Kok Seng Ong - Academia.edu (original) (raw)
Papers by Kok Seng Ong
Nucleation and Atmospheric Aerosols, 2017
A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat ef... more A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat effectively and efficiently over a long distance and with a small temperature difference between the heat source and heat sink. A heat pipe consists of a metal pipe initially vacuumed and then filled with a small quantity of fluid inside. The pipe is separated into a heating (evaporator) section and a cooling (condenser) section by an adiabatic section. In a run-around-coil heating, ventilation and air conditioning system, a wrap-around heat pipe heat exchanger could be employed to increase dehumidification and to reduce cooling costs. The thermal performance of a thermosyphon is dependent upon type of fill liquid, fill ratio, power input, pipe inclination and pipe dimensions. The boiling and condensation processes that occur inside a thermosyphon are quite complex. During operation, dry-out, burn-out or boiling limit, entrainment or flooding limit and geysering occur. These phenomena would lead to non-uniform a...
Drying Technology, Apr 1, 1999
... 4. Hildebrand, R., 1970, "Kiln drying of sawn timber", Roben Hilderbrand Co... more ... 4. Hildebrand, R., 1970, "Kiln drying of sawn timber", Roben Hilderbrand Corp. 5. Langrish. T. A. G. and RB Keey, 1991. "A solar heated kiln for drying New Zealand hardwoods", Trans. Inst. ... 18(2), 10-26. l 1 . Taylor. K. I. and AD Weir. 1985, "Simulation of solar linlber drier". ...
Elsevier eBooks, 1980
Solar energy provides a source of non-polluting and virtually inexhaustible energy supply which c... more Solar energy provides a source of non-polluting and virtually inexhaustible energy supply which could be harnessed relatively cheaply and easily for domestic, commercial, industrial and agricultural applications. The practical utilisation of solar energy in rural farming areas in Malaysia is mainly for crop and timber drying. Some feasible solar crop drying systems are discussed. A programme for research and development on solar drying technology for rural development is outlined.
Heat Transfer Engineering, Nov 1, 2010
Experimental investigations were conducted to determine the thermal performances of an R-134a-fil... more Experimental investigations were conducted to determine the thermal performances of an R-134a-filled thermosyphon heat pipe heat exchanger (THPHE) and a water-filled loop heat pipe heat exchanger (LHPHE) for hot and cold energy recovery for air conditioning purposes. For such applications, the heat pipe heat exchangers are operated at low temperatures. Both exchangers were operated in the countercurrent flow mode. This article presents the experimental results obtained. The results showed that heat transfer rate increased as evaporator inlet temperature increased and as both evaporator and condenser velocities increased. The overall effectiveness for the THPHE ranged from 0.8 to a minimum of about 0.5, while for the LHPHE it ranged from 0.9 to 0.3. Overall effectiveness was found to approach a minimum when both air streams have equal velocities.
Polymers, Jun 18, 2017
In this study, reduced graphene oxide (RGO)/polymethyl methacrylate (PMMA) nanocomposites were pr... more In this study, reduced graphene oxide (RGO)/polymethyl methacrylate (PMMA) nanocomposites were prepared by employing in situ polymerization and solution blending methods. In terms of mechanical properties, RGO loading increased the Young's modulus but decreased the elongation at break for RGO/PMMA nanocomposites. Tensile strength for solution blended RGO/PMMA nanocomposites increased after adding 0.5 wt % RGO, which was attributed to the good dispersion of RGO in the nanocomposites as evidenced from SEM and TEM. Solar energy conversion efficiency measurement results showed that the optimum concentration of RGO in the RGO/PMMA nanocomposites was found to be 1.0 wt % in order to achieve the maximum solar energy conversion efficiency of 25%. In the present study, the solution blended nanocomposites exhibited better overall properties than in situ polymerized nanocomposites owing to the better dispersion of RGO in solution blending. These findings would contribute to future work in search of higher conversion efficiency using nanocomposites.
