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There are three objectives that should be satisfied by the biscuit packaging process. Every packet of biscuits should ideally be exactly at the declared weight and in addition each pack should contain the same number of biscuits and the length of the biscuit pack should be invariant. Any deviations from these desired targets can impose costs on the manufacturer or have negative quality implications. However, because there is random variability in the weight and thickness of individual biscuits, it is not possible to achieve uniformity in packet parameters using existing packaging methods. A methodology is proposed whereby other possible approaches in assembling packets of column wrapped biscuits can be investigated. A Monte-Carlo computer model, sampling from the probability distribution functions of biscuit weight and thickness, has been developed to quantify the efficiencies of alternative packaging strategies. Packaging by fixed biscuit count is shown to be superior to the existing approach.

The objective in food dehydration is to dry the product to a specified uniform moisture content. In practice, a distribution in final moisture content is unavoidable, arising from the intrinsic variability of food properties and the probabilistic nature of the food drying process. A methodology is outlined whereby the inherent stochastic dynamics of batch tray dehydration in cabinet or tunnel dryers can be modeled efficiently using Markov chains. By simulating the drying process with the model, the progressive transformation of the moisture distribution of the trays throughout the drying cycle can be quantified. Output from the model is validated with experimental drying results to test its accuracy. In addition the output of the Markov approach is compared with that of an equivalent Monte Carlo simulation model to provide inter-model comparisons. Markov analysis can predict the variation in final moisture content and thus has the potential to help maximize the value of the dried product.

The objective in food dehydration is to dry the product to a specified uniform moisture content. In practice, a distribution in final moisture content is unavoidable, arising from the intrinsic variability of food properties and the probabilistic nature of the food drying process. For commercial dryers there are significant costs associated with this deviation in final moisture. To investigate the variability in the dehydration of vegetables, a model of a tray dryer was constructed, based on the empirical Page equation. It was solved using the Monte Carlo technique by describing the initial moisture content and the drying rate with probability distribution functions. A series of experiments were conducted to provide constants and statistical data for the model and to validate it. The utility of this approach is illustrated by applying the probabilistic drying model to quantifying and optimising the final moisture content distribution.

SYNOPSIS Timber, while being a low energy intensive material, requires a relatively high energy input in its processing operations, particularly drying. The schedules used for drying timber have largely been developed empirically by various government laboratories, trade organizations and sawmill operators. The schedules are generally low temperature and conservative which can mean unnecessary energy consumption and needlessly long residence times in the kiln. Thus processing costs are high due to recurrent energy costs and a relatively low return on capital investment in physical plant. This paper considers the energy related aspects of timber in general and the results of an empirical study in particular which indicate that the inherent energy advantages of using timber can be improved by the use of High Temperature Drying (HTD) techniques.

Static and dynamic models of the characteristic responses of sliotar cores made of both cork and polyurethane were studied in this work in order to understand their constitutive behaviour. Data from quasi-static tests at 10 mm/s and from dynamic impacts at speeds from 5 to 25 m/s were used to develop and evaluate the models. The quasi-static response was described well by Hertzian theory. A non-linear HunteCrossley model and a modified linear KelvineVoigt model were used to predict the dynamic response with set mass and shape coefficient parameters. The HunteCrossley model predicted well both the maximum force and maximum deflection for each ball type. The HunteCrossley model generally captured the experimental contact times well with a mean difference between experimental and model contact times of 8.3%. The mean difference between the KelvineVoigt model and experimental contact times was 7.6%, while the corresponding mean difference for the coefficient of restitution was 13.1%. Overall, the modified KelvineVoigt model predicted the parameters of contact time and coefficient of restitution well. Contact time and coefficient of restitution prediction in this linear model were not particularly sensitive to the strain rate.

A case study was conducted on a group of undergraduate chemical engineering students to assess the relevance of attending lectures from a student perspective and to understand why these students attend and do not attend lectures with a view to developing approaches to teaching, which are of greater interest and benefit to student learning. The students were surveyed by means of a questionnaire-type survey, which collected both quantitative and qualitative data from them. The majority of students stated that lectures are still very beneficial to their learning and are not an out-of-date mode of education. The major reasons for lecture non-attendance were time priority and curriculum overload issues with other scholarly activities and poor quality teaching. The students provided a number of suggestions to improve lectures and lecture attendance, including the incorporation of active learning in lectures, linking lectures to assessment and adding extra value to what is already in the notes.

