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research-article  
Ramanathan Velmurugan, Jaikumar Mayakrishnan, Induja S, Selvakumar Raja, Sasikumar Nandagopal and Dr. Ravishankar Sathyamurthy
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041878
The present investigation aims at analyzing various parameters of single cylinder 4-stroke CI engine fueled with Waste Cooking Oil Biodiesel (WCOB), Waste Cooking Oil Biodiesel Water Emulsion (WCOBE) while the engine is operated with a constant speed of 1500 rpm. Furthermore, an attempt is made to study the impact of nanofluids in the behavior of the engine fueled with WCOB blended with nanofluids (WCOBN50). This work also explored a novel method of producing nanofluids using one-step chemical synthesis method. Copper Oxide (CuO) nanofluids were prepared by the above mentioned method and blended with Waste Cooking Oil Biodiesel (WCOBN50) using ethylene glycol as a suitable emulsifier. Results revealed that Brake Thermal Efficiency (BTE) and Brake Specific Fuel Consumption (BSFC) of WCOBN50 are significantly improved when compared to WCOB and WCOBE. Furthermore, a higher reduction in Oxides of Nitrogen (NOx), Carbon Monoxide (CO), Hydrocarbon (HC), and smoke emissions were observed with WCOBN50 on comparison with all other tested fuels at different power outputs. It is also identified that one step chemical synthesis method is a promising technique for preparing nanofluids with a high range of stability.
TOPICS: Engines, Nanofluids, Biodiesel, Brakes, Thermal efficiency, Stability, Copper, Fuels, Nitrogen, Smoke, Water, Nitrogen oxides, Fuel consumption, Emissions, Carbon, Cylinders, Diesel engines, Emulsions
Discussion  
Asterios Pantokratoras
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041884
The present discussion concerns some doubtful results included in the above paper.
Technical Brief  
Pawan Karki, Ajay K Yadav and D. Arumuga Perumal
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041875
This study involves the effect of adiabatic obstacles on two-dimensional natural convection in a square enclosure using Lattice Boltzmann Method (LBM). The enclosure embodies square shaped adiabatic obstacles with one, two and four in number. The single obstacle in cavity is centrally placed whereas for other two configurations, a different arrangement has been made such that the core fluid zone is not hampered. The four boundaries of the cavity considered here, consists of two adiabatic horizontal walls and two differentially heated vertical walls. The current study covers the range of Rayleigh number (10^3 = Ra = 10^6) and a fixed Prandtl number of 0.71 for all cases. The effect of size of obstacle (Ø) is studied in detail for single obstacle. It is found that the average heat transfer along the hot wall increases with the increase in size (Ø) of obstacle until it reaches an optimum value and then with further increase in size, the heat transfer rate deteriorates. Study is carried out to delineate the comparison between the presences of obstacle in and out of the conduction dominant zone in the cavity. The number of obstacles (two and four) outside of this core zone shows that heat transfer decreases despite the obstacle being adiabatic in nature.
TOPICS: Natural convection, Cavities, Lattice Boltzmann methods, Heat transfer, Fluids, Heat conduction, Rayleigh number, Prandtl number
research-article  
Faisal Al-Malki
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041794
The aim of this paper is to examine the response of twin premixed flames formed in a counterflow configuration to the presence of an unsteady straining flow. We began by describing the problem mathematically using the thermo- diffusive model with constant density and then adopted a finite elements approach to solve the problem numerically. The study has shown that the role of flow on flame propagation is determined by three main parameters, namely: flow amplitude A, strain rate ? and fuel Lewis number Le F . For Le F = 1, the flow is seen to promote flame extinction, while Le F < 1 the flow clearly enhances the flame reactivity. Qualitatively, it has been shown that for Le F = 1, there exists a critical value of A (that varies with ?) below which the reactivity decreases monotonically with A. For small Le F < 1, on the other hand, the re- activity were seen to increase with A. For Le F > 1, however, a non-monotonic dependence, especially for small ?, is predicted
TOPICS: Flow (Dynamics), Computer simulation, Flames, Density, Finite element analysis, Fuels
research-article  
Rajneesh Kumar, Sourabh Khurana, Anoop Kumar and Varun Goel
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041683
The sharp corner significantly affects the flow through triangular duct. In the corners, flow gets stagnant and results in poor heat transfer. Therefore, in the present study, one corner of the duct is kept rounded with variable curvature radius values (Rc). The curvature radius is selected in such a way that, it varied from the minimum value (i.e. Rc=0.333?duct height; h) to a maximum value (i.e. Rc=0.67h). In addition to this, the combined effect of both rounded corner and dimple-shaped intrusion has also been studied on flow of air and heat transfer. ANSYS (Fluent) 12.1 software is used to perform numerical simulations and good match is observed between the simulated and experimental results. Due to rounded corner and dimple intrusions, velocity near the corner region has higher value in comparison to the conventional duct. The uniform temperature distribution is seen in the case of dimple intruded duct as compared to conventional and rounded corner duct. In comparison to conventional duct with Rc of 0.67h, the heat transfer increased 21-25%, 13-20%, and 5-8%, for the Rc value of 0.33h, 0.49h, and 0.57h, respectively, but, the combination of rounded corner and dimple-shaped intrusions gives more heat transfer by 46-94%, 75-127%, 60-110%, for the z/e value of 6, 10, and 14, respectively, with the Reynolds number increase from 5600 to 17700.
