Dissertation > Excellent graduate degree dissertation topics show

Development of Gas Carrying Evaporation and Study of the Fouling on Its Heated Surface

Author: MaFeng
Tutor: ShenZiQiu
School: Dalian University of Technology
Course: Chemical Engineering
Keywords: Evaporation of the carrier gas Heat transfer characteristics Operating characteristics Sieve column The introduction of the carrier gas Dirt Analog loop hard water Subcooled flow boiling : fractal
CLC: TQ02
Type: PhD thesis
Year: 2003
Downloads: 321
Quote: 1
Read: Download Dissertation

Abstract

Solve the pharmaceutical, food, chemical and other industrial production in the heat-sensitive and easily scarring type materials thermal metamorphism of the enrichment process of evaporation scarring on the heated wall, Institute of Chemical Engineering, Dalian University of Technology developed the carrier gas evaporation technique. A wide range of basic research has been concentrated by evaporation of heat-sensitive materials and easy to scale-type material and process reboiler. More focus on larger liquid velocity (liquid velocity u ₁ = 0.3 ~ 1.6ms ^{-1 ) under the conditions of the study, these studies suitable for intermittent operation of the production, new development of the Institute of the upward straight-through carrier gas evaporator has a high efficiency and operating characteristics of continuous evaporation, concentrated by evaporation, can be applied to large-scale production of such evaporator to be material in the evaporation process of the carrier gas once through reached sufficient effect and concentrated to give the product, evaporation should be conducted under the conditions of low liquid velocity; other hand, for the easily polymerizable concentrated by evaporation of the aqueous solution of acrylamide, particularly the enrichment process of the biological production of aqueous solution of acrylamide, often require introducing a large amount of air as a carrier gas in order to achieve a good effect of inhibiting polymerization. Therefore, it is very necessary the further evaporation technology, research and development of carrier gas low liquid velocity carrier gas evaporation technology and the development of a new method of carrier gas concentrated aqueous solution of acrylamide evaporation. The dirt is a common problem in industrial production, which seriously affect the heat transfer process, and cause a great waste of energy. In the process of evaporation and concentration, fouling problems are often very serious, and even affect the conduct of the production. The carrier gas evaporation process due to the suppression of nucleate boiling, reduce the formation of dirt. Thus formed on the dirt mechanism, in particular, the introduction of the carrier gas of dirt formed to provide a theoretical basis for research access to a wider range of applications for the carrier gas evaporation technique. The main work of this paper is divided into the following areas: (1) u ₁ = 0.032 ~ 0.321ms ^{-1 low liquid velocity range of the carrier gas evaporation process (air as carrier gas) heat transfer and operating characteristics was studied. The results showed that: compared with convection boiling wall superheat decreases, the heat transfer film coefficient thus obtained is significantly improved; the same inlet superficial liquid velocity and the operating temperature, when the introduction of the relatively small amount of carrier gas, the heat transfer film Coefficient With the apparent improvement of the gas velocity increases; excessive carrier gas is introduced, the trend of the heat transfer film coefficient decreases with the apparent carrier gas rate increases, with the inlet superficial liquid velocity increases heat transfer film coefficient reduce the apparent carrier gas when the speed the greater; entire heating tube of the evaporation process of the carrier gas flow pattern is significantly higher than the general convection boiling down, the speed of the liquid rises and bubbles slip , the whole of the heating tube wall superheat decreases. Use of the the bubble slip model, simplified analysis of the the bubble slip enhanced heat transfer mechanism in the carrier gas evaporation process. (2) made of the carrier gas of an acrylamide aqueous solution was concentrated to the evaporation of the new method (air as a carrier gas). The acrylamide solution concentrated characteristics of the evaporation of the carrier gas is heating tubes arranged in the general sieve concentrated tower sieve on the the general screening Dalian University of Technology PhD thesis board tower condensed balance control process into heat and control process. Much greater amount of air than the amount of air introduced in the evaporator of the carrier gas before the carrier gas evaporated new method is compared with the previously proposed carrier gas evaporation method, since the polymerization inhibitor from the polymerization inhibitor is greatly enhanced, and the operation The scope and flexibility. According to this method to develop a new type of carrier gas evaporation the sieve column can be a multi-layer plate operation. Concentrated by evaporation capacity of the entire apparatus is greatly improved, not provided with heating tubes and trays less compared with the concentration ratio can be doubled. The device uses negative pressure operation, avoided propylene Thalidomide may leak from the device, and is conducive to environmental protection. (3) on the vertical rise in rectangular channel next to the heated wall to introduce the carrier gas (nitrogen, as set out in the gas) conditions under the convective heat conducted the experimental study, the results illustrate: introducing the carrier gas convective heat transfer coefficients than the single-phase circulating heat transfer coefficients have increased significantly low superficial liquid velocity and low heat flux, the heat transfer for mixed convective heat transfer, this enhanced effect is more significant, and can be enhanced about 5 times. The introduction of the carrier gas on the degree of convective heat transfer enhancement significantly better than the subcooled boiling heat transfer enhancement. Carrier gas enhanced heat transfer is caused by the increase of the liquid velocity in bubble slip turbulent enhancements, the result of the boundary layer turbulence and bubble slip additive effect of these two mechanisms. (4) analog industrial cooling water system CaC hatred of the vertical heat exchange surface fouling process using dynamic thermal resistance CaC03 scaling mechanism systematic experimental study. The carrier gas (nitrogen as a carrier gas), introduced in the current system to examine the role in the formation of the dirt, and analysis of its mechanism of action. Experiments found that the introduction of the carrier gas in the fluid flow path, can reduce the formation of dirt, and the introduction of the contained gas the greater, the smaller the formation of fouling resistance. The reason for the introduction of the carrier gas to reduce the fouling rate accelerate the adsorption bubbles leave the heated wall slip bubble increases the dirt removal rate and strengthen the heat transfer to the heating wall temperature to reduce the results of the three aspects together. (5) subcooling flow boiling process of CaCO3 in the vertical heat exchanger fouling on the mechanism of experimental studies, the introduction of carrier gas (nitrogen as a carrier gas) flow system to study the role in the formation of the dirt. Fractal theory, to study the CaCO3 crystallization fouling dirt shaped fractal characteristics. In addition, subcooled flow boiling dirt formation mechanism. : It was found that the introduction of the carrier gas, subcooled flow boiling fouling rate is reduced, but the introduction of carrier gas on subcooled flow boiling fouling rate is weaker than the convective heat transfer fouling rate; statistical self-similarity of CaCO3 crystallization fouling has CaC03 crystallization scale fractal dimension value, fractal characteristics; measured by box dimension, fractal dimension values ??reflect the size of the heat exchanger surface generated crystalline dirt surface complexity, can be used to describe the introduction of carrier gas formation of dirt .}}

Related Dissertations

CLC: > Industrial Technology > Chemical Industry > General issues > Chemical processes ( physical processes and physical and chemical processes )
© 2012 www.DissertationTopic.Net Mobile