Mechanical Subcooling Research Articles

SENSITIVITY ANALYSIS ON HEAT EXCHANGERS SELECTION AND ITS INFLUENCE ON THE EFFICIENCY OF A TRANSCRITICAL CO2 CYCLE WITH INDIRECT DEDICATED MECHANICAL SUBCOOLING

This work evaluates through numerical modeling, the efficiency of an air-to-water heat pump that operates using a transcritical CO2 cycle assisted by an indirect dedicated mechanical subcooling (IDMS) cycle, with R1234ze(E) as the refrigerant. The research aims to analyze how the size of the heat exchangers used as the evaporator and the condenser for the IDMS cycle affects the overall efficiency of the system. A numerical model previously developed in Matlab® is used to modify the refrigerant and compressor of the IDMS cycle and to determine the optimal number of evaporator and condenser plates that maximize the efficiency of the whole system. The compressor model is derived from manufacturer correlations, whereas the models for the heat exchangers are obtained through a parametric study developed using IMST-ART® to characterize their operating parameters based on their number of plates and the inlet conditions of water and refrigerant. Once the models are developed, they are integrated into the model of the overall system to find the heat exchanger sizes that maximize the efficiency of the system.

Transcritical CO2 system with two-stage throttling for supermarkets: Field tests, energy and emission performance assessment in China

Transcritical CO2 system is eco-friendly for the application of refrigeration and cooling in supermarket. To evaluate the applicability of transcritical CO2 supermarket refrigeration system in China with different climate regions, this study focuses on the field tests of a transcritical CO2 two-stage throttling system in a supermarket in Suzhou, Jiangsu Province, China. Furthermore, based on the tested data, the system energy and emissions performance models of four system configurations are also developed and validated, including the system integrated with an internal heat exchanger, a parallel compression, and mechanically assisted subcooling. In order to improve the usability of the system in different climatic zones, 40 cities were selected for calculation in China. Five representative cities (Beijing, Harbin, Xiamen, Chongqing, and Kunming) located in different climate regions of China are selected, and the annual performance factor and life cycle climate performance (LCCP) are determined to evaluate the application potential of the CO2 refrigeration systems in different climate conditions. The tested results show the operation mode of transcritical and subcritical changes occurs at an ambient temperature of about 27 °C, at which the coefficient of performance (COP), compressor discharge pressure and discharge temperature change dramatically. The simulation results demonstrate that the mechanical subcooling system shows the best performance. The annual performance factor can be improved by 18.69 % when the mechanical subcooling is adopted. For the case of the system used in Xiamen by using mechanical subcooling, the carbon emissions can be reduced by 19.3 %.

Experimental study of the effect of dedicated mechanical subcooling on the performance of a single multiparallel evaporator

In systems with a single machine and multiple parallel evaporators, issues such as uneven liquid–vapor phase refrigerant separation and low efficiency are prevalent. This study investigates the impact of distributor inlet conditions on liquid–vapor separation uniformity and proposes improving separation performance and system efficiency by adjusting the working fluid's dryness through subcooling. It introduces the use of a rectifying nozzle-type distributor (RD) instead of a centrifugal distributor (CD) and presents experimental studies on multiple parallel evaporators. A test setup featuring multiple parallel evaporators with mechanical subcooling unit was developed to investigate the subcooling degree's impact on various aspects: superheat unevenness across branches, refrigeration capacity disparity among cold storages, cooling rates, distributor pressure drop, and overall system energy efficiency. Findings indicate significant improvements with RD; at a 16 °C subcooling degree, superheat unevenness and refrigeration capacity unevenness decreased by 30.6 % and 23.0 % respectively, while cooling rates increased by 27.3 %. At a 26 °C subcooling degree, system energy efficiency improved by 15.4 %. Compared under identical conditions, the RD system outperformed the CD system. This research contributes to a better understanding of optimizing multiple parallel evaporator performance through subcooling degree adjustments and can be applied to multi-cold room cold storage systems.

