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Characterization of Natural Convection over an Elliptical Tubes Array AR 2.5 and PR 1.25 inside a Thermally Asymmetric Cavity of Various Clearance Ratio Stefanus Widhipratama; Budi Utomo Kukuh Widodo
JMES The International Journal of Mechanical Engineering and Sciences Vol 2, No 1 (2018)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v2i1.5167

Natural convection is the phenomenon of heat transfer due to the buoyancy force of fluid. One application of natural convection inside a vertical cavity is refrigerator condenser of circular cross-section tube. An experimental investigation is presented on natural convection of air over an array of elliptical tubes of AR 2.5 arranged vertically inside a thermally asymmetric cavity. One side of the cavity is insulated and the opposite side is exposed to ambient air. The distance between tubes, pitch ratio PR is constant at 1.25 where “a” is a half of tube major axis. The Clearance Ratio \textit{CR} which is the ratio between the distance of tubes array major axis to the insulated wall x and the width of the cavity y, is varied 0.4 and 0.6. The heat flux of the tube is maintained at 22.79 kW/m$^2$. It is found that the higher value of heat transfer coefficient is achieved on CR= 0.4.

Experimental and Numerical Studies of Natural Convection on Elliptical Tube in Thermal Asymmetric Cavity Angga Tegar Setiawan; Budi Utomo Kukuh Widodo; Nila Rahmawati
JMES The International Journal of Mechanical Engineering and Sciences Vol 2, No 2 (2018)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v2i2.6398

The characteristic of natural convection heat transfer in a thermally asymmetric cavity is influenced by temperature differences and space between the heat source and cavity wall. The heat source is any bluff body placed inside the cavity. This research used a heated elliptic tube as the heat source inside the cavity. The three tubes are of 2.5 aspect ratio (AR) in a vertically aligned arrangement. The cavity was thermally asymmetric because three sides of the cavity were insulated while the other side was exposed to convection with ambient air. The clearance ratio (CR) as the ratio between the gap from the insulated wall to the major axis of the tubes to the space of the cavity is varied 0.4 and 0.6. while the pitch ratio is constant at 3.5a. this study analyzes the characteristics of heat transfer from the surface of the elliptical tube to the surrounding air experimentally and numerically. The result reveals that the highest heat transfer coefficient 0f 0.4 CR is higher than that of 0.6 CR. The numerical solution shows the contour and streamlines of the fluid flow in all conditions as the characteristics of natural transfer thermally asymmetric cavity.

Thermal Analysis on Water-Simple Rankine Cycle and Combined Cycle for Waste Heat Recovery Flat Glass Factory Zefanya Hiro Wibowo; Budi Utomo Kukuh Widodo; Djatmiko Ichsani
JMES The International Journal of Mechanical Engineering and Sciences Vol 1, No 1 (2017)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v1i1.2213

One of the most important processes in glass production is the furnace section. The furnace’s waste heat, which still has a temperature around 400oC-500°C, is often released directly to the surrounding using a stack. Waste Heat Recovery Generation (WHRPG) and Organic Rankine Cycle (ORC) is one of the many waste heat reusing schemes implemented to increase the efficiency of industrial processes by converting the waste heat into electricity. Two schemes of the system will be studied in this research; there are Water-Simple Rankine Cycle (WSRC) and combined cycle (WSRC and ORC). In the WSRC, steam mass flow rate varied and found the highest performance to compare with combined cycle system. For combined cycle, the variations of the system are steam mass flow rate, the evaporating temperature, flue gas temperature in stack and refrigerant as working fluid. For the result, the highest combined cycle perform is 5.89 MW with steam mass flow rate 5 kg/s. Higher evaporating temperature (160°C) results in a higher combined cycle performance (5.96 MW), while, similarly, a lower flue gas temperature (120°C) also yields a higher combined cycle performance (6.3 MW). By varying the working fluids of R-11, R-113, and R-114.

