Centrifugal Compressor Working Fluids for Refrigeration Cycle

2009 ◽  
Author(s):  
Pekka Ro¨ytta¨ ◽  
Juha Honkatukia ◽  
Teemu Turunen-Saaresti
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Working Fluid ◽  
Accurate Estimation ◽  
Cooling Power ◽  
Condensation Temperature ◽  
Refrigeration Cycle ◽  
Light Weight ◽  
Centrifugal Compressors ◽  
Working Fluids

A centrifugal high-speed compressor is an effective light weight option to power a refrigeration cycle for air conditioning purposes. Perhaps the most important decision in design is the working fluid selection. Modern high-speed technology makes it possible for the refrigeration compressor to be completely oil free, which considerably broadens the scale of possible working fluids. Furthermore, many traditional fluids have become banned and the industry standard R134a might face the same faith in some European countries because of its relatively high global warming potential. In this study eleven different fluids were studied and compared and R22 was used as a reference. It was found that there are many potential fluids for centrifugal compressors that provide better efficiencies than the most common fluids in use today. The purpose of this study is to initially screen a larger set of candidate fluids for more accurate estimation later on. The fluids are evaluated by the efficiency of the cycle, but also mechanical feasibility and dimensions are considered as light weight of the machinery was an important criterion in design process. The comparison was made with constant evaporation and condensation temperature and fixed cooling power for all the fluids. In selection of the working fluid the safety factors often play a dominant role which was also shortly considered. In our study we found out that for a residential HVAC size cooling cycle there are environmentally friendly fluids with high efficiency leading to feasible mechanical designs with centrifugal compressors.

Performance Investigation of Solar Organic Rankine Cycle Systems With and Without Regeneration and With Zeotropic Working Fluid Mixtures for Use in Micro-Cogeneration

2020 ◽  
Author(s):  
Wahiba Yaïci ◽  
Evgueniy Entchev ◽  
Pouyan Talebizadeh Sardari
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
High Efficiency ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Industrial Wastes ◽  
Working Fluid ◽  
Condensation Temperature ◽  
Thermodynamic Performance ◽  
Cycle Efficiency

Abstract Globally there are several viable sources of renewable, low-temperature heat (below 130°C) particularly solar energy, geothermal energy, and energy generated from industrial wastes. Increased exploitation of these low-temperature options has the definite potential of reducing fossil fuel consumption with its attendant very harmful greenhouse gas emissions. Researchers have universally identified the organic Rankine cycle (ORC) as a practicable and promising system to generate electrical power from renewable sources based on its beneficial use of volatile organic fluids as working fluids (WFs). In recent times, researchers have also shown a preference for/an inclination towards deployment of zeotropic mixtures as ORC WFs because of their capacity to improve thermodynamic performance of ORC systems, a feat enabled by better matches of the temperature profiles of the WF and the heat source/sink. This paper demonstrates both the technical feasibility and the notable advantages of using zeotropic mixtures as WFs through a simulation study of an ORC system. The study examines the thermodynamic performance of ORC systems using zeotropic WF mixtures to generate electricity driven by low-temperature solar heat source for building applications. A thermodynamic model is developed with an ORC system both with and excluding a regenerator. Five zeotropic mixtures with varying compositions of R245fa/propane, R245fa/hexane, R245fa/heptane, pentane/hexane and isopentane/hexane are evaluated and compared to identify the best combinations of WF mixtures that can yield high efficiency in their system cycles. The study also investigates the effects of the volumetric flow ratio, and evaporation and condensation temperature glides on the ORC’s thermodynamic performance. Following a detailed analysis of each mixture, R245fa/propane is selected for parametric study to examine the effects of operating parameters on the system’s efficiency and sustainability index. For zeotropic mixtures, results showed that there is an optimal composition range within which binary mixtures are inclined to perform more efficiently than the component pure fluids. In addition, a significant increase in cycle efficiency can be achieved with a regenerative ORC, with cycle efficiency ranging between 3.1–9.8% and 8.6–17.4% for ORC both without and with regeneration, respectively. Results also showed that exploiting zeotropic mixtures could enlarge the limitation experienced in selecting WFs for low-temperature solar organic Rankine cycles.

