Methanol (heat pipe working fluid)

spore: profile
id: methanol-heat-pipe-fluid
spore_version: 0.2
family: alcohols
name: Methanol (heat pipe working fluid)
role: heat pipe working fluid
category: thermal-protection
type: multi-layer-insulation
summary: |
  Methanol (CH3OH, CAS 67-56-1) is a liquid working fluid for heat pipes. NIST records a normal boiling point of 337.8 K and an enthalpy of vaporization of 37.6 kJ/mol at standard conditions. It is flammable: ICSC records a flash point of 9 °C, and NASA heat pipe reports found methanol incompatible with aluminium envelopes.
best_for: Moderate-temperature heat pipes with stainless steel or titanium walls, where ammonia is not used (NASA heat pipe reports)
weakest_at: 'Flammability and toxicity: low flash point and a toxic, flammable vapour (ICSC, NIOSH, PubChem)'
identity:
  formula: CH3OH (also printed as CH4O on the NIST page)
  cas: 67-56-1
  source: nist-webbook-methanol
  where: 'Page header: Formula and CAS Registry Number'
tags:
  applications:
    - thermal-control
properties:
  - benchmark: boiling_point
    label: Normal boiling point (NIST average)
    value: 337.8
    unit: K
    scope: material
    conditions:
      uncertainty: plus or minus 0.3 K
      basis: average of 154 out of 171 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, Tboil
  - benchmark: boiling_point
    label: Boiling point (Wikipedia infobox)
    value: 64.7
    unit: °C
    scope: material
    conditions:
      basis: infobox value in degrees Celsius; the same cell also prints 337.8 K
    method: Infobox value compiled from the cited sources on the page
    status: ground
    source: wikipedia-methanol
    where: Infobox, Boiling point
  - benchmark: melting_point
    label: Melting point (Wikipedia infobox, kelvin)
    value: 175.6
    unit: K
    scope: material
    conditions:
      basis: value printed in kelvin in the infobox
    method: Infobox value compiled from the cited sources on the page
    status: ground
    source: wikipedia-methanol
    where: Infobox, Melting point
  - benchmark: triple_point_temperature
    label: Triple point temperature
    value: 175.5
    unit: K
    scope: material
    conditions:
      uncertainty: plus or minus 0.5 K
      basis: average of 8 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, Ttriple
  - benchmark: critical_temperature
    label: Critical temperature
    value: 513
    unit: K
    scope: material
    conditions:
      uncertainty: plus or minus 1 K
      basis: average of 27 out of 31 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, Tc
  - benchmark: critical_pressure
    label: Critical pressure
    value: 81
    unit: bar
    scope: material
    conditions:
      uncertainty: plus or minus 1 bar
      basis: average of 17 out of 20 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, Pc
  - benchmark: critical_density
    label: Critical density
    value: 8.51
    unit: mol/l
    scope: material
    conditions:
      uncertainty: plus or minus 0.07 mol/l
      basis: average of 7 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, critical density (rho c)
  - benchmark: enthalpy_of_vaporization
    label: Enthalpy of vaporization at standard conditions
    value: 37.6
    unit: kJ/mol
    scope: material
    conditions:
      uncertainty: plus or minus 0.5 kJ/mol
      basis: standard conditions; average of 11 out of 12 values compiled by NIST
    method: Average of literature values compiled by the NIST Thermodynamics Research Center
    status: ground
    source: nist-webbook-methanol
    where: Phase change data, delta vap H degrees
  - benchmark: enthalpy_of_vaporization
    label: Enthalpy of vaporization near boiling
    value: 35.21
    unit: kJ/mol
    scope: material
    conditions:
      temperature: 337.7 K
      basis: single value from the NIST enthalpy table, from Majer and Svoboda (1985)
