2022-10

Gongcheng Kexue Yu Jishu/Advanced Engineering Science (Issue : 6) (Volume : 54)

Air-water two-phase flow development in a vertical pipe has been investigated through service of experiments and simulations in this research. Differential Pressure Transducers (DPTs) and Wire Mesh sensors (WMSs) are used to monitor the two-phase flow in a vertical pipe of 67 mm inlet diameter and 7000 mm length. Computational Fluid Dynamic (CFD) is used to evaluate the experiments of the air-water flow in the vertical pipe using a volume of fluid (VOF) model. The operating conditions cover a range of inlet air superficial velocities from 0.05 to 5 m/s. The inlet water superficial velocity remains constant at 0.2m/s and 0.4 m/s for all experiments. The results show that the bubbly flow is noted at low superficial velocities of gas, slug flow is observed at the moderate flow rates of gas, while the churn flow pattern is observed at high rates of gas. There is no significant effect when the Usl changed from 0.2 m/s to 0.4 m/s on the vertical flow lines. Pressure drop is recorded and compared with the CFD simulations. The CFD results are over estimation compared with the experimental pressured drop with maximum absolute error of 21% at Usl of 0.2 m/s and 25% at Usl 0.4 m/s.

2022-10

Gongcheng Kexue Yu Jishu/Advanced Engineering Science (Issue : 6) (Volume : 54)

In this paper, air distribution parameters inside the selected control room in cooling mode ventilated by cassette type air conditioner was analyzed. In this work, the investigation in both experimentally and numerically have been conducted. An proper control room was selected for experiment design with dimensions of 4.8m width, 5m length, and 3.55m height. Furthermore, the instrument devices for measuring the air temperature and air velocity were arranged and prepared. An ANSYS workbench software was utilized for CFD simulation to analysis the air distribution numerically and compare the results with experimental work. The same dimensions of the room and 4 way cassette air conditioner were used as physical modelling by ANSYS design modular. Mesh independence was applied to obtain the accurate data. Reynolds averaged Navier–Stokes equation (RANS) and the standard k-epsilon k-ε transport equations were utilized to estimate the streamline of the air inside a control zone. The outcomes revealed that average percentage error between predicted and empirical data was 8.88% for velocity readings and (7.6%, 2.8%, and 3.2%) for temperature results on (pole 1, pol 2, pole 3) respectively. As a result, we can state that the experimental data validate the numerical model.

2022-10

Journal of Bioresources and Bioproducts

An investigation was conducted to examine the impact of additive mixing with wheat straw (WS) for pellet making. This study manufactured seven types of pellets with different additive combinations to evaluate pellet quality characteristics and their relationships. A laboratory-type hammer mill and a pellet mill were used for feedstock preparation and pellet production. Experimental investigations showed that the lignin content increased from 7.0% to 13.1%, which was a primary need for pelletization. Also, the heating value rose from 17.02 to 20.36 MJ/kg. However, the ash content also increased from 7.09% to 16.2%. Results showed that dimension (length and diameter), durability, and tensile strength increased significantly with additives while the fines content decreased. The fines content had an inverse relationship with durability and strength. Wheat straw (60%), together with 10% sawdust (SD), 10% corn starch (CS), 10% bentonite clay (BC), and 10% biochar (BiC), was optimal with good pellet performance (T7). In addition, both the T5 pellets (70% WS, 10% SD, 10% BiC, and 10% BC) and the T6 pellets (70% WS, 10% SD, 10% BiC, and 10% CS) provide suitable quality according to EN plus 2015 standard requirements. The ash content of produced pellet was higher than the recommended value, which suggests that further research onto the alternative additive use for ash reduction is needed.

2022-09

Gongcheng Kexue Yu Jishu/Advanced Engineering Science (Issue : 6) (Volume : 54)

Experimental investigation to enhance the heat storage ability for the parabolic trough collector (PTC) is performed in this study. The performance of the PTC has been integrated with paraffin wax manufactured in Baghdad, Iraq. It has been evaluated experimentally based on the ANSI/ASHRAE 93-1986 standard. A special design for the heating water system is built with a continuous flow and a maximum temperature range of 65 oC. Water is used as the primary working fluid. The operation conditions include constant flow rate of 0.056 kg/s, direct solar radiation range from 120 w/m2 to 895 w/m2. The results show that with an incidence angle of 0, the highest efficiency for the collector is 0.82 %. The results also show that the paraffin wax has a crucial role to absorb the solar energy during the day and disperse the solar energy to the working fluid after sunset.

