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.
Highlights
In summer, the demand of electrical energy for air-conditioning and refrigeration becomes important, in hot climate zones like the Mediterranean region
The authors concluded that the energetic and economic performance of multieffect absorption machines coupled with concentrating collectors in low direct normal irradiation (DNI) fraction climate zones is poor due to large solar field sizes required and high payback time compared to a single-effect chiller system driven by heat from evacuated tube collector array
Simulations of a 60 kW solar chiller are performed in order to analyze thermodynamically and predict the performances of a combined ejector single-effect absorption refrigeration cycle coupled with linear Fresnel collector modules
Summary
The demand of electrical energy for air-conditioning and refrigeration becomes important, in hot climate zones like the Mediterranean region. The overall energy consumption and costs and the environmental impact become important To reduce these impacts, solar cooling technologies may constitute a promising and attractive solution. Single-effect absorption systems can be activated by flat plate collectors and/or evacuated tube collectors [8, 9] since they require relatively low temperatures of the driving heat sources. The required parabolic collector area was 15m2 and the capacity of hot Journal of Engineering
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