Method of simulating the performance of a co 2 refrigeration system

Abstract

This disclosure relates to a simulation method for choosing the best system configuration for a CO2 refrigeration system. In particular, the disclosure refers to a simulation method capable of defining the influence of operating parameters of a CO2 refrigeration system. This method takes into account the climatic profile of the installation site of the system. The disclosure also relates to a method of designing and constructing a CO2 refrigeration system comprising the aforementioned simulation method.

Description

[0001] TITLE: METHOD OF SIMULATING THE PERFORMANCE OF A CO2REFRIGERATION SYSTEM DESCRIPTION

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] This disclosure relates to a simulation method for choosing the best system configuration for a CO2 refrigeration system. In particular, the disclosure refers to a simulation method capable of defining the influence of operating parameters of a CO2 refrigeration system. This method takes into account the climatic profile of the installation site of the system. The disclosure also relates to a method of designing and constructing a CO2 refrigeration system comprising the aforementioned simulation method.

[0004] PRIOR ART

[0005]

[0002] A refrigeration system consists of a set of equipment that functions to lower the temperature of a confined space or a production or industrial process.

[0006]

[0003] From a thermodynamic perspective, the integration of the different equipment occurs according to a refrigeration cycle based on the successive evaporation, compression, condensation, and expansion of a refrigerant fluid. Through this process, heat is transferred from the confined space or the process to be cooled to an environment at a higher temperature capable of absorbing it.

[0007]

[0004] The environment where the heat generated by a refrigeration system is dissipated is generally the ambient air. This heat exchange process is achieved using ventilated units, that is, heat exchangers equipped with a fan necessary to increase heat transfer to the external environment.

[0008]

[0005] Regardless of the final application (e.g., industrial or commercial), there is a strong need today to reduce both energy consumption and emissions of gases harmful to the environment that are used by refrigeration systems. Therefore, in this sector too, there is increasing attention to the development of technologies that allow significant energy savings and the use of environmentally friendly refrigerant gases.

[0009]

[0006] In recent years, due to its very low environmental impact and excellent thermodynamic properties, the use of carbon dioxide (CO2) as a refrigerant fluid has received particular attention.

[0010]

[0007] However, the use of CO2 as a refrigerant fluid within a refrigeration system presents designers with some technical challenges, such as the heat dissipation performed by the ventilated units when the external ambient temperature is above 31 °C. Under these conditions, the pressure of the CO2 refrigerant gas rises rapidly to values exceeding 100 bar. The operating modes of the system that thus arise are known in the art as transcritical, distinguishing their behavior from the subcritical mode (i.e., when the ambient temperature is below 31 °C).

[0011]

[0008] In a ventilated unit operating in a CO2 refrigeration system in transcritical mode, the refrigerant fluid enters in a high-temperature gaseous phase (up to 115°C) and exits at temperatures close to the ambient temperature. Between the inlet and the outlet, the CO2 undergoes simple cooling. In this case, the ventilated unit employing CO2 in transcritical operation is called a gas cooler. In this mode, the operating pressure is above 73.7 bar and can even exceed 100 bar.

[0012]

[0009] Conversely, if the CO2 refrigeration system operates in subcritical mode (when the ambient temperature is below 31 °C), the ventilated unit is called a condenser. Inside it, the CO2 changes phase from gas to liquid. The operating pressure of a condenser is roughly between 45 bar and 73.7 bar.

[0013]

[0010] From a design, construction, and energy perspective, operating the system at high operating pressures (i.e., transcritical) can be particularly demanding. The consequences, in addition to being technical, can also become economic, determined by higher construction costs and excessive energy consumption during operation, lengthening the payback periods of the investment and making the economic viability of the intervention as a whole particularly critical.

[0014]

[0011] Nevertheless, interest in CO2 is growing, especially in applications such as commercial or industrial refrigeration. In this context, new systems are continually proposed with technical measures aimed at solving the efficiency problem under the aforementioned conditions.

[0015]

[0012] The evaluation of system solutions, the technologies to be used, and their sizing within a CO2 refrigeration system represent barriers that can limit the diffusion of these systems.

