Source code for component.expander.expander_csteff

import numpy as np
from component.base_component import BaseComponent
from connector.mass_connector import MassConnector
from connector.work_connector import WorkConnector
import CoolProp.CoolProp as CP



class ExpanderCstEff(BaseComponent):
    """
    **Component**: Expander

    **Model**: Constant isentropic efficiency model

    **Reference**: /

    **Description**:

        This component models an expander using a constant isentropic efficiency. 
        Given the suction conditions (pressure, temperature, fluid) and the exhaust pressure,
        it calculates the exhaust specific enthalpy and exhaust temperature.
        This simple model can be used for on-design models of systems.

    **Assumptions**:

        - Steady-state operation.
        - Isentropic efficiency stays constant for all the conditions.
        - Negligible heat losses and mechanical losses except those accounted for by efficiency.


    **Connectors**:

        su (MassConnector): Mass connector for the suction side.

        ex (MassConnector): Mass connector for the exhaust side.
        
        W (WorkConnector): Work connector.


    **Parameters**:

        eta_is: Isentropic efficiency of the expander (0 < eta_is ≤ 1) [-]

    **Inputs**:

        P_su: Suction side pressure. [Pa]

        T_su: Suction side temperature. [K]
        
        m_dot: Mass flow flow rate. [kg/s]

        P_ex: Exhaust side pressure. [Pa]

        fluid: fluid. [-]

    **Ouputs**:

        h_ex: Exhaust side specific enthalpy. [J/kg]

        T_ex: Exhaust side temperature. [K]
        
        W_dot_exp (float): Mechanical power  of the expander [W]

    """

    def __init__(self):
        super().__init__()
        
        # Define mass flow connectors for suction and exhaust
        self.su = MassConnector()
        self.ex = MassConnector()  
        
        # Define work connector for mechanical work output
        self.W = WorkConnector()
        self.print_flag = 1

    def get_required_inputs(self):  # Used in check_calculablle to see if all of the required inputs are set
        # Return a list of required inputs
        return ["P_su", "T_su", "P_ex", "m_dot", "fluid"]

    def get_required_parameters(self):
        # Return a list of model parameters required for solving
        return ["eta_is"]

    def solve(self):
        # Perform checks to ensure the model can be calculated and has parameters
        self.check_calculable()
        self.check_parametrized()

        self.AS = CP.AbstractState('HEOS', self.su.fluid)


        if not (self.calculable and self.parametrized):
            self.solved = False
            print(
                "ExpanderCstEff could not be solved. It is not calculable and/or not parametrized"
            )
            return
        try:
            """EXPANDER MODEL"""
            # Calculate the outlet enthalpy based on isentropic efficiency
            
            # h_ex_is = PropsSI("H", "P", self.ex.p, "S", self.su.s, self.su.fluid) #Isentropic outlet enthalpy at exhaust pressure and suction entropy
            
            self.AS.update(CP.PSmass_INPUTS, self.ex.p, self.su.s)
            h_ex_is = self.AS.hmass()
            
            
            h_ex = self.su.h - (self.su.h - h_ex_is) * self.params["eta_is"]
            w_exp = self.su.h - h_ex # Specific work 
            
            # Set exhaust mass flow rate equal to suction (mass conserved)
            self.ex.set_m_dot(self.su.m_dot)
            W_dot_exp = self.su.m_dot * w_exp #Mechanical power output

            # Update connectors after the calculations
            self.update_connectors(h_ex, w_exp, self.ex.p, W_dot_exp)

            # Mark the model as solved if successful
            self.solved = True

        except Exception as e:
            # Handle any errors that occur during solving
            self.solved = False
            
            if self.print_flag:
                print(f"Solving problem in expander model: {e}")
                
            return

    def update_connectors(self, h_ex, w_exp, p_ex, W_dot_exp):
        """Update the connectors with the calculated values."""
        self.ex.set_fluid(self.su.fluid)
        self.ex.set_h(h_ex)
        self.ex.set_p(p_ex)
        self.ex.set_m_dot(self.su.m_dot)
        self.W.set_W_dot(W_dot_exp)

    def print_results(self):
        print("=== Expander Results ===")
        print(f"  - h_ex: {self.ex.h} [J/kg]")
        print(f"  - T_ex: {self.ex.T} [K]")
        print(f"  - W_dot_exp: {self.W.W_dot} [W]")
        print("=========================")

    def print_states_connectors(self):
        print("=== Expander Results ===")
        print("Mass connectors:")
        print(
            f"  - su: fluid={self.su.fluid}, T={self.su.T} [K], p={self.su.p} [Pa], h={self.su.h} [J/kg], s={self.su.s} [J/K.kg], m_dot={self.su.m_dot} [kg/s]"
        )
        print(
            f"  - ex: fluid={self.ex.fluid}, T={self.ex.T} [K], p={self.ex.p} [Pa], h={self.ex.h} [J/kg], s={self.ex.s} [J/K.kg], m_dot={self.ex.m_dot} [kg/s]"
        )
        print("=========================")
        print("Work connector:")
        print(f"  - W_dot_exp: {self.W.W_dot} [W]")
        print("=========================")