2022-07

International Journal of Heat and Technology (Issue : 3) (Volume : 40)

The steam condensation process has been experimentally investigated in an air-cooled condenser (ACC). The ACC has been designed and built using a flattened cross-section horizontal tube. The flattened tube has an internal dimension of 102 mm x 12 mm with 4030 mm length. A range of vacuum operating conditions are applied to operate the ACC. In the experiments, parameters such as vacuum pressure, saturated temperature, wall tube temperature, rate of heat transfer, and local average steam heat transfer coefficient have been considered along the flow direction with the variation of cooling water temperature. The experimental results revealed that the steam saturated temperature and the related pressure decrease with the reduction of the cooling water temperature, and the temperatures of the upper and lower parts of the horizontal flattened tube. The results also showed that the local steam condensation heat transfer coefficient decreases along with the direction of the flow, but it there is incrementing with the decreasing of saturated steam temperature at a certain range of cooling water temperature.

2022-06

Advanced Engineering Science (Issue : 4) (Volume : 54)

Performance of a hot water solar collector system has been investigated and assessed in this work. Solar energy is one of the essential natural energy sources that can be used to provide hot water for daily use in sustainable buildings. A mobile solar collector has been designed and built to assess the hot water solar collector system in different regions of Iraq. A flat plate solar collector with a helical coil heat exchanger has been used in this study. The average solar radiation has been predicted and measured. The results revealed that there is high performance of the solar water collector panel to produce hot water for buildings in Iraq. The maximum outlet temperature of the hot water of 54 ± 0.1 oC was recorded at the shell flow rate of 4 l/min and coil flow rate of 1 l/min. Maximum output energy of the solar collector system ranging from 13567 to 1488 ± 10.5 W/m2 was recorded at the range of ambient temperature from 10 to 49± 0.1 oC and sun intensity of 1890 W/m2 . The outcome of this work is a real database which will provide a good reference for future research and energy applications in Iraq.

2022-06

Fluid Dynamics and Materials Processing (Issue : 4) (Volume : 15)

This work investigates the steam condensation phenomena in an air-cooled condenser. The considered horizontal flattened tube has a 30 mm hydraulic diameter, and its length is a function of the steam quality with a limit value between 0.95 and 0.05. The mass flow rate ranges from 4 to 40 kg/m2.s with a saturated temperature spanning an interval from 40°C to 80°C. A special approach has been implemented using the Engineering Equation Solver(EES) to solve a series of equations for the two-phase flow pattern and the related heat transfer coefficients. A wavy-stratified structure of the two-phase flow has been found when the mass rate was between 4 and24 kg/m2.s. In contrast, an initially annular flow is gradually converted into a wavy stratified flow (due to the condensation process taking place inside the flattened tube) when the considered range ranges from 32 to 40 kg/m2.s.

2022-06

International Journal on “Technical and Physical Problems of Engineering (Issue : 51) (Volume : 14)

In order to more understanding the nature of physical phenomena, the simulations, mathematical equations and their solution are used to describe those physical phenomena. They also describe the combustion process with the help of mathematical and chemical equations for an ignition engine by spark. Alternative fuels and air are mixed at a molecular level prior to combustion which occurs as a flame front. This paper presents the combustion simulation of spark ignition for an engine with four-stroke cylinders and a compression ratio (12:1). Zero-dimension model is used to predict the speed of turbulent flame, and mixture (10%) of ethanol and gasoline expresses the fuel used in this study. The turbulent flame speed is predicted with different parity ratios (0.6-1.1), different engine speed (500-2500) RPM and different compression ratios (7:1 - 10:1) as well as the timing of the different spark timing up to (5-30 btdc), by using the visual basic program.

