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R-600a pressure–temperature table and P–h diagram

Isobutane — a natural refrigerant. Saturation pressure from −70 to 132 °C, every 2 K, and a pressure–enthalpy diagram to read any state from, computed with CoolProp. Also written R600a.

Safety class A3GWP under 5ODP 0Sources

Pressure–enthalpy diagram

log P · h
Pressure (kPa abs)
Specific enthalpy (kJ/kg)

Point anywhere on the diagram to read the state there

Pressure
—
Temperature
—
Specific enthalpy
—
Specific entropy
—
Density
—
Specific volume
—
Saturation
—
Superheat or subcooling
—

Values come from a CoolProp 7.2.1dev tabulation of R-600a (113 pressures, each with states across its liquid, two-phase and vapour spans), interpolated between the points of that grid, and must be verified by a qualified professional before they're relied on.

Enthalpy and entropy are on the IIR datum: h = 200 kJ/kg and s = 1 kJ/(kg·K) for saturated liquid at 0 °C.

Points

CoolProp
R-600a critical and boiling points
ReadingValue
Critical temperatureCoolProp, from its equation of state134.66°C
Critical pressureCoolProp, from its equation of state3,629.0kPa
Normal boiling pointAt 101.325 kPa, solved by CoolProp−11.75°C

Saturation pressure

kPa abs · bar g
R-600a saturation pressure by temperature, in kPa absolute and bar gauge
T (°C)P (kPa abs)P (bar g)
−704.8−0.97
−685.5−0.96
−666.3−0.95
−647.2−0.94
−628.2−0.93
−609.3−0.92
−5810.5−0.91
−5611.8−0.89
−5413.3−0.88
−5215.0−0.86
−5016.8−0.85
−4818.8−0.83
−4620.9−0.80
−4423.3−0.78
−4225.9−0.75
−4028.7−0.73
−3831.7−0.70
−3635.0−0.66
−3438.6−0.63
−3242.5−0.59
−3046.6−0.55
−2851.1−0.50
−2655.9−0.45
−2461.0−0.40
−2266.6−0.35
−2072.5−0.29
−1878.8−0.23
−1685.5−0.16
−1492.7−0.09
−12100.3−0.01
−10108.50.07
−8117.10.16
−6126.20.25
−4135.90.35
−2146.10.45
0157.00.56
2168.40.67
4180.40.79
6193.20.92
8206.51.05
10220.61.19
12235.41.34
14250.91.50
16267.21.66
18284.31.83
20302.22.01
22321.02.20
24340.52.39
26361.02.60
28382.42.81
30404.73.03
32428.03.27
34452.33.51
36477.53.76
38503.84.03
40531.24.30
42559.74.58
44589.24.88
46619.95.19
48651.85.50
50684.95.84
52719.26.18
54754.76.53
56791.66.90
58829.77.28
60869.27.68
62910.08.09
64952.28.51
66995.98.95
681,041.09.40
701,087.59.86
721,135.610.34
741,185.310.84
761,236.511.35
781,289.311.88
801,343.812.42
821,399.912.99
841,457.813.56
861,517.414.16
881,578.814.77
901,642.015.41
921,707.016.06
941,774.016.73
961,842.817.41
981,913.718.12
1001,986.518.85
1022,061.419.60
1042,138.520.37
1062,217.621.16
1082,299.021.98
1102,382.622.81
1122,468.623.67
1142,556.924.56
1162,647.625.46
1182,740.826.39
1202,836.627.35
1222,935.128.34
1243,036.329.35
1263,140.430.39
1283,247.531.46
1303,357.832.56
1323,471.533.70

Gauge pressure is absolute pressure less a standard atmosphere, 101.325 kPa; below it, gauge pressure is negative.

Identity

Kelvin’s refrigerant library
Designation
R-600a (also written R600a)
Name
Isobutane
Formula
HC(CH₃)₃
Kind
natural refrigerant

Environment and safety

Cited
Safety class
A3Lower toxicity, higher flammability. The class assigned in ISO 817 or ANSI/ASHRAE 34, as tabled in UNEP RTOC 2018; the Australian Government lists A3 (AS/NZS ISO 817).
GWP, 100-year (AR4)
Not listedIPCC AR4 (2007) lists no GWP for it.
GWP, 100-year (AR6)
Not listedIPCC AR6 (2021) lists no GWP for it.
GWP, Australian list
under 5The Australian Government (DCCEEW) lists it with the refrigerants the Ozone Protection and Synthetic Greenhouse Gas Management Act 1989 doesn't control, each with a GWP under 5.
ODP
0Not an ozone-depleting substance in the Montreal Protocol's annexes.

Two GWPs, both for a 100-year horizon. AR4 is the assessment that Australia's Ozone Protection and Synthetic Greenhouse Gas Management Act 1989 and the Montreal Protocol count HFCs in, so it is the figure behind Australia's HFC import phase-down (DCCEEW). The Montreal Protocol's Annexes A, C and F list the same AR4 figures for the CFCs, HCFCs and HFCs they control. AR6 is the IPCC's most recent assessment. The GHG Protocol's table of IPCC GWPs (version 2.0, August 2024) recommends using these latest values.

Sources

  • UNEP RTOC 2018: Annex I to Chapter 2, Tables 2.I-1 to 2.I-3: safety classes as assigned in ISO 817:2014 or ANSI/ASHRAE Standard 34-2016.
  • DCCEEW (Australian Government): Hydrofluorocarbon refrigerants – global warming potential values and safety classifications (last updated 13 December 2024): AR4 GWPs as used under the Ozone Protection and Synthetic Greenhouse Gas Management Act 1989, safety classes from AS/NZS ISO 817:2016.
  • IPCC AR4 (2007): Working Group I, Chapter 2, Table 2.14, 100-year GWP (as corrected in the Working Group I errata).
  • IPCC AR6 (2021): Working Group I, Chapter 7 Supplementary Material, Table 7.SM.7, GWP-100.
  • Montreal Protocol: Annex A, Group I (CFCs), and Annex C, Group I (HCFCs): ozone-depleting potentials.

Source

Computed with
CoolProp 7.2.1dev, HEOS backend — open-source software under the MIT licence
Fluid
IsoButane, CoolProp's pure-fluid model
Equation of state
Buecker-JPCRD-2006B (CoolProp’s reference key)
Cite
Bell, I.H., Wronski, J., Quoilin, S., Lemort, V. (2014). Pure and pseudo-pure fluid thermophysical property evaluation and the open-source thermophysical property library CoolProp. Ind. Eng. Chem. Res. 53(6), 2498-2508.

Related

In R-number order
Before: R-513A · After: R-717
Every refrigerant
All refrigerant tables

Use R-600a in Kelvin

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Note

Verify before relying on these figures

The property figures are computed with CoolProp from published equations of state. The GWP, ODP and safety class are the named sources’ figures, a blend’s GWP and ODP summed from its composition. They must be verified by a qualified professional before they’re relied on.