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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 ... – PowerPoint PPT presentation

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Title: Adsorption Refrigeration System


1
Adsorption Refrigeration System
2
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.

3
Simple Adsorption cooling system
4
One bed adsorption system by Monma and Mizota in
2005
5
  • Disadvantages of One Bed adsorption system
  • Intermittent cooling effect
  • Low Coefficient of Performance (COP)
  • Long Cycle Time
  • Low Specific Cooling Power (SCP)

6
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.

7
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.

8
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.

9
  • Fig. Internal construction of the adsorption
    chiller.

10
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
11
A Hybrid Solar powered water Heater and
Refrigerator by R.Z. Wang in 2000
12
  • 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.

13
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

14
Fig 1 Rotary thermal regenerative adsorption
device
15
Fig. 2 Section through the generators.
16
  • 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

17
Heat recovery adsorption refrigeration cycles by
R.Z. Wang in 2000
18
  • 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.

19
Solar-Powered Rotary Solid Adsorption
Refrigerator by Aiping Zheng Juan Gu in 2004
20
  • 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.

21
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.

22
  • Thanks
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