No abstract

Cooling systems using colling towers are often an important element in a production process and always involve water or energy consumption. Therefore, increasing the efficiency of the colling tower will reduce water and / or energy consumption. In order to increase the efficiency of colling tower energy consumption, the most studied part is the fills, where heat transfer occurs. However, there are no studies on the use of vortex generators in colling tower fills. Hence the aim of this study was to evaluate the performance improvement in a forced draught cooling tower using a vortex generator. It was conducted on a laboratory scale using single fill as a trial medium. The fill was made of 3-mm acrylic with dimensions of 30 × 30 × 1950 mm. A three-unit vortex generator was placed inside the fill. The rectangular vortex generator was made of 0.5-mm thick aluminium and had a size of 50 × 10 mm. Data were retrieved for the fills with and without a vortex generator. Water and air discharge of 1 L/minute and an inlet water temperature of 60°C were maintained. The results indicated that the effectiveness of the fill with a vortex generator was increased by 90.72% compared to the fill without a vortex generator.

Fresh water is basic need for life while the source is limited. Therefore, sea water is used as fresh water through desalination process. Sea water has different physical and chemical properties ranging from the surface to the seabed. The energy potential that can be obtained from the hydrostatic pressure also changes according to the depth. As part of the research of the utilization of sea water into fresh water, the aim of this study is to know the characteristics of sea water in the depth that can be utilized as source of fresh water. The sea water samples were taken at 11km from Ujung Kulon beach with depth of 0m, 20m, 40m, 60m, 80m, and 100m under the surface. The results showed that the physical properties at every depth were below the maximum allowable drinking water except for the amount of dissolved solids. Chemical characteristics at any depth above allowable level were fluoride, hardness (CaCo3), chloride, sodium, sulphate, and (KMnO4). In addition to the properties, pressure is one of the considerations in this study to determine the depth of sea water as sources for desalination. Pressure increased by 36.11% as the depth of the sea increased.

The geometry of a solar still determines the convection constants C and n, which in turn affect the convection heat transfer coefficient’s value and mass. A method for determining the value of convection heat transfer constants C and n has already been developed by the researchers. Therefore, this study aimed to use several methods and theories to find the value of convection heat transfer constants C and n. The results are then compared with the results of the study. The solar still used in this study has one slope. To reduce variables that cannot be controlled, the data collection was conducted indoors using a halogen lamp that can be regulated as a heat source for 24 hours nonstop. The sea surface height in the solar still was maintained at a height of 20 mm, using a height regulator. Temperature was measured using a data logger set to enter data every hour. The desalinised clean water was stored in bottles placed on scales that were recorded every one hour. Room temperature was maintained in the range of 35 to 36 oC. The data in this study were used to calculate the heat transfer constants C and n to obtain the value of the convection heat transfer coefficient and mass calculation. This study compares the calculation models of Tiwari, Dunkle and Power. The following calculation model results: Tiwari model, C = 0.082 and n = 0.612; Dunkle model, C = 0.075 and n = 1/3; Power model, C = 0.815 and n = 0.611. The C and n values obtained with these four approaches reveal that the results from the Power model calculation are the closest to the actual mass, showing a percentage deviation of 1.63%.

Many researchers already use sensible materials to enhance the performance of solar stills, but only a few use iron sand as a heat absorber in single-basin solar stills to enhance the performance, as demonstrated in this experiment. The study was conducted in the period August-September 2018 and used four solar stills with dimensions of 420 mm × 305 mm and a cover with a slope of 30 degrees. Three of the solar stills contained iron sand 20 mm high. The height of water in the three solar stills was 15 mm (V1), 20 mm (V2) and 25 mm (V3), so that the surface of the water would be: below the surface of the iron sand, on the same level as the surface of the iron sand, and above the surface of the iron sand, respectively. The fourth solar still, filled with only 20 mm (P) of water, was a benchmark for the others. From the results, we inferred that the heat absorbed by the iron sand enhanced the total heat transfer coefficients inside the solar still. This result agreed with exergy and overall efficiency of solar stills. The results showed that the fresh water produced by increasing V1, V2 and V3 against P was 1.5%, 51.8% and 57.1%, respectively. Therefore, we conclude that iron sand significantly enhances the productivity of a solar still. The best result was obtained when the water surface was higher than the iron sand surface.