Analisa dan Desain Compact Condensor di Pembangkit Listrik Tenaga Gas dan Uap (PLTGU) Tanjung Priok

Kondensor merupakan salah satu komponen penukar panas yang berfungsi untuk membuang panas dari fluida uap air (steam) pada sebuah sistem pembangkit listrik tenaga gas dan uap (PLTGU). Namun komponen kondensor ini memiliki dimensi yang cukup besar sehingga memerlukan lahan yang luas. Penelitian ini dilakukan untuk mendapatkan dimensi kondensor yang lebih ringkas (compact) yang memerlukan lahan yang sedikit dalam penerapannya dilapangan. Desain Compact kondensor diawali dengan pengambilan data dilapangan, menghitung efisiensi kondensor awal (0,44), dan proses simulasi pada aplikasi CFD desain kondensor exisiting untuk mengetahui gambara dari proses perpindahan panas yang terjadi. Proses perhitungan untuk desain compact kondensor dilakukan untuk mendapatkan ukuran dimensi dan kinerja compact kondensor. Dari hasil perhitungan desain yang dilakukan didapatkan dimensi compact kondensor dengan panjang : 2 ft = 0,6096 m, lebar : 1 ft = 0,3048 m, dan tinggi 8 ft = 2,4384 m, dengan Volume Compact kondensor = 16 ft3 = 4,8768 m3, Efisiensi Sirip : 0.924027, Efisiensi Sirip Overall: 0.936563, Efisiensi kondensor : 0.60, Pressure Drop Sisi uap : 0,5184 Bar, Pressure Drop Sisi air : 1,4734 Bar, Daya Sisi uap : 70.43555 Watt, Daya Sisi air : 25.03529 Watt. Nilai efisiensi yang dihasilkan dari desain compact kondensor lebih tinggi dibandingkan dengan kondensor awal dengan dimensi yang lebih kecil. The condenser is one of the heat exchanger components that functions to remove heat from the water vapor fluid (steam) in a gas and steam power plant (PLTGU) system. However, this condenser component has dimensions large enough to require a large area. This research was conducted to obtain a condenser dimension that is more compact (compact) which requires less land in its application in the field. Compact condenser design begins with data collection in the field, calculating the efficiency of the initial condenser (0.44), and the simulation process in the application of the exisiting condenser CFD design to find out the details of the heat transfer process that occurs. The calculation process for compact condenser design is carried out to get the dimensions and compact condenser size. From the results of design calculations performed, the dimensions of the compact condenser with length: 2 ft = 0.6096 m, width: 1 ft = 0.3048 m, and height 8 ft = 2.4384 m, with condenser Compact Volume = 16 ft3 = 4 , 8768 m3, Fin Efficiency: 0.924027, Overall Fin Efficiency: 0.936563, Condenser efficiency: 0.60, Pressure Drop Vapor side: 0.5184 Bar, Pressure Drop Water side: 1.4734 Bar, Steam Side Power: 70.43555 Watt, Water Side Power : 25,03529 Watt. The efficiency value resulting from the compact condenser design is higher than the initial condenser with smaller dimensions.

