Preference-based multiobjective artificial bee colony algorithm for optimization of superheated steam temperature control

In order to incorporate the decision maker＇s preference into multiobjective optimization a preference-based multiobjective artificial bee colony algorithm PMABCA is proposed.In the proposed algorithm a novel reference point based preference expression method is addressed.The fitness assignment function is defined based on the nondominated rank and the newly defined preference distance.An archive set is introduced for saving the nondominated solutions and an improved crowding-distance operator is addressed to remove the extra solutions in the archive.The experimental results of two benchmark test functions show that a preferred set of solutions and some other non-preference solutions are achieved simultaneously.The simulation results of the proportional-integral-derivative PID parameter optimization for superheated steam temperature verify that the PMABCA is efficient in aiding to making a reasonable decision.

Aquathermolysis of conventional heavy oil with superheated steam

This paper presents a new aquathermolysis study of conventional heavy oil in superheated steam. A new high temperature autoclave was designed, where volume and pressure could be adjusted. Aquathermolysis was studied on two different conventional heavy oil samples under different reaction times and temperatures. Experimental results show that aquathermolysis does take place for conventional heavy oil. As reaction time increases, the oil viscosity reduces. However, the reaction will reach equilibrium after a certain period of time and won＇t be sensitive to any further reaction time any more. Analysis shows that, while resin and asphaltenes decrease, saturated hydrocarbons and the H/C ratio increase after reaction. The main mechanism of aquathermolysis includes hydrogenization, desulfuration reaction of resin and asphaltenes, etc.

Neuro-fuzzy generalized predictive control of boiler steam temperature

Power plants are nonlinear and uncertain complex systems. Reliable control of superheated steam temperature is necessary to ensure high efficiency and high load-following capability in the operation of modem power plant. A nonlinear generalized predictive controller based on neuro-fuzzy network （NFGPC） is proposed in this paper. The proposed nonlinear controller is applied to control the superheated steam temperature of a 200MW power plant. From the experiments on the plant and the simulation of the plant, much better performance than the traditional controller is obtained,

External Heat Transfer in Moist Air and Superheated Steam for Softwood Drying

In kiln drying of softwood timber, external heat and moisture mass transfercoefficients are important in defining boundary temperature and moisture content at the woodsurface. In addition, superheated steam drying of wood is a promising technology but this has notbeen widely accepted commercially, partially due to the lack of understanding of the dryingphenomena occurred during drying. In this work, experimental investigation was performed to quantifythe heat transfer between wood surface and surrounding moist air or superheated steam. In theexperiment, saturated radiata pine sapwood samples were dried using dry-bulb/wet-bulb temperaturesof 60℃/50℃, 90℃/60℃, 120℃/70℃, 140℃/90℃, 160℃/90℃, 140℃/100℃ and 160℃/100℃. The lasttwo schedules were for superheated steam drying as the wet-bulb temperature was set at 100℃. Thecirculation velocity over the board surface was controlled at 4.2m·s^(-1). Two additional runs(90℃/60℃) using air velocities of 2.4 m·s^(-1) and 4.8 m·s^(-1) were performed to check theeffect of the circulation velocity. During drying, sample weight and temperatures at wood surfaceand different depths were continuously measured. Prom these measurements, changes in woodtemperature and moisture content were calculated and external heat-transfer coefficient wasdetermined for both the moist air and the superheated steam drying.

Thermal Hydraulic Design and Analysis of a Water-Cooled Ceramic Breeder Blanket with Superheated Steam for CFETR

The water-cooled ceramic breeder blanket（WCCB） is one of the blanket candidates for China fusion engineering test reactor（CFETR）.In order to improve power generation efficiency and tritium breeding ratio,WCCB with superheated steam is under development.The thermal-hydraulic design is the key to achieve the purpose of safe heat removal and efficient power generation under normal and partial loading operation conditions.In this paper,the coolant flow scheme was designed and one self-developed analytical program was developed,based on a theoretical heat transfer model and empirical correlations.Employing this program,the design and analysis of related thermal-hydraulic parameters were performed under different fusion power conditions.The results indicated that the superheated steam water-cooled blanket is feasible.

