Research of the Effect of Different Circular Moist Object Geometries for Air Jet Impingement Drying on Heat and Mass Transfer

Year 2019, Volume: 24 Issue: 1, 51 - 62, 30.04.2019

Doğan Engin Alnak , Koray Karabulut

https://doi.org/10.17482/uumfd.360168

Abstract

Drying is one of the most used methods for
long-term storage by removing water from food. The physical and chemical changes occurring during
storage are minimal due to the reduction of considerable amount of water and
microbial activity of the food. In the present study, the effect of the two
different new moist object geometries with whole and reverse semi-circular on
the heat and mass transfer enhancement of drying with air jet was numerically
examined. The drying jet was a laminar and 2D jet stationed at a constant jet
distance (H) from the moist object. The diameter of the moist object, jet distance
from the moist object and jet initial height were fixed for all cases. Streamlines
and isotherms were acquired around the objects for different jet Reynolds
numbers. A finite volume method was used to solve the governing equations by
using ANSYS Fluent 17.0 software program. Calculations were carried out for
different Reynolds numbers, namely, Re=100, 200 and 300. It was found good
agreement with experimental and numerical data available in the literature. The
results showed that the geometry of whole circular moist object had better
performance of heat and mass transfer than that of the reverse semi-circular
moist object geometry. In addition, increasing Reynolds number showed a
positive effect on heat and mass transfer. Locally, jet drying was found to be
most effective near the stagnation point on the leading side of the objects.

Keywords

Drying, Air jet impingement, Mass transfer, Moist object, Numerical analysis

HAVA JETİ ÇARPMALI KURUTMA İÇİN FARKLI DAİRESEL NEMLİ NESNE GEOMETRİLERİNİN ISI VE KÜTLE TRANSFERİ ÜZERİNDEKİ ETKİSİNİN ARAŞTIRILMASI

Abstract

Kurutma, gıdadan suyun uzaklaştırılarak uzun
süreli depolama için en çok kullanılan yöntemlerden biridir. Kurutma ile gıdadaki su
miktarı ve mikrobiyal aktivitenin önemli ölçüde azalması nedeniyle depolama
boyunca meydana gelen fiziksel ve kimyasal değişimler en az seviyede
olmaktadır. Bu çalışmada, iki farklı
yeni nemli nesne geometrisi olan tam ve ters yarı dairesel nesnenin hava jeti
ile kurutulmasının ısı ve kütle transferi artışı üzerindeki etkisi sayısal
olarak incelenmiştir. Jet kurutması, nemli nesneden sabit bir jet uzaklığında
(H) konumlandırılmış olup laminer ve iki boyutludur. İncelenen tüm durumlar
için nemli nesnenin çapı, nemli nesneden olan jet uzaklığı ve jet giriş
yüksekliği sabit olarak alınmıştır. Nesnelerin etrafındaki akım çizgileri ve eş
sıcaklık eğrileri farklı jet Reynolds sayıları için elde edilmiştir. Korunum denklemlerini
çözmek için sonlu hacim yöntemi olan ANSYS Fluent 17,0 bilgisayar programı
kullanılmıştır. Hesaplamalar, Re = 100, 200, 300 olarak farklı Reynolds
sayıları için yapılmıştır. Çalışmanın, literatürde var olan deneysel ve sayısal
çalışmayla iyi bir uyum içerisinde olduğu bulunmuştur. Sonuçlar, tam dairesel
nemli nesne geometrisinin ters yarı dairesel nemli nesne geometrisinden daha
iyi ısı ve kütle transfer performansına sahip olduğunu göstermiştir. Ayrıca,
Reynolds sayısının artışının ısı ve kütle transferi üzerinde olumlu bir etkiye
sahip olduğu görülmüştür. Yerel olarak, jet kurutmanın nesnelerin ön
taraflarındaki durma noktasına yakın daha etkili oldukları bulunmuştur.

Keywords

Kurutma, Hava jeti çarpması, Kütle transferi, Nemli nesne, Sayısal analiz

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