scholarly journals Elbel S., Hrnjak P. Performance optimization of two-stage compressor system using transcritical R744 / trans. from Engl. M. A. Fedorova

2021 ◽  
Vol 5 (2) ◽  
pp. 66-77
Author(s):  
M. A. Fedorova ◽  
Keyword(s):  
Performance Optimization ◽  
Geometric Mean ◽  
High Heat ◽  
Compression Process ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Discharge Temperature ◽  
Standard Design ◽  
Optimum Heat ◽  
High Pressure Level

The use of transcritical R744 systems has become increasingly popular in recent years in a variety of different applications. For applications that span a wide temperature range between the heat source and heat sink, the use of two-stage compressor results in numerous advantages in terms of efficiency and compressor discharge temperature. This paper presents experimental data for a transcritical R744 compressor system operating at high heat rejection temperatures. A comprehensive system model was developed and validated with the experimental results. Based on this, the simulation tool was used to further optimize the system design specifically to accommodate the two-stage compression process. The optimum heat transfer area distribution has been determined to simultaneously ensure efficient intercooling at intermediate pressure and gas cooling at the high-pressure level. Simultaneously, the system was also optimized with respect to optimal intermediate pressure and the results show that for this particular system, the optimum intercooler pressure deviated substantially from the standard design approach that uses the geometric mean between suction and discharge pressures

Optimum Refrigerating Efficiency and Exergy Index of a Two-Stage Refrigeration Cycle

Volume 1 ◽  
2004 ◽  
Author(s):  
J. S. Tiedeman ◽  
S. A. Sherif
Keyword(s):  
Performance Optimization ◽  
Geometric Mean ◽  
Maximum Error ◽  
Second Law ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Two Stage ◽  
Optimization Study ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

This paper presents results of an optimization study for a two-stage vapor compression refrigeration cycle based on the refrigerating efficiency and exergy index. Traditional two-stage refrigeration cycle studies have focused on the first law performance, while those studies dealing with the second law have primarily been limited to performance analysis as opposed to performance optimization. Results of this study indicate that the use of the common approximation of the geometric mean to find the optimum interstage pressure leads to nearly optimum results for the refrigerating efficiency, with maximum error in the neighborhood of 5%. However, the error associated with using this approximation to find the optimum exergy index is too large, approaching 15%. Second law optimization revealed that the optimum data curves themselves have maxima for each set of conditions tested. There are a series of conditions that lead to the conclusion that, for a given system, there is an optimum set of conditions that lead to the lowest amount of exergy destruction for that system. Polynomial equations have been fitted to the resultant optimum data for the refrigerating efficiency and exergy index. These equations allow for the reproduction of optimum points based on high- and low-pressure compressor efficiencies and condenser and evaporator pressures.

Optimum coefficient of performance and exergetic efficiency of a two-stage vapour compression refrigeration system

2003 ◽  
Vol 217 (9) ◽  
pp. 1027-1037 ◽  
Author(s):  
J S Tiedeman ◽  
S A Sherif
Keyword(s):  
Performance Optimization ◽  
Geometric Mean ◽  
Coefficient Of Performance ◽  
Second Law ◽  
Refrigeration System ◽  
Exergetic Efficiency ◽  
Two Stage ◽  
Optimization Study ◽  
The Common ◽  
Vapour Compression

This paper presents the results of an optimization study for a two-stage vapour compression refrigeration system based on the coefficient of performance (COP) and exergetic efficiency. Traditional studies have focused on the first-law performance, while those studies dealing with the second law have primarily been limited to performance analysis as opposed to performance optimization. The results of this study indicate that the use of the common approximation of the geometric mean to find the optimum interstage pressure can lead to significant errors in interstage pressure. However, an optimum COP or exergetic efficiency based on the same interstage pressure has relatively little error. This trend is valid as long as the isentropic compressor efficiencies are ‘reasonable’. Second-law optimization revealed that the optimum data curves themselves have a maxima for each set of conditions tested. This leads to the conclusion that for a given system there is an optimum set of conditions that lead to the lowest amount of exergy destruction for that system. This is shown to occur consistently for reasons that are, as yet, undetermined. Finally, polynomial equations have been fitted to the resultant optimum data for the interstage pressure, COP and exergetic efficiency. These equations allow for the reproduction of optimum points based on high-and low-pressure compressor efficiencies and condenser and evaporator pressures.

Performance Analysis of Transcritical CO2 Two Stage Compression Cycle with an Intercooler (TSCC+IC) and the Cycle with an Expander (TSCE+IC)

2012 ◽  
Vol 538-541 ◽  
pp. 1998-2002 ◽  
Author(s):  
Jing Rui Tian ◽  
Hong Li Wang ◽  
Hui Qin Liu
Keyword(s):  
High Pressure ◽  
Heat Pumps ◽  
Cycle Performance ◽  
Outlet Temperature ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Discharge Temperature ◽  
Compression Cycle ◽  
Increasing Trend ◽  
Better Than

In range of high pressure, the performance of two stage compression cycle with an expander (TSCE+IC) is better than the two stage cycle with an intercooler (TSCC+IC). In the cycle (TSCE+IC), the optimum discharge temperature is 42°C and the highest COP is 3.3, in the cycle (TSCC+IC), the optimum discharge temperature is 50°C and the highest COP is 3.07. In the cycle (TSCC+IC), the optimum intermediate pressure is 5.8MPa and the highest COP is 3.08, in the cycle (TSCE+IC), the optimum intermediate pressure is 6.2MPa and the highest COP is 3.33. With increasing of evaporating temperature or decreasing outlet temperature of gas cooler, the performance of cycle (TSCE+IC) or cycle (TSCC+IC) is an increasing trend. Under the same conditions, expander cycle performance superior to the throttle valve performance. Some fundamental data were obtained for improving cycle performance and developing the products of CO2 refrigeration air condition and heat pumps.

