Repeat Prob. 8–125 for cast iron pipes of the same diameter.

Data from problem 125

A geothermal district heating system involves the transport of geothermal water at 110°C from a geothermal well to a city at about the same elevation for a distance of 12 km at a rate of 1.5 m³/s in 60-cm-diameter stainless steel pipes. The fluid pressures at the wellhead and the arrival point in the city are to be the same. The minor losses are negligible because of the large length-to-diameter ratio and the relatively small number of components that cause minor losses.

(a) Assuming the pump-motor efficiency to be 65 percent, determine the electric power consumption of the system for pumping. 

(b) Determine the daily cost of power consumption of the system if the unit cost of electricity is $0.06/kWh.

(c) The temperature of geothermal water is estimated to drop 0.5°C during this long flow. Determine if the frictional heating during flow can make up for this drop in temperature.