Question

An engineer has proposed that compressed air be used to "level the load" in an electrical-generation and distribution system. The proposed system is illustrated in the figure. During those times when electrical-generation capacity exceeds the demand for electrical energy, the excess electrical energy is used to run the compressor and fill the storage tank. When the demand exceeds the generation capacity, compressed air in the tank is passed through the turbine to generate additional electrical energy. Consider this system when the compressor and turbine are isentropic, the tank’s temperature stays constant at 65°F, air enters the compressor at 70°F and 1 atm, the tank volume is 1 million cubic feet, and air leaves the turbine at 1 atm. The compressor is activated when the tank pressure is 1 atm, and it remains on until the tank pressure is 10 atm. The filled compressed-air storage tank is discharged at a later time through the turbine until the pressure in the tank is 1 atm. During this discharge, the temperature of the air in the storage tank remains constant at 70°F. Calculate the total work produced by the turbine and the total heat transferred to the air in the tank during this discharge. Use data from tables.

The work produced by the turbine is  × 10⁷ Btu.

The total heat transferred to the air is    × 10⁸ Btu.

Answer 1

Bte # = 0.24 IbmR B70 W = .0.171 IbonR ka lat psia-fa3 R= 0.3704 Im R 14.696 psig Pinitial lains 145.96 psis Pemul = loads 530 R 70F ta Poitial v RT # initial mass of air, minitial . (14.696) (IXC) 11 0.370 4X 530 : 74860.43 lbm U Panul air Sonal mass of RI nfmal =(146.96)(106) 60.3704) (530) =468604 0 26 Thors

* total leat touns fermed formals Vew (Pone, Pimit) JG (-) KT TE mihé tane Uz to off 3 a '20.171 Bto Proitial = 14.696 Toinni psia psis Ronal 146.96 ka =114, C 50-24 Btu IhmR apsia-ft3 R=0.3704 Ibmok. Taxié) CO.HU) (146.96-149.696) o U 0.3704 104-1 Try (146.96 - 14.696 (14.096 1x10&0.24 iry 146.96 ] V 0.3704 241.9971 - 7.4541 Xco7 Bto Bto Q = 7.454 X1 x107 [heat is transferred from The tanie

Farm Energy Equanian. (6th) = my a T-M; WT-GT (mf-mi ) W = -Q+ Cut (ng my ) -67 (mf. mi) --0-(-) (my mi) w=67.454x63 ) – (0.24 +0:171)(530)(+48604.28–14860.43 Bto W = 4.99 Xco7 to total work 4099 Xco7 Bto required fill the tanie cs S diagram 2 8 A Turbine. stora ger Compressor :5 Ifanil Q = 7154 X1071370 W = 40.99 XcofBtu-