Okay guys, here's the question: My construction company installs utility lines among other things, and we are currently "dewatering" an excavation with pumps running 24/7. Yesterday, with an air temp of 36F, some of the discharge water was freezing on tall grass adjacent to the pump discharges. How can "wind chill" cause the water temp to go below the ambient air temp?
I gotta admit, as an engineer, this is bugging the crap out of me. It also bugs me that one of my employees asked me if it was possible for the pump discharge to freeze at 36F, and I said "No!" (He set me up and got a kick out of proving me wrong, BTW).
The only explanation that I can come up with is some evaporative cooling from the wind that could cause the water temp to go below freezing.