Values Of Mass Flow Rate Research Articles

Bi-Level Operation Optimization and Performance Analysis for a Distributed Energy System with Energy Network

The increasing energy crisis and environmental problems promote the development of distributed energy systems (DESs) that utilize combined heat and power technology, renewable energy technology, and waste heat recovery technology to meet various load requirements. Although there is existing work and research on a variety of DESs, most previous studies tend to focus on energy production with little consideration of a distributed energy network and its energy loss, which results in large errors in energy-efficiency calculations and performance analyses. In this paper, a new DES model is proposed with full consideration of an energy network and the full use of solar energy, terrestrial heat, and exhaust gases. At the same time, an effective bi-level optimization method is also proposed for the daily operation of the DES in order to improve the system performance and benefits in the energy, the economy, and the environment. Specifically, the co-generation energy station and water heating network in the DES are optimized separately with two different optimization models. The first-level optimization model is used to seek the optimal values of water mass flow rate and water temperature of the water heating network, and the second-level optimization model is built to determine the optimal energy purchasing strategy and the optimal energy outputs of the co-generation energy station. In order to verify the advantages and effectiveness of the proposed system and method, a contrastive simulation study is undertaken to provide a comparison of the global optimization method. Simulation results show that energy loss, energy cost, and energy consumption of the DES using the bi-level optimization operation strategy only account for 22.51%, 33.42%, and 51.31% of the quantities of the global optimization method, respectively. The hourly curves of the optimal operating variables also demonstrate that the proposed bi-level optimization method can improve the operating stability of the DES better than the global optimization method.

Twist Angle Error Statistical Analysis and Uncertain Influence on Aerodynamic Performance of Three-Dimensional Compressor Rotor

Twist angle errors along the blade radial direction are uncertain and affected by cutting force, tool wear, and other factors. In this paper, the measured twist angle errors of 13 sections of 72 rotor blades were innovatively analyzed to obtain the rational statistical distribution. It is surprisingly found that the under-deflection systematic deviation of twist angle errors shows a gradually increasing W-shaped distribution along the radial direction, while the scatter is nearly linear. Logically, the statistical model is established based on the linear correlation of the scatter by regression analysis to reduce variable dimension from 13 to 1. The influence of the radial non-uniform twist angle errors’ uncertainty on the aerodynamic performance of the three-dimensional compressor rotor is efficiently quantified combining the non-intrusive polynomial chaos method. The results show that the mean values of mass flow rate, total pressure ratio, and isentropic efficiency at the typical operating conditions are lower than the nominal values due to the systematic deviation, indicating that the under-deflection twist angle errors lead to the decrease in compressor thrust. The compressor’s stable operating range is more sensitive to the scatter of twist angle errors, which is up to an order of magnitude greater than that of the total pressure ratio and isentropic efficiency, indicating the compressor’s safe and stable operation risk increases. Additionally, the flow field at the tip region is significantly affected by twist angle errors, especially at the shock wave position of the near-stall condition.

Utilization of vortex flow pattern in the design of an efficient solar air heater

In this work, numerical and experimental analyses of a new model of circular solar air heater are carried out to examine the effect of employing vortex flow inside the air vessel of collector for convection enhancement. In three-dimensional numerical CFD-based analysis, the COMSOL Multi-physics is used to solve the flow equations for the turbulent forced convection airflow and conduction equation for the solid parts of the solar heater at different air mass flow rates in the range of 0.003 to 0.012 kg/s. In the calculation of turbulent stresses and heat fluxes, the RNG κ-∊ turbulence model is employed. The surface to surfaces (S2S) radiation model is used to consider the radiations emitted by the hot surfaces in collaboration with the energy equation. For validation, the theoretical findings are evaluated against the experiment. For the studied test cases with different values of solar irradiation and air mass flow rate, thermal efficiencies of up to 80 % are found. In comparison to the conventional rectangular-shaped solar air heaters with smooth ducts, more than 100 % increase in the value of thermal efficiency is delineated from the theoretical and experimental findings. This gain is attributed to the unique flow pattern in the developed solar collector.

