scholarly journals HFO1234ze(e) As an Alternative Refrigerant for Ejector Cooling Technology

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4045
Author(s):  
Van Vu Nguyen ◽  
Szabolcs Varga ◽  
Vaclav Dvorak
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
The Other ◽  
Coefficient Of Performance ◽  
Fourth Generation ◽  
Working Fluid ◽  
Third Generation ◽  
Alternative Refrigerant ◽  
Overall Performance ◽  
Cooling Technology

The paper presented a mathematical assessment of selected refrigerants for the ejector cooling purpose. R1234ze(e) and R1234yf are the well-known refrigerants of hydrofluoroolefins (HFOs), the fourth-generation halocarbon refrigerants. Nature working fluids, R600a and R290, and third-generation refrigerant of halocarbon (hydrofluorocarbon, HFC), R32 and R152a, were selected in the assessment. A detail mathematical model of the ejector, as well as other components of the cycle, was built. The results showed that the coefficient of performance (COP) of R1234ze(e) was significantly higher than R600a at the same operating conditions. R1234yf’s performance was compatible with R290, and both were about 5% less than the previous two. The results also indicated that R152a offered the best performance among the selected refrigerants, but due to the high value of global warming potential, it did not fulfill the requirements of the current European refrigerant regulations. On the other hand, R1234ze(e) was the most suitable working fluid for the ejector cooling technology, thanks to its overall performance.

scholarly journals Performance Evaluation of a Gravity-Assisted Heat Pipe-Based Indirect Evaporative Cooler

Energies ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 200 ◽  
Author(s):  
Krzysztof Rajski ◽  
Jan Danielewicz ◽  
Ewa Brychcy
Keyword(s):  
Mathematical Model ◽  
Heat Pipe ◽  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Mass Transfer Processes ◽  
Air Cooler ◽  
Evaporative Cooler ◽  
The Mathematical Model ◽  
Further Development

In the present work, the effects of different operating parameters on the performance of a gravity-assisted heat pipe-based indirect evaporative cooler (GAHP-based IEC) were investigated. The aim of the theoretical study is to evaluate accurately the cooling performance indicators, such as the coefficient of performance (COP), wet bulb effectiveness, and cooling capacity. To predict the effectiveness of the air cooler under a variety of conditions, the comprehensive calculation method was adopted. A mathematical model was developed to simulate numerically the heat and mass transfer processes. The mathematical model was validated adequately using experimental data from the literature. Based on the conducted numerical simulations, the most favorable ranges of operating conditions for the GAHP-based IEC were established. Moreover, the conducted studies could contribute to the further development of novel evaporative cooling systems employing gravity-assisted heat pipes as efficient equipment for transferring heat.

Univocality within Multivocality

2010 ◽  
Vol 2 (2) ◽  
pp. 46-62 ◽  
Author(s):  
Elie Podeh
Keyword(s):  
Jewish History ◽  
Linear Process ◽  
History Textbooks ◽  
The Other ◽  
Fourth Generation ◽  
Third Generation ◽  
Gradual Improvement ◽  
The Third ◽  
The Past ◽  
The Way

Previous research on the way in which the Arab-Israeli conflict and the image of the Arab have been presented in Jewish history and civics textbooks established that there have been three phases, each typified by its own distinctive textbooks. The shift from the first to the third generation of textbooks saw a gradual improvement in the way the Other has been described, with the elimination of many biases, distortions and omissions. This article explores whether new history textbooks, published from 2000 to 2010, have entrenched or reversed this trend. With the escalation of the Israeli-Palestinian conflict since the early 2000s, one might have expected that the past linear process of improvement would be reversed. However, textbooks written over the last decade do not substantially differ from those written in the 1990s, during the heyday of the peace process. The overall picture is, therefore, that the current textbooks do not constitute a fourth generation.

Design and Evaluation of a MEMS-Based Stirling Microcooler

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Dongzhi Guo ◽  
Jinsheng Gao ◽  
Alan J. H. McGaughey ◽  
Gary K. Fedder ◽  
Matthew Moran ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Dead Volume ◽  
Working Fluid ◽  
Cooling Power ◽  
Phase Lag ◽  
Power Losses ◽  
Cold Side ◽  
Swept Volume

A new Stirling microrefrigeration system composed of arrays of silicon MEMS cooling elements has been designed and evaluated. The cooling elements are to be fabricated in a stacked array on a silicon wafer. A regenerator is placed between the compression (hot side) and expansion (cold side) diaphragms, which are driven electrostatically. Air at a pressure of 2 bar is the working fluid and is sealed in the system. Under operating conditions, the hot and cold diaphragms oscillate sinusoidally and out of phase such that heat is extracted to the expansion space and released from the compression space. Parametric study of the design shows the effects of phase lag between the hot space and cold space, swept volume ratio between the hot space and cold space, and dead volume ratio on the cooling power. Losses due to regenerator nonidealities are estimated and the effects of the operating frequency and the regenerator porosity on the cooler performance are explored. The optimal porosity for the best system coefficient of performance (COP) is identified.

