The Effect Of Lithium Bromide On The Performance Of Ammonia-Water Absorption-Resorption Heat Pump System

Ammonia absorption-resorption heat pump (ARHP) has lower operating pressure than the absorption heat pump, and it can also make full use of low-grade heat in the heating process. But the low coefficient of performance (COP) limits the applications of ammonia ARHP. Lithium bromide, as the third working medium, is added to the traditional ammonia-water working pair to improve the performance of the system. In this paper, COPs of NH3-H2O-LiBr ternary working fluid ARHP systems under different operating temperatures are studied by a simulation model established in Aspen Plus. The operating temperature parameters ranges of the ternary ARHP are compared with those of the binary ARHP. The simulation results indicate that the COP of the ternary system is greatly influenced by the concentration of lithium bromide, and it improves up to 21% at T-Gen = 100 degrees C, T-Des = T-Abs = T-Res = 40 degrees C, and P-H/P-L, = 1.5/0.48 MPa. Besides, when lithium bromide is added to the binary ARHP, the minimum values of (TGen) and T-Res are reduced to 87 degrees C and 3 degrees C, respectively. In contrast, the maximum values of T-Abs and T-Res are increased to 47.5 degrees C compared with the binary system. The NH3-H2O-LiBr ternary working fluid makes the low-grade heat reused by the ARHP more efficiently.