ts = surface temperature (oC)
te = surrounding environment - ambient - temperature (oC)
For a cold surface where the air will flow downwards - the value will be negative.
Convective air flow volume at a vertical distance generated by the hot or cold surface can be calculated as
Q = 0.019 [g (te - ts) / (273 + te)]0.4 l1.2 (2)
Q = air flow volume (m3/s per meter surface width)
The air velocity at the lower level of a cold (5oC) window with height 2 m in a room with temperature 20oC can be calculated as
vc = 0.65 [(9.81 m/s2) (2 m) ((20 oC) - (5 oC)) / (273 + (20 oC))]1/2
= 0.65 m/s
The air flow volume (for a window with width 1m) can be calculated as
Q = 0.019 [(9.81 m/s2) ((20 oC) - (5 oC) / (273 + (20 oC))]0.4 (2 m)1.2
= 0.033 m3/s
= 119 m3/h
The air flow velocity at the top of a hot (80oC) radiator with height 1 m in a room with temperature 20oC can be calculated as
vc = 0.65 [(9.81 m/s2) (1 m) ((80 oC) - (20 oC) / ((273 K) + (20 oC))]1/2
= 0.92 m/s
The air flow volume (for radiator with width 1 m) can be calculated as
Q = 0.019 [(9.81 m/s2) ((80 oC) - (20 oC) / ((273 K) + (20 oC))]0.4 (1 m)1.2
= 0.025 m3/s
= 90.4 m3/h
Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more.
Calculate the vertical air flow and air velocity generated by a single heat source.
Convective air flows from typical heat sources like people, computers, radiators and more.
Heat transfer between a solid and a moving fluid is called convection. This is a short tutorial about convective heat transfer.
Steam radiators and steam convectors - heating capacities and temperature coefficients.
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