**2. Description of the system**

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.

**Figure 3.** *Single-effect solar absorption cooling system with the auxiliary system in TRNSYS.*

#### *Zero and Net Zero Energy*

The chilled water circuit is used to control the temperature of the building (type 56) using a cooling thermostat (Type 1503) at 25°C ± 1°C. The chilled water is pumped (Type 3d-1) from the evaporator from the SC to a heat exchanger (Type 91) and exchanges heat with an airflow rate coming from the building (Type 642) and returns to the SC.

The cooling water circuit is used to extract the heat load from the condenser and absorber of the SC. A water flow rate is pumped (Type 3d-5) from the SC, and it is sent to a cooling tower (Type 510) which decreases its temperature, and it is returned to the chiller.

**Figure 4** shows the implementation of the modulating tempering valve (MTV) programmed in Excel (Type62); in this case, the control Type 2b does not turn off

**Figure 4.** *Single-effect solar adsorption cooling system with MTV in TRNSYS.*

**91**

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

**CC TCHW, set Tchilled Tcooling Thot** ABS(°C) 6.7 5.5–10.0 26.6–32.2 108.9–116.1 ADS(°C) 6.7 5.0–12.0 10.0–35.0 65.0–95.0

the pump Type 3d-3 when maximum temperature in the generator is reached but

The MTV consisted of a diverter (Tee1) and a mixer (Tee2) component (**Figure 5**). The objective of the MTV is to keep the input temperature (5) at the maximum range of operation when the storage tank is higher than the limit of operation of CC. The function consists in mixing the high temperature coming from the storage tank (4) with a relative low temperature coming from the chiller (1) changing the flow rates of each stream to keep the maximum temperature (5) at 116°C in the case of absorption system (ABS) and 95°C in the case of adsorption system (ADS) as shown in

The equations presented in this section describe briefly the main components

• Fraction pump power (the energy converted to fluid thermal energy, fpar)

The solar thermal collector efficiency (Type1b) was calculated using a quadratic or linear efficiency equation according to ASHRAE or European standards. The solar collector is an HTP-Evacuated Tube HP-30SC [5] with a net aperture area of

where TIN and TENV are the input temperatures of the solar collector and environment temperature, respectively, and QRAD is the global radiation incident (W/m2

The building (Type 56) is a simple multi-zone building with four windows and only one zone with some dimensions and main building characteristics are shown in **Table 3**. Four occupants in a rest position and three computers turned on from

The Type4a is a stratified storage tank. The properties and working conditions supplied were a heat capacity of 2.24 kJ/kg K for the heating fluid, an initial

(1)

°C).

K. The characteristics of

. The solar thermal collector efficiency is presented in Eq. (1):

used for the simulation; a detailed information could be found in [4].

• The pressure drops and heat losses are negligible into pipelines.

• Thermophysical properties of the fluids are constant.

<sup>η</sup> <sup>=</sup> 0.418 <sup>−</sup> 1.17 (*TIN* <sup>−</sup> *TENV*) \_\_\_\_\_\_\_\_\_ *QRAD*

08:00 to 18:00 were considered as heat generation [6].

temperature of 70°C, and a loss coefficient = 0.75W/m2

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

when storage tank reaches 130°C.

*Operation conditions of the CC.*

**3. Mathematical model of the cooling system**

**Table 2**.

**Table 2.**

**3.1 Assumptions**

was 0.05.

**3.2 Basic equations**

3.86 m2

**Figure 5.** *Connection of the MTV in the solar chiller.*

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


#### **Table 2.**

*Zero and Net Zero Energy*

returns to the SC.

returned to the chiller.

The chilled water circuit is used to control the temperature of the building (type 56) using a cooling thermostat (Type 1503) at 25°C ± 1°C. The chilled water is pumped (Type 3d-1) from the evaporator from the SC to a heat exchanger (Type 91) and exchanges heat with an airflow rate coming from the building (Type 642) and

The cooling water circuit is used to extract the heat load from the condenser and absorber of the SC. A water flow rate is pumped (Type 3d-5) from the SC, and it is sent to a cooling tower (Type 510) which decreases its temperature, and it is

**Figure 4** shows the implementation of the modulating tempering valve (MTV) programmed in Excel (Type62); in this case, the control Type 2b does not turn off

**90**

**Figure 5.**

**Figure 4.**

*Connection of the MTV in the solar chiller.*

*Single-effect solar adsorption cooling system with MTV in TRNSYS.*

*Operation conditions of the CC.*

the pump Type 3d-3 when maximum temperature in the generator is reached but when storage tank reaches 130°C.

The MTV consisted of a diverter (Tee1) and a mixer (Tee2) component (**Figure 5**). The objective of the MTV is to keep the input temperature (5) at the maximum range of operation when the storage tank is higher than the limit of operation of CC. The function consists in mixing the high temperature coming from the storage tank (4) with a relative low temperature coming from the chiller (1) changing the flow rates of each stream to keep the maximum temperature (5) at 116°C in the case of absorption system (ABS) and 95°C in the case of adsorption system (ADS) as shown in **Table 2**.
