per Fahrenheit degree
Thermal expansion coefficientexact by definition
The reciprocal Fahrenheit degree is the customary US expansion coefficient. Because a Fahrenheit degree is five-ninths of a kelvin, a coefficient of one per Fahrenheit degree is 1.8 per kelvin, and that factor of 9/5 is exact by definition. Copper is 9.2e-6 per Fahrenheit degree, steel 6.5e-6, and PVC about 30e-6.
Watch out: The direction of the 1.8 is easy to get backwards. Per Fahrenheit degree gives a SMALLER number than per kelvin for the same material, because a Fahrenheit degree is a smaller temperature step and produces less expansion. Going from per-°F to per-K, multiply by 1.8.
| 1 | 1.8 |
Pipe expansion is the everyday use. A 100 foot copper run heated 100 F° grows by 9.2e-6 × 1200 in × 100 = 1.1 inches, which is why hydronic mains get expansion loops and why a rigidly anchored riser will eventually tear something out of a wall.
One per fahrenheit degree in every thermal expansion coefficient unit
| 1,800,000 | part per million per kelvin (ppm/K) | |
| 1,800,000 | part per million per Celsius degree (ppm/°C) | |
| 1,000,000 | part per million per Fahrenheit degree (ppm/°F) | |
| 1,000,000 | microinch per inch per Fahrenheit degree (μin/(in·°F)) | |
| 180 | percent per Celsius degree (%/°C) | |
| 100 | percent per Fahrenheit degree (%/°F) | |
| 1.8 | per kelvin (1/K) | |
| 1.8 | per Celsius degree (1/°C) | |
| 1 | per Fahrenheit degree (1/°F)this unit | |
| 1 | per Rankine degree (1/°R) |