Industrial heat recovery by absorption/compression heat pump using TFE-H2O-TEGDME working mixture

The-thermodynamic performance of a single-stage absorption/compression heat pump using the ternary working fluid Trifluoroethanol-Water-Tetraethylengl ycol dimethylether (TFE-H2O-TEGDME) for upgrading waste heat has been studi ed. A simulation program has been developed using a mathematical model base d on mass and energy balances in all components of the cycle and thermodyna mic equilibrium considerations. In order to establish the optimum operating conditions of the cycle for various thermal conditions, sensitivity studie s of the coefficient of performance (COP), the flow rate of the weak soluti on and the compressor volumetric displacement, both per unit of upgraded en ergy, were carried out versus of water content in the vapour phase. The results obtained show that the operation of the cycle with this ternary system is still more advantageous than the TFE-TEGDME binary working pair. So, it is possible to upgrade thermal waste heat from 80 to 120 degrees C, with a COP of about 6.4, with a compression pressure ratio of 4 at a low p ressure of 100 kPa, the water mole fraction in the vapour being 42%. At the se operating conditions, the necessary weak solution mass flow rate is abou t three times lower than the corresponding binary one. The performance comp arison of such a cycle with other absorption cycles like the heat transform er or the single-effect heat pump, both of them using the-ternary system, s hows its interest and potential. (C) 1999 Elsevier Science Ltd. All rights reserved.