IJTech International Journal of Technology

The condensation of water vapor plays a crucial role in various applications, including combating water scarcity. In this study, by employing molecular dynamics simulations, we delved into the impact of graphene coatings on water vapor condensation on copper surfaces. Unique to this work was the exploration of various levels of graphene coverage and distribution, a facet largely unexplored in prior investigations. The findings demonstrated a notable increase in the rate of water vapor condensation and heat transfer performance as the graphene coverage was reduced. Using graphene coverages of 84%, 68%, and 52%, the numbers of condensed water molecules were 664, 735, and 880 molecules/ns, respectively. One of the most important findings was that when using the same graphene coverage of 68%, the rate of water vapor condensation and heat transfer performance increased as the graphene coating became more distributed. The overall performance of the water condensation correlated well with the energy and vibrational interaction between the graphene and the copper. This phenomenon suggests how a hybrid surface can enhance the nucleation and growth of a droplet, which might be beneficial for tailoring graphene-coated copper surfaces for applications demanding efficient water vapor condensation.

Excellence in skilled operation is vital for the efficiency of geothermal power plants. Mount Salak geothermal power plant unit 1-2-3 has consistently produced no less than 180 MWe to the Java-Bali grid since its first commercial operation in 1994, with an equivalent availability factor (EAF) average of 96%. Owing to this long operation period, power plant efficiency must be improved for the sustainable production of electricity. In this study, energy and exergy analysis has been undertaken to ascertain the amount of energy that is used in the power plant’s current condition, and to determine the plant’s overall system losses. Research was carried out by collecting data relating to temperature, pressure, and mass flow rate. Data were analyzed using the control volume to assess the thermal and mass balance and ascertain the value of exergy. Analysis was conducted theoretically and compared with results calculated by Engineering Equation Solver (EES) software. The results showed that from 1069.90 MWe in steam energy entering the system, the total amount of exergy was 302.42 MWe. Mount Salak geothermal power plant unit 1-2-3 had an overall first law efficiency of 16.75% and an overall second law efficiency of 59.27%. The greatest losses - 27.84% of the total exergy - were in the condensers. This was caused by the quality of cooling water entering condensers, which was in turn a result of cooling tower performance. Results suggest that turbine unit 1 should be investigated further to determine causes of decreased capacity.

Understanding the dynamics of bubbles is necessary in an effort to increase the efficiency of separation of flotation process. The purpose of this research was to study characteristics of small bubbles (bubbles with diameter of 0.2-1 mm), which rise in a liquid column. Experimental set up was a column made of an acrylic pipe with inner diameter of 8.4 cm and length of 200 cm. Small bubbles were generated by copper cathode. The dynamics of bubbles were observed using a video camera. Video images were processed using image processing software. The results indicate that at height of 50 cm from cathode tip bubbles in average have reached its terminal velocity. It has been proven that effect of alum surfactant can reduce the bubbles terminal velocity.