# -*- coding: utf-8 -*-
"""
Class FlowDevice
functions for compressor and expander output state calcultations
so far/here: only for fixed isentropic efficiencies
pumps and throttles added.
((Part of carbatpy.))
Created on Sun May 21 08:51:33 2023
@author: atakan
"""
import carbatpy as cb
import numpy as np
[docs]class FlowDevice:
"""Unified themodynamic calculations for single flow devices"""
[docs] def __init__(self, fluid, p_out, m_dot, device_type="machine", **kwargs):
"""
Calculate the output state and state changes for single flow devices
Parameters
----------
fluid : Fluid
The fluid at is entering state.
p_out : float
Output pressure in Pa.
m_dot : float
mass flow rate in kg/s.
device_type : TYPE, optional
'machine' for compressor/expander, 'pump', or 'throttle'. The default is
"machine".
**kwargs : dictionary
Optional parameters for setting the configuration and parameters
- plot info : dictionary,optional, default value is {} contains a Figure, an
Axes, a list of What shall be plotted,
a list with the colour/styles and a list with the labels must be
passed. in "what", the two numbers coincide with the fluid THERMO
order. The x-shift can be used in cycle calculations, to shift the
curves, by the value (it will be added).
The names in the dictionary are: "fig", "ax", "what","col",
"label", "x-shift".
- name : string, optional, the name of this specific device, the default is
"compressor".
- calc_type : string, optional, which method shall be used (e.g.: "const_eta",
"const_h"), default is "const_eta".
- calc_parameters : dictionary, optional, if further parameters have to be
given for the calculation. the default is None.
- verbose : Boolean, optional, the default is False.
DESCRIPTION.
the self.output dictionary contains the exit state values, and work and power.
The self.fluid is at the exit state. Check self.warning and self.warning_message.
There is also a self.print_device function for inspection. If a figure is passed
by plot_info the plot will be updated.
Returns
-------
None.
"""
self.fluid = fluid
self.p_out = p_out
self.m_dot = m_dot
self.device_type = device_type
self.plot_info = kwargs.get("plot_info", {})
self.name = kwargs.get("name", "compressor")
self.calc_type = kwargs.get("calc_type", "const_eta")
self.calc_parameters = kwargs.get("calc_parameters", None)
self.verbose = kwargs.get("verbose", False)
self.warning = 0
self.warning_message = "All o.k."
self.input = fluid.state
self.output = None
match device_type: # noeq
case "machine":
self.compressor()
case "pump":
self.pump()
case "throttle":
self.throttle()
case _:
print(f"Not implemented device: {device_type}")
[docs] def compressor(self):
"""
compressor or expander output state calculation
so far only for a constant isentropic efficiency, according to the pressure
change an expansion or compression is detected and handled.
Parameters
----------
p_out : float
output pressure.
eta_s : float
isentropic efficiency.
fluid : fprop.Fluid
entering fluid, including properties, composition, and model.
m_dot : float, optional
mass flow rate (in kg/s). Default is 1
calc_type : string, optional
how to calculate, so far, only one implemented. The default is
"const_eta".
name : string, optional
name of the device. The default is "compressor".
plot_info : dictionary, optional
if not empty a Figure, an Axes, a list of What shall be plotted,
a list with the colour/styles and a list with the labels must be
passed. in "what", the two numbers coincide with the fluid THERMO
order. The x-shift can be used in cycle calculations, to shift the
curves, by the value (it will be added).
The names in the dictionary are: "fig", "ax", "what","col",
"label", "x-shift". Default is empty.
Returns
-------
state_out : array of float
compressor output state containing [T,p,h,v,s,q].
work_specific : float
work per kg of fluid, positive for compressor; units:J/kg.
