Abstract
The field of computational fluid dynamics has been rekindled by recent researchers to unleash this powerful tool to predict the ejector design, as well as to analyse and improve its performance. In this paper, CFD simulation was conducted to model a 2-D axisymmetric supersonic ejector using NIST real gas model integrated in ANSYS Fluent to probe the physical insight and consistent with accurate solutions. HFOs (1234ze(E) and 1234yf) were used as working fluids for their promising alternatives, low global warming potential (GWP), and adhering to EU Council regulations. The impact of different operating conditions, performance maps, and the Pareto frontier performance approach were investigated. The expansion ratio of both refrigerants has been accomplished in linear relationship using their critical compression ratio within ±0.30% accuracy. The results show that R1234yf achieved reasonably better overall performance than R1234ze(E). Generally, by increasing the primary flow inlet saturation temperature and pressure, the entrainment ratio will be lower, and this allows for a higher critical operating back pressure. Moreover, it was found out that increasing the degree of superheat for inlet primary flow by 25 K improved the entrainment ratio by almost 20.70% for R1234yf. Conversely, increasing the degree of superheat to the inlet secondary flow has a relativity negative impact on the performance. The maximum overall ejector efficiency reached was 0.372 and 0.364 for R1234yf and R1234ze(E) respectively. Comparing the results using ideal gas model, the ejector entrainment ratio was overestimated up to 50.26% for R1234yf and 25.66% for R1234ze(E) higher than using real gas model.
Highlights
Refrigeration is identified as an indispensable method that is widely used in many applications, including food storage, providing thermal comfort, and in the health care industry to preserve pharmaceuticals and medicines
The comprehensive computational fluid dynamics (CFD) simulation was performed based on the NIST real gas model in order to increase the accuracy and consistency of the results, and this was used to model and design 2-D
This paper is mainly devoted to computational fluid dynamics simulation conducted for a 2D
Summary
Refrigeration is identified as an indispensable method that is widely used in many applications, including food storage, providing thermal comfort, and in the health care industry to preserve pharmaceuticals and medicines. The conventional vapor-compression refrigeration systems are mainly driven by electricity and are usually characterized by high energy consumption [1]. ERS come with advantages such as simple mode of function, lack of moving parts in construction, low cost, long lifespan, in addition to simplicity of installation and maintenance This refrigeration system utilizes an ejector, generator and a liquid pump in place of the compressor which is electricity driven [3]. The advantages of using ERS have resulted in many researchers trying to exploit different techniques to enhance ejector performance An example of such technique is the computational fluid dynamics (CFD). The work from Mohamed et al [12] was pertinent to this paper based on the CFD design of the ejector under real gas modelling in spite despite the use of a different solver and turbulent model
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