I don't know if classical physics is the best place to put this, cause normally i would have put it in the engineering section. There is no governing equation right now to describe heat flow between 2 liquids? another question: flow between 2 liquids is governed by convection, if we place an imaginary plate between the 2 liquids and consider the equations between horizontal plate and fluid to find the thermal conductivity of both liquids and the plate. then we take the thickness of the plate to be zero, then we would be left with an equation containing 2 thermal conductivity values and no conduction value thus we would be able to calculate the heat transfer as if the plate never existed. question 3. I need to find the heat loss from a heated pool to ambient cool air, if no formula exists isn't there an approximation or something that i can use? Thnx to anyone who could reply to that!