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Suamir I.N.,Bali State Polytechnic | Ardita I.N.,Bali State Polytechnic | Dewi N.I.K.,Bali State Polytechnic
Refrigeration Science and Technology | Year: 2015

This paper studied integration of heat pump and air conditioning systems to provide heating for hot water as well as cooling for hotel services based on weather conditions and energy costs in Indonesia. The paper also analyzed environmental impact and investigated economical aspect of such system in comparison with conventional technology consisting separate hot water boiler and air conditioning system. The study was conducted for a five star hotel of 636 rooms, 30 apartments and 25 meeting rooms. The results showed that optimum arrangement of the integration could reduce 36.7% energy consumption for space cooling and hot water supply. This accounted for about 6.6% of total energy use of the hotel. The investigated system was found to be economically viable for hotel application with energy cost reduction for air conditioning and hot water supply systems of 34.4%. The system could also provide reduction on the environmental impact.

Tsamos K.M.,Brunel University | Ge Y.T.,Brunel University | Santosa I.,Bali State Polytechnic | Tassou S.A.,Brunel University | And 2 more authors.
Energy Conversion and Management | Year: 2017

Refrigeration systems are crucial in retail food stores to ensure appropriate merchandising of food products. This paper compares four different CO2 refrigeration system configurations in terms of cooling performance, environmental impact, power consumption and annual running costs. The systems studied were the conventional booster refrigeration system with gas bypass (reference system), the all CO2 cascade system with gas bypass, a booster system with a gas bypass compressor, and integrated cascade all CO2 system with gas bypass compressor. The weather conditions of London, UK, and Athens, Greece, were used for the modelling of energy consumption and environmental impacts to represent moderate and warm climatic conditions respectively. The control strategies for the refrigeration systems were derived from experimental tests in the laboratory on a conventional booster refrigeration system. The results from the analysis showed that the CO2 booster system with gas bypass compressor can provide best performance with 5.0% energy savings for the warm climate and 3.65% for the moderate climate, followed by the integrated cascade all CO2 system with gas bypass compressor, with 3.6% and 2.1% savings over the reference system for the warm and moderate climates respectively. © 2017 The Authors.

Rahtika I.P.G.S.,Bali State Polytechnic | Rahtika I.P.G.S.,Brawijaya University | Wardana I.N.G.,Brawijaya University | Sonief A.A.,Brawijaya University | Siswanto E.,Brawijaya University
Advances in Acoustics and Vibration | Year: 2017

This paper shows the experimental results of the flutter speed of thin-flat plates with free leading edge in axial flow as a function of plates' geometry, fluid densities, and viscosities, as well as natural frequencies of the plates. The experiment was developed based on similitude theory using dimensional analysis and Buckingham Pi Theorem. Dimensional analysis generates four dimensionless numbers. Experiment was conducted by placing the thin-flat plates in a laminar flow wind tunnel in order to obtain the relationship among those dimensionless numbers. The flutter speed was measured by varying the flow velocity until the instability occurred. The dimensional analysis gives a map of the flutter Reynolds number as a function of a new type of dimensionless number that is hereby called flutter fluid structure interaction number, thickness-to-length, and aspect ratios as the correcting factors. This map is a very useful tool for predicting the flutter speed of thin-flat plates in general. This investigation found that the flutter Reynolds number is very high at the region of high flutter fluid structure and thickness-to-length ratios numbers; however, it is very sensitive to the change of those two dimensionless numbers. The sensitivity is higher at lower aspect ratio. Copyright © 2017 I. P. G. Sopan Rahtika et al.

Rasta I.M.,Bali State Polytechnic | Wardana I.N.G.,Brawijaya University | Hamidi N.,Brawijaya University | Sasongko M.N.,Brawijaya University
ARPN Journal of Engineering and Applied Sciences | Year: 2016

This paper presents an experimental investigation on effects of corn oil to ice nucleation phenomenon of a corn oil - water solution immersed in a tank containing super-cooled liquid mixture of water and propylene glycol. Temperature of water and propylene glycol mixture was to be maintained as low as -20 °C. The corn oil-water solution is a new PCM candidate to be investigated for medium temperature refrigeration applications. Thermal energy storage characteristics of the PCM candidate were established and tested at various concentrations using a T-history method. Ice nucleation below freezing point in water/ice at temperatures ranging from -6 °C to -4 °C was induced by mixing corn oil with water to form an oil-water solution. As most of the solution consisted of water, this PCM became a strong candidate for under 0 °C applications. The PCM should be capable to maintain product temperatures of a medium temperature refrigeration system between -1 °C and +5 °C. © 2006-2016 Asian Research Publishing Network (ARPN).