Applied Thermal Engineering, Aug 1, 2016
Abstract The thermal performances of a R410A filled thermosyphon subjected to low power input fro... more Abstract The thermal performances of a R410A filled thermosyphon subjected to low power input from 40 to 100 W and evaporator wall temperatures between 25 °C and 50 °C with fill ratios between 0.50 and 1.00 and at different inclinations from 30° to 90° were investigated. The axial temperature distribution of the thermosyphon was found to be quite uniform at all temperatures with the exception of the bottom end of the evaporator at all power input. The performance of the thermosyphon determined from the heat transfer resistance of the thermosyphon was found to be independent of fill ratio and inclination. Comparisons with other investigators using water, R410A and R134a would seem to indicate that a lower aspect ratio resulted in higher resistance and thus lower thermal performance.
IOP Conference Series: Earth and Environmental Science, 2021
The temperature of a PV panel rises during operation which affects its power output. A PV panel i... more The temperature of a PV panel rises during operation which affects its power output. A PV panel is similar to a flat plate solar collector. This paper presents a simple theoretical heat transfer resistance model and a solution procedure to predict the absorber plate surface temperature of the solar collector. The model consisted of a rectangular cross-section steel duct placed inclined at an angle to the horizontal and exposed to solar radiation. The heat absorbed on the top surface of the plate is transmitted by conduction through the plate and heats the air in the duct. This creates a natural buoyancy effect which induces a natural convection air flow rate. A simple one-dimensional theoretical model of the solar collector with the thermal resistances of the various components is proposed. Simulated results of plate temperature and induced air flow velocity are presented.
IOP Conference Series: Earth and Environmental Science, 2021
This study investigates the effect of inclination angle of a flat plate solar air collector in Ka... more This study investigates the effect of inclination angle of a flat plate solar air collector in Kampar, Malaysia. Flat plate solar air collectors have been investigated since the early 1950s for air heating and crop drying. Their performances under natural convection air cooling are very similar to a photovoltaic (PV) panels for power production. A PV panel becomes hot when operating under hot weather which will affect the efficiency and lifespan. The panel could be cooled down by providing an air duct underneath which allowing natural convection air circulating inside the duct. The degree of cooling would depend upon the angle of inclination of the panel. This paper presents some experimental results on the effect of inclination angle on the performance of a flat plate solar air collector under natural convection air cooling.
IOP Conference Series: Materials Science and Engineering, 2020
Main barriers for installation of conventional solar water heating system (SWHS) are requirement ... more Main barriers for installation of conventional solar water heating system (SWHS) are requirement of large installation area and heavy weight of the heat storage tank consisting water. A storage tank with minimum capacity of 230 liters are needed for household usage and this tank when empty can weigh up to 100 kg while a filled tank could weigh up to 400 kg. In reality, installation of this conventional system require more space and heavy structural support on the roof, which is not available in most houses. As a solution, a form stable light harvesting phase change material (FSLHPCM) integrated compact system is proposed. This new SWHS consists of glass – topped collector cum storage tank filled with FSLHPCM. This new FSLHPCM is form stable, does not leak and exhibit stable latent heat when tested to 1000 thermal cycles. It is capable to not only store heat but can improve the collector efficiency by harvesting the visible light and converting it to heat. The additional light to hea...
Solar Energy, 1974
The theoretical performance of a solar water heater operating under thermosiphon-flow conditions ... more The theoretical performance of a solar water heater operating under thermosiphon-flow conditions was evaluated using a finite-difference solution procedure. Tests were conducted on an experimental heater which incorporated a flat-plate collector design. Experimental water mass flow rates were measured at half-hour intervals using a dye-injection method while the temperature distribution of the system was monitored continuously. Some defects in the theory arising from inaccurate assumptions of the mean temperatures of the various components of the system are pointed out. Fortunately, these defects are significant only during the early and late periods of the day. Throughout the main insolation period, satisfactory qualitative and quantitative agreement can be obtained between experimental and theoretical results. A proposal for future study to investigate the reverse-flow phenc, ena is introduced.
