Wettability of waterborne coatings on chemically and thermally modified pine wood

Modification of wood can change its hydrophilic character. Consequently, modified wettability of wood can change its behavior with coating or gluing processes. The authors investigated the wettability of oil-heat-treated and DMDHEU-modified Scots pine wood with some commercial waterborne coatings. The increased hydrophobic character of modified wood was revealed from high advancing contact angles of water. In contrast, exterior waterborne coatings exhibited much better wetting on modified substrates than on unmodified substrates. Good wetting of modified wood by waterborne coatings is an interesting result, opening up possibilities for application of environmentally friendly waterborne surface systems on modified wood.     

Removal rate of zinc from coal bottom ash in aqueous solutions

The leaching of inorganics including heavy metals from coal ashes has recently received extensive attention. This study was undertaken to understand the rate of leaching of metals from coal ash and the significant factors affecting the rate, and to develop an approach to predict leaching rates. The rate of leaching of zinc was characterized quantitatively for one coal bottom ash using a pseudokinetic mechanism. The resulting rate constants were correlated over a pH range of 1.3–9.3.     

Investigation of adsorption properties of geological materials for CO2 storage

The assessment for realistic CO₂‐adsorption capacities of different rocks is important for understanding the processes associated with CO₂ storage. This paper investigates the adsorption characteristics of rocks for CO₂ (limestone, sandstone, marl, claystone, clay, siltstone and metamorphic rock) by using a gravimetric method. The measurements were performed at 21°C with pressures from 1 up to 4 MPa. Sandstone (and clay with sand/sandstone) showed the largest adsorption capacity at 21°C. The highest amount of in situ CO₂ contents in measured samples was 21.4 kg/t. The CO₂‐adsorption capacities were lower than past results in different coal samples. The results indicate that adsorption of CO₂ into rocks may play an important role in storing CO₂ in subsurface rock. Copyright © 2012 John Wiley & Sons, Ltd.     

A Numerical Analysis of the Local Anomalies in a Natural-Draft Cooling Tower

This paper presents experimental and numerical analyses of the aero-thermodynamic characteristics of a natural-draft cooling tower. The influence of local technical faults in the fill and rain region on the cooling tower's performance was estimated. Measurements of the air velocity and the temperature above the droplet eliminators showed a noticeable non-uniformity of both parameters. This is caused by a non-uniform airflow resistance and heat-transfer rate within the fill and rain region. Based on these measurements, a commercial CFD model was customized with additional relations describing the heat- and mass-transfer, as well as the airflow resistance in individual regions of the cooling tower. The results of a 3D numerical simulation of the cooling tower are the temperature and velocity distributions within the entire cooling tower. A comparison of nominal and actual cooling tower operation shows regions with unfavorable air temperatures or velocities. Thus, the inefficiently operating areas of the cooling tower's cross-section can be identified. These areas cause non-homogeneous aero-thermodynamic characteristics and have an influence on the integral characteristics of the cooling tower. A sample calculation of an actual cooling tower shows the usefulness of the method when it comes to improving the cooling tower's performance. The improvement can be achieved by modifying the fill resistance and water distribution.     

Stochastic modeling of an industrial activated sludge process

The purpose of this paper is to develop a Box-Jenkins time series transfer function model of the effluent COD using the influent COD, from a sewage treatment process. The data is from an industrial waste treatment plant encompassing a 14-month period.The work was done in 3 steps: (1) Box-Jenkins ARIMA (autoregressive integrated moving average) modeling of the influent COD; (2) ARIMA modeling of the effluent COD; and (3) development of a transfer function model for the waste treatment process.It was found that single difference models best described influent and effluent COD. For the transfer function model, the influent COD had an insignificant effect on the effluent COD.     