Valves are employed to regulate flow and pressure drop in product and service fluid lines in dairy plants. Some valves have a simple open/closed mode of operation, while others can regulate flow between these two extremes. A variety of construction principles are possible to achieve the desired mode of operation. The most important feature of any valve is the relationship between the flow rate through it and the corresponding pressure drop across it. This feature must be considered for the valve itself (the inherent characteristic) and for the valve as a component of the total flow line (the installed characteristic). Equations from fluid mechanics are available to predict this depending on the nature of the flow: compressible versus incompressible, laminar versus turbulent, and so on. One particular aspect of good valve fluid flow design is the avoidance of the phenomenon of water hammer, which, if it occurs, can damage the valve and connected pipework. Hygienic design is also essential for valves in the dairy industry, and a variety of industry and regulatory bodies can supply sound guidelines in this regard. There are a number of means to actuate a valve: manually, electrically, pneumatically, or hydraulically; however, the pneumatic option is favored by dairy processors.

The buckling capacity of thin cylindrical shells subject to uniform external pressure is investigated in this paper. Thin cylindrical shells are known to be highly sensitive to geometric and material imperfections such as wall thickness variation, non-circularity and random geometric imperfections. The effect of imperfection on the buckling load is studied using finite element (FE) models and laboratory experiments. Imperfection measurements are taken on small scale steel cans and these measurements are modelled and analysed using a geometrically nonlinear static finite element analysis. The cans are then tested in the laboratory and the results compared with those predicted by the FE models and theory.Copyright © 2010 by ASME

The sliding conveyor consists of a plane surface, known as the track, along which particles are induced to move by vibrating the bed sinusoidal with respect to time. The forces on the particle include gravity, bed reaction force and friction. Because friction coefficients are inherently variable, particle motion along the bed is erratic and unpredictable. A deterministic model of particle motion (where friction is considered to be known and invariant) is selected and its output validated by experiment. Two probabilistic solution techniques are developed and applied to the deterministic model, in order to account for the randomness that is present. The two methods consider particle displacement to be represented by discrete time and continuous time random processes, respectively, and permits analytical solutions for mean and variance in displacement versus time to be found. These are compared with experimental measurements of particle motion. Ultimately this analysis can be employed to calculate residence-time distributions for such items of process equipment. © 2009 American Institute of Chemical Engineers AIChE J, 2010

The grid approximation of an initial‐boundary value problem is considered for a singularly perturbed parabolic reaction‐diffusion equation. The second‐order spatial derivative and the temporal derivative in the differential equation are multiplied by parameterså21andå22, respectively, that take arbitrary values in the open‐closed interval (0,1]. The solutions of such parabolic problems typically have boundary, initial layers and/or initial‐boundary layers.A prioriestimates are constructed for the regular and singular components of the solution. Using such estimates and the condensing mesh technique for a tensor‐product grid, piecewise‐uniform inxandt, a difference scheme is constructed that convergeså‐uniformly at the rateO(N−2ln2N + N0−1ln N0), where (N +1) and (N0+1) are the numbers of mesh points inxandtrespectively. First Published Online:14 Oct 2010

Reducing the liquid content of green products is an important step in the manufacture of many products. Process conditions in the drying phase have significant influences on the quality of the end product and on energy consumption and required manufacturing time. Effective optimisation of the drying process requires accurate representation of the drying product and its interaction with its environment. The development of a computer simulation tool to analyse the industrial batch timber drying process is outlined. A detailed finite difference product model describing the heat and mass transfers within a plank during drying is described. It is integrated with a customised CFD code characterising the process conditions within the drying chamber. Simulation output from the integrated model is used to generate a macroscopic representation of the product in its drying environment. This representation is included as a component in a modular industrial installation simulation environment. Analysis with this global model can lead to optimisation of energy consumption of the industrial timber drying process whilst maintaining product quality and acceptable drying duration.

An organic reaction searching system based on structural similarity has been developed for the Reaction Access System (REACCS). Although similarity searching in the molecular domain has been widely reported in the literature, we report the first application of these successful techniques to the organic reaction domain. Molecule and reaction similarity is determined by the degree of overlap of weighted fragment sets. Reaction similarity searching has applications in reaction classification, as a browsing tool and as a useful and simple alternative to substructure searching. Examples are provided.

Five common high protein dairy powders and their agglomerates produced by fluidised bed granulation were evaluated and compared for their rehydration characteristics in this study. Wettability of powders was measured by immersion wetting time, capillary rise wetting and contact angles methods, while dispersion and solubilisation processes were quantified by the change of particle size and the sediment height after centrifugation. The results showed that these high protein dairy powders generally had poor wettability, especially for whey protein isolate and the caseinates, which formed an impermeable layer separating the water surface and powders just after they contacted the water. However, the casein-micellar dominant powders exhibited prolonged dispersion due to strong interactions inside the micellar structures. The agglomerates with large particle size and high porosity are expected to exhibit increased wettability. However, agglomeration only caused the external structural modification and thus is difficult to accelerate the dispersion process of micellar casein, which can be explained by the milk protein isolate rehydration mechanism. The micellar structure inhibits the release of materials into surrounding liquid phase, which is mainly responsible for the extended rehydration time.