International Journal of Productivity and Quality Management, 2022
We report an extended surface technique that utilises micro-fin arrays to enhance the heat transf... more We report an extended surface technique that utilises micro-fin arrays to enhance the heat transfer performance in the microchannels at Reynolds number ranging from 400 to 1000. Three different types of microfins namely Case A (cylindrical micro-fin), Case B (offset cylindrical micro-fin) and Case C (diverge cylindrical micro-fin) are designed. A comparative study between the three cases and bare rectangular microchannel was conducted. The technique enhances the thermal dissipation rate while keeping the pressure drop at a satisfactory level through proper design configurations. Numerical study has been performed in order to elucidate the single phase heat transfer phenomena in the present study.
International Journal of Productivity and Quality Management, 2021
Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
... In order to assist in providing a comfortable and cool environment inside the house, removal ... more ... In order to assist in providing a comfortable and cool environment inside the house, removal of the hot air in the ceiling and reducing the ... Hamdy and Fikry [12] showed that the optimum tilt angle for a solar air heater connected in series with a vertical solar chimney was at 60 o ...
Solar Energy, 2003
A mathematical model of a solar chimney was proposed in order to predict its performance under va... more A mathematical model of a solar chimney was proposed in order to predict its performance under varying ambient and geometrical features. Steady state heat transfer equations were set up using a thermal resistance network and solved using matrix inversion. Existing correlations of heat transfer coefficients were utilised. Property values for the air flow in the duct were based on mean bulk or film temperatures. The performance of the chimney was evaluated by predicting the temperatures of the glass glazing and the heat-absorbing wall and also the temperature and velocity of the induced air flow in the chimney. The effects of air gap and solar radiation intensity on the performance of different chimneys were investigated. In order to verify the theoretical model, experiments were conducted on a 2 m high30.45 m wide physical model with air gaps of 0.1, 0.2 and 0.3 m. Experiments were carried out outdoors on the roof and the experimental model exposed to both 21 21 22
System performance of a solar water heater depends upon collector and storage tank design (dimens... more System performance of a solar water heater depends upon collector and storage tank design (dimensions, insulation, pipe connections, etc.) and weather con ditions (solar radiation intensity and ambient temp rature). Nocturnal reverse flow and tank insulation dictate th degree of overnight water temperature drop in t he storage tank. A tropical country like Malaysia has widely fluctuating and intermittent solar radiation . It is neither practical nor feasible to conduct outdoor t ests such as that proposed by International Standar ds. Indoor collector tests are expensive to conduct and would not provide meaningful information to the domestic or commercial end user. Outdoor system tes ts would be more informative to consumers who would like to compare the water temperatures that could b e achieved in order to choose from the wide range o f commercial products available. This paper reports t he results of outdoor tests conducted on natural an d forced convection heat pipe solar hot wat...
IOP Conference Series: Earth and Environmental Science, 2021
In the present study, a numerical model of photovoltaic thermal (PV/T) system using alumina (Al2O... more In the present study, a numerical model of photovoltaic thermal (PV/T) system using alumina (Al2O3) nanofluid, and pure water are used as working fluid. The proposed PV/T model consists of parallel riser tubes that are connected to two header tubes and it is attached to an absorber plate to simulate the conduction and convection heat transfer mechanism of a conventional PV/T system. The energy efficiency of the PV/T model is analyzed by varying the solar radiation (Heat Flux), inlet fluid velocity, and the volume percentage of the nanofluids. The numerical simulation is performed by using a conjugate heat transfer method with a computational fluid dynamics (CFD) software. According to the simulation data, the energy efficiency and the heat transfer coefficient of the PV/T system increased by increasing the inlet fluid velocity. In comparison with water, alumina nanofluid showed better thermal and electrical efficiency due to its high thermal conductivity. The thermal efficiency incr...