Temperature control of highly exothermic batch polymerization reactors

In this article a highly exothermic batch polymerization reactor is considered. The reactor is simplified as a mixing tank with the internal heat generation treated as a disturbance. A fuzzy-hybrid-PID-feedback (FH-PID) control structure is developed in which the output of fuzzy hybrid portion is used to adjust the set point of a PID controller to compensate for the effect of the major disturbance, the heat of reaction. In this way, the hybrid portion of the controller does not influence the stability of the original PID control system. A fuzzy model was constructed to estimate the heat of reaction inside the fuzzy hybrid block. The fuzzy parameters of the hybrid portion do not depend on the process model and can be estimated from the transient response obtained with a conventional PID controller. This FH-PID control strategy has been applied to the temperature control of batch solution and batch inverse emulsion polymerizations of acrylamide in a 1 gallon pilot scale reactor. The results show that this fuzzy hybrid—PID-feedback control strategy improves the control performance of the batch polymerization reactor.     

Thermovision Method for Diagnostics of Local Characteristics of Natural Draft Cooling Towers

Abstract

Increased and more rigorous demands for power station operation in order to minimize both the cost of electrical energy production and environment pollution, addressed the necessity for optimisation of all segments of the process. As a consequence, there are certain needs for the introduction of new experimental methods which would ensure effective diagnostics.

A newly developed experimental method for thermovisional detection of the temperature field in natural draft cooling towers is presented in this paper. The method is adapted to the real conditions that are present inside cooling towers and enables spatial‐ and time‐dependent detection of local temperatures in the region of drift eliminators of natural draft cooling towers. Combined with the previously developed methods for detection of velocity and temperature fields, the thermovision method enables quick detection of the local efficiency of cooling towers. Results of the method can be used for diagnostics of local and integral characteristics of cooling tower operation. Apart from this, they enable prediction of local corrections in order to increase the cooling tower efficiency.     

Modeling of heat pump tumble dryer energy consumption and drying time

The use of heat pump tumble dryers is nowadays more common because they offer huge energy savings compared to conventional tumble dryers. Earlier studies made on conventional tumble dryers have shown that parameters such as heater power, fan speed, drum speed, weight and initial moisture content of textiles and air leakage have a huge impact on the energy efficiency and drying time. In the present study, a modified commercial heat pump tumble dryer was evaluated for energy consumption and drying time by changing operating parameters including fan speed, drum speed, and mass load. The total energy consumption and drying time were measured and corrected for the initial and final moisture content in the textiles. The experimental results based on 27 drying tests were evaluated to develop linear regression models for energy consumption and drying time, which show a good agreement with the experimental data. The results show that a large mass load, a high drum speed, and a low fan speed give the highest energy efficiency, i.e. the lowest energy consumption per kg of drying load. Larger loads extend the length of the drying cycle while higher fan and drum speeds result in shorter drying time.     

Influence of drum inlet air conditions on drying process in a domestic tumble dryer

This study examines how the inlet air temperature, relative humidity, and flow rate influence the textile drying process in an open cycle tumble dryer. An experimental setup was prepared by connecting a domestic tumble dryer to an external system for controlled heating, humidification, and transport of air. Experiments were conducted by drying cotton textiles (8?kg dry mass) at different air inlet conditions. On the basis of measured data, correlations for determination of the total drying time, the moisture evaporation rate during the constant drying rate, and the area-mass transfer coefficient were developed. The process in the drum was modeled by using an established moisture evaporation model, based on sorption isotherms. A commonly used and a recently reported sorption isotherm for cotton were used with the model. Agreement between calculated and measured drying curves was better in case of the commonly used sorption isotherm, but final moisture content was better predicted by the recently reported sorption isotherm.     

A mixing model for diagnosing reacting tracers and tracing reactants in chemical and biochemical processes

It has previously been shown (Tanner et al., 1985) that biochemical and chemical reaction processes of the Type A → B → C can lead not only to kinetic hysteresis between the rate of formation of C and the concentration of species B in batch processes, but also hysteresis between those variables in a closed, imperfectly mixed (two zone) batch reactor. Furthermore, crossplotting the intermediate reactant, B, in one region of the poorly mixed reactor against B from the other major region leads to a clockwise hysteresis curve which is defined by both its area and the coordinate phase angle. This paper shows that the earlier analysis (Tanner et al., 1985) can be extended to the more general system A → B, where A in one region of the vessel is crossplotted against A measured in the other region. With an initial concentration of A* in one zone equal to its highest concentration, the inscribed area double-valued crossplot of A, uniquely defines the system in terms of the inter-vessel flowrate to reaction rate constant ratio, D/k.