Investigation of Thermal Performance of Evacuated Tube with Parabolic Trough Collector with and without Porous Media

In this paper a new model has demonstrated that it operates in a moderate performance scale to generate hot water. In its early stage, the preliminary model, which built with double pass water tube inside evacuated tube, was investigated experimentally. The model was tested inside room under different operation conditions in terms of solar radiation 300, 400, 500 and 600 W/m2 and water mass flow rates 0.00305 and 0.0083kg/s. In the first case, there was a problem because of the air gap inside the tube and surrounding the double pass water tube, so In the second stage, two different filling medium inside the evacuated tube was proposed to modify the preliminary model. The mediums cases include porous media (stainless steel wire mesh and Aluminum fiber metallic). The results show that maximum efficiency without porous media was 62.4% at 0.0083 kg/s and heat flux 600 W/m2, but after porous media applied, the efficiency reached 79.4% at 99.997% porosity of Aluminum fiber metallic and heat flux 600 W/m2 with same water mass flow.

Maximum Allowable Pressure Calculation of Water Tube Boiler during Operation

In the steam boiler industrial sector, pressure and temperature of the water tube are the two main factors that affect the safety and efficiency of a steam boiler. Explosions may be occurring because of a sudden drop in pressure without a corresponding drop in temperature. Therefore, understanding the temperature distribution of the water tube boiler is essential to control the failure and explosion of the boiler. Once the temperature distribution is known than the limiting factors that affect the water tube life such as the maximum allowable pressure can be determined. ANSYS software will be used to determine the temperature distribution in the water tube of a utility boiler during operation at elevated inlet water and furnace temperature. The theory of axisymmetric has been utilized since the water- tube is cylindrical in shape. In axisymmetric theory, a three-dimensional cylindrical problem like a water tube can be reduced to two-dimensional by ignoring the circumferential Ө, while the r-axis and z-axis became x-axis and y-axis or Cartesian coordinate. Then two-dimensional rectangular elements meshing for the profile cross-section along the water tube in r and z axes were implemented in a computerized simulation using ANSYS 10 to find out the steady-state temperature distribution of the water tube.

Analisa Efisiensi Termal Water Tube Boiler Berdasarkan Rasio Udara Bahan Bakar LPG Untuk Memproduksi Saturated dan Superheated Steam

Boiler adalah suatu bejana tertutup yang terbuat dari baja dan digunakan untuk menghasilkan steam. Agar dapat menghasilkan steam diperlukan pembakaran. Pembakaran merupakan reaksi eksotermis yang berlangsung sangat cepat, yang membebaskan energi berupa panas dan nyala api (flame temperature) serta mampu menyebarkan panas melalui suatu medium. Agar pembakaran terjadi dengan optimal maka harus memperhatikan nilai rasio udara bahan bakar atau Air Fuel Ratio (AFR). Tujuan dari penelitian ini untuk meningkatkan efisiensi termal water tube boiler. Bahan bakar yang digunakan adalah gas LPG. Oleh karena itu, pada penelitian kali ini akan difokuskan untuk menentukan rasio udara dengan bahan bakar gas yang paling tepat sehingga didapatkan hasil pembakaran dan produksi steam yang maksimal. Rasio udara bahan bakar gas dan excess air yang digunakan yakni, 15,78 (5%), 15,93 (6%), 16,08 (7%), 16,23 (8%), 16,38 (9%).