Theoretical Analysis and Experimental Researches on Internal Heat Exchanger in CO2 Trans-Critical Cycle

2012 ◽  
Vol 204-208 ◽  
pp. 4336-4342
Author(s):  
Hui Xia Lu ◽  
Jing Lv ◽  
Zhe Bin He ◽  
Jin Yu Wang ◽  
Jia Wei Zhou
Keyword(s):  
Heat Exchanger ◽  
Internal Heat ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Outlet Temperature ◽  
Internal Heat Exchanger ◽  
High Side ◽  
Side Pressure ◽  
Experimental Researches ◽  
Regenerative Cycle

The change of system performance caused by regenerative cycle in different operating conditions was analyzed in this paper, comparing the cycle with or without internal heat exchanger in a CO2 trans-critical cycle. We analyzed theoretically the performance of CO2 trans-critical cycle with the internal heat exchanger, and found that the coefficient increased with the decreasing of the high side pressure and the increasing of outlet temperature in gas cooler, in a certain range of the high side pressure and outlet temperature. The evaporation temperature could be raised when the system with internal heat exchanger and at the same time the coefficient of performance could be improved obviously. At lower high side pressure, the performance coefficient could be improved significantly by increasing the suction superheat. The higher the gas cooler outlet temperature was, the more obvious the increase was.

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.

Experimental Study of an Internal Heat Exchanger Influence on R134a Automobile Air Conditioning System

2012 ◽  
Vol 165 ◽  
pp. 145-149 ◽  
Author(s):  
Salman Bahrami ◽  
Hasan Mohammad Beigi ◽  
Mohammad Hosein Sabour
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Air Conditioning ◽  
Internal Heat ◽  
Low Pressure ◽  
Work Conditions ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Air Conditioning System ◽  
Internal Heat Exchanger

Liquid-suction or internal heat exchanger (IHX) is installed in vapor compression refrigeration systems to exchange energy between cool low-pressure gas and warm high-pressure liquid refrigerant. The aim of this research is to experimentally evaluate the effect of IHX adaptation in an automotive air conditioning system focusing on evaporator working conditions. In this new design of IHX, the high-pressure liquid passes through the central channel and the low-pressure vapor flows in several parallel channels in the opposite direction. The experimental set-up has been made up of original components of the air conditioning system of a medium sedan car, specially designed and built to analyze vehicle A/C equipments under real work conditions. The results show that low pressure drop will be imposed on the cycle using this type of IHX. Also, they confirm considerable decrease of compressor power consumption; it is intensified at higher evaporator air flow. A significant improvement of the coefficient of performance will be achieved with IHX too. The influence of operating conditions has been also discussed in this paper.

THERMODYNAMIC ANALYSIS AND EXPERIMENTAL RESEARCH OF TRANSCRITICAL CO2 CYCLE WITH INTERNAL HEAT EXCHANGER AND DUAL EXPANSION

2013 ◽  
Vol 21 (01) ◽  
pp. 1350005 ◽  
Author(s):  
Z. WANG ◽  
Y. GONG ◽  
X. H. WU ◽  
W. H. ZHANG ◽  
Y. L. LU
Keyword(s):  
Heat Exchanger ◽  
Experimental Evaluation ◽  
Pressure Fluctuations ◽  
Internal Heat ◽  
Energy Performance ◽  
Evaporation Temperature ◽  
Internal Heat Exchanger ◽  
Side Pressure ◽  
Wide Range ◽  
Compressor Power

This work presents the experimental evaluation of the energy performance of transcritical CO2 refrigeration and heat pump systems. The optimal gas cooler pressures and the optimal COP have been analyzed from a thermodynamic point of view. The systems used a new dual expansion valve and a balance CO2 liquid receiver adjustment device, which can control high and low side pressure effectively. Moreover, we demonstrate the influence of the internal heat exchanger (IHX) on the systems' performances, on the basis of the analysis of the relative COP index RCOPI, the compressor power index RPCI and other parameters which can confirm the truth of. The experimental evaluation covers five evaporating levels (-10 to 10°C) and in a wide range of gas cooler pressures (75 to 120 bar). It is concluded that with the IHX system, compressor power is relatively low when the high side pressure is over 100 bar, and the evaporation temperature is below 0°C. The COP of the system without the IHX is slightly higher than the system with the IHX; it is increasing about 3% to 5%, when the evaporation temperature is over 5°C. Relative to the single expansion process, the dual expansion cycle can decrease the influence of pressure fluctuations of CO2 supercritical fluid and liquid mixture on the systems.