Exergy performance analysis of hydrogen recirculation ejectors exhibiting phase change behaviour in PEMFC applications

A comprehensive analysis of flow behavior and exergy performance was conducted in hydrogen recirculation ejector, taking into account the phase change of humid hydrogen for proton exchange membrane fuel cell (PEMFC) systems. A two-phase nonequilibrium condensation CFD model integrating the entropy transport equations was established. The effect of phase change on ejectors’ performance under various primary pressure, secondary pressure and temperature, and back pressure were analyzed. When primary pressure was adjusted into 3.0 bar, a liquid fraction of 4.56 % was observed at the outlet, while the liquid fraction will increase to 15.35 % when the inlet pressure got to 5.0 bar. Then, the values of mass flow rate and liquid mass fraction on different sections under variable secondary temperature and back pressure were calculated. Finally, it is found that a larger primary pressure brought an increase in exergy destruction. So was exergy destruction ratio. However, increasing secondary pressure leads to the opposite result. With the increase of secondary temperature from 60 to 80 °C, exergy destruction increases from 330.28 to 390.23 kJ/kg but the destruction ratio decreases from 29.85 % to 26.19 %.

APPLICATION OF AN EXACT SOLUTION OF SPECIAL TYPE OF THERMOSOLUTAL CONVECTION EQUATIONS FOR THE INVESTIGATION OF EVAPORATIVE THREE-DIMENSIONAL FLOWS

The characteristics of gas-liquid flows with evaporation at the thermocapillary interface in an infinite rectangular duct, with a linearly distributed thermal load being applied on the upper and lower walls, are studied. The theoretical research of the three-dimensional convective flows is carried out within the framework of a two-sided model of evaporative convection based on the Navier-Stokes equations in the Oberbeck-Boussinesq approximation. A solution of a special type of governing stationary equations is used for describing the heat and mass transfer in a system of two immiscible fluids. We investigate the influence of the working (equilibrium) temperature of the system and intensity of the external thermal load on the structure of the velocity and temperature fields, as well as on changes in the evaporation mass flow rate and vapor content in the gas phase. The simulations are performed for the ethanol-air system. Based on the comparison of the calculated and experimental data, an effective way of nondimensionalization is proposed that allows one to consistently take into account the impact of the gas pumping velocity being a controlled parameter in experiments. It provides correct matching of the mathematical model to the experiment conditions, as well as a better qualitative and quantitative agreement between theoretical and measured values of evaporative mass flow rate. The results of the present study can aid in developing a theoretical basis for experimental research methods of evaporative convection and also in designing equipment for thermal coating or drying.

Thermal response of an asphalt solar collector: Numerical and experimental validation

This study conducts a numerical analysis and experimental validation of the thermal performance of an asphalt solar collector. Both parallel and serpentine copper tubes with a total length of 3000 mm were embedded in the middle of a 1000 × 600 × 80 mm hot mix asphalt model. The sides and bottom of the test sections were insulated to prevent heat loss to the surrounding environment. Using four values of water mass flow rate and three values of artificial solar radiation, the thermal performance of the system was examined. A mass flow inlet of 0.0038–0.035 kg/s is specified for the water inside the embedded tubes, while 600, 800, and 1000 W/m2 solar radiation is applied on the upper section of the asphalt mix during this study. The thermal response was simulated using the COMSOL Multiphysics 5.6.0.280 heat transfer module. Using a reference asphalt solar collector, the desired parameter effects were investigated independently. The experimental results showed that the efficiencies of the asphalt solar collector with serpentine bare tubes and parallel bare tubes are 53.56 % and 52.85 %, respectively. The numerical simulation reveals that there is no significant thermal effect in the area under the embedded tubes when compared to the area above the tubes that are exposed to solar radiation from above. The average error found between the numerical and experimental results for the water temperature difference inside the embedded tubes of the asphalt solar collector ranged between 6 % and 14 %. This good agreement indicated that the computational fluid dynamics model is reliable and capable of simulating the thermal response of an asphalt solar collector.