"""
state_in = self.fluid.state
expander = False
if self.fluid.pressure > self.p_out:
expander = True
if self.calc_type == "const_eta":
if self.calc_parameters["eta_s"]:
eta_s = self.calc_parameters["eta_s"]
else:
self.warning = 99
self.warning_message = f"No 'eta_s' provided, a value of 1 will be used!"
self.calc_parameters["eta_s"] = eta_s = 1.0
self.fluid.set_state(
[self.fluid.entropy, self.p_out], "SP")
diff_enthalpy_s = self.fluid.enthalpy-state_in[2]
if expander:
work_specific = diff_enthalpy_s * eta_s
else:
work_specific = diff_enthalpy_s / eta_s
state_out = self.fluid.set_state(
[state_in[2] + work_specific, self.p_out], "HP")
else:
self.warning = 100
self.warning_message = f""""The option{calc_type} is not yet implemented for
compressors"""
raise Exception(
self.warning_message)
power = self.m_dot * work_specific
#
self.output = {"state_out": state_out,
"work_specific": work_specific,
"power": power}
self.plot_temp_h_flow()
[docs] def pump(self):
"""
Calculate the exit state of a pump assuming an incompressible fluid.
Only formulated for constant isentropic efficiency
Parameters
----------
p_out : float
output pressure.
eta_s : float
isentropic efficiency.
fluid : fprop.Fluid
entering fluid, including properties, composition, and model.
m_dot : float, optional
mass flow rate (in kg/s). Default is 1
calc_type : string, optional
how to calculate, so far, only one implemented. The default is
"const_eta".
name : string, optional
name of the device. The default is "pump".
plot_info : dictionary, optional
if not empty a Figure, an Axes, a list of What shall be plotted,
a list with the colour/styles and a list with the labels must be
passed. in "what", the two numbers coincide with the fluid THERMO
order. The x-shift can be used in cycle calculations, to shift the
curves, by the value (it will be added).
The names in the dictionary are: "fig", "ax", "what","col",
"label", "x-shift". Default is empty.
Returns
-------
state_out : array of float
compressor output state containing [T,p,h,v,s,q].
work_specific : float
work per kg of fluid, positive for compressor; units:J/kg.
"""
state_in = self.input
if self.calc_type == "const_eta":
if self.calc_parameters["eta_s"]:
eta_s = self.calc_parameters["eta_s"]
else:
self.warning = 99
self.warning_message = f"No 'eta_s' provided, a value of 1 will be used!"
self.calc_parameters["eta_s"] = eta_s = 1.0
work_is = state_in[3] * (self.p_out - state_in[1])
if work_is > 0:
work_specific = work_is / eta_s
else:
work_specific = work_is * eta_s
h_out = state_in[2] + work_specific
state_out = self.fluid.set_state([h_out, self.p_out], "HP")
else:
self.warning = 130
self.warning_message = f"The option{calc_type} is not yet implemented for pumps"
raise Exception(self.warning_message)
power = self.m_dot * work_specific
self.output = {"state_out": state_out,
"work_specific": work_specific,
"power": power}
self.plot_temp_h_flow()
[docs] def throttle(self):
"""
throttle output state calculation
so far only for a constant enthalpy
Parameters
----------
p_out : float
output pressure.
fluid : fprop.Fluid
entering fluid, including properties, composition, and model.
m_dot : float, optional
mass flow rate (in kg/s). Default is 1
calc_type : string, optional
how to calculate, so far, only one implemented. The default is
"const_h".
name : string, optional
name of the device. The default is "throttle".
plot_info : dictionary, optional
if not empty a Figure, an Axes, a list of What shall be plotted,
a list with the colour/styles and a list with the labels must be
passed. in "what", the two numbers coincide with the fluid THERMO
order. The x-shift can be used in cycle calculations, to shift the
curves, by the value (it will be added).
The names in the dictionary are: "fig", "ax", "what","col",
"label", "x-shift". Default is empty.
Returns
-------
state_out : array of float
compressor output state containing [T,p,h,v,s,q].
"""
state_in = self.fluid.state
if self.calc_type == "const_h":
state_out = self.fluid.set_state([self.fluid.enthalpy,
self.p_out], "HP")
else:
raise Exception(
f"The option{self.calc_type} is not yet implemented for throttles")
self.output = {"state_out": state_out,
"work_specific": 0.0,
"power": 0.0}
self.plot_temp_h_flow()
#
return state_out
[docs] def plot_temp_h_flow(self):
"""
plotting a T-H-dot diagram for simple flows (compressor, throttle etc.)
Parameters
----------
_state_in : np.array
entering state [T,p,h,v,s,...].
_state_out : np.array
exiting state.
_m_dot : float
mass flow rate (kg/s).
