ok, this is more of a question of theory than actual calculation. Me and my friends did a physics lab on heat transfer vs. surface area of contact. We used water and oil (since oil will float above the water and creating a surface of contact). We heated the water to ~50 degrees C and oil was left at room temperature. We used different sizes of beakers (with ghetto style insulation) to create different areas of contact, and we measured the temperature with a temperature probe that's plugged into the laptop. so basically we have graphs with the temperature of water decreasing while the temperature of the oil increasing. the problem: the usual equation for heat transfer through conduction has Q (heat transfer), t (time), k (conductivity of barrier), A (area of contact), T (temperature final and initial), and d (thickness of barrier). The problem is with d. since there wasn't an actual barrier in our experiment (it's just water and oil), there wouldn't be a d (d would equal to zero). and if that's true, then the equation won't work. so my question: what should I do now? is there another equation that fits my purpose?