Santika W.G.,Bali State Polytechnic | Sudirman,Bali State Polytechnic | Nyoman Suamir I.,Bali State Polytechnic
ARPN Journal of Engineering and Applied Sciences | Year: 2016

The present study offers technical and economical analyses of grid-connected hybrid power systems for a large scale production industry located in Bali. The peak load of observed system can reach 970.630 kW consuming on average 16 MWh of electricity a day. Software HOMER was utilized as the optimization tool. The proposed hybrid renewable energy systems consist of wind turbines, a PV system, a converter, and batteries. The system is connected to the grid. Optimization results show that the best configuration is the Grid/Wind hybrid system with the predicted net present cost of -884,896 USD. The negative sign indicates that revenues (mostly from selling power to the grid) exceed costs. The levelized cost of electricity of the system is predicted to be -0.013 USD/kWh. The present study also conducts sensitivity analysis of some scenarios i.e. 50% and 100% increases in grid electricity prices, 50% reduction of PV and WECS prices, and 10 USD and 50 USD carbon taxes per ton CO2 emission. Implications of the findings are discussed. © 2006-2016 Asian Research Publishing Network (ARPN).

Putra I.K.G.D.,Udayana University | Prihatini P.M.,Bali State Polytechnic
Telkomnika | Year: 2012

Communication between doctor and patient play an important role in determining the diagnosis of the illness suffered by the patient. Consultation time constraints led to insufficient information obtained to produce a diagnosis. This limitation is overcome by developing an expert system using fuzzy logic to represent the vagueness of symptoms experienced by patients and the certainty factor represents a relationship between the symptoms and disease. Fuzzy logic method begins with the acquisition of knowledge to produce the facts and rules, implication process, composition and defuzzification. The result of defuzzification used in the calculation of sequential and combined certainty factor which represent the belief percentage of diseases diagnosis that suffered by the patient. The results of the expert diagnosis with expert system for the given cases indicates the system, has the similarity diagnosis with the expert at 93.99%.

Santika W.G.,Bali State Polytechnic | Sudiartha I.K.G.,Bali State Polytechnic | Putra I.G.P.M.E.,Bali State Polytechnic
Proceedings 2015 International Conference on Science and Technology, TICST 2015 | Year: 2015

In 2009, Midden & Ham found that social feedbacks motivated users to reduce energy consumption in washing experiments with a simulated washing machine. They also found that having negative social feedbacks reduced energy consumption better than having factual, positive social, and no feedbacks. The present study compares the effect of positive and negative social and factual feedbacks on user preferences in air conditioning (AC) temperature setting. A higher room temperature setting means a lower energy use. We predicted that having any of the feedbacks increased chosen temperatures compared to having no feedback and that having negative social feedbacks increased chosen temperatures compared to having either factual, positive social, or no feedbacks. An interface was made in order for the AC remote controller to be able to communicate with computers. Animated faces which are able to smile or frown were made representing positive and negative social feedbacks. The factual feedback is represented by a bar indicator that turns red when users choose low temperatures and green when high. 159 participants were asked to participate for the experiment and randomly assigned to either control, factual, positive, or negative feedback groups. A computer screen was put in front of respondents to display the animated feedbacks. Participants set their preferred AC temperature by means of a remote controller and the screen deliver feedbacks according to the chosen temperature. One-way ANOVA were used to analyze the data with temperatures as the dependent variable and feedbacks as independent variables. Results show that there was a significant effect of feedbacks on chosen temperatures, F(3, 153) = 20.96, p <.001, r =.54. There was a significant linear trend, F(1, 153) = 60.55, p <.001, r =.53, indicating that as the feedback changed from factual to positive and negative social, the temperature increased proportionally. Planned contrasts showed that having animated social feedbacks increased chosen temperatures compared to having no feedback, t(152) = 6.80, p <.001 (1-tailed), r =.39, and that having negative social feedbacks increased chosen temperatures compared to having positive social feedbacks, t(152) = 2.14, p .05 (1-tailed), r =.09. © 2015 IEEE.