ENERGY AND ENVIRONMENTAL ASSESSMENT OF CO2 BOOSTER REFRIGERATION CYCLES WITH FLOODED EVAPORATORS AND PARALLEL COMPRESSOR FOR SUPERMARKETS IN TÜRKİYE

CO2 booster refrigeration systems have higher energy efficiency and are more environmentally friendly. Therefore, the CO2 booster refrigeration cycle with flooded evaporators and parallel compressors (BFP), BFP with mechanical subcooling (BFP-MSC), and BFP with evaporative cooling (BFP-EVC) are investigated for supermarkets in this study. For the first time in the literature, these systems are analyzed to present which system performs better in terms of energy and environmental performance for Türkiye. According to the results of the investigation, BFP-MSC has a better coefficient of performance (COP) values than BFP, with up to a 16.67% increase at equivalent dry bulb temperatures. Meanwhile, BFP-EVC has the lowest annual energy consumption (AEC) in each city, followed by BFP-MSC and then BFP. Annual savings obtained by BFP-EVC over BFP vary between 10.81% to 25.47%. Additionally, BFP-EVC offers more substantial savings in cities with lower humidity levels, as it was analyzed with respect to wet bulb temperatures.

Multi-objective optimization analysis of combined heating and cooling transcritical CO2 system integrated with mechanical subcooling utilizing hydrocarbon mixture based on machine learning

To meet the simultaneous needs of high temperature disinfection and freezing in the field of food processing, a new concept of combined heating and cooling transcritical CO2 system integrated with dedicated mechanical subcooling utilizing hydrocarbon mixture is proposed. The system performance in terms of thermodynamics, economy and environment is studied and compared with the baseline combined heating and cooling transcritical CO2 system and four traditional combined heating and cooling solutions, considering the influence of temperature glide and the heat transfer deterioration. The new proposed system is further optimized by using the machine learning method of artificial neural network and non-dominated sorting genetic algorithm. Multi-objective optimization is conducted considering the objective function of energy efficiency, initial capital cost and life cycle carbon emissions of the new system, to obtain the optimum components and concentration ratio of the hydrocarbon mixture. The results indicate the thermodynamic performance and environmental benefits of subcooling subsystem with hydrocarbon mixture are better than those of the pure system. In contrast to that using pure R290 and R601, the coefficient of performance is enhanced by 8.20 % and 8.13 % and the life cycle carbon emission is reduced by 8.54 % and 9.31 %, respectively, when R290/R601 (50/50) is used. However, the initial capital cost is 9.25 % and 10.23 % higher than that of pure R290 and R601, respectively. Finally, the hydrocarbon mixture corresponding to the optimal design point is R1270/R601a (53/47), the corresponding discharge pressure is 12.86 MPa, and the subcooling degree is 37.50 °C. This study can provide a theoretical reference for the application of CO2 refrigeration and heat pump technology.

Exergy, carbon footprint and cost lifecycle evaluation of cascade mechanical subcooling CO2 commercial refrigeration system in China

The concept of cascade mechanical subcooling is recommended to widen the application of natural working fluid CO2, improve the efficiency and reduce the carbon footprint of CO2 refrigeration system applied in commercial supermarket. Three potential configurations for CO2 system with integrated multi-stage dedicated mechanical subcooling (MS-DMS) are proposed as prospect solutions. Life cycle assessment is conducted from the viewpoint of exergy, carbon footprint and cost performance for the proposed refrigeration systems, and compared with baseline CO2 booster refrigeration system (BASE) and traditional R404A system. 8 representative cities located in diverse climatic zones across China are chosen as scenarios and discussed in detail. The results indicate the irreversible loss is efficiently reduced with the utilization of MS-DMS. The annual exergy efficiency of CO2 system integrated with triple-stage DMS (TS-DMS) is 11.92–18.48% higher than BASE. Life cycle climate performance (LCCP) is reduced by 6.87% when the TS-DMS is employed in Haikou in contrast to BASE from the perspective of carbon emissions. Additionally, the life cycle cost (LCC) is remarkably reduced by 6.8% compared with BASE. Consequently, MS-DMS CO2 systems are more suitable for the application in warm or hot regions in contrast to BASE due to its better emission reduction performance as well as lower life cycle cost.

Experimental assessment of CO2/R-152a mixtures in a refrigeration plant with integrated mechanical subcooling

During the last years, CO2 utilization has grown in the refrigeration sector, especially in medium and large size plants. These cycles have implemented complex architectures to improve their energetic performance and be cost-effective. One of the most advanced architectures is cycle with the integrated mechanical subcooling. This work aims to experimentally evaluate the performance of this cycle using CO2/R-152a mixtures. Two R-152a mass concentrations, 5 % and 10 %, are selected for testing on a test rig at heat rejection temperatures from 20 °C to 40 °C with 5 °C step and at one temperature (2.50 °C of secondary fluid) at the inlet of the evaporator. The results show that the use of CO2/R-152a mixtures improves COP values of the cycle, confirming the trend observed in previous studies. However, it is observed that the cooling capacity decreases compared to pure CO2 due to the reduction in volumetric cooling capacity. The introduction of R-152a increases both critical temperature and pressure, and reduce the optimum heat rejection pressure, enabling more efficient operation in subcritical conditions. The study determines an upper limit for the R-152a mass fraction (10 %) beyond which the behaviour of the IMS cycle gets worse significantly compared to pure CO2.

