Water Thermal Properties - Density, Heat Capacity, and Conductivity
Key thermodynamic constants and engineering reference values for water, including boiling point, critical point, latent heat, density, heat capacity, conductivity, viscosity, and thermal expansion.
Overview
Water is a baseline heat-transfer fluid for HVAC, process, power, and laboratory calculations. This page merges the original Engineering ToolBox overview of water thermal properties with the practical temperature-dependent values commonly needed for engineering estimates.
The original reference page is primarily a property index and constants summary. The temperature tables below are representative engineering values at approximately 1 atm and should be used as convenient reference data; for high pressure, saturation, or critical-region calculations, use the linked specialist property pages or IAPWS formulations.
Key Thermodynamic Constants
Property | Value | Condition or Equivalent Units |
|---|---|---|
| Boiling temperature | 99.974 degC = 211.953 degF | At 101.325 kPa |
| Bulk modulus elasticity | 2.15 x 10^9 Pa | Equivalent to N/m2 |
| Critical temperature | 373.946 degC = 705.103 degF | Liquid and vapor phases become indistinguishable |
| Critical pressure | 217.7 atm = 220.6 bar = 22.06 MPa = 3200 psi | Critical point pressure |
| Critical density | 0.322 g/cm3 = 0.62478 slug/ft3 = 20.1018 lbm/ft3 | Critical point density |
| Ionization constant | pKw = 13.995 | At 25 degC |
| Latent heat of melting | 334 kJ/kg = 144 Btu/lb | Ice-water phase change |
| Latent heat of evaporation | 40.657 kJ/mol = 2256 kJ/kg = 970 Btu/lb | At 100 degC |
| Maximum density | 999.975 kg/m3 = 1.9403 slug/ft3 = 8.34519 lbm/US gal | At 4 degC |
| Melting temperature | 0 degC = 32 degF | At 101.325 kPa |
| Molar mass | 18.01527 g/mol | H2O |
| pH | 6.9976 | At 25 degC |
| Specific heat, liquid water | 4.187 kJ/(kg K) = 1.001 Btu/(lbm degF) | At 15 degC / 60 degF |
| Specific heat, ice | 2.108 kJ/(kg K) = 0.5035 Btu/(lbm degF) | Solid phase |
| Specific heat, water vapor | 1.996 kJ/(kg K) = 0.4767 Btu/(lbm degF) | Vapor phase |
| Specific weight | 9.806 kN/m3 = 62.43 lbf/ft3 | At 4 degC |
| Volumetric thermal expansion | 4.2 x 10^-4 | From 4 degC to 100 degC; non-linear with temperature |
| Triple point pressure | 0.00604 atm = 0.00612 bar = 611.657 Pa = 0.08871 psi | Solid, liquid, and vapor coexist |
| Triple point temperature | 0.01 degC = 32.02 degF | Solid, liquid, and vapor coexist |
Source: engineeringtoolbox.com
Temperature-Dependent Properties
Temperature(degC) | Density(kg/m3) | Specific Heat(kJ/(kg K)) | Thermal Conductivity(W/(m K)) | Dynamic Viscosity(mPa s) | Prandtl Number |
|---|---|---|---|---|---|
| 0 | 999.8 | 4.217 | 0.561 | 1.792 | 13.5 |
| 10 | 999.7 | 4.193 | 0.58 | 1.307 | 9.45 |
| 20 | 998.2 | 4.182 | 0.598 | 1.002 | 7.01 |
| 30 | 995.7 | 4.178 | 0.615 | 0.798 | 5.42 |
| 40 | 992.2 | 4.179 | 0.631 | 0.653 | 4.33 |
| 50 | 988.1 | 4.181 | 0.644 | 0.547 | 3.55 |
| 60 | 983.2 | 4.185 | 0.655 | 0.467 | 2.99 |
| 70 | 977.8 | 4.19 | 0.663 | 0.404 | 2.55 |
| 80 | 971.8 | 4.197 | 0.67 | 0.355 | 2.21 |
| 90 | 965.3 | 4.205 | 0.675 | 0.315 | 1.95 |
| 100 | 958.4 | 4.216 | 0.679 | 0.282 | 1.75 |
Source: engineeringtoolbox.com
Key Formulas
Sensible Heat Transfer
where is heat transfer rate, is mass flow rate, is specific heat capacity, and is the temperature change.
Thermal Diffusivity
where is thermal diffusivity, is thermal conductivity, is density, and is specific heat capacity.
Volumetric Expansion Coefficient
Water expansion is non-linear with temperature. Near 4 degC water reaches maximum density, so the sign and magnitude of change around this point.
Sensible Heat Calculator
Water Sensible Heat Transfer
Property Trends
Water Property Trends vs. Temperature
Related Water Property Pages
Use dedicated property pages when pressure, phase boundary, or wider temperature range matters:
- Water boiling point at higher pressures
- Water density, specific weight, and thermal expansion
- Water dynamic and kinematic viscosity
- Water enthalpy and entropy
- Water heat of vaporization
- Water specific heat capacity
- Water thermal diffusivity
- Water saturation pressure
- Water specific gravity vs. temperature
References
- Engineering ToolBox - Water Thermal Properties
- IAPWS, Releases and Guidelines for the Properties of Water and Steam
- NIST Chemistry WebBook, Thermophysical Properties of Fluid Systems