Numerical study of an exhaust heat recovery system using corrugated tube heat exchanger with twisted tape inserts

Author(s):  
Vamsi Mokkapati ◽  
Chuen-Sen Lin
Author(s):  
Moslem Yousefi ◽  
Danial Hooshyar ◽  
Joong H Kim ◽  
Marc A Rosen ◽  
Heuiseok Lim

Nearly 30% of the input energy to a diesel engine is wasted through the exhaust gas; thus, considerable attention has been directed toward developing efficient heat recovery systems for these engines. Given the demonstrated ability of nanofluids to boost the heat transfer rate of heat exchangers, these heat transfer fluids merit consideration for use in diesel exhaust heat recovery systems. In this study, the effects of employing nanofluids on the optimum design of these systems are investigated. An existing heat diesel engine exhaust heat recovery system is modeled to work with Al2O3/water and a modified imperialist competitive algorithm is employed for the optimization. Seven variables consisting of five heat exchanger geometric characteristics together with nanoparticle volume fraction and coolant mass flow rate are considered as design variables. The heat exchanger cost and charging rate of the storage tank are optimization objectives, while the greenhouse gas savings of the heat recovery system are assessed for measuring the environmental impact of the energy recovery. The results indicate that the proposed approach can overcome the challenge of finding the near-optimal design of this complex system and using nanofluids enhances the performance of the heat recovery heat exchanger.


Author(s):  
Shashank Rai ◽  
Selin Arslan ◽  
Badih Jawad

Strict regulations are set up in various parts of the world with respect to vehicular emissions by their respective government bodies forcing automakers to design fuel-efficient vehicles. Fuel economy and carbon emission are the main factors affecting these regulations. In this competitive industry to make fuel efficient vehicles and reduce Green House Gas (GHG) emissions in internal combustions has led to various developments. Exhaust Heat Recovery System (EHRS) plays a vital role in improving powertrain efficiency. In this system, heat rejected by the engine is reused to heat the vehicle fluids faster (like engine coolant, engine oil, etc) also reducing harmful gases emitted. In internal combustion engines, generally only 25% of the fuel energy is converted into useful power output and approximately 40% of it is lost in exhaust heat. Certain studies show that by using the EHRS, the power output can be increased to 40% and the heat loss can be reduced to as much as 25%. The purpose of this study is to make use of this lost energy and convert most of it into useful energy. The thermodynamic properties and fuel consumed during the warmup period were analyzed to measure the improvement in the engine efficiency. The design was implemented on a Briggs and Stratton Junior 206cc engine. This system includes the use of heat exchangers. The main goal of this study is to develop a robust EHRS design and compare it with the baseline engine configuration to see the thermal and fuel economy improvement.


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