Swap refrigerants¶

The refrigerant is a constructor argument on every model in tmhp. Changing it requires no recalibration and no manufacturer data — pick any name CoolProp recognises and the library re-solves the cycle from first principles. That’s the single most concrete way to see what “refrigerant-agnostic” means in this library.

This page is both a copy-runnable tutorial — sweep four refrigerants at one operating point and inspect the COP — and an engineering reference covering the ten working fluids that actually show up in modern heat-pump design.

Note

Property values quoted below are nominal engineering references from ASHRAE Standard 34 and CoolProp’s REFPROP-grade equations of state. Always reconfirm against the EOS at your specific operating point before sizing — these tables are screening tools, not design data.

Sweep¶

import pandas as pd

from tmhp import AirSourceHeatPumpBoiler

T_tank_w   = 55.0   # °C
T0         = 5.0    # °C
Q_ref_cond = 8_000  # W

refrigerants = ["R32", "R290", "R410A", "R134a"]

rows = []
for ref in refrigerants:
    ashpb = AirSourceHeatPumpBoiler(ref=ref)
    r = ashpb.analyze_steady(
        T_tank_w=T_tank_w,
        T0=T0,
        Q_ref_cond=Q_ref_cond,
    )
    rows.append({
        "ref": ref,
        "cop_ref [-]": r["cop_ref [-]"],
        "cop_sys [-]": r["cop_sys [-]"],
        "E_cmp [kW]": r["E_cmp [W]"] / 1_000,
        "T_evap_sat [°C]": r["T_ref_evap_sat [°C]"],
        "T_cond_sat [°C]": r["T_ref_cond_sat_v [°C]"],
        "failure_reason": r["failure_reason"],
    })

df = pd.DataFrame(rows)
print(df.to_string(index=False))

The output is a four-row DataFrame — same operating point, same code path, four refrigerants. Compressor power, saturation temperatures, and COP all move together with the refrigerant’s EOS.

The cycles, side by side¶

The same sweep, rendered on three P–h panels so the pressure shift is visible at a glance. R290’s saturation envelope sits roughly an order of magnitude lower than R32’s; R134a lands between the two.

Three P-h diagrams for R32, R290, and R134a at the same operating point, showing the saturation envelope and the converged ASHPB cycle for each refrigerant. — Converged ASHPB cycles for R32, R290, and R134a at \(T_{\mathrm{tank}}=55\,^{\circ}\mathrm{C}\), \(T_{0}=7\,^{\circ}\mathrm{C}\), \(\dot{Q}_{\mathrm{cond}}=8\,\mathrm{kW}\). Generated by `scripts/visualization/refrigerant_compare_ph.py`.¶

Reading the result¶

A few things to look for:

failure_reason — should be none for all four at this operating point. If a refrigerant trips cycle_invalid or hx_not_converged, see failure_reason semantics.
``cop_ref`` vs ``cop_sys`` — cop_ref is the cycle COP (condenser duty divided by compressor work). cop_sys also charges auxiliary power (fan, pumps) and is the figure that matches catalogue datasheets.
Saturation temperatures — the evaporating temperature was found by the internal minimiser. Refrigerants with steeper saturation curves end up at different T_evap_sat even when the heat exchangers are identical.

