No abstract

A mathematical model was developed to get an equation of the decrease of air velocity crossing the canopy of tree crops during pesticide application using air carrier orchard sprayers. The utility of such a model rises from the need for an aid to understand the experimental results of several authors, who agree with the opinion that air jet velocity greatly affects environmental pollution from pesticides. Further, probably in the future it will arise the demand to implement the equation of air velocity decay in self-adjustment systems of the fan installed on orchard sprayers to limit spray drift. Based on momentum theorem applied under three assumptions, a differential equation was found and its integration lead to a closed 1282 Dario Friso et al. solution that can easily be implemented in a PLC for the self-adjustment system to develop. The integral equation thus obtained, together with the assumptions made, was submitted to on-field verification on three crops (peach, vine and apple). The results show a good correspondence between measured and estimated air speed as predicted by the mathematical model, with a relative mean error 3.3% and a maximum value of 6.2%.

A mathematical model was developed to correlate the four heat penetration parameters of 57 Stumbo's tables (18,513 datasets) in canned food: (the difference between the retort and the coldest point temperatures in the canned food at the end of the heating process), ℎ / (the ratio of the heating rate index to the sterilizing value), (the temperature change required for the thermal destruction curve to traverse one log cycle), and , (the cooling lag factor). The quantities , , and , are input variables for predicting ℎ / , while , and ℎ / are input variables for predicting the value of , which is necessary to calculate the heating process time , at constant retort temperature, using Ball's formula. The process time calculated using the value obtained from the mathematical model closely followed the time calculated from the tabulated values (root mean square of absolute errors RMS = 0.567 min, average absolute error = 0.421 min with a standard deviation SD = 0.380 min). Because the mathematical model can be used to predict the intermediate values of any combination of inputs, avoiding the storage requirements and the interpolation of 57 Stumbo's tables, it allows a quick and easy automation of thermal process calculations and to perform these calculations using a spreadsheet.

The mathematical modeling presented in this work concerns the conveyor-belt dryer with the tangential flow of air with respect to food. This dryer, if operating in co-current, has the advantage of well preserving the organoleptic and nutritional qualities of the dried product. In fact, it has a low air temperature in the final stretch where the product has low moisture content and is therefore more temperature sensitive. It is a bulkier dryer than the continuous through-circulation conveyor dryer with a perforated belt. The latter is therefore more frequently used and has received greater study attention from researchers and designers of the industry. With the aim to propose guidelines for a rational design of the conveyor-belt dryer with tangential flow, a mathematical model was developed here through the differentiation of the drying rate equation followed by its integration performed along the dryer belt. Consequently, and with the assumption that the final moisture content XF of the product is higher than the critical moisture content XC, the relationships between the intensive quantities (temperatures, humidity and enthalpies), the extensive quantities (air and product flow rates) and the dimensional ones (length and width of the belt), were obtained. Finally, on the basis of these relationships, the rules for an optimized design for XF > XC were obtained and experimentally evaluated.

The performance of a 118-kW tractor fuelled by pure biodiesel was monitored during a long-term field experiment with\ud approximately 800 h of engine function. The objective was to demonstrate that B100, a pure biodiesel fuel, is a viable alternative to\ud traditional diesel oil in terms of long-term mechanical reliability. A bench test on the new engine, performed by attaching a test stand to\ud the power take-off of the tractor, showed an expected reduction in power (–9%) and torque (–7%) and an increase in specific consumption\ud (+13%) when biodiesel was used as a complete substitute to diesel oil. Furthermore, with the same setup, the exhaust gas had a Bosch\ud smoke index equal to 50% of the value for the same engine fuelled with diesel oil. After these initial tests, the tractor was set up for\ud normal field operations, in which both the engine curves and lubricant quality were periodically monitored. These surveys indicated\ud no significant reduction in engine performance; however, the lubricant was consequently diluted and contaminated by biodiesel, which\ud caused the lubricant properties to considerably worsen. However, on the basis of the chemical–physical analysis, reducing the oil\ud change interval from 200 h (manufacturer’s indications for the engine when operating with diesel oil) to 100 h would compensate for\ud this progressive quality decline. At the end of the trials, the engine was disassembled to check the condition of its components; wear\ud and lacquer-like coating phenomena were observed, and their levels were acceptable. The obtained results demonstrated that B100\ud can effectively substitute for diesel oil in a standard compression-ignition engine: the power change is not perceptible during normal\ud operation of a tractor, and no particular problem will arise in the engine during its life if the lubricant is changed every 100 h