6 research outputs found
Design and Modelling of a Novel Combustion Heat Exchanger for Household Heating
The present study is focused on the design and modelling of a novel Combustion Heat Exchanger (CHE), used for heating
and hot water supplies in residential buildings. System design includes a combination of an efficient porous burner and heat exchangers.
Combined with an Organic Rankine Cycle (ORC) and a Heat Pump (HP), it is meant to deliver higher energy efficiency as well as
reduced greenhouse gas emissions. A numerical model has been developed in STAR-CCM+ to evaluate the design. Furthermore, system
level heat transfer calculations were acquired to assist with the design process. A step by step approach was undertaken to investigate
physical and chemical phenomena in the system. System dimensions, exchanger location and geometry, air/fuel ratio, porous media
models, radiation and combustion were investigated along with different exchanger geometries. A novel spiral heat exchanger was
introduced in addition to the common coil designs to exhibit both convection and radiation heat transfers. The results indicated that the
exhibition of spiral heat exchanger would result in significantly enhanced heat transfer. Overall heat transfer coefficients of 4-5 times
higher in comparison to coils could be expected for spiral exchangers. It was shown that radiation heat transfer accounts for a prominent
share in the total heat transfer. Furthermore, the CHE could operate at a wide range of lean air/fuel ratios, enabling further decrease in
greenhouse gas emissions. As the last part of the study, further investigations on the regular coil exchangers indicated that these
exchangers could still be used with the design, but heat transfer enhancement is required to reduce the dimensions. Such enhancements
were tested through shell geometry designs with improved results. Overall, the system shows a promising solution for further reduction
of CO2 emissions while improving thermal efficiency
Numerical investigation of natural gas direct injection properties and mixture formation in a spark ignition engine
In this study, a numerical model has been developed in AVL FIRE software to
perform investigation of Direct Natural Gas Injection into the cylinder of
Spark Ignition Internal Combustion Engines. In this regard two main parts
have been taken into consideration, aiming to convert an MPFI gasoline engine
to direct injection NG engine. In the first part of study multi-dimensional
numerical simulation of transient injection process, mixing and flow field
have been performed via three different validation cases in order to assure
the numerical model validity of results. Adaption of such a modeling was
found to be a challenging task because of required computational effort and
numerical instabilities. In all cases present results were found to have
excellent agreement with experimental and numerical results from literature.
In the second part, using the moving mesh capability the validated model has
been applied to methane Injection into the cylinder of a Direct Injection
engine. Five different piston head shapes along with two injector types have
been taken into consideration in investigations. A centrally mounted injector
location has been adapted to all cases. The effects of injection parameters,
combustion chamber geometry, injector type and engine RPM have been studied
on mixing of air-fuel inside cylinder. Based on the results, suitable
geometrical configuration for a NG DI Engine has been discussed
Design and Modelling of a Novel Combustion Heat Exchanger for Household Heating
The present study is focused on the design and modelling of a novel Combustion Heat Exchanger (CHE), used for heating
and hot water supplies in residential buildings. System design includes a combination of an efficient porous burner and heat exchangers.
Combined with an Organic Rankine Cycle (ORC) and a Heat Pump (HP), it is meant to deliver higher energy efficiency as well as
reduced greenhouse gas emissions. A numerical model has been developed in STAR-CCM+ to evaluate the design. Furthermore, system
level heat transfer calculations were acquired to assist with the design process. A step by step approach was undertaken to investigate
physical and chemical phenomena in the system. System dimensions, exchanger location and geometry, air/fuel ratio, porous media
models, radiation and combustion were investigated along with different exchanger geometries. A novel spiral heat exchanger was
introduced in addition to the common coil designs to exhibit both convection and radiation heat transfers. The results indicated that the
exhibition of spiral heat exchanger would result in significantly enhanced heat transfer. Overall heat transfer coefficients of 4-5 times
higher in comparison to coils could be expected for spiral exchangers. It was shown that radiation heat transfer accounts for a prominent
share in the total heat transfer. Furthermore, the CHE could operate at a wide range of lean air/fuel ratios, enabling further decrease in
greenhouse gas emissions. As the last part of the study, further investigations on the regular coil exchangers indicated that these
exchangers could still be used with the design, but heat transfer enhancement is required to reduce the dimensions. Such enhancements
were tested through shell geometry designs with improved results. Overall, the system shows a promising solution for further reduction
of CO2 emissions while improving thermal efficiency