Adsorption Refrigeration System

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Adsorption Refrigeration System
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INTRODUCTION

• Adsorption refrigeration system uses adsorbent
  beds to adsorb and desorb a refrigerant to obtain
  cooling effect.
• Adsorption systems mainly use a natural working
  fluid which have zero ozone depletion potential.
• However, the adsorption cooling machines still
  have some disadvantages that hinder their wide
  application.
• Inventors propose technologies to improve
  adsorption system and make it become a realistic
  alternative.
• An assessment is made about current development
  of adsorption refrigeration technologies.

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Simple Adsorption cooling system
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One bed adsorption system by Monma and Mizota in
2005
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• Disadvantages of One Bed adsorption system
• Intermittent cooling effect
• Low Coefficient of Performance (COP)
• Long Cycle Time
• Low Specific Cooling Power (SCP)

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SILICA GEL/WATER ADSORPTION CHILLER INTEGRATEDIN
SOLAR COOLING SYSTEM by Dr. Uli Jakob in 2008

• Step 1 Desorption Drying of the adsorbent
• The adsorbent is dried by heat input. Water
  vapour is set free, flows in the condenser and is
  liquefied there under heat emission. When the
  material is dry, the heat input in the adsorber
  is stopped and the upper check valve closes.

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SILICA GEL/WATER ADSORPTION CHILLER INTEGRATEDIN
SOLAR COOLING SYSTEM by Dr. Uli Jakob in 2008

• Step 2 Adsorption
• water vapour is adsorbed at the surface of
  the adsorbent. After a cool down phase the
  reverse reaction and the evaporation of the
  liquid refrigerant starts. The lower check valve
  to the evaporator opens and the dry adsorbent
  aspirates water vapour. In the evaporator, water
  evaporates and generates cold.

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SILICA GEL/WATER ADSORPTION CHILLER INTEGRATEDIN
SOLAR COOLING SYSTEM by Dr. Uli Jakob in 2008

• Step 3 Return of condensate
• In a final step, the liquid condensate is
  returned to the evaporator and the circuit is
  closed.

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• Fig. Internal construction of the adsorption
  chiller.

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Technical data ACS 08 Cooling Capacity 7.5
kW Thermal COP 0.56 Electricity Consumption 9
W Chilled Water Circuit 18/15 C at 2.0 m³/h Heat
Rejection Circuit 27/32 C at 3.7 m³/h Heat
Supply Circuit 72/67 C at 1.6 m³/h
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A Hybrid Solar powered water Heater and
Refrigerator by R.Z. Wang in 2000
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• The working principle is just a combination of a
  solar water heater and adsorption refrigeration.
• Heating of the water tank is started in the
  morning through vacuum tube type solar collector.
  With the increasing of the water temperature, the
  temperature in the adsorbent bed rises.
• When the adsorbent temperature rises up
  desorption of the water vapour is get started
  from the bed at constant pressure. The desorbed
  vapor is condensed in the condenser and collected
  in the receiver.
• The liquid flows to the evaporator via an flow
  rate regulating valve.
• A maximum temperature of 80100C could be
  achieved at the end of the process
• hot water in the tank could be drained out and
  moved into another tank thus hot water can be
  used very flexibly.
• With the refilling of the water tank with cold
  water, the temperature of the adsorbent bed is
  reduced rapidly and the pressure in the adsorber
  drops to a value below evaporation pressure .
• Evaporation could happen if the connecting valve
  is open, Refrigeration will continue for the
  whole night until the next morning.

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Rotary thermal regenerative adsorption device by
R.E. Critoph in 2001

• A refrigeration/heat-pump system based on a
  number of simple tubular adsorption modules.
• A single module is comprised of a generator and a
  receiver/condenser/evaporator

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Fig 1 Rotary thermal regenerative adsorption
device
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Fig. 2 Section through the generators.
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• Sixteen modules are shown, arranged in a
  cylindrical shell. All rotate about the central
  axis.
• Air is blown over the tubes, counterflow to their
  direction of motion and exchanging heat with
  them.
• The carbon is at its coldest, perhaps 50ºC and
  has maximum concentration at position 1 in fig 2.
• As it moves clockwise through the annular duct it
  is heated by air flowing in the opposite
  direction.
• The carbon is heated it desorbs ammonia which
  condenses in the receiver section of the module.
  The module reaches the end of the desorption
  section it is perhaps at 200º C.
• A similar process occurs in the adsorbing
  section, but with evaporation occurring in the
  receiver, which cools the airstream passing over
  it.
• All rotate about the central axis typically
  completing one revolution in 10 min

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Heat recovery adsorption refrigeration cycles by
R.Z. Wang in 2000
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• A two beds continuous adsorption refrigeration
  system with heat recovery is shown in Fig. 1
• When adsorber 1 is cooled and connected to the
  evaporator to get adsorption refrigeration in the
  evaporator.
• Adsorber 2 is heated and is connected to the
  condenser to get heatingdesorptioncondensation.
  
• The condensed refrigerant liquid flows into
  evaporator via a flow control valve.
• The operation phase can be changed, and the
  go-between will be a short time heat recovery
  process in which the two pumps drive the thermal
  fluid in the circuit between two adsorbers. (the
  connection to the heater and cooler are blocked
  during this process).
• Heat recovery is important to increase the cycle
  COP.

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Solar-Powered Rotary Solid Adsorption
Refrigerator by Aiping Zheng Juan Gu in 2004
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• The low-pressure refrigerant vapor with low
  temperature from evaporator is introduced to the
  3/5 area of the nether part of the rotary
  adsorbent bed by the gas circulation pump.
• it will be adsorbed by the activated carbon
  fibre, adsorption heat released from the
  adsorbing course will be taken away by the
  refrigerant vapor not adsorbed and then enters
  the solar energy heater.
• The refrigerant vapor will be heated by the solar
  energy heater and its temperature will rise
  gradually, and it will enter the 2/5 area of the
  upper part of the rotary adsorbent bed.
• The refrigerant will desorbed from the activated
  carbon fibre when it is heated by the high
  temperature vapour refrigerant.
• the refrigerant is condensed in the condenser by
  the cooled water.
• After being throttled its pressure is reduced,
  the liquid refrigerant will enters the
  evaporator.
• In the evaporator, the low-pressure refrigerant
  liquid will adsorb the heat from the cooled
  medium, and then it will be gasified into
  refrigerant vapor.
• Then the low-pressure low temperature
  refrigerant vapor will be channeled into the 3/5
  area of the under part of the rotary adsorbing
  bed by the gas pump again and the cycle repeats.

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Conclusion

• For adsorption refrigeration system, significant
  achievements have been obtained on the use of
  various technologies to reduce the complexity of
  system structure, initial cost, to increase the
  system operation reliability as well as energy
  performance.
• However, intensive research is still needed to
• i) enhance the amount of recovered
  thermal energy, without adding complexity into
  the design and operation of system
• ii) optimize the recovered mass rate to
  achieve the best effect.
• Applied material research could produce new
  combined material in order to achieve a higher
  SCP for adsorption refrigeration system.

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• Thanks