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6.2      Design of Condenser

 

The condenser/ evaporator must be designed in such a way that the ammonia vapor, when condensed, can be stored in it. Therefore, the volume of the condenser/evaporator must be at least 2.5 liters, which is the quantity of ammonia required to convert 5 liters of water into ice.

 

The dimensions of the inner tank. Which holds ice, is as follows:

 

Length       =       24.5 cm

Breath       =       25 cm

Height       =        8 cm

 

Considering allowance, the height of tank is 12 cm

 

The volume of the condenser is

 

Vc = p/4 [4d2 b lb + 6 d2c lc  + 16d2v  lv]

 

Where

 

db

=

=

Inside dia. Of the pipe of the bottom frame

f 5.08 cm

dc

=

=

Inside dia. of  the cross pipes

f 1.27 cm

dv 

=

=

Inside dia of the vertical pipes

f 1.27 cm

lc

=

=

Length of each cross pipe

25 cm

Lv

=

=

Length of each vertical pipe

8 cm

 

 

 

Vc   =    p/4 [4 ( 5.08)2 (32) + 6(1.27)2 (25) + 16(1.27)2 (8) ]

      =     2946.5 cm3

      =     2.95 liters

 

Since the volume of the condenser is more than the volume of condensed ammonia required, the design is safe

6.3      Insulation

           Thickness of thermocol   =   45 mm

           (at the top and bottom)

           thickness of glass wool   =   85 mm

           (At the sides)

7.    Details of construction

 

7.1. Flat Plate Collector:

 

(a)    Collector Tubes and Header:

 

        Two G.I tubes, one of which is f 5.08 cm and the other f10.16 cm, and length 112 cm were taken. Twelve holes were drilled on each pipe to accommodate the end of the collector tubes of f1.27 cm. The G.I pipes of f 5.08 cm forms the lower header and that of f 10.16 cm forms the upper  header. These two headers were connected by G.I pipes of f 1.27 cm. The ends of f 1.27 cm pipes were gas-welded with the headers. The upper header was provided with two f 1.27 cm pipes, one for charging of aqua-ammonia solution and the other for carrying ammonia vapour to the condenser. The lower header was provided with one f 1.27 cm pipe for the return line.

 

(b)   Absorber plate:

       The absorber plate was made from a 24-gauge aluminium sheet. The sheet was corrugated so as to accommodate the 12 G>I tubes of 1.27 cm. This was accomplished by carving a semi-circular groove on a wooden block over which the aluminium sheet was placed on the aluminium sheet over the groove . the rod was then hammered along the length until the sheet was corrugated to the required shape . this was done at ten desired positions along the width of the sheet ,the pitch being maintained at 10 cm.

 

Dimensions of the absorber plate

 

Length

=

121.92 cm

Width

=

91.44 cm

Area

=

1.115 m2

      

Holes were punched by the side of the grooves to facilitate the collector plate to be tied to the tubes.

The absorber plate was then placed on to the tubes such that the grooves covered the ten tubes , leaving out one tube at each side to facilitate convection .wires were then passed through the holes and around the tubes and the absorber plate. Black board paint was then applied to the upper surface of the plate.

 

       This type of contact between the absorber plate and the collector tubes ensures a god bond and heat transfer. However, the air gap small it may be, will itself form insulation and hence, decrease in plate efficiency is inevitable. Also, if the bond is good, all the heat is collected by the plate should be transferred to the working medium only through this small contact. This turns out to be a very inefficient method. However, soldered bond is expensive and heating and cooling of the pipes may result in cracks being developed at the joints.

 

(c)   Collector case:

 

       The collector case was made of plywood of size

143.2cm x 120cm x 20.32cm. The bottom was covered with plywood board of size 143.2cm x 120cm. The top was covered with a glass plate and frame, which was hinged to one of the longer sides.

 

       The collector tubes and absorber plate assembly was placed in this case after packing the case with a layer of glass wool of 8cm. Thickness. As mentioned earlier, only 10 pipes were covered with the absorber plate, leaving out one at each side. These two pipes were also insulated with glass wool, so that they do not get heated. This facilitates the convection current to be set up inside the collector tubes, so that the aqua-ammonia solution gets heated and ammonia is liberated.

 

Glass cover with frame:

 

Ordinary window glass of size 110cm x 110cm x 0.3cm was used. This glass cover was placed at a distance of 8cm above the absorber plate.

 

       Shalimar tar-wax was applied to the top edges of the case to form a layer of 0.3cm thickness and 0.6cm width. When the frame rests on the edge, an air tight seal is obtained at the place of contact. It also acts as a cushion to the glass plate.

