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Wu J.-F.,East China University of Science and Technology | Zeng L.-D.,East China University of Science and Technology | Zheng W.-Y.,East China University of Science and Technology | Zhou H.-J.,Shanghai Baofeng Machinery Manufacturing Co. | Zhu D.-S.,East China University of Science and Technology
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2012

The adjustment and optimization of operating parameters in the process of designing high efficient closed circuit cooling tower were analyzed to reduce the heat transfer area and pressure loss as much as possible. Optimization theory was used to control the different variables including velocity of process water inside the tube, density of spray water, air face velocity and air distribution. MATLAB's numerical analysis was used to reveal how much the variables work on the reduction of heat transfer area and pressure drop, which also helps to figure out the optimum operating parameters. The result shows that the optimum operating parameters are as follows: staggered arrangement, process water velocity of 1.2 m/s, spray water flow rate per unit length of 0.12 kg/(m·s), air face velocity of 3.0 m/s and air distribution of 175 m 3/(kW·h), which lead to the comprehensive minimum of heat transfer area and pressure drop, and so do the production and running costs. Source


Zheng W.-Y.,East China University of Science and Technology | Zhu D.-S.,East China University of Science and Technology | Song J.,East China University of Science and Technology | Zeng L.-D.,East China University of Science and Technology | Zhou H.-J.,Shanghai Baofeng Machinery Manufacturing Co.
Gao Xiao Hua Xue Gong Cheng Xue Bao/Journal of Chemical Engineering of Chinese Universities | Year: 2012

The heat and mass transfer of closed wet cooling towers were analyzed, a computational model was presented to predict the temperature distribution along the tower. A comparison between 1-D and 2-D was made. For the 1-D model, each tube row is an element and the 2-D model contains 4 and 10 elements per tube row, respectively. Based on Matlab programming, the cooling procedure program of cooling tower was composed. The difference of cooling water temperature distribution along the tower calculated separately by the 2-D model with 4 elements and with 10 elements is very small. Results obtained by 2-D model are closer to the results given by Hasan than those obtained by 1-D model. Based on Matlab programming, the outlet temperatures of cooling water in tubes were predicted by stepwise calculation with 10 elements per tube row. Compared with the experimental results, it can be seen that the calculated and measurement results are in good agreement. The proposed computational model can be used to predict the outlet cooling water temperatures and the spray water temperatures with variable flow rates and outdoor air conditions. Source


Zhu J.,Shanghai Ocean University | Xie J.,Shanghai Ocean University | Wang J.,Shanghai Ocean University | Du Z.,Shanghai Ocean University | Zhou H.,Shanghai Baofeng Machinery Manufacturing Co.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2014

In the evaporative condenser, the heat transfer performance was directly influenced by the spraying effect. When the evaporative condenser is in its working state, the cooling water passed through the top spray nozzle, and sprayed uniformly on the outside surface of condenser tubes, and formed a layer of water film. The low temperature water film took away a large amount of heat, the high temperature refrigerant vapor inside the tubes was cooled, and the purpose of the cooling fluid was achieved. In this paper, the spraying effects of two types of nozzles were simulated by CFD numerical calculation software, the real spraying effect was tested on a test platform, and the structure and layout of nozzles were improved at last. In order to get the spraying effect difference of the two types of spray nozzles, the pressure field and velocity field changes were analyzed when the spray nozzles were in different working states. The experimental and simulation results showed that the outer dynamic pressure field of each spray nozzle was irregularly distributed, which was caused by the change of the fluid motion trajectory under the minimum spraying amount. The local dynamic pressure of nozzle two was significantly higher than that of nozzle one. The outer velocity field distribution was directly influenced by the irregular distribution of the dynamic pressure field. The outer dynamic pressure of the two types of spray nozzles were 6000Pa and 13000Pa, and the outer local maximum velocity had reached 3m/s and 5m/s with the water inlet at the velocity of 2m/s. In the simulation, the outer dynamic pressure of nozzle two was always greater than that of nozzle one. The ratio of local dynamic pressure between the two types of spray nozzles was 2.33 when the velocity of water inlet was set to be 3m/s. Compared with spray nozzle one, the condenser cavity static pressure distribution of spray nozzle two was more uniform and reasonable, the local dynamic pressure and spray area were much bigger, and the fluid motion trajectory was simple and clear. The spraying effect could be improved by the design of a shunt channel. At last, the real spraying effect of the two types of spray nozzles was tested on a evaporative condenser test platform. 15 spray nozzles of every type were installed on the water inlet pipeline, and the spraying effect was caught by a high pixel camera when the evaporative condenser was under stable operation state. The water spraying effect showed that spray nozzle two had a much bigger spraying angle and spraying area, and it was better to enhance the spraying effect. In the future study, the internal flow field uniformity of nozzle one can be improved by adding a two-tier shunt platform. Furthermore, the diameter of the shunt base can be increased and more shunt channels can be added on the original base of nozzle two to optimize the spraying water effect and the heat transfer efficiency of the condenser. Source


Zheng W.-Y.,East China University of Science and Technology | Zhu D.-S.,East China University of Science and Technology | Song J.,East China University of Science and Technology | Zeng L.-D.,East China University of Science and Technology | Zhou H.-J.,Shanghai Baofeng Machinery Manufacturing Co.
Applied Thermal Engineering | Year: 2012

Closed wet cooling towers (CWCTs) characterize by smaller investment and exploitation cost as well as fewer materials and less space. It can be regarded as a cooling tower with the packing replaced by a bank of tubes. However, heat and mass transfer in an oval tube closed wet cooling tower (CWCT) have been little investigated under different operating conditions. The thermal performance characteristics of an oval tube CWCT were conducted. From the experimental results, correlations for the water-film heat transfer coefficient and air-water mass transfer coefficient are obtained. Experimental tests show the water-film heat transfer coefficient is a function of deluge-water temperature, deluge-water mass velocity and air mass velocity, which is different from that in the public literatures. The air-water mass transfer coefficient is a function of air mass velocity. In addition, a mathematical model with three ordinary differential functions is presented to predict the outlet process water temperature. The model is solved by a sectional method. The results show the analytical outlet temperature compares well with the experimental data. The method is suitable for evaluating the performance of an oval tube CWCT. © 2011 Elsevier Ltd. All rights reserved. Source


Zheng W.-Y.,East China University of Science and Technology | Zhu D.-S.,East China University of Science and Technology | Song J.,East China University of Science and Technology | Zeng L.-D.,East China University of Science and Technology | Zhou H.-J.,Shanghai Baofeng Machinery Manufacturing Co.
Huaxue Gongcheng/Chemical Engineering (China) | Year: 2011

An experimental platform was built for oval tube closed circuit cooling tower. The heat transfer performance of oval tube closed circuit cooling tower was tested by varying water temperature and flow rate in the tube, air mass flow rate, air wet/dry bulb temperature, deluge water flow rate and so on. The Popple and Dreybal analysis for evaporative coolers were presented for data processing. From the experimental results, the correlations for the water film heat transfer coefficient, air-water mass transfer coefficient were developed. Experimental tests show that the water film heat transfer coefficient is a function of air mass flow rate and mean deluge water temperature, which is different from those empirical equations in the reference literature of Mizushina, Niitsu, Parker, et al, while air-water mass transfer coefficient is a function of air mass flow rate. The heat and mass transfer coefficients obtained from experiments can be referred in optimal design for oval tube closed circuit cooling towers. Source

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