Water Steam Thermal Diffusivity

Overview

Engineering reference data for Water Steam Thermal Diffusivity in thermodynamics.

Key Formulas

First Law

$\Delta U = Q - W$

Energy is conserved — heat added minus work done.

Ideal Gas Law

$PV = nRT$

Relates pressure, volume, and temperature of an ideal gas.

Heat Transfer

$Q = mc\Delta T$

Sensible heat transfer.

Carnot Efficiency

$\eta = 1 - T_C/T_H$

Maximum efficiency between two temperatures.

Variables

Symbol	Description	Unit
$U$	Internal energy	J
$Q$	Heat	J
$W$	Work	J
$P$	Pressure	Pa
$V$	Volume	m³
$T$	Temperature	K

Thermal Diffusivity at Atmospheric Pressure

Water thermal diffusivity data at atmospheric pressure (1 bara / 14.5 psia) for both liquid and gas phases.

Thermal Diffusivity vs Temperature and Pressure

Thermal diffusivity of water at various pressures including 1 bara, 10 bara, and 100 bara.

Phase Transition Observations

Water undergoes a dramatic change in thermal diffusivity at the liquid-to-gas phase transition:

• Liquid water has relatively low thermal diffusivity ($\alpha \approx 0.13 - 0.17 \times 10^{-6}$ m²/s), meaning heat transfers slowly through the liquid phase
• Steam has thermal diffusivity approximately 100-200 times higher than liquid water at the same temperature near the boiling point
• At atmospheric pressure, the transition occurs at 100°C (212°F) where $\alpha$ jumps from $0.168 \times 10^{-6}$ m²/s (liquid) to $20.2 \times 10^{-6}$ m²/s (gas)

This significant difference is due to the much lower density of steam compared to liquid water, even though steam has lower thermal conductivity.

Unit Conversions

Common conversion factors for thermal diffusivity:

From	To	Multiply by
1 ft²/h	m²/s	$2.581 \times 10^{-5}$
1 ft²/s	m²/s	$0.09290$
1 m²/h	m²/s	$2.7778 \times 10^{-4}$
1 m²/s	ft²/s	$10.7639$
1 m²/s	ft²/h	$38750.1$

Interactive Charts

References

• Original Source