Efficiency of ventilated facades in terms of airflow in the air gap

The gradual exploitation of the natural environment has forced most developed countries to promote ecological solutions and the development of sustainable construction. Ventilated facades perfectly match into this trend, and with their appropriate design, they bring real energy savings. This paper analyzes numerically the influence of the inflowing air, mimicking the wind, on the efficiency of heat removal from the ventilated space and heat transmission by thermal radiation and conduction through the consecutive layers of the external wall. For the purpose of comparison, two variants of ventilated facade were adopted: open and closed joints, at different wind speeds prevailing outside. The results obtained show that in windless weather, the ventilated facade with open joints shows higher heat removal efficiency and thus lower heat transmission to the building interior. At higher wind speeds of 5 m/s, the open-joint and closed-joint ventilated facades achieve similar heat transfer efficiency, and the prevailing temperature inside the building for the two technologies is almost identical. Subsequent increments of incoming wind on the building result in minimal differences in the heat transmission to the building interior, representing changes of about 0.1°C at increments of another 5 m/s of incoming wind. Conscious use of this facade technology, along with appropriate urban design of cities, can help reduce the energy needed to cool buildings during the summer period.

Perfection of cooling systems of overhead tuyeres heads of 250-t BOFs

Deterioration of tips cooling as a result of number of nuzzles increase in tuyere heads does not allow to use multinozzle (six and more) overhead tuyeres for increasing of steel melting technical and economical indices and operating characteristics of technological equipment. The main reason of it is as follows: deterioration ofcooling results in over-heating and burnt-outof tips material in the farthest nozzle zone following the overhead tuyeres breakage. To avoid the water stagnant areas in the farthestnozzle zones of the heads cooling route and therefore to increase the overheads oxygen tuyeres of 250-t BOF operation life, a new design of the six-nozzle tuyere head with asymmetric cooling of tips farthest zones elaborated, manufactures and tested. The perfection of the six-nozzle heads cooling system included asymmetric (relating the side surface of the nozzle block) installation behind every nozzle (in the water direction) a guidingblade of special design. It enabled to increase to a maximum degree the heat removal efficiency from the internal surface in the tip farthest zones and had a positive effect on the overhead tuyeres heads resistance. The workability of the proposed design of the six-nozzle tuyere head with asymmetric cooling of farthest zones was confirmed during test-industrial heats at 250-t BOFs of OJSC “Dneprovskysteel-works”. The heats were carried out with oxygen consumption of 800–1200 m 3/min and regime of partial afterburning ofexit gases. The water consumption for tuyeres cooling decrease from 320–340 m 3 /h, at that the water temperature difference at the tuyere entry and exit varied in the range of 11–16 °C depending on blow-down duration. Application of the new design of the six-nozzle tuyere head with asymmetric farthest zones cooling enabled to increase the sixnozzle heads resistance by a factor 1.287 comparing with six-nozzle heads without farthest zones cooling and by a factor of 3.327 comparing with regular five-nozzle tuyere heads. The effect reached thanks to more rational cooler distribution and increase ofits velocity. The metal pick up of shafts of the six-nozzle tuyere head with asymmetric farthest zones cooling: while the five-nozzle tuyeres were taken off for salamander cutting off after 1–5 heats, the six-nozzle tuyeres were taken off for the salamander cutting off after 79–81 heats. It indicated a higher efficiency of heat running blow-down and slag regimes with application of proposed design of the six-nozzle tuyere head with asymmetric farthest zones cooling.

Desain dan Optimasi Injection Mold dengan Sistem Slider pada Produk Hardcase Handphone

Peningkatan penggunaan handphone pada era digital saat ini, berdampak pada peningkatan penggunaan pelindung handphone. Hardcase merupakan jenis pelindung handphone dengan bahan material plastik dan proses pembentukan menggunakan metode injection molding. Metode tersebut membutuhkan mold (cetakan) sebagai tempat untuk membentuk/menghasilkan sebuah produk. Dari latar belakang peningkatan penggunaan handphone, maka dibutuhkan perancangan mold untuk menghasilkan produk pelindung handphone berbahan plastik dengan jenis hardcase, sebagai solusi untuk menyediakan aksesoris berupa pelindung handphone pada para pengguna handphone. Pada perancangan hardcase, material yang digunakan pada produk yaitu polycarbonate iupilon GS2010MPH, konstruksi pada pembentukan hardcase menggunakan sistem slider dengan mekanisme angular pin. Software yang digunakan untuk perancangan mold, yaitu catia v5r21 dan software simulasi produk menggunakan autodesk moldflow insight 2016. Simulasi yang dilakukan, yaitu fill dan cooling, masing-masing dibandingkan untuk mendapatkan hasil yang optimal serta dapat diterapkan pada perancangan mold hardcase. Hasil perbandingan dan analisa dari moldflow insight yang dilakukan didapat, fill time yaitu 0,9630 s dengan clamping force 326,2 ton. Kemudian sistem cooling mengunakan tipe seri dengan hasil simulasi Circuit coolant temperature, yaitu 25,63 0C dan hasil simulasi deflection, all effects:deflection, yaitu 0,1411 mm dan hasil simulasi circuit heat removal efficiency, yaitu 1. Hasil perhitungan yang dilakukan pada konstruksi desain mold, dinyatakan aman karena nilai tegangan yang terjadi dibawah tegangan bahan material. Dari hasil perancangan desain dan simulasi, maka mesin yang digunakan yaitu Beston 4500.

Empirical Model Rating Method of Heat Removal Efficiency for Vertical Mantle Storage Tanks

The heat removal efficiency of a storage tank is effective to evaluate the thermal energy that users can obtain during its heat removal phase. With different types and volumes Vt, from 174 L to 1093 L, of six vertical mantle storage tanks widely applied to heat pumps and solar heating systems, the analyses of heat removal patterns were carried out. In addition, using a new integrated variable (Ti − Tw)/ V˙d found from the heat removal patterns, an empirical model of heat removal efficiency has been developed. The study found that the empirical model is a logarithmic curve ηR = aLn((Ti − Tw)/V˙d)+b with a good data correlation coefficient from 0.93 to 0.97. Characteristic heat removal efficiency ηR* was set up with this empirical model based on the relation of ηR* = ηR|(Ti − Tw)/V˙d = 1.5. The characteristic heat removal efficiency ηR* presents the useful thermal energy in a storage tank and the testing method is characterized by fitting it for different types, volumes, charge modes, and discharge modes of storage tanks. It is a practical testing method for the heat removal efficiency testing of a vertical mantle storage tank. The testing method provides the manufacturers of the systems with the information that how many energy output rates of their commercial products can be more improved, and then they can be sure to supply consumers the high quality of products.

Characteristic Heat Removal Efficiency for Thermosyphon Solar Water Heaters During the System Application Phase

The overall performance rating of a thermosyphon solar water heater should take into consideration its heat removal efficiency during the system application phase. This study employs a precise on-line operation to first identify physical heat removal patterns of a thermosyphon solar water heater, and then develops an empirical model for deriving its characteristic heat removal efficiency. This empirical model is in the form of a logarithmic curve, and has a high data correlation coefficient of 0.889 to 0.967. Based upon the empirical model, this study defines a characteristic heat removal efficiency parameter for thermosyphon solar water heaters. Finally, this study establishes a storage tank design method which enables the characteristic heat removal efficiency of the complete system to be optimized.