Temperature drop over hydraulic turbine

[fuentes303]

Assuming an hydraulic turbine of an hydro electric plant. Is it correct to assume that the water temperature at the outlet of the turbine can be calculated from the balance:

enthalpy of water at outlet = (enthalpy of water at inlet) minus (shaft power hydraulic turbine)?

Thanks

 

[btrueblood]

ione,

Kudos, I didn't think about the enthalpy equation (my background is gas turbines, not water wheels), but you are right, a water flow turbine would be better modelled by the velocity (momentum) equations. The enthaply equation would work, but you'd have to calculate from near-static conditions upstream and d/s. Still get a temp. rise, though .

FWIW, have you ever seen an installed Pelton wheel being used? I'm wondering under what circumstances it is more practical than a Francis or screw turbine.

 

[ione]

btrueblood,

I agree that gas/steam turbines are another beast (this is why in my first reply I have asked for a confirmation the OP was talking about hydraulic turbines).

In Italy we have some. Due to the particular morphology of my country it is possible to exploit this kind of installations. Pelton wheels are characterized by relatively small flow rates and big geodetic heads (up to 2000 m), whilst reaction turbines have got higher flow rates and smaller geodetic heads.

 

[BigInch]

I did see a small one on a dairy farm high up in the Andes in Colombia. Making electricity for the farmhouse. And just as Ione says, small flow with about a 150 m head off the clif behind the house. Quite typical most everywhere in Colombia, but usually w/o the generator. Water was snowmelt from 4500 m, so it didn't ever get warm even after going through the heater.

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