A METHOD FOR DETERMINING THE CONVECTIVE HEAT TRANSFER COEFFICIENT DURING IMMERSION FRYING

The convective heat transfer coefficient is a useful parameter in characterizing heat flow across a fluid/solid interface when the fluid flow field is complex and solution of the coupled transport equations impractical. While convective heat transfer coefficient values for many unit operations have been tabulated, the boiling phase of immersion frying has not been quantified. The objective of this study was to develop a laboratory method for the measurement of the convective heat transfer coefficient during immersion frying. The method that was developed was applied to the immersion frying of potato cylinders at an oil temperature of 180C. The convective heat transfer coefficient was initially 300 W/m²K, it increased sharply to 1100 W/m²K, and gradually decreased to 300 W/m²K over the duration of the process. Use of this new method will allow the study of the effects of oil temperature, oil quality, product shape/size, and product quality on heat transfer coefficients.     

Improving the equality of workload assignments in assembly lines

Most heuristic and optimal methods for assembly line balancing are designed either to minimize the number of workstations required given a production rate, or to maximize the production rate given a fixed number of workstations. This singular focus on line design efficiency typically results in an imbalanced allocation of tasks among the stations. This paper presents a new procedure that rebalances a given solution to level the allocation of tasks. Characteristics of dominant levelled solutions are identified and incorporated into this heuristic procedure. Computational results indicate that the procedure is very effective in levelling workloads.     

QUALITY COMPARISON OF FRENCH FRY STYLE POTATOES PRODUCED BY OVEN HEATING, IMMERSION FRYING AND CONTROLLED DYNAMIC RADIANT HEATING

The effect of finish heating method (oven heating, immersion frying and controlled dynamic radiant (CDR) heating) on mechanical properties, color and sensory properties of par‐fried French fries was evaluated. Peak breaking force was highest for CDR‐heated French fries. An equivalent b value (yellowness) for the crust of immersion‐fried and CDR‐heated French fries was found by using color analysis. Sensory evaluation indicated overall acceptability of CDR‐heated French fries equivalent to immersion fried‐French fried potatoes. Finish heating of par‐fried French fries using CDR heating showed promise to produce a reduced‐fat fried product, as well as an alternative process to traditional immersion finish frying.     

MEASUREMENT OF YIELD STRESS IN DARK CHOCOLATE USING CONTROLLED STRESS VANE METHOD

The controlled stress vane method was used to measure the yield stress in dark chocolate. Three vanes with different L/D ratios and five different stress rates were used in three different chocolate formulations. The vane displacement data did not indicate a definite yield phenomenon. When the vane displacement data were transformed into a ratio of vane velocity to elapsed time, the square root of vane velocity (SV) or the cube root of displacement, a definite yield phenomenon was observed. The SV was preferred on the basis of physical considerations and the linear regression of its derived yield stress on vane dimensions, stress rate and chocolate particle size. The value of the yield stress was the least when determined for a vane height to diameter ratio of 2 and at a stress rate of 3 Pa/min using the SV transformation.     

Pedagogy of an Aircraft Studio

A studio was developed to teach engineering design and prepare students for emerging environments in the aircraft industry. Emphasis is placed on synthesis, in general, and specifically, on rigorous solution of open‐ended engineering problems. Key elements are the design, engineering, testing, and fabrication of an aircraft that provides common focus and interdependency, the structure of teams and phases that allows cycling of leadership responsibilities, an open‐ended grading system that reflects the nature of design, and open‐ended laboratory work that provides the reality check. The central focus of the Aircraft Studio, which has been the RP‐3 two‐seat aerobatic sailplane that made its maiden flight in December 1999, has facilitated pragmatic, relevant, “just‐in‐time” education without abandoning the principles of engineering science.     

Everyday Geometries: Synthetic Facts and Superficial Qualities

Streamlining becomes here an organic force as it relates to the dynamic equilibrium of the motion of the body within encompassed space. Frederick Kiesler     

Probing the effect of polymer molecular weight on penetration into the wood cell wall using polyethylenimine (PEI) as a model compound

Decking is one of the largest applications for the treated wood market. The most challenging property to obtain for treated wood is dimensional stability, which can be achieved, in part, by cell wall bulking, cell wall polymer crosslinking and removal of hygroscopic components in the cell wall. A commonly accepted key requirement is for the actives to infuse through the cell wall, which has a microporosity of ～5–13 nm. Equally as challenging is being able to measure and quantify the cell wall penetration. Branched polyethylenimine (PEI) was studied as a model polymer for penetration due to its water solubility, polarity, variable molecular weight ranges, and ability to form a chelation complex with preservative metals to treat lumbers. Two different molecular weight polyethylenimines (PEI), one with a weight average molecular weight (Mw) equal to 800 Da and the other 750 000 Da, were investigated for penetration by microscopy and spectroscopy techniques. Analytical methods were developed to both create smooth interfaces and for relative quantitation and visualisation of PEI penetration into the wood. The results showed both PEI with Mw of 800 Da and PEI with Mw of 750 000 Da coated the lumens in high density. However, only the PEI with Mw of 800 appeared to penetrate the cell walls in sufficient levels. Literature has shown the hydrodynamic radii of PEI 750 000 is near 29 nm, whereas a smaller PEI at 25 K showed 4.5 nm. Most importantly the results, based on methods developed, show how molecular weight and tertiary structure of the polymer can affect its penetration, with the microporosity of the wood being the main barrier.     

The analysis of an inventory control model using posynomial geometric programming

We consider a generalization of the well-known ‘sawtooth’ inventory control model which is used to determine optimal policies for stocking a single item under certain conditions. The case where several items are to be stocked simultaneously and subject to a number of constraints give rise to the generalization that is of interest. We show that the problem of analysing the model may he viewed as a problem in posynomial Geometric Programming. We then point out some of the advantages to be realized from viewing it this way and from using Geometric Programming techniques to solve it. These include, the ability to obtain feasible solutions with known upper bounds on the difference between their associated costs and the minimum cost, a capability for performing an analysis of the sensitivity of the values of the optimized parameters to variations in input parameters, availability of a solution method that is computationally more attractive than methods previously known and, arising out of this last benefit, an ability to deal with much more complicated problems to which the model is applied than previously seemed practical. A simple example problem is solved in detail to illustrate many of these benefits and results are presented for a much more complex case. In addition some possible extensions of the model, which can also be dealt with in this framework, are pointed out.