Finally... heat exchanger docs are complete.
Finally... heat exchanger docs are complete.

jcchin/Hyperloop,JustinSGray/Hyperloop,whiplash01/Hyperloop,malachiw7/OpenMDAO-Hyperloop,paulopperman/Hyperloop,UwHyperloop/Hyperloop,whiplash01/Hyperloop,kishenr12/Hyperloop,paulopperman/Hyperloop,JustinSGray/Hyperloop,HyperloopTeam/Hyperloop,malachiw7/OpenMDAO-Hyperloop,UwHyperloop/Hyperloop,kishenr12/Hyperloop,jcchin/Hyperloop,HyperloopTeam/Hyperloop