    method: Value from a compiled enthalpy table
    status: ground
    source: nist-webbook-methanol
    where: Enthalpy of vaporization table, first row
  - benchmark: enthalpy_of_fusion
    label: Enthalpy of fusion
    value: 3.18
    unit: kJ/mol
    scope: material
    conditions:
      temperature: 175.3 K
      reference: Domalski and Hearing, 1996, as cited by NIST
    method: Value from a compiled enthalpy table
    status: ground
    source: nist-webbook-methanol
    where: Enthalpy of fusion table, first row
  - benchmark: density
    label: Density (Wikipedia infobox)
    value: 0.792
    unit: g/cm3
    scope: material
    conditions:
      temperature: not printed on the page
    method: Infobox value; the page gives no temperature
    status: ground
    source: wikipedia-methanol
    where: Infobox, Density
  - benchmark: viscosity
    label: Viscosity (Wikipedia infobox)
    value: 0.545
    unit: mPa·s
    scope: material
    conditions:
      temperature: 25 °C
      basis: the page labels it Viscosity and does not say dynamic
    method: Infobox value
    status: ground
    source: wikipedia-methanol
    where: Infobox, Viscosity
  - benchmark: flash_point
    label: Flash point (ICSC, closed cup)
    value: 9
    unit: °C
    scope: material
    conditions:
      basis: ICSC prints the method as c.c., which means closed cup
    method: Value printed in the ICSC chemical safety card
    status: ground
    source: icsc-0057
    where: Flash point line
  - benchmark: flash_point
    label: Flash point (NIOSH)
    value: 52
    unit: °F
    scope: material
    conditions:
      basis: flash point field as printed; test method not stated on the page
    method: Value printed in the NIOSH Pocket Guide entry
    status: ground
    source: niosh-npg-methanol
    where: Flash point field
  - benchmark: flash_point
    label: Flash point range (Wikipedia infobox)
    value: 11
    value_high: 12
    bound: range
    unit: °C
    scope: material
    conditions:
      basis: range printed in the infobox
    method: Infobox value compiled from the cited sources on the page
    status: ground
    source: wikipedia-methanol
    where: Infobox, Flash point
  - benchmark: autoignition_temperature
    label: Auto-ignition temperature (ICSC)
    value: 440
    unit: °C
    scope: material
    conditions:
      basis: ICSC value as printed
    method: Value printed in the ICSC chemical safety card
    status: ground
    source: icsc-0057
    where: Auto-ignition temperature line
  - benchmark: autoignition_temperature
    label: Auto-ignition temperature (Wikipedia infobox)
    value: 470
    unit: °C
    scope: material
    conditions:
      basis: one of two values printed in the infobox, cited to a different source
    method: Infobox value compiled from the cited sources on the page
    status: ground
    note: The infobox prints a second, lower autoignition value cited to another source; it is not recorded here.
    source: wikipedia-methanol
    where: Infobox, Autoignition temperature
  - benchmark: explosive_limits
    label: Explosive limits in air (NIOSH)
    value: 6
    value_high: 36
    bound: range
    unit: '%'
    scope: material
    conditions:
      basis: lower explosive limit 6.0% and upper explosive limit 36% as printed by NIOSH
    method: Values printed in the NIOSH Pocket Guide entry
    status: ground
    source: niosh-npg-methanol
    where: Explosive limits field
  - benchmark: explosive_limits
    label: Explosive limits in air (ICSC)
    value: 6
    value_high: 50
    bound: range
    unit: vol% in air
    scope: material
    conditions:
      basis: ICSC prints the range as vol% in air without labelling lower and upper limits
    method: Value printed in the ICSC chemical safety card
    status: ground
    note: ICSC's upper value differs from the upper limit printed by NIOSH and Wikipedia; both are recorded.