scholarly journals Exergetic performance analysis of low GWP alternative refrigerants for R404A in a refrigeration system

2021 ◽  
Author(s):  
Mehmet Altinkaynak
Keyword(s):  
Cooling System ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Refrigeration System ◽  
Alternative Refrigerants ◽  
Condenser Temperature ◽  
Parametric Analyses ◽  
Low Global Warming Potential ◽  
Very High

Abstract According to the regulation of European Union laws in 2014, it was inevitable to switch to low global warming potential (GWP) fluids in the refrigeration systems where the R404A working fluid is currently used. The GWP of R404A is very high, and the potential for ozone depletion is zero. In this study, energetic and exergetic performance assessment of a theoretical refrigeration system was carried out for R404 refrigerant and its alternatives, comparatively. The analyses were made for R448A, R449A, R452A and R404A. The results of the analysis were presented separately in the tables and graphs. According to the results, the cooling system working with R448A exhibited the best performance with a coefficient of performance (COP) value of 2.467 within the alternatives of R404A followed by R449A and R452A, where the COP values were calculated as 2.419 and 2.313, respectively. In addition, the exergy efficiencies of the system were calculated as 20.62%, 20.22% and 19.33% for R448A, R449A and R452A, respectively. For the base calculations made for R404A, the COP of the system was estimated as 2.477, where the exergy efficiency was 20.71%. Under the same operating conditions, the total exergy destruction rates for R404A, R448A, R449A and R452A working fluids were found to be 3.201 kW, 3.217 kW, 3.298 kW and 3.488 kW, respectively. Furthermore, parametric analyses were carried out in order to investigate the effects of different system parameters such as evaporator and condenser temperature.

scholarly journals PRINCIPLES OF CONSTRUCTION OF THE GENERALIZED MATHEMATICAL MODEL OF THE HYDRAULIC EXTINGUISHER OF OSCILLATIONS OF THE PASSENGER CAR

2021 ◽  
Vol 1 (38) ◽  
pp. 173-184
Author(s):  
I. Shcherbyna
Keyword(s):  
Mathematical Model ◽  
Operating Conditions ◽  
Working Fluid ◽  
Operating Parameters ◽  
Hydraulic Systems ◽  
Passenger Cars ◽  
Passenger Car ◽  
Periodic Movement ◽  
Depth Analysis ◽  
The Impact

The study of the processes associated with the use of working fluids in the elements of hydraulic drives was preceded by studies of the unsteady periodic movement of the working fluid in the pipelines of hydraulic systems. Such processes take place in hydraulic drives and their elements, and are associated with the compressibility of the working fluid. The stability of the operation of hydraulic valves, which are supplied to hydraulic systems in order to maintain, within the required limits, pressures or flow rates, is also largely predetermined by non-stationary hydro mechanical processes occurring in the pipelines of these systems, channels and chambers of hydraulic devices. The peculiarities of the working processes of passive vibration dampers of passenger cars include the interaction of the working fluid with moving parts and its flow through the channels and through the calibrated holes with local artificial resistance. For in-depth analysis of changes in operating parameters, it is necessary to use a mathematical model that should reflect the processes that occur during the operation of the hydraulic device. In the presented article the generalized mathematical model of the hydraulic damper of fluctuations of the passenger car of the НЦ-1100 type is developed. This model takes into account the special operating conditions of the hydraulic shock absorber, which allows you to study the impact of operating parameters on the performance of the device.

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.

Parametric Analysis of a PULSCO Vent Silencer

2014 ◽  
Author(s):  
Usama Tohid ◽  
Chris Genger ◽  
John Kaiser ◽  
Ilaria Accorsi ◽  
Arturo Pacheco-Vega
Keyword(s):  
Mathematical Model ◽  
Parametric Study ◽  
Numerical Results ◽  
Operating Conditions ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Computational Domain ◽  
Hole Size ◽  
Plane Wave Solution ◽  
The Mathematical Model

