A Graph-Based Approach for Dynamic Compressor Modeling in Vapor Compression Systems

2017 ◽  
Author(s):  
Christopher T. Aksland ◽  
Justin P. Koeln ◽  
Andrew G. Alleyne
Keyword(s):  
Transient Behavior ◽  
Operating Conditions ◽  
Working Fluid ◽  
Vapor Compression ◽  
Thermal Dynamics ◽  
Thermal Capacitance ◽  
Initial Work ◽  
Fast Dynamic ◽  
Significant Effort ◽  
Vapor Compression Systems

Vapor compression systems are widely used as thermal management systems. To satisfy thermal demands, models are used to control and optimize the system’s performance, reliability, and efficiency. Significant effort has been made to model the condenser and evaporator, while there has been minimal focus on control-oriented modeling of the compressor. Initial work illustrates that during transient behavior, the working fluid exhibits a fast dynamic. However, during a startup and shutdown sequence, the working fluid follows a slower dynamic believed to be associated with heat transfer to the shell. To address both thermal dynamics, a graph-based modeling approach is used to incorporate the compressor shell’s thermal capacitance into the model. Experimental and simulation data are compared for a range of operating conditions including shutdown and startup dynamics.

Thermodynamic Analysis and Working Fluid Optimization of a Combined ORC-VCC System Using Waste Heat From a Marine Diesel Engine

2014 ◽  
Author(s):  
Oumayma Bounefour ◽  
Ahmed Ouadha
Keyword(s):  
Thermodynamic Analysis ◽  
Waste Heat ◽  
Operating Conditions ◽  
Working Fluid ◽  
Vapor Compression ◽  
Marine Diesel ◽  
Vapor Compression Refrigeration ◽  
Propylene Yield ◽  
Fluid Optimization ◽  
Propane Butane

This paper examines through a thermodynamic analysis the feasibility of using waste heat from marine Diesel engines to drive a vapor compression refrigeration system. Several working fluids including propane, butane, isobutane and propylene are considered. Results showed that isobutane and Butane yield the highest performance, whereas propane and propylene yield negligible improvement compared to R134a for operating conditions considered.

scholarly journals Performance Analysis of Solar Combined Ejector-Vapor Compression Cycle Using Environmental Friendly Refrigerants

2013 ◽  
Vol 14 (1) ◽  
Author(s):  
A. B. Kasaeian ◽  
S. Daviran
Keyword(s):  
Internal Heat ◽  
Exergy Efficiency ◽  
Operating Conditions ◽  
Working Fluid ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Environmental Friendly ◽  
Vapor Compression Cycle ◽  
Compression Cycle ◽  
Vapor Compression Refrigeration

In this study, a new model of a solar combined ejector-vapor compression refrigeration system has been considered. The system is equipped with an internal heat exchanger to enhance the performance of the cycle. The effects of working fluid and operating conditions on the system performance including COP, entrainment ratio (ω), compression ratio (rp) and exergy efficiency were investigated. Some working fluids suggested are: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e) and R1234ze(z). The results show that R114 and R1234ze(e) yield the highest COP and exergy efficiency followed by R123, R245fa, R365mfc, R141b, R152a and R600a. It is noticed that the COP value of the new solar ejector-vapor compression refrigeration cycle is higher than that of the conventional ejector cycle with R1234ze(e) for all operating conditions. This paper also demonstrates that R1234ze(e) will be a suitable refrigerant in the solar combined ejector-vapor compression refrigeration system, due to its environmental friendly properties and better performance. ABSTRAK: Kajian ini menganalisa model baru sistem penyejukan mampatan gabungan ejektor-wap solar.Sistem ini dilengkapi dengan penukar haba dalaman untuk meningkatkan prestasi kitaran.Kesan bendalir bekerja dan keadaan operasi pada prestasi sistem termasuk COP, nisbah pemerangkapan (ω), nisbah mampatan (rp) dan kecekapan eksergi telah disiasat.Beberapa bendalir bekerja yang dicadangkan adalah: R114, R141b, R123, R245fa, R600a, R365mfc, R1234ze(e) dan R1234ze(z).Hasil kajian menunjukkan R114 dan R1234ze(e) menghasilkan COP dan kecekapan eksergi tertinggi diikuti oleh R123, R245fa, R365mfc, R141b, R152a dan R600a.Didapati nilai COP kitaran penyejukan mampatan bagi ejektor-wap solar baru adalah lebih tinggi daripada kitaran ejektor konvensional dengan R1234ze(e) bagi semua keadaan operasi.Kertas kerja ini juga menunjukkan bahawa R1234ze(e) boleh menjadi penyejuk yang sesuai dalam sistem penyejukan mampatan gabungan ejektor -wap solar, kerana ianya mempunyai prestasi yang lebih baik serta sifatnya yang lebih mesra alam sekitar. KEYWORDS: environmental friendly refrigerants; solar combined ejector-vapor compression cycle; R1234ze(e)

Performance investigation of organic Rankine-vapor compression refrigeration integrated system activated by renewable energy

2019 ◽  
Vol 20 (2) ◽  
pp. 206 ◽  
Author(s):  
B. Saleh ◽  
Ayman A. Aly ◽  
Ageel F. Alogla ◽  
Awad M. Aljuaid ◽  
Mosleh M. Alharthi ◽  
...  
Keyword(s):  
Renewable Energy ◽  
System Performance ◽  
Organic Rankine Cycle ◽  
Integrated System ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Vapor Compression ◽  
Working Fluids ◽  
Vapor Compression Refrigeration