    source: icsc-0057
    where: Explosive limits line
  - benchmark: vapor_pressure
    label: Vapour pressure (ICSC)
    value: 12.9
    unit: kPa
    scope: material
    conditions:
      temperature: 20 °C
    method: Value printed in the ICSC chemical safety card
    status: ground
    source: icsc-0057
    where: Vapour pressure line
  - benchmark: occupational_exposure_limit
    label: NIOSH recommended exposure limit (TWA)
    value: 200
    unit: ppm
    scope: material
    conditions:
      basis: time-weighted average, as printed; skin absorption also flagged
    method: Value printed in the NIOSH Pocket Guide entry
    status: ground
    source: niosh-npg-methanol
    where: Exposure limits, NIOSH REL
  - benchmark: idlh
    label: Immediately dangerous to life or health (IDLH)
    value: 6000
    unit: ppm
    scope: material
    conditions:
      basis: IDLH value as printed by NIOSH
    method: Value printed in the NIOSH Pocket Guide entry
    status: ground
    source: niosh-npg-methanol
    where: Exposure limits, IDLH
corrosion:
  - environment: Aluminium envelope and wick with methanol charge
    headline: Methanol and aluminium heat pipes are incompatible and generate gas.
    effect: A NASA heat pipe manufacturing study says methanol and aluminium heat pipe combinations are incompatible, resulting in gas generation, and cites an earlier reference for this. The study's own methanol charging results were inconclusive because gas formed during charging.
    rating: severe
    conditions:
      basis: statement in the life-test discussion of the report; no test duration or gas volume is given in the passage
    source: nasa-19750002275
    where: Section 3, life-test results text, printed page 3-23
risks:
  hazards:
    - text: PubChem's ECHA aggregated data lists methanol as a highly flammable liquid and vapour, toxic if swallowed, toxic in contact with skin, toxic if inhaled, and causing damage to organs.
      ghs:
        - H225
        - H301
        - H311
        - H331
        - H370
      source: pubchem-methanol
      where: GHS Classification, ECHA aggregated set
    - text: NIOSH classes methanol as a Class IB flammable liquid and describes it as a colourless liquid with a pungent odour.
      ghs: []
      source: niosh-npg-methanol
      where: Hazard classification and physical description fields
    - text: ICSC states that the substance is irritating to the eyes, skin and respiratory tract, and that a harmful contamination of the air can be reached quickly on evaporation at ordinary room temperature.
      ghs: []
      source: icsc-0057
      where: Short-term effects; Inhalation risk
  failure_risks:
    - mode: Gas generation in an aluminium heat pipe
      trigger: Methanol charged into an aluminium envelope and wick
      consequence: Gas forms inside the pipe. The NASA report calls the methanol and aluminium combination incompatible, so the pipe cannot be relied on to work as designed.
      severity: high
      source: nasa-19750002275
      where: Section 3, life-test results text, printed page 3-23
    - mode: Vapour ignition after a leak
      trigger: Leak or rupture that releases methanol vapour into air
      consequence: Vapour mixes well with air and explosive mixtures form easily (ICSC). The flash point is low (see the flash point properties).
      severity: high
      source: icsc-0057
      where: Physical dangers
  handling:
    - text: Keep methanol away from strong oxidizers. NIOSH lists strong oxidizers as the incompatibility.
      source: niosh-npg-methanol
      where: Incompatibilities and reactivities
    - text: Treat any leak as a fire risk, because the vapour forms explosive mixtures with air easily.
      source: icsc-0057
      where: Physical dangers
uses:
  - application: thermal-control
    device: Gas-loaded variable-conductance heat pipe for temperature control
    example: A NASA report describes a methanol heat pipe that uses nitrogen gas for temperature control, which was constructed and tested with the heat source near ambient temperature. The OCR scan of the abstract is letter-spaced, so this is paraphrased.
    source: nasa-19730022152
    where: Abstract
  - application: thermal-control
    device: Dual-slot heat pipe radiator for solar dynamic heat rejection
    example: A NASA study recommended stainless steel/methanol or titanium/methanol dual-slot heat pipe radiator systems as the baseline configuration for the CBC solar dynamic heat rejection system.
    source: nasa-19880013798
    where: Task 1 results, paragraph on the CBC solar dynamic heat rejection system
  - application: thermal-control
    device: Moderate-temperature aluminium and stainless steel heat pipes
    example: A NASA manufacturing study covered moderate-temperature aluminium and stainless steel heat pipes that used ammonia, Freon-21 or methanol as the working fluid.
