Thermodynamic Analysis of a Solar Combined Ejector Absorption Cooling System

Abstract

The objective of this paper is to investigate theoretically a solar driven 60 kW absorption cooling system. The system is constituted of a combined ejector single-effect absorption cycle coupled with a linear Fresnel solar concentrator and using water/lithium bromide as working fluid. The combined ejector single-effect absorption cycle exhibits high performances, almost equal to that of double-effect absorption device. However, higher driving heat temperatures are required than in the case of conventional single-effect machines. A mathematical model is set up to analyze the optical performance of the linear Fresnel concentrator. Simulations are carried out to study the overall system performance COPsystem and the performances of the combined absorption machine COPcycle for generator driving temperatures and pressures in the ranges 180°C – 210°C and 198 kPa – 270 kPa, respectively. Further, the effect of operating parameters such as the cooling medium and chilled water temperatures is investigated. A maximum cycle performance of 1.03 is found for a generator pressure of 272 kPa and chilled and cooling water temperatures of 7°C and 25°C, respectively. A case study is investigated for a typical summer Tunisian day, from 8:00 to 18:00. The effect of ambient temperature and solar radiation on cycle and system performances is simulated. The optical performances of the concentrator are also analyzed. Simulation results show that between 11:00 and 14:00 the collector efficiency is 0.61 and that the COPcycle reaches values always higher than 0.9 and the COPsystem is larger than 0.55. Globally the performances of the investigated cycle are similar to those of double-effect conventional absorption system.

Investigate the Potential Use of Absorption Chiller for Waste Heat Recovery of Data Centre; Case Study of Earth Ranger Centre

“…Additionally, the optical efficiency of the linear Fresnel collector was between 0.635, under ideal conditions and, 0.663 [28]. The mathematical model for a steady state process was designed based on mass and energy balances for both absorption chiller and ejector [28]. The results from simulation was validated with the results of a research done by Aphornratana et al [29] and was noted that the deviations were less than 1% [28].…”

“…Another research towards solar absorption chillers has been done by Sioud et al [28] on a 60kW LiBr-Water absorption chiller and 164 m 2 linear Fresnel collector. Figure 3-7 demonstrates the combination of linear Fresnel collector and single-effect chiller.…”

“…Figure 3-7 demonstrates the combination of linear Fresnel collector and single-effect chiller. An ejector has been used in the model, which "uses the vapor produced in the generator to entrain and compress the refrigerant vapor coming from evaporator before flowing in the condenser" [28]. Temperature of chilled water was set to be in the range of 4ºC and 12 ºC, which required higher driving source temperatures in the range of 180 ºC and 210 ºC [28].…”

“…An ejector has been used in the model, which "uses the vapor produced in the generator to entrain and compress the refrigerant vapor coming from evaporator before flowing in the condenser" [28]. Temperature of chilled water was set to be in the range of 4ºC and 12 ºC, which required higher driving source temperatures in the range of 180 ºC and 210 ºC [28]. Additionally, the optical efficiency of the linear Fresnel collector was between 0.635, under ideal conditions and, 0.663 [28].…”

“…Temperature of chilled water was set to be in the range of 4ºC and 12 ºC, which required higher driving source temperatures in the range of 180 ºC and 210 ºC [28]. Additionally, the optical efficiency of the linear Fresnel collector was between 0.635, under ideal conditions and, 0.663 [28]. The mathematical model for a steady state process was designed based on mass and energy balances for both absorption chiller and ejector [28].…”