Bachelor's thesis Lutz Schiffer


Advanced exergy analysis of a heat pump system

The exergy destruction of an energy conversion system effects a degradation of energy. In order to discover the genesis of the exergy destruction occurring in each component the advanced exergy analysis splits the exergy destruction into two parts. The endogenous part depends on the inefficiency of the considered component whereas the exogenous part depends on the inefficiency of the other components.
The advanced exergy analysis is applied to a heat pump system consisting of the components evaporator, condenser, valve and compressor. The system is modelled with the software Dymola and simulated under steady state conditions.
The results show that the greatest amount of exergy destruction occurs in the expansion valve. The components condenser, valve and compressor consist of about 50 per cent endogenous and 50 per cent exogenous exergy destruction. In the evaporator the endogenous exergy destruction is even greater than the real exergy destruction, which leads to a negative amount of exogenous exergy destruction. This might due to the fact that it may be not recommendable to split the exergy destruction into the previously mentioned parts.
Based on the results of the advanced exergy analysis it is not possible to determine directly the amount of exergy destruction which can be avoided by improving a component. Therefore it would be more appropriate to simulate component’s improvement separately.
In order to provide a suggestion in which order the components should be improved, a list was made based on the amount of total exergy destruction occurring in the hybrid cycles. The conclusion is that improving the evaporator leads to the greatest decrease of total exergy destruction followed by the components condenser, compressor und valve.