We have conducted a parametric study via numerical simulations of a PULSCO vent silencer. The overall objective is to demonstrate the existence of an optimum system performance for a given set of operating conditions i.e., temperature, pressure, mass flow-rate and the working fluid, by modifying the corresponding geometry of the device. The vent silencer under consideration consists of a perforated diffuser, the silencer body and a tube module. The tube module consists of a set of tubes through which the working fluid passes. The flow tubes are perforated and surrounded with acoustic packing that is responsible for the attenuation. The mathematical model of the vent silencer is built upon Helmholtz equation for the plane wave solution, and the Delany-Bazley model for the acoustic packing. The geometrical parameters chosen for the parametric study include: the porosity of the diffuser and the flow tubes, the type of packing material used for the tube module, bulk density for the acoustic packing and the hole diameter of the perforated diffuser and flow tubes. The equations of the mathematical model are discretized over the computational domain and solved with a finite element method. Numerical results in terms of transmission loss, for the system, indicate that diffuser hole size of 1/4” with porosity of 0.1, flow tube hole size of 1/8” with porosity of 0.23, packing density of 16 kg/m3 for TRS-10 and 100 kg/m3 for Advantex provided the optimum results for the chosen set of conditions. The numerical results were found to be in agreement with experimental data.

scholarly journals Experimental Analysis of Refrigeration Ejector System by using Different Organic Refrigerants

2021 ◽  
Vol 9 (VII) ◽  
pp. 281-288
Author(s):  
P. V. Wakchaure
Keyword(s):  
Experimental Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Working Fluid ◽  
Cfd Simulations ◽  
Evaporator Temperature ◽  
Optimum Operating Condition ◽  
Condenser Temperature ◽  
Ejector System

This paper presents the experimental analysis performed on ejectors to optimize operating conditions like evaporator temperature, condenser temperature and generator temperature. Using the environmentally friendly working fluid R134a, R152a, R600a, R717 (Ammonia). Parametric analysis was performed to review the effect of blending chamber geometry on ejector performance which has direct impact on coefficient of performance of ejector refrigeration cycles. Results show that operating conditions and thus the effect of the deflection of the primary flow on the secondary flow is set. CFD simulations was performed to identify optimum geometry and optimum operating condition

Monitoring of genealogical structure development of East Bulgarian breed horses originating from stallions of other sporting breeds

2019 ◽  
Vol 11 (3) ◽  
pp. 195-197
Author(s):  
I. Sabeva ◽  
M. Popova
Keyword(s):  
Statistical Data ◽  
The Other ◽  
Fourth Generation ◽  
Third Generation ◽  
Structure Development ◽  
Productive Life ◽  
Breeding Activity ◽  
Set Up

Abstract. The origin of horses from the East Bulgarian breed, which descent from the other sport breeds stallions used for grading has been investigated. Genealogical structure development was traced by pedigree analyses of 1123 horses, born during the period from 2000 to 2018. The East Bulgarian Horse Association set of statistical data, concerning stallions’ breeding activity and productive life of their progeny were used. Two new lines with founders Hanoverians Da Kapo (GER) and Eistanzer (GER) were set up during the last four generations. Nowadays the line of stallion Da Kapo (GER) has developed in second and third generation after the founder and the line of stallion Eistanzer (GER) – in fourth generation after the founder. A small bulk of genealogical groups with origin traced to stallions Ladykiller, Cottage Son, Cor de la Bryere and Alme Z have developed.

Exergy Analysis of a Solar-Driven Dual Parallel-Connected Ejector Refrigeration System

2016 ◽  
Vol 839 ◽  
pp. 100-106
Author(s):  
Yahya Gaafar Abdella Mohammed ◽  
Tawat Suriwong ◽  
Sakda Somkun ◽  
Timeyo Mkamanga Maroyi
Keyword(s):  
Solar Collector ◽  
Exergy Analysis ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Saturated Steam ◽  
Working Fluid ◽  
Electric Heater ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Exergetic Efficiency

Nowadays, developing solar cooling technologies, especially ejector refrigeration system, has become preferable to scientific researchers. Exergy analysis is a technique in which the basis of evaluation of thermodynamic losses follows the second law rather than the first law of thermodynamics. An experimental exergy analysis of a solar-driven dual parallel-connected ejector (DPE) refrigeration system was conducted using water as working fluid. Saturated steam with 2 bar and 120oC was provided by heat–pipe evacuated tube solar collector with an assistant of an electric heater. The saturated stream was used as a motive flow for the ejectors. The exergy destruction and exergetic efficiency of the main components of the DPE refrigeration system were determined and compared with those when using a single ejector (SE) under same operating conditions. It was found that the most irreversibilities of both systems occurred at the solar collector, electric boiler and ejectors, respectively. Also, the total irreversibility (Exergy destruction) of the system when using DPE was lower than using a SE. In additions, the exergetic efficiency of the ejector, evaporator, and overall system when using DPE were increased by 21%, 10%, and 27%, respectively. The system thermal ratio (STR) and coefficient of performance (COP) of the system using DPE compared with SE were increased by 20% and 23%, respectively.

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