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API · /vaporpressure-api

Vapor Pressure API

healthy 3,271 Subscribers

Vapor-pressure thermodynamics as an API, computed locally and deterministically. The clausius-clapeyron endpoint predicts the vapor pressure of a substance at a new temperature from a known reference point and the molar enthalpy of vaporization, using ln(P2/P1) = -ΔHvap/R·(1/T2 - 1/T1) with temperatures in kelvin — so from water boiling at 101.325 kPa at 373.15 K and ΔHvap ≈ 40.66 kJ/mol it returns about 42.6 kPa at 350 K. The enthalpy endpoint inverts the same relation: given two pressure/temperature points it solves for the molar enthalpy of vaporization, ΔHvap = -R·ln(P2/P1)/(1/T2 - 1/T1), in J/mol and kJ/mol. The antoine endpoint evaluates the Antoine equation log10(P) = A - B/(C + T) both ways — supply a temperature to get the vapor pressure, or a pressure to get the boiling temperature — defaulting to the water constants (°C and mmHg, so water reads 760 mmHg at 100 °C) but accepting any A, B, C for other substances. The gas constant R = 8.314462618 J/(mol·K). Everything is computed locally and deterministically, so it is instant and private. Ideal for chemical-engineering, process-simulation, distillation, HVAC, meteorology and chemistry-education app developers, boiling-point and phase-equilibrium tools, and lab software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is vapor pressure and boiling point; for humidity and dew point use a psychrometric API and for ideal-gas state use a gas-law API.

#vapor-pressure #thermodynamics #clausius-clapeyron #antoine #boiling-point #developer-tools
api.oanor.com/vaporpressure-api
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Machine-readable spec so AI agents can integrate this API.

/api/vaporpressure-api/openapi.json
/api/vaporpressure-api/llms.txt

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API health

healthy
Uptime
100.00%
Server probes · 24h
Avg latency
87 ms
Server probes · 24h
Subscribers
3,271
active
Total calls
16
last 7 days
status Full status page → · 20 probes/24h

Pricing

Pick a tier — billed monthly, cancel anytime.

Free

Free

  • 3,600 calls / month
  • 2 requests / second
  • Hard cap (429 above quota, no overage)
  • 3,600 calls/month
  • 2 req/sec
  • Clausius-Clapeyron + enthalpy + Antoine
  • No credit card
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Starter

€6.00 /month

  • 38,000 calls / month
  • 6 requests / second
  • Hard cap (429 above quota, no overage)
  • 38,000 calls/month
  • 6 req/sec
  • Custom Antoine constants, boiling point
  • Email support
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Pro

€18.00 /month

  • 182,000 calls / month
  • 15 requests / second
  • Hard cap (429 above quota, no overage)
  • 182,000 calls/month
  • 15 req/sec
  • Process-simulation & distillation pipelines
  • Priority support
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Mega

€58.00 /month

  • 1,120,000 calls / month
  • 40 requests / second
  • Hard cap (429 above quota, no overage)
  • 1,120,000 calls/month
  • 40 req/sec
  • Platform scale
  • Dedicated SLA
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Heat-engine efficiency and coefficient of performance as an API, computed locally and deterministically. The efficiency endpoint gives the Carnot maximum efficiency of any heat engine working between two temperatures, η = 1 − Tc/Th (in kelvin) — the absolute upper limit no real engine can beat — and, given a heat input, the maximum work it could produce and the heat it must reject. The heat-pump endpoint gives the Carnot coefficient of performance of a heat pump, COP = Th/(Th − Tc), and of a refrigerator or air conditioner, COP = Tc/(Th − Tc), and the heat moved for a given work input. The engine endpoint analyses a real engine from its heat balance: from any two of the heat input, the work output, the efficiency or the heat rejected it returns the rest using η = W/Qh and Qc = Qh − W, and — given the reservoir temperatures — compares it to the Carnot limit and reports the second-law (exergy) efficiency. Temperatures accept kelvin, Celsius or Fahrenheit. Everything is computed locally and deterministically, so it is instant and private. Ideal for thermodynamics-education tools, engine, turbine and HVAC design, refrigeration and heat-pump apps, and energy-systems software. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is heat-engine and refrigeration-cycle efficiency; for sensible heat use a specific-heat API and for heat-exchanger LMTD use a heat-exchanger API.

api.oanor.com/carnot-api

Newton Cooling & Convection API

Newton's law of cooling and convective heat transfer as an API, computed locally and deterministically. The convection endpoint applies the convective-heat-transfer rate Q = h·A·ΔT — the heat carried away from a surface equals the convection coefficient times the area times the temperature difference between the surface and the fluid — and solves for whichever of the heat rate, the coefficient, the area or the temperature difference you leave out, with typical coefficients for natural and forced air, water, boiling and condensing built in. The cooling endpoint applies Newton's law of cooling, T(t) = T_env + (T0 − T_env)·e^(−k·t): from an initial temperature, the ambient temperature and a cooling constant (or time constant τ = 1/k) it gives the temperature after a time, or the time to reach a target temperature, or it solves the cooling constant from a measured temperature at a known time — the maths behind how a hot drink, a forensic body or a cooling casting approaches room temperature. The coefficient endpoint links the cooling constant to the physical properties, k = h·A/(m·c), and the thermal time constant. Everything is computed locally and deterministically, so it is instant and private. Ideal for thermal-engineering and HVAC tools, food-safety and forensic cooling apps, electronics-cooling and process-control software, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is convection and transient cooling; for steady conduction through walls use a U-value API and for thermal radiation use a Stefan-Boltzmann API.

