The importance of evaporative condenser
Due to population expansion and economic development, water shortages are emerging in many parts of the world, especially in urban water shortages. Although the amount of water resources that can be exploited in China has reached 379 million kilowatts, the average per capita is less than 0.3 kilowatts.
The 《China Water Conservation Technology Policy Outline》 states: "Developing and promoting industrial water reuse technology and increasing water reuse rate are the primary means of industrial water conservation. Developing high-efficiency cooling water-saving technology is the focus of industrial water conservation."
The condensing and cooling equipment of the condenser is a large industrial energy-consuming water source. The cooling and cooling energy consumption accounts for 13%~15% of the industrial energy, the water consumption accounts for 70%-80% of the industrial water, and the indirect cooling water accounts for 70% of the cooling water. %~80%.
It is also in this case that evaporative condensation technology came into being and became one of the important technologies for water cycle recycling. Evaporative condensation technology plays an important role in the aviation, power, machinery, textile and other industrial fields.
At the same time, cooling towers, spray towers, evaporative condensers, etc. are the key equipment for the reuse of cooling water. The energy-saving and water-saving effects of evaporative condensers are not only theoretically obvious, but also good in practical applications. prove.
Therefore, research and development of evaporative condensing cooling equipment is of great practical significance.
2 Evaporative condenser advantages
According to the working principle of the evaporative condenser, since the evaporative condenser mainly uses the vaporization latent tropical water to condense heat released during the refrigerant condensation process, the amount of cooling water is much less than that of the water-cooled condenser.
The actual amount of water replenished is 1/25-1/50, which is water-cooled, which is especially suitable for water-deficient areas.
The performance and water consumption of various condensers were compared separately. According to calculations, when ammonia is used as the refrigerant and the cooling capacity is 3·8×106 kJ/h, the evaporative condenser saves an average of 3·4×105 kWh per year than the shell-and-tube condenser.
Theoretical progress of 3 evaporative heat exchangers
3.1 Progress in foreign theoretical research
The evaporation evaporation technology in foreign countries has developed relatively early, and the theoretical and research results obtained are relatively high. The basic heat and mass transfer theory of evaporative condensing equipment was proposed and developed by Merkel in 1925, which laid the foundation for future theoretical research.
Later, in the middle of the twentieth century, S.G. Chuklin and Owaki Hideo proposed a generalization method for the design of evaporative condensers.
Parker and Treyball studied the heat transfer and mass transfer performance of evaporative coolers, and clarified the heat transfer and mass transfer mechanism of evaporative coolers.
Experiments on the evaporative condenser and cooling tower mixing system show that the system can significantly reduce the condensation temperature and save heat exchange area. A computer program was developed for designing horizontal or vertical placement of light pipes, finned tube evaporative condensers and cooling tower mixing systems.
The heat and mass transfer test of the vertical tube evaporative cooler was carried out. The results show that the control thermal resistance occurs at the interface between air and water, and the empirical correlation for the performance calculation of the smooth vertical tube evaporative condenser is established.
The performance of the evaporative heat exchanger (cooling tower, fluid cooler, condenser) was simulated, and the difference between the simulation algorithm and the manufacturer (Baltimore, USA) was within ±3%.
Simulation calculations were carried out on the design of several evaporative cooler cores. It was found that the added plastic material (Munter) can significantly enhance the heat transfer performance of the smooth tube cooler without the use of costly finned tubes. To increase the heat transfer area.
A new mathematical model of heat and mass transfer for evaporative condenser is given. The model accurately describes the heat and mass transfer process. A computer simulation program suitable for the optical tube evaporative condenser is compiled. The calculated result is 3% compared with the experimental results, and the error is not more than 20%; and the calculation results have high precision, which verifies the rationality of the computer program.
The effect of steam mixture on the performance of DCXs heat exchanger under negative atmospheric pressure was studied. The influence of non-condensable gas at the inlet of DCXs heat exchanger was studied by experimental test. The mathematical calculation model was given and the model was pointed out. Provides a basis for condenser design.