3 1. INTRODUCTION Cooling adsorption systems Advantages: 3/271. INTRODUCTIONCooling adsorption systemsAdvantages:● environmentally friendly refrigerants● can recover waste heat at low temperature levels● low operation costsEvaluation of an Adsorption cooling system:● coefficient of performance (COP)● specific cooling power (SCP)Oil crisis (1970)Ecological problems (1990)
4 2. ADSORPTION REFRIGERATOR 4/272. ADSORPTION REFRIGERATOR2.1 System configuration and operationADSORBENTADSORBATEFigure 1. General basis system layout of the adsorption chiller.Adsorbent cooling:adsorption process + refrigerant evaporationAdsorbent heating:desorption process + refrigerant condensation
5 2. ADSORPTION REFRIGERATOR 5/272. ADSORPTION REFRIGERATOR2.1 System configuration and operationFigure 2. Photograph of the silica gel-water adsorption chiller.
6 2. ADSORPTION REFRIGERATOR 6/272. ADSORPTION REFRIGERATOR2.1 System configuration and operationFigure 3. The adsorption icemaker during ice production.Figure 4. Solar-powered icemaker without valves.
7 2. ADSORPTION REFRIGERATOR 7/272. ADSORPTION REFRIGERATOR2.2 Parameters of workParameters that influence in the performance ofthe system:● Temperature of cooling water● Adsorption temperature● Heating source temperature● Desorption temperature● Cycle timeload control toolT↑ and madsorbed ↓ (Pconst)T↑ and P↑ (madsorbed-const)to get more cooling.
8 2. ADSORPTION REFRIGERATOR 8/272. ADSORPTION REFRIGERATOR2.3 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.
9 2. ADSORPTION REFRIGERATOR 9/272. ADSORPTION REFRIGERATOR2.3 Key issues for the development of adsorption systemsThe 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.
10 2. ADSORPTION REFRIGERATOR 10/272. ADSORPTION REFRIGERATOR2.3 Key issues for the development of adsorption systemsThe 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.
11 3. RESEARCHS 3.1 Researches tendency 11/273. RESEARCHS3.1 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.AdsorbentsComponentsSistems
14 3. RESEARCHS 3.1 Researches tendency Simulation constant values: 14/27 ● Overall heat transfer coefficient for adsorbent beds;● Evaporator;● Condenser.
15 3. RESEARCHS 3.1 Researches tendency 15/273. RESEARCHS3.1 Researches tendencyResearches 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.
16 3. RESEARCHS 3.1 Researches tendency 16/273. RESEARCHS3.1 Researches tendencyFigura 5. Design drawing and a frontal view of the adsorption chiler test facility.
17 3. RESEARCHS 3.2 Read Researches 17/273. RESEARCHS3.2 Read ResearchesDevelopment 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.
18 3. RESEARCHS 3.2 Read Researches 18/273. RESEARCHS3.2 Read ResearchesSynthesis 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.
19 3. RESEARCHS 3.2 Read Researches 19/273. RESEARCHS3.2 Read ResearchesTesting 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.
20 3. RESEARCHS 3.2 Read Researches 20/273. RESEARCHS3.2 Read ResearchesDesign 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● refrigerant
21 3. RESEARCHS 3.2 Read Researches Optimization the operation strategy : 21/273. RESEARCHS3.2 Read ResearchesOptimization the operation strategy :● Different temperatures of hot water inlet, cooling water inlet and chilling water inlet → different COP and cooling capacity;● Conventional chiller;● Composite adsorbenthigher cooling capacityCOP slightly higher
22 4 . APLICATIONS ● Jiagsu Province, China 22/274 . APLICATIONS● 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.
24 4 . APLICATIONS ● small power adsorption chillers 24/274 . APLICATIONS● 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
25 25/275 . CONCLUSIONSWe 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.