2021-10

International Journal of Heat and Technology (Issue : 5) (Volume : 39)

To improve the performance of vapor compression refrigeration systems that use vertical gravitational flash tank separators, the liquid separation efficiency of the vertical gravitational flash tank separator requires to be approved. To approach this improvement, the two-phase flow development and its behavior after the expansion device need to be investigated and predicted. For thus, this paper presents a three-dimensional computational investigation of the two-phase flow development of R134a after the expansion device in a horizontal pipe. Computational Fluid Dynamic (CFD) was used to predict the two-phase development and its behavior in the horizontal pipe. ANSYS 16.2 program was used to generates the geometry of the three-dimensional horizontal pipe of 2 meters long and 25 mm inner diameter. The hexahedral mesh was generated and it is assessed to obtain the optimum mesh size and number. Eulerian-Eulerian two-phase model was used with k-ɛ turbulence model. R134a was used as a working fluid in the horizontal pipe utilizing four different inlet diameters: 12, 12.5, 25, and 50.0 mm. Mass flux and vapor quality have been changed from 288 to 447 kg/m2 .s and from 10 to 20% respectively. Results were validated against experimental results from the literature and revealed that the separation region length is affected by the initial phase velocities, inlet vapor quality, and inlet tube diameter. An empirical correlation to predict the expansion region length is proposed as a function of Froude, Webber, and Lockhart-Martinelli numbers.

2021-09

Int. J. of Applied Mechanics and Engineering, (Issue : 3) (Volume : 26)

Reducing energy consumption and providing high performance for a vapour compression refrigeration system are big challenges that need more attention and investigation. This paper provides an extensive review of experimental and theoretical studies to present the vapour compression refrigeration system and its modifications that can be used to improve system’s performance and reduce its energy consumption. This paper also presents the challenges that can be considered as a gab of research for the future works and investigations. Cooling capacity, refrigerant effect, energy consumption can be improved by using vapour injection technique, natural working fluid, and heat exchanger. Based on the outcome of this paper, vapour injection technique using natural refrigerant such as water can provide ultimate friendly refrigeration system. Future vision for the vapour compression refrigeration system and its new design technique using Computational Fluid Dynamic (CFD) is also considered and presented.

2021-06

TECHNIUM (Issue : 5) (Volume : 3)

Two-phase flow behaviour and its flow patterns have a significant effect in many applications in industry. Oil-gas is one of the two-phase flow types that have many applications in petroleum and power stations. An oil-gas two-phase flow behaviour and flow patterns have been investigated in an inclined pipe using two different tomography sensors: Wire Mesh sensor (WMS) and Electrical Capacitance Tomography (ECT). A special experimental facility was designed and built to operate the tow-phase flow application in the inclined pipe with the various angle of inclination. A set of experimental data were collected using operating conditions which covered a two-phase flow range of superficial velocity of gas (Usl) from 0.05 to 0.52 m/s and superficial velocity of liquid (Usg) from 0.05 to 4.7 m/s at atmospheric pressure and room temperature. Three inclined angles to change the pipe’s inclination 45, 60, and 80-degree were applied in the experiments. The Comparison between the Wire Mesh Sensor (WMS) and Electrical Capacitance Tomography (ECT) was completed experimentally. The results revealed that there is a good agreement between the two sensors, however; the WMS had a higher frequency which was calculated 1000 frames per second compared with the ECT which worked at 200 frames per second.

2021-04

International Journal of Heat Transfer and Technology (Issue : 2) (Volume : 39)