Fast Calculation of Supercritical Carbon Dioxide Flow, Heat Transfer Performance, and Mass Flow Rate Matching Optimization of Printed Circuit Heat Exchangers Used as Recuperators

Printed circuit heat exchangers (PCHEs) are widely used as recuperators in the supercritical carbon dioxide (S-CO2) Brayton cycle design. The variation of heat sources will have a great impact on the heat transfer effect of the recuperator. It is of interest to study the fast calculation of flow and heat transfer performance of PCHEs under different operating conditions to obtain the optimal comprehensive performance and provide guidance for the operation control strategy analysis. Herein, a fast calculation method is established through a one-dimensional model of a PCHE based on Modelica. The effects of working medium mass flow rate and inlet temperature on the flow and heat transfer process are analyzed from the three aspects of heat transfer rate, flow pressure drop, and comprehensive performance, and the mass flow rate matching optimization is realized. The results show that increased mass flow rate increases heat transfer rate and flow pressure drop. The efficiency evaluation coefficient (EEC) has a maximum value at which the mass flow rate values of the cold and hot channels are best matched, and the comprehensive performance is optimal. When the mass flow rate of the heat channel is 4.8 g/s, the maximum EEC is 1.42, corresponding to the mass flow rate of the cold channel, 4.2 g/s. Compared with the design condition, the heat transfer rate increases by 62.1%, and the total pump power increases by 14.2%. When the cold channel inlet temperature increases, EEC decreases rapidly, whereas EEC increases when the hot channel inlet temperature increases. The conclusions can provide theoretical support for the design and operation of PCHEs.

Thermo-hydraulic efficiency enhancing: Optimized ladder fold baffle structure with cam and circle tube bundle

In this article, the design and thermo-hydraulic efficiency of a shell and tube heat exchanger (STHE) having ladder fold baffle equipped by two configurations with pore and without pore considering two types of tube bundles, cam and circular, are investigated numerically. Three-dimensional STHE is simulated employing the Solid Works Flow Simulation software. A numerical approach is performed for different values of mass flow rate from 0.5 to 2 kg/s, baffle height of 0, 20, and 40, and baffle pitch of 85.7, 60, and 46.15. STHE pressure drop, heat transfer, and efficiency evaluation coefficient (EEC) for different arrangements have been performed to study the STHE fluid flow and heat transfer. Obtained results for a ladder fold baffle and two studied types of tube bundles, cam, and circle, are provided, and thermo-hydraulic performance is compared with the current baffle structure. Based on the obtained results, an increase of 12.2% and 17.4% in pressure drop with increasing baffle height from 0 to 20 mm and from 20 to 40 mm was observed for circular tube bundles without pores, respectively. Related values for the case with pore are 14% and 14%. These values for the cam tube bundle are 12% and 15% without pores and 3% and 9% with pores. In addition, at an angle of 0, 20, and 40° in the case without pore, the EEC factor increased by 2.31%, 15.67%, and 15.47% compared to the case with pore for the cam tube bundle. The perforated ladder fold baffle showed the best performance with pitch and height of 85.7 mm and 40 mm, respectively.

Comparative Evaluation and Multi-Objective Optimization of Cold Plate Designed for the Lithium-Ion Battery Pack of an Electrical Pickup by Using Taguchi–Grey Relational Analysis

