Performance improvement of a butane/octane absorption chiller

To improve the coefficient of performance (COP) of an absorption chiller working with the n-butane as refrigerant and the n-octane as absorbent, a thermodynamic analysis based on the first and the second law of thermodynamic is required. A simulation model is established to calculate the different thermodynamic properties of each point of the cycle such as compositions, flow rates, and temperatures. Heat transfer rates and some performance parameters are calculated using the first law analysis. Compared to an ideal machine, the performances are degraded because of the irreversibilities occurring in the different components of the machine. The second law analysis provides the entropy generation in each element and its contribution at the degradation of the COP as well as the total entropy generation of the system. We have proposed a modification of the initial configuration of the machine to reduce the energy losses occurring in the components of high entropy generation and to improve the performance. This recuperation increases the COP from 0.36 to 0.59 and the efficiency from 0.24 to 0.39.

► Simulation of a classical absorption machine working with n-butane/octane as working fluids.
► Determination of the performance parameters (COP and second law efficiency).
► Estimation of the entropy generation of each component of the system and detection of the elements of high energy losses.
► Modification of the initial configuration to recuperate a part of the lost energy.
► Improvement of the performances of the machine.