Treatment of industrial wastewater by electrocoagulation (EC) is one of the most efficient methods to remove pollutants. Paper-recycling wastewater is a complex mixture containing toxic and recalcitrant substances, indicating complexity and difficulty of its treatment. The aim of the present study was to assess the effectiveness of paper-recycling wastewater treatment by EC process using aluminum (Al) and iron (Fe) plate electrodes. Removal of chemical oxygen demand (COD), total suspended solids (TSS), color and ammonia from paper-recycling mill effluent was evaluated at various electrolysis times (10–60 min), voltage (4–13 V) and pH (3.5–11). The optimum process conditions for the maximum removal of COD, TSS, color and ammonia from paper-recycling industry wastewater have been found to be pH value of 7, treatment time of 60 min and voltage of 10 V. Under optimum operating conditions, the removal capacities of COD, TSS, color and ammonia were 79.5%, 83.4%, 98.5% and 85.3%, respectively. It can be concluded that EC could be considered as an effective alternative for treatment of paper-recycling wastewater.
Heat transfer parameters are the most critical variables affecting turbine blade life. Therefore, accurately predicting heat transfer parameters is essential. In this study, for precise prediction of the blade temperature distribution, a conjugate heat transfer procedure is used. This procedure involves three different physical aspects: flow and heat transfer in external domain and internal cooling passages and conduction within metal blade. For the external flow simulation and conduction within metal, three-dimensional solvers are used. However, three-dimensional modeling of blade cooling passages is time-consuming because of complex cooling passage geometries. Therefore, in the current work, a one-dimensional network method is used for the simulation of cooling passages. For validation of the numerical procedure, simulation results are compared with the available experimental data for a C3X vane. Results show good agreement against experimental data. The present paper investigates uncertainties of some parameters that affect turbine blade heat transfer, namely, (1) turbine inlet temperature and pressure, (2) upstream stator coolant mass flow rate and temperature, (3) rotor shroud heat transfer coefficient and fluid temperature over shroud, (4) rotor coolant inlet pressure and temperature (as a result of secondary air system), (5) blade metal thermal conductivity, and (6) blade coating thickness and thermal conductivity. Results show that turbine inlet temperature, pressure drop and temperature rise in the secondary air system (SAS) and coating parameters have significant effect on the blade temperature.
Modern turbine blades are cooled by air flowing through internal cooling passages. Three-Dimensional numerical simulation of these blade cooling passages is too time-consuming because of their complex geometries. These geometrical complexities exist as a result of using various kinds of cooling technologies such as rib turbulators (inline, staggered, or inclined ribs), pin fin, 90 and 180 degree turns (both sharp and gradual turns, with and without turbulators), finned passage, by-pass flow and tip cap impingement. One possible solution to simulate such sophisticated passages is to use the one-dimensional network method, which is presented in the current work. Turbine blade cooling channels are flow passages having multiple inlets and exits. The present in-house developed solver uses a network method for analyzing such a complicated flow pattern. In this method, cooling system is represented by a network of elements connected together at different nodes. Using assumed wall temperature, internal flow and heat transfer is calculated. The final goal of this computation is a set of boundary conditions for conjugate blade heat transfer simulation (coolant side boundary conditions). For validation, it is required to use experimental data that include temperature distribution of blade coolant-side walls. Since there is no experimental work with such data in the open literature, numerical computation is validated using available analytical and published numerical data. Calculated results agree well with analytical and numerical data. In order to exhibit the potential capabilities of the developed code, flow and heat transfer in a complicated internal cooling passage of a typical vane are investigated using the network method.
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