Thermal Conductivity of Water

k_{w} = 0.598\ \text{W/(m}{\cdot}\text{K)}

Value	0.598 W/(m·K)
Status	Measured: ± 0.003 W/(m·K) (0.005 relative)
Source	IAPWS / CRC Handbook of Chemistry and Physics, 104th ed.
Categories	Material Properties Engineering & Trade thermodynamics

k_w in every thermal conductivity unit

watt per meter-kelvin	0.598 W/(m·K)
BTU per hour-foot-Fahrenheit	0.34551801 BTU/(h·ft·°F)

Learning zone

Water conducts heat better than most liquids — roughly four times better than mineral oil and 25 times better than air — thanks to hydrogen bonding, and unusually it improves as it warms, peaking near 0.68 W/(m·K) at about 130 °C before declining. It is one of the terms in the Prandtl number and therefore in every convective correlation for water-side film coefficients.

The distinction that trips people up is conduction versus convection. Still water is a mediocre insulator, but water moving through a tube transfers heat by convection at film coefficients of thousands of W/(m²·K) — the conductivity only enters through the correlation. Adding glycol makes this worse twice over: a 50 % propylene-glycol mix has conductivity near 0.40 W/(m·K) and roughly triple the viscosity at low temperature, which is why glycol loops need larger pumps and more heat-transfer surface for the same duty.

Used by these solvers

Heat Conduction Rate

P = \tfrac{k A \Delta T}{d}

Reynolds Number

Re = \frac{\rho v D}{\mu}