Heres my story of a simple solution, engineers, and Aircraft.
Several years ago I was in charge of a certification program for an engine Conversion to Cessna 340 Aircraft.
We basically replaced the stock TSIO-520 Continental engines (300hp 285 contineous) with Lycoming TIO-540's (350hp)
Part of the certification process involved a Hot Fuel test.
The FAA wanted the fuel heated to 120 degrees F.
The purpose being to demonstrate compliance with Vapor lock margins.
Meaning they basically wanted to be sure that with elevated fuel temps there was no Vapor lock....as the engines stopping would and is considered bad.
So the Engineers and engineering firm came up with a plan:
They proposed to build a rig at the cost of $1200 to heat the fuel to 120 degrees.
They would then circulate the fuel thru the rig and back to the tank.
When all the fuel was 120 degrees we'd go fly the airplane.
Obviously we did this to one engine only.
Me....the mechanic..proposed a simpler solution.
Being the middle of a south Texas summer.......
I wrapped the tank (tip tanks on a C340) in two black plastic trash bags.
Then pushed the airplane outside in the sunlight.
45 minutes later.....Fuel temp. was 126 degrees.
Successful test.
Total cost? About .50 cents for the trash bags.