Why are you using a hot oil bath? With a 45deg C outlet on the crude oil, your LMTD is not that bad and the U is better. Using a heat medium oilbath can produce coking of the firetube if the maximum film temperature of the oil is exceeded. Just a word of caution on that matter.
If you are truely wanting a indirect fired heater then the bath will be glycol/water mix. The crude oil will flow through the process coil that is immered in the bath. If you will go to mohawkprocess.com
you can see a picture of a indirect heater. I will be happy to provide you a size if you...
