EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF DOUBLE SLOPE SOLAR STILL Ishan Kossambe
Jun 13, 2015
EXPERIMENTAL AND COMPUTATIONAL ANALYSIS OF DOUBLE SLOPE SOLAR STILL
Ishan Kossambe
Need of the project
Fresh water is essential for all life forms on earth
The available fresh water on the earth is fixed, but the demand of fresh water is increased
The ocean is the only available source for large amount of water
But the ocean water contains high salinity, so there is a need to desaline the water
Problem Statement
Desalination of salt water using solar still which then can be used for drinking or other household purpose
Solar Still
Solar still is a device, which is used for desalination purpose Economical process but distillation rate is low Involves all the three modes of heat transfer The solar radiations falling on the glass cover pass through
the glass cover and strike the inside surface of the basin This leads to rise in temperature of the water and water
begins to evaporate. Temperature difference between water vapor and glass
leads to vapor condensation in glass cover The combination of gravity and surface tension causes
water to flow downwards and get collected in a trough leading into a storage tank
Experimental Setup
It is an insulated metallic basin covered by a transparent glass
Made up of GI sheet having a base area of 1.0 m x 1.0 m
The basin is double walled having 1” thermocol sheet sand-witched between the walls to reduce heat losses from walls.
The basin is painted with black epoxy paint from inside to increase its absorptivity and it is painted with silver enamel paint on the walls to create the adiabatic surface on the walls and reduce thermal losses
A transparent glass of 5 mm thickness covers the top of the still
Experimental Setup
Design Modifications
The setup available was very old The collecting passage was not having
proper slope First we tried to make the slope proper
using glass putty One more problem was with insulator
absorbing the condensed water This was eliminated by using a non
absorbing material (cello tape) placed over the insulator
Design Modifications
Still the collecting passage problem was not rectified
Then we tried sticking a electric pipe on to the glass surface itself
This pipe got bend due to intense sun heat Then electric pipe was replaced by high
temperature resistance pipe For the water to flow one side of the still
was lifted slightly by 5 mm
Experimental Procedure
Experiment was carried out from 1100 Hrs till 1300 Hrs
Solar still was filled with 10 liters of water
For every 20 min the reading were taken as tabulated below
Time Tg (oC) Tb (oC) Ts (oC) Ta (oC)Flux
(KW/m2)
Amount of water collecte
d
11:00 33 39 25 37.7 10.9
11:20 53 55 56 38 11.4 40
11:40 56.7 58.8 60 38 11.7 100
12:00 59 62.8 63.5 38.5 11.8 210
12:20 62 67 67 37.1 11.6 320
12:40 65.2 63.9 70 38.3 11.3 450
13:00 68 74 73 38 11.1 620
Observation and Calculations
Pw (Pa) Pg (Pa)
Expt flow rate
(ml/m2min)
hew hcwAnlytical flow rate
(ml/m2min)
0 0
16471 14259 2-
45.27002775-2.920248 20.4587631
19871 17027 3 -47.624171-
3.1156672
26.33361339
23321 18970 5.5-
50.44245846
-3.284999
9
32.58533648
27268 21785 6-
50.87247844
-3.486428
940.4365203
31089 25173 6.5-
67.83362287
-3.491067
5
46.16413147
35355 28495 8.5-
59.06693878-3.759033
56.52839511
Time vs Water Output
10:48 11:02 11:16 11:31 11:45 12:00 12:14 12:28 12:43 12:57 13:120
1
2
3
4
5
6
7
8
9
Water Output vs Time
ExperimentalAnalytical
Time
Wate
r o/p
(m
l/m
in)
Variation of Ambient temperature with time
10:48 11:02 11:16 11:31 11:45 12:00 12:14 12:28 12:43 12:57 13:1236
36.5
37
37.5
38
38.5
39
Variation of Amient Temperature with time
Ta (oC)
Time
Am
bie
nt
Tem
pera
ture
(oC
)
Variation of Solar Flux With Time
10:48 11:02 11:16 11:31 11:45 12:00 12:14 12:28 12:43 12:57 13:1210.4
10.6
10.8
11
11.2
11.4
11.6
11.8
12
Variation of Solar Flux with Time
Flux (KW/m2)
Time
Sola
r Flu
x (
KW
/m2)
PPM Test of water
Two samples were collected 1. Water which was put inside the solar still2. Water which was collected out from the
solar still These samples were tested for calculating
various salt contents like1. Hardness of the water (CaCo3)
