scholarly journals Performance Analysis of Natural-Refrigerants-Based Vortex Tube Expansion Refrigeration Cycles

2013 ◽  
Vol 06 (2) ◽  
Keyword(s):  
Performance Improvement ◽  
Vortex Tube ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Design Parameters ◽  
Refrigeration Cycle ◽  
Expansion Valve ◽  
Tube Expansion ◽  
Vapour Compression ◽  
Cycle Temperature

The energetic analyses and comparison of three natural refrigerants, ammonia, propane and isobutane based vapour compression refrigeration cycles are presented in this article using a vortex tube as an expansion device. A simple thermodynamic model has been used for analyses of two vortex tube expansion refrigeration cycle layouts based on the Maurer model (1999) and the Keller model (1997). Effects of various operating and design parameters of the COP improvement using vortex tube instead of expansion valve are presented. Results show that the COP improvement over basic expansion cycle increases with increase in cycle temperature lift for both cycle layouts. The COP improvement of CYC1 can be realized for certain operating temperature combinations. Effects of design parameters on the performance improvement are negligible. Study shows that the COP improvement using vortex tube as an expansion device are dependent on the refrigerant varieties, operating conditions as well as cycle configurations. Using the vortex tube as an expansion device, isobutane yields a maximum COP improvement of 12.2% for CYC2 followed by propane (11.5% for CYC2), whereas ammonia yields negligible improvement for studies ranges.

Performance characteristics of natural-refrigerants- based ejector expansion refrigeration cycles

2009 ◽  
Vol 223 (5) ◽  
pp. 543-550 ◽  
Author(s):  
J Sarkar
Keyword(s):  
Heat Exchanger ◽  
Internal Heat ◽  
Area Ratio ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Internal Heat Exchanger ◽  
Optimum Parameters ◽  
And Performance ◽  
Vapour Compression ◽  
Cycle Temperature

The thermodynamic analyses and comparison of three natural-refrigerants-based vapour compression refrigeration cycles (ammonia, isobutane, and propane) are presented in this article using a constant pressure mixing ejector as an expansion device. Optimization of the area ratio of the ejector is done based on maximum cooling coefficient of performance (COP) and performance improvement for different operating conditions. The effect of using an internal heat exchanger is studied as well. Results show that optimum area ratio and cooling COP increases with a decrease in cycle temperature lift, whereas the COP improvement over basic expansion cycle increases with the increase in cycle temperature lift. Study shows that the optimum parameters, as well as performance using the ejector as an expansion device, are strongly dependent on the refrigerant properties as well as the operating conditions. The optimum area ratio is maximum for ammonia and minimum for propane, whereas maximum cooling COPs are similar. Using the ejector as an expansion device, propane yields a maximum COP improvement of 26.1 per cent followed by isobutane (22.8 per cent) and ammonia (11.7 per cent) for studies ranges. The effect of using an internal heat exchanger in the ejector expansion refrigeration cycle is found to be not profitable.

scholarly journals Purification of Methyl Acetate/Water Mixtures from Chemical Interesterification of Vegetable Oils by Pervaporation

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 775
Author(s):  
Abraham Casas ◽  
Ángel Pérez ◽  
María Jesús Ramos
Keyword(s):  
Methyl Acetate ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Biodiesel Production ◽  
Design Parameters ◽  
Chemical Interesterification ◽  
Permeate Flux ◽  
A Value ◽  
Pervaporation Membrane ◽  
Hydrophilic Character

Biodiesel production through chemical interesterification of triglycerides requires an excess of methyl acetate that must be recovered once the reaction is finished and the catalyst is neutralized. The present study concerns with the purification of methyl acetate by pervaporation. PERVAP 2201 was chosen as pervaporation membrane due to its high hydrophilic character that makes it suitable for the elimination of water in methyl acetate. Runs were started from concentrations in the feed of 2–8 wt.% of water and working temperatures close to the boiling point of methyl acetate (50, 60, and 70 °C), to get the main design parameters, i.e., permeate flux and selectivity. High temperature favored the permeate flux without compromising the selectivity. However, the flux declines significantly when water contained in the feed is below 2 wt.%. This implies that pervaporation should be used, only to decrease the water content to a value lower than in the azeotrope (2.3% by weight). A solution-diffusion model relating the flux of the permeating compound with the activity of the compound in the feed and the operating temperature has been proposed. The model obtained can be used in the design of the pervaporation stage, thus allowing to know the permeate flux for the different operating conditions.

