3. Introduction
The vapor absorption refrigeration system is one of the oldest methods of
producing refrigeration effect.
An ammonia is the commonly used refrigerant in a vapor absorption system.
The absorption system uses heat energy instead of mechanical energy as in
compression systems, in order to change the conditions of the refrigerant.
The absorption system is unique in refrigeration since it involves no moving
parts.
Continuous absorption types of refrigerators have four main sections: the
boiler (generator), the condenser, the evaporator and the absorber.
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4. Introduction cont’d
This system may be used in both the domestic and large industrial refrigerating plants.
The compressor is replaced by an absorber, a generator and a pressure reducing valve.
During the heating process, the vapor refrigerant is driven off by the solution and enters into
the condenser where it is liquefied. The liquid refrigerant then flows into the evaporator and
thus the cycle is completed .
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5. Working principle
The four sections are connected by steel tubes. The entire system is welded together. The
necessary heat for generation is obtained by using either a gas burner, kerosene burner or
electric heating element at the boiler (generator).
The system is charged with ammonia, water and hydrogen. The amount of the combined
solution is at a pressure which will allow the ammonia to condense at room temperature.
When the unit begins operation, some of the ammonia is in a strong solution with water in the
vessel. Heat is applied to the boiler, raising the solution temperature to 177°C (350°F). Some of
the ammonia rises through the vapour pump. The liquid falls back through the boiler and liquid
heat exchanger. It than flows to the vessel, as a weak solution, through the absorber.
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6. Working principle cont’d
After leaving the vapour pump, the ammonia vapour cools down to about 120°C (248°F).
The ammonia gas is mixed with steam and the water is condensed out of the solution in the
rectifier.
The pure ammonia vapour then flows through the condenser, at room temperature. After the
ammonia condenses the liquid falls in the precooled. As the liquid ammonia reaches the
evaporator, the solution begins to evaporate into the hydrogen 18°C (0°F).
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7. Working principle cont’d
The hydrogen ammonia solution then drops back down trough the heat exchanger
and into the vessel to begin another cycle.
It is important to understand that the entire cycle is carried out entirely by gravity flow
of the refrigerant.
It is important that the unit remain in a level, upright position.
It is important that the heat generated in the absorber be removed and that the heat
removed by the condenser be carried away by the surrounding atmosphere.
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8. Thermodynamic Requirement of
Refrigerant –Absorbent Mixture:
Solubility requirement:
The refrigerant should have proper solubility in the absorbent so that a strong solution,
highly rich in the refrigerant, is formed in the absorber by the absorption of the refrigerant
vapor.
Boiling point requirement:
There should be a large difference, about 200oC, in the boiling points of the two substances,
thus absorbent free refrigerant is boiled off from the generator.
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9. Thermodynamic Requirement of
Refrigerant –Absorbent Mixture cont’d
Some other Properties required:
The refrigerant should have high affinity for the absorber at low temp and less affinity at high
temp.
It should have low freezing point.
It should have good thermal and chemical stability
Irreversible chemical reactions of all kinds are to be avoided.
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14. Widely used absorption refrigerators in
Ethiopia
1. Dometic: RCW 42 KE; RCW 50 KE
2. SIBIR: V 170 KE; V 110 KE
3. Zero: PR 265 KE; PR 245 KE
Note: All absorption type refrigerators can operate either
in kerosene or electricity (KE).
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16. For electrical and Kerosene
operation
Refrigerator Heating Element's
wattage
Burner model
RCW 50 KE 120 Watt Aladin 32
SIBIR 175 KE 300 Watt Aladin 23
SIBIR 110 KE 175 Watt Kosmos
ZERO PR 265 KE 320 Watt Aladin 23
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17. Types of Burners
Absorption refrigerators KE, use two types of burner
1. Kosmos burner :- small and yellow flame.
2. Aladdin burner :- big and blue flame.
• Aladdin 32
• Aladdin 23
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21. Installation
Remove accessories from the box and examine to ensure they are complete.
Parts include, filler funnel, brush,burner,wick cleaner,spring,burner reflector and
aluminium partitions.
The device should be cleaned properly before setting it into operation.
Ensure that the device is placed at a cool location, away from heat sources, and
not being exposed to direct sunlight.
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22. Installation cont’d
The room must be ventilated properly.