Nucleation and Atmospheric Aerosols, 2017
A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat ef... more A heat pipe is a passive heat transfer device capable of transferring a large quantity of heat effectively and efficiently over a long distance and with a small temperature difference between the heat source and heat sink. A heat pipe consists of a metal pipe initially vacuumed and then filled with a small quantity of fluid inside. The pipe is separated into a heating (evaporator) section and a cooling (condenser) section by an adiabatic section. In a run-around-coil heating, ventilation and air conditioning system, a wrap-around heat pipe heat exchanger could be employed to increase dehumidification and to reduce cooling costs. The thermal performance of a thermosyphon is dependent upon type of fill liquid, fill ratio, power input, pipe inclination and pipe dimensions. The boiling and condensation processes that occur inside a thermosyphon are quite complex. During operation, dry-out, burn-out or boiling limit, entrainment or flooding limit and geysering occur. These phenomena would lead to non-uniform a...
Drying Technology, Apr 1, 1999
... 4. Hildebrand, R., 1970, "Kiln drying of sawn timber", Roben Hilderbrand Co... more ... 4. Hildebrand, R., 1970, "Kiln drying of sawn timber", Roben Hilderbrand Corp. 5. Langrish. T. A. G. and RB Keey, 1991. "A solar heated kiln for drying New Zealand hardwoods", Trans. Inst. ... 18(2), 10-26. l 1 . Taylor. K. I. and AD Weir. 1985, "Simulation of solar linlber drier". ...
Elsevier eBooks, 1980
Solar energy provides a source of non-polluting and virtually inexhaustible energy supply which c... more Solar energy provides a source of non-polluting and virtually inexhaustible energy supply which could be harnessed relatively cheaply and easily for domestic, commercial, industrial and agricultural applications. The practical utilisation of solar energy in rural farming areas in Malaysia is mainly for crop and timber drying. Some feasible solar crop drying systems are discussed. A programme for research and development on solar drying technology for rural development is outlined.
Heat Transfer Engineering, Nov 1, 2010
Experimental investigations were conducted to determine the thermal performances of an R-134a-fil... more Experimental investigations were conducted to determine the thermal performances of an R-134a-filled thermosyphon heat pipe heat exchanger (THPHE) and a water-filled loop heat pipe heat exchanger (LHPHE) for hot and cold energy recovery for air conditioning purposes. For such applications, the heat pipe heat exchangers are operated at low temperatures. Both exchangers were operated in the countercurrent flow mode. This article presents the experimental results obtained. The results showed that heat transfer rate increased as evaporator inlet temperature increased and as both evaporator and condenser velocities increased. The overall effectiveness for the THPHE ranged from 0.8 to a minimum of about 0.5, while for the LHPHE it ranged from 0.9 to 0.3. Overall effectiveness was found to approach a minimum when both air streams have equal velocities.
Polymers, Jun 18, 2017
In this study, reduced graphene oxide (RGO)/polymethyl methacrylate (PMMA) nanocomposites were pr... more In this study, reduced graphene oxide (RGO)/polymethyl methacrylate (PMMA) nanocomposites were prepared by employing in situ polymerization and solution blending methods. In terms of mechanical properties, RGO loading increased the Young's modulus but decreased the elongation at break for RGO/PMMA nanocomposites. Tensile strength for solution blended RGO/PMMA nanocomposites increased after adding 0.5 wt % RGO, which was attributed to the good dispersion of RGO in the nanocomposites as evidenced from SEM and TEM. Solar energy conversion efficiency measurement results showed that the optimum concentration of RGO in the RGO/PMMA nanocomposites was found to be 1.0 wt % in order to achieve the maximum solar energy conversion efficiency of 25%. In the present study, the solution blended nanocomposites exhibited better overall properties than in situ polymerized nanocomposites owing to the better dispersion of RGO in solution blending. These findings would contribute to future work in search of higher conversion efficiency using nanocomposites.
