CALCULATIONS :

At Pressure = 1.5 cm of water

Weight of dry solid, S = 100 gm

Amount of initial moisture = 15 ml

Weight of solid, W= solid + water

Moisture content present in solid,

We have the experimental data as :

 

Time ,t (sec)	Wt. of solid(solid + water ) W (gm)	Moisture content present in solid X (gm water/gm of dry soild)
0	115	0.15
3	112	0.12
6	109	0.09
9	107	0.07
12	105	0.05
15	103	0.03
18	101	0.01
21	100	0

 

Now we plot a X vs t plot as shown

From this plot we calculate the slope = -dx/dt.

Now we have the drying rate as

For a constant area we hve the drying rate equation as :

Thus we have the table as :

Time,t (sec)	Wt. of solid (solid + water ) W (gm)	Moisture content present in solid X (gm water/gm of dry soild)	Slope = -dx/dt	N(Area const) gm/sec
0	115	0.15	0.0102	1.02
3	112	0.12	0.009324	0.9324
6	109	0.09	0.008448	0.8448
9	107	0.07	0.007572	0.7572
12	105	0.05	0.006696	0.6696
15	103	0.03	0.00582	0.582
18	101	0.01	0.004944	0.4944

Finally we plot a graph between X vs N as shown :

The same steps are repeated for other runs at different operating conditions.

 

COST CALCULATIONS :

Total time of drying = 21 min

Therefore No. of batches processed in a day = 24*60/21 = 68.57

Amount dried in one batch = 100 Kg

Therefore total weight = (100*68.57)Kg

Let us consider an orificemeter with the following diameters:

Diameter of the pipe , d₁ = 0.039 m

Diameter of the orifice hole , d₂ = 0.052 m

Co-effecient of discharge , C_d = 0.6

Therefore the areas are :

Area of the pipe , A₁ =( 3.14*(0.039)²)/4 = 0.00119 m²

Area of the orifice hole , A₂ = ( 3.14*(0.052)²)/4 = 0.00212 m²

Now we have the volumetric flow rate as :

 

 

where H is

= 1.5*((1000/1.2)-1)/100 m

=12.485 m

Therefore the volumetric flow rate = 0.013554 m^3/s

The mass flow rate G :

 G = Q * Density of air

= 0.013554 * 1.2

= 0.016265 Kg/sec

We have the specific heat of air C_p= 1.005 kJ/kgK

Temperature at which drying takes place = 340 K

Therfore amount of heat removed Q₁

=0.016265 *1.005 * (340-298)

= 0.683472 KW

= 3515.001 KWH(taking effeciency as 0.7)

Let us assume three industrial rate to be Rs 10 per unit

Therefore cost = 35150.01Rs

Cost per unit weight = 5.12Rs/Kg.