Heat Exchanger - Nouman090/ThermoSim GitHub Wiki

A heat exchanger transfers thermal energy between two fluid streams (hot and cold sides). The package supports multiple HEX types with pinch-point constraints, effectiveness methods, and detailed temperature profile analysis.

HEX Types

Type	Description
`double_pipe`	Counter-flow or parallel-flow with both sides fully modeled
`Condenser`	Hot side condenses (phase change); cold side may be single-phase
`Evaporator`	Cold side evaporates (phase change); hot side may be single-phase
`SimpleHEX`	Single-side only (external heat source/sink); no pinch analysis

Physics

Energy balance:

Q = ṁ_hot × (H_hot,in - H_hot,out) = ṁ_cold × (H_cold,out - H_cold,in)

Pinch-point constraint (PPT):

ΔT_min ≥ PPT   (minimum temperature difference)

UA and LMTD:

Q = UA × LMTD
LMTD = (ΔT₁ - ΔT₂) / ln(ΔT₁ / ΔT₂)

Exergy destruction:

Ex_D = (Ex_hot,in + Ex_cold,in) - (Ex_hot,out + Ex_cold,out)

Syntax

HeatExchanger(Model, ID, PPT, HEX_type, HeatAdded,
              Hot_In_state, Hot_Out_state,
              Cold_In_state, Cold_Out_state,
              UA=None, effectiveness=None, Q=None,
              div_N=200, PPT_graph=False, Calculate=False)

Parameter	Type	Default	Description
`Model`	ThermodynamicModel	—	The model object
`ID`	str	—	Unique component name
`PPT`	float	—	Pinch-point temperature (K)
`HEX_type`	str	—	`'double_pipe'`, `'Condenser'`, `'Evaporator'`, `'SimpleHEX'`
`HeatAdded`	bool/None	—	`True` = adds heat to cycle, `False` = rejects heat, `None` = internal
`Hot_In_state`	str	—	Hot inlet state point name
`Hot_Out_state`	str	—	Hot outlet state point name
`Cold_In_state`	str	—	Cold inlet state point name
`Cold_Out_state`	str	—	Cold outlet state point name
`UA`	float	None	Overall heat transfer coefficient × Area [W/K]
`effectiveness`	float	None	Heat exchanger effectiveness (0–1)
`Q`	float	None	Heat duty [W] (for SimpleHEX)
`div_N`	int	200	Number of discretization segments for pinch analysis
`PPT_graph`	bool	False	Show pinch-point diagram during calculation
`Calculate`	bool	False	Solve immediately if True

Output Attributes

Attribute	Type	Unit	Description
`.Q`	float	W	Heat transferred
`.UA`	float	W/K	Overall heat transfer coefficient
`.Hot_to_Cold`	float	—	Enthalpy ratio
`.Hot_Mass_flowrate`	float	kg/s	Hot side mass flow
`.Cold_Mass_flowrate`	float	kg/s	Cold side mass flow
`.Ex_D`	float/str	W	Exergy destruction
`.Solution_Status`	bool	—	True if solved

HEX Types

Type	Description	Use Case
`'SimpleHEX'`	Only one side modelled	Boiler, condenser (external source/sink)
`'double_pipe'`	Both sides modelled, single phase	Recuperator, preheater
`'Condenser'`	Phase change on hot side	Steam condenser
`'Evaporator'`	Phase change on cold side	ORC evaporator

HeatAdded Parameter

Value	Meaning	Effect on Model Summary
`True`	This HEX adds heat TO the cycle	Counted as Q_in
`False`	This HEX rejects heat FROM the cycle	Counted as Q_out
`None`	Internal heat exchange (recuperator)	Not counted in Q_in or Q_out

Case 1: SimpleHEX — Cold Side Heating (Boiler)

Only the cold side (cycle fluid) is modelled. No hot fluid needed.

from ThermoSim import ThermodynamicModel, HeatExchanger

Model = ThermodynamicModel()
Model.set_dead_state()

Model.add_point('water', 'ci', P=8e6, T=350, Mass_flowrate=1)
Model.add_point('water', 'co', P=8e6)

# Known Q: calculate outlet
HeatExchanger(Model, 'Boiler', PPT=5, HEX_type='SimpleHEX',
              HeatAdded=True,
              Hot_In_state=None, Hot_Out_state=None,
              Cold_In_state='ci', Cold_Out_state='co',
              Q=2500e3,
              Calculate=True)

Case 2: SimpleHEX — Hot Side Cooling (Condenser)

Only the hot side is modelled.

Model.add_point('water', 'hi', P=0.008e6, H=2300000, Mass_flowrate=1)
Model.add_point('water', 'ho', P=0.008e6, Q=0)

HeatExchanger(Model, 'Condenser', PPT=5, HEX_type='SimpleHEX',
              HeatAdded=False,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state=None, Cold_Out_state=None,
              Calculate=True)

print(f"Heat rejected: {Model.Component['Condenser'].Q:.0f} W")

Case 3: SimpleHEX — Compute Q from Known Inlet and Outlet

Model.add_point('water', 'ci', P=8e6, T=350,    Mass_flowrate=1)
Model.add_point('water', 'co', P=8e6, T=753.15)

HeatExchanger(Model, 'Boiler', PPT=5, HEX_type='SimpleHEX',
              HeatAdded=True,
              Hot_In_state=None, Hot_Out_state=None,
              Cold_In_state='ci', Cold_Out_state='co',
              Calculate=True)
# Q is calculated automatically

Case 4: SimpleHEX — Known Q, Find Inlet

Model.add_point('water', 'ci', P=8e6, Mass_flowrate=1)   # H unknown
Model.add_point('water', 'co', P=8e6, T=753.15)

HeatExchanger(Model, 'Boiler', PPT=5, HEX_type='SimpleHEX',
              HeatAdded=True,
              Hot_In_state=None, Hot_Out_state=None,
              Cold_In_state='ci', Cold_Out_state='co',
              Q=2500e3,
              Calculate=True)
# Cold inlet H and T are calculated

Case 5: Double Pipe — Both Sides Known, Find Mass Flow

When both hot and cold inlet/outlet enthalpies are known but one mass flow is unknown.

