Suppose a hot body is surrounded by a coil of very good thermally conducting pipe with cold water flowing inside which comes at a certain fixed low temperature in the pipe and leaves at some higher temperature after absorbing the heat. Will the rate of the hot body’s cooling down increase or decrease with increase in the water flow rate?
I think the rate of cooling will increase. But this is also in opposition to the intuition that the water will have less time to take away heat from the hot body, hence decreasing the cooling rate. I doubt that this is wrong since though the water is moving faster, water behind with lower temperature is following immediately after.