([equa1, equa2, equa3, equa4], name='test')

Changing Initial Input Values

To change the initial value of an input, simply call it by name or with it's zero-based index and set a new value. This new value will be checked against the bounds set by the proforma as for a regular input or parameter.

>>> pipe1.parameters['Number_of_Fluid_Nodes'] = 50
>>> pipe_type.initial_input_values["Inlet_Fluid_Temperature_Pipe_1"] = 70
>>> pipe_type.initial_input_values["Inlet_Fluid_Temperature_Pipe_1"].default  # or, pipe_type.initial_input_values[0]
70.0 <Unit('degC')>

Creating a Deck file

A deck file (.dck) is created by instanciating a Deck object and calling the instance method .save(). The Deck object contains the Simulation Cards and the different models (components) for the project. The following code block shows one way of creating a Deck and saving it to file.

>>> from trnsystor import Deck, ControlCards
>>> 
>>> control_card = ControlCards.debug_template(). # Specifies a predefined set of control cards. See section bellow.
>>> cdeck = Deck(name="mydeck", control_cards=control_card, author="jovyan")
>>> 
>>> list_models = []  # a list of TrnsysModel objects created earlier
>>>  
>>> deck.update_models(list_models)
>>> 
>>> deck.save("my_project.dck")

Simulation Cards

The Simulation Cards is a chuck of code that informs TRNSYS of various simulation controls such as start time end time and time-step. trnsystor implements many of those Statements with a series of Statement objects.

For instance, to create simulation cards using default values, simply call the all() constructor:

>>> from trnsystor import ControlCards
>>> cc = ControlCards.all()
>>> print(cc)
*** Control Cards
SOLVER 0 1 1          ! Solver statement    Minimum relaxation factor   Maximum relaxation factor
MAP                   ! MAP statement
NOLIST                ! NOLIST statement
NOCHECK 0             ! CHECK Statement
DFQ 1                 ! TRNSYS numerical integration solver method
SIMULATION 0 8760 1   ! Start time  End time    Time step
TOLERANCES 0.01 0.01  ! Integration Convergence
LIMITS 25 10 25       ! Max iterations  Max warnings    Trace limit
EQSOLVER 0            ! EQUATION SOLVER statement

Selecting elements of components

Inputs, Outputs, Parameters, Derivatives, SpecialCards and ExternalFiles can be accessed via their attribute in any TrnsysModel component. They are accessed via their position as for in a list. It is also possible to slice the collection to retrieved more than one element. In this case a list is returned:

>>> from trnsystor.trnsysmodel import TrnsysModel
>>> pipe = TrnsysModel.from_xml("tests/input_files/Type951.xml")
>>> pipe.inputs[0:2]  # getting the first 2 inputs
[Inlet Fluid Temperature - Pipe 1; units=C; value=15.0 °C
The temperature of the fluid flowing into the first buried horizontal pipe., Inlet Fluid Flowrate - Pipe 1; units=(kg)/(hr); value=0.0 kg/hr
The flowrate of fluid into the first buried horizontal pipe.]

Parsing string snippets

Since version 1.4, it is possible to parse string snippets of TRNSYS components. Deck.load() and Deck.loads() (similarly to json.load and json.loads for users who are familiar with json deserializing in python).

For example, one can load the following string into a Deck object:

from trnsystor import Deck
s = r"""
UNIT 3 TYPE  11 Tee Piece
*$UNIT_NAME Tee Piece
*$MODEL district\xmltypes\Type11h.xml
*$POSITION 50.0 50.0
*$LAYER Main
PARAMETERS 1
1  ! 1 Tee piece mode
INPUTS 4
0,0  ! [unconnected] Tee Piece:Temperature at inlet 1
flowRateDoubled  ! double:flowRateDoubled -> Tee Piece:Flow rate at inlet 1
0,0  ! [unconnected] Tee Piece:Temperature at inlet 2
0,0  ! [unconnected] Tee Piece:Flow rate at inlet 2
*** INITIAL INPUT VALUES
20   ! Temperature at inlet 1
100  ! Flow rate at inlet 1
20   ! Temperature at inlet 2
100  ! Flow rate at inlet 2

* EQUATIONS "double"
*
EQUATIONS 1
flowRateDoubled  =  2*[1, 2]
*$UNIT_NAME double
*$LAYER Main
*$POSITION 50.0 50.0
*$UNIT_NUMBER 2
"""
dck = Deck.loads(s, proforma_root="tests/input_files")

If the same string was in a file, it could be as easily parsed using Deck.load():

>>> from trnsystor import Deck
>>> with open("file.txt", "r") as fp:
>>>     dck = Deck.load(fp, proforma_root="tests/input_files")