The device must not be exposed to air draught conditions.
Avoid installing the unit under a ceiling fan.
Never covering the unit with news papers, magazines or other inflammable
materials.
The venting slots at the rear and the top must never be blocked.
To avoid the risk of fire!
The chimney opening can be extremely hot, therefore never covering or
blocking with obstacles.
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24. Installation cont’d
Lower the spacer block at the rear side of the device.
Make sure that, due to the air circulation required, a minimum distance of 10 cm
is provided between the device and any wall located next to the unit.
If the unit is placed near a wooden wall or a cardboard wall, a minimum safety
distance of 50 cm must be realised.
Position the burner reflector on the edge of the spacer support.
To ensure proper function, the unit must be standing horizontally.
Use a water level to check and to correct if necessary.
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25. Installation cont’d
5 VIPs for the installation :
-correct levelling
-no sunlight
-10 cm space around the unit
-no ceiling fan
-no air draught
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26. Installation of separation wall
2 aluminium and 2 water separation walls are included with
the delivery. The use of these separation walls is subject to
the ambient temperature.
Use the water separation wall at ambient
temperatures up to +32°C.
Use the aluminium separation wall at ambient
temperatures higher than +32°C. (up to 43°C at
maximum)
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27. Installation cont’d
The separation walls must be pushed into the slot on the left and right
side of the freezer section.
2 separation walls must be installed. If only one separation wall is
installed, the temperature in the cooling section without an separation
insert will become to cold
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28. Installation cont’d
The blue plastic separation wall must be
filled up to the indicated maximum level
with cold, clean water before starting
operation
Do not fill the separation wall completely!
The upper section must be kept free.
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29. Operating in kerosene
To avoid the risk of fire, use only pure top-grade kerosene. Do not use
Petrol, Diesel or Mixed fuels.
The equipment can be operated using either Kerosene or Electricity.
The device will not function and might be damaged if it is operated with
both energy supplies being selected simultaneously.
Use the funnel provided to fill the tank. To ensure the tank remains free
from dirt, the kerosene should be poured in through a sieve, filter paper
or a clean cloth.
The tank can receive max 5litres of kerosene for 1 week of operation!
Fill the tank up to the “ MAX “ mark.
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30. Operating in kerosene cont’d
Wipe the tank carefully in
case kerosene has been
spilled.
Close the tank using the red
shutter cap and push 3/4 of
the way onto the tank plate.
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31. Operating in kerosene cont’d
Push the spring onto the
burner housing (smaller
diameter facing upwards).
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32. Operating in kerosene cont’d
The wick cleaner is located below
in the burner housing. Keep in a
safe place after removal.
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33. Operating in kerosene cont’d
Position the burner glass
securely on the burner
gallery.
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34. Operating in kerosene cont’d
Detach the burner gallery,
together with burner glass,
by turning anticlockwise.
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35. Operating in kerosene cont’d
Screw the wick out, turn the burner
round and dip the upper end of the
wick into the kerosene for a few
minutes.
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36. Operating in kerosene cont’d
Twist the wick out so that it is
approximately 2 mm over the edge of
the burner.
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37. Operating in kerosene cont’d
Position the burner upright on the tank.
The ends of the wick must reach the bottom of the tank inlet.
Leave the burner in this position for approximately five
minutes to enable the wick to absorb the kerosene from the
tank.
Then light the burner and leave it burning for several minutes
until the wick is burning all around.
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38. Attach the burner gallery, together with the burner
glass, and place clockwise in position.
CAUTION:
the burner is hot.
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39. Operating in kerosene cont’d
Press the burner downwards onto the
spring while carefully pushing the tank
onto the tank plate.
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40. Operating in kerosene cont’d
Release the burner carefully when it is
positioned under the chimney pipe.
Ensure that the burner glass is exactly under
the flange and is closed tightly.
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42. Adjusting the burner flame
cont’d
The optimum adjustment must be set to
achieve maximum performance from the
equipment.
The burner must be burning on a completely
blue flame. (MAX setting) not with small light
tips.
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43. Adjusting the burner flame
cont’d
“Max.” setting “Min.” setting
To adjust the “MAX” setting turn the wick back slowly until the light tips disappear.
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44. Adjusting the burner flame
cont’d
.