Applied Thermal Engineering, Aug 1, 2016
Abstract The thermal performances of a R410A filled thermosyphon subjected to low power input fro... more Abstract The thermal performances of a R410A filled thermosyphon subjected to low power input from 40 to 100 W and evaporator wall temperatures between 25 °C and 50 °C with fill ratios between 0.50 and 1.00 and at different inclinations from 30° to 90° were investigated. The axial temperature distribution of the thermosyphon was found to be quite uniform at all temperatures with the exception of the bottom end of the evaporator at all power input. The performance of the thermosyphon determined from the heat transfer resistance of the thermosyphon was found to be independent of fill ratio and inclination. Comparisons with other investigators using water, R410A and R134a would seem to indicate that a lower aspect ratio resulted in higher resistance and thus lower thermal performance.
IOP Conference Series: Earth and Environmental Science, 2021
The temperature of a PV panel rises during operation which affects its power output. A PV panel i... more The temperature of a PV panel rises during operation which affects its power output. A PV panel is similar to a flat plate solar collector. This paper presents a simple theoretical heat transfer resistance model and a solution procedure to predict the absorber plate surface temperature of the solar collector. The model consisted of a rectangular cross-section steel duct placed inclined at an angle to the horizontal and exposed to solar radiation. The heat absorbed on the top surface of the plate is transmitted by conduction through the plate and heats the air in the duct. This creates a natural buoyancy effect which induces a natural convection air flow rate. A simple one-dimensional theoretical model of the solar collector with the thermal resistances of the various components is proposed. Simulated results of plate temperature and induced air flow velocity are presented.
IOP Conference Series: Earth and Environmental Science, 2021
This study investigates the effect of inclination angle of a flat plate solar air collector in Ka... more This study investigates the effect of inclination angle of a flat plate solar air collector in Kampar, Malaysia. Flat plate solar air collectors have been investigated since the early 1950s for air heating and crop drying. Their performances under natural convection air cooling are very similar to a photovoltaic (PV) panels for power production. A PV panel becomes hot when operating under hot weather which will affect the efficiency and lifespan. The panel could be cooled down by providing an air duct underneath which allowing natural convection air circulating inside the duct. The degree of cooling would depend upon the angle of inclination of the panel. This paper presents some experimental results on the effect of inclination angle on the performance of a flat plate solar air collector under natural convection air cooling.
IOP Conference Series: Materials Science and Engineering, 2020
Main barriers for installation of conventional solar water heating system (SWHS) are requirement ... more Main barriers for installation of conventional solar water heating system (SWHS) are requirement of large installation area and heavy weight of the heat storage tank consisting water. A storage tank with minimum capacity of 230 liters are needed for household usage and this tank when empty can weigh up to 100 kg while a filled tank could weigh up to 400 kg. In reality, installation of this conventional system require more space and heavy structural support on the roof, which is not available in most houses. As a solution, a form stable light harvesting phase change material (FSLHPCM) integrated compact system is proposed. This new SWHS consists of glass – topped collector cum storage tank filled with FSLHPCM. This new FSLHPCM is form stable, does not leak and exhibit stable latent heat when tested to 1000 thermal cycles. It is capable to not only store heat but can improve the collector efficiency by harvesting the visible light and converting it to heat. The additional light to hea...
Solar Energy, 1974
The theoretical performance of a solar water heater operating under thermosiphon-flow conditions ... more The theoretical performance of a solar water heater operating under thermosiphon-flow conditions was evaluated using a finite-difference solution procedure. Tests were conducted on an experimental heater which incorporated a flat-plate collector design. Experimental water mass flow rates were measured at half-hour intervals using a dye-injection method while the temperature distribution of the system was monitored continuously. Some defects in the theory arising from inaccurate assumptions of the mean temperatures of the various components of the system are pointed out. Fortunately, these defects are significant only during the early and late periods of the day. Throughout the main insolation period, satisfactory qualitative and quantitative agreement can be obtained between experimental and theoretical results. A proposal for future study to investigate the reverse-flow phenc, ena is introduced.