It is aimed to minimize carbon emissions and the spread of electric vehicles is supported for a more sustainable future. To increase the safety and life of these vehicles, cooling systems are added and developed to their energy storage systems. The aim of this study is to design and optimize the cooling plate for the lithium-ion battery pack used in a lightweight commercial electrical vehicle. Multi-objective optimization using Taguchi–grey relational analysis was performed by considering maximum temperature, the standard deviation of temperature, and pressure drop for the design of the cold plate. Channel number, channel height, and mass flow rate values were determined as parameters to be examined, and three different levels were selected for each parameter. Analysis was performed using water and 25% and 50% ethylene glycol–water solutions, which can work under sub-zero environmental conditions, employed as cooling fluid. It is shown that increasing the ethylene glycol ratio in the coolant allows it to work in colder environmental conditions, it is relatively worsening thermal performances in the cold plate applications. A new empirical correlation is proposed to predict the Nusselt number for the three coolants under all geometric and operating conditions considered in this study. Statistical analysis shows that the number of channels is the most effective parameter for the relatively low and homogenous temperature distribution on the cold plate surface. A sensitivity analysis was performed for Reynolds number ranges from 2500 to 15,000 using the optimum configurations of the three coolant fluids. It is shown that the same cooling effects could be obtained by using 1.56 times and 2.66 times more mass flow rates for 25% and 50% ethylene glycol–water solutions, respectively, compared to the water. However, rising mass flow rates result in a significant increase in the required pumping power.

Analysis of Heat Transfer and Efficiency of Rack Type Flash Dryer Machine in Purple Sweet Potato Drying Process

Purple sweet potato (Ipomoea batatas var Ayumurasaki) has deep purple flesh and tuber skin. The variety of processed purple sweet potato products is increasingly diverse as purple sweet potato production increases, such as cookies and chips. Therefore, a process is needed to turn purple sweet potato into flour before being made into a variety of processed products, namely the drying process. Drying is a process of reducing the water content of a material to a certain level. To determine how much fuel is used by dryer machine, it is necessary to evaluate the effectiveness of the machine. So that in this study the aims were to determine the amount of energy needed to dry purple sweet potatoes, calculate the efficiency of the flash dryer machine and find out the temperature distribution on each tray of the drying machine. Based on the research results of the rack-type flash dryer drying machine, it can be concluded that the mechanism of the heat transfer rate in the purple sweet potato drying process occurs by forced convection heat transfer from the drying air to the purple sweet potatoes and a mass flow rate value of 0.1272 kg/s is obtained, the convection transfer rate in the drying chamber is 836.84 W and the sensible heat value is 1033.84 W. Hence, the amount of heat to dry 3 kg of purple sweet potato for 4 hours is 1870.68 W and an efficiency value of 55.26% is obtained. The total energy required to dry 3 kg of purple sweet potato in 4 hours is 5712.86 kJ.

A numerical investigation of mathematical modelling in 3D hexagonal porous prism on oil recovery using nanoflooding

The use of nanomaterials as a means of recovering heavy and light oil from petroleum reservoirs has increased over the preceding twenty years. Most researchers have found that injecting a nanoparticle dispersion (nanofluids) has led to good results and increased the amount of oil that can be recovered. In this research, we aim to imitate the three-dimensional hexagonal prism in the existence of SiO2 and Al2O3 nanoparticles for better oil recovery. Porosity (0.1≤φ≤0.4), mass flow rate (0.05mL/min≤Q≤0.05ml/min), nanoparticle concentration (0.01≤ψ≤0.04), and the effect of relative permeability (kr) on oil and water saturation in the presence of gravity under different time durations are all investigated. The result obtained for the model is verified with existing experimental data. The results indicated that the infulence of nanoparticle volume fraction (VF) is significant in enhancing the oil recovery rate. It is also observed that at low porosity values the oil recovery is maximum. The maximum oil recovery is attained at low values of mass flow rate in the 3D hexagonal prism in the presence of silicon and aluminium nanoparticles It is also observed that the use of SiO2 gives a better oil recovery rate than Al2O3. It is also observed that maximum oil recovery is obtained at 99% at a flow rate of 0.05 mL/min in the presence of silicon injection.

