بررسی برخی پارامترهای کیفی و ترمودینامیکی خشک‌کردن ورقه‌های کیوی در یک خشک‌کن بازگردشی مجهز به پمپ حرارتی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 عضو هیئت علمی/گروه مهندسی مکانیک بیوسیستم، دانشکده مهندسی زراعی، دانشگاه علوم کشاورزی و منابع طبیعی ساری

2 مکانیک بیوسیستمٰ دانشگاه علوم کشاورزی و منابع طبیعی ساری

چکیده

خشک­کردن با کاهش فعالیت­های میکروبی، زمان ماندگاری محصول را افزایش و با کاهش وزن و حجم مواد، بسته بندی، حمل و نقل و انبارداری محصولات را سهولت می­بخشد. شاخص­های کیفی و پارامترهای ترمودینامیکی از موارد مهم قابل بررسی در خشک­کردن مواد غذایی و محصولات کشاورزی می­باشند. هدف از این پژوهش بررسی تاثیرات بازگردش هوا و پمپ حرارتی بر شاخص­های کیفی (تغییرات رنگ، بازجذب آب و pH) و پارامترهای ترمودینامیکی (بازده حرارتی، حرارت و توان مخصوص مصرفی، ضریب خشک­شدن و بازده همرفتی) خشک­شدن کیوی می­باشد. در این پژوهش از سه سطح بازگردش ( 0%، 50%، 100%)، سه سطح دمای خشک­کردن (45، 55، 65 درجه ­سلسیوس) و دو سطح با و بدون استفاده از پمپ حرارتی استفاده شد. نتایج نشان داد که با افزایش میزان بازگردش از 0% به 50% تغییرات رنگ افزایش و از 50% به 100% تغییرات کلی رنگ کاهش یافت و با بکارگیری پمپ حرارتی میزان تغییرات کلی رنگ کاهش یافت. همچنین با افزایش بازگردش از 0% به 50% میزان pH افزایش و از 50% به 100% میزان pH  کاهش یافت. بیشترین بازجذب مربوط به بازگردش 100% و با وجود پمپ حرارتی بود. بالاترین میزان حرارت و توان مخصوص مصرفی در دمای 45 درجه سلسیوس، بازگردش 0% و با خاموش بودن پمپ حرارتی به ترتیب به میزان 37/73 و 57/83 مگاژول بر کیلوگرم و پایین­ترین میزان این دو پارامتر در دمای 65 درجه سلسیوس، بازگردش 100% و با روشن بودن پمپ حرارتی به میزان 15/14 و 01/27 مگاژول بر کیلوگرم بدست آمد. همچنین نتایج نشان داد که ضریب خشک­شدن، بازده حرارتی و همرفتی با افزایش دما و بازگردش و با بکارگیری پمپ حرارتی روند صعودی داشت.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating Some Quality and Thermodynamic Parameters of Kiwifruit Thin Layer Drying in an Air Recycling Dryer Equipped with Heat Pump

نویسندگان [English]

  • Reza Tabatabaei kolor 1
  • Iman Mohammadi 2
  • Ali Motevali 2
1 Scientific member/Department of Mechanics of Biosystems Engineering, Faculty of Crop Engineering, Sari University of Agricultural Sciences and Natural Resources
2 Biosystems Engineering, Sari Agricultural University
چکیده [English]

Drying reduces microbial activity, increases storage time, and facilitates packaging, transportation and storage of crops by reducing weight and volume of materials. Quality indices and thermodynamic parameters are as important cases in drying food and agricultural crops. The aim of this research is investigating the effects of air recycling and heat pump on quality indices (color changes, water rehydration and pH) and thermodynamic parameters (thermal efficiency, temperature, specific power consumption, drying coefficient and convection efficiency) of kiwifruit drying. In this research, three levels of recycling (0, 50% and 100%), three drying temperatures (45, 55 and 65ºC) and two levels with and without using a heat pump were used. Results showed that by increasing recycling from 0 to 50% color changes and pH increased and from 50% to 100% both them reduced. The maximum rehydration was related to 100% recycling with heat pump. The highest temperature and specific power consumption were 73.37 and 83.57 Mj.kg-1, respectively at 45 ºC, 0% recycling and heat pump off. The lowest rate of these two parameters were 14.15 and 27.01 Mj.kg-1at 65 ºC, recycling 100% and heat pump on. Also, results showed that drying coefficient, heat efficiency and convective had an increasing trend by using heat pump and increasing air temperature and recycling.

کلیدواژه‌ها [English]

  • Kiwifruit
  • color changes
  • rehydration
  • heat efficiency
  • specific power consumption
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