[0016]

[0013] A widely known and widespread technological-construction solution in the sector is the installation of an adiabatic system to support the ventilated units using CO2 as the refrigerant fluid. The advantage of this solution lies in the possibility of increasing the heat exchange of a ventilated unit by cooling the ambient temperature entering the ventilated unit (this physical phenomenon is also known as evaporative or adiabatic cooling). The amount of ambient temperature reduction can be calculated as: ATamb- Qadb X (Tdb—Twb) where Tdb in [°C] is the dry-bulb ambient temperature, TWb in [°C] is the wet-bulb ambient temperature, and qadb in [%] is the adiabatic saturation coefficient. The wetbulb temperature can be calculated from the dry-bulb temperature and the ambient relative humidity evaluated at the same time. The adiabatic saturation coefficient is a parameter that can be provided by the manufacturers of adiabatic systems.

[0017]

[0014] The amount of reduction in the inlet temperature to the ventilated unit is related to the environmental conditions defined by the ambient temperature and relative humidity. Generally, the reduction amount is maximal when the ambient temperature is high (e.g., Tdb>35°C) and the relative humidity is low (e.g., <20%). Conversely, the reduction amount will be zero when the relative humidity is maximal (100%).

[0018]

[0015] Typically, an adiabatic system is activated when the ambient temperature is above 18°C and when the relative humidity is below 65%.

[0019]

[0016] From a technological, constructive, functional, and system perspective, an adiabatic system represents a widely known and adopted solution in various application sectors such as refrigeration, air conditioning, air treatment units, or data centers. For this reason, further details will not be provided in this document.

[0020]

[0017] The strong dependence of the annual energy performance of an adiabatic system on environmental conditions requires the definition of appropriate control strategies and accurate system choices related to the final application.

[0021]

[0018] The adoption of an adiabatic system to support a ventilated unit that employs CO2 as a refrigerant fluid within a refrigeration system can help limit the negative effects of high temperatures on the system's operating pressures, making technical- economic alternatives that were previously disadvantageous and / or non-viable interesting.

[0022]

[0019] The development and consolidation of knowledge in this field would require experimental field tests that demand significant investments and long execution times. All this work obviously involves substantial economic expenditure.

[0023] SUMMARY OF THE INVENTION

[0024]

[0020] A technical problem underlying the present disclosure is therefore to provide a method for simulating and comparing different system configurations for refrigeration systems using CO2 as a refrigerant fluid. In particular, the method is capable of providing a valid tool for determining the operational and functional characteristics of a gas cooler and the working parameters for a given system configuration, thereby providing the designer with a valid tool for selecting the best system solution.

[0025]

[0021] The method is based on the evaluation of the annual energy performance of a system and takes into account the climatic characteristics of the installation site.

[0026]

[0022] A first object of the present disclosure is therefore a method of simulating the performance of a CO2 refrigeration system comprising data processing phases specifically selected to simulate the different operating conditions of a gas cooler over the course of a year.

[0027]

[0023] A second object is a method of simulating a CO2 refrigeration system in which the processing phases include the evaluation of temperature trends in a specific geographical area.

[0028]

[0024] A third object is the aforementioned simulation method in which the phases include the evaluation of adiabatic systems supporting a gas cooler.

[0029]

[0025] Another object is a method of designing a CO2 refrigeration system comprising the use of an electronic computer in which a program developed to perform the aforementioned phases of the simulation method is loaded and run.

[0030]

[0026] Yet another object is a CO2 refrigeration system comprising components designed based on the aforementioned simulation method.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032]

[0027] Further characteristics and advantages of the simulation method for a CO2 refrigeration system of the present disclosure will become more evident from the following description of some exemplary, non-limiting embodiments with reference to the following figures:

[0033] - FIG. 1 represents a general schematic of a CO2 refrigeration system;

[0034] - FIGS. 2A and 2B respectively represent a refrigeration diagram of carbon dioxide in transcritical and subcritical cycles;

[0035] - FIG. 3 represents a diagram of the hourly temperature distribution recorded over a year in Madrid;

[0036] - FIG. 4 represents a diagram of the statistical temperature distribution of FIG. 3 according to the present disclosure;

[0037] - FIG. 5 represents a diagram of the water consumption in [m3] of an adiabatic system varying with the limit operating conditions defined by ambient temperature and relative humidity; - FIG. 6 represents a diagram of the annual energy consumption reduction of a CO2 refrigeration system employing an adiabatic gas cooler compared to a system operating under the same environmental conditions; the reduction in consumption is quantified in terms of percentage reduction and varies with the limit operating conditions defined by ambient temperature and relative humidity.