Experimental Study of the Effect of Magnetization on Bioethanol Injectors on Spray Characteristics for Applications in the SINJAI-150 Engine Amalia Dwi Utami; Bambang Sudarmanta; Budi Utomo Kukuh Widodo; Ary Bachtiar Krisna Putra; Is Bunyamin Suryo
JMES: The International Journal of Mechanical Engineering and Sciences Vol 3 No 2 (2019)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v3i2.9389

In general, the hydrocarbon molecules in the fuel perform vibrational activity towards the core and attract each other, forming clustering molecules. Induction of a magnetic field in the fuel flow can change the hydrocarbon molecules so that their arrangement becomes more regular (de-clustering). The induction of the magnetic field in this research utilized a coil that was fed by an output current from the SINJAI-150 engine alternator. Magnetic field placement was placed before Bioethanol E100 fuel entered the injector. Observation of the magnetization of the fuel was carried out molecularly with the FTIR (Fourier Transform-Infra Red Spectroscopy) test and observing the characteristics of the fuel spray at the injector output. The results obtained were an increase in the fuel transmittance of Bioethanol E100 up to 41.31% for C-H compounds, 48.8% for C-O compounds, and 114% for O-H compounds compared to standard conditions. In the spray characteristics, there was an increase in the spray angle up to 2 and a decrease in the Sauter Mean Diameter (SMD) to 1.312 mm, due to a decrease in the value of the fuel properties in the form of surface tension, viscosity, and density up to 2.6%, 10.28% and 10.15% from the standard state without magnetization. As a result of decreasing the density value, the mass flow rate of the fuel decreases to 10.28% from the standard conditions at 2,000 rpm.

Characterization of Natural Convection over an Elliptical Tubes Array AR 2.5 and PR 1.25 inside a Thermally Asymmetric Cavity of Various Clearance Ratio Stefanus Widhipratama; Budi Utomo Kukuh Widodo
JMES: The International Journal of Mechanical Engineering and Sciences Vol 2 No 1 (2018)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v2i1.5167

Natural convection is the phenomenon of heat transfer due to the buoyancy force of fluid. One application of natural convection inside a vertical cavity is refrigerator condenser of circular cross-section tube. An experimental investigation is presented on natural convection of air over an array of elliptical tubes of AR 2.5 arranged vertically inside a thermally asymmetric cavity. One side of the cavity is insulated and the opposite side is exposed to ambient air. The distance between tubes, pitch ratio PR is constant at 1.25 where “a” is a half of tube major axis. The Clearance Ratio \textit{CR} which is the ratio between the distance of tubes array major axis to the insulated wall x and the width of the cavity y, is varied 0.4 and 0.6. The heat flux of the tube is maintained at 22.79 kW/m$^2$. It is found that the higher value of heat transfer coefficient is achieved on CR= 0.4.

Experimental and Numerical Studies of Natural Convection on Elliptical Tube in Thermal Asymmetric Cavity Angga Tegar Setiawan; Budi Utomo Kukuh Widodo; Nila Rahmawati
JMES: The International Journal of Mechanical Engineering and Sciences Vol 2 No 2 (2018)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v2i2.6398

The characteristic of natural convection heat transfer in a thermally asymmetric cavity is influenced by temperature differences and space between the heat source and cavity wall. The heat source is any bluff body placed inside the cavity. This research used a heated elliptic tube as the heat source inside the cavity. The three tubes are of 2.5 aspect ratio (AR) in a vertically aligned arrangement. The cavity was thermally asymmetric because three sides of the cavity were insulated while the other side was exposed to convection with ambient air. The clearance ratio (CR) as the ratio between the gap from the insulated wall to the major axis of the tubes to the space of the cavity is varied 0.4 and 0.6. while the pitch ratio is constant at 3.5a. this study analyzes the characteristics of heat transfer from the surface of the elliptical tube to the surrounding air experimentally and numerically. The result reveals that the highest heat transfer coefficient 0f 0.4 CR is higher than that of 0.6 CR. The numerical solution shows the contour and streamlines of the fluid flow in all conditions as the characteristics of natural transfer thermally asymmetric cavity.