Improvement of Rotordynamic Performance of Integrally Geared Centrifugal Compressors Through a Systematic Design Modification Approach

2019 ◽  
Author(s):  
Zhusan Luo ◽  
Carl Schwarz
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
High Reliability ◽  
Air Separation ◽  
Centrifugal Compressors ◽  
Design Modification ◽  
Design Variables ◽  
Short Period ◽  
Key Indicators ◽  
Bearing System

Abstract Integrally geared centrifugal compressors have found wide applications in air separation plants and the petrochemical industry because they can be readily designed to run at a higher efficiency than in-line compressors. Many of these compressors with multiple stages are designed to meet the demands for high power and high speed applications with high efficiency and high reliability. These requirements are challenges for their rotordynamic designs. Some compressors may experience excessive synchronous or subsynchronous vibrations during commissioning or in a short period of service. This study starts with discussing the vibration characteristics of a compressor pinion-bearing system, including undamped critical speeds, unbalance responses, and rotordynamic stability. To improve the rotordynamic performance, a systematic and feasible approach for modifying a rotordynamic design has been proposed. It has been showed that damped modes at an operating speed are key indicators of the rotordynamic performance. The sensitivities of damped modes to main design variables, i.e. bearing geometry, shaft geometry and impeller mass properties, are thoroughly examined. A procedure for design modification is proposed for general guidance. The feasibility and effectiveness of this method have been demonstrated in the modification of a pinion-bearing system. In addition, this paper also proposes a method to evaluate the torsional natural frequencies of an equivalent pinion model and briefly discusses the application of optimal design methodology to the rotordynamic design modification.

Siloxanes as Working Fluids for Mini-ORC Systems Based on High-Speed Turbogenerator Technology

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti ◽  
Juha Honkatukia ◽  
Piero Colonna ◽  
Jaakko Larjola
Keyword(s):  
Molecular Weight ◽  
Power Output ◽  
High Speed ◽  
Thermodynamic Cycle ◽  
Turbine Rotor ◽  
Working Fluid ◽  
Specific Enthalpy ◽  
Working Fluids ◽  
Simulated Performance ◽  
Component Design

This paper presents a study aimed at evaluating the use of siloxanes as the working fluid of a small-capacity (≈10kWe) ORC turbogenerator based on the “high-speed technology” concept, combining the turbine, the pump, and the electrical generator on one shaft, whereby the whole assembly is hermetically sealed, and the bearings are lubricated by the working fluid. The effects of adopting different siloxane working fluids on the thermodynamic cycle configuration, power output, and on the turbine and component design are studied by means of simulations. Toluene is included into the analysis as a reference fluid in order to make comparisons between siloxanes and a suitable low molecular weight hydrocarbon. The most influential working fluid parameters are the critical temperature and pressure, molecular complexity and weight, and, related to them, the condensation pressure, density and specific enthalpy over the expansion, which affect the optimal design of the turbine. The fluid thermal stability is also extremely relevant in the considered applications. Exhaust gas heat recovery from a 120 kW diesel engine is considered in this study. The highest power output, 13.1 kW, is achieved with toluene as the working fluid, while, among siloxanes, D4 provides the best simulated performance, namely 10.9 kW. The high molecular weight of siloxanes is beneficial in low power capacity applications, because it leads to larger turbines with larger blade heights at the turbine rotor outlet, and lower rotational speed if compares, for instance, to toluene.