[0038] DETAILED DESCRIPTION OF THE DRAWINGS

[0039]

[0028] With reference to FIG. 1 , the refrigeration systems 1 based on a refrigeration cycle comprise a compressor 2A and a related support compressor 2B, placed in parallel, heat dissipation units 3, a high-pressure valve 4, a liquid / gas receiver 5, and one or more evaporators 6 with their respective auxiliary devices (not shown) known in the field. Despite the technical-systemic problems described earlier, the use of CO2 is very interesting due to its negligible environmental pollution and good energy efficiency. In principle, a refrigeration cycle using CO2 as a refrigerant fluid involves its evaporation (in the form of gas at low pressure between 10 and 35 bar) and its condensation or cooling depending on whether the process is transcritical or subcritical, respectively, as exemplified in FIGS. 2A and 2B.

[0040]

[0029] In particular, in the system 1 , the CO2 refrigerant fluid undergoes compression in the compressor 2A and is then forced into the ventilated unit 3 for heat dissipation into the environment. Subsequently, the cooled fluid passes through the high-pressure or expansion valve 4 where it expands with consequent further cooling and is finally collected in a liquid receiver in the form of a liquid / gas tank 5. From this tank, the fluid reaches the evaporator 6 where it exchanges heat again with a warm environment to cool the environment itself by absorbing heat from it. The cycle concludes with the return of the fluid that has absorbed heat from the evaporator to the compressor 2A, where it undergoes a new compression cycle.

[0041]

[0030] The aforementioned general schematic of a refrigeration system can then be implemented with numerous devices placed in parallel or series with the refrigeration circuit. For example, subcooling elements (also known as subcoolers) can be provided downstream of the gas cooler, especially when it is of the adiabatic type. Additional compressors can be placed in parallel with the main compressor or in series with the main compressor and upstream of the evaporator. In any case, the combination of elements in a refrigeration system mainly depends on its intended use, whether for large industrial environments, large or small commercial environments, or domestic environments. The complexity of the system layout, the mass flow rate, and the installed thermal power of such systems must therefore be evaluated and designed each time considering the operating environment.

[0042]

[0031] It is therefore clear that the executive and detailed design of a refrigeration system involves the evaluation of numerous constructive and functional parameters for each component.

[0043]

[0032] With reference to the component of a gas cooler installed in a CO2 refrigeration system according to the present disclosure, the constructive parameters depend on the layout of the system to be designed. In particular, the layouts provided for a CO2 gas cooler system are defined by the combination of different technologies or solutions typically used in these systems, such as gas cooler, adiabatic gas cooler, adiabatic subcooler, mechanical subcooler, ejector, or parallel compressor. These technologies or solutions are well known to those skilled in the refrigeration field and will not be further elaborated here.

[0044]

[0033] The parameters necessary to characterize the operation of the refrigeration system through the simulation according to the present disclosure are preferably:

[0045] - Cooling capacity, evaporation temperature, and desuperheating of the evaporator(s);

[0046] - Desired CO2 temperature at the exit of the ventilated unit (for both condenser and gas cooler operating modes);

[0047] - Operating limits of the adiabatic system (defined by dry-bulb temperatures and relative humidity).

[0048]

[0034] The method of simulating the performance of a gas cooler for a CO2 refrigeration system according to the present present disclosure, using the aforementioned system parameters, allows the definition of a series of performance indicators to quantify the annual performance of the entire system. In particular, these performance indicators belong to two categories:

[0049] - they can be specific and relate to the heat dissipation technology chosen by the designer, namely: o maximum thermal capacity dissipated; o maximum electrical absorption; o maximum inlet pressure and temperature; o thermal energy dissipated and electrical energy consumed; o operating hours of the adiabatic system, if any, and related water consumption;

[0050] - they can be general and related to the entire system, namely: o maximum electrical absorption; o electrical energy consumed; o average annual coefficient of performance (COP).

