Numerical heat transfer analysis of waste heat exchanger for exhaust gas energy recovery

Abstract

Waste heat is heat that is usually thrown into the environment even though it could still be reused for some useful and economic purpose. For example, any exhaust gas stream with a temperature of above 80°C has the potential for significant waste heat recovery. Therefore, an attempt to reuse the exhaust waste energy to transfer the energy to any energy cycle is a worthwhile effort. In the present study, the waste energy from the exhaust gas of an internal combustion engine is recovered by converting it to ammonia (NH 3) as an organic operating fluid in the Organic Rankine Cycle (ORC), which aims to produce 3 kW turbine power. To achieve a specific amount of energy, a key component in waste heat recovery is the heat exchanger. In the present study, a steady-state numerical analysis of heat transfer is conducted for various dimensional configurations of the waste heat exchanger using ammonia. The findings showed that the exhaust gas mass flow rate only has a very minimal effect on the length of the pipe when the exhaust temperature exceeds 400°C.