ABSTRACT
As discussed in Chapter 6, one of the limitations of single-effect absorption cycles is that they cannot take advantage of the higher availability (exergy) of high-temperature heat sources to achieve higher coefficient of performance (COP). Although the COP of a reversible cycle is quite sensitive to heat input temperature, the COP of a real absorption machine is essentially constant due to the irreversible effects associated with heat transfer. Thus, the cooling COP of a single-effect water/lithium bromide machine is around 0.7, essentially independent of the heat input temperature. To achieve higher cycle performance, it is necessary to design a cycle that can take advantage of the higher availability (or exergy) associated with a higher temperature heat input. Double-effect technology represents one such cycle variation (Alefeld 1983; Alefeld and Ziegler 1985a, 1985b; Alefeld and Radermacher 1994; Wagner et al. 2005). This chapter is devoted to describing the operating characteristics and the performance potential of double-effect, water/lithium bromide technology. Other high-performance cycles are also possible, and an overview of some of these is presented in Chapter 8.
