Numerical prediction of rotary-kiln foundation temperature at an early age

The hydration heat confined to the core of the mass concrete during the hydration reaction causes a temperature rise and irregular temperature distribution in the concrete. High temperatures in concrete cause Delay Ettringite Formation (DEF) that cause damage several years after pouring, especially if the concrete is in an acidic environment. The uneven temperature distribution causes thermal stresses that can initiate cracks in the concrete surface. This article discusses a prediction of temperature distribution inside a mass concrete used as a rotary kiln foundation. We measure the heat of hydration of the concrete sample using an adiabatic calorie meter and derive the heat of hydration equation from the measurement data. The hydration heat was used in numerical calculations to obtain the temperature distribution, maximal temperature and temperature differential. The numerical calculation shows that the maximum foundation temperature was 64.01 0C. This temperature is still below the limit temperature for the occurrence of Delayed Ettringite Formation (DEF). The core region has the highest temperature, while the surfaces have the lowest temperature. The difference between the highest and lowest temperatures is 37.40 0C. However, the temperature differential exceeds the safe limit, 20 0C, so heat treatment to prevent cracking needs to be done

Studi Eksperimental Pengaruh Bilangan Reynold dan Fraksi Massa Terhadap Koefisien Perpindahan Panas Konveksi pada Pipa Coil

Aliran dua fase merupakan bagian dari aliran multi-fase dan  masih dapat dibedakan menjadi beberapa bagian yang memepengaruhi koefisien perpindahan panas. Pada dunia industri, koefisien perpindahanpanas memiliki arti penting. Dalam aplikasinya seperti pada proses pemanasan dan pendinginan, koefisien perpindahan panas sangat berpengaruh pada proses ini karena sangat menentukan hasil prosesyang di inginkan.. Perubahan fasa ini menciptakan kondisi aliran dua fasa dimana sebelumnya aliran tersebut hanya satu fasa. Kondisi aliran dua fasa ini tentu memiliki koefisien perpindahan panas yangberbeda daripada aliran satu fasa. Sehingga kita perlu mengetahui besarnya pengaruh koefisien perpindahan panas pada aliran dua fasa. Penelitian ini  bertujuan untuk menentukan pengaruh fraksi massa terhadap koefisien perpindahan panas pada dinding coil. &nbsp

Pengaruh Overlap Ratio pada Model Turbin Savonius terhadap Karakteristik Koefisien Daya Berdasarkan Eksperimen Pada Wind Tunnel

Wind energy is a resource that is abundant, environmentally friendly, and renewable, therefore it has the potential to be developed. Savonius vertical axis type is suitable for application in low wind speed conditions. The Savonius wind turbine has good self-starting so that it is able to rotate the rotor even though the wind speed is low, besides that the torque it produces is relatively high. This study aims to determine how differences in OR affect the performance of Savonius turbines with an aspect ratio (AR) of 2. The experimental method was applied in this research to investigate the characteristic Cp of the model using the wind tunnel with different overlap ratios of 0.1, 0.15, 0.2, 0.25, and 0.3. The wind turbine model that has been made using a 3D printing process made of PLA + material. The results obtained in each OR test are the maximum Cp value for the variation OR 0.1, which is 0.121, OR 0.15, the maximum Cp value obtained is 0.213, OR 0.2, the maximum Cp value is 0.245, OR 0.25, the maximum Cp value is 0.224 and OR 0.3, the maximum Cp value is 0.210. Based on the five overlap variations, the maximum Cp ratio is obtained at OR = 0.2, namely Cp = 0.245 and TSR = 0.7. The OR value of 0.2 is able to maximize turbine power and minimize negative torque because the flow through the overlap area can maximally direct wind power to the maximum backward blade

Accuracy of nominally 2nd order unstructured grid, CFD codes

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Comparison of Errors Caused by Flux Limiters on the Numerical Solution of Advection-Diffusion Problem

Flux limiters are widely used in numerical simulations to prevent spurious oscillation in the flow with strong property gradients. However, applying flux limiter on flow without strong property gradient such as advection-diffusion flow can cause errors. This article discusses the errors caused by several flux limiters in advection-diffusion flow solution. A method for applying one-dimensional limiters to two-dimensional unstructured mesh was also suggested. The error was measured by comparing the finite volume solution of a test case with a reference solution. The study shows that the calculation error of second-order finite volume with flux limiter was higher than that of second-order finite volume without limiter.  However, the error of third-order finite volume with flux limiter is less than that of second-order without flux limiter. Among the flux limiters tested in this study, Venkatakrishnan’s flux limiter produces the highest error, followed by Van leer’s limiter, EULER and SMART limiter

RANCANGAN DAN PEMBUATAN ALAT UKUR TEMPERATUR, TEKANAN DAN ALIRAN UDARA UNTUK KEPERLUAN LABORATORIUM

Sebuah rangkaian elektronik hotlwire anemometer yang terdiri atas tiga segmen yaitu segmen pengkonvesi dari tegangan kecepatan, segmen perara-rata dan segmen Analog to Digital Converter (ADC) dibuat dalam kegiatan ini. Unjuk kerja rangkaian diuji dengan membandingkan hasil pengukuran kecepatan pada aliran diatas plat datar dalam terowongan angin dengan hasil hitung numerik sebagai benchmark. Ditemukan, secara kualitatif kesesuaian yang baik antara hasil pengukuran dengan benchmark pada daerah aliran seragam diluar lapisan batas, alat ukur gagal mengukur dengan akurat pada daerah transisi dari lampiran batas ke aliran bebas

Offshore ocean thermal energy conversion in Layang-Layang Island, Sabah-Malaysia

Ocean Thermal Energy Conversion (OTEC) is a clean marine renewable energy using temperature difference between the sea surface and the deep ocean to rotate a generator to produce electrical energy. As Malaysia is an equatorial country located at latitudes less than 20 degrees covered by ocean, many islands, strain and many difference of topography, OTEC is very compatible build in Malaysia. This paper discussed the potential areas of OTEC to be applied in Layang-Layang Island, Sabah in Malaysia. The paper found that Layang-Layang Island was high potential for application of OTEC. Using site measurement data, 4 MW electricity generated by OTEC was simulated as a case study