Question

The town of Mustang, TX is concerned that waste heat discharged from a new up- stream power plant will decimate the minnow population in its local stream. The power plant is 35% efficient with a rated output of 350 MW, and 75% of the waste heat is discharged into the stream, which flows at 150 m3/s. Before the power plant starts operations, the stream temperature was 20◦C. If the minnows can handle max- imum stream temperatures of 22◦C, will the water be safe at the point of cooling water discharge? (Assume that the waste heat is discharged to the flow of the whole stream.)

Answer 1

Yes the water will be safe at the point of cooling water discharge

Step-by-step explanation:

Power losses in plant= 350- 350×0.35=227.5MW

Rate of heat rejection to stream= 0.75× 227.5= 170.625MW

Rate of heat rejection= rate of flow of water× c × ΔT

170625000= 150000000× 4.186 × (Final temperature- 20)

Final temperature= 20.3 ◦C

The final temperature of stream will be 20.3 ◦C. Thechange is very small so the minnows will be able to handle this temperature.