So I'm designing a double pipe Heat Exchanger that needs to cool Engine Oil.Here's what I know:The oil is starting at about 95C and needs to be cooled to about 75C, roughly a 20C drop in temperature.The mass flow rate of the oil is roughly 500 kg/hr.I'm using Schedule 40 1/2quot; Steel Pipe. OD=.840quot; ID= .622quot;I'm using water as the coolant, it will be at 25CThe velocity of the water is about 1m/s, and of the oil about .5 m/sAbout what length should I make it? Any tips?
First you need to determine how much heat must be transferred to cool the oil. (Q) Assuming you are going to have a counter flow exchanger you have assume an approach temperature for the cooing water. With that you can calculate the log mean temperature difference. (LMTD) You next need an over all heat transfer coefficient. There are several online sites where you can get typical coefficients. (U) With this information you can calculate the area of the pipe needed and from that the length you need. (A) The equation is : Q equals U X LMTD X A. Solve for A by dividing Q by U X LMTD NOTE : go over size because you can always cut back on the water.
