Free heat exchanger LMTD calculator. Calculate log mean temperature difference, heat duty, required surface area and UA product for counter-flow and parallel-flow heat exchangers.
Heat exchanger sizing is one of those calculations that looks simple in a textbook but has enough small steps that it is easy to get confused in practice. You need to figure out dT1 and dT2 correctly depending on whether the flow is counter or parallel, then compute the log mean correctly, then divide into the heat duty.
I also kept having to remind myself whether counter-flow dT1 is hot inlet minus cold outlet or hot inlet minus cold inlet. So I built this calculator with the arrangement selector so it sets up the temperature differences automatically, you just put in the four temperatures and it handles the rest. Useful for GATE Heat Transfer questions and for quick checks when selecting industrial heat exchangers.