Influence of Nozzle-to-Surface Distance Ratio and Reynolds Number Variation on Hemispherical Tempered Glass Strength and Quench Time Frans Loekito; Budi Utomo Kukuh Widodo; Djatmiko Ichsani
JMES: The International Journal of Mechanical Engineering and Sciences Vol 1 No 1 (2017)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v1i1.2208

The quenching step in a glass tempering process is a transient heat transfer phenomenon which is governed by several parameters – Reynolds number (Re) and the nozzle diameter-to-surface distance ratio (H/D). In this research, the effect of such parameters on the strength and quench time of hemispherical tempered glass are to be analyzed. The quenching process will use the impinging jets quench method, with an equilateral – staggered nozzle arrangements. The process is performed in an ambient air of 60oC and with a nozzle pitch and diameter of 27 mm and 4 mm respectively. The study applies variations of Reynolds number: 2300, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, and 87000, and H/D: 2, 6, 9, and 12. These variations are used to construct and solve a mathematical model, to obtain temperature distribution contours. The contours are then transformed into stress distribution graphs. From these steps, it is found that the tempered glass strength increases and the quench time decrease along with the increase of Re and the decrease of H/D. It is also found that the allowable range of operation is between Re = 8000 – 25000 for H/D =2 and Re = 8000 – 30000 for H/D = 6, 9, and 12.

Thermal Analysis on Water-Simple Rankine Cycle and Combined Cycle for Waste Heat Recovery Flat Glass Factory Zefanya Hiro Wibowo; Budi Utomo Kukuh Widodo; Djatmiko Ichsani
JMES: The International Journal of Mechanical Engineering and Sciences Vol 1 No 1 (2017)
Publisher : LPPM, Institut Teknologi Sepuluh Nopember, Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/j25807471.v1i1.2213

One of the most important processes in glass production is the furnace section. The furnace’s waste heat, which still has a temperature around 400oC-500°C, is often released directly to the surrounding using a stack. Waste Heat Recovery Generation (WHRPG) and Organic Rankine Cycle (ORC) is one of the many waste heat reusing schemes implemented to increase the efficiency of industrial processes by converting the waste heat into electricity. Two schemes of the system will be studied in this research; there are Water-Simple Rankine Cycle (WSRC) and combined cycle (WSRC and ORC). In the WSRC, steam mass flow rate varied and found the highest performance to compare with combined cycle system. For combined cycle, the variations of the system are steam mass flow rate, the evaporating temperature, flue gas temperature in stack and refrigerant as working fluid. For the result, the highest combined cycle perform is 5.89 MW with steam mass flow rate 5 kg/s. Higher evaporating temperature (160°C) results in a higher combined cycle performance (5.96 MW), while, similarly, a lower flue gas temperature (120°C) also yields a higher combined cycle performance (6.3 MW). By varying the working fluids of R-11, R-113, and R-114.

The Effect of Feedwater Heaters Operation Schemes to a 200 MW Steam Power Plant Heat Rate Using Cycle-Tempo Software Adi Apriyanto Wijaya; Budi Utomo Kukuh Widodo
IPTEK The Journal of Engineering Vol. 4 No. 3 (2018)
Publisher : Institut Teknologi Sepuluh Nopember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.12962/joe.v4i3.4995

There are several ways to improve performance of Rankine cycle which is implemented at steam power plant, regenerative feedwater heating is one of the methods. Some failures in closed feedwater heaters such as, water leak through manhole and tube leakage may happen during operation of the plant. Repairing such failures may take some period of time and must shut off the operation of the feedwater heaters. Further study is needed to evaluate the effect of closed feedwater heater in off-service condition against the steam power plant’s performance. This study varies off-service condition of closed feedwater heaters applying thermodynamics analysis and modeled through Cycle-Tempo software. There are 12 possible feedwater heater operation schemes. Based on the heat balance and equipment design of a 200 MW Steam Power Plant at Jakarta-Indonesia, this study concluded that the NPHR might increase as much as 0.96% and 0.39% due to the off-service of any HPH and the off-service of any LPH respectively. Schemes of 2 off-service feedwater heaters summed up with 1.37% increase of NPHR.

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