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In this research, convective and microwave drying characteristics, energy requirement and color changes of sorbus fruits (Sorbus domestica L.) were reported. Sorbus fruits were dehydrated in a computer connected parallel air flow type dryer and in a microwave oven dryer. Samples of freshly harvested sorbus fruits were dehydrated under two air temperatures of 50° and 70°C and at three microwave power levels of PL-1, PL-2 and PL-3. Selected drying air velocity was 0.30 m/s for both temperatures. Sorbus fruits were dehydrated from the initial moisture content of 300 (percentage dry basis) to a final moisture content of 8...10%. During convective drying experiments, product were weighted automatically by the balance per 5...10 minutes. Data were transferred to the computer and processed by a software. During microwave drying, the product were weighted and data recorded manually per 15...60 minutes. The influence of drying method, drying air temperature and microwave power level have also been studied. Hunter L, a, b values system was also used to evaluate changes in total color difference ( E) on dried products. The results showed that convective drying air temperature and microwave oven power levels influenced the total drying time, total energy requirement, specific energy requirement and color difference for sorbus fruits. The minimum specific energy requirement were determined as 0.69 kWh/kg and 37.07 kWh/kg for 70°C and PL-3 respectively. 50° C drying air temperature and PL-1 was found to yield better quality product in terms of color retention of Hunter L, a, b and E. As a result, to reduce drying energy consumption and to keep better color retention, convective drying can be recommended for this application.

In this research, convective and microwave drying characteristics, energy requirement and color changes of nettle leaves (Urtica diocia L.) were reported. Samples of freshly harvested nettle leaves were dehydrated under three air temperatures of 50 °C, 60 °C and 70 °C and at three microwave power levels of PL-1, PL-2 and PL-3. Selected drying air velocity was 0.30 m/s for all temperatures. This is coming from the fact that it was understood from the preliminary studies that the temperature less than 50 °C and the air speed more than 0.30 ms-1 increase the drying time and energy requirement, extremely for these products. Nettle leaves were dehydrated from the initial moisture content of 320 (percentage dry basis) to a final moisture content of 7 % to 9 %. During convective drying experiments, product were weighted automatically by the balance per (5 to10) min. Data were transferred to the computer and processed by a software. During microwave drying, the product were weighted and data recorded manually per (15 to 60) min. The influence of drying method, drying air temperature and microwave power level have also been studied. Hunter L, a, b values system was also used to evaluate changes in total color difference (DE) on dried products. The results showed that convective drying air temperature and microwave oven power levels influenced the total drying time, total energy requirement, specific energy requirement and color difference for nettle leaves. The minimum specific energy requirement were determined as 6.95 kWhkg-1 and 23.63 kWhkg-1 for 70 °C and PL-2 respectively. 70 °C drying air temperature and PL-3 was found to yield better quality product in terms of color retention of Hunter L, a, b and DE. As a result, to reduce drying energy consumption and to keep better color retention, convective drying can be recommended for this application.

ÖZET Bu çalışmada; keten lifi, mısır sapı, ayçiçeği sapı, su kamışı, arpa samanı gibi beş farklı doğal destek malzemesi ile cam yünü ve karbon lifi gibi iki farklı sentetik destek malzemesi belirli oranlarda (2.5 g lif/72.5 g PE, 5 g lif/70 g PE, 7.5 g lif/67.5 g PE ve 10 g lif/65 g PE) yüksek yoğunluklu polietilen matris içerisine yerleştirilerek, lif takviyeli kompozit lamine levhalar üretilmiştir. Liflere ya da matrise herhangi bir ön kimyasal işlem uygulanmamıştır. Kompozit lamine levhalar presle kalıplama yöntemi ile üretilmiş, sonrasında ise çekme ve ısı testlerine tabi tutulmuşlardır. Sonuçlar; kompozit numunelerin çekme mukavemetlerinin desteklenmemiş polietilen numunelere göre daha düşük olduğunu fakat mısır sapı, ayçiçeği sapı ve su kamışı ile desteklenmiş kompozit numunelerin, cam yünü ve karbon lifi ile desteklenmiş kompozit numunelere çok yakın çekme mukavemetine sahip olduğunu göstermiştir. Ayrıca kompozit numuneler yüksek sıcaklığa karşı, desteklenmemiş polietilene göre daha az deformasyon göstermişlerdir.Production of different composite materials and determination of some technical properties Anahtar Sözcükler: Doğal lif Kompozit malzeme Sentetik lif Yüksek yoğunluklu polietilen ABSTRACT In this study, five different natural reinforce materials as flax fiber, corn stalk, sunflower stalk, reedmace, barley straw and two different synthetic reinforce materials as glass fibers and carbon fibers with different ratios (2.5 g fiber/72.5 g PE, 5 g fiber/70 g PE, 7.5 g fiber/67.5 g PE and 10 g fiber/65 g PE) were placed inside high density polyethylene matrix to produce fiber reinforced composite. No chemical pretreatment were made to the fibers or the matrix. Composite laminate sheets were produced by compression molding process, then tensile tests and heat tests were conducted. Results show that; tensile strengths of the composite samples are lower than unreinforced polyethylene but corn stalk, sunflower stalk and reedmace reinforced sample's tensile strengths are very close to the composite samples reinforced with glass and carbon fibers. Furthermore most composites show lower deformation against high temperature than unreinforced polyethylene.