Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout

On-site investigations show that an asynchronous load feature would greatly influence the operation of water systems for centralized air conditioning. However, the manner of defining the load feature and relating it to its influence quantitatively is still unclear. This article quantitatively describes the asynchronous load demand feature and reveals its relationship with the loss of pump power and heat transfer ability in a centralized air-conditioning water system. The Lorenz curve and the Gini index are introduced in this study and used as indices to depict load features. For a large-scale use in office buildings, shopping malls, and other buildings, the fan coil unit and the variable air volume systems are investigated in this study. The loss of pump power on valves and heat transfer ability under different load profiles are analyzed. This study develops a new perspective of analyzing load patterns and quantitatively explores reasons for the resulting losses in pump power and heat transfer ability in ...

Influence of load feature on the water distribution system in a centralized air-conditioning system

Thermal optimization of secondary cooling systems in the continuous steel casting process

Abstract Shrinkage porosity is a typical internal defect in the continuous casting billet, which occurs frequently and is difficult to solve. To explore the influence factors of central shrinkage porosity, a novel unsteady thermomechanical coupling analysis algorithm is developed based on the billet solidification characteristics, and the central shrinkage behavior during the ending solidification process is simulated. Results show that when the casting speed increases from 1.6 to 2.8 m·min−1 and the center outward displacement is reduced from 9.20 × 10−2 mm to 5.8 × 10−2 mm, it means casting speed has a significant effect on the formation of shrinkage porosity, and for this caster, the higher casting speed is more suitable for the secondary cooling zone. Without the changes in the solidification structure, when the superheat degree of molten steel increases from 10 to 40°C, the center outward displacement value decreases from 7.12 × 10−2 mm to 6.91 × 10−2 mm. In that case, the superheat degree has no obvious effect on the center displacement value.

Numerical simulation of shrinkage porosity defect in billet continuous casting

An improved genetic algorithm is presented for the water consumption of the secondary cooling zone based on the heat transfer model of the off-line bloom caster. This study is to control the existing cooling systems and the steel casting practises in order to produce steel with best possible quality. The fitness function of improved genetic algorithm is founded according to the metallurgical criteria. This algorithm coupled with heat transfer model and metallurgical criteria, added dynamic coding method and self-adapting mutation on the original genetic algorithm can increase water distribution adaptively and improve the process efficiency. The simulation results of T91 bloom show that the optimised distribution reduced by 2% of water consumption comparing to that of before optimisation. The maximum surface cooling rate and the rate of temperature rise reduced, and the equiaxed rate increases. The function is built for explaining the relationship between the casting speed and water distribution.

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Beiyue Ma

Papers

The optimisation of the secondary cooling water distribution with improved genetic algorithm in continuous casting of steels