In this article, the performance and working fluid selection for an organic Rankine cycle-vapor compression refrigeration (ORC–VCR) integrated system activated by renewable energy is investigated. The performance of the system is described by the system coefficient of performance (COPS), and the refrigerant mass flow rate per kilowatt refrigeration capacity (m˙total). Twenty-three pure substances are proposed as working fluids for the integrated system. The basic integrated system performance is assessed and compared using the proposed working fluids. The basic VCR cycle works between 35 and 0 °C, while the basic ORC works between 35 and 100 °C. The impacts of different operating parameters such as the evaporator, the boiler, and the condenser temperatures on the ORC–VCR system performance are also examined. The results show that the cyclopentane accomplished the highest system performance under all investigated operating conditions. Accordingly, among the examined 23 working fluids, cyclopentane is the most appropriate working fluid for the integrated system from the viewpoints of environmental concerns and system performance. Nevertheless, due to its high flammability, further restrictions should be taken. The basic integrated system COPS, refrigeration effect, and the corresponding m˙total utilizing cyclopentane are 0.654, 361.3 kW, and 0.596 × 10−2 kg/(s kW), respectively.

Optimal Subcooling in Vapor Compression Systems via Extremum Seeking Control

2013 ◽  
Author(s):  
Justin P. Koeln ◽  
Andrew G. Alleyne
Keyword(s):  
System Architecture ◽  
Operating Conditions ◽  
Extremum Seeking ◽  
Vapor Compression ◽  
System Efficiency ◽  
Limited Information ◽  
Extremum Seeking Control ◽  
Additional Degree ◽  
Alternative System ◽  
Vapor Compression Systems

Building systems constitute a significant portion of the overall energy consumed each year in the U.S., and a large portion of this energy is used by air-conditioning systems. Therefore, the efficiency of these systems is important. This paper presents a method to increase system efficiency using an alternative system architecture for vapor compression systems. This architecture creates an additional degree of freedom which allows for independent control of condenser subcooling. It is found that there exists a non-zero subcooling that maximizes system efficiency; however, this optimal subcooling can change with different operating conditions. Thus, extremum seeking control is applied to find and track the optimal subcooling using only limited information of the system. In a simulation case study, a 10% reduction in energy consumption is reported when using the alternative system architecture and extremum seeking control when compared to a conventional system configuration.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

scholarly journals Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2585
Author(s):  
Jessica Guadalupe Tobal-Cupul ◽  
Estela Cerezo-Acevedo ◽  
Yair Yosias Arriola-Gil ◽  
Hector Fernando Gomez-Garcia ◽  
Victor Manuel Romero-Medina
Keyword(s):  
Sensitivity Analysis ◽  
Experimental Tests ◽  
Caribbean Sea ◽  
Ocean Model ◽  
Operating Conditions ◽  
Working Fluid ◽  
Ocean Energy ◽  
Mexican Caribbean ◽  
Water Temperature Data ◽  
Mass Flows

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.

scholarly journals Component-Oriented Modeling of a Micro-Scale Organic Rankine Cycle System for Waste Heat Recovery Applications

2021 ◽  
Vol 11 (5) ◽  
pp. 1984
Author(s):  
Ramin Moradi ◽  
Emanuele Habib ◽  
Enrico Bocci ◽  
Luca Cioccolanti
Keyword(s):  
Electric Power ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Micro Scale

Organic Rankine cycle (ORC) systems are some of the most suitable technologies to produce electricity from low-temperature waste heat. In this study, a non-regenerative, micro-scale ORC system was tested in off-design conditions using R134a as the working fluid. The experimental data were then used to tune the semi-empirical models of the main components of the system. Eventually, the models were used in a component-oriented system solver to map the system electric performance at varying operating conditions. The analysis highlighted the non-negligible impact of the plunger pump on the system performance Indeed, the experimental results showed that the low pump efficiency in the investigated operating range can lead to negative net electric power in some working conditions. For most data points, the expander and the pump isentropic efficiencies are found in the approximate ranges of 35% to 55% and 17% to 34%, respectively. Furthermore, the maximum net electric power was about 200 W with a net electric efficiency of about 1.2%, thus also stressing the importance of a proper selection of the pump for waste heat recovery applications.

A Transient 3D CFD Model of a Progressive Cavity Pump

2016 ◽  
Author(s):  
K. R. Mrinal ◽  
Md. Hamid Siddique ◽  
Abdus Samad
Keyword(s):  
Oil And Gas ◽  
Complex Geometry ◽  
Transient Behavior ◽  
Oil And Gas Industry ◽  
High Viscosity ◽  
Solid Content ◽  
Operating Conditions ◽  
Cfd Model ◽  
Ansys Fluent ◽  
Flow Variables

A progressive cavity pump (PCP) is a positive displacement pump and has been used as an artificial lift method in the oil and gas industry for pumping fluid with solid content and high viscosity. In a PCP, a single-lobe rotor rotates inside a double-lobe stator. Articles on computational works for flows through a PCP are limited because of transient behavior of flow, complex geometry and moving boundaries. In this paper, a 3D CFD model has been developed to predict the flow variables at different operating conditions. The flow is considered as incompressible, single phase, transient, and turbulent. The dynamic mesh model in Ansys-Fluent for the rotor mesh movement is used, and a user defined function (UDF) written in C language defines the rotor’s hypocycloid path. The mesh deformation is done with spring based smoothing and local remeshing technique. The computational results are compared with the experiment results available in the literature. Thepump gives maximum flowrate at zero differential pressure.

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