First and Second Law Analyses of Double Effect Parallel and Series Flow Direct Fired Absorption Cycles for Optimum Operating Parameters

Thermodynamic analysis of double effect parallel and series flow direct fired absorption systems with lithium bromide-water has been carried out for different operating conditions. Temperatures in primary generator (T-g) and secondary generator (T-gs)/secondary condenser (T-cs) are optimized analytically using an iterative technique for maximum coefficient of performance (COP) and minimum energy required. A solution distribution ratio for a parallel flow cycle is also optimized. Source of energy used to drive the cycles is considered as compressed natural gas (CNG) and liquefied petroleum gas (LPG). Exergy destruction rate (EDR) in individual components as well as in the whole cycle along with volume flow rate of LPG and CNG is presented and compared. Results show that maximum COP for the parallel flow cycle is 3-6% higher than the series flow cycle. Also, minimum EDR of the parallel flow cycle is around 4% less while energy consumption is 2-3% low as compared to the series flow cycle.