Chemical Heat Storage for Saving Exhaust Gas Energy in Internal Combustion Engines

Cao, Duc Luong

Chemical Heat Storage for Saving Exhaust Gas Energy in Internal Combustion Engines

Cao, Duc Luong

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Publication Type:: Thesis
Issue Date:: 2019

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Field	Value	Language
dc.contributor.author	Cao, Duc Luong
dc.date.accessioned	2020-05-05T02:13:46Z
dc.date.available	2020-05-05T02:13:46Z
dc.date.issued	2019
dc.identifier.uri	http://hdl.handle.net/10453/140478
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US
dc.description.abstract	Utilizing the wasted energy is one of the important strategies for addressing the current issue of sustainability by increasing the energy system overall efficiency. Thermal energy storage (TES) systems have been in development to address the above strategy by storing the wasted energy and reusing it when needed. Chemical heat storage (CHS) system is one kind of TES systems, with its advantages of high energy density and long storage time and has been studied in recent years. CHS systems have been applied to storing the solar energy for domestic hot water, air-conditioning, etc. and heat energy required in the thermal power plants. However, research is needed to exploit more applications of CHS to store and utilize the wasted heat energy. Internal combustion (IC) engines have been and are still the main power resource for vehicles and stationary electricity generation systems. However, the heat lost through the exhaust gases of an IC engine is significant and it is the major factor limiting the engine thermal efficiency. Technologies for instantaneously converting the heat energy of the engine exhaust gas to be other forms of energy have become mature, such as thermoelectric generation (TEG) and heat exchangers. Difference from them, CHS stores the wasted energy and reuses it when needed. However, applying CHS in the IC engine is still new. This study was aimed to develop a CHS system using magnesium hydroxide (Mg(OH)₂) and its dehydration and hydration reactions to store the engine exhaust gas energy rather than instantaneous energy conversion until the stored energy was need. To experimentally investigate the performance of the CHS system, a CHS system was developed and tested on a Diesel engine (D1146TI). In the heat storage process, the experiments were conducted at 60%, 70% and 80% engine load conditions. Experimental results showed that at 80% engine load, 61.4% of chemical material reacted and 5.05% heat energy of exhaust gas was stored in an hour. The percentage of the stored exhaust gas energy reduced with the decrease of engine load due to the decrease of the exhaust gas energy. In the heat output process, as one of the proposed applications, the engine intake air was heated with the stored energy by hydrating MgO at the ambient temperature. The experimental results showed that the intake air could be heated to the temperature 5.7°C - 17.3°C higher than the ambient temperature of 23°C. To further investigate the CHS system in engine conditions more than that in experiments, a CFD model of the CHS system was developed using the commercial code of ANSYS FLUENT as a platform. The model was verified by comparing the simulation and experimental results. In the heat storage process and 60 minutes mode, the maximum stored energy in the CHS system was 21.9 MJ which was equivalent to 4.78% of exhaust gas energy with 72.54% of the EM8block reacted at the full engine load. The stored energy and the percentage of reacted EM8block decreased with the decrease of the engine load. In the full charge mode, the simulation results showed that the time on fully charge of the CHS reduced with the increase of the engine load and that the shortest time was 67.1 minutes at full engine load. This time on full charging increased to 110.3 minutes at 50% engine load. The simulation results also showed that the maximum percentage of the exhaust gas energy stored in the CHS system was 7.14% at 70% engine load. In the heat output process, the CFD model was used to test the CHS system at different ambient temperature values. Simulation results showed that the temperature of the engine intake air heated by the CHS could be increased from the ambient temperature of -10°C to 12.15°C. Numerical simulation was also performed to investigate the CHS system modified with two wings added to the exterior wall of the tube of the reactor, aiming to enhance the heat transfer between the exhaust gas and the reactant. In the heat storage process in 60 minutes mode, both the percentage of the stored exhaust gas energy and reacted EM8block increased. Compared with the original CHS system, the percentage of reacted EM8block increased from 72.54% to 81.6% and the percentage of stored exhaust gas energy increased from 4.78% to 5.47% at the full engine load. The effect of the modified CHS system became stronger with the increase of the engine load. In the full charge mode, using the modified CHS system, the full charge time reduced 3.1 minutes at the full engine load and 8.2 minutes at 50% engine load compared with the original CHS system. Furthermore, the maximum percentage of stored exhaust gas energy increased from 7.14 % to 7.58% at 70% engine load. In the heat output process, the effect of the modified CHS system was stronger at the lower ambient temperature and higher reactor wall temperature. In the same condition at the ambient temperature of -10°C and the reactor wall of 85°C, the heated air temperature in the modified CHS system was 1.2°C higher than that in the original one.	en_US