Computational Fluid Dynamics of a Radial Compressor Operating With Supercritical CO2

2012 ◽  
Author(s):  
Rene Pecnik ◽  
Enrico Rinaldi ◽  
Piero Colonna
Keyword(s):  
Critical Point ◽  
Gas Turbine ◽  
Supercritical Co2 ◽  
High Speed ◽  
Power Plants ◽  
Compressible Flows ◽  
High Efficiency ◽  
Fluid Dynamic ◽  
Working Fluid ◽  
Maximum Pressure

The merit of using supercritical CO2 (scCO2) as the working fluid of a closed Brayton cycle gas turbine is now widely recognized, and the development of this technology is now actively pursued. scCO2 gas turbine power plants are an attractive option for solar, geothermal and nuclear energy conversion. Among the challenges which must be overcome in order to successfully bring the technology to the market, the efficiency of the compressor and turbine operating with the supercritical fluid should be increased as much as possible. High efficiency can be reached by means of sophisticated aerodynamic design, which, compared to other overall efficiency improvements, like cycle maximum pressure and temperature increase, or increase of recuperator effectiveness, does not require an increase in equipment cost, but only an additional effort in research and development. This paper reports a three-dimensional CFD study of a high-speed centrifugal compressor operating with CO2 in the thermodynamic region slightly above the vapor-liquid critical point. The investigated geometry is the compressor impeller tested in the Sandia scCO2 compression loop facility [1]. The fluid dynamic simulations are performed with a fully implicit parallel Reynolds-averaged Navier-Stokes code based on a finite volume formulation on arbitrary polyhedral mesh elements. The CFD code has been validated on test cases which are relevant for this study, see Ref. [2,3]. In order to account for the strongly nonlinear variation of the thermophysical properties of supercritical CO2, the CFD code is coupled with an extensive library for the computation of properties of fluids and mixtures [4]. Among the available models, the one based on reference equations of state for CO2 [5,6] has been selected, as implemented in one of the sub-libraries [7]. A specialized look-up table approach and a meshing technique suited for turbomachinery geometries are also among the novelties introduced in the developed methodology. A detailed evaluation of the CFD results highlights the challenges of numerical studies aimed at the simulation of technically relevant compressible flows occurring close to the liquid-vapor critical point. The data of the obtained flow field are used for a comparison with experiments performed at the Sandia scCO2 compression-loop facility.

scholarly journals Thermodynamic Analysis of a Rankine Cycle Powered Vapor Compression Ice Maker Using Solar Energy

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Bing Hu ◽  
Xianbiao Bu ◽  
Weibin Ma
Keyword(s):  
Solar Energy ◽  
System Performance ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Cooling Power ◽  
Condensation Temperature ◽  
Vapor Compression ◽  
Maximum Value ◽  
Ice Production

To develop the organic Rankine-vapor compression ice maker driven by solar energy, a thermodynamic model was developed and the effects of generation temperature, condensation temperature, and working fluid types on the system performance were analyzed. The results show that the cooling power per square meter collector and ice production per square meter collector per day depend largely on generation temperature and condensation temperature and they increase firstly and then decrease with increasing generation temperature. For every working fluid there is an optimal generation temperature at which organic Rankine efficiency achieves the maximum value. The cooling power per square meter collector and ice production per square meter collector per day are, respectively, 126.44 W m−2and 7.61 kg m−2 day−1at the generation temperature of 140°C for working fluid of R245fa, which demonstrates the feasibility of organic Rankine cycle powered vapor compression ice maker.

scholarly journals Experimental and numerical investigation of blade resonance in a centrifugal compressor for varying gas properties

2018 ◽  
Vol 2 ◽  
pp. Q15CRP
Author(s):  
Degendorfer Carsten ◽  
Reza S. Abhari ◽  
Klemens Vogel ◽  
René Hunziker
Keyword(s):  
Unsteady Flow ◽  
Damping Ratio ◽  
Dynamic Strain ◽  
Working Fluid ◽  
Centrifugal Compressors ◽  
Resonance Amplitude ◽  
Working Fluids ◽  
Flow Simulations ◽  
Modal Response ◽  
Wide Range