Verbs of falling in Tigrinya

The paper gives a survey of verbs of falling in Tigrinya (an Ethio-Semitic language spoken in Eritrea and northern Ethiopia). The employment of each verb related to the situation of falling down is illustrated with phrasal examples. The Tigrinya data is further compared with Geez, a closely related extinct language. A special subsection deals with metaphorical use of the basic verb ‘to fall’ in Tigrinya. Tigrinya possesses one basic verb of falling, wädäḳä, which is applied to describe the downward movement of a solid object through the air or a loss of vertical position of a vertically oriented object. Falling of a solid, heavy object, either through the air or, less typically, along an oblique surface, can also be referred to by a special verb ṣädäfä. In all situations deviating from this default situation of falling in Tigrinya, special verbs are employed. Thus, the verbs tägälbäṭä ‘to be overturned, to topple’ or tägämṭälä ‘to be turned over’ are used to describe the situation of toppling, overturning which does not involve physical falling from a higher level to a lower one. Detachment of an object which had been fi rmly fi xed to another object, is usually denoted by the verb moläḳä ‘to slip off ; to become detached’. Falling to pieces of buildings or other built structures is described by the special verbs färäsä ‘to collapse, crumble, to fall’ or ʕanäwä ‘to collapse’ (but ṣädäfä can also be used in such contexts). Detachment of parts of body or plants due to natural reasons is denoted by the special verb rägäfä ‘to fall off (leaves), to break off , break loose (fruit, leaf), to shed a coat (livestock)’ (although the physical falling which is caused by such a detachment can well be described by the verb wädäḳä ‘to fall’). Furthermore, with respect to teeth, a special verb goräfä ‘to lose milk teeth, to have one’s tooth pulled out’ is used, with the possessor of the tooth encoded as the subject, and the tooth itself, as the object. Downward movement of liquids is denoted by a wide range of verbs, such as wäḥazä ‘to fl ow’, näṭäbä ‘to fall in drops, to drop (water), to drip (water)’, fäsäsä ‘to be spilled, poured (out) (water, grain, etc.), to fl ow (liquid, stream), to run (water), to fall (water)’, ṣärär bälä ‘to ooze, exude’, läḥakʷä ‘to drip, run (water along a wall after leaking through a roof), lo leak, to seep, fi lter through (intransitive)’. The verb wärädä ‘to descend’ is also used to describe the movement of liquids from a higher level to the lower. Spilling of granular material is denoted by fäsäsä ‘to be spilled, poured (out) (water, grain, etc.)’. Rolling down is denoted by the verb ʔankoraräyä/ʔankoraräwä ‘to roll’. Downward movement in water is described by the verb ṭäḥalä ‘to sink, to submerge’. Intentional losing of vertical position is described by the verb bäṭṭ bälä ‘to lie down’,and intentional movement from a higher level to the lower is described by wärädä ‘to descend’. The metaphors of falling include the employment of the verb wädäḳä to describe an abrupt, unexpected (and often unpleasant) change. This involves decrease in a measure, loss of interest, the destruction of a social power, arriving of a sudden calamity. A separate group of metaphorical employment is the verb wädäḳä as the standard predicate of such nouns as “lottery” and “lot”, presumably by extension from the situation of dice falling to the ground. Finally, death in battle is also denoted by the verb wädäḳä. The Geez cognate of wädäḳä likewise functions as the basic verb ‘to fall’, whose employment is very similar to, although not identical with, its Tigrinya equivalent. Similarly, Geez ṣadfa does not display any signifi cant diff erence from Tigrinya ṣädäfä in its semantics and usage.

Marangoni puffs: dramatically enhanced dissolution of droplets with an entrapped bubble

We present a curious effect observed during the dissolution process of water-immersed long-chain alcohol drops with an entrapped bubble. When the drop-water interface and the air bubble contact each other, a rapid cyclic motion that accelerates the drop's dissolution is found. We name this eye-catching phenomenon puffing.

Captive-air-bubble aerophobicity measurements of antibiofouling coatings for underwater MEMS devices

In this article, we report the measurement of underwater aerophobicity, through the captive-bubble method, for different polymeric coatings employed to protect microscale and nanoscale flexible electronic devices for seawater applications. Controlling the morphology and wettability of the coating, in particular with the incorporation of nanoparticles of fluorinated polymers, allows to adjust the hydrophilic/hydrophobic (aerophobic/aerophilic) character of the surface in order to achieve a more insulating and antibiofouling behavior. Morphological analysis (roughness) and wettability measurements in sessile-drop and captive-bubble methods were provided for some properly selected polymeric coatings. We found that parylene C decorated with poly(vinylidene fluoride) nanoparticles at a higher dispersion concentration (5 mg/mL) exhibits the best compromise between morphology, hydrophobicity, and underwater aerophobicity, with sessile-drop water contact angle of 95.1 ± 2.9° and captive-air-bubble contact angle of 133.1 ± 5.9°.

Impacts of air drying and DIC pretreatments on textural properties of frozen/thawed apple fruits

This research work is about dehydrofreezing assisted by DIC treatment as an innovative conservation process of apple fruits. Samples previously dehydrated and DIC treated were frozen at -30 °C and at two different practical freezing rates. The effects of sample water content (W) and practical freezing rate (PFR) on freezing characteristics and apple texture were examined. Thaw exudate water (TEW) of 200% and 100% db samples was approximately 3 g/100 g water. Whereas, it was lower than 0.5 g/100 g water for samples with 30% db W during thawing at 4 °C. Moreover, the impact of PFR on TEW was significant and very important only for high W samples. For samples whose water content was lower than 100% db, firmness was as higher as the W was lower, without any significant impact of PFR. Keywords: Dehydrofreezing; Instant controlled pressure drop; Water content; Practical freezing rate; Texture.