1. The problem statement, all variables and given/known data Hi all, I am helping in designing a conveyor that takes freshly milled mild steel bars and submerges them in a tank of cooled water to reduce their temperature enough to to not damage the proceeding equipment. The tank of water will be connected to a separate reservoir of water which will be cooled by the cooling equipment, and will then be pumped around in a cycle as the cooling equipment is not allowed near the milling machines. The question is as follows: Bars of mild steel with a radius of 25mm and a length of 1100mm, as transported into a tank of water, with a constant flow meaning that there will be 6 bars submerged in the water at any time, and will take a total of roughly 144 seconds to pass through the tank. The tank of water holds 275L. The bars will enter the water at roughly 85deg C, and need to be reduced to below 28deg C by the time they leave. How much cooling (how large of a chiller) will need to be applied to the tank, and how much water will the separate reservoir need to hold to keep the water at optimum temperature, enough to chill the bars. 2. Relevant equations I believe that I need to evaluate whether the lumped capacitance method is applicable to the scenario by checking the value of the Biot number, but this is beyond my understanding, I have looked into it via wikipedia and some journals but I am struggling to understand which heat transfer coefficient (h) and thermal conductivity (ks) values to use for my scenario 3. The attempt at a solution So far I have worked out the following: (Mass of metal in 1 bar = 17kg), (Specific Heat Capacity of Mild steel = 0.62j/kg/k or 620j/kg/k SO I use 620j/kg/k as its in Kg, correct?), (Temp change (T Final - T Initial) so 20deg - 85 deg = -65deg) So we have 17kg x 620j/kg/k x -65 = -685100 Next, average heat loss per second per bar = -685100 / 144secs = -4757.64 (J/s or W) (Why is it J/s or W?) And then finally, -4757.64 x 6bars = -28.546 K/watts This answer is not of much use, instead I would need to determine the optimal water temperature for the cooling purpose, and the the optimal temperature depends on the time available for the cooling process. Any help would be greatly appreciated.