neweng1,
designing a heat recovery system is not easy, and there are different ways to do it - including two main difference: low temperature and high temperature (steam). Sounds like you may be dealing with the more simple low temperature situation:
typically you need a radiator (usually remote-mounted) designed to handle the full heat rejection to the jacketwater (and aftercooler) some engines run the jacketwater and aftercooler on separate circuits. If so you'll need a 2-circuit rad.
if the radiator is remote-mounted you will possibly need an expansion tank on the engine as well as one on the radiator.
additionally, you may need an extra circulating pump and controls if the engine jacketwater pump cannot create the required flow through all the engine-side heat recovery components.
You run a heat exchanger (usually shell-and-tube style) in parallel with the radiator and use a 3-way, thermostatic, load-balancing valve to regulate the temperature of water going to your heat recovery system.
mechanical "AMOT" valves are perfect for this purpose (they use a wax reservoir inside them to control diversion of the coolant flow and do not need electrical power) but they have to be specified at the correct temperature.
you will require a separate heat recovery device to extract heat from the exhaust, with a bypass valve around it.
... and a lot of piping and valves.
Major radiator suppliers and your engine dealers (if they are any good) can assist with all this.
Hope this helps.