Performance enhancement and environmental analysis of vapor compression refrigeration system with dedicated mechanical subcooling

The primary focus of this study is on the energy, exergy, and environmental (3E) analysis of a dedicated mechanical subcooled vapor compression refrigeration (DMS-VCR) system for applications involving commercially available water chillers that employ R134a (in both subcooler and main cycle). For a cooling capacity of 100-kW water chillers, the mathematical model of the DMS-VCR system is built to determine the performance parameter of the system. The DMS-VCR system reduces electricity usage by 15.52% and increase in COP by 9.5%, which results in a significant reduction in CO2 emissions of about 15.55%. When compared to equivalent vapor compression refrigeration system (VCRS), the system’s exergetic efficiency is also increased by 8%. Since the computer simulation results will undoubtedly give design engineers a better option, the subcooling and superheating of the vapor compression refrigeration system become alluring in this study. Consequently, the DMS-VCR system performs better as per the combined 3E study.

CO2 system integrated with ejector and mechanical subcooling: A comprehensive assessment

To achieve the goal of clean annual space heating and cooling for residential buildings, the concept of annual space heating and cooling transcritical CO2 system combined with ejector and mechanical subcooling is proposed. The problem of large throttling loss and performance degradation when CO2 system is applied for residential space heating and cooling can be solved. A theoretical model of the new proposed system is developed, and then optimized by the method of genetic algorithm. Moreover, taking an ordinary residential building located in 70 cities belonging to different climate zones as the application scenario, the seasonal, annual, environmental, and economic performance of eight heating and cooling solutions are compared and discussed. The results indicate that the COP and exergy efficiency of the new proposed system is significantly improved in contrast to conventional mechanical subcooling system, which increases by 11.48% and 21.64% in heating mode, and 8.99% and 8.69% in cooling mode, respectively. The annual performance coefficient of the new proposed system is 7.21%∼8.21% higher than conventional mechanical subcooling system. Additionally, the life cycle carbon emissions of the new proposed system can be significantly reduced by 12.23%∼89.58% compared with the combined solution of coal-fired boiler and R32. With the advancement of CO2 technology, it is possible to improve the economic performance of CO2 systems and the price of the new proposed system is lower than all solutions when the price of compressor is reduced by 60%. This study can provide a theoretical reference for the development and optimization of CO2 combined heating and cooling system, and provide a feasible solution for residential annual space heating and cooling.

Experimental evaluation of the effect of mechanical subcooling on a hydrocarbon heat pump system

In addition to the progressive movement of countries towards the use of renewable energy sources, efficient energy consumption is another important goal set by the International Energy Agency. In heat pump technology, the use of mechanical subcooling system has a high potential for this purpose. In this experimental study, the impact of using a mechanical subcooling cycle on the performance of a heat pump system is investigated. The system is designed to supply heat at condensing temperatures of 50, 60 and 70 °C. Propane and isobutane are used as low GWP refrigerants in the main and secondary cycles, respectively. The results revealed that both the COP and heating capacity of the system are increased by adding the mechanical subcooling cycle up to 15.1% and 34%, respectively. To express the improvement of the system performance by means of the TEWI index, a reduction of 9–13% is calculated when the mechanical subcooling cycle is included. It is also of interest that the cooling coefficient of performance (COP2) is improved by adjoining a secondary cycle as a liquid subcooler. An optimal power ratio between the basic cycle and the secondary cycle was obtained, which is consistent with the simulation results.

