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

Utilization of Small Diesel Engine for Drying of Paddy

S. Sarker
Technical School and Colledge, Sunamganj

M. A. Basunia
Department of Farm Power and Machinery, BAU, Mymensingh

M. A. Rabbani
Department of Farm Power and Machinery, BAU, Mymensingh

Abstract/ Executive Summary:

A fixed bed rough rice dryer of base area 0.81 m² was designed and constructed on the basis of availabillty of harvested engine waste heat. The waste heat released from the cooling system of a small diesel engine (≈ 3.25 kW) was used for drying of farm crops. A fan was directly coupled with the crankshaft to move the air. The harvested engine waste heal was forced to pass through a suitable duct system to the dryer. The performance of the dryer was studied in drying 40 cm rough rice bulk depth amounting 200 kg. The waste heat Was sufficient to increase the temperature of the ambient air by 7 to 12 °C at an airflow rate of 8.80 to 5.70 m³/min. The initial moisture content of rough rice was 25.4% (w.b.). After continuous 8 hour drying the top layer moisture content was 18.6% (w.b.) and the bottom teller moisture content was 11.2% (w a.). The average final moisture content was 14.7% (w.b.) while the moisture gradient was 7.4% (w.b.). There was no significant difference in rough rice moisture content between the center and corner of the bin, which indicates drying uniformity across the bin cross section. This study shows that the waste heat of small diesel engine can be used as a source of energy for grain drying in low temperature.

Keywords: Diesel engine, Waste heat, Drying paddy

Location: Department of Farm Power and Machinery, BAU, Mymensingh

Start Date:

End Date:

Program Area: Farm Mechanization

Commodity: Drier

Objectives:

(1) To measure the availability of engine waste heat from a diesel engine (3.25kW) which can be harvested for paddy drying; and

(2) To evaluate the Performance of engine waste heated paddy dryer with available engine waste heat.

Methodology:

Construction of the dryer

In this study an air-cooled four-stroke cycle diesel engine was used. The brake output of the engine was 3.25 KW at 3000 rpm and cooling efficiency of 30 percent was used. A forward curved centrifugal fan usually used for ventilation was used. The diameter of the fan was 18 cm and it was directly coupled with the engine flywheel (crank shaft). The coupling is very easy and cost effective. Diagram of the vertical section of the engine fan combination dryer duct system, plenum chamber, and the flat bed 'dryer chamber. The dryer chamber is an open-ended box 90 x 90 cm in cross section and 60 cm deep. A wire screen supported by mild steel rod net spacing 6 x 6 cm was used as the dryer bed. The mild steel rod net supported the wire screen to hold the grain mass. A wooden box made the housing of the fan and the duct was connected with the box. A PVC pipe 15 cm diameter and 100 cm long was used for the duct. The lower Part of the -Plenum chamber was connected with a 90⁰ elbow with the duct. To reduce the loss of heat by conduction the duct and the plenum chamber were insulated Properly.

Measurement of airflow

A standard Pitot tube and glass tube manometer measured the airflow rates of the drying air. One of the Pitot tube was inserted at the center of the straight duct with one of its opening facing opposite to the direction of airflow to measure the sum of static and velocity pressure of the drying airflow. The other one was inserted such a way so that one of its openings was with the same surface of the inner wall of the straight duct to measure the static pressure of the drying airflow. The other opening ends of the pitot tubes were connected to the glass tubes of the manometer by plastic tubes. Both pitot tubes were inserted 60 cm apart from the fan housing to avoid the turbulence of airflow during measuring by making holes on the surface of the straight duct. Water was used in the manometer. The average velocity of drying air was calculated from the difference of the observed average total pressure and the static pressure. The velocity pressure of the drying air was used to calculate the velocity of the airflow, and then airflow rate was calculated from the known area of the duct.

Engine waste heat

About 30% of the energy generated by the combustion process in the engine is transformed into useful work, about 30% is vented with exhaust gases, and 10% is lost due to radiation and friction, while the remaining 30% is dissipated by the cooling system. The dissipated heat from the cooling system and the radiated heat was mostly used in this experiment for the heating of drying air. The total heat energy to be utilized (HEA) to heat the drying air at any given rpm of the engine is calculated.

Moisture content measurement

The moisture content was measured at the end of drying period and during drying using grain samples collected from the top middle and bottom layers. Grain samples were collected from the middle and bottom layers by manual probe and the top layer sample was picking. At each - layer, grains were collected from two positions; center and near the wall of the dryer. At each position, moisture content was determined individually to know the moisture gradient across the horizontal direction and the average was made at each layer. So the moisture content at each layer represented the average of three samples. The moisture gradient across the vertical direction was determined from the difference of moisture content between the top and bottom layer of the grain bed. The average moisture content of the entire grain bed was an average of moisture readings from top, middle and bottom layers. A single grain digital moisture meter was used for measuring the moisture content.

Source of Information: Bangladesh J. Prog. Sci. & Tech. 3(2): 105-110, July 2005 ISSN 1609-526X

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the study It was established that a small diesel engine can be used for a mechanical dryer from which 71.99 MJ/hr energy can be harvested with the help of a direct coupled (connecting directly with engine crank shaft) forward curve centrifugal fan and the amount of beat energy harvested was sufficient to dry 200 kg of rough rice. After 8-hour operation of the dryer the moisture content of rough rice reduced to 14.7% w.b. where the initial moisture content was 25.4% w.b., at the average ambient temperatures of 31 ⁰C end the relative humidity of 82%. The engine consumes only 3-liter fuel during 8 hour of operation that was cost effective. No extra capital investment and operating cost is necessary for supplemental heating of drying air. Even the provision cart be easily made to use the same engine simultaneously for dual purposes like drying and pumping water as the dryer fan consume a little power from the engine as compared with the engine power. The use of this static flat bed dryer in rural areas where electricity is not available should encourage the harveating of improved rice variety with field moisture content as high as 23% (w.b.) to minimize the harvest and shatter losses.

Knowledge Management: Journal