1. Internal combustion engines cooling water valorization through
ISTENER
Internal combustion engines cooling water valorization through
invertible HTHP/ORC systems
Bernardo Peris*, a, Olivier Dumontb , Sylvain Quoilinb, Joaquín Navarro-Esbría
a ISTENER Research Group, Campus de Riu Sec s/n, University Jaume I, E12071, Castellón, Spain
b Thermodynamics and Energetics Laboratory, Chemin des chevreuils, 7 B49, 4000 Liege, Belgium
* address:
Abstract
Power generation through Internal Combustions Engines (ICEs) offers a wide range of possibilities up to 10 MW. Their high efficiency and flexibility not only established ICEs as a premier technology in transportation applications, but also in cogeneration (combined heat and power), due to their heat recovery potential mainly contained in exhaust gases and cooling water. However the lower temperature of the cooling water circuit not always allows its use, often being rejected to the ambient.
Having this into account, this work proposes an efficient method for the ICEs waste heat valorization. It consists of an invertible system between High Temperature Heat Pump (HTHP) and Organic Rankine Cycle (ORC). Thereby from about 90ºC of cooling water waste heat, the HTHP can provide useful heat for processes up to 140 ºC or to generate electricity as ORC system.
1. Invertible HTHP / ORC System
4. Theoretical Performance
2. Cycle Modelization
5. Results
3. Compressor/Expander Optimizations
The built-in volume ratio must be optimized, since the pressure ratio is much higher operating as compressor than as expander.
To adjust the displacement volume to the operating conditions, the rotational speed as expander must be lower than as compressor.
Due to the high difference between the electrical power consumption as HTHP and production as ORC, an electric motor and a generator with different rated powers are proposed.
From 145 kW of cooling water waste heat at 90 ºC, the HTHP can provide 208 kW of useful heat at 140 ºC.
The ICE electrical efficiency increases from 39.2% to 40.4% using the ORC as bottoming power cycle.
Conclusions
The invertible HTHP/ORC has been proven as a method to enhance the electrical and thermal efficiency. For instance, it is demonstrated that its application in a commercial ICE can provide 208 kW of useful heat at 140 ºC or 7.4 kW of electricity. For this, a model has been developed taking into account realistic performance indexes. Moreover, a compressor/expander optimization has been carried out.
Acknowledgements
The authors want to acknowledge the University Jaume I of Spain for the financial support under the PhD grant PREDOC/2013/28 and the stay support E conducted in the University of Liege.