[0051]

[0035] The design method thus includes a series of phases in which technical data derived from the components used in refrigeration systems is considered and processed. This data is processed by an electronic computer using a program specifically designed to predict the best operating parameters in a pre-selected system.

[0052]

[0036] Specifically, the simulation program for a gas cooler for a CO2 refrigeration system according to the present present disclosure has been designed to implement a method comprising the following phases:

[0053] - selecting a reference CO2 refrigeration system layout;

[0054] - selecting an alternative CO2 refrigeration system layout;

[0055] - defining a set of operating parameters for said layouts;

[0056] - selecting a geographical location associated with an average annual climatic profile;

[0057] - calculating the annual statistical distribution of temperature and relative humidity of said location;

[0058] - calculating the activation time of an adiabatic system based on the operating conditions defined by the designer;

[0059] - calculating the instant performance of the system under specific operating conditions defined by the statistical analysis of the climatic data of the location;

[0060] - calculating the annual energy performance of the two system layouts using the bin method;

[0061] - comparing the calculation results by comparing the respective performance indicators between the reference and alternative systems;

[0062] - identifying the better system between the reference and the alternative.

[0063]

[0037] Once the system that provided the best performance indicators has been identified, it is possible to define and choose the specific characteristics of the gas cooler suggested by the aforementioned method. Subsequently, the designer can proceed to develop all the other conditions necessary for the proper functioning of the system to allow the realization of the refrigeration system by assembling and connecting all the components of the chosen system, particularly the gas cooler designed according to the aforementioned method.

[0064]

[0038] In particular, the phase of selecting a reference CO2 refrigeration system layout and its alternative fundamentally depends on the intended use of the system, whether industrial, commercial, or domestic. In turn, the system depends on the size of the environment in which it is to be placed and the type of cooling to be used, whether to cool / condition a room or one or more refrigeration units.

[0065]

[0039] In any case, according to the present disclosure, the reference system layout and its alternative can be chosen, by way of example, from those listed earlier. It should be noted that these structures include many components such as those exemplified earlier with reference to FIG. 1 . Additionally, each piece of equipment and component of the system layout is well known in the field and will not be further described here.

[0066]

[0040] Once the system layout has been selected, the corresponding operating parameters to be considered for verifying performance under certain conditions are selected. These parameters are preferably those described previously. It should be noted that some parameters are to be considered for any structure, while others are to be considered only for certain specific structures because the components themselves dictate it.

[0067]

[0041] The phase of selecting a geographical location aims to define the operating conditions of the heat dissipation system. These operating conditions are derived from an average annual climatic profile, which can be obtained from online databases, industry technical standards, or field surveys (see, for example, the graph in FIG. 3 related to the temperature trend over a year in Madrid). In the case of a gas cooler / condenser operating with CO2 as the refrigerant fluid, the temperature and relative humidity of the installation site are particularly relevant. Given the dependence of the components' behavior and the annual performance of the system on environmental conditions, this aspect plays a significant role in the design method.

[0068]

[0042] The operating conditions of the system must be defined in the form of a statistical frequency distribution of temperature and relative humidity for that location. In general, the chosen frequency of the climatic data (e.g., ambient temperature, as shown in the graph in FIG. 4) can be very narrow (e.g., 0.05 K) or broader (e.g., 5 K), but this does not affect the overall validity of the design method.

[0043] The desired CO2 temperature at the outlet of the ventilated unit, Tcc.out, is defined relative to the external air temperature, i.e., by defining the approach temperature. This parameter is calculated as the temperature difference between the desired CO2 temperature at the outlet of the gas cooler / condenser and the ambient temperature. This temperature difference is always greater than zero to enable heat dissipation to the external environment.

