Agricultural Research Management Information System

Home
Research Summary
Search
About Us
- ARMIS
- Brochure
Contact Us
Report
User Request
Data Input
Help
- Operation Manual
  - PDF
  - Video
- Program Area & Commodity
We have reached 37600 number of research entries at this moment.

- Logout

Research Detail

Home
Research
Detail

Optimisation of Solar Tunnel Drier for Drying of Chilli Without Color Loss

M. A. Hossaina
FMP Engineering Division, Bangladesh Agricultural Research Institute, Gazipur 1701, Bangladesh

J. L. Woodsb
School of Agriculture, Food and Rural Development, University of Newcastle upon Tyne, upon Tyne NE1 7RU, UK

B. K. Balac
Department of Farm Power and Machinery, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh

Abstract/ Executive Summary:

A solar tunnel drier is optimised for drying of chilli in Bangladesh. The simulation model was combined with the economic model of the solar tunnel drier and adaptive pattern search was used to find the optimum dimensions of the collector and the drying unit. Two optimum designs are obtained. For design-1, both collector and drying unit are 14.0 m long and 1.9 m wide and for design-2, both collector and drying unit are 13.0 m long and 2.0 m wide. Both the collector and drying unit of basic mode drier are 10.0 m long and 1.8 m wide. The capacity of optimum mode driers is higher than the basic mode drier and achieves a cost saving of 15.9%. The pay back period of the basic mode drier is 4 years and optimum mode drier is about 3 years. Sensitivity analysis showed that the design geometry is sensitive to costs of major construction materials of the collector and air temperature in the drier. q 2004 Published by Elsevier Ltd.

Keywords: Color; Economic model; Forced convection; Optimisation; Simulation model

Location: Bangladesh Agricultural Research Institute, Gazipur.

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Chilli

Objectives:

To optimise the physical component of the solar tunnel drier for the drying of chilli efficiently and economically without loss of its color.

Methodology:

A solar tunnel drier consists of a plastic-covered flat plate solar collector and a drying tunnel. The drier is arranged to supply hot air to the drying tunnel using two small fans powered by a photovoltaic module. The heated air passes over and under the products spread in a single layer in the drying chamber and thus moisture is evaporated and carried away from the products. Considering an element, dx of the collector or drying unit from the inlet, energy balances on the collector. The bottom of the collector is provided with insulation and heat loss through the bottom is neglected. The surface area of side is small and heat loss through side is negligible. Air flows inside the collector (between the cover and absorber plate) along the length. Considering an element, dx of drying tunnel at a distance, x from the inlet of the drying unit.Heat balance on plastic cover of drying tunnel is the same as the cover of collector. The chilli in the solar tunnel drier is dried in a single layer thickness and heated air mainly flows above the chilli pods. Due to low airflow, the temperature below the chilli bed will come to equilibrium with the chillies quite rapidly. It is therefore, assumed that all airflow is above the chilli bed and the chillies to be standing on an impermeable adiabatic surface. It is also assumed that the tray is completely covered with chilli pods and there is no space between the adjacent pods. For calculation of the cost of drying, a simple annual cost model was used. The total cost of the solar drier consists of the cost of the collector, drying tunnel, fan and PV module. The materials used in collector and drier were GI sheet, timber, glass wool, MS rod, angle bar, polyethylene cover, rubber rope, aluminium U-channel, DC fan, PV module, GI pipe, plastic net and miscellaneous materials (screw, rivet, paint, etc.). Taking an interest rate of 12%, inflation rate of 15%, life of drier 10 years, number of working day per year 120 days and number of working hours per day 8 h, the drying cost per unit moisture removal for chilli was calculated. In carrying out the simulations, the system was assumed to be operated from 9:00 a.m. to 4:00 p.m. daily. The economic model was combined with the simulation model. For different combinations of drier geometry (length and width) under constraint conditions of colour as well as drying air temperature, the dimensions of the solar tunnel drier for minimum cost per unit moisture removal were determined. The optimum dimensions were determined by adaptive pattern search technique. The technique essentially consists of an exploratory search and a pattern search under constrained conditions. The optimisation programme was written in BASIC programme.

Source of Information: Renewable Energy 30 (2005) 729–742 (www.elsevier.com/locate/renene)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

The main feature of the optimum design is a relatively long collector. Two types of optimum designs are obtained. For design-1, both collector and drying unit are 14.0 m long and 1.9 m wide and for design-2, both collector and drying unit are 13.0 m long and 2.0 m wide. Both the collector and drying unit of basic mode drier are 10.0 m long and 1.8 m wide. There is no significant difference of efficiency between the basic mode and optimum mode driers. The capacity of optimum mode driers is higher than the basic mode drier and hence cost saving by 15.89%. Pay back period of basic mode drier is 4 years and optimum mode driers are about 3 years. Sensitivity analysis showed that the design geometry was not very sensitive to minor material costs, fixed cost and operating cost. The design geometry is sensitive to costs of major construction materials of the collector, solar radiation and air velocity in the drier. This optimisation technique may be applied for optimal design and construction of solar tunnel drier for drying of chilli and other crops.

Knowledge Management: Journal