This page calculates the average heat transfer coefficient and surface temperature for an isoflux (constant and uniform flux) parallel plate vertical channel open to ambient from both ends in a natural convection environment. The convection calculation are based on Rayleigh number.

Define the channel size, uniform heat load and ambient air fluid temperature. You also need to define the fluid properties. This page will calculate a heat transfer coefficient based on the flow conditions as well as the temperature of the plates.

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Channel and Flow Conditions

Fluid Properties at Film Temperature (Default is for Air at 20C)

Description Symbol Value Units
Film Temperature = (Tp+Ta)/2 Tf oC
Specific Heat Cp J/kg-oC
Coefficient of Thermal Expansion B 1/K
Thermal Conductivity k W/m-oC
Dynamic Viscosity µ kg/m-s
Density rho kg/m3

Channel Dimensions

Description Symbol Value Units
Channel Width (across flow) W Meters
Channel Height (with flow) H Meters
Channel Gap S Meters
Total uniform heat load on plates q Watts
Ambient Temperature Ta oC

Results for Plate

Description Symbol Value Units
Flux = q / (2*W*H) q" W/m2
Prandlt Number = Cp*µ / k Pr None
Rayleigh Number = g*B*q"*S4*rho2*Cp / (µ*k2) Ra* None
Ra*S/H  Ra*S/H  None
Nusselt Number = ( 48*H /( Ra*S) + 2.51 / (Ra*S / H)(2/5) )-0.5 Nu None
Average Heat Transfer Coefficient = Nu*k/S h W/m2-C
Plates temperature Tp oC

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