The current investigation aimed to identify pressure gradients and to study the fully developed flow patterns of oil-gas as a blend in a pipe of internal diameter 50 mm and 6 m length with different orientations of 0, 30, and 45-degree. The study was performed at constant values of liquid superficial velocities 0.052, 0.157, 0.262, 0.314, 0.419, and 0.524 m/s, and inlet superficial velocities of gas were ranged from 0.05 to 4.7 m/s at atmospheric pressure. Two pressure transducers located up and downstream were used to measure pressure drops inside the tested pipe. Flow patterns were derived by using the correlation between pressure gradients and time series, the Probability Density Function of differential pressures, pressure gradients with gas superficial velocities, and total pressure losses with mean void fractions. The flow patterns of oil-gas were observed as a uniform stratified flow in the pipe on a 0-degree orientation at various superficial velocities. Stratified, wavy, and slug flow patterns were observed at 30-degree orientation, whereas, bubbly, slug, and churn flow patterns were observed in the pipe of 45-degree orientation. The experiment also showed that pressure drop gradients decreased with increased void fractions, gas superficial velocities, and degree rotations of the flow lines. Finally, the validation of using pressure transducers as a technique for estimating the flow patterns of two-phase flow showed acceptable results with some kind of patterns. The current investigation aimed to identify pressure gradients and to study the fully developed flow patterns of oil-gas as a blend in a pipe of internal diameter 50 mm and 6 m length with different orientations of 0, 30, and 45-degree. The study was performed at constant values of liquid superficial velocities 0.052, 0.157, 0.262, 0.314, 0.419, and 0.524 m/s, and inlet superficial velocities of gas were ranged from 0.05 to 4.7 m/s at atmospheric pressure. Two pressure transducers located up and downstream were used to measure pressure drops inside the tested pipe. Flow patterns were derived by using the correlation between pressure gradients and time series, the Probability Density Function of differential pressures, pressure gradients with gas superficial velocities, and total pressure losses with mean void fractions. The flow patterns of oil-gas were observed as a uniform stratified flow in the pipe on a 0-degree orientation at various superficial velocities. Stratified, wavy, and slug flow patterns were observed at 30-degree orientation, whereas, bubbly, slug, and churn flow patterns were observed in the pipe of 45-degree orientation. The experiment also showed that pressure drop gradients decreased with increased void fractions, gas superficial velocities, and degree rotations of the flow lines. Finally, the validation of using pressure transducers as a technique for estimating the flow patterns of two-phase flow showed acceptable results with some kind of patterns.

2021-02

Thermal Science (Issue : 1)

Natural and mixed convection heat transfer from a horizontal cylinder placed in a vented square enclosure has been investigated using numerical method with ANSYS Fluent 16.1 software for laminar and turbulent flow. Navier- Stokes equations and energy equation with standard k-ω transport equation turbulence model have been used to simulate both flow and thermal behaviors. The operating conditions covered a range of the Rayleigh number from 103 to 106 and the Richardson number range between 0.1 and 100 at variable sizes of the lower open vent with constant upper opening size. The Nusselt numbers, velocity lines and isotherms are presented to display the flow and thermal behaviors. The results displayed that the average Nusselt number is affected by Rayleigh number, Richardson number, enclosure width and lower opening size. The Nusselt number is enhanced by controlling the lower opening size. The maximum enhancement range for Nusselt number is between 20-85% depending on the Rayleigh number, Richardson number, enclosure width to cylinder diameter, and lower opening size. The velocity lines and isotherms are directly affected by the Rayleigh number, Richardson number, enclosure width to cylinder diameter, and lower opening size.

2021-01

Journal of Thermal Engineering (Issue : 1) (Volume : 7)

To optimize a vertical flash tank separator, the characteristics of the flow entering the separator are required to be known. A flash tank separator improves the performance of a refrigeration cycle by separating the liquid from liquid-gas flow and providing the evaporator with only liquid refrigerant. This technique improves the effective area and enhances the heat transfer coefficient in the evaporator. This paper investigates the influence of the inlet operating conditions to an expansion device, on the adiabatic two-phase flow development in a horizontal pipe downstream from the expansion device. This work also compares three dimensional numerical simulations and experimental observations for the two-phase flow development after the expansion device in the horizontal pipe. A general trend of the two-phase flow after the expansion device was gradually developed and the expansion length was identified at less than 200 mm from the inlet. The two-phase flow behaviour was recorded using a digital camera recording the flow behaviour at the upstream and downstream of the horizontal tube. The results revealed that an increase of the mass flow rate causes an increase in the void fraction and a reduction in the slip ratio in the developed region. The simulations underestimate the expansion length and the mean difference between the experimental data and the numerical results is 8 %

2021-01

Revista de Chimie (Rev. Chim.), (Issue : 12) (Volume : 71)