Model.add_point('water',  'hi', P=1e6, T=500, Mass_flowrate=2)
Model.add_point('water',  'ho', P=1e6, T=350)
Model.add_point('R245fa', 'ci', P=5e5, T=300)
Model.add_point('R245fa', 'co', P=5e5)

HeatExchanger(Model, 'Recup', PPT=5, HEX_type='double_pipe',
              HeatAdded=None,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              Calculate=True)

print(f"Cold mass flow: {Model.Component['Recup'].Cold_Mass_flowrate:.3f} kg/s")

Case 6: Double Pipe — Both Mass Flows Known, Cold Outlet Unknown

Model.add_point('water',  'hi', P=1e6, T=500, Mass_flowrate=2)
Model.add_point('water',  'ho', P=1e6, T=350)
Model.add_point('R245fa', 'ci', P=5e5, T=300, Mass_flowrate=3)
Model.add_point('R245fa', 'co', P=5e5)       # H unknown

HeatExchanger(Model, 'HEX1', PPT=5, HEX_type='double_pipe',
              HeatAdded=None,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              Calculate=True)

Case 7: Double Pipe — PPT-Based Solving (No Mass Flow)

When one mass flow is unknown AND one outlet is unknown, the solver uses the pinch point temperature difference to find the missing state.

Model.add_point('water',  'hi', P=1e6, T=500)   # no mass flow
Model.add_point('water',  'ho', P=1e6, T=350)
Model.add_point('R245fa', 'ci', P=5e5, T=300)
Model.add_point('R245fa', 'co', P=5e5)

HeatExchanger(Model, 'HEX1', PPT=10, HEX_type='double_pipe',
              HeatAdded=None,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              PPT_graph=True,
              Calculate=True)

Case 8: Evaporator with Phase Change

Model.add_point('water',  'hi', P=1e6, T=500)
Model.add_point('water',  'ho', P=1e6, T=350)
Model.add_point('R245fa', 'ci', P=5e5, Q=0)   # saturated liquid in
Model.add_point('R245fa', 'co', P=5e5)         # superheated out

HeatExchanger(Model, 'Evap', PPT=10, HEX_type='Evaporator',
              HeatAdded=True,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              PPT_graph=True,
              Calculate=True)

Case 9: Condenser with Phase Change

Model.add_point('R245fa', 'hi', P=5e5, T=400)              # superheated in
Model.add_point('R245fa', 'ho', P=5e5)                      # subcooled out
Model.add_point('water',  'ci', P=1e5, T=293.15, Mass_flowrate=10)
Model.add_point('water',  'co', P=1e5)

HeatExchanger(Model, 'Cond', PPT=5, HEX_type='Condenser',
              HeatAdded=False,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              PPT_graph=True,
              Calculate=True)

Case 10: Effectiveness-NTU Method

Model.add_point('Air', 'hi', P=1e5, T=800, Mass_flowrate=1)
Model.add_point('Air', 'ho', P=1e5)
Model.add_point('Air', 'ci', P=1e5, T=350, Mass_flowrate=1.2)
Model.add_point('Air', 'co', P=1e5)

HeatExchanger(Model, 'Recup', PPT=5, HEX_type='double_pipe',
              HeatAdded=None,
              Hot_In_state='hi', Hot_Out_state='ho',
              Cold_In_state='ci', Cold_Out_state='co',
              effectiveness=0.85,
              Calculate=True)

Complete Example

from Thermosim import ThermodynamicModel, HeatExchanger

Model = ThermodynamicModel()
Model.set_dead_state()

# Hot side
Model.add_point('water', 'H_in',  P=2e5, T=363.15, Mass_flowrate=0.5)
Model.add_point('water', 'H_out', P=2e5)

# Cold side
Model.add_point('water', 'C_in',  P=1.5e5, T=293.15, Mass_flowrate=0.3)
Model.add_point('water', 'C_out', P=1.5e5)

# Create heat exchanger
HeatExchanger(Model, 'Recuperator', PPT=5, HEX_type='double_pipe',
              HeatAdded=None,
              Hot_In_state='H_in', Hot_Out_state='H_out',
              Cold_In_state='C_in', Cold_Out_state='C_out',
              Calculate=True)

# Results
hex = Model.Component['Recuperator']
print(f"Heat transferred:   {hex.Q/1e3:.2f} kW")
print(f"UA value:           {hex.UA:.2f} W/K")
print(f"Exergy destruction: {hex.Ex_D/1e3:.2f} kW")
print(f"Hot outlet:         {Model.Point['H_out'].T - 273.15:.2f} °C")
print(f"Cold outlet:        {Model.Point['C_out'].T - 273.15:.2f} °C")