 

Orientation of the collector:

       The collector assembly was placed with an angle of tilt of 300 and facing south. The collector was turned at an angle of 80 towards west to take advantage of the afternoon sun.

 

 

 

7.2  Condenser

 

The condenser was made from G.I. pipes of f1.27cm, f2.54cm and f 5.08cm.firstly,two square frames of pipes were made, one from f2.24cm pipe and the other from f5.08cm pipe. Each pipe was cut into four pieces of required length at an angle of 450 to the axis of the pipe. The ends were then welded to form a square frame. The lower frame was made from f5.08cm pipe and the upper frame from f2.54cm pipe.

 

The next step was to connect the square frames together. For this, sixteen holes were drilled on each frame and facing each other so as to accommodate the ends of sixteen f1.27cm pipes were gas welded on to the square frames after positioning them properly in the holes.

 

Six G.I pipes of f1.27cm gas-welded to the two opposite pipes of the lower frame, which were provided with the required size holes.

 

Two f1.27cm G.I. pipes were used as the inlet and outlet for ammonia vapour, and were gas-welded on to the top of the frame.

The condenser appeared like a cage after fabrication (ref.fig.7.2.)

7.3 Tank

 

A tank was made from G.I  sheet, such that it fitted inside the condenser. The dimensions of the tank are

 

Length

:

24.5cm

Breath

:

25cm

Height

:

12cm

 

Water, which is to be cooled to form ice, is to be filled only to height of 8cm so that the volume is 5 liters.

 

Stagnant water jacket:

 

If stagnant water is used for cooling the condenser, then large quantity of water is required for efficient condensation. A separate tank has to be provided for this purpose. So, a tank of G.I> sheet was made to the following dimensions.

 

Length

=

43.2cm

Breath

=

43.2cm

Height

=

22.8cm

 

A lid was provided at the top to facilitate the insertion and removal of the inner tank. The top of the tank was covered with thermocol and the sides were insulated by glass wool. The whole set up was enclosed in a box made of hard board of 6mm thickness.

Structures

 

Structures were provided to hold the collector and condenser in place. The condenser was placed at a higher level with respect to the collector to prevent the aqua­–ammonia solution from getting into the condenser.

 

Connecting Pipes

 

The collector and condenser were connected by means of f 1.27 cm G.I. pipes. The outlet from the upper header of collector was connected to the inlet of the condenser via a 1.2m. Rectifying column made from 1.27 cm G.I pipe. The outlet of the condenser was connected to the inlet of the lower header of the collector.

 

Valves

 

Stop values made of cast iron body and steel ball valve inside were provided to regulate the flow of ammonia from the collector to the condenser and back.

8                   Instrumentation

Thermometers were used to measure

a.      The temperature of the absorber plate

b.      The temperature of the condenser

c.      The ambient temperature

8.2 Experimental Procedure

 

The apparatus was made leak proof by applying shellac at the pipe joints. It was then charged with aqua–ammonia solution and the charging valve was closed.

 

The temperature of the absorber plate was measured and recorded and corresponding ambient temperature were noted.

 

During nighttime, refrigeration took place. The temperature of the condenser was noted in the morning the next day. The readings were then tabulated.

RESULTS

 

PERFORMANCE TEST

Date: -------------

 

TIME

PLATE

TEMPERATURE

IN 0C

AMBIENT

TEMPERATURE

IN 0C

SOLARIMETER

READING

IN W/m2

 

 

 

 

10–00 AM

55.0

30.5

900

10–30 AM

62.0

30.5

900

11–00 AM

67.0

31.0

920

11–30 AM

73.0

31.5

940

12–00 AM

76.0

35.0

950

12–30 AM

77.0

36.0

1040

01–00 AM

74.0

35.0

1000

01–30 AM

74.0

33.0

400

02–00 AM

71.0

33.0

940

02–30 AM

52.0

34.0

200

03–00 AM

55.0

35.0

720

03–30 AM

50.0

34.0

700

 

 

At 6.00 pm water was filled in the inner tank of the condenser at 280C.

At 12.30 am the temperature of water was 240C.

At 6.30 am the temperature of water was 200C.

 

 

 

 

9.    Conclusion

This unit can be used in rural areas where electricity is not available. This unit is simple to operate.

The unit was designed to produce ice. However, we were able to get only chilled water.

The coat of the set–up is very high. If solar refrigerators can be made on large scale, the cost of each unit can be effectively reduced and used economically in rural areas.