The blades of centrifugal compressors are exposed to unsteady forces during operation which can result in resonance response conditions and failures due to high cycle fatigue. A typical source of excitation is the unsteady fluid structure interaction between the impeller blades and the downstream vaned diffuser. Centrifugal compressors are operated with various working fluids with a wide range of applications in the power and process industry. Understanding the excitation mechanisms for different working fluids will help to design aerodynamically efficient compressors, while ensuring mechanical integrity and reducing the number of experimental design validations. A variation in working fluid properties allows investigation of the contribution of blade forcing and damping while the modal response remains unchanged. Experiments have been conducted at ETH Zurich’s radial compressor facility with a state of the art industrial compressor design. Dynamic strain gauge measurements on the impeller blades were used to determine the amplitude response, damping properties and forcing at a defined resonance condition. Two working fluids have been investigated to vary compressor flow settings while the modal response remains unchanged. Unsteady flow simulations and harmonic FSI simulations were used to complement the experiments and to investigate the local blade forcing distribution, which then were linked to flow effects. Experiments showed a change in resonance amplitude up to a factor of 4 due to a change in the applied working fluid. Estimation of the damping ratio with a single degree of freedom model found the exciting force to be the main contributor to the differences in resonant response. The unsteady flow simulations were able to identify the locations on the blade surface which are responsible for the change in forcing. It was found that the forcing depends on wave propagation effects in the flow channel and on how the pressure field matches the mode shape.

scholarly journals Influence of metal working fluid on chip formation and mechanical loads in orthogonal cutting

2021 ◽  
Author(s):  
Berend Denkena ◽  
Alexander Krödel ◽  
Lars Ellersiek
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Orthogonal Cutting ◽  
Machining Process ◽  
Working Fluid ◽  
Rake Face ◽  
Metal Working ◽  
Mechanical Loads ◽  
Working Fluids ◽  
Process Forces

AbstractMetal working fluids are used in machining processes of many hard-to-cut materials to increase tool life and productivity. Thereby, the metal working fluids act on the thermal and on the mechanical loads of the tool. The changing mechanical loads can mostly be attributed to the changing friction between rake face and chip and changes in the chip formation, e.g., the contact length between rake face and chip. However, analyzing those effects is challenging, since a detailed look at the chip formation process is prevented by the metal working fluid. In this paper, a novel planing test rig is presented, which enables high-speed recordings of the machining process and process force measurements while using metal working fluids. Experiments reveal that process forces are reduced with increasing pressure of the metal working fluid. However, the average friction coefficient only changes slightly, which indicates that the reduced process forces are mainly the result of reduced contact lengths between rake face and chip.

Modeling and Computer Simulation of Centrifugal CO2 Compressors at Supercritical Pressures

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Farhad Behafarid ◽  
Michael Z. Podowski
Keyword(s):  
Incompressible Flow ◽  
High Speed ◽  
High Efficiency ◽  
Three Dimensional ◽  
Ideal Gas ◽  
Working Fluid ◽  
Technical Data ◽  
Flow Models ◽  
Energy Conversion Systems ◽  
Co2 Flow

The use of supercritical carbon dioxide (SC-CO2) as a working fluid in energy conversion systems has many benefits, including high efficiency, compact turbomachinery, and the abundance of CO2. A very important issue for design optimization and performance analysis of future SC Brayton cycles is concerned with the SC-CO2 flow inside high-speed compressors and turbines. The objective of this paper is to present a novel modeling approach to, and its use in numerical simulations of, SC-CO2 flow inside a high-speed compact compressor. The proposed approach capitalizes on using three different physical and mathematical formulations of one-dimensional (1D) models, i.e., compressible and incompressible flow models using actual properties of SC-CO2 and a compressible ideal gas model, as a reference to verify the predictive capabilities of a three-dimensional (3D) incompressible flow model. The incompressible model has been used to perform simulations for a complete detailed multidimensional model of an SC-CO2 high-speed compact compressor. The advantages of the new model include numerical stability, computational efficiency, and physical accuracy. In particular, it has been shown that the model's predictions are consistent with selected published technical data.

