Experimental testing of a car exhaust heat recovery system utilising TEGs and heat pipes
Exhaust heat recovery systems are used to make use of otherwise wasted heat from a car engine. The purpose of exhaust heat recovery systems is to potentially reduce the fuel consumption of the car and consequently reduce CO2 emissions and running costs. The unique system design described herein utilises thermoelectric generators (TEGs) and heat pipes with its key advantage being it is a passive solid state design. The use of heat pipes allows for more flexible designs as the TEG location is not limited to the exhaust pipe surface. Testing was undertaken on a car with a 3.0L V6 engine. The theoretical modeling was shown to be valid at relatively low exhaust temperatures but deviates at higher exhaust temperatures. It is believed that the heat pipes are operating beyond their capacity at higher temperatures so the model deviates. In all test conditions the power loss due to pressure drop in the exhaust duct was always lower than the electrical power output. Repeat tests were conducted and the results were found to be consistent. When testing the system at different orientations, the bottom heat mode was found to be the best option. After all testing, the maximum power output of the system was 38W from the 8 62mmX62mm TEGs used. The rate of heat transfer in this case was 1541W with the resultant TEG efficiency being 2.46% The calculated potential reduction in CO2 emissions, fuel consumption and fuel costs was 1.57%