Waste Heat Driven Multi-Ejector Cooling Systems: Optimization of Design at Partial Load; Seasonal Performance and Cost Evaluation

Abstract

In this paper, a seasonal performance analysis of a hybrid ejector cooling system is carried-out, by considering a multi-ejector pack as expansion device. A 20 kW ejector-based chiller was sized to obtain the optimal tradeoff between performance and investment costs. The seasonal performance of the proposed solution was then evaluated through a dynamic simulation able to obtain the performance of the designed chiller with variable ambient temperatures for three different reference climates. The optimized multi-ejector system required three or four ejectors for any reference climate and was able to enhance the system performance at partial load, with a significant increase (up to 107%) of the seasonal energy efficiency ratio. The proposed system was then compared to conventional cooling technologies supplied by electric energy (electrical chillers EHP) or low-grade heat sources (absorption chillers AHP) by considering the total costs for a lifetime of 20 years and electric energy-specific costs for domestic applications from 0.10 to 0.50 €/kWhel. The optimized multi-ejector cooling system presented a significant convenience with respect to both conventional technologies. For warmer climates and with high electricity costs, the minimum lifetime for the multi-ejector system to achieve the economic break-even point could be as low as 1.9 years.

Waste heat recovery of industrial exhaust gas : study of variable power ejector cooling systems

“…The technology has since been applied in large and medium scale systems. In the case of single-phase vapor ejectors, several works proposed the use of a multiple ejector setup where each ejector is designed to operate at a specific outlet pressure, allowing the ejector setup to operate over a wide range of outlet pressure by switching from one ejector to the other [13][14][15][16][17][18]. Thus, in all these works, there was always only one ejector in operation at the same time.…”

Effect of Back Pressure on Performances and Key Geometries of the Second Stage in a Highly Coupled Two-Stage Ejector

“…Wang et al [ 27 ] developed a CFD model to investigate the performance of a proposed two-stage ejector. Viscito et al [ 28 ] proposed a seasonal performance analysis of a hybrid ejector cooling system, they claimed that system required three or four ejectors for any reference climate, and they obtained an increase of the seasonal energy efficiency ratio up to 107%. Lillo et al [ 29 ] presented a thermo-economic analysis of a waste heat recovery hybrid ejector cycle with a cooling load of 20 kW, the thermo-economic performance of this cycle has evident advantages over other waste heat driven system.…”