Optimal Heat‐Up Planning of a Solid Oxide Fuel Cell with and without Hot Air Recycling by Considering Energy, Time, and Temperature Gradient

A solid oxide fuel cell (SOFC) needs to be heated to a high temperature to be able to start generating electricity. This study aims to manage the heat‐up process of a SOFC by considering the three objectives of time duration, energy consumption, and temperature gradient, simultaneously. Mass flow rate (MFR) and rate of temperature rise (RTR) of the hot air, passing through the cathode channel of the SOFC, are considered as decision variables. The transient heat‐up process is numerically simulated for six different MFR values (5–50 mg s−1) and six different RTR values (0.1–5 K s−1). The results indicate that higher RTR leads to lower heat‐up duration, lower energy consumption, but higher temperature gradient. Also, higher MFR results in lower heat‐up duration, lower temperature gradient, but higher energy consumption. The results also reveal that hot air recycling increases thermal efficiency from below 40% to nearly 100%. Finally, when hot air recycling is employed and all the objectives are considered simultaneously, the heat‐up plan with a RTR of 0.5 K s−1 and a MFR of 50 mg s−1 is selected as the best choice by using linear programming technique for multidimensional analysis of preference.

Dust produced by plasma off normal event in the vacuum vessel: Experimental analyses of the deposition inside the pressure suppression tank during a LOCA

This paper deals with experimental tests simulating the dust deposition, produced in the Vacuum Vessel of the nuclear fusion reactor ITER, and carried by steam and gases inside the Pressure Suppression Tanks during a Loss of Coolant Accident (LOCA). The dust, mainly tungsten and beryllium, is produced by the erosion of the divertor or of the first wall due to plasma off-normal events, like plasma disruptions or vertical displacement events. The activity is performed in the frame of a research program performed at the University of Pisa, funded by the ITER Organization, for studying the behaviour of the Vacuum Vessel Pressure Suppression System (VVPSS). A reduced scale of VVPSS was built at the University of Pisa (1/32 geometrical scale). The experimental rig is composed by an electric steam generator and steam and air mass flow rate control lines. Steam with (or without) air is sent in a condensation container, partially filled with water. These fluids entrain a mass of dust measured by a dust mini-dosing system. The air and the non-condensed steam flow in the atmosphere through a demister and HEPA filters. A tests campaign was carried out injecting a simulant of the actual dust (aluminium oxide) in a flux of steam and air into the condensation tank. The tests were performed at different values of steam, air and dust mass flow rate. During the test, the dust concentration in the water was measured versus time, in order to determine the settling time. The dust deposition on the surfaces of the condensation tank was measured as well as the decontamination efficiency of the tank. The results demonstrated that about 99 % of dust is deposited on the tank surfaces and only a quantity less than 1 % is carried by the water during the tank discharge.

Performance analysis of single‐pass solar air heater thermal collector with adding porous media and finned plate

AbstractThe recent study encompasses a practical inspect on adding porous material above absorber flat plate having fins to improve the effectiveness of solar air heater (SAH) collector along with forced air circulation process. The efficiency of the altered model and conventional SAH system is compared at the same time to display the impacts of adding porous material. The model that used porous material is called Model‐2, whereas the conventional SAH is called Model‐1. The measuring data is collected in January 2021 in Iraq (Mosul city). Outcomes emphasize that the effectiveness of altered model is better than traditional model by 7% for all air mass flow rates values. The highest efficiency is obtained equal 67% for Model‐2 and 60% for Model‐1 for mass flow rate 0.02 kg/s. For all mass flow rate values, a substantially change in temperature is observed in altered system as compared to traditional system, where the exhaust temperature of Model‐2 is higher than Model‐1. The improvement in the effectiveness of Model‐2 demonstrates that the employ of porous material has an extreme action on the heat exchange and subsequently heat transfer rate.

Optimization of a salt gradient solar pond for air heating application

In this study, it is demonstrated that when a solar pond is used for an air heating application like crop drying, domestic space heating, greenhouse heating etc., it is important to account for pumping power in the calculations. When air is the working fluid, the magnitudes of extraction and pumping power are comparable. Therefore, a new parameter is defined in context of solar ponds used for air heating, namely, effective power (defined as power extracted minus pumping power). At first, using a steady-state analysis, a closed form solution is derived for extraction power. The pertinent expression for pumping power is taken from the literature. Thus, an analytical expression for effective power is obtained and thereafter, an optimization analysis has been carried with the objective of maximizing this effective power. The analysis is used to calculate optimum values of air mass flow rate and pond’s non-convective zone thickness at which maximum effective power is registered. The corresponding maximum effective power and the associated air outlet temperature are also calculated. This work thus is believed to prove useful for designing of solar ponds that are used for air heating applications in a manner to ensure maximal system performance.