    source: nasa-19750002275
    where: Introduction, study scope
supply:
  - subject: Methanol, industrial synthesis
    feedstock: Carbon monoxide and hydrogen react over a catalyst to produce methanol. Synthesis gas made from methane yields more hydrogen than the reaction uses, so some carbon dioxide is often fed in as well. Most green methanol is produced from gasification of biomass.
    source: wikipedia-methanol
    where: Production section; Introduction
media: []
documents:
  - title: 'NIST Chemistry WebBook: Methyl Alcohol (CAS 67-56-1), phase change data'
    type: database
    url: https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C67561
    year: 2026
  - title: 'PubChem REST view: Methanol (CID 887), GHS Classification'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/887/JSON?heading=GHS+Classification
    year: 2026
  - title: 'NIOSH Pocket Guide to Chemical Hazards: Methanol (NPG 0397)'
    type: database
    url: https://www.cdc.gov/niosh/npg/npgd0397.html
    year: 2026
  - title: 'ICSC 0057: Methanol (International Chemical Safety Card)'
    type: database
    url: https://www.inchem.org/documents/icsc/icsc/eics0057.htm
    year: 2026
  - title: NASA heat pipe manufacturing study (NTRS 19750002275)
    type: report
    url: https://ntrs.nasa.gov/citations/19750002275
    year: 1975
  - title: NASA gas-loaded variable-conductance heat pipe report (NTRS 19730022152)
    type: report
    url: https://ntrs.nasa.gov/citations/19730022152
    year: 1973
  - title: NASA solar dynamic heat rejection report, Task 1 (NTRS 19880013798)
    type: report
    url: https://ntrs.nasa.gov/citations/19880013798
    year: 1988
gaps:
  - Global production volume and producer country shares were not found in a page read in this run. Wikipedia gives a production volume without a year and no country shares.
  - Atomic weights for the recipe parts were not taken from a fetched page, so the recipe lists atom counts only.
  - Copper wall compatibility over a stated temperature range was not found. The planner's claim that methanol is the standard fluid for copper heat pipes, with ammonia incompatible with copper, is unsourced here. NASA report 19750002275 has a copper-bronze test table with methanol, but its layout could not be read reliably, so no value was recorded.
  - 'Flash point differs between sources: ICSC gives a closed-cup value, Wikipedia gives a range and NIOSH gives a Fahrenheit value. All three are recorded and none is preferred.'
  - 'Explosive limits differ: NIOSH and Wikipedia give an upper limit of 36%, while ICSC gives 50 vol% in air. Both are recorded.'
  - Liquid thermal conductivity, surface tension, latent heat at heat pipe operating temperatures and the heat pipe operating limits were not found in a page read in this run.
  - Wikipedia gives density without a temperature, and no temperature-dependent density table was read.
  - No flight or space-qualification result for methanol heat pipes was found. The NASA reports read here are ground development and study documents.
  - Radiation and atomic oxygen effects on methanol and its heat pipe walls were not looked up.
  - The PubChem page read here did not print the CAS number; the CAS number is taken from the NIST and NIOSH pages.
  - Two NASA reports (NTRS 19840000109 and 19860055169) could not be downloaded in this run and are not used.
  - The NASA abstract used for the first use is an OCR scan with letter-spaced text, so its wording is paraphrased.
  - Wikipedia prints a second autoignition value cited to another source. It is not recorded.
