Thermodynamics Review Problems for Mechanical Engineering Students | Series 28

This review problem is a continuation of the 27^th series and the data obtain in that series are used in solving this review problem. So for this review problem, the net power output of the Brayton cycle is easily obtained by simply subtracting the compressor power, WC from the turbine output, WT. And by doing so, we’ve found out that WNET is equal to 8104 hp. The last parameter that would check the performance of the Brayton cycle is its efficiency and before we can obtain it, let’s define the efficiency of the Brayton cycle for which it is expressed as a ratio of the net power output WNET to the QA of the cycle; wherein QA is the power being generated during combustion in the combustor. As for the heat that is being added to the cycle, the formula for it is expressed in the following equation, QA = mc_p(T₃ - T₂), since process 2 -> 3 is an isobaric heat addition process, that’s why we are using specific heat capacity at constant pressure, cp. And by using the mentioned formula, we’ve found out that the heat that is being added to the cycle is equal to 16814 hp. Finally, we can now compute for the efficiency of the Brayton cycle and by using the formula for efficiency that is expressed as a ratio of WNET and QA; we’ve found out that the Brayton cycle is 0.4820 = 48.20 % efficient.