Numerical Simulation And Optimization Of Small Condenser

The essence of condenser is heat exchanger,which can be divided into water-cooled condenser,air-cooled condenser and evaporative condenser.Water-cooled condensers mainly include shell-and-tube water-cooled condensers and plate water-cooled condensers.Condenser is an indispensable device in refrigeration unit,distillation water plant and power plant.Its performance determines the energy consumption and refrigeration effect of the system.So it is very necessary to study the condenser.This paper mainly studies the small shell-and-tube condenser,which is mostly used in desalination plant.In this paper,the numerical simulation software Fluent and its UDF（user-defined function）are used to simulate the condenser.The flow field on the shell side of the condenser is mainly analyzed.Because of the complexity of the tube bundle,the porous medium model is used to simplify the tube bundle area of the condenser.The simulation results are compared with the experimental results to verify the accuracy of the method.The small condenser studied in this paper is mainly used in desalination plant,so,the performance of the condenser has an important impact on the energy consumption and freshwater output of the plant.Because of the existing experimental data of integrated water-making plant,the condenser studied in this project is based on the condenser of the device to carry out numerical simulation,and then optimize it by simulating the heat transfer performance of small condenser under different conditions.The results show that when the inlet temperature of cooling water is higher,the heat load is more uniform and the heat transfer coefficient is higher,but the heat transfer temperature difference is lower,the condensation capacity per unit time is lower and the performance of the condenser is worse.When the inlet temperature of cooling water is lower,the heat load is more uneven and the heat transfer coefficient is lower,but the heat transfer temperature difference is higher,the condensation capacity per unit time is higher,and the performance of the condenser is better.When the cooling water velocity is higher,the heat load is more uniform,the heat transfer coefficient is higher,the condensation capacity per unit time is higher,and the performance of the condenser is better;when the cooling water velocity is lower,the heat load is more uneven,the heat transfer coefficient is lower,the condensation capacity per unit time is lower,and the performance of the condenser is worse.When the inlet velocity of mixed gas is higher,the heat load is more uniform,the utilization ratio of heat exchanger tube is higher,the overall heat transfer coefficient is higher,the condensation amount per unit time is higher,and the performance of condenser is better;when the cooling water velocity is lower,the heat load is more uneven,there is a larger low condensation rate zone,the overall heat transfer coefficient is lower,the condensation amount per unit time is lower,and the performance of the condenser is worse.Compared with the position of the exhaust port on the wall opposite the air intake of the condenser,the position of the exhaust port of the condenser on the top of the condenser and relatively far away from the air intake is more conducive to improving the condensation performance of the condenser.Comparing the condensation performance of three kinds of condensers,the condensation performance of the condenser with triangular arrangement is the best,while the condensation performance of the condenser with square staggered arrangement is the worst.The results of three-dimensional simulation show that there is a short circuit in the steam passage（steam flows directly to the outlet without passing through the tube bundle）in the condenser,so the method of adding baffles is optimized,which achieves good results and improves the heat transfer performance of the condenser by 26.43%.