The flame must be readjusted after the
burner has been in operation for
approximately 30 minutes and after 1
hour.
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45. Adjusting the burner flame
cont’d
Do not operate the burner on a large yellow flame under any
circumstances.
This causes the flame to give off smoke and the unit to
overheat.
Performance is impaired as a result.
Kerosene consumption also increase considerably.
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46. Adjusting the burner flame
cont’d
A yellow flame always indicates incorrect oxygen supply.
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47. Adjusting the burner flame
cont’d
There can be several main causes:
Burner glass sealing - pervious flange.
Burner glass is resting insecurely on the burner gallery.
Wick is too far out, or burned too low. (soot particles)
Kerosene supply interrupted or insufficient kerosene in the
tank.
Draught. (flickering flame)
Burner installed incorrectly or dirty.
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48. Adjusting the burner flame
cont’d
Check the refrigeration compartment
temperature after approximately 24
hours by using the thermometer.
For the storage of vaccines or
laboratory reagents the temperature
must be between 1 and 8°C .(green
area on the thermometer)
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50. Daily maintenance
Check and note the refrigeration compartment temperature by
using the thermometer.
Check the colour of the flame. The flame must be blue and the
burner must not give off any smoke.
Examine the tank contents.
Check if your vaccines are correctly placed.
Remove any residual liquid from the inner container
immediately.
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51. Weekly maintenance
Check for the ice layer on the evaporator. If the ice layer is thicker than 1cm, the
unit must be defrosted.
Clean the lid gasket and verify that the lid is locking tightly.
Check if the unit is level and stable.
Examine the wick. The top of the wick must be straight and clean. Trim using the
wick cleaner, if necessary.
Examine to ensure the burner is free from soot.
Examine to ensure the end of the wick reaches the bottom of the tank inlet.
Check the burner glass.
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52. Monthly maintenance
Clean the chimney using the brush provided.
Clean the cooling unit. Use a soft brush to free the unit from
dust.
Clean the unit inside and outside.
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53. OPERATION WITH ELECTRICAL
ENERGY
Stop kerosene operation!
The unit will not function and might be damaged if it is operated
with both energy supplies being selected simultaneously.
Refer to the nameplate (rear side of the box) to check whether
the available mains supply corresponds to the required operating
voltage of the unit (220V, 240V or 120V)
The mains cable has to be provided, corresponding to the local
regulations, with an earthen mains plug.
Connect the mains plug to the socket.
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54. OPERATION WITH
ELECTRICAL ENERGY
Turn the electrical thermostat knob clockwise to position “2” (at ambient
temp. 32°C).
Increased setting = increased
cooling capacity.
Use the thermometer to check the temperature
of the cooling section after about 24 hours
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57. Troubleshooting
.
Refrigerator not cold at all
• Device is not placed horizontally.
• Poor ventilation of the box.
• Device is operating with 2 energy sources.
•Cooling unit defective.
Probable couse (both elc and kerosene)
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58. Troubleshooting
Refrigerator not cold at all
With electricity
• wrong operating voltage.
• Heating element wrongly positioned in the
heating tube.
• Wrong thermostat setting.
• Voltage is not constant.
• Electrical thermostat defective ( bad capillary
tube contact at the evaporator).
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59. Troubleshooting
Refrigerator not cold at all
with Kerosene
• Kerosene tank empty.
• Burner dirty.
• Wick dirty
• Chimney dirty and blocked with soot.
• Flame is not burning properly (yellow).
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60. Troubleshooting
Refrigeration insufficient.
Both K & E
• Device is not placed horizontally.
• Poor ventilation of the box.
• Device is operating with 2 energy sources.
• Ambient temperature too high.
• Lid does not lock properly.
• Poor air ventilation within the box.
• Sample have been inserted, before the device had
been cool down.
• Ice layer at the evaporator.
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62. Troubleshooting
Refrigerator to cold.
Both k & E
• Water separation walls are frozen.
• No water in the separation walls.
with electricity
• Wrong thermostat setting.
• Electrical thermostat defective ( bad
capillary tube contact at the evaporator).
with kerosene
• Flame setting too high
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63. Advantage of Absorption
refrigeration
• Silent operation
• Cost effective
• Balanced pressure
• No need of valve
• No lubrication problem
• Less maintenance
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