Papers by Dr. Audai Hussein Al-Abbas
Journal of Techniques, Dec 18, 2023
The use of wickless heat pipe heat exchangers has been improving a wide range of thermal applicat... more The use of wickless heat pipe heat exchangers has been improving a wide range of thermal applications such as solar water heaters. Therefore, more scientific research needs to be conducted to improve its performance. In the present study, a wickless heat pipe heat exchanger test rig has been designed and fabricated to investigate the effect of different parameters on its performance. Two different heat pipe working fluids have been used namely pure water and water with nanoparticles (Al2O3) using different fluid volume ratios (20%,40%,60%,80%, and 100%). The concentrations of the nanoparticles in water range between 1.3 and 7 % wt. For the heat exchanger, various inlet hot air temperatures (50, 55, and 60 o C) have been tested at the hot side (heat pipe evaporator) whereas the inlet temperature of the cold side (heat pipe condenser) has been maintained at 20 o C. The effect of airflow Reynolds number has also been examined with a range of 2583-20664. Results showed that the best heat exchanger effectiveness is achieved at a Reynolds number of 10332 and nanoparticles concentration of 7% wt. Also, the use of nanoparticles reduced the thermal resistance in the heat pipe due to the significant reduction in its surface temperature compared to that of pure water.
International Journal of Applied Science and Engineering, Dec 31, 2022
This experimental study investigates the use of R1234-yf and ethanol as working fluids in a wickl... more This experimental study investigates the use of R1234-yf and ethanol as working fluids in a wickless heat pipe, with air flowing through the heat exchanger ducts. The hot air temperatures were set at 50°C, 55°C and 60°C, while the cold air temperature was fixed at 20°C. Both hot and cold air streams were pumped with Reynolds numbers ranging from 2583 to 20664. The wickless heat pipe was oriented vertically and filled with varying filling ratios of 20%, 40%, 60%, 80% and 100%. The results demonstrate that the wickless heat pipe -heat exchanger achieved the best thermal performance of 0.181 at a filling ratio of 60%, using ethanol as the working fluid and a Reynolds number of 10332. Additionally, a novel approach is proposed to predict the overall thermal performance of the wickless heat pipe -heat exchanger, and the predicted results show good agreement with the experimental findings
Frontiers in Heat and Mass Transfer, Mar 25, 2023
Transferring thermal energy efficiently necessitates utilizing a heat exchanger capable of produc... more Transferring thermal energy efficiently necessitates utilizing a heat exchanger capable of producing the full thermal power of the energy supply at lowest possible cost and time. Therefore, in the present investigation, the impact of corrugated helical coil concentric tube-in-tube heat exchanger on the thermal performance is investigated experimentally. As a continuous in our issue of heat exchanger, the corrugated helical tube-in-tube is carried out and compared with smooth helical tube-in-tube for free convection heat transfer. The setup of the experimental apparatus are designed and utilized to be appropriate for the cooling and heating systems of working fluid. The impacts of geometry and operating conditions on the thermal and hydraulic characteristics such as the thermal effectiveness, whole coefficient of heating-transfer, number of thermal unit, pressure drop, Number of Dean and Number of Nusselt are taken into consideration of this investigation. The steady state flow condition and the counter flow direction are assumed in this investigation. The experimental results demonstrated that the whole coefficient of heating-transfer, effectiveness, number of thermal units, and Number of Nusselt were improved significantly due to the adoption of the corrugated helical coil tube-in-tube heat exchanger. This is happened because of the impact of geometrical configuration of corrugated tube in comparison with that of smooth tube, which is affected on increasing of the coefficient of heating-transfer. The maximum enhancement magnitude of the whole coefficient of heating-transfer was 33% for water flow rate of 16 L/min. For the latter water flow rate, effectiveness found that the maximum enhancement was 35%. The high magnitudes of NTU and Number of Nusselt were 3.37 and 218.5, respectively at the corrugated coil tube-in-tube for 16 L/min of hot water flow rate. The pressure drop for the corrugated tube was higher than that of smooth tube due to the swirl flow of hot water inner tube.
International Journal of Thermal Sciences, 2016
Procedia Engineering, 2013
In the present paper, a computational fluid dynamics (CFD) modelling study was performed for the ... more In the present paper, a computational fluid dynamics (CFD) modelling study was performed for the combustion of the brown coal in a large-scale tangentially-fired furnace (550 MW) under different operating conditions. The AVL Fire CFD code has been used to model the furnace. The mathematical models of coal combustion with the appropriate kinetic parameters were written and added to the code as user defined functions. It consists of pulverised coal (PC) devolatilization, char burnout, heat and mass transfer, and nitric oxide formation. The simulation of the PC combustion was carried out using multi-step reaction chemistry schemes. The level of confidence of this numerical model was based on the previous validations of the lignite combustion in a lab-scale furnace, as well as the validation parameters of the present furnace at the standard existing conditions in terms of temperature values and species concentrations. Performance of the boiler under different operating conditions was investigated, from which the effects of air and coal mass flow rates were considered at full load with different operating schemes of coal mills (out-of-service operations). The validated model was used to perform the following investigation parameters: furnace gas temperatures, species concentrations (CO and CO 2 ), and velocity distributions. This study provides good information to optimize the operations of the utility tangentially-fired boiler with less emissions production.