TOPICS: Fluid dynamics, Heat transfer, Corners (Structural elements), Ducts, Flow (Dynamics), Computer simulation, Reynolds number, Temperature distribution, Computer software
research-article  
Ales Vojacek, Vaclav Dostal, Tomas Melichar, Martin Rohde and Friedrich Gottelt
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041686
This technical paper presents results of an air cooled supercritical CO2 (sCO2) finned-tube sink heat exchanger (HX) performance test comprising wide range of variable parameters (26-166 °C, 7-10 MPa, 0.1-0.32 kg/s). The measurement covered both supercritical and subcritical pressures including transition of pseudocritical region in the last stages of the sink HX. The test was performed in a newly built sCO2 experimental loop which was constructed within SUSEN (Sustainable Energy) project at Research Centre Rez (CVR). The experimental set-up along with the boundary conditions are described in detail, hence the gained data set can be used for benchmarking of system thermal hydraulic codes. Such benchmarking was performed on the open source Modelica-based code ClaRa. Both steady-state and transient thermal hydraulic analyses were performed using the simulation environment DYMOLA 2018 on a state of the art PC. The results of calculated averaged overall heat transfer coefficients (using Gnielinsky correlation for sCO2 and IPPE or VDI for the air) and experimentally determined values shows reasonably low error of + 25 % and - 10 %. Hence, using the correlations for the estimation of the heat transfer in the sink HX with a similar design and similar conditions gives a fair error and thus is recommended.
TOPICS: Heat exchangers, Testing performance, Supercritical carbon dioxide, Errors, Steady state, Energy sustainability, Boundary-value problems, Heat transfer, Simulation, Transients (Dynamics), Design, Heat transfer coefficients
research-article  
Omid Ali Zargar, Rong Fung Huang and Ching Min Hsu
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4041685
The effects of acoustic excitation at resonance on the flame appearances, flame lengths, flame temperatures, and combustion product concentrations of combusting swirling dual-disk double-concentric jets were studied. The Reynolds number of the annular swirling air jet was varied, while it was fixed at 2500 for the central propane jet. The central fuel jet was acoustically forced by a loudspeaker, which was installed using downstream longitudinal irradiation. The central jet pulsation intensities were measured by a calibrated, one-component hot-wire anemometer. The instantaneous full-length and close-up flame images were captured to identify the characteristic flame modes. Long-exposure flame images were taken to measure the flame lengths. The axial and radial temperature distributions of flames were measured using a homemade, fine-wire R-type thermocouple. The concentrations of combustion products were measured by a gas analyzer. Four characteristic flame modes, blue-base wrinkled flame, yellow-base anchored flame, blue-base anchored flame, and lifted flame, were observed in the domain of central jet pulsation intensity and annular swirling jet Reynolds number. The lifted flame, which was formed at large central jet pulsation intensities, presented characteristics of a premixed flame due to significant mixing induced by violent, turbulent flow motions. It was short and stable, with high combustion efficiency and low toxic emissions, when compared with the unexcited flame and other excited characteristic flame modes, which presented characteristics of diffusion flame.
TOPICS: Resonance, Acoustics, Jets, Flames, Swirling flow, Excitation, Combustion, Reynolds number, Wire, Irradiation (Radiation exposure), Air jets, Fuels, Turbulence, Temperature, Temperature distribution, Thermocouples, Diffusion flames, Emissions, Loudspeakers, Disks
Errata  
Mohsen Ali Mandegari, Somayeh Farzad and Hassan Pahlavanzadeh
J. Thermal Sci. Eng. Appl   doi: 10.1115/1.4032332
TOPICS: Exergy, Optimization, Wheels

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