Reference table¶

Refrigerant	Type	ASHRAE	GWP₁₀₀	T_crit [°C]	NBP [°C]	Glide [K]	Primary applications
R32	HFC, single	A2L	675	78	−52	0	Residential AC and DHW heat pumps; the current R410A successor.
R290	HC (propane)	A3	3	97	−42	0	Monoblock outdoor heat pumps; commercial and EU-residential.
R600a	HC (isobutane)	A3	3	135	−12	0	Domestic refrigeration and small (<300 W) heat pumps.
R454B	HFC/HFO blend (R32 / R1234yf, 68.9 / 31.1)	A2L	466	78	−51	~1.5	Newer residential AC/HP; a near drop-in R410A replacement.
R134a	HFC, single	A1	1430	101	−26	0	Industrial heat pumps, chillers, transport refrigeration.
R513A	HFC/HFO blend (R1234yf / R134a, 56 / 44)	A1	631	94	−29	<0.2	Industrial chillers; lower-GWP R134a replacement.
R410A	HFC blend (R32 / R125, 50 / 50)	A1	2088	72	−51	<0.2	Legacy residential AC/HP; being phased down under F-gas regulation.
R1234ze(E)	HFO, single	A2L	<1	109	−19	0	High-temperature heat pumps and centrifugal chillers.
R744	CO₂	A1	1	31	−78 (subl.)	n/a	Transcritical sanitary hot water (60–90 °C), supermarket refrigeration.
R717	NH₃ (ammonia)	B2L	0	132	−33	0	Large industrial heat pumps and process refrigeration.

The glide column shows the temperature difference between bubble and dew points at constant pressure inside the two-phase region. Single-component fluids and near-azeotropes (R410A, R513A) glide by < 0.5 K; zeotropic blends (R454B) glide by ~1.5 K, which matters for evaporator design and for fractionation behaviour on a leak-and-recharge cycle.

Picking by application¶

Use the sweep above as a screening step against the constraints that actually matter for your application. A rough decision guide:

Residential AC / heat pump (split or monoblock, ≤ 12 kW, LWT ≤ 65 °C): R454B (new) or R32 (still allowed in most markets) for split systems; R290 for sealed monoblock outdoor units. R410A only for service of existing installs.
Domestic DHW heat pump (LWT 55–65 °C): R32 or R290 for subcritical designs; R744 for the very-high-LWT (≥ 65 °C with cold return) hot-water-heat-pump pattern.
High-temperature industrial heat pump (LWT 80–95 °C): R1234ze(E), R134a, or R717 (ammonia). R600a is occasionally used for niche small units. tmhp solves these subcritically as long as T_crit clears the condenser by ~10 K; check failure_reason for cycle_invalid.
Very-high-LWT (≥ 90 °C) industrial heat pump: R717 (ammonia) or R718 (water) — the latter requires a radically different compressor class and is not modelled here. Pure R134a / R1234ze(E) can reach 90 °C but with diminishing COP.
Transcritical sanitary hot water (≥ 65 °C, cold return): R744 — the only mainstream refrigerant whose cycle is optimised for this duty. Not subcritical, so the tmhp result is a sanity check rather than a design; see Refrigerants and CoolProp.
Industrial refrigeration and process cooling: R717 (ammonia) is the workhorse. R744 (CO₂) is the growing alternative, often in CO₂/NH₃ cascade systems for supermarkets and cold storage.

The screening table above narrows the candidate list. Once one or two refrigerants survive, re-run a full annual simulation with realistic schedules — see Realistic dynamic simulation.

Screening criteria summary¶

To recap the levers when picking from the table:

Operating-point COP — what the sweep above reports. The refrigerant with the best COP at one operating point is rarely the best across an annual envelope; always confirm against analyze_dynamic with a realistic schedule.
Flammability class — A1 (R410A, R134a, R513A, R744) → A2L (R32, R454B, R1234ze(E)) → A3 (R290, R600a). B-class (R717) is toxic and brings its own code regime.
GWP — for new systems aim for GWP < 700 to align with the EU F-gas 2024 phase-down. R744 / R717 / R290 / R600a / R1234ze(E) are GWP-future-proof.
Critical temperature — sets the practical condenser ceiling for a subcritical cycle. Check the T_ref_cond_sat_v column from the sweep against the refrigerant’s T_crit in the table.
Glide — > 1 K (R454B) means the evaporator should be counter-flow and the refrigerant must be charged from the liquid phase.

Refer to Refrigerants and CoolProp for how CoolProp handles each refrigerant and the cycle-architecture implications.