Hot Oil Pump
The hot oil pump is used to circulate the oil. It must be electrically driven and must be able to withstand the high oil temperatures. The pump must also have a high enough flow rate so it can replace the oil in the receiver pipe in a reasonable time.
A receiver pipe with an internal diameter of 2 inches that is 24 feet long will hold about 15 litres of oil. Based on oil heating rate data (see stale air test) I assumed all the oil in the receiver pipe would have to be circulated in about one minute. This will give a required flow rate around 15 litres/min which is very close to many car engine oil pumps (see using recycled car oil pumps). It is very important that a pump is selected that is easy to seal and add fitting to in order to attach to the oil loop plumbing. Because of the high temperature oil leaks can be a large problem. These pumps can also withstand high temperatures and are inexpensive and easy to find. They can be driven electrically by attaching them to an electric motor using gears or a chain. A test was done using a recycled car electric motor and oil pump with very good results (see car oil pump test).
The picture below is of the recycled car part oil pump. An electric motor drives gears to drive the pump. The electric motor is far way from the pump so that the heat from the oil will not overheat the motor (a video of the pump running) or (a video of the pump, hot oil test)