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Michael F. Colarossi

Bio: Michael F. Colarossi is an academic researcher from University of Massachusetts Amherst. The author has contributed to research in topics: Thermodynamic equilibrium & Injector. The author has an hindex of 1, co-authored 2 publications receiving 68 citations.

Papers
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TL;DR: In this paper, the authors describe the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach, where the fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed.
Abstract: Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated. The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed. The CFD code is constructed using the open-source OpenFOAM library. Using carbon dioxide as the working fluid, the results of the simulations show a pressure rise that is comparable to experimental data. It is also observed that the flow is near thermodynamic equilibrium in the diffuser, suggesting that turbulence effects present the greatest challenge in modeling these ejectors.

81 citations

12 Jul 2010
TL;DR: In this paper, a two-phase condensing injector is used to produce a more efficient two-loop refrigeration cycle, and the authors present a semi-empirical method based on an Eulerian pseudo-fluid approach using a modified form of the Homogenous Relaxation Model implemented within the framework of OpenFOAM.
Abstract: Widespread research of single phase injectors has led to the development of more efficient refrigeration cycles that utilize the pressure rise induced by injectors without the input of work. The current work presented here focuses on the application of a two-phase condensing injector in a refrigeration cycle to produce a more efficient cycle. A thermodynamic investigation shows the application and limitations of a condensing injector in a two loop refrigeration cycle. The flow through a condensing injector is modeled using semi-empirical method based on an Eulerian pseudo-fluid approach using a modified form of the Homogenous Relaxation Model (HRM) implemented within the framework of OpenFOAM. The predictions are found to be metastable, in that a solution is highly dependent on inlet conditions.

1 citations


Cited by
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TL;DR: In this paper, a comprehensive literature review on ejector refrigeration systems and working fluids is presented, which deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance.
Abstract: The increasing need for thermal comfort has led to a rapid increase in the use of cooling systems and, consequently, electricity demand for air-conditioning systems in buildings. Heat-driven ejector refrigeration systems appear to be a promising alternative to the traditional compressor-based refrigeration technologies for energy consumption reduction. This paper presents a comprehensive literature review on ejector refrigeration systems and working fluids. It deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance and all of the ejector refrigeration technologies, with a focus on past, present and future trends. The review is structured in four parts. In the first part, ejector technology is described. In the second part, a detailed description of the refrigerant properties and their influence over ejector performance is presented. In the third part, a review focused on the main jet refrigeration cycles is proposed, and the ejector refrigeration systems are reported and categorized. Finally, an overview over all ejector technologies, the relationship among the working fluids and the ejector performance, with a focus on past, present and future trends, is presented.

359 citations

Journal ArticleDOI
TL;DR: A review of developments in the use of ejectors for expansion work recovery in vapor-compression systems focusing on the past several years is presented.
Abstract: Previous reviews on ejectors for expansion work recovery have provided detailed discussions of operating characteristics and control of ejector cycles, zero-dimensional ejector modeling, ejector geometry effects, and alternate ejector cycles. However, important advances in the field of ejector technology have occurred since previous reviews were written. Several focuses of recent ejector research are the development of multi-dimensional CFD ejector models, investigation of alternate ejector cycles and uses of the work recovered by the ejector, implementation of effective control strategies for ejector cycles, and application of ejectors in real systems. The objective of this paper is to present a review of developments in the use of ejectors for expansion work recovery in vapor-compression systems focusing on the past several years. Although the first commercial applications are being introduced to the market, it is suggested that future works continue in these areas in order to make ejectors more suitable for additional applications.

212 citations

Journal ArticleDOI
TL;DR: In this paper, a mathematical model of the compressible transonic single and two-phase flow of a real fluid is discussed, in which the specific enthalpy, instead of the temperature, is an independent variable.

111 citations

Journal ArticleDOI
TL;DR: In this paper, the geometry of a CO2 ejector mixing section was optimized using genetic algorithm (GA) and an evolutionary algorithm (EA) with a validated CFD model based on the homogeneous equilibrium model (HEM).

77 citations

Journal ArticleDOI
TL;DR: In this article, a validated CFD tool was used to investigate three cases that were differentiated by the mass flow rate per unit area (mass flux) that passed through the mixer, which represented three dissimilar flow patterns.
Abstract: A CFD-based numerical analysis of the flow irreversibility in R744 ejectors is presented. A validated CFD tool was used to investigate three cases that were differentiated by the mass flow rate per unit area (mass flux) that passed through the mixer, which represented three dissimilar flow patterns. The mixer mass flux was found to significantly affect the ejector performance both locally and globally. An original approach was introduced to assess the contribution of the local irreversibilities to the overall entropy increase. A new factor was proposed to evaluate the ejector performance based on the reference entropy increase in a classic expansion valve. In addition, the influence of the mixer diameter and length on the ejector performance was numerically analysed, which showed that the effects of both geometric parameters may be significant. Namely, in the conditions considered, both enlargement of the mixer cross section area by 17.4% as well as shortening the mixer length by 33.3% resulted in the increase of the overall entropy growth rate by 8.9% and 5.4%, respectively.

75 citations