The air-water two-phase flow plays an important role in many applications of industry fields. Usually, a 90-degree bend is used to connect pipes for changing the direction of flow which influences the two-phase flow pattern. In this paper, the effect of 90-degree bend under different ranges of gas and liquid superficial velocities on the two-phase flow patterns in the horizontal pipe located after the bend was experimentally investigated, and then results were presented and compared in a two-phase flow pattern map. Also, tomographic images and probability density functions were used to capture the cross-section void fraction and its distribution for the two-phase flow patterns. The results revealed that at low liquid and gas flow rates, a stratified-wavy flow pattern was observed as a dominant flow pattern. While the wavy-annular and semiannular flow patterns were observed at a high range of gas flow rates in the horizontal pipe. The results also showed that at the high range of liquid flow rate, bubbly, plug, slug, stratified-wavy, and wavy-annular flow patterns were observed in the horizontal pipe when the gas flow increased. The tomographic images and probability density functions gave good agreement with the experimental observations and results.

2020-12

International Journal of Applied Mechanics and Engineering (Issue : 4) (Volume : 25)

In Australia and others developed countries, concerns about global warming have increased, and these concerns influence the use of refrigerants as working fluids in mechanical vapour compression refrigeration systems. One of the most important aspects of refrigerant selection is to reduce its impact on the environment and the ozone layer. This paper provides a comprehensive review of various theoretical and experimental studies which have been carried out on air conditioning and refrigeration applications to investigate the effect of refrigerants on the environment. The analysis in this paper reveals that alternative refrigerants are the most suitable working fluids that can be used in refrigeration systems to meet the needs of the environment. This study also suggests that natural types of refrigerants such as water, carbon dioxide, and hydrocarbon will play a significant role in protecting the environment and providing alternative friendly refrigerants to be used in refrigeration and air conditioning systems.

2020-08

International Journal of Air-Conditioning and Refrigeration (Issue : 3) (Volume : 28)

Three design enhancement options for a vertical gravitational °ash tank separator were proposed and investigated in this work. Computational Fluid Dynamic (CFD) was used to assess the optimum con¯gurations of the vertical gravitational °ash tank separator. A series of experiments were performed to test the CFD proposed con¯gurations of the enhancement design options. This paper also assessed the usefulness of CFD in °ash tank design, and this is achieved through experiments and simulations on a range of relevant con¯gurations using water as the working °uid. The results revealed that the combination of the inlet °ow direction and extractor had a signi¯cant e®ect on the performance of the vertical °ash tank separator which increased by 2%. The results also revealed that there was a good agreement between the CFD simulations and experiments; the CFD simulations underestimated the liquid separation e±ciency by approximately 0.02 over the range of conditions tested.

2020-07

International Journal of Engineering & Technology (Issue : 3) (Volume : 9)

This paper investigates the effect of adding a liquid-suction heat exchanger on the performance of a mechanical refrigeration system using alternative refrigerants. Engineering Equation Solver (EES) was used to simulate a mechanical refrigeration system in two configurations: modified system with liquid-suction heat exchanger and system without liquid-suction heat exchanger. The results revealed that the liquid-suction heat exchanger has a significant effect on the system performance as it influences the subcooling and superheating temperatures. The results also showed that the highest value of the coefficient of performance (COP) was achieved by the modified system with refrigerant type R134a, COP was about 7% and 12% higher than that of refrigerants R600a and R22 respectively. It also presented that R600a has high response to increase the refrigerant effect when the liquid-suction heat exchanger is used. R600a is good alternative refrigerant and it can be used in the mechanical refrigeration system, but its COP is lower than that of R134a

2020-04

International Journal of Advances in Mechanical and Civil Engineering (Issue : 2) (Volume : 7)

In air conditioning and refrigeration, insulation materials are essential in building insulation to achieve high performance and reduce energy consumption. However, nowadays, environment concerns have been increased as a result of using petrochemical insulation materials. The petrochemicals insulation materials have a direct effect on the environment as a result of using non-renewable materials, fossil energy consumption, and to the disposal stage. Eco-friendly insulation materials are the solution to decrease the environment concerns and build a sustainable building. Eco-friendly insulation materials have been used in this work to assess and compare its effectiveness in building insulations. Four eco-friendly insulation materials which excited by the nature were used in wall insulation. The overall heat transfer coefficient U was used to assess and compare the insulation efficiency. The basic wall configuration was used in comparison. The results revealed that the eco-friendly insulation material have effective insulation efficiency and can be used to reduce the energy loss through a walls by 50%.

