Evaporatively cooled adsorption machine combined with desiccant dehumidifier

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Compressor driven metal hydride cooling system (CDMHC)

The schematic of CDMHC is shown in fig. 1.2. CDMHC is an environmental friendly technology based on the ability of certain metals to absorb and desorb hydrogen (H2). H2 is pumped by a compressor which creates a pressure diffe-rence between two metal reactors. The major disadvantage of this technology is the result of parasitic losses. The COP of CDMHC may approach or exceed that of a VCC by reducing parasitic losses [29]. In CDMHC, the problem of compres-sor overloading during start-up and during sudden load changes is less severe compared to VCC [30]. Park et al. [31] and Mazumdar et al. ([32] [33] [34]) investigated the operating characteristics leading to better performance and co-oling capacity of CDMHC. They found that the properties of metal hydride have a great influence on system performance. Besides, a high metal conductance, a high compressor efficiency, a low compressor pressure ratio and a low mass ratio of slurry to hydrogen lead to a high COP.

Thermoelectric cooler (TEC)

The principle of TEC is based on the Peltier effect where the heat is transferred when an electric current passes across a junction between two materials. The schematic of TEC is shown in fig.1.3. TEC is a clean technology that could be po-wered directly by a PV cell. However, it is very expensive and consumes a large amount of electricity. The COP and the cooling capacity of TEC could be maxi-mized by optimizing the thermal conductance allocation between the hot and the cold side ([35] and [36]) or using an appropriate current ([37] [38] [39]). Moreover, the COP is affected by the temperature difference between the two sides and a multi-stage TEC could be used when a large temperature difference is required.
There are different parameters that influence TEC performance such as the TEC module parameters, the thermal resistances of heat exchangers, the heat sink temperature, the allowable temperature of the cooled object and the ap-plied electric current [35]. According to [37], TEC at transient cooling may reach a lower temperature than that reachable at the steady state, if a current much higher than the steady state optimum current is applied. The contribution of so-lar electricity in a TEC was also studied ([40] and [41]). In [40], the authors observed that the solar insolation has a great effect on the performance of solar driven TEC, and a temperature in the range 5 − 10oC could be maintained in the refrigerator at optimum operating conditions. In [41], the authors tested a TEC connected to P V /T solar panel. A COP greater than 0.45 were achieved. Ho-wever, the system couldn’t achieve a temperature lower than 17oC. The thermal energy gained both from the hot side of TEC and PV/T modules was able to rise the domestic water temperature by about 9oC in 18.5L storage tank.

Vacuum Cooler

A vacuum cooler is a rapid cooling method which is 60 times quicker than conventional air cooling [42]. It is used to remove heat field and, thus, to extend shelf life and improve the quality for many types of horticultural and floricul-tural products. The difference between vacuum cooling and conventional refrigeration methods is that some water from product is directly evaporated in a vacuum chamber. Therefore, only pr ducts containing free water can be vacuum cooled [43]. A Table1simple.layout1 Summaryofvcuumofstudiescoolerconductedisshown inonfigVCC.1.4.

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Absorption cooling system (ABSC)

The ABSC principle is based on the ability of a liquid to absorb and desorb vapor, of another fluid, whose solubility varies with temperature and pressure. It consists mainly of four heat exchangers : a generator, an absorber, an evapo-rator and a condenser as shown in fig.1.5. The refrigerant vapor, resulting from the generator, is cooled down in the condenser at high pressure. The condensed refrigerant is evaporated again at low pressure in the evaporator, thereby extrac-ting heat from the medium to be cooled. Meanwhile, the weak solution (poor in refrigerant) is then sprayed over the top of the absorber where the refrigerant vapor leaving the evaporator is absorbed. The condensing heat in the condenser and the mixing heat in the absorber are rejected to a cooling fluid. LiBr/H2O and H2O/N H3 are the most mixtures used. In a ABSC where volatile absorbent are used such as H2O/N H3, the cycle requires a rectifier to separate the water evaporated from N H3 before entering in the condenser.

Table of contents :

Abstract
Table des figures
Liste des tableaux
General introduction
Introduction générale
1 .Generalities on individual cooling systems 
1.1 Introduction
1.2 Electrically driven cooling system
1.2.1 Vapor Compression Chiller (VCC)
1.2.2 Compressor driven metal hydride cooling system (CDMHC)
1.2.3 Thermoelectric cooler (TEC)
1.2.4 Vacuum Cooler
1.3 Thermally driven cooling system
1.3.1 Absorption cooling system (ABSC)
1.3.2 Adsorption cooling system (ADSC)
1.3.3 Desiccant system (Open sorption system)
1.3.4 Heat-driven metal hydride cooling machine (HDMH)
1.3.5 Steam ejector cooling system or jet compression system (EJC)
1.4 Other cooling system
1.4.1 Evaporative Cooler (Swamp cooler)
1.4.2 Magnetic Refrigerator
1.4.3 Thermoacoustic refrigerator
1.5 Conclusion
2 .Effectiveness Factor of Solar Absorption Cooling System in Representative Locations 
2.1 Introduction
2.2 System description
2.3 Mathematical model
2.3.1 Solar collector model
2.3.2 Generator model
2.3.3 Initial and boundary conditions
2.3.4 Numerical method
2.4 Model validation
2.4.1 Solar collector model validation
2.4.2 Generator model validation
2.5 Results and discussion
2.5.1 Collector area determination
2.5.2 Simulation results
2.6 Effectiveness Factor
2.6.1 Monthly effectiveness factor
2.6.2 Yearly Effectiveness factor
2.7 Conclusion
3 .Hybrid cooling systems : a review and an optimized selection scheme 
3.1 Introduction
3.2 Hybrid systems based on a vapor compression cooling machine
3.2.1 Cascaded absorption- vapor compression cooling system
3.2.2 Adsorption-vapor compression cooling system
3.2.3 Combined desiccant-vapor compression cooling system
3.2.4 Combined ejector-vapor compression cooling system
3.2.5 Combined evaporative-vapor compression cooling system
3.2.6 Combined VCC with desiccant and evaporative systems
3.3 Hybrid systems based on absorption cooling machine
3.3.1 Absorption cooling system with integrated compressor
3.3.2 Desiccant-absorption cooling system
3.3.3 Ejector-absorption cooling system
3.4 Hybrid systems based on adsorption cooling machine
3.4.1 Compressor driven adsorption chiller
3.4.2 Evaporatively cooled adsorption machine combined with desiccant dehumidifier
3.4.3 Ejector-adsorption cooling system
3.4.4 Thermoelectric-adsorption cooling system
3.4.5 Desiccant-evaporative hybrid cooling system
3.5 Multi- evaporator cooling systems
3.6 Discussions
3.7 Conclusions
4 .Hybrid Cooling System : Optimal Sizing 
4.1 Introduction
4.2 System description
4.3 House Description
4.4 Optimal Sizing Method
4.4.1 Mathematical formulation
4.4.2 Case studies
Bibliographie

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