_plot_info : dictionary
if not empty a Figure, an Axes, a list of What shall be plotted,
a list with the colour/styles and a list with the labels must be
passed. in "what", the two numbers coincide with the fluid THERMO
order. The x-shift can be used in cycle calculations, to shift the
curves, by the value (it will be added).
The names in the dictionary are: "fig", "ax", "what","col",
"label", "x-shift".
Returns
-------
None.
"""
if len(self.plot_info) > 0:
if self.plot_info["what"][0] == 2:
data = np.array([self.input[self.plot_info["what"][0]],
self.output["state_out"][self.plot_info["what"][0]]]) * self.m_dot \
+ self.plot_info["x-shift"][0]
self.plot_info["ax"].plot(data,
[self.input[self.plot_info["what"][1]],
self.output["state_out"][self.plot_info["what"][1]]],
self.plot_info["col"][0],
label=self.plot_info["label"][0])
else:
self.warning = 130
self.warning_message = f"Pump: plotting only implemented fot T-H_dot [2,0]. You requested{_plot_info['what']}"
print(self.warning_message)
[docs] def print_device(self):
print(f"\nDevice: {self.device_type}, {self.calc_type}")
print(f"Parameters, {self.calc_parameters}")
print(f"Input, {self.input}")
print(f"Output: {self.output}")
if self.warning:
print(f"Device: {self.warning}, {self.warning_message}")
[docs] def state_w_p(self):
if self.output:
return [*self.output.values()]
if __name__ == "__main__":
import matplotlib.pyplot as plt
[docs] FLUID = "Propane * Pentane"
comp = [.80, 0.2]
flm = cb.fprop.FluidModel(FLUID)
myFluid = cb.fprop.Fluid(flm, comp)
P_LOW = 1e5
T_IN = 310.
DT_IN_LIQ = -5
state_in_act = myFluid.set_state([T_IN, P_LOW], "TP")
P_OUT = 10e5
ETA_S = .7
M_DOT = 1e-3
fig0, ax0 = plt.subplots()
PLOT_INFO = {"fig": fig0, "ax": ax0, "what": [2, 0], "col": ["r:", "k"],
"label": ["compressor", "xx"], "x-shift": [0, 0]}
# Compressor-------------
compressor = FlowDevice(myFluid, P_OUT, M_DOT,
device_type="machine",
name="compressor",
calc_type="const_eta",
calc_parameters={"eta_s": ETA_S},
plot_info=PLOT_INFO)
# state_o, work, power_c = compressor(myFluid, P_OUT, M_DOT, ETA_S, device_type="machine",
# plot_info=PLOT_INFO)
print(myFluid.temperature, compressor.output)
# print("\nCompressor", state_in_act, "\n", state_o, "\n", state_o-state_in_act)
PLOT_INFO["col"] = ["k", ""]
PLOT_INFO["label"] = ["expander", ""]
expander = FlowDevice(myFluid, P_LOW, M_DOT,
device_type="machine",
name="expander",
calc_type="const_eta",
calc_parameters={"eta_s": ETA_S},
plot_info=PLOT_INFO)
print("\nExpander:", expander.output)
# Pump, incompressible:
state_in_p = myFluid.set_state([P_LOW, 0], "PQ")
state_in_p = myFluid.set_state([P_LOW, state_in_p[0]+DT_IN_LIQ], "PT")
PLOT_INFO["col"] = ["bv:", ""]
PLOT_INFO["label"] = ["pump", ""]
pump = FlowDevice(myFluid, P_OUT, M_DOT,
device_type="pump",
name="pump-A",
calc_type="const_eta",
calc_parameters={"eta_s": ETA_S},
plot_info=PLOT_INFO)
print(
f"pump work output: {pump.output['work_specific']:.3f} J/kg, \npump all:{pump.output}")
# throttle:
PLOT_INFO["col"] = ["go:", ""]
PLOT_INFO["label"] = ["throttle", ""]
state_in_p = myFluid.set_state([P_OUT, state_in_p[0]+DT_IN_LIQ], "PT")
throttle = FlowDevice(myFluid, P_OUT, M_DOT,
device_type="throttle",
name="throttle-A",
calc_type="const_h",
calc_parameters={},
plot_info=PLOT_INFO)
throttle.print_device()
# if you want a legend etc
ax0.legend()
ax0.set_ylabel("T/K")
ax0.set_xlabel("$\\dot h$/ kW")