Question

A water treatment plant mixer used for coagulation during the summer, when the water temperature is 20 °C, consumes power of 750 W. A classmate of yours estimated that the power consumption during winter, when the water temperature drops to 10 °C, would be 740 W. Does this estimate seem reasonable to you, yes or no?

Answer 1

No, the provided estimate is not reasonable.

The formula for Power Consumption is P=V.u.G​​2

Where V=Volume of the mixer

u=dynamic viscosity

G=velocity gradient

Here, we can see that Power is directly proportional to the dynamic viscosity.

Viscosity is inversely proportional to the temperature. As temperature decreases, the dynamic viscosity increases and so the Power. As in winter, temperature decreases, viscosity increases and so the Power Consumption increases. So the Power Consumption during winter will be more than in summer.