scholarly journals Performance Optimizations of the Transcritical CO2 Two-Stage Compression Refrigeration System and Influences of the Auxiliary Gas Cooler

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5578
Author(s):  
Yuyao Sun ◽  
Jinfeng Wang ◽  
Jing Xie
Keyword(s):  
Exergy Analysis ◽  
Energy Analysis ◽  
Exergy Efficiency ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
System Operation ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Discharge Temperature ◽  
Performance Optimizations

To optimize the performance of the transcritical CO2 two-stage compression refrigeration system, the energy analysis and the exergy analysis are conducted. It is found that higher COP, lower compression power, and less exergy destruction can be achieved when the auxiliary gas cooler is applied. Moreover, the discharge temperature of the compound compressor (HPS) can be reduced by decreasing the temperature at the outlet of the auxiliary gas cooler (Tagc,out). When the Tagc,out is reduced from 30 to 12 ℃, the discharge temperature of the compound compressor (HPS) can be decreased by 13.83 ℃. Furthermore, the COP and the exergy efficiency can be raised by enhancing the intermediate pressure. Based on these results, the optimizations of system design and system operation are put forward. The application of the auxiliary gas cooler can improve the performance of the transcritical CO2 two-stage compression refrigeration system. Operators can decrease the discharge temperature of the compound compressor (HPS) by reducing the Tagc,out, and increase the COP and the exergy efficiency by enhancing the intermediate pressure.

scholarly journals Two-Stage Multi-Objective Meta-Heuristics for Environmental and Cost-Optimal Energy Refurbishment at District Level

2019 ◽  
Vol 11 (5) ◽  
pp. 1495 ◽  
Author(s):  
Diana Manjarres ◽  
Lara Mabe ◽  
Xabat Oregi ◽  
Itziar Landa-Torres
Keyword(s):  
Performance Optimization ◽  
Energy Demand ◽  
Harmony Search ◽  
Economic Assessment ◽  
District Level ◽  
The European Union ◽  
Two Stage ◽  
Nsga Ii ◽  
Multi Objective ◽  
Payback Time

Energy efficiency and environmental performance optimization at the district level are following an upward trend mostly triggered by minimizing the Global Warming Potential (GWP) to 20% by 2020 and 40% by 2030 settled by the European Union (EU) compared with 1990 levels. This paper advances over the state of the art by proposing two novel multi-objective algorithms, named Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-Objective Harmony Search (MOHS), aimed at achieving cost-effective energy refurbishment scenarios and allowing at district level the decision-making procedure. This challenge is not trivial since the optimisation process must provide feasible solutions for a simultaneous environmental and economic assessment at district scale taking into consideration highly demanding real-based constraints regarding district and buildings’ specific requirements. Consequently, in this paper, a two-stage optimization methodology is proposed in order to reduce the energy demand and fossil fuel consumption with an affordable investment cost at building level and minimize the total payback time while minimizing the GWP at district level. Aimed at demonstrating the effectiveness of the proposed two-stage multi-objective approaches, this work presents simulation results at two real district case studies in Donostia-San Sebastian (Spain) for which up to a 30% of reduction of GWP at district level is obtained for a Payback Time (PT) of 2–3 years.

A Numerical Model of a Reciprocating-Mechanism Driven Heat Loop for Two-Phase High Heat Flux Cooling

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Olubunmi Popoola ◽  
Ayobami Bamgbade ◽  
Yiding Cao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Numerical Model ◽  
Performance Optimization ◽  
Numerical Study ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
Transfer Device

An effective design option for a cooling system is to use a two-phase pumped cooling loop to simultaneously satisfy the temperature uniformity and high heat flux requirements. A reciprocating-mechanism driven heat loop (RMDHL) is a novel heat transfer device that could attain a high heat transfer rate through a reciprocating flow of the two-phase working fluid inside the heat transfer device. Although the device has been tested and validated experimentally, analytical or numerical study has not been undertaken to understand its working mechanism and provide guidance for the device design. The objective of this paper is to develop a numerical model for the RMDHL to predict its operational performance under different working conditions. The developed numerical model has been successfully validated by the existing experimental data and will provide a powerful tool for the design and performance optimization of future RMDHLs. The study also reveals that the maximum velocity in the flow occurs near the wall rather than at the center of the pipe, as in the case of unidirectional steady flow. This higher velocity near the wall may help to explain the enhanced heat transfer of an RMDHL.

Theoretical performance of transcritical carbon dioxide cycle with two-stage compression and intercooling

2005 ◽  
Vol 219 (2) ◽  
pp. 187-195 ◽  
Author(s):  
J. S. Baek ◽  
E. A. Groll ◽  
P. B. Lawless
Keyword(s):  
Carbon Dioxide ◽  
System Analysis ◽  
Coefficient Of Performance ◽  
System Efficiency ◽  
Compression Process ◽  
Two Stage ◽  
Bell Curve ◽  
Second Stage ◽  
Transcritical Carbon Dioxide ◽  
Theoretical Performance

A computer model was developed to perform a thermodynamic analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling. In typical two-stage compression with intercooling applications, the intercooler serves the purpose of cooling the fluid to the lowest possible temperature before it enters the second-stage compressor. This paper presents the results of the system analysis of the transcritical carbon dioxide cycle with two-stage compression and intercooling (intercooler cycle) and identifies the pressure ratios that provide maximum system efficiency. The results show that the coefficient of performance (COP), curves of the intercooler cycle are different from the ‘typical bell curve behaviours’ that are observed when plotting the COP versus the intermediate pressure with assumptions of isentropic and real compression process.

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