**1. Introduction**

The use of air conditioner and electric fans in buildings around the world is nearly 20% of the total electricity. This consumption has a trend to grow up due to the demographic growth, and more people will naturally want to live in thermal comfort [1]. Solar cooling is a promising and clean alternative equipment which has the advantage for cooling demand in buildings [2]; however, the heat and mass transfer process between the refrigerant and sorption solution and the number of heat exchangers of this kind of equipment (condenser, evaporator, generator, and sorption) reduce the performance of the thermodynamic cycle. The use of new configurations to improve the efficiency of energy has been an important topic of study to reduce the consumption of fossil fuels [1].

The absorption and adsorption cooling system technologies are heat-activated based on the liquid and solid sorption process, respectively. The absorption is based on the absorption and desorption of a working fluid named refrigerant in an absorbent. The absorption cooling system (ACS) consists of four main components: generator, condenser, evaporator, and absorber components as shown in **Figure 1**. The thermodynamic cycle is described as follows: Heat energy is added to the generator to vaporize the refrigerant from the strong solution (high absorbent concentration). The vaporized refrigerant goes to the condenser where it is condensed delivering an amount of heat (QCOOLING). The refrigerant leaving the condenser flows through an expansion valve to reduce the pressure and goes to the evaporator; the refrigerant absorbs the heat of the room (QAIR CONDITIONING) vaporizes producing the cooling effect. Then, the generated vapor goes to the absorber where it is absorbed by the poor solution of the absorbent coming from the generator, delivering heat (QCOOLING), which is dissipated to the ambient to keep the absorption process at a desirable temperature. Finally, the mixture refrigerant-absorbent is pumped to the generator to restart the cycle.

The adsorption system has similar components of the absorption system. However, the cooling effect can be carried out in separate two basic phases (**Figure 2**). In the first phase when the heat is removed (QAIR CONDITIONING) from the chilled water, the refrigerant vapor leaves the evaporator and enters the adsorber, where the refrigerant vapor is adsorbed in the adsorbent bed. The second phase is the desorption process as the result of heating up (QHEATING) the adsorbent bed to release adsorbate (refrigerant) from it. The vapor moves to the condenser, and after throttling liquid refrigerant

#### **Figure 1.**

*Schematic diagram of a single-stage absorption cooling system.*

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**Figure 3.**

*Thermal Analysis of an Absorption and Adsorption Cooling Chillers Using a Modulating…*

Generator temperature, °C 85–180 50–100 Coefficient of performance (COP) 0.6–1.1 0.4–0.6 Working fluid H2O-LiBr or NH3-H2O H2O silica gel

**Absorption system Adsorption system**

flows to the evaporator. The adsorption system has two beds to ensure continuous operation which adsorption and desorption processes occur in the same phase as the

ever, the coefficient of operation is lower than absorption system [3].

*Single-effect solar absorption cooling system with the auxiliary system in TRNSYS.*

The advantages of the adsorption on absorption chiller are the relatively low temperature to separate the refrigerant in the generator as shown in **Table 1**; how-

The TRNSYS [4] software was used to simulate the solar chillers (SC) for cooling a building located in Temixco City, Mexico. **Figure 3** shows the schematic diagram of the process. There are three main circuits: the solar collector (red line), chilled water (blue line), and cooling (green line). In the solar collector circuit, a heating fluid is pumped (Type 3d-3) from a storage tank (Type 4a) into the evacuated solar collector (Type 71) and returned to the tank. This pump is controlled by Type 2b, and it is turned on when the output is higher than the input temperature of the solar collector or when the temperature of the tank does not reach the maximum temperature of operation in the generator of the SC; otherwise, it is turned off. On the other hand, the heating fluid is pumped (Type 3d-4) to the CC (Type 107–2) to supply energy to the generator. When the temperature is lower than the minimum temperature of the working operation of the SC, a heater (Type 6) is turned on.

*DOI: http://dx.doi.org/10.5772/intechopen.84737*

*Typical operation conditions for the sorption systems.*

switching of the chambers [3].

**Table 1.**

**2. Description of the system**

**Figure 2.**

*Adsorption and desorption phases of an adsorption cycle.*

*Thermal Analysis of an Absorption and Adsorption Cooling Chillers Using a Modulating… DOI: http://dx.doi.org/10.5772/intechopen.84737*


**Table 1.**

*Zero and Net Zero Energy*

The absorption and adsorption cooling system technologies are heat-activated based on the liquid and solid sorption process, respectively. The absorption is based on the absorption and desorption of a working fluid named refrigerant in an absorbent. The absorption cooling system (ACS) consists of four main components: generator, condenser, evaporator, and absorber components as shown in **Figure 1**. The thermodynamic cycle is described as follows: Heat energy is added to the generator to vaporize the refrigerant from the strong solution (high absorbent concentration). The vaporized refrigerant goes to the condenser where it is condensed delivering an amount of heat (QCOOLING). The refrigerant leaving the condenser flows through an expansion valve to reduce the pressure and goes to the evaporator; the refrigerant absorbs the heat of the room (QAIR CONDITIONING) vaporizes producing the cooling effect. Then, the generated vapor goes to the absorber where it is absorbed by the poor solution of the absorbent coming from the generator, delivering heat (QCOOLING), which is dissipated to the ambient to keep the absorption process at a desirable temperature. Finally, the mixture refrigerant-absorbent is pumped to the generator to restart the cycle.

The adsorption system has similar components of the absorption system. However, the cooling effect can be carried out in separate two basic phases (**Figure 2**). In the first phase when the heat is removed (QAIR CONDITIONING) from the chilled water, the refrigerant vapor leaves the evaporator and enters the adsorber, where the refrigerant vapor is adsorbed in the adsorbent bed. The second phase is the desorption process as the result of heating up (QHEATING) the adsorbent bed to release adsorbate (refrigerant) from it. The vapor moves to the condenser, and after throttling liquid refrigerant

**88**

**Figure 2.**

**Figure 1.**

*Adsorption and desorption phases of an adsorption cycle.*

*Schematic diagram of a single-stage absorption cooling system.*

*Typical operation conditions for the sorption systems.*

flows to the evaporator. The adsorption system has two beds to ensure continuous operation which adsorption and desorption processes occur in the same phase as the switching of the chambers [3].

The advantages of the adsorption on absorption chiller are the relatively low temperature to separate the refrigerant in the generator as shown in **Table 1**; however, the coefficient of operation is lower than absorption system [3].
