The temperature difference between the inlet and outlet of a turbocharger is primarily caused by the compression of air as it passes through the turbocharger's compressor stage.
When the exhaust gases from the engine flow through the turbine stage of the turbocharger, they spin the turbine wheel, which is connected to the compressor wheel. The compressor wheel, in turn, draws in ambient air and compresses it before supplying it to the engine's intake manifold.
During the compression process, the ambient air is forced into a smaller volume, resulting in an increase in pressure. According to the ideal gas law (PV = nRT), when the pressure of a gas increases while its volume remains constant, its temperature also rises.
As the air passes through the compressor stage, it gains energy from the turbine's spinning motion and gets compressed. This compression causes an increase in temperature, resulting in a higher outlet temperature compared to the inlet temperature. The degree of temperature rise depends on various factors such as the design and efficiency of the turbocharger, the pressure ratio across the compressor, and the ambient conditions.
Additionally, the turbocharger itself generates heat due to friction and exhaust gas energy, contributing to the temperature difference. The materials used in the turbocharger, such as the turbine housing and compressor housing, also affect heat transfer and can influence the temperature differential.
It's worth noting that the turbocharger's intercooler, located between the compressor outlet and the engine's intake manifold, helps reduce the temperature of the compressed air before it enters the engine. This intercooling process aims to improve the air density, increase combustion efficiency, and prevent engine knock.
In summary, the temperature difference between the inlet and outlet of a turbocharger is primarily caused by the compression of air during its passage through the compressor stage, as well as the heat generated by the turbocharger itself.