Next generation of ejector-supported R744 booster systems for commercial refrigeration at all climates

The pernicious effects of synthetic refrigerants on different environmental aspects leave natural refrigerants as the only alternative for vapour compressions systems. Among natural refrigerants, CO2 (R744) has become the preferred choice for commercial refrigeration at almost any location and climate. However, efficient R744 refrigeration systems for warm climates have a great level of complexity, implementing technologies such as mechanical subcooling or ejector that increase the investment costs. The goal of the novel hybrid configuration presented in this work is to simplify ejector-supported R744 commercial refrigeration systems while maintaining all the benefits of the ejector implementation in transcritical operation mode. Moreover, utilization of a low-pressure accumulator layout in the subcritical mode removes all the practical challenges related to the booster layout operating at low ambient temperatures. This solution is based on: (i) MT and LT compressor suction groups, (ii) non-superheated MT evaporation with increased evaporation temperature, and (iii) ejector utilization throughout the year. The ejector is actively operated as a high-pressure-control device at elevated ambient temperatures ('summer mode'), while it is passive and acts as a check-valve at lower ambient temperatures ('winter mode'). The experimental campaign performed proved that this novel system configuration is more energy efficient than booster systems with parallel compressors at any condition, improving the COP by around 40 % at the most extreme gas cooler outlet temperatures tested, i.e., 40 °C (summer mode) and 10 °C (winter mode).

Evaluation of the Use of Different Dedicated Mechanical Subcooling (DMS) Strategies in a Water Source Transcritical CO2 Heat Pump for Space Heating Applications

In this work we analyze numerically different design configurations to be used in a R1234yf DMS cycle coupled with a water source, transcritical CO2 heat pump for heating applications in the building sector. Specifically, we study the temperature range proposed by a European standard for heating with inlet/outlet water temperatures of: 30 °C/35 °C, 40 °C/45 °C, 47 °C/55 °C and 55 °C/65 °C. Moreover, 25 °C/30 °C is also analyzed which is the range expected for indoor swimming pool water pool heating applications. A water inlet temperature of 10 °C at the evaporator was considered in all of the cases. Results show that depending on the coupling strategy between the DMS cycle and the CO2 heat pump, optimal COP values obtained can vary up to 30% whereas the optimal operating pressure of the CO2 cycle can vary up to 8%. A configuration based on splitting the water flow to be heated into the DMS condenser and the gas cooler in a system with IHX was the best option for all the temperature ranges studied. The improvement in the maximum COP values obtained with this configuration ranges between 5% (for swimming pool applications) and 25% (for space heating with 40 °C/45 °C) when compared with the base cycle depending on the water temperature range considered. When this configuration is not considered, the basic transcritical CO2 with IHX and without DMS was found the best option.

Numerical performance of a water source transcritical CO2 heat pump with mechanical subcooling

In order to improve their efficiency, transcritical CO2 heat pumps need to resort to the use of a subcooling method. Among the different subcooling methods, dedicated mechanical subcooling (DMS) systems and internal heat exchangers (IHX) are currently the more promising technologies. This paper presents a numerical study of a transcritical water source CO2 heat pump during hot water generation using different subcooling methods. Ten different configurations, including both, IHX and DMS, separately and combined in different layouts, some of them not studied previously, are analyzed numerically under the same operating conditions in order to compare their performance. A description of the numerical model is presented: compressors are modeled using the performance curves provided by their manufacturers, expansion valves are modeled as isenthalpic, and heat exchangers are modeled by deriving correlations for the evaporation/condensation pressure and heat transfer rate obtained using a 1D cell-by-cell discretization method previously applied to all heat exchangers. Results are presented for different water heating conditions and show that in most configurations analyzed, the use of a DMS does not improve the performance of the system compared to the base system with IHX. There is only an improvement in the efficiency for two of the configurations analyzed, those in which the main CO2 cycle and the DMS cycle are coupled by the water flowing first through the evaporator of the auxiliary cycle and then through the gas cooler of the main cycle. Specifically, compared to the base cycle with IHX, the configuration that provides the best results (Conf. F* according to the nomenclature used in this work) gives average improvements of around 26% in efficiency and almost 160% in the heating capacity, while the optimum gas cooler pressure is reduced by an average of 12%. Even more, compared to the best performance system previously studied by other authors (indirect DMS without IHX, Conf. F in this work) this configuration improves the efficiency by almost 8.5%, with a decrease in the total capacity lower than 1% and similar gas cooler pressure. The results also show that the auxiliary compressor capacity and the way in which the water is distributed among the main and the auxiliary cycle have an important influence on the efficiency of the system, although that influence depends on the configuration studied. For the configuration that provides the best efficiency (Conf. F*), the optimum efficiency is obtained when the auxiliary compressor capacity is similar to the capacity of the main compressor (55% of the total heating capacity comes from the auxiliary cycle), and the water is mostly heated in the auxiliary cycle (85% of the water flow heated in the condenser of the auxiliary cycle, 15% heated in the gas cooler of the main cycle).