2019-04

International Journal of Management and Applied Science (Issue : 4) (Volume : 5)

A vertical gravitational flash tank separator can be used to increase the performance of a refrigeration cycle. Using the vertical gravitational flash tank separator improves the effective area and enhances the heat transfer coefficient inside the evaporator. However, the vertical gravitational flash tank separator still needs further investigation to improve its performance. This paper provides an investigation study to demonstrate the improvement of separation efficiency using an extractor inside the vertical gravitational flash tank separator. Computational Fluid Dynamic (CFD) was used to assess the optimum configuration and dimension of the extractor. A series of experiments were performed to test and confirm the proposed CFD configuration of the extractor design. The results revealed that the extractor had increased the separation efficiency by 2 %. The CFD simulations gave a good agreement with the experiments; however, all the simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested

2019-04

International Journal of Management and Applied Science (Issue : 4) (Volume : 5)

Two-phase flow separation has been investigated by many researchers due to its important role in the most industrial applications. In refrigeration and air conditioning systems, two-phase flow separation influence the system performance. So, many techniques have been used to separate liquid phase from gas-liquid two phase flow and consequently to improve a system performance. T-junction is one of the techniques that can be used to obtain effective two-phase separation. In order to investigate the two-phase flow separation in very simple way and obtain wide accurate range of results, computational work is the appropriate solution. Computational Fluid Dynamics (CFD) software is one of the most effective computational way that can be used to visualise two-phase flow separation and design two-phase flow separator. This paper presents an instruction of CFD simulation to predict and visualize the two-phase flow separation in vertical Tjunction and a comparison between the CFD results with the related experimental results to validate the CFD results. ANSYS 17.1 was used to carry out the simulation. The geometry of the T-junction was generated by the ANSYS modular design based on the dimensions of experimental test section, then lunched to the ANSYS meshing to generate a suitable mesh.

2019-04

International Journal of Management and Applied Science (Issue : 4) (Volume : 5)

In refrigeration and air conditioning systems, a vertical flash tank separator is one of the most important component that can be used to improve the system performance. Using vertical flash tank technique improves the effective area and enhances the heat transfer coefficient in the evaporator. However, enhancing and improving the performance of the vertical flash tank separator need further investigation. In order to provide an optimum configuration and performance, this paper provides experimental and numerical investigation of two-phase flow direction change effect on the performance of the vertical flash tank separator. Computational Fluid Dynamics (CFD) was used to assess the effect of flow direction change. Series of experiments were performed to test the CFD proposed configurations. The results revealed that the inlet flow direction has a significant effect on the performance of the vertical flash tank. The CFD simulations gave a good agreement with the experiments, all the simulations underestimated the liquid separation efficiency by approximately 0.02 over the range of conditions tested. ANSYS 17.1 was used to carry out the simulation. The geometry of the vertical flash tank separator was generated by the ANSYS modular design based on the dimensions of experimental test section, then lunched to the ANSYS meshing to generate a suitable mesh.

2019-02

International Journal of Air-Conditioning and Refrigeration (Issue : 1) (Volume : 27)

The °ash tank separator is one of the most important components that can be used to improve the performance of a refrigeration cycle by separating the liquid from the gas–liquid two-phase °ow and providing the evaporator with only liquid refrigerant. This technique increases the e®ective area and enhances the heat transfer coe±cient in the evaporator. To optimize the size of the vertical °ash tank separator for obtaining high separation e±ciency, the e®ect of the size of the vertical °ash tank separator needs to be considered. This paper investigates the e®ect of the size on the liquid separation e±ciency of the vertical °ash tank separator. This paper also assesses the usefulness of Computational Fluid Dynamic (CFD) in °ash tank design, and this is achieved through experiments and simulations on a range of relevant con¯gurations using water as the working °uid. The results revealed that the size has a signi¯cant e®ect on the liquid separation e±ciency, as the highest value was achieved by the largest size (VFT-V5). The CFD simulations give a good agreement with the experiments; all the simulations underestimated the liquid separation e±ciency by approximately 0.02 over the range of conditions tested