COMPARATIVE PERFORMANCE OF SOLAR TUNNEL GREENHOUSE AND OPEN SUN DRIING SYSTEMS DURING SEEDLESS GRAPE DRYING

ABDELLATIF, S. M; MOHMED, A. T.; MOSAD, G. A.

doi:10.21608/mjae.2010.104822

COMPARATIVE PERFORMANCE OF SOLAR TUNNEL GREENHOUSE AND OPEN SUN DRIING SYSTEMS DURING SEEDLESS GRAPE DRYING

Document Type : Original Article

Authors

Dept. of Agricultural Engineering, Faculty of Agric. Mansoura University, Egypt.

10.21608/mjae.2010.104822

Abstract

Drying is simply the process of moisture removal from an agricultural product, and can be performed by different methods. The main purpose of this research work was to study the thermal performance of two different solar driers (active and passive dryers) based on the energy balance equations for the drying air and the drying product during dehydration process of seedless grapes in August 2009 under the climatic conditions of El-Mansoura city (31.05ºN and 31.37 ºE), Egypt. Three identical solar tunnel greenhouse driers (STGD) were functioned as an active solar drier, and an open sun drier (OSD) under direct solar radiation without cover (as a passive solar drier) to dry seedless grapes. The three active solar driers were operated under three different mass flow rates of 0.122, 0.183, and 0.259 kg/s. Three different shapes of grapes (clusters, parts, and grains) with total quantity of 33 kg, were spread on wire mesh tray with floor surface area of 2.0 m². The results of greenhouse solar driers were compared individually with open sun drying. During the drying process, it was observed that, the hourly average air drying temperatures inside the three active solar dryers were increased to 49.9, 45.5, and 40.1ºC, respectively, whereas the hourly average ambient air temperature was 31.6ºC. The seedless grapes could be dried from initial moisture content of 79.1%wb to 17.1, 18.5, and 20.8%wb within drying time of 61, 61, and 71 hrs, using the three active solar dryers, respectively, while it was taken 96 hrs under open sun drying method to reach the final moisture content of 21.2%wb. The daily average thermal efficiencies for the four different solar drying modes, respectively, were 22.37%, 21.57%, 19.12%, 1and 10.81%. The quality of raisin (dried grapes) in terms of physicochemical parameters such as colour retention and water activity were evaluated.
The overall study concluded that good quality dehydrated raisin could be produced by using active solar dryers as compared with passive sun drying method. The produced raisin of grapes under different drying methods had various colours. They, respectively, were light brown and dark brown when the grapes dried under active solar dryers and passive sun drying method. The experimental work showed that, the solar tunnel greenhouse drying (active solar dryer) was satisfactory and competitive to a natural convection solar drying process (passive dryer).

Keywords

Main Subjects

Processing Engineering of Agricultural Products

References

Abdellatif, S. M. ; and Helmy, M. A. (1993) "Solar dryers utilization in clover drying for providing forage materials in critical feed period" J. Agric. Sci. Mansoura University, 18(8):2375-2383.

AOAC (1995)“Official methods of analysis of the association of official analytical chemists”. 14th Ed. Published by the Association of Official Analytical Chemists, Arlington, Virginia, 22209 USA.

Ayensu, A. (1997) "Dehydration of food crops using a solar dryer with convective heat flow" J. of Solar energy, 59(4-6):121-126.

Bargach, M. N. ; Tadili, R. ; Dahman, A. S. ; and Boukallouch, M. (2000) "Survey of thermal performances of a solar system used used for heating of agricultural greenhouses in Morocco, Renewable Energy, 20:415-433.

Condori, M. ; and Luis, S. (1998) "The performance of forced convection greenhouse driers" Renewable Energy, 13(4):453-469.

Condori, M. ; Echazu, R. ; and Saravia, L. (2001) "Solar drying of sweet pepper and garlic using the tunnel greenhouse drier" Renewable Energy, 22(4):447-460.

Dickerson, R. W., Jr. (1969). Thermal properties of foods. In "The freezing preservation of foods" 4th ed, vol.2 (D.K. Tressler, W.B Van Arsdel, and M.J. Copley, eds.) pp.26-51 AVI Publ.co. Westport, Connecticut, cited by Singh, R. P. and Heldman, D. R. (1993)

Duffie, J. A. ; and Beckman, W. A. (1991) "Solar engineering of thermal processes" John Wiley and Sons, New York, USA.

El-Ghetany, H. H. (2006) "Experimental investigation and empirical correlations of thin layer drying characteristics of seedless grapes" Energy Conservation and Management, 47:610-1620.

El-Sahrigi, A. F. ; Matouk, A. M. ; Abdellatif, S. M. and Awad, A. S. (2007) "Development and evaluation of a portable grapes dryer" Egypt Journal Agriculture Research, 85(1).

El-Sebaii, A. A. ; Aboul-Enein, S. ; Ramadan, M. R. I. ; and El-Gohary, H. G. (2002a) "Experimental investigation of an indirect type natural convective solar dryer" Energy Conservation and Management, 43:2251-2266.

El-Sebaii, A. A. ; Aboul-Enein, S. ; Ramadan, M. R. I. ; and El-Gohary, H. G. (2002b) "Empirical correlations for drying kinetics of some fruits and vegetables" Energy, 27(9):845-859.

Ibrahim, H. I. K. (1990) "Solar energy dehydration of fruits and vegetables and its effects on the enzymatic activities of the process" Unpublished, M.Sc. Thesis, Departement of food Sci., Dep., Fac. Of Agri., Ain Shams Univ. Egypt.

Jayaraman, K. S. ; and Gupta, D. K. (1995) "Hand book of industrial drying" Marul Dekker Inc.

Kumar, A. ; and Tiwari, G. N. (2006) "effect of shape and size on convective mass transfer coefficient during greenhouse drying (GHD) of Jaggery" J. of Food Engineering, 73:121-134.

Kumar, A. ; and Tiwari, G. N. (2007) "Effect of mass on convective mass transfer coefficient during open sun and greenhouse drying of onion flakes" J. of Food Engineering, 79:1337-1350.

Matteo, M. D. Luciano, C. L. ; Galiero, G. ; and Crescitelli, S. J. (2000) "Thin layer drying models of grapes" J. of Food Engineering, 46:83-89.

Pangavhane, D. R. ; Sawhney, R. L. ; and Sarsavadia, P. N. (1999) effect of various dipping pretreatment on drying kinetics of Thompson seedless grapes" J. of Food Engineering, 39(2):211-216.

Timoumi, S. ; Mihoubi, D. ; and Zagrouba (2004) "Simulation model for a solar drying process" Desalination, 168:111-115.

Tiwari, G. N. (2003) "Greenhouse technology for controlled environment" New Delhi: Narosa Publishing House.

Tiwari, G. N. ; Bhatia, P. S. ; Singh, A. K. ; and Goyal, R. K. (1997) "Energy balance equation for the drying product" Energy Conservation and Management, 38:751-759.

Yaldiz, O. ; Ertekin, C. ; and Uzun, H. I. (2001) "Investiagtion of a thin layer solar drying of sultana grapes" Energy, 26:457-465.