api.oanor.com/cooling-api

Heat Exchanger LMTD API

Heat-exchanger LMTD and effectiveness-NTU maths as an API, computed locally and deterministically. The lmtd endpoint computes the log mean temperature difference, LMTD = (ΔT1 − ΔT2)/ln(ΔT1/ΔT2), the true average driving temperature of a heat exchanger, from the hot and cold stream inlet and outlet temperatures for either a counterflow or a parallel-flow arrangement, and flags a temperature cross. The duty endpoint applies Q = U·A·LMTD·F — the heat duty equals the overall heat-transfer coefficient times the area times the LMTD times an optional correction factor — and solves for whichever of the duty, the coefficient, the area or the LMTD you leave out, taking the LMTD directly or from the four temperatures. The effectiveness endpoint uses the effectiveness-NTU method: from the hot and cold heat-capacity rates (given directly or as mass flow times specific heat) and the number of transfer units NTU = U·A/Cmin, it returns the capacity ratio, the effectiveness for the arrangement, and — given the inlet temperatures — the maximum and actual heat duty and the outlet temperatures. Everything is computed locally and deterministically, so it is instant and private. Ideal for process, chemical and mechanical engineering tools, HVAC, refrigeration and thermal-design apps, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is two-stream heat-exchanger analysis; for the sensible heat of a single stream Q = m·c·ΔT use a specific-heat API.

api.oanor.com/lmtd-api

Latent Heat & Enthalpy API

Latent-heat and phase-change enthalpy as an API, computed locally and deterministically. The latent endpoint applies Q = m·L — the heat to melt, freeze, boil or condense a substance equals its mass times the latent heat — and solves for whichever of the heat, the mass or the latent heat you leave out, taking the latent heat of fusion or vaporization directly or from a built-in substance table (water, ethanol, mercury, lead, aluminium, iron, nitrogen, oxygen). The phase-change endpoint computes the full enthalpy of heating or cooling a substance from one temperature to another, automatically combining the sensible heat m·c·ΔT within each phase with the latent heat at every melting and boiling transition it crosses, and returns a step-by-step breakdown — so it can tell you, for example, the total energy to turn ice at −10 °C all the way into steam at 110 °C, using the right specific heat for the solid, the liquid and the gas. The substances endpoint lists the latent heats and per-phase specific heats. Heat is reported in joules, kilojoules, watt-hours and kilocalories. Everything is computed locally and deterministically, so it is instant and private. Ideal for thermodynamics and HVAC tools, refrigeration, heating and process-engineering apps, food and material science, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is latent heat and phase change; for sensible heat alone (Q = m·c·ΔT with no phase change) use a specific-heat API.

api.oanor.com/enthalpy-api

Frequently asked questions

Quick answers about pricing, quotas, and integration.

How do I get an API key for Vapor Pressure API?
Sign up for free at oanor.com, generate an API key from the developer dashboard, and call Vapor Pressure API with the x-oanor-key header. No credit card needed for the free tier.
What's the rate limit for Vapor Pressure API?
Free tier allows 1 request per second. Paid plans scale up to 50 requests per second on the Mega tier. Hard limits return HTTP 429 above the quota — no surprise overage charges.
How much does Vapor Pressure API cost?
Vapor Pressure API has a free tier with 100 calls / month. Paid plans start at €6.00 / month with higher quotas and faster rate limits.
Can I cancel my subscription anytime?
Yes. Plans are billed monthly and you can cancel anytime from your billing dashboard. No long-term contracts and no cancellation fee.
Is Vapor Pressure API GDPR-compliant?
All requests to Vapor Pressure API go through our EU-based gateway. Your upstream API key never leaves our server and no personal data is shared with the upstream provider beyond the request you send.

Pick an endpoint from the list on the left to see its details and try it.

Code snippets

Sign up to get an API key, then call any path under your slug.

curl https://api.oanor.com/vaporpressure-api/SOME_PATH \
  -H "x-oanor-key: oanor_test_..."
const res = await fetch("https://api.oanor.com/vaporpressure-api/SOME_PATH", {
  headers: { "x-oanor-key": "oanor_test_..." }
});
const data = await res.json();
$ch = curl_init("https://api.oanor.com/vaporpressure-api/SOME_PATH");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, ["x-oanor-key: oanor_test_..."]);
$response = curl_exec($ch);
import requests
r = requests.get(
    "https://api.oanor.com/vaporpressure-api/SOME_PATH",
    headers={"x-oanor-key": "oanor_test_..."},
)
print(r.json())

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