Fabrication and Testing of a Manual Charcoal-Fired Groundnut Fryer

Groundnut is an agricultural product that is of great value to both man and animals. It serves as raw material for industries. Frying is the process of generating characteristic aroma, flavour and colour required by consumers for acceptance of such fried food. The wide range usage of groundnut and its products has led to increase in its demand. However, the local methods of roasting Groundnut seeds after it has been shelled has some associated problems and difficulties which make it ineffective, laborious and time consuming. A manually operated Groundnut seed roaster was constructed with the aim of improving on the traditional methods commonly used in the Nigeria. The machine shows the roasting efficiency (Er) to be in the realm of 98.0% with percentages of seed damaged (loss) in the range of 2.00-20.0%. The average and optimum time for roasting was estimated to be in the range of 4 minutes.


MATERIALS AND METHODS CONSTRUCTION THEORY AND DEVELOPMENT
In order to achieve a good construction, the selection of materials plays a vital role. Therefore, a good, rigid and durable structure of machinery indicates a good selection of materials during its construction. This chapter therefore, present theory and the design analysis of some machine part and the applicable engineering graphic representation.

DESCRIPTION OF THE GROUNDNUT ROASTING MACHINE
The major components of the machine are the loading opening in the drum as shown in plate 1 and 2, roasting chamber, the shaft, the paddles, the heating unit (charcoal), the discharge outlet and handle. The hopper is made up of welded metal sheets together with a flat metal sheet used for closure and exposure of the hopper.
The roasting compartment is made of a cylindrical metal plate of 28 cm diameter and 46 cm length with 2 mm plate thickness, a solid shaft of diameter 2 cm and length 55 cm that carries a set of paddles or flange of 22 x 40 cm made of metal sheet with 2 mm thickness, a metal plate of 46 x 36 cm containing charcoal placed under a metal plate at the bottom of the roasting chamber and handle for efficient operation.

DESCRIPTION OF MACHINE ELEMENT
i. Loading Unit: This is a rectangular shaped opening situated at the drum. It is the inlet in which the groundnut seeds are admitted into the roasting chamber with a dimension of 41.5 x 13 cm. ii. Roasting Chamber: This is the core of the roasting section of the machine, it consists of a drum and it also carries the rotating shaft which houses the paddles. It is made of mild steel plate and supported by two bearing. Heating chamber is housed in this chamber. iii. Heat Chamber: This is where the hot coals are kept, just below the roasting chamber, with perforations to allow the entrance of air. iv. Frame: This is the mounting support of all the components of the machine. It is made of metal angle rod with a thickness of 5mm welded alongside the units which provide support on which the whole unit rest. v. Handle: The handle in this case is the prime mover which is 20 cm long, this is connected to the shaft which turns the paddles/flanges in the roasting chamber (drum).

DESIGN CALCULATIONS
Before the machine was constructed, the following design calculations were carried out:

Shaft Design
The shaft design will be based on maximum shear theory (Hall, 1988). Diameter of the shaft is given as Where: = allowable shear stress = 42 N/m 2 (maximum allowable stress for shaft ASME code of design of transmission shaft) Mb = bending moment on shaft Mt = Torsional moment Kb = combined shock and factor applied to bending moment Kt = combined shock and fatigue factor applied to torsional moment Using Kb = 1.5 and Kt = 1.0 (Hall, 1988)  Due to factor of safety 40mm diameter shaft will be recommended.

MODE OF OPERATION
The roaster employs the principle of heat absorption by the groundnut seeds and attains uniform roasting as a result of heat supplied from the heating element and the action of the paddles housed by the shaft which causes the cotyledon to rotate with the aid of the an attached handle. Harvested groundnut seeds with the desired moisture content are fed into the hopper of the roasting chamber when the medium (sand) already introduced attains a suitable temperature and the seed control device is opened to allow the seed to fall directly into the roasting chamber. The groundnut seed which are dropped into the roasting chamber mixes with the hot sand and it turns anti-clockwise at a given temperature to ensure even roasting. When the discharge unit of the roasting chamber is opened, the cotyledon and the bath moves out of the roasting chamber into the sieve suspended on top of the tray.

Performance Evaluation
The parameters used in evaluating the groundnut seed drum roaster are the roasting efficiency (Er)% and percentage seed loss. The mathematical for these parameters are. Roasting efficiency (i )% = k G G/ l m 100 … … … … … … … … … … … … … … (9) o ,/:C p -:9:C /< ---(q ) = k G G/ l m 100 … … … … … (10) Where: Wd = weight of roasted seed damaged (over roasted) Wr = weight of roasted seed not damaged Wt = total weight of seed roasted (Wr + Wd) Table 4.1 shows the comprehensive performance of the groundnut seed roaster. The evaluation parameters used are the roasting efficiency (Er) and percentage losses of seeds.

Discussion of Results
The roaster efficiency appears to be generally high in the range of 80.00 to 98.00% at four different level of roasting groundnut seeds in the drum roaster. Seed losses (EI), was observed but at a low level in the range of 2 to 20%. One of the distinguishing features of the roaster is that instead of using conventional firewood as the source of energy, wood Charcoal was used to supply heat the roaster.

CONCLUSION
The groundnut seed roaster constructed during this investigation was observed to roast groundnut seeds at faster rate than the traditional that was takes 20 -30 minutes and exposes the health of rural women to great danger. The drying required was observed to be lighter, because the moisture content required for frying is the moisture content require for the safe storage and preservation of groundnut seeds.

RECOMMENDATIONS
After achieving the aim and objectives of this research work, recommendations are made as follows: i. It is recommended that for optimum roasting the groundnut should be sun dried before roasting. ii.
Further investigation on other groundnut seed varieties should be carried out at various roasting moisture content to determine the optimum moisture level that would be convenient for roasting.