sources:
  nist-webbook-methanol:
    title: 'NIST Chemistry WebBook: Methyl Alcohol, phase change data and thermodynamic data'
    url: https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C67561
    year: 2026
    kind: database
    license: U.S. Secretary of Commerce, NIST Standard Reference Data (cited, not reproduced)
  wikipedia-methanol:
    title: Methanol (infobox properties, production and history)
    url: https://en.wikipedia.org/wiki/Methanol
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  pubchem-methanol:
    title: 'PubChem compound record: Methanol (CID 887), GHS Classification (ECHA aggregated set)'
    id: CID 887
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/887/JSON?heading=GHS+Classification
    year: 2026
    kind: database
    license: PubChem (NCBI), public domain; ECHA classifications attributed to ECHA
  niosh-npg-methanol:
    title: 'NIOSH Pocket Guide to Chemical Hazards: Methanol'
    id: NPG 0397; RTECS PC1400000
    url: https://www.cdc.gov/niosh/npg/npgd0397.html
    year: 2026
    kind: handbook
    license: U.S. government work (cited, not reproduced)
  icsc-0057:
    title: 'ICSC 0057: Methanol (International Chemical Safety Card)'
    id: ICSC 0057
    url: https://www.inchem.org/documents/icsc/icsc/eics0057.htm
    year: 2026
    kind: handbook
    license: ILO and WHO safety card (cited, not reproduced)
  nasa-19750002275:
    title: 'Heat pipe manufacturing study: aluminium and stainless steel heat pipes with ammonia, Freon-21 and methanol working fluids (NASA)'
    id: NTRS 19750002275
    url: https://ntrs.nasa.gov/citations/19750002275
    year: 1975
    kind: report
    license: public domain (NASA)
  nasa-19730022152:
    title: Construction and testing of a gas-loaded, passive-control, variable-conductance heat pipe (NASA)
    id: NTRS 19730022152
    url: https://ntrs.nasa.gov/citations/19730022152
    year: 1973
    kind: report
    license: public domain (NASA)
  nasa-19880013798:
    title: 'Solar dynamic heat rejection technology, Task 2: heat pipe radiator development (NASA), Task 1 results'
    id: NTRS 19880013798
    url: https://ntrs.nasa.gov/citations/19880013798
    year: 1988
    kind: report
    license: public domain (NASA)
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 22
  unreachable: 0
  caveats: 2
  note: 'Written by an AI assistant on 2026-11-01 from pages fetched in this run. Caveats: the NASA abstract is an OCR scan; the PubChem values come from the REST JSON endpoint.'
story:
  recipe:
    line: 'Methanol (CH3OH) is made industrially by hydrogenating carbon monoxide: carbon monoxide and hydrogen (synthesis gas) react over a catalyst to produce methanol.'
    parts:
      - name: Carbon
        symbol: C
        role: The central carbon atom, bonded to the hydroxyl group and to the hydrogen atoms of the methyl group.
      - name: Hydrogen
        symbol: H
        role: Three hydrogens sit on the carbon and one sits on the oxygen of the hydroxyl group.
      - name: Oxygen
        symbol: O
        role: The hydroxyl oxygen, which together with one hydrogen makes the hydroxyl group that defines an alcohol.
  risk_groups:
    - title: For people
      level: 0
      verdict: 'Toxic and flammable: handle as hazardous'
      lead: PubChem's ECHA data classify methanol as flammable and toxic by several routes. The NIOSH entry adds that it is a Class IB flammable liquid.
      points:
        - label: The liquid
          line: Methanol is a colourless liquid with a pungent odour. The ECHA aggregated set in PubChem lists it as highly flammable, toxic if swallowed, toxic in contact with skin, toxic if inhaled, and causing damage to organs.
        - label: Exposure limits
          line: NIOSH gives a time-weighted average limit of 200 ppm with skin absorption, and an immediately dangerous to life or health value of 6000 ppm.
        - label: Vapour
          line: ICSC says a harmful contamination of the air can be reached quickly on evaporation at ordinary room temperature, and that the vapour forms explosive mixtures with air easily.
    - title: Near a leak or fire
      verdict: Flammable vapour near a leak or fire
      lead: 'The flash point and the explosive limits set the risk: the vapour can ignite at low temperatures.'
      points:
        - label: Flash point
          line: ICSC records a flash point of 9 °C by the closed-cup method. NIOSH records 52 °F, and Wikipedia gives 11 to 12 °C. The sources agree the flash point is low.