Hybrid CO2 air source heat pump system integrating with vapor injection and mechanical subcooling technology for space heating of global application: Life cycle techno-energy-enviro-economics assessment

As a heating method for the sustainability of residential buildings in clean space heating, carbon dioxide (CO2) air source heat pump is an environment-friendly solution to replace fuel-fired boiler. Four hybrid configurations of vapor injection integrated with dedicated mechanical subcooling (VI + DMS) technologies are developed, to deal with the problem of traditional CO2 system energy efficiency deterioration in cold regions, and compared with traditional transcritical CO2 baseline heat pump (BASE), R410A heat pump, coal-fired boiler and four CO2 heat pump systems adopting single technique of VI or DMS. Genetic algorithm is utilized to optimize the operation variables. The comprehensive techno-energy-enviro-economics performances of the nine systems among the whole lifetime are assessed. The influences of heating terminal selection and climate condition are discussed for 40 typical cities in 8 climate zones around the world. The results demonstrate a maximum coefficient of performance (COP) is obtained for transcritical CO2 vapor injection heat pump with flash tank and dedicated mechanical subcooling (VI-FT-DMS), and the COP of VI-FT-DMS system using traditional designed radiator as heating terminal is as high as 1.94 at the ambient temperature of −30 °C. The hybrid VI + DMS CO2 heat pump achieves a significant enhancement in heating season performance factor of 10.61 ∼ 30.37 % and the throttling irreversibility can be remarkably reduced with the exergy efficiency promoted by 12.76 ∼ 64.34 %. The life cycle cost is declined by 14.71 ∼ 22.38 % in contrast to BASE, and life cycle carbon emission reduces by 4.77 ∼ 22.12 %, indicating apparent advantage in environmental performance. The hybrid VI + DMS CO2 heat pump system is a promising solution to apply for clean space heating in the cold, very cold and subarctic zones.

Performance simulation of CO2 transcritical cooling system with mechanical subcooling cycle for automobile air conditioning

Performance simulation of CO2 transcritical cooling system with mechanical subcooling cycle for automobile air conditioning

Real-time energy-efficient operation of a dedicated mechanical subcooling based transcritical CO2 heat pump water heater via multi-input single-output extreme seeking control

In the field of transcritical CO2 systems applied research, dedicated mechanical subcooling (DMS) is one of the most recently investigated and promising solutions, especially for space heating. However, this kind of system brings with it an intrinsic complexity, and to pursue effective and efficient operation, it requires suitable control and optimization strategies. The paper considers a combined transcritical CO2 and R134a -based DMS system and depicts the benefits of using a Multi-Input-Single-Output (MIMO) Extremum Seeking Control (ESC) approach. The real-time optimization strategy was obtained through a Computer-Aided Control System Design (CACSD) tool, exploiting an ad hoc Dymola model of the DMS system that has been validated and tested by using experimental data. The performance of the proposed approach has been compared with standard solutions relying on physical correlations. The MISO-ESC strategy always performed better in terms of system Coefficient of Performance (COP), under both fixed and variable ambient temperature conditions. Finally, the influence of the different refrigerants in the combined DMS system was analyzed from both heating capacity and performance points of view.

Experimental evaluation of a transcritical CO[formula omitted] refrigeration facility working with an internal heat exchanger and a thermoelectric subcooler: Performance assessment and comparative

The use of carbon dioxide in transcritical state has become one of the most used solutions to comply with the F-Gas directive and reduce greenhouse gases emissions from refrigeration systems at high ambient temperatures. For low-medium power units, the commonly used solutions to improve the efficiency such as the ejector, multiple compressor arrangements, mechanical subcooler, etc., add complexity and increase the cost of the refrigeration facility, which is not ideal for small units. In this low-medium power range, two technologies stand out to increase the performance of a carbon dioxide transcritical cycle: the internal heat exchanger and the thermoelectric subcooler. This study brings a complete research in which both solutions have been tested in the same experimental transcritical carbon dioxide refrigeration facility under the same working conditions. It focuses on the real performance of both systems and discusses the strengths and weaknesses of using an internal heat exchanger or a thermoelectric subcooler. The results show that the thermoelectric subcooler outperforms the internal heat exchanger in both the coefficient of performance and the cooling capacity while also being a more controllable and flexible solution.

