# New Developments and Progress in Absorption Chillers for Solar Cooling Applications
## 4 Prototypes of Absorption Chillers
### Single-Stage Absorption Chillers
#### 4.1.1 Ammonia-Based Working Pairs
It has also been shown that the use of ammonia/LiNO\({}_{3}\) instead of water/LiBr has advantages for air-cooled absorption chillers. For example, at an ambient air temperature of 41 \({}^{\circ}\)C the ammonia/LiNO\({}_{3}\) absorption chiller can deliver a cooling effect with no risk of the solution crystallizing (64% of its nominal cooling capacity at an ambient temperature of 35 \({}^{\circ}\)C [57]). Compared to the ammonia/water mixture, ammonia/LiNO\({}_{3}\) can be used to design and develop a simplified absorption chiller by avoiding the need for desorbedvapor rectification and reducing the refrigerant charge. Besides, ammonia/LiNO\({}_{3}\) makes it possible to operate the chiller at high heat rejection temperatures and a minimum of 10 \({}^{\circ}\)C below the desorption temperature [57]. Between 2006 and 2011, a laboratory prototype and two pre-industrial small capacity ammonia/LiNO\({}_{3}\) absorption chillers were designed and manufactured with the close collaboration of the CIATESA (Compania Industrial de Aplicaciones Termicas S.A)-CIAT group and the CREVER research group of the URV (Universitat Rovira i Virgili) [57; 58; 59; 48; 51]. The pre-industrial prototypes are air-cooled and water-cooled single-effect absorption chillers. In these prototypes, all the components are made of brazed PHEs. A patented unique distribution device was also used to mix the ammonia vapor and the weak solution at the entry port of the absorber [59]. The schematic diagram of the prototype's cycle configuration is illustrated in Figure 13. The prototype was designed for a nominal cooling capacity of 10 kW at a chilled water supply temperature of 15 \({}^{\circ}\)C for air conditioning applications. The corresponding hot water and cooling water inlet temperatures are 90 \({}^{\circ}\)C and 37.5 \({}^{\circ}\)C in the nominal design conditions. The prototypes were tested under different operating conditions. The air-cooled prototype chiller was experimentally tested at hot water and ambient temperatures of 90 \({}^{\circ}\)C and 35 \({}^{\circ}\)C. The cooling output was \(\sim\)9.3 kW at a chilled water supply temperature of 15 \({}^{\circ}\)C with an electrical COP of about 6.5 for a fan speed of 600 rpm [57]. The chiller is also capable of delivering 64% of its nominal capacity at an ambient air temperature of 41 \({}^{\circ}\)C, which makes it highly applicable in hot climate conditions. According to the test carried out for the water-cooled prototype, an output of \(\sim\)12.9 kW cooling was obtained at a chilled water supply temperature of 15 \({}^{\circ}\)C and an electrical COP of \(\sim\)19.3 [57]. The hot water and cooling inlet temperatures were set to 90 \({}^{\circ}\)C and 35 \({}^{\circ}\)C, respec  
Figure 13: Schematic diagram of the single-effect ammonia/LiNO\({}_{3}\) absorption cycle of the [PERSON] et al. [57] pre-industrial prototype. Adapted from Reference [57]. prototype of the air-cooled ammonia/LiNO\({}_{3}\) absorption chiller manufactured by the company CIATESA is shown in Figure 14.  
The single-effect ammonia/LiNO\({}_{3}\) laboratory prototype was built using Alfa Laval(tm) PHEs, and all its main components were used in a vertical configuration [61]. Both Alfanova 52 and Alfanova 27 were made of stainless steel and were also used in this prototype to avoid corrosion because of ammonia and LiNO\({}_{3}\). The prototype was experimentally tested at hot water and cooling water inlet temperatures between 80 \({}^{\circ}\)C and 95 \({}^{\circ}\)C and 20 \({}^{\circ}\)C and 32 \({}^{\circ}\)C, respectively. In this operating range, the prototype reached a cooling capacity of 3.1 kW at chilled water supply temperatures as low as 6 \({}^{\circ}\)C and a thermal COP of \(\sim\)0.62. Using these PHEs, a compact ammonia/LiNO\({}_{3}\) chiller was developed with an overall prototype volume of approximately 0.7 m\({}^{3}\).