add refrigeration agents for CO2 capture

biosteam/_heat_utility.py

@@ -298,6 +298,12 @@ class HeatUtility:
  #: Used for BioSTEAM refrigeration utility.
  thermo_propane: Thermo = Thermo(['Propane'])
 
+ #: Used for BioSTEAM refrigeration utility.
+ thermo_propylene: Thermo = Thermo(['Propylene'])
+
+ #: Used for BioSTEAM refrigeration utility.
+ thermo_ethylene: Thermo = Thermo(['Ethylene'])
+
  #: Characterization factor data (value and units) by agent ID and impact key.
  characterization_factors: dict[tuple[str, str], tuple[float, AbsoluteUnitsOfMeasure]] = {}
 
@@ -573,10 +579,30 @@ def default_cooling_agents(cls):
  heat_transfer_price = 13.17e-6,
  phase='l',
  )
+ propylene = UtilityAgent(
+ 'propane',
+ Propylene=1,
+ thermo=cls.thermo_propylene,
+ T=227.59,
+ P=cls.thermo_propylene.chemicals.Propylene.Psat(227.59),
+ heat_transfer_price = 16.54e-6, # Lever rule with -30 and -90 F prices
+ phase='l',
+ )
+ ethylene = UtilityAgent(
+ 'ethylene',
+ Ethylene=1,
+ thermo=cls.thermo_ethylene,
+ T=172.04,
+ P=cls.thermo_ethylene.chemicals.Ethylene.Psat(172.04),
+ heat_transfer_price = 33.2e-06,
+ phase='l',
+ )
  cls.cooling_agents = [cooling_water, 
  chilled_water, 
  chilled_brine,
- propane]
+ propane,
+ propylene,
+ ethylene]
 
  def copy(self) -> HeatUtility:
  hu = HeatUtility()