Waste heat from an oven is used to boil water and thereby produce power through

Question

Waste heat from an oven is used to boil water and thereby produce power through a steam turbine. Ignore all stray heat transfer with the surroundings and all kinetic and potential energy effects. For h_1, use h_f at p_sat = 1.0 psia. Specific heats, use C_p = 0.24 BTU/Ib middot degree F for air, and C_p = 1.0 BTU/lb middot degree F for water. Determine the rate of heat transfer from the oven exhaust air to the water in the Steam Generator, in Btu/h. Calculate the mass flow rate of the water, in lb/h. Assume Q = Q_12. Determine the power output of the turbine, in kW.

Explanation / Answer

As per data given in above problem:

Part -a)

In Oven heat transfer is given by: ( oven act as heat exchanger)

Heat loss= heat gain

Qab= Ma * Cpa* (860 - 230) { As temperature of air at inlet and outlet though oven is given }

Qab= 9500 * 0.24 * 630

Qab= 1436400 BTU /hr ( Heat transfer through Oven)

Part -b)

We know that Heat Exchanger is consider to be Heat transfer device where no work is done.

So, Heat loss= heat gain

Qab= Q12

Now , Q12= Mw * Cpw* (600-102)   { As temperature of water at inlet and outlet though oven is given }

1436400 BTU /hr =Mw * 1.0 * (498)

Therefore, Mw = 2884.33 lb/hr

Part -c)

Power generated by turbine :

Power = M* (H3- H2) = 0.3634* (2794.89-2330.3441)

Power = 168.81 KW

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