Parametric optimization of a Rankine cycle based waste heat recovery system for a 1.1 MW diesel-gen-set 2020-01-0890
Due to the increasing fuel demand along with decreasing supply of petroleum, the need for an efficient IC engine is very important. Most IC engines now-a-days operate at a rather low efficiency, ranging from 20 to 40%, from a typical automobile engine to a diesel engine. This paper outlines the parametric study of a Rankine cycle (RC) based waste heat recovery system to improve the overall efficiency of a diesel-gen-set. WHR systems depend greatly on the exhaust temperature of the engine, whereby higher exhaust temperatures will result in a higher gain from the system. In this study, a 1.1MW diesel-gen-set was used to design a WHR system to generate additional power using RC. This is a large diesel engine and therefore, the exhaust temperature and flow rate are quite high to use water as the working fluid in WHR system. A computer code was written for the WHR system which was validated with experimental data. After the initial design of the WHR system, manufacturers were contacted to find out the availability of parts, and then, accordingly the design was changed. All the parts needed are added into WHR system with actual efficiency and losses in the system. There are several heat exchangers required to heat the water from liquid to superheated steam and then, it is passed to the turbine. Then, after the expansion in the turbine, it was passed to condenser (another heat exchanger) to condense the steam to water. Optimization was done on the heat exchangers, focusing on the tube length and diameter. The tube length was changed in accordance to the availability on the market, where it came in either 2 m or 4 m in length. At rated power of the gen-set, with a pressure ratio of 100, an overall improvement of 12.2% was achieved.
Saiful Bari, Wei Zhi Loh
Univ. of South Australia, University of South Australia