Study on the Performance of the Organic Rankine Cycle System with Internal Heat Exchanger under Vehicle Engine Various Operating Conditions

2013 ◽  
Vol 856 ◽  
pp. 349-356 ◽  
Author(s):  
Kai Yang ◽  
Hong Guang Zhang ◽  
Zhen Wang ◽  
Jian Zhang ◽  
Fu Bin Yang ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Diesel Engine ◽  
High Speed ◽  
Organic Rankine Cycle ◽  
Internal Heat ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Combined System ◽  
Cycle System ◽  
Internal Heat Exchanger

Through experiment, the variation of the exhaust energy of the vehicle diesel engine is studied, a set of vehicle diesel engine-organic Rankine cycle (ORC) combined system with internal heat exchanger (IHE) is designed, the zeotropic mixtures R416A is used as the working fluids for the ORC system with IHE, by theoretical analysis and numerical calculation, the variation of the vehicle diesel engine-ORC combined system with IHE under entire operating conditions of the diesel engine is studied, the calculation results show that, when engine is operating at high speed and high torque, the performance of the vehicle diesel engine-ORC combined system with IHE is higher.

scholarly journals Numerical study on the influence of internal heat exchanger in transcritical CO2 heat pumps under optimal pressure conditions

2021 ◽  
Vol 2116 (1) ◽  
pp. 012098
Author(s):  
F Illán-Gómez ◽  
J R García-Cascales ◽  
F J Sánchez-Velasco ◽  
V Sena-Cuevas ◽  
R Otón-Martínez
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Strong Influence ◽  
Numerical Study ◽  
Internal Heat ◽  
Heat Pumps ◽  
Operating Conditions ◽  
Water Heater ◽  
Internal Heat Exchanger ◽  
Heat Pump Water Heater

Abstract This paper presents a numerical study on the influence of internal heat exchanger (IHX) exchanging surface in the performance of a transcritical CO2 heat pump water heater at different operating conditions. Five different IHX geometries and four different evaporation temperatures have been studied with water temperature ranging from 10 °C to 60 °C at the gas cooler inlet. The results show a strong influence of IHX characteristics on system’s performance.

Performance Analysis of Single Stage Compression Cycle with an Internal Heat Exchanger

2013 ◽  
Vol 753-755 ◽  
pp. 1401-1404
Author(s):  
Gui Jun Xue ◽  
Da Wei Liang ◽  
Guang Da Liu ◽  
Shui Qing Li ◽  
Zhen Jiang Zhou
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Performance Analysis ◽  
Internal Heat ◽  
Single Stage ◽  
Outlet Temperature ◽  
Outlet Pressure ◽  
Internal Heat Exchanger ◽  
Compression Cycle ◽  
Increasing Trend

With the increase of outlet pressure to compressor, all cycle COP is a reducing trend except R744, in addition, R744 compression cycle has an optimum high pressure. When the inlet temperatures of compressor gradually increase, the performances of all cycles basically unchanged, but the R744 compression cycle has an increasing trend. With the increasing of outlet temperature to the condenser, the performances of all cycles are decreased; instead with increasing of the evaporating temperature, all cycle COP is an increasing trend.