An idea to efficiently recover the waste heat of Data Centers by constructing an integrated system with carbon dioxide heat pump, mechanical subcooling cycle and lithium bromide-water absorption refrigeration cycle

As a perennial stable heat source, Data Centers release a continuous increasing amount of waste heat. Besides rejecting it into atmosphere by traditional refrigeration ways, how to effectively utilize the waste heat is still an open question. Thus, an idea is proposed to integrate carbon dioxide heat pump with mechanical subcooling cycle and lithium bromide-water absorption refrigeration cycle for the waste heat recovery of Data Centers. The carbon dioxide heat pump is firstly used for upgrading the low-temperature heat of Data Centers, and then the hot water from heat pump is employed to supply heat in winter, drive lithium bromide-water absorption refrigeration cycle in summer for surrounding office buildings. The main function of mechanical subcooling cycle is to increase the cooling capacity of carbon dioxide heat pump, and decrease the required mass flow of carbon dioxide in the Data Centers cooling. For this integrated system, energy, exergy and economic models are respectively established with the help of MATLAB and REFPROP 10 to obtain the corresponding performance. Eight high-temperature mixtures, namely R600a/R601a, R600a/R134a, R600a/R1234yf, R600a/R152a, R600a/R1233zd, R600a /R1234ze and R600a/R236ea, are considered in the mechanical subcooling cycle. The obtained results indicate that the optimum mixture is R600a/R601a (0.4/0.6) with the highest coefficient of performance 2.12 under the discussed conditions, but R600a/R134a (0.5/0.5) with coefficient of performance 2.01 is more recommended out of security. On this basis, exergy destruction and economic analysis are conducted for the use of R134a, R600a and R600a/R134a (0.5/0.5) in mechanical subcooling cycle. Compared with pure fluids R600a and R134a, the exergy destruction of mixture R600a/R134a (0.5/0.5) could be reduced by 593.1 kW ∼ 1114 kW. Besides, the required heat exchanging area of condenser could be diminished by 19.20%∼23.16%. As for the economy, the cost of lithium bromide-water absorption refrigeration unit takes up over the half of the integrated system cost. For different working fluids in mechanical subcooling cycle, the payback period of developed system ranges from 2.04 to 2.46 years.

Thermodynamic study of carbon dioxide transcritical refrigeration cycle with dedicated subcooling and cascade recooling

Stimulated by the fast development of cold chain commodity market and a large amount of demand in cold storages, the application of CO2 refrigeration system is to enhance remarkably. Owing to the low critical temperature of CO2, the dedicated subcooling technology is widely-used in the CO2 transcritical refrigeration cycle to increase the system performance. In this regard, reducing the compressor power of subcooling subcycle and extending the working range of heat source temperature is highly important for the mechanical subcooling technology and absorption one, respectively. Motivated by such purpose, the CO2 transcritical cycle with dedicated subcooling and cascade recooling is presented and the thorough investigation is performed thermodynamically. The proposed system is compared with layouts with dedicated mechanical subcooling and dedicated absorption one at first. Subsequently, the effect of recooling capacity ratio, the critical parameter for the system performance, is analyzed in-depth. Finally, the optimum recooling capacity ratio for different conditions is fitted by the neural network approach. Compared to layouts with dedicated mechanical subcooling and dedicated absorption one, the secondary compressor work goes down by 28.5% and the lower limit of heat source temperature is extended by 4 °C, respectively in the proposed system. The paper is favorable for the development and performance improvement of CO2 transcritical refrigeration systems.

Experimental assessment of different extraction points for the integrated mechanical subcooling system of a CO2 transcritical plant

Subcooling systems are positioned in recent years as one of the best solutions to improve the efficiency of transcritical CO2 cycles. Specifically, the integrated mechanical subcooling cycle allows the improvement of these systems only using CO2 as a refrigerant. This integrated cycle can be designed with three different architectures: extracting the CO2 from the gas-cooler outlet, from the subcooler outlet or from the liquid tank. In this work, the three configurations are experimentally analysed and the main differences between them are studied. An experimental plant has been tested at three heat rejection levels (25.0, 30.4 and 35.1 °C) and a fixed temperature of the secondary fluid at the evaporator inlet of 3.8 °C. The results show that from an energy efficiency point of view, all the configurations have practically the same COP, with certain variations in the cooling capacity and the greatest differences in the cycles are found in the subcooler.