РNusselt number Nu. (W/m2.K)(m)/(W/m.K) dimensionlessРIf all the resistance to heat transfer were in a laminar layer of thickness x in which heat transfer was only by conduction.Р(11.25)РThe Nusselt number is the ratio of the tube diameter to the equivalent thickness of the laminar layer.Р(11.24)Р7РWhen apply the Eq.Рinside of the tube (the warm side)Рoutside of the tube (the cold side)Р(11.26)Р(11.27)Рto the heat exchangerР8Р4. Calculation of overall coefficient from individual coefficientРThe heat transfer between warm and cold fluids through metal wall is a series process.Рfluid convection?solid conduction?fluid convectionРFor steady-state heat transfer, rates of heat transfer q are the same.РWarmer fluidРCooler fluidРSolid wallР9РBoth sides of the equation are divided by dAoР(11.30)Р10
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