[0069]

[0044] In the design practice of a heat dissipation system, the approach temperature is predefined by the designer. With the same power to be dissipated by the gas cooler / condenser and other environmental conditions, designing a gas cooler with a relatively low approach temperature (e.g., 1 K) requires constructing a much larger and thus more expensive ventilated unit compared to designing the same gas cooler with a higher approach temperature (e.g., 3 K). The relationship between the approach temperature and the investment (including the design effort and the supply of the ventilated unit) is not linear but follows an exponentially increasing trend.

[0070]

[0045] In the performance calculation phase, the rotational speed of the fans of the ventilated unit of the gas cooler / condenser is considered. Indeed, this speed can be varied based on the operating conditions of the gas cooler, i.e., according to the environmental operating conditions. This strategy is commonly employed in the design and implementation phases and has significant benefits in terms of energy efficiency. For example, the higher the ambient temperature, the higher the rotational speed must be to facilitate heat dissipation from the gas cooler / condenser.

[0071]

[0046] Following the compression work of the compressor, the CO2 simultaneously undergoes an increase in its pressure and temperature. The operating performance of compressors can be derived from manufacturers' catalogs or industry standards.

[0072]

[0047] Upon exiting the compressor, the CO2 is directed into the ventilated unit. While the temperature between the inlet and outlet of the gas cooler / condenser decreases due to the heat dissipation process, the pressure of the CO2 remains roughly constant, net of the circuit's pressure losses. The operating pressure of the gas cooler / condenser is regulated by a high-pressure control valve located downstream of the gas cooler / condenser. The pressure can range between 45 and 130 bar, depending on environmental conditions. In practice, for example, the higher the ambient temperature, the higher the operating pressure.

[0073]

[0048] It has been demonstrated in industry literature that optimizing the operating pressure of the gas cooler / condenser can significantly impact the energy performance of the system. The software underlying the method of the present disclosure implements empirical relationships linking the operating pressure (pcc.opt in [bar]) to the outlet temperature of the gas cooler / condenser Tcc.out in [°C], depending on the operating mode (subcritical, transcritical) and the system solution considered. These relationships have the following form:

[0074] Pcc.opt = (A x Tcc.out - B) [bar] where A and B are predefined empirical coefficients for each system configuration. These coefficients can be obtained from industry literature or calculated by varying the operating pressure to maximize the annual coefficient of performance (COP) of the system.

[0075]

[0049] Upon exiting the high-pressure valve, the CO2 enters the liquid receiver 5, which consists of a tank maintained at a predefined and controlled pressure. Inside it, the CO2 can be present in both liquid and gaseous phases. From the liquid receiver, the CO2 can be:

[0076] - distributed to medium and low-temperature evaporators with a flow rate controlled by conventional electronic expansion valves;

[0077] - distributed to the compressor suction.

[0078]

[0050] In a real installation, the operating pressure inside the liquid receiver 5 is regulated by a bypass valve positioned between the liquid receiver itself and the compressor suction. The pressure value is defined by the designer and regulated by the control logic provided by the manufacturers of control and regulation systems.

[0079]

[0051] In general, a mass and energy balance (the first law of thermodynamics) can be imposed on each system component. Applying these balances to the liquid receiver 5, for example, represented in the system configuration in FIG. 1 , the following emerges:

[0080] - From the mass balance, it is understood that the CO2 flow rate entering the liquid receiver (min) equals the sum of the flow rates exiting it, destined for the evaporators (mout ,evap1 , fTlout.evaP2) and the compressor (mOut, flash) min=rriout.evapi + rriout,evap2 +rriout, flash mass balance

[0081] - From the energy balance, the energy associated with the incoming flows must equal that of the outgoing flows. In addition to the outgoing flows defined previously (towards the evaporators and the compressor), thermal losses can also be considered.

[0082]

[0052] From solving the two balances defined previously for the liquid receiver 5, it is possible to define the inlet conditions to the evaporators 6 in terms of flow rate and temperature. From these, the outlet conditions from the evaporators 6 can be calculated considering the input parameters defined in paragraphs 32 or 33.

[0083]

[0053] Based on the system configuration in FIG. 1 , the CO2 is drawn into the compressors at the outlet of the evaporators 6.

