Development of automation system of laboratory type shelves dryer for medicinal and aromatic plants and determination of its performance

The scope of this research thesis includes development of three different circuit design; two identical circuit design for measurement of temperature and one circuit design for data acquisition of lab scale shelf dryer on drying of medicinal and aromatic plants. Therefore 2 different software programs were developed for (i) temperature and humidity hardware and (ii) online weighing recording unit. Measured data can be effectively transferred and monitored to PC. Rosemary was chosen as the test material for testing of the software. Drying tests were done at 42, 45 and 48 oC temperature set points. It has been determined that both automation hardware and the software were successful. Software is able to compute mean values of humid exhaust air from 4 shelves and end drying process automatically. In addition mean power consumption of dryer set at 45 oC was determined. According to the results at the condition of both heater and fan are on, 3.16 kW power consumption at current value of 7.61 A was recorded. Considering the specific energy consumption related to the drying temperature, the results showed that 5.70 kWh energy is required for removing of 1 kg of water and similarly 5.71 Drying of rosemary were completed at 16.12, 18.00 and 20.05 hours for temperature set points 42, 45, 48 ° C respectively. Increase in temperature resulted to decrease of drying time. Rosemary drying experiment showed that materials at SHELF II and SHELF III dries faster than other materials located at the other shelves.Rosemary essential oil quantity of the dried sample showed that, dried rosemary had essential oil loss: 2.74% at 42 °C; 7.31 % at 45 °C and 5.02 % at 48 ° C. The color values between fresh rosemary and dried rosemary indicated by L* value which is light-dark indicator have showed that L* value was decreased, the redness level indicator a* value increased and yellowness degree b* value also decreased. It has been concluded that the when the termination parameter of drying process was set to taking out of the products from the shelves decided by humidity values via software, can effectively increase the efficiency of dryer. Therefore, independent control of the dryer shelves for making a new design of electronic circuit and control system would be beneficial.