CHEMICAL ENGINEERUniversity of Valladolid

Ana Celina Gondim SantosSara Pérez Nieto

(Group B - 22)

Valladolid, 20 de Octubre de 2011

Chemical Engineering Laboratory II

CHILLING ADSORPTION

1. INTRODUCTION

2. ADSORPTION REFRIGERATOR

3. RESEARCHS

4. APLICATIONS

5. CONCLUSIONS

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1. INTRODUCTION

Cooling adsorption systems

Advantages:

● environmentally friendly refrigerants ● can recover waste heat at low

temperature levels● low operation costs

Evaluation of an Adsorption cooling system:

● coefficient of performance (COP) ● specific cooling power (SCP)

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Oil crisis (1970)Ecological problems (1990)

2. ADSORPTION REFRIGERATOR

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2.1 System configuration and operation

Figure 1. General basis system layout of the adsorption chiller.

ADSORBENT

ADSORBATE

Adsorbent cooling:adsorption process + refrigerant evaporation

Adsorbent heating:desorption process + refrigerant condensation

2. ADSORPTION REFRIGERATOR

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2.1 System configuration and operation

Figure 2. Photograph of the silica gel-water adsorption chiller.

2. ADSORPTION REFRIGERATOR

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2.1 System configuration and operation

Figure 3. The adsorption icemaker during ice production.

Figure 4. Solar-powered icemaker without valves.

2. ADSORPTION REFRIGERATOR

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2.2 Parameters of work

Parameters that influence in the performance of

the system:● Temperature of cooling water● Adsorption temperature● Heating source temperature● Desorption temperature

● Cycle time to get more cooling.

load control toolT↑ and madsorbed ↓ (Pconst)T↑ and P↑ (madsorbed-const)

2. ADSORPTION REFRIGERATOR

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2.3 Key issues for the development of adsorption systems

● The hight cost of production is a drawback for adsorption systems.

● To become more commercially attractive, it is necessary to make a cost and size reduction:

● Increasing the SCP throught enhancement of the internal and external heat transfer of the adsorber;● Increasing the COP throught the improvement of the heat management.

2. ADSORPTION REFRIGERATOR

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2.3 Key issues for the development of adsorption systems

The main technologies to enhance the external heat transfer are related to:

● extended surfaces: to increase of the heat exchange area;● coated adsorbers: to increase the wall heat transfer coefficient;● heat pipe technology: to have a high heat flux

density and less intermediate elements. 

2. ADSORPTION REFRIGERATOR

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2.3 Key issues for the development of adsorption systems

The main technologies to enhance the internal heat transfer are related to:

● consolidated adsorbents: because consolidated adsorbents have lower mass transfer

properties than granular adsorbents, which could lead to very low adsorption rates.

3. RESEARCHS

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3.1 Researches tendency

● Increase in adsorption cooling systems performance → compete with electric compression machines.

● R&D develop performing

● Harmonization of the adsorbent with the thermodynamic cycle.

Adsorbents

Components

Sistems

3. RESEARCHS

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3.1 Researches tendency

Investigation in adsorbing materials:

● silica gel/water● zeolite/water● activated carbon● activated carbon fibres/ammonia● Methanol● R134a

3. RESEARCHS

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3.1 Researches tendency

Adsorption refrigeration systems modelling:

● Many modelling techniques;● Simulate the adsorption refrigeration

systems; ● Simulation techniques:

● lumped-parameter ;● lumped analytical ;● dynamic ;● distributed .

3. RESEARCHS

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3.1 Researches tendency

Simulation constant values:

● Overall heat transfer coefficient for adsorbent beds;

● Evaporator;● Condenser.

3. RESEARCHS

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3.1 Researches tendency

Researches about adsorption cooling:

● evaluation of adsorption and physical-chemical properties of the working-pairs;● development of predictive models of their behaviour in different working conditions.● study of the different kinds of cycles.

Divided into some specifics ways to improve adsorption cooling systems.

3. RESEARCHS

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3.1 Researches tendency

Figura 5. Design drawing and a frontal view of the adsorption chiler test facility.

3. RESEARCHS

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3.2 Read Researches

Development and test of two heat regenerative adsorption systems:

● ice making and air conditioning;

● activated carbon-methanol adsorption pair;

● cycle time was short → good heat transfer.

3. RESEARCHS

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3.2 Read Researches

Synthesis and characterization of a new composite sorbent:

● Improve the adsorbent;● Make the isobars of ads-/desorption steeper; ● Increase the mass of water exchanged at the

same boundary conditions;● Improve the hydrothermal stability.

3. RESEARCHS

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3.2 Read Researches

Testing of the lab scale adsorption chiller:

● Study the influence of the cycle time;● Study the relative duration of the isobaric

steps;● Relative duration of the isobaric steps on the performance of an adsorption

cooling system.

3. RESEARCHS

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3.2 Read Researches

Design and performance prediction of a new generation adsorption chiller:

(Mathematical model)

● Describe the heat and mass transfer process

● Adsorbent bed● the composite adsorbent ● the metal of the tube● the working fluids

● Condenser● cooling water ● the metal of the tube● refrigerant

3. RESEARCHS

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3.2 Read Researches

Optimization the operation strategy :

● Different temperatures of hot water inlet, cooling water inlet and chilling water inlet → different COP and cooling capacity;

● Conventional chiller;

● Composite adsorbent higher cooling capacityCOP slightly higher

4 . APLICATIONS

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● Jiagsu Province, China

● cool a grain depot during hot summers ;● silica-gel adsorption chiller driven by a low

temperature heat source .

● Shanghai Research Institute of Building Science

● chillers being used in the air conditioning system of a “green” building.

4 . APLICATIONS

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Figure 6. (a) Shanghai ‘‘Green’’ Building; (b) equipment room.

(a) (b)

4 . APLICATIONS

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● European project Climasol

● examples of buildings that already use solar-powered sorption air conditioners

● System located in the cosmetic company● adsorption chillers powered by hot water in

the summer

● Chinese policy for energy exploitation ● small power adsorption chillers

● suitable for combined cooling, heating and power systems or heating and power system

5 . CONCLUSIONS

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We tried to synthesize the four articles, taking the best that each had. It was observed that:

•Adsorption cooling systems are becoming increasingly considered for applications where cooling is required and low grade heat is available.•Adsorption refrigerating machines consist essentially of an evaporator, a condenser, valves, and an adsorber-reactor containing a porous medium as adsorbent.•Some parameters influence in the performance of the system and there are drawbacks in these systems that don’t make them so commercially attractive.•Researches about adsorption cooling are divided into some specifics ways to improve adsorption cooling systems.•Looking for real application for the cooling adsorption, some buildings and grain depot were found in Asia and Europe.

Thank you!

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CHEMICAL ENGINEERUniversity of Valladolid

Ana Celina Gondim SantosSara Pérez Nieto

(Group B - 22)

Valladolid, 20 de Octubre de 2011

Chemical Engineering Laboratory II

CHILLING ADSORPTION