[0084]

[0054] The thermodynamic cycle defined from paragraph 28 is repeated iteratively for each bin.

[0085]

[0055] The phase of calculating annual performance particularly comprises the following steps:

[0086] - Calculating the performance of the refrigeration system under a specific operating condition defined by the j-th ambient condition defined by the previous statistical analysis. Specifically, the electrical power absorbed in [W] by the system Weij is calculated as the sum of the individual contributions from the different system components (gas cooler, subcooler, compressors, and evaporators):

[0087] Weij=Wel,GC,j + Wei, SC, j + Wei, comp, j + Wel.evapj

[0088] - Calculating the electrical energy absorbed by the system Eeij in [kWh] as the product of the electrical power absorbed Wei in [W] and the duration of the j-th ambient condition defined by the previous statistical analysis hj in [h]:

[0089] Eel,j=Wei X hj

[0090] - Calculating the annual electrical energy absorbed by the system in [kWh] as the sum of the contributions:

[0091] Eel=£j (Eelj)

[0092]

[0056] From the calculated annual electrical energy, it is possible to derive performance indicators to compare different system solutions under the same operating conditions.

[0093]

[0057] In addition to electrical energy consumption, it is possible to calculate the operating conditions of the various system components, such as the temperatures and pressures at the gas cooler / condenser inlet or water consumption by the adiabatic system.

[0094]

[0058] The method of the present disclosure thus provides the designer with energy and operational evaluation elements to compare the performance of alternative system solutions.

[0095]

[0059] For example, with reference to FIG. 5, the diagram shows the annual water consumption in [m3] of an adiabatic system depending on the ambient temperature [°C] and relative humidity [%]. From this diagram, the designer can choose the desired conditions for the system based on environmental conditions. Indeed, the water consumption values of the adiabatic system vary depending on temperature and relative humidity.

[0096]

[0060] Similarly, with reference to FIG. 6, the diagram shows the reduction in annual energy consumption of a CO2 refrigeration system employing an adiabatic gas cooler compared to a system operating under the same environmental conditions. Here, too, it can be seen that the ambient temperature and relative humidity differently influence the reduction in consumption. Therefore, the designer, based on the environmental conditions where the system is to be designed, can choose the best parameters for the system components.

[0097]

[0061] The trends of the two indicators in FIGS. 5 and 6 are opposite in nature. The problem of defining the control strategy of an adiabatic system is mathematically an optimization problem, in which the "optimal" combination of the effects of two design parameters is sought. From a design perspective, the designer, knowing the cost of electricity and water, can decide on the best operating point of the adiabatic system. This is one of the problems that only a tool like the one in this present disclosure can solve.

[0098]

[0062] According to a variant of the present disclosure, the method can include the simulation of an evaporative subcooler or a dedicated mechanical subcooler to be associated upstream of the gas cooler. For each of these additional devices, the method includes further calculation phases similar to those described in the aforementioned paragraphs regarding the gas cooler / condenser.

[0099]

[0063] A second object of the present disclosure is a method for designing a CO2 refrigeration system comprising a computer program to implement said method. In particular, the computer program is loaded onto any computer, such as a personal computer, to carry out the aforementioned phases.

[0100]

[0064] Another object of the present disclosure is a refrigeration system for civil, commercial, or industrial environments that operates with a CO2 system, comprising a compressor 2A and, if necessary, a backup compressor 2B placed in parallel, a condenser 3 (gas cooler), a high-pressure valve 4, a liquid receiver 5, and one or more evaporators 6, where these components are designed according to the previously described method.

[0065] Yet another object is a method for constructing a CO2 refrigeration system, comprising a phase of assembling system components, where these components are built according to the previously described design method.

[0101]

[0066] From what has been described so far, the method of simulating a CO2 system according to the present disclosure clearly solves the technical problems described earlier with reference to known methods and brings significant advantages.

[0102]

[0067] First of all, complicated, long, and expensive tests are no longer necessary to determine which gas cooler is most suitable for a particular cooling system in a specific geographical area. Indeed, thanks to the aforementioned method, it is possible to provide a simulation tool that can a priori determine the best technical / functional characteristics to build the gas cooler with the best performance.

