Gday, Currently I have the task of producing specifications for a water cooled condenser used in distilling liquids. Initially I thought it would be a simple thermodynamics problem. But it has proved quite complex, and I need pointing in the right direction. The problem is, I need to figure out how big to make the condenser to be able to condense all liquid at the same rate as it is boiled. That is, the condenser needs to dissipate the same amount of heat as the boiler element produces, P. The condenser will consist of copper tubbing, length L and inner radius r1 and outer radius r2. The water will flow through the pipe at a rate F with an initial temperature of Tw. The temperature of the vapour outside the tube will be T. My aim is to be able to assign a value to all the variables except for L, therefore work out how long the copper tube needs to be. To begin, I looked up the thermal conductivity of copper (390 W.m^-1.K^-1), and assumed I could work out the power conducted by the copper by knowing the surface area and temperature inside and outside. For the temperature inside, I used an average of the input water temp and output water temp. I worked out the output water temp by using the specific heat of water and flow rate to match the power needed. Does using that average water temperature invalidate my results because of the non linearity of heating the water?? I worked out I need approx 2.7m of 3.8mm inner diameter, 5mm outer diameter tube with a water flow rate of 2L/min to dissipate 2000W from 78C vapour using 35C input water. Does this add up? I'd appreciate if someone with a bit more knowledge of thermodynamics could have a go at the problem and tell me what they get and how they went about it. Thanks for reading if you got this far. Neil Stephens.