2. Chloride content3. Sulphate content
Test for Hardness
1. Take 20 ml or suitable portion of sample diluted to 100ml in to a conical flask.
2. Add 1-2 ml buffer solution.3. Add 1 or 2 drops of Erichrome black T and titrate
with standard EDTA (0.01 M) till wine red colour changes to blue. Note down to vol. of EDTA required. (A)
4. Run a reagent blank if buffer is not checked properly. Note the Vol. of EDTA required by blank (B).
5. Calculate Vol. of EDTA required by sample, C = (A-B).
Test for Hardness
Sample Volume of sample (ml)
Burette reading Volume of EDTA consumed (ml)
initial Final difference
1 20 0 17 17 172 20 0 1.4 1.4 1.4
Total Hardness as mg/l of CaCo3= (C x D x1000)/Volume of sampleWhere C- volume of EDTA required by sampleD-1 ml of EDT = 1mg of CaCo3 For Sample 1:Total hardness as mg/l as CaCo3= 17 x 1 x1000/20
= 850 mg/lThis is 0.085% of the total volume of the waterFor sample 2:Total hardness as mg/l of CaCo3= 1.4 x 1 x 1000/20
= 70 mg/lThis is 0.007% of the total volume of the water
Chloride Test
1. Take 100 mL of the sample or take appropriate amount and dilute it to100 mL
2. Fill burette with silver nitrate titrant.3. Add 2 to 3 drops of the potassium chromate indicator
to the sample.4. Titrate the blank with standard AgNO3. The end point
is the change of colour from yellow to brick-red (B)5. Titrate the sample in the same way to the same brick-
red color (use blank titration as reference colour and be consistent in end-point recognition.)(A)
6. Calculate ppm Cl- and record with one decimal.
Chloride Test
Parameters Sample 1 Sample 2
Sample Volume (ml) 20 20
Initial Burette reading 0 0
Final burette reading 29.5 1.4
Total Chlorides as mg/l = (A x N AgNO3 x 35450)/Volume of sampleWhere A- ml AgNO3 consumedFor sample 1:Total chlorides = 29.5 X 0.0141 x 35450/20
= 734.77mg/l This is 0.0734% of total volume of the waterFor sample 2:Total chlorides = 1.4 X 0.0141 x 35450/20
= 35mg/lThis is 0.0035% of total volume of the water
Sulphate Test
1. Measure 100 ml water sample or suitable portion of sample made to 100 ml with distilled water
2. Add 5 ml conditioning agent and a spoon full of BaCl2 crystals. Stir exactly for 1 minute
3. Pour the solution in to the glass cell of the turbidity meter and measure the turbidity
4. Prepare a calibration graph by using sulphate standard as described earlier
5. The standards can be made from 0 to 40 mg/l sulphate range by taking 0-40 ml standard solution and making up to 100 ml
6. Determine the concentration of given sample from the calibration chart plotted with known sulphate concentrations Vs turbidity
Sulphate Test
1 2 3 4 5 6 7 8 9 10 110
100200300400500600700
Turbidity vs suplahte concen-tration
Turbidity
Sulphate Concentration (mg/l)
Turb
idit
y (
NTU
)
For sample 1:Turbidity is found to be 490 NTU hence from graph sulphate concentration comes out to be 8.4 mg/l. That is 0.0084% of the total volume of the water.For sample 2:Turbidity is found to be 150 NTU hence from graph sulphate concentration comes out to be 2.5 mg/l. That is 0.0025% of the total volume of the water.
Comparison of Results
Test Before (mg/l) After (mg/l)
Hardness Test 850 70
Chloride Test 734 35
Sulphate Test 8.54 2.5
Computational Analysis
Half of the model is considered for analysis since its symmetric about the y axis
Solar still is modeled in solidworks and then imported into ICEM for meshing
Tetra meshing is done Number of nodes-1788804 Number of elements- 4951096
Computation Analysis
Mesh