International Journal of Productivity and Quality Management, 2022
We report an extended surface technique that utilises micro-fin arrays to enhance the heat transf... more We report an extended surface technique that utilises micro-fin arrays to enhance the heat transfer performance in the microchannels at Reynolds number ranging from 400 to 1000. Three different types of microfins namely Case A (cylindrical micro-fin), Case B (offset cylindrical micro-fin) and Case C (diverge cylindrical micro-fin) are designed. A comparative study between the three cases and bare rectangular microchannel was conducted. The technique enhances the thermal dissipation rate while keeping the pressure drop at a satisfactory level through proper design configurations. Numerical study has been performed in order to elucidate the single phase heat transfer phenomena in the present study.
International Journal of Productivity and Quality Management, 2021
Proceedings of ISES World Congress 2007 (Vol. I – Vol. V), 2008
... In order to assist in providing a comfortable and cool environment inside the house, removal ... more ... In order to assist in providing a comfortable and cool environment inside the house, removal of the hot air in the ceiling and reducing the ... Hamdy and Fikry [12] showed that the optimum tilt angle for a solar air heater connected in series with a vertical solar chimney was at 60 o ...
Solar Energy, 2003
A mathematical model of a solar chimney was proposed in order to predict its performance under va... more A mathematical model of a solar chimney was proposed in order to predict its performance under varying ambient and geometrical features. Steady state heat transfer equations were set up using a thermal resistance network and solved using matrix inversion. Existing correlations of heat transfer coefficients were utilised. Property values for the air flow in the duct were based on mean bulk or film temperatures. The performance of the chimney was evaluated by predicting the temperatures of the glass glazing and the heat-absorbing wall and also the temperature and velocity of the induced air flow in the chimney. The effects of air gap and solar radiation intensity on the performance of different chimneys were investigated. In order to verify the theoretical model, experiments were conducted on a 2 m high30.45 m wide physical model with air gaps of 0.1, 0.2 and 0.3 m. Experiments were carried out outdoors on the roof and the experimental model exposed to both 21 21 22
System performance of a solar water heater depends upon collector and storage tank design (dimens... more System performance of a solar water heater depends upon collector and storage tank design (dimensions, insulation, pipe connections, etc.) and weather con ditions (solar radiation intensity and ambient temp rature). Nocturnal reverse flow and tank insulation dictate th degree of overnight water temperature drop in t he storage tank. A tropical country like Malaysia has widely fluctuating and intermittent solar radiation . It is neither practical nor feasible to conduct outdoor t ests such as that proposed by International Standar ds. Indoor collector tests are expensive to conduct and would not provide meaningful information to the domestic or commercial end user. Outdoor system tes ts would be more informative to consumers who would like to compare the water temperatures that could b e achieved in order to choose from the wide range o f commercial products available. This paper reports t he results of outdoor tests conducted on natural an d forced convection heat pipe solar hot wat...
IOP Conference Series: Earth and Environmental Science, 2021
In the present study, a numerical model of photovoltaic thermal (PV/T) system using alumina (Al2O... more In the present study, a numerical model of photovoltaic thermal (PV/T) system using alumina (Al2O3) nanofluid, and pure water are used as working fluid. The proposed PV/T model consists of parallel riser tubes that are connected to two header tubes and it is attached to an absorber plate to simulate the conduction and convection heat transfer mechanism of a conventional PV/T system. The energy efficiency of the PV/T model is analyzed by varying the solar radiation (Heat Flux), inlet fluid velocity, and the volume percentage of the nanofluids. The numerical simulation is performed by using a conjugate heat transfer method with a computational fluid dynamics (CFD) software. According to the simulation data, the energy efficiency and the heat transfer coefficient of the PV/T system increased by increasing the inlet fluid velocity. In comparison with water, alumina nanofluid showed better thermal and electrical efficiency due to its high thermal conductivity. The thermal efficiency incr...
Operational Research and Analytics in Practice: Theory, Methods, and Applications (ISBN no. 978-967-2792-40-6) , 2023