Читать книгу Planning and Executing Credible Experiments - Robert J. Moffat - Страница 21

One night, years ago, my wife baked a Bundt cake (chocolate and vanilla batter layered in a toroidal pan). When she presented me with a slice of that cake for dessert, I was impressed. But, also, I noticed something interesting about the pattern the batter had made as it cooked.

I recognized that the flow pattern, as drawn in figure 1.2, was related to the heat‐transfer coefficient distribution around the baking pan.

I tried to impress my wife with my knowledge of heat transfer by explaining to her what I thought I saw. “Look,” I said, “see how the batter rose up in the center, and came down on the sides. That means that the batter got hot in the center sooner than it did on the edges. That means that the heat‐transfer coefficient is highest at the bottom center stagnation point for a cylinder in free convection with a negative Grashof number.”

My wife was silent for a minute, then gently corrected me “I baked the cake upside down.”

Of course, as soon as I learned that, I was able to say with confidence that “The heat‐transfer coefficient is lowest at the bottom center stagnation point and high on the sides, for a cylinder in free convection with a negative Grashof number.”