Thermo-Economic Analysis of a Hybrid Ejector Refrigerating System Based on a Low Grade Heat Source

Abstract

The rising of the global energy demand requires the use of alternative energy conversion systems employing renewable sources. In the refrigeration and air conditioning fields, heat driven ejector systems represent a promising way to produce the cooling effect by using available low-grade temperature sources. In this paper, a thermo-economic analysis of a waste heat recovery hybrid ejector cycle (WHRHEC) was carried out. A thermodynamic model was firstly developed to simulate a WHRHEC able to obtain chilled water with a cooling load of 20 kW, by varying the working fluids and the pinch point values in the heat exchangers. Specific single- and two-phase heat transfer correlations were used to estimate the heat transfer surface and therefore the investment costs. The operative ranges that provide a reasonable compromise between the set-up costs and the cycle performances were then defined and compared to the current waste heat-driven technologies, such as absorption chillers and organic Rankine cycles (ORCs) coupled with vapor compression cycles (VCCs). The last part of the paper presents an economic analysis providing the map of the design (plant size) and contingent (specific cost of energy, waste heat availability) variables that lead to the economic convenience of a WHRHEC system when integrated to a conventional VCC plant.

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

“…There are many analysis and evaluation methods currently used to measure the energy consumption of heat exchangers and guide their optimal design [19]. They can be divided into the following three categories: first, the analysis and evaluation based on the first law of thermodynamics [20]; second, the evaluation combining the conservation of energy and the second law of thermodynamics [21]; finally, the above methods are improved and derived, including thermoeconomics [22], composition method [23], the theory of fire accumulation dissipation [24], etc. Sun et al [25] studied a shell-and-tube heat exchanger with inclined three-lobed baffles, numerically simulated its flow and heat transfer characteristics, and analyzed the structure using heat transfer coefficients and pressure drops.…”

Thermodynamic Performance Investigation of a Small-Scale Solar Compression-Assisted Multi-Ejector Indoor Air Conditioning System for Hot Climate Conditions

“…These refrigerants are suitable to operate at typical generation, evaporation, and condensation conditions for ejector-assisted air conditioning cycles [30]. Hydrochlorofluorocarbon (HFC) R245fa and hydrocarbon (HC) R600a, which have zero ozone depletion potential (ODP) and relatively low to moderate global warming potential (GWP), are the primary candidates, while R11 and R141b, which have been widely used in both actual air conditioning systems and experimental and numerical ejector refrigeration studies [31], thereby providing performance and model validation data (e.g., [20,21,32,33]), serve as a benchmark. Due to their low or zero ODP, HCFs, including R245fa, have served as transition working fluids to replace CFCs and HCFCs [16,34].…”

“…Certain nations may not be prepared for compliance due to a lack of commitment, financial means, or knowledge [34]. While R600a may be considered the preferred working fluid based on the ODP and GWP criteria in this study, it is classified as highly flammable, which has raised safety concerns for residential air conditioning applications [20,31,41,42]. In addition, although new HFOs with near-zero or zero ODP and GWP appear to be, overall, less flammable than hydrocarbons [43], they are currently up to eight times more expensive than HFCs [41] and, consequently, may not be affordable in certain developing economies with a high demand of air conditioning in hot climates.…”

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

“…A schematic layout of the hybrid ejector cycle is shown in Figure 2a, and the thermodynamic cycle on the T-s diagram of the hybrid ejector cycle is shown in Figure 2b. The description of the thermodynamic cycle can be found in our previous open-access work [11].…”

“…Lillo et al [11] proposed a comparison, using a thermo-economic analysis, between a hybrid ejector cooling system and conventional heat-driven cooling technologies such as absorption and combined ORC/VCC plants. Several working fluids including HFCs, HFOs, hydrocarbons and ammonia were investigated, and ammonia solutions were found to be the most efficient and less expensive options.…”