[0103]

[0068] Additionally, the method has been developed with calculation phases specifically designed to simplify numerous steps that might be necessary to define all the design variables of a gas cooler considering different applications; on the other hand, a way has been found to select sufficient and exhaustive data to obtain a precise and reliable result.

[0104]

[0069] In other words, the method allows, with a limited amount of data and calculations, to accelerate the definition of the technical characteristics of a gas cooler, considering the best performance conditioned primarily by climatic variations in the geographical area where it is to be installed.

[0105]

[0070] Numerous variations of the gas cooler simulation method in a CO2 cooling system according to the present disclosure can be developed by a skilled technician in the field without departing from the scope of protection defined by the attached claims.

Claims

CLAIMS1. Method of simulating a CO2 refrigeration system, comprising the steps of:- selecting a reference CO2 refrigeration system layout;- selecting an alternative CO2 refrigeration system layout;- defining a set of operating parameters for said layouts;- selecting a geographical location associated with an average annual climatic profile;- calculating the annual statistical distribution of temperature and relative humidity of said location;- calculating the activation time of an adiabatic system based on the operating conditions defined by the designer;- calculating the instant performance of the system under specific operating conditions defined by the statistical analysis of the climatic data of the location;- calculating the annual energy performance of the two system layouts using the bin method;- comparing the calculation results by comparing the respective performance indicators between the reference and alternative systems;- identifying the better system between the reference and the alternative.

2. Method according to claim 1 , wherein the steps of selecting the reference and alternative system layouts are carried out by combining multiple components chosen from gas cooler, adiabatic gas cooler, adiabatic subcooler, mechanical subcooler, ejector, or parallel compressor.

3. Method according to claim 1 or 2, wherein the operating parameters of the components of said layouts are chosen from:- Cooling capacity, evaporation temperature, and desuperheating of the evaporator(s);- Desired CO2 temperature at the exit of the ventilated unit, for both condenser and gas cooler operating modes;- Operating limits of the adiabatic system, defined by dry-bulb temperatures and relative humidity.

4. Method according to any of claims 1 to 3, wherein the step of selecting the geographical location including average annual climatic profiles is carried out by querying databases, technical standards, or field surveys.

5. Method according to any of claims 1 to 4, wherein the step of calculating the annual distribution of temperature and relative humidity of said location is carried out considering a data sampling frequency.

6. Method according to any of claims 1 to 5, wherein the step of calculating the activation time of an adiabatic system is carried out based on the approach temperature as the temperature difference between the desired CO2 temperature at the exit of a gas cooler / condenser and the ambient temperature.

7. Method according to any of claims 1 to 6, wherein the step of calculating the annual energy performance of the two system layouts is carried out through the following steps:- Calculating the performance of the refrigeration system under a specific operating condition defined by the j-th ambient condition defined by said statistical analysis, such as the electrical power absorbed in [W] by the system Wei as the sum of the individual contributions from the various system components:Weij=Wel,GC,j + Wei, SC, j + Wei, comp, j + Wel.evapj- Calculating the electrical energy absorbed by the system Eeij in [kWh] as the product of the electrical power absorbed Wei in [W] and the duration in time of the j-th ambient condition defined by the previous statistical analysis hj in [h]: Eel,j=Wei X hj- Calculating the annual electrical energy absorbed by the system in [kWh] as the sum of the contributions:Eel=£j (Eelj).

8. Method of designing a gas cooler for a CO2 refrigeration system comprising a computer program to implement the method according to any of claims 1 to 7.

9. Method of constructing a CO2 refrigeration system (1 ), comprising a step of assembling a gas cooler (3) upstream of at least one compressor (2A) and downstream of a high-pressure valve (4), wherein each component of the system is constructed according to the method of any of claims 1 to 7.

10. Refrigeration system (1 ) for civil, commercial, or industrial environments that operates with a CO2 system, comprising a compressor (2A) and, if necessary, a backup compressor (2B), placed in parallel, a condenser (3), a high-pressure valve (4), a liquid receiver (5), and one or more evaporators (6), wherein each component is simulated according to the method of any of claims 1 to 7.

Images