Experimental Performance Comparison of a Single Cell and Multi-Cell Stack of High Temperature PEM Fuel Cell Prototype

2010 ◽  
Author(s):  
Susanta K. Das ◽  
Etim U. Ubong ◽  
Antonio Reis ◽  
K. Joel Berry
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Single Cell ◽  
Operating Temperature ◽  
Operating Conditions ◽  
Experimental Results ◽  
Design Parameters ◽  
Fuel Cell Stack ◽  
Current Voltage ◽  
Current Voltage Characteristics

In this study, we experimentally studied our newly designed and built single cell and multi-cell high temperature (140°C∼180°C) polymer electrolyte membrane (HTPEM) fuel cell stack prototype at different operating conditions to investigate the effects of operating temperature, pressure and CO concentration on the cell performance. In particular, the effects of these parameters on the current-voltage characteristics of the fuel cell stack are investigated extensively. Experimental results obtained from both the single cell and multi-cell stack with high temperature PBI-based membrane show that the high CO tolerance at high operating temperature of HTPEM fuel cell stack makes it possible to feed the reformate gas directly from the reformer without further CO removal. In order to develop design parameters for fuel reformer, experimental data of this type would be very useful. The experimental results revealed the fact that a fuel reformer is a consumer of heat and water, and the HTPEM fuel cell stacks are a producer of heat and water. Therefore, the integration of the fuel cell stack and the reformer is expected to improve the entire system’s performance and efficiency. The results obtained from this study showed significant variations in current-voltage characteristics of HTPEM fuel cell stack at different temperatures with different CO poisoning rates. The results are promising to understand the overall system performance development strategy of HTPEM fuel cell in terms of current-voltage characteristics while fed with on-site reformate with different CO ratios in the anode fuel stream.

Vortex Tube Expansion Two-Stage Transcritical CO2 Refrigeration Cycle

2012 ◽  
Vol 516-517 ◽  
pp. 1219-1223 ◽  
Author(s):  
Ying Fu Liu ◽  
Guang Ya Jin
Keyword(s):  
Mass Fraction ◽  
Vortex Tube ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Outlet Temperature ◽  
Two Stage ◽  
Evaporation Temperature ◽  
Optimum Heat ◽  
Tube Expansion ◽  
Cold Mass

Use of vortex tube as an expansion device in transcritical CO2 cycle could reduce the throttle loss and improve the coefficient of performance. In this paper, a vortex tube expansion two-stage transcritical CO2 refrigeration cycle(VTTC) is established and compared to that of the two-stage transcritical CO2 refrigeration cycle with throttle valve(TVTC). Thermodynamic analysis results indicate that there is also an optimum heat rejection pressure for the vortex tube cycle, and the COP improvement is 2.4%~16.3% at given conditions. Decrease in evaporation temperature or increase in gas-cooler outlet temperature decrease the COP, but the COP improvement will increase. The effect of cold mass fraction on the COP is negligible, but the COP improvement will increase fast with the increase of cold mass fraction.

CO2 Trans-Critical Two Stage Compression Refrigeration Cycle with Vortex Tube

2011 ◽  
Vol 52-54 ◽  
pp. 255-260 ◽  
Author(s):  
Ying Bai Xie ◽  
Kui Kui Cui ◽  
Zhi Chao Wang ◽  
Jian Lin Liu
Keyword(s):  
Mass Fraction ◽  
Vortex Tube ◽  
Refrigeration Cycle ◽  
Two Stage ◽  
Fluid Mass ◽  
Cold Fluid ◽  
Exit Temperature ◽  
Discharge Pressure ◽  
Tube Expansion ◽  
Cold Gas

The paper analyses CO2 trans-critical two stage compression refrigeration cycle with vortex tube expansion by thermodynamics method. And compare with CO2 trans-critical two stage compression refrigeration cycle with expansion value. The results show that in the calculated conditions of the paper, the performance of the cycle with vortex tube improves 2.4%~16.3% than the cycle with expansion value. The optimal discharge pressure maximizing COP of the cycle with vortex tube exists. With lower evaporating temperature or higher gas cooler exit temperature, COP of system decreases and COP improvement increases. The effect of cold fluid mass fraction on COP is not significant, but COP improvement increases more quickly with cold gas mass fraction increasing.

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