INTEGRATION OF HEAT EXCHANGERS AND THERMODYNAMIC CYCLE ANALYSIS VIA 1ST AND 2ND LAW TECHNIQUES

摘要

Heat can be defined as the transfer of random energy over a temperature difference. The 2nd Law shows the larger the temperature difference the larger the irreversibility, which represents lost work in engine cycles and extra work required for refrigeration cycles. Thus, the maximization of performance of any external combustion engine or refrigeration cycle is highly dependent upon minimizing the amount of irreversibility in the heat exchange processes such as liquid heaters, boilers, superheaters, condensers, evaporators and stack. While it is relatively easy to identify irreversible processes, it is substantially more challenging to identify the absolute and relative amount of irreversibility for each process in a cycle, and also to compare the irreversibilities of the various heat exchanger based processes with the irreversibilities associated with non ideal adiabatic processes such as turbines, compressors, pumps and throttles. This paper will develop a technique that responds to this challenge by integrating the heat exchangers with the thermodynamic cycle analysis via 1st and 2nd Law techniques, and then demonstrating the application of this technique by quantifying the lost work and lost efficiency associated with each non ideal process in a realistic fuel burning Rankine cycle.