SUGGESTION FOR IMPROVENT

 

Some improvement have been proposed, but I was not applied due to technical difficulties, shortage of time and non–availability of materials and equipments. These are as follows:

1. Double glazing can be used instead of single glazing, so that the heat loss can be reduced and hence efficiency can be increased.

 

2. Mirrors can be used to concentrate the solar radiation on the absorber plate.

 

3. the air from the set–up must be removed prior to charging.

 

4. A drain valve must be provided between the condenser– evaporator and generator – absorber o drain out the condensed water.

 

5. An array of the plate collectors can be used tp increase the collector area.

10.                      ECONIMIC ANALYSIS

 

COLLECTOR

4” GI pipes 1.1 meters

 

 

2” GI pipes 1.1 meters

 

 

½” GI pipes 20 meters

 

 

Glass plate (1.1 x1.1 meters )

 x0.3 mm thick

 

 

Aluminium sheet(4’ x 3’)

 

 

Black board paint(200 ml)

 

 

Wooden planks

 

 

Labour for wooden box

 

 

Labour and gas welding material

 

 

Paint(green)

 

 

Steel wires,hinges,latches etc.

 

 

Valves (4 in number)1/2” inch

 

 

Cardboard

 

 

Aqua–ammonia solution (10 liters)

 

 

 

CONDENSER

 

 

2” GI pipes 4”6’

 

 

1” GI pipes 4”8’

 

 

½” GI pipes 8”

 

 

Gas welding material and labour

 

 

Thermocol

 

 

GI sheet and labour charge for condenser tank

 

 

Card board condenser box

 

 

Fevicol

 

 

Hinges, latches and screws

 

 

Wooden stripes (1/2” x 1/2")

 

 

Labour for card board box

 

 

Drilling of holes

 

 

 

 

 

 

Structures for collector and condenser

 

 

900 angle plates to collector ( 11 m)

 

 

900 angle plates for ondenser

 

 

¾” ms rod (21 kg)

 

 

2” x ¼” MS flat bar (15 kg)

 

 

 

PROJECT REPORT (-------------)

 

 

 

OTHER CHARGES

 

 

Elbows

 

 

Wooden planks

Painting charges

 

 

Traveling charges

 

 

Miscellaneous

 

 

Arc welding rods

 

 

Synopsis charge

 

 

 

GARND TOTAL:

 

 

 

 

 

 

 

 

 

 

 

11.                      TARGET APPLICATION

 

Artist's rendition of the Sun Frost Vaccine Storage Refrigerator.

 

 

 

 

For vaccine storage and medical uses:

The World Health Organization’s Global Programme for Vaccines and Immunization and its Expanded Programme on Immunization/EPI has approved a number of low voltage DC PV vaccine refrigerators. Solar vaccine refrigerators are designed specifically to meet health needs, and are not appropriate for private use (e.g., refrigerating food and drink).

Technology Availability:

 The WHO has certified a number of models from companies in the world for their GPV/EPI programmes. PV fridges and freezers are generally only available on order from source manufacturers.

Fuel/Energy Availability:

 Most areas in the tropics have sufficient solar energy availability for PV vaccine refrigeration systems. Individual systems may have to be designed based on particular needs of the clinic or health Programme.

Optimum Situation:

Off-grid rural health clinics and hospitals with more than 4 kWh/m2/day solar radiation. Note that there must be sufficient technical infrastructure and manpower in place to service, monitor, and maintain the fridges. In cases where infrastructure is insufficient, consider LPG or kerosene fridges.

REFERENCES

SR NO

 

INDUSTRY

ADDRESS

1

Jade Mountain Inc

http://www.jademountain.com

P.O. Box 4616, Boulder, CO 80306

US

2

Small Power Systems

74550 Dobie Lane
Covelo, CA 95428,US

 

 

 

 

BOOKS

AUTHOR

1

Refrigerator Handbook

Operation and Maintenance Manual, Whirlpool

2

Guide to Insulations

Dupont

3

Solar Energy 5(1),(1961) ; Solar Energy 6(4), (1962)

Prof. J.C.V. Chinnappa 

 

 

 

4

Refrigeration and Air Conditioning

Domkhundwar

 

 

CASE STUDY

AUTHOR

 

 

 

1

Creating a Renewable Energy Future

Keith Lee Kozloff and Roger C. Dower

2

Bringing Power to the People

Daniel M. Kammen

3

Energy Needs in Developing Countries and Sustainability

José Goldemberg

 

 

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