Heat Transfer by Convection

Written by Jerry Ratzlaff on . Posted in Thermodynamics

conduction convection radiantHeat transfer by convection, abbreviated as Qc, also called heat convection or convective heat transfer, is one of four types of heat transfer: conduction, convection, mixing and radiation.  Convection is the energy transfer of heat by air, water, or any other fluid to and object.  It includes energy transferred by random molecular motion as well as energy transferred by the bulk motion of the fluid.  There are two types of convecion: natural convection and forced convection.  Natural convection is fluid flow caused by changes to the fluid, such as change of density or temperature variations of the fluid.  Forced convection is convection that is caused by a a piece of equipment, such as a pump or a fan.


Heat Transfer by Convection formulas

\(\large{  Q_c =  h \; A_c \; \left( T_h \;-\; T_c \right)   }\) 

\(\large{ Q_c = 4.5 \; cfm \; \Delta H }\)

Symbol English Metric
\(\large{ Q_c }\) = heat transfer by convection \(\large{\frac{Btu}{hr}}\)  \(\large{ W }\)
\(\large{ A_c }\) = area cross-section \(\large{ in^2 }\) \(\large{ mm^2 }\)
\(\large{ T_c }\) = cooler temperature \(\large{ F }\) \(\large{ K }\)
\(\large{ T_h }\) = higher temperature \(\large{ F }\) \(\large{ K }\)
\(\large{ cfm }\)  = cubic feet per minute \(\large{\frac{ft^3}{min}}\)  \(\large{\frac{m^3}{min}}\) 
\(\large{ \Delta H }\)  = enthalpy differential \(\large{\frac{Btu}{lbm}}\) \(\large{\frac{kJ}{kg}}\)
\(\large{ h }\) = heat transfer coefficient \(\large{\frac{Btu}{hr-ft^2-F}}\)  \(\large{\frac{W}{m^2-K}}\)


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Tags: Heat Transfer Equations Heat Equations HVAC Equations