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/140478/2/02whole.pdf
dc.rights	au.edu.uts.lib/ppc
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	info:eu-repo/semantics/openAccess
dc.title	Chemical Heat Storage for Saving Exhaust Gas Energy in Internal Combustion Engines	en_US
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Utilizing the wasted energy is one of the important strategies for addressing the current issue of sustainability by increasing the energy system overall efficiency. Thermal energy storage (TES) systems have been in development to address the above strategy by storing the wasted energy and reusing it when needed. Chemical heat storage (CHS) system is one kind of TES systems, with its advantages of high energy density and long storage time and has been studied in recent years. CHS systems have been applied to storing the solar energy for domestic hot water, air-conditioning, etc. and heat energy required in the thermal power plants. However, research is needed to exploit more applications of CHS to store and utilize the wasted heat energy. Internal combustion (IC) engines have been and are still the main power resource for vehicles and stationary electricity generation systems. However, the heat lost through the exhaust gases of an IC engine is significant and it is the major factor limiting the engine thermal efficiency. Technologies for instantaneously converting the heat energy of the engine exhaust gas to be other forms of energy have become mature, such as thermoelectric generation (TEG) and heat exchangers. Difference from them, CHS stores the wasted energy and reuses it when needed. However, applying CHS in the IC engine is still new. This study was aimed to develop a CHS system using magnesium hydroxide (Mg(OH)₂) and its dehydration and hydration reactions to store the engine exhaust gas energy rather than instantaneous energy conversion until the stored energy was need. To experimentally investigate the performance of the CHS system, a CHS system was developed and tested on a Diesel engine (D1146TI). In the heat storage process, the experiments were conducted at 60%, 70% and 80% engine load conditions. Experimental results showed that at 80% engine load, 61.4% of chemical material reacted and 5.05% heat energy of exhaust gas was stored in an hour. The percentage of the stored exhaust gas energy reduced with the decrease of engine load due to the decrease of the exhaust gas energy. In the heat output process, as one of the proposed applications, the engine intake air was heated with the stored energy by hydrating MgO at the ambient temperature. The experimental results showed that the intake air could be heated to the temperature 5.7°C - 17.3°C higher than the ambient temperature of 23°C. To further investigate the CHS system in engine conditions more than that in experiments, a CFD model of the CHS system was developed using the commercial code of ANSYS FLUENT as a platform. The model was verified by comparing the simulation and experimental results. In the heat storage process and 60 minutes mode, the maximum stored energy in the CHS system was 21.9 MJ which was equivalent to 4.78% of exhaust gas energy with 72.54% of the EM8block reacted at the full engine load. The stored energy and the percentage of reacted EM8block decreased with the decrease of the engine load. In the full charge mode, the simulation results showed that the time on fully charge of the CHS reduced with the increase of the engine load and that the shortest time was 67.1 minutes at full engine load. This time on full charging increased to 110.3 minutes at 50% engine load. The simulation results also showed that the maximum percentage of the exhaust gas energy stored in the CHS system was 7.14% at 70% engine load. In the heat output process, the CFD model was used to test the CHS system at different ambient temperature values. Simulation results showed that the temperature of the engine intake air heated by the CHS could be increased from the ambient temperature of -10°C to 12.15°C. Numerical simulation was also performed to investigate the CHS system modified with two wings added to the exterior wall of the tube of the reactor, aiming to enhance the heat transfer between the exhaust gas and the reactant. In the heat storage process in 60 minutes mode, both the percentage of the stored exhaust gas energy and reacted EM8block increased. Compared with the original CHS system, the percentage of reacted EM8block increased from 72.54% to 81.6% and the percentage of stored exhaust gas energy increased from 4.78% to 5.47% at the full engine load. The effect of the modified CHS system became stronger with the increase of the engine load. In the full charge mode, using the modified CHS system, the full charge time reduced 3.1 minutes at the full engine load and 8.2 minutes at 50% engine load compared with the original CHS system. Furthermore, the maximum percentage of stored exhaust gas energy increased from 7.14 % to 7.58% at 70% engine load. In the heat output process, the effect of the modified CHS system was stronger at the lower ambient temperature and higher reactor wall temperature. In the same condition at the ambient temperature of -10°C and the reactor wall of 85°C, the heated air temperature in the modified CHS system was 1.2°C higher than that in the original one.

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