Sunu P.W.,Bali State Polytechnic | Anakottapary D.S.,Bali State Polytechnic | Santika W.G.,Bali State Polytechnic
MATEC Web of Conferences | Year: 2016

Heat transfer in double pipe heat exchanger with circumference-rectangular grooves has been investigated experimentally. The volume flowrate of cold and hot water were varied to determine its influence on the approach temperature of the outlet terminals. In this experimental design, the grooves were incised in annular room that is placed on the outside surface of the inner pipe. The shell diameter is 38.1 mm and tube diameter 19.4 mm with 1 m length, which is made of aluminum. The flow pattern of the two fluids in the heat exchanger is a parallel flow. The working fluid is water with volume flow rate of 27.1, 23.8 and 19.8 l/minute. The temperature of water on the inlet terminals are 50±1°C for hot stream and 30±1°C for cold stream. Temperature measurements conducted on each terminal of the inlet and outlet heat exchanger. The results showed that the grooves induced the approach temperature. The change of the approach temperature from the grooves compared to that of without grooves decreased by 37.9%. This phenomenon indicates an increase in heat transfer process and performance of the heat exchanger. Groove improves the heat surface area of the inner pipe, increasing the momentum transfer and in the other hand, reducing the weight of heat exchangers itself. © Owned by the authors, published by EDP Sciences, 2016.

Suarta I.M.,Bali State Polytechnic | Wardana I.N.G.,Brawijaya University | Hamidi N.,Brawijaya University | Wijayanti W.,Brawijaya University
Journal of Combustion | Year: 2016

The role of hydrogen bond molecule clustering in laminar burning velocities was observed. The water in hydrous ethanol can change the interaction between water-ethanol molecules. A certain amount of water can become oxygenated which increases the burning velocity. The hydrogen bond interaction pattern of ethanol and water molecules was modeled. Based on the molecular model, azeotropic behavior emerges from ethanol-water hydrogen bond, which is at a 95.1%v composition. The interaction with water molecule causes the ethanol molecule to be clustered with centered oxygenated compound. So, it supplies extra oxygen and provides intermolecular empty spaces that are easily infiltrated by the air. In the azeotropic composition, the molecular bond chain is the shortest, so hypothetically the burning velocity is anticipated to increase. The laminar burning velocity of ethanol fuel was tested in a cylindrical explosion bomb in lean, stoichiometric, and rich mixtures. The experimental result showed that the maximum burning velocity occurred at hydrous ethanol of 95.5%v composition. This discrepancy is the result of the addition of energy from 7.7% free ethanol molecules that are not clustered. At the rich mixture, the burning velocity of this composition is higher than that of anhydrous ethanol. © 2016 I Made Suarta et al.

Suamir I.N.,Bali State Polytechnic
Applied Mechanics and Materials | Year: 2014

Indonesia has abundant renewable energy resources. In 2005 this country, however, only consumed 0.38% renewable energy of the total energy consumption. Most of the energy sources of the country are from fossil fuels which result in high CO2 emissions. Solar energy systems would be as an option to reduce the CO2 emissions of this country. This paper studied the application of solar energy to provide cooling for medium temperature food refrigeration based on Indonesian weather conditions. The paper additionally analyzed the environmental impact relating to CO2 emissions, and investigated the economical aspect. CFD-Fluent software was applied on modeling the modification of the absorption chiller generator to enable it to operate with heat from solar radiation, while F-Chart and Microsoft Excel spreadsheet were used to analyze the solar system and the economical viability of the technology. The results showed that the optimum modification of the absorption chiller was to use a jacket for heat addition. CFD modeling with Fluent using Diphyl THT as the heat transfer fluid (HTF) indicated that the system would function optimally at fluid temperature input of 180°C, whereas the optimum average temperature of the chiller generator would be 170°C. The proposed technology was found economically less viable for food refrigeration compared to the vapor compression cycle using R-404A but it could provide a significant impact on the environment by a reduction of 37% CO2 emissions. © (2014) Trans Tech Publications, Switzerland.

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