L. R. Walton

Thermal Conductivity of Baled Burley Tobacco

ABSTRACT The effective thermal conductivity of baled burley tobacco was determined with a thermal conductivity probe as a function of the major parameters expected to influence the conductivity. The mean value of effective thermal conductivity of baled burley tobacco was higher parallel to the leaf (0.0762 W/m°C) than it was perpendicular to the leaf (0.0453 W/m°C) because the heat was conducted through continuous solid leaf material in the parallel direction while it had to pass through successive air spaces in the perpendicular direction. The effective thermal conductivity increased linearly with increasing moisture content and increasing bulk density. The effective thermal conductivity was highest at the center of the bale and progressively lower toward the edge of the bale..

New Model for Determining Thermal Diffusivity with the Thermal Probe

ABSTRACT Anew model for the temperature rise of an infinite medium with a thermal probe is developed which accounts for the finite diameter and specific heat of the probe. The new model is more accurate than the old model as demonstrated during the determination of thermal diffusivity of burley tobacco in bales. Multiple thermocouples in the medium and multiple probings are suggested for the determination of thermal diffusivity. Reduction of moisture diffusion to a negligible level is discussed.

Sensitivity of Air-Type Solar Collector Efficiency to Design Changes

ABSTRACT THE sensitivity of the thermal efficiency, the collector efficiency factor and the collector loss coefficient, to design parameter (top loss, bottom loss, convective and radiative heat transfer in the collector) changes is presented graphically for three common air-type solar collectors. Interactions are shown to exist as design parameters change. Design parameter changes have different effects depending on location of the flow channel. The most critical component of air-type solar collector design is the convective heat transfer coefficient in the flow channel since its effect on efficiency may be positive or negative depending on collector type and operating conditions.

Tobacco Moisture Content Determination by Microwave Heating

ABSTRACT SAMPLES of shredded burley tobacco leaves were heated for a fixed time interval in a microwave oven and the resulting temperature rise was correlated to the sample moisture content. The results showed that the moisture content of tobacco leaves, from 9 to 23 % wb, is a function of temperature rise when 50 g samples are heated for 18 s at maximum power of 625 W in a home microwave oven. The accuracy is improved with shredded samples by reducing the uneven heating that occurs with whole leaf samples, lowering the standard error for the prediction equation from 1.04 % wb to 0.68 % wb. Much of the remaining uneven heating is due to the inadequacy of the microwave applicator.

Development and Evaluation of a Cable-hoist System for Housing Burley Tobacco

A unique cable-hoist system has been developed that can reduce the labor by up to 45% for placing stalk-harvested tobacco in a barn for curing and later removing it for stripping. Workers are not required to climb and work in the barn, thus improving safety. Most of the physical drudgery is eliminated, thus offering desirable benefits to tobacco producers. Safety of operation has been a prime consideration in the development and evaluation of the method. A crew size of one or two workers can accomplish the same housing and bulking tasks of three to five workers by conventional methods. Labor savings do not compensate for the amortized cost of converting a conventional barn. However, new barn construction and installation of the system show a potential break-even situation for a 2 ha (5 acre) size in five to seven years.

Trail-type harvester for burley tobacco.

A trail-type harvester for burley tobacco was designed, built and tested. The machine cuts the plants, makes a 45° notch in the stalk near its base and conveys the plants to a three-person hanging crew that hangs them on portable handling frames. A tractor front-end loader is used to remove and replace frames. An independent hydraulic system was used to supply fluid to hydraulic motors driving the cutting and notching saws, conveyors, and frame indexing device. Harvesting rate for the three person hanging crew was 36.8 plants/min and the estimated field capacity was 0.1 ha/hr with a theoretical field efficiency of 77%. The system offers a potential labor saving of 63% when compared to the manual-harvest conventional system. Leaves lost with the machine amounted to 1.3% and 4% for KY-14 variety and TN-86 variety, respectively.

Mechanical Harvesting System for Burley Tobacco

A harvesting-handling system for burley tobacco was modified and field tested to evaluate its performance. The system utilizes a semi-mounted harvester to cut the plants, notch their stalks and convey them to a trailing wagon where workers hang the notched plants on wire-strung portable frames. A grasping chain conveyor was added at the front of the harvest to positively control the plants in the cutting and notching zone. An adjustable frame holder was added to the wagon which allowed the frame to be repositioned to provide working space for completely filling the frame. A quickly adjustable wagon tongue was provided which facilitated turning the machine at end of row. Test results showed that 94.7% of plants were successfully harvested and hung while 2.2% were lost from the conveyors and 3.1% were not properly notched for hanging. Leaves lost amounted to 18.7% and harvest rate was 40.5 plants/min.

Moisture Content as a Function of Temperature Rise Under Microwave Radiation

ABSTRACT SAMPLES of shelled corn and whole burley tobacco leaves were heated for a fixed time interval in a microwave oven and the resulting temperature rise was correlated to the sample moisture content. The results showed that the moisture content of tobacco leaves, from 14 to 24% wb, is a linear function of temperature rise when 50-g samples are heated for 18 s at maximum power of 625 W in a home microwave oven, although the accuracy is reduced by the uneven heating that occurs with whole leaf samples. For shelled corn, with 200-g samples heated for 50 s at 625 W at maximum power, moisture content from 8 to 16% wb is a function of temperature rise. For higher moisture content corn the technique must be changed so as to induce less temperature rise in the samples.

Notched burley tobacco system performance

Burley tobacco is a valuable crop that is still harvested manually. A system of harvesting and handling notched burley plants on wire-strung portable frames has shown potential to reduce labor requirements. The purpose of this research was to evaluate the performance of the system with a newly designed harvester. Specific objectives were to determine hanging rates of several two and three person hanging crews, leaf loss associated with each crew, the percentage of plants that had split-out or shallow notches and could not be hung, and the frame exchange time requirements during field operation and to compare curing of the tobacco on the wire-strung portable frames to tobacco cured conventionally. The results showed that the notched plant wire-strung portable frame system harvests 0.7 ha/day (1.7 ac/day) thus saving the burley tobacco producer up to 45% of the labor compared to the conventional system. Leaf loss can be held to the 5% level and the combined percentage of splitout and shallow notches can be held below 3%. Less skill and strength is required with the notched burley tobacco system than the conventional system. The three worker hanging crew functioned more smoothly than the two worker hanging crew but a slower tractor speed would correct the problem for the two worker crew. Tobacco harvested by the notched plant system was more susceptible to houseburn because of the higher density than tobacco harvested and cured conventionally. Tips of leaves near the concrete floor of the barn cured dark red because of the wet curing year.

A Portable Cantilever Frame System for Burley Tobacco

ABSTRACT AN experimental unitized burley tobacco handling system was developed and evaluated. The portable cantilever frame design was much easier and faster to load than previous portable frames. A labor reduction of 68% from field into the barn was achieved by this system when compared to the conventional system of housing burley tobacco in tiered barns. Stacking the 1983 portable cantilever frames three high in comparison to two high greatly improved barn utilization with only a slight increase in stacking time..