Procedia Engineering, 2013
This paper presents a computational fluid dynamics (CFD) modelling study to investigate Victorian... more This paper presents a computational fluid dynamics (CFD) modelling study to investigate Victorian brown coal combustion in a 550 MW utility boiler under the air-fired (standard) and three oxy-fuel-fired cases. The standard case was modelled based on the real operating conditions of Loy Yang A power plant located in the state of Victoria, Australia. A level of confidence of the present CFD model was achieved validating four parameters of the standard combustion case, as well as the previous preliminary CFD studies which were conducted on a lab-scale (100 kW) unit firing lignite and propane under oxy-fuel-fired scenarios. The oxy-fuel combustion cases are known as OF25 (25vol. % O 2 concentration), OF27 (27vol. % O 2 concentration), and OF29 (29vol. % O 2 concentration). The predictions of OF29 combustion case were considerably similar to the standard firing results in terms of gas temperature levels and radiative heat transfer compared with OF25 and OF27 combustion scenarios. This similarity was because of increasing the residence time of pulverised coal (PC) in the combustion zone and O 2 concentration in feed oxidizer gases. Furthermore, a significant increase in the CO 2 concentrations and a noticeable decrease in the nitric oxides (NO x ) formation were noted under all oxy-fuel combustion conditions. This numerical study of oxy-fuel combustion in a full-scale tangentially-fired PC boiler is important prior to its execution in real-life power plants.
Numerical investigation of pyrolysis of a Loy Yang coal in a lab-scale furnace at elevated pressures
Heat and Mass Transfer, 2013
ABSTRACT A computational fluid dynamics (CFD) model of the pyrolysis of a Loy Yang low-rank coal ... more ABSTRACT A computational fluid dynamics (CFD) model of the pyrolysis of a Loy Yang low-rank coal in a pressurised drop tube furnace (pdtf) was undertaken evaluating Arrhenius reaction rate constants. The paper also presents predictions of an isothermal flow through the drop tube furnace. In this study, a pdtf reactor operated at pressures up to 15 bar and at a temperature of 1,173 K with particle heating rates of approximately 105 K s−1 was used. The CFD model consists of two geometrical sections; flow straightner and injector. The single reaction and two competing reaction models were employed for this numerical investigation of the pyrolysis process. The results are validated against the available experimental data in terms of velocity profiles for the drop tube furnace and the particle mass loss versus particle residence times. The isothermal flow results showed reasonable agreement with the available experimental data at different locations from the injector tip. The predicted results of both the single reaction and competing reaction modes showed slightly different results. In addition, several reaction rate constants were tested and validated against the available experimental data. The most accurate results were being Badzioch and Hawksley (Ind Eng Chem Process Des Dev 9:521–530, 1970) with a single reaction model and Ubhayakar et al. (Symp (Int) Combust 16:427–436, 1977) for two competing reactions. These numerical results can provide useful information towards future modelling of the behaviour of Loy Yang coal in a full scale tangentially-fired furnace.
Energy & Fuels, 2012
A computational fluid dynamics (CFD) modeling study has been carried out. The study involved gase... more A computational fluid dynamics (CFD) modeling study has been carried out. The study involved gaseous fuel combustion with associated chemical reactions, radiative heat transfer, and turbulence. The three different combustion environments that were adopted experimentally in a 100 kW drop-tube firing unit were examined. One air-fired and two oxy-fuelfired cases [21 vol % O 2 for one combustion case (OF21) and 27 vol % O 2 for the other combustion case (OF27)] were investigated. A swirl injection system was used to achieve the flame stability of the turbulent non-premixed combustible gases. A modified eddy breakup (EBU) model was used with appropriate empirical coefficients for propane combustion reactions. The irreversible single-step and reversible multi-step reaction mechanisms were considered. The overall agreement of the CFD results with the available measured data was reasonable. The data compared were the temperature distributions and the species concentrations (CO 2 , CO, and O 2 ) at the most intensive combustion locations in the furnace. The luminous appearance and temperature levels of the OF27 flame were relatively close to the reference (air-fired) flame. This was due to a reduced volumetric flow rate and an increase in the O 2 concentration in the gas mixture. The carbon dioxide concentrations for both oxyfuel-fired scenarios were around 8 times higher than that of the air-fired combustion case. The results obtained with the multistep chemistry mechanism showed improved agreement, particularly in the flame zone. The concentration of CO was lower in the OF21 case. The unburnt fuel in the air-fired and OF27 cases was less than that of the OF21 case because of the low oxygen concentration used in the latter combustion case. This study can provide a basis for the future investigation of combustion characteristics in a large-scale furnace under oxy-fuel-firing conditions.
Thermal Power Plants - Advanced Applications, 2013
IOP Conference Series: Materials Science and Engineering
Computational Fluid Dynamics CFD modeling study was carried out to investigate the effect of the ... more Computational Fluid Dynamics CFD modeling study was carried out to investigate the effect of the pin fins arrangements over the flat plate heat sink. The pin fins were adopted with in-line array form over the surface of the heat sink with different parameters. The CFD domain was designed by the use of ANSYS FLUENT 2019 R1 commercial software. The Reynolds Average Naiver Stoke RANS turbulent model was used in this study to show accurately capture the effect of alternating acceleration and deceleration and consequent variations in the pressure field. The heat sink is in a rectangular shape with a rib length of 100mm and100mm. This CFD investigation included a simulation of the proposed heat sink under the forced convection with Reynolds number range of 2166.67 ∼ 19500 and subjected heat flux of 1000W/m2. Pin fins diameters range were 3, 6 and 9mm while the fin lengths range were 5, 10 and 15mm under the same the heat flux and Reynolds number. The predicted results showed an augmentati... 
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Papers by Dr. Audai Hussein Al-Abbas