        - label: Explosive limits
          line: NIOSH gives a lower limit of 6.0% and an upper limit of 36%. ICSC gives a range of 6 to 50 vol% in air, so the upper value is not settled.
        - label: Ignition
          line: The autoignition temperature is 440 °C in ICSC and 470 °C in Wikipedia.
    - title: Handling and storage
      points:
        - label: Oxidizers
          line: NIOSH lists strong oxidizers as incompatible with methanol.
        - label: Leaks
          line: Because explosive mixtures form easily, a leak should be treated as a fire risk, not only as a toxic release.
  why: Methanol is a light alcohol that boils at 337.8 K at normal pressure, so it works as a two-phase heat transfer fluid in the moderate temperature band where heat pipes are used. A heat pipe carries heat by evaporating a liquid at the hot end and condensing the vapour at the cool end. NASA heat pipe reports list methanol with ammonia and Freon-21 as a candidate working fluid for aluminium and stainless steel envelopes. Its fire and toxicity hazards mean it has to be handled with care, and the material compatibility limits below apply to any design that uses it.
  uses:
    - where: Gas-loaded variable-conductance heat pipe
      line: A NASA report describes a methanol heat pipe that uses nitrogen gas to control temperature. The unit was built and tested with the heat source near ambient temperature.
    - where: Dual-slot heat pipe radiators for solar dynamic power
      line: A NASA study recommended stainless steel/methanol or titanium/methanol dual-slot heat pipe radiators as the baseline configuration for the CBC solar dynamic heat rejection system.
    - where: Moderate-temperature heat pipes
      line: A NASA manufacturing study limited its scope to aluminium and stainless steel heat pipes that used ammonia, Freon-21 or methanol as the working fluid.
  can_do:
    - label: Phase change
      line: Carries heat as a two-phase fluid. It boils at 337.8 K at normal pressure (NIST), and its enthalpy of vaporization is 37.6 kJ/mol at standard conditions (NIST).
    - label: Liquid range
      line: Stays liquid over a wide band. Its triple point is 175.5 K (NIST), and its melting point is 175.6 K in the Wikipedia infobox.
    - label: Critical limit
      line: Has a critical temperature of 513 K and a critical pressure of 81 bar (NIST). Designs should stay below these limits.
    - label: Vapour pressure
      line: Has a vapour pressure of 12.9 kPa at 20 °C (ICSC).
    - label: Gas-loaded design
      line: Can be used in a gas-loaded design that controls temperature with nitrogen gas, as one NASA report describes.
  compare: Methanol is a volatile, flammable working fluid. Its boiling point, enthalpy of vaporization and flash point are the properties that set its heat transfer range and its fire risk. The NASA reports read here tested methanol alongside ammonia and Freon-21, but the passages read did not give numerical comparisons between those fluids, so no ranking is made here. The compare table lists the three properties that matter most for a heat pipe fluid.
  compare_rows:
    - label: Boiling point
      benchmark: boiling_point
    - label: Enthalpy of vaporization
      benchmark: enthalpy_of_vaporization
    - label: Flash point
      benchmark: flash_point
  handling:
    - Methanol is toxic by several routes and flammable. Keep it in closed containers and away from strong oxidizers (NIOSH).
    - Treat a leak as a fire risk, because the vapour forms explosive mixtures with air easily (ICSC).
    - Do not charge methanol into aluminium envelopes. NASA reports the combination as incompatible and generating gas.
  good_for:
    - Heat pipes that must run at moderate temperatures without ammonia, where stainless steel or titanium walls are used (NASA).
    - Gas-loaded variable-conductance designs for temperature control (NASA).
  watch_out:
    - 'Flammable: the flash point is low and the vapour forms explosive mixtures with air easily.'
    - Toxic by ingestion, skin contact and inhalation, according to the PubChem ECHA data.
    - Incompatible with aluminium envelopes, which generate gas (NASA).
  verdict: Methanol is a workable heat pipe fluid in the moderate temperature band, but it is flammable and toxic, and aluminium walls are unsuitable.