Lapping Machining of High-Speed and High-Precision Ceramic Bearing Balls

2005 ◽  
Vol 291-292 ◽  
pp. 325-330 ◽  
Author(s):  
Yu Hou Wu ◽  
Song Hua Li ◽  
Ke Zhang
Keyword(s):  
High Precision ◽  
High Speed ◽  
High Efficiency ◽  
Research Result ◽  
High Hardness ◽  
Light Weight ◽  
Abrasive Resistance ◽  
Ceramic Bearing ◽  
Mechanics Characteristic ◽  
Heat Expansion

In resent years, ceramic balls have been applied into precision bearings and other parts far and wide because of its advantages in light weight, high hardness, abrasive resistance, high-temperature resistance, corrosion resistance, little heat expansion coefficient and so on. The high-precision ceramic balls are machined by lapping usually, and the method of lapping has an important influence on the machining precision and efficiency of ceramic balls. In order to improve the precision and efficiency of ceramic ball machining, in the paper, a new cone lapping method is researched by the lapping experiment. The research result shows that the cone method is the optimal lapping method with high precision, high efficiency and the very simple machine. Furthermore, the mechanics characteristic of the cone lapping method have been analyzed and summarized, which will provide the basic principle and theoretical basis for the choice of primary geometry and mechanics parameter in the process of ceramic balls lapping.

Multivariate Analysis of Orthogonal Tube Cutting Forces With 3-D Tool Wear Analysis of AISI 1020 Alloy Steel Using Cold Compressed Air Versus Liquid Nitrogen as Metal Working Fluids

2015 ◽  
Author(s):  
Vishnu Vardhan Chandrasekaran ◽  
Lewis N. Payton ◽  
Wesley S. Hunko
Keyword(s):  
Multivariate Analysis ◽  
Liquid Nitrogen ◽  
High Speed ◽  
High Speed Steel ◽  
Compressed Air ◽  
Working Fluid ◽  
Metal Working ◽  
Factor Level ◽  
Working Fluids ◽  
Force Data

The growing cost associated with insurance, handling and disposing of conventional metal working fluids (oil and water based) continues to drive a need for alternative metal working fluids. An orthogonal tube turning machining experiment on AISI 1020 alloy steel was conducted to study the performance of High Speed Steel (HSS) tool inserts and carbide tool inserts utilizing cold compressed air and liquid nitrogen environments as the metal working fluid of choice The use of both high speed steel and carbide inserts allowed for direct comparison of geometrically identical inserts in customized tool holders that were used to present the tools with the geometrically identical tool rake angle alpha. Tool holder stiffness was therefore common to all tool rake angles compared. AISI 1020 steel was used because of its commercially dominant availability and usage. Cold cryogenic cooling was selected because of its growing usage in high performance machining applications. The use of cold compressed air has been much less studied in the machining of metals than in the machining of plastics and composites where it is quite commonly used. The comparisons between these two methods represent the first published values comparing the current extremes of gaseous metal working fluid applications in a commercial steel. This statistically designed experiment produced a large amount of comparative data that focused on the wear of the tools in two different cutting environments allowing for multivariate analysis of variance and regressive curve fitting. The orthogonal tube turning was set up on a conventional two axis HAAS TL-2 CNC tool room lathe. Forces were collected utilizing a standard Kistler force dynamometer to record the force data in X, Y and Z axes. Two levels of uncut chip thickness, 0.002 and 0.004” per revolution were maintained with a constant feed and depth of cut of 0.125” at different tool rake angles of 0°, 7° and 15°, with no chip breaker installed in the tool. Tool rake angles and depth of cuts were selected to ensure maximum statistical power/decisiveness of the experiment. The experiment was carried out for duration of 1 minute while the force data was collected for the entire duration of cut. New tool insert was used for each factor level combination. The traditional force analysis results are provided for an orthogonal tube turning experiment. In addition, all tools were analyzed for 3-dimensional rake face wear using an innovative Keyence white light microscope. Surprisingly, the inexpensive, simple cold compressed air produced less wear than the more expensive liquid nitrogen for all cutting factor level combinations.

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