Thermodynamic analysis of absorption chillers: Internal dissipation and process average temperature

Absorption chillers operate well below their reversible or endoreversible limits because their thermodynamic behavior is dominated by internal dissipation, a significant part of which occurs in the chiller's heat exchangers. This fact has summarily been omitted from earlier analyses. It translates into incorrect values for the refrigerant process-average temperature (PAT), and leads to noticeable errors in chiller diagnostics and optimization. Using experimental measurements from an absorption chiller, in concert with a computer simulation code and an analytic thermodynamic model, we fortify these claims with quantitative examples. The correct PAT is derived and its significance in chiller analysis is high-lighted. Aspects of chiller optimization that are unique to absorption technology, as opposed to conventional vapor-cycle reciprocating chillers, are also illustrated. We also substantiate that commercial absorption chiller technology has empirically evolved to close to optimal operating conditions.