Performance Analysis of Single Stage Compression Cycle with an Internal Heat Exchanger

2012 ◽  
Vol 602-604 ◽  
pp. 1068-1071
Author(s):  
Hong Li Wang ◽  
Hui Qin Liu ◽  
Qi Long Tang ◽  
Ning Jia
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Performance Analysis ◽  
Internal Heat ◽  
Single Stage ◽  
Outlet Temperature ◽  
Internal Heat Exchanger ◽  
Compression Cycle ◽  
Increasing Trend

With increasing of high pressure, the performances of all kinds refrigerants except for R744 are all declined, transcritical R744 compression cycle has an optimum high pressure. With increasing of the evaporating temperature, all cycle COP is an increasing trend, with increasing of outlet temperature of condenser, the performances of all cycles are decreased. Under the same comparison conditions, the performance of R22 refrigerant cycle is superior to the cycles of other refrigerants, and the cycle of R11 refrigerant has the worst performance.

Performance Analysis of Two Stage Compression Cycle with an Internal Heat Exchanger

2014 ◽  
Vol 540 ◽  
pp. 110-113
Author(s):  
Hong Li Wang ◽  
Ning Jia ◽  
Jing Rui Tian
Keyword(s):  
High Pressure ◽  
Heat Exchanger ◽  
Internal Heat ◽  
Outlet Temperature ◽  
Minimum Level ◽  
Two Stage ◽  
Intermediate Pressure ◽  
Internal Heat Exchanger ◽  
Compression Cycle ◽  
Increasing Trend

With increasing of the evaporating temperature, the two stage compression cycle with an internal exchanger’s COP has an increasing trend. In addition, R744 achieves the highest COP, and the R12 achieves the minimum level. With increasing of the high pressure and the outlet temperature of the condenser, the two stage compression cycle has a down trend. In terms of the increasing intermediate pressure, the two stage cycle with different refrigerants has different performance: R12’s COP has a downtrend with the pressure changing from 1MPa-3MPa, the rest refrigerants all increased first, and then decreased. Except for R12, they all have optimal intermediate pressure.

Effects of an Internal Heat Exchanger in a Refrigerant System with Carbon Dioxide on Its Cooling Coefficient of Performance and Cooling Capacity

2008 ◽  
Vol 34 (5) ◽  
pp. 505-512 ◽  
Author(s):  
Shogo Tamaki ◽  
Yuuko Fujii ◽  
Yohsuke Matsushita ◽  
Hideyuki Aoki ◽  
Takatoshi Miura ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Internal Heat ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Internal Heat Exchanger

scholarly journals Thermodynamic Analysis of a CO2 Refrigeration Cycle with Integrated Mechanical Subcooling

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 4 ◽  
Author(s):  
Laura Nebot-Andrés ◽  
Daniel Calleja-Anta ◽  
Daniel Sánchez ◽  
Ramón Cabello ◽  
Rodrigo Llopis
Keyword(s):  
Thermodynamic Analysis ◽  
Internal Heat ◽  
Cooling Capacity ◽  
Point Of View ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Optimum Operating ◽  
Refrigeration Cycle ◽  
Internal Heat Exchanger ◽  
Promising Solution

Different alternatives are being studied nowadays in order to enhance the behavior of transcritical CO2 refrigeration plants. Among the most studied options, subcooling is one of the most analyzed methods in the last years, increasing cooling capacity and Coefficient Of Performance (COP), especially at high hot sink temperatures. A new cycle, called integrated mechanical subcooling cycle, has been developed, as a total-CO2 solution, to provide the subcooling in CO2 transcritical refrigeration cycles. It corresponds to a promising solution from the point of view of energy efficiency. The purpose of this work is to present, for the first time, thermodynamic analysis of a CO2 refrigeration cycle with integrated mechanical subcooling cycle from first and second law approaches. Using simplified models of the components, the optimum operating conditions, optimum gas-cooler pressure, and subcooling degree are determined in order to obtain the maximum COP. The main energy parameters of the system were analyzed for different evaporation levels and heat rejection temperatures. The exergy destruction was analyzed for each component, identifying the elements of the system that introduce more irreversibilities. It has been concluded that the new cycle could offer COP improvements from 11.7% to 15.9% in relation to single-stage cycles with internal heat exchanger (IHX) at 35 °C ambient temperature.

Sign in / Sign up

Export Citation Format

Share Document