1 reply to this topic

[freeman]

Dear All,

 

As you know, to size a electrical water heater it's enough to calculate electrical power. I wish to know the heater efficiency in % which is used as a criteria to calculate the power.

 

Q=(mass flowrate)*Cp*DeltaT/(3600*Efficiency)              (Metric)

 

 

Thanks

 

[Art Montemayor]

Freeman:

 

I've always taken an electric process immersion heater  as being essentially 100% efficient.  In other words, all the electric power you apply with it is coverted to heat and this is directly imposed on the fluid you are heating.  Unlike a heat exchanger, you don't have a return electric flow with unused heat.   I don't recall ever having to apply the power factor to a resistance heater.  I have always calculated the Btu/hr required as the heat transferred and directly converted this into kW.   There are, of course some losses, but I always leave that up to the fabricator and they are usually small.