curl --request POST \
  --url https://api.iotools.cloud/v1/tool/heat-exchanger-lmtd-calculator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "arrangement": "counter",
  "temperatureUnit": "c",
  "hotIn": "150",
  "hotOut": "100",
  "coldIn": "20",
  "coldOut": "80",
  "overallCoefficient": "500",
  "duty": "250"
}
'

{
  "tool": "heat-exchanger-lmtd-calculator",
  "tool_version": "1.0.2",
  "outputs": {
    "status": "LMTD = 74.89 °C. Required area ≈ 6.677 m².",
    "results": [
      {
        "property": "Flow Arrangement",
        "value": "Counter-flow (counter-current)"
      },
      {
        "property": "ΔT1 (larger end)",
        "value": "80.00 °C"
      },
      {
        "property": "ΔT2 (smaller end)",
        "value": "70.00 °C"
      },
      {
        "property": "LMTD (uncorrected)",
        "value": "74.89 °C"
      },
      {
        "property": "Overall Heat Transfer Coefficient (U)",
        "value": "500.0 W/(m²·K)"
      },
      {
        "property": "Heat Duty (Q)",
        "value": "250.0 kW"
      },
      {
        "property": "Required Heat Transfer Area (A = Q / (U × LMTD))",
        "value": "6.677 m²"
      },
      {
        "property": "Note",
        "value": "Assumes constant specific heats and an overall U — a preliminary sizing estimate, not a detailed rating calculation."
      }
    ]
  },
  "credits_used": 5,
  "credits_remaining": null
}