Drying Characteristics of Wood under Vacuum-superheated Steam

This paper presents comparison and analysis of thermal-dynamic characteristics of air-drying and superheated steam drying under vacuum. The result reveals that for both convective heat transfer coefficient and resistance of mass transfer on the surface, superheated steam drying under vacuum is superior to air-drying under the same condition. With Masson pine as specimen, we found that the inversion temperature really exists through comparable experiments of air-drying and superheated steam drying under vacuum. When temperature is above inversion point of temperature, drying speed is faster than that of air-drying; however, if temperature is below the point, the result is opposite. The inversion temperature of experiment ranges from 80 to 85 ℃.

Characteristics and mathematical models of the thin-layer drying of paddy rice with low-pressure superheated steam

Drying paddy with low-pressure superheated steam(LPSS)can effectively increase theγ-aminobutyric acid content in paddy.This study aimed to investigate the characteristics and mathematical models(MMs)of thin-layer drying of paddy with LPSS.The experimentally obtained data werefitted by nonlinear regression with 5 MMs commonly used for thin-layer drying to calculate the goodness of fit of the MMs.Then,the thin-layer drying of paddy with LPSS was modeled with two machine learning methods as a Bayesian regularization back propagation(BRBP)neural network and a support vector machine(SVM).The results showed that paddy drying with LPSS is a reduced-rate drying process.The drying temperature and operating pressure have a significant impact on the drying process.Under the same pressure,increasing the drying temperature can accelerate the drying rate.Under the same temperature,increasing the operating pressure can accelerate the drying rate.The comparison of the model evaluation indexes showed that 5 common empirical MMs(Hederson and Pabis,Page,Midilli,Logarithmic,and Lewis)for thin-layer drying can achieve excellent fitting effects for a single experimental condition.However,the regression fitting of the indexes by calculating the coefficient(s)of each model showed that the empirical MMs produce poor fitting effects.The BRBP neural network-based model was slightly better than the SVM-based model,and both were significantly better than the empirical MM(the Henderson and Pabis model),as evidenced by a comparison of the training root mean square error(RMSE),testing RMSE,training mean absolute error(MAE),testing MAE,training R2,and testing R2 of the Henderson and Pabis model,the BRBP neural network model,and the SVM-based model.This results indicate that the MMs established by the two machine learning methods can better predict the moisture content changes in the paddy samples dried by LPSS.

Energy and Exergy Analysis of a Novel Efficient Combined Process by Hydrothermal Degradation and Superheated Steam Drying of Degradable Organic Wastes

This paper considers the combination of hydrothermal degradation （HTD） and superheated steam （SHS） drying in disposal and processing of degradable organic wastes in municipal solid wastes （MSW）. In SHS drying, a fraction of dryer thermal energy input can be recovered and used to satisfy the heat requirement in maintaining the HTD operating temperature. Both energy and exergy analysis are applied to the combined process. The analysis covers ranges of dryer inlet temperatures of 202.38-234.19~C and feed water content of 32.5-65%. Thermal energy analysis shows that the combination of HTD and SHS drying can achieve thermal energy self-sufficiency （TES） by manipulating process variables. The exergy analysis indicates the location, type, and magnitude of the exergy losses during the whole process by applying the second law of thermodynamics.

Effect of drying methods and parameters on the antioxidant properties of tea(Camellia sinensis)leaves

Background:Conventional drying using heated air oven is commonly used as a method for preserving the product but often affects the nutritional value,taste,and texture.However,the heat from the drying method can oxidize and destroy heat-sensitive compounds.Superheated steam(SHS)drying uses superheated steam instead of hot air or combustion gases in a direct dryer and was reported better at preserving the nutritional values of food products.Aim:To evaluate the effect of SHS drying on antioxidant properties of tea leaves.The study also compared SHS drying with conventional and freeze-drying methods.Results:Tea leaves dried using freeze drying retained the highest level of antioxidant properties compared to other drying methods.The leaves dried using SHS exhibited significantly higher radical scavenging activity,ORAC and FRAP values compared to oven drying method.At different drying temperatures(150℃and 175℃),oven dried leaves showed significantly higher(p<0.05)antioxidant properties than that of SHS dried ones.Tea leaves dried for 60,75,and 90 min using SHS showed significantly higher(p<0.05)FRAP and ORAC values,and also total phenolic content compared to oven dried tea leaves.Conclusion:Tea leaves dried using SHS drying method retained higher level of antioxidant properties compared to oven drying.The drying method also retained lower antioxidant properties as drying time increased.Further study involving SHS drying in food-related fields should be conducted to support its usefulness.