Overall Heat Transfer Coefficient: Definitions, Values & Applications

Calculator for overall heat transfer coefficient and heat transfer through multi-layered walls, pipes, or heat exchangers with fluid flow on each side. Supports both metric and imperial units consistently.

Overall Heat Transfer Coefficient Calculator

Heat transfer through a multi-layered wall can be calculated using:

q = U A ΔT

Where:

q = heat transfer (W or Btu/h)
U = overall heat transfer coefficient (W/(m²K) or Btu/(ft² h °F))
A = wall area (m² or ft²)
ΔT = temperature difference (°C or °F)

For multi-layered walls with equal area in all layers:

1/U = 1/hci + Σ(sn/kn) + 1/hco

Where:

hci, hco = inside/outside convection coefficients
sn = thickness of layer n
kn = thermal conductivity of layer n

Calculator

Inputs

Wall Area (A) (m² or ft²)

Temperature 1 (t1) (°C or °F)

Temperature 2 (t2) (°C or °F)

Inside Convection Coefficient (hci) (W/(m²K) or Btu/(ft² h °F))

Thickness Layer 1 (s1) (m or ft)

Thermal Conductivity Layer 1 (k1) (W/(m K) or Btu/(hr ft °F))

Thickness Layer 2 (s2) (m or ft)

Thermal Conductivity Layer 2 (k2) (W/(m K) or Btu/(hr ft °F))

Thickness Layer 3 (s3) (m or ft)

Thermal Conductivity Layer 3 (k3) (W/(m K) or Btu/(hr ft °F))

Outside Convection Coefficient (hco) (W/(m²K) or Btu/(ft² h °F))

Results

Temperature Difference (ΔT)-- °C or °F

Total Thermal Resistance (R)-- m²K/W or ft² h°F/Btu

Overall Heat Transfer Coefficient (U)-- W/(m²K) or Btu/(ft² h °F)

Heat Transfer (q)-- W or Btu/h

Fluid Configuration	U Range (W/m²K)	Typical Application
Free Convection Gas - Free Convection Gas	1 - 2	Window, room to outside air through glass
Free Convection Gas - Forced liquid (flowing) water	5 - 15	Radiator central heating
Free Convection Gas - Condensing Vapor Water	5 - 20	Steam radiators
Forced Convection Gas - Free Convection Gas	3 - 10	Superheaters
Forced Convection Gas - Forced Convection Gas	10 - 30	Heat exchanger gases
Forced Convection Gas - Forced liquid (flowing) water	10 - 50	Gas coolers
Forced Convection Gas - Condensing Vapor Water	10 - 50	Air heaters
Liquid Free Convection - Forced Convection Gas	10 - 50	Gas boiler
Liquid Free Convection - Free Convection Liquid	25 - 500	Oil bath for heating
Liquid Free Convection - Forced Liquid (Water, no steering)	50 - 100	Heating coil in vessel water
Liquid Free Convection - Forced Liquid (Water, with steering)	500 - 2000	Heating coil in vessel water with steering
Liquid Free Convection - Condensing Vapor Water (stirrers)	300 - 1000	Steam jackets around vessels with stirrers
Liquid Free Convection - Condensing Vapor Water (other liquids)	150 - 500	Steam jackets other liquids
Forced liquid (flowing) water - Free Convection Gas	10 - 40	Combustion chamber + radiation
Forced liquid (flowing) water - Free Convection Liquid	500 - 1500	Cooling coil - stirred
Forced liquid (flowing) water - Forced liquid (flowing) water	900 - 2500	Heat exchanger water/water
Forced liquid (flowing) water - Condensing Vapor Water	1000 - 4000	Condensers steam water
Boiling liquid water - Free Convection Gas	10 - 40	Steam boiler + radiation
Boiling liquid water - Forced Liquid (Water)	300 - 1000	Evaporation of refrigerators or brine coolers
Boiling liquid water - Condensing Vapor Water	1500 - 6000	Evaporators steam/water

Material	Thermal Conductivity (W/(m K))	Notes
Polypropylene (PP)	0.1 - 0.22	Varies with temperature
Stainless Steel	16 - 24	Varies with temperature
Aluminum	205 - 250	Varies with temperature

Configuration	Thermal Resistance (m²K/W)
Static air layer, 40 mm	0.18
Inside heat transfer resistance, horizontal current	0.13
Outside heat transfer resistance, horizontal current	0.04
Inside heat transfer resistance, heat current downward to upward	0.10
Outside heat transfer resistance, heat current downward	0.17

Unit Conversions

Thermal Conductivity:

1 W/(m K) = 0.5779 Btu/(ft h °F)

Heat Transfer Coefficient:

1 W/(m²K) = 0.85984 kcal/(h m² °C) = 0.1761 Btu/(ft² h °F)

Thermal Resistance:

1 m²K/W = 5.678 ft² h °F/Btu