Experiments on waste hot water fed still operating with stirring turbulence

ABSTRACT The present work experimentally analyzes the performance of a novel waste hot water fed (WHWF) still for potable water production. In contrast to conventional solar stills, in this still hot water flows over the basin and the mass flow rate of water has been utilized to rotate four small alphabet S-shaped rotors provided at the basin. This rotation induces the stirring turbulence in hot water to enhance the evaporation rate. The non-dependency on solar energy provides the characteristic of continuous (both day and night) water production in all weathers. The variation in thermo-exergic and economic parameters has been studied for varying room temperature in the range of 22–30°C and mass flow rate of hot water in range 150–50 kg/h. The cumulative yield at 22°C is 8–21% and at water mass flow rate of 50 kg/h it is about 7–13% more in comparison of other considered room temperature and mass flow rate values. The improvement in exergy efficiency up to 45.7% is observed in the study. The average cost of potable water is Rs 0.92 (0.012 $) and average payback period is 0.9 year for the WHWF still.

A critical analysis of the AHRI polynomials for scroll compressor characterization

• Scroll compressor energy and mass flow surfaces with evaporating and condensing conditions. • ARHI polynomials overfit scroll compressor behavior. • Two-degree polynomials are more indicated to scroll compressors. • Less experimental points are required to characterize scroll compressor. • Pressure as polynomial variable is more suitable than temperature. This paper presents the analysis of the energy consumption and mass flow rate of scroll-type compressors. The study has included the data of several AHRI reports (especially AHRI 11 and AHRI 21) and data from other sources. A total of 7 different scroll compressors of different sizes have been considered in the study, some of them tested with various refrigerants (R134a, R32, R410A, R404a…). For all the studied compressors and refrigerants, the compressor energy consumption and mass flow rate values have been analyzed. The main objective is to better understand the dependence of these variables on the operating conditions and the refrigerant used. The analyzed data include tests following different superheat control, i.e., constant superheat or constant return temperature, so the effect of the inlet temperature on these variables is also discussed. As the main novelty of this study, the analysis of the response surfaces has allowed the authors to evaluate the most suitable correlation to use, including an analysis of the necessary experimental tests and where to place them to increase the model's accuracy. It was found that using the condensing and evaporating pressure terms is more universal than the classical temperature domain. In scroll compressors, AHRI polynomials overfits the compressor performance introducing significant deviations in the interpolation and extrapolation capabilities if the experimental data are not properly selected. Finally, it was found that lower degree polynomials are more suitable for this kind of compressor and has also the advantage of requiring fewer experimental point measurements to characterize the compressor with the corresponding cost-savings.

Impact of combustion chamber wall heat loss on the energy, exergy, ecology, NOx emission based performance and multiobjective optimization of the precooled scimitar engine

In this paper, the impact of the combustion chamber wall heat loss on the performance of the hydrogen-fueled precooled combined cycle Scimitar engine is investigated. Overall and exergy efficiencies, coefficient of ecological performance and coefficient of emission based ecological performance (CEEP) are considered as the performance indicators to analyze the effects of wall heat loss flux, chamber length, chamber contraction area ratio, throat area and nozzle convergent half angle. A multiobjective optimization is carried out to find the optimum values of hydrogen and air mass flow rates, cruise speed and altitude and core nozzle outlet area. It is found that a wall heat loss flux of 10 MW/m2 decreases the overall efficiency by 1.1% and causes an increase of 2 kJ/gNOx in CEEP. Multiobjective optimization revealed that increasing the hydrogen mass flow rate, decreasing the cruise speed and air mass flow rate improve the overall performance while the optimum values of cruise altitude and core nozzle outlet area are 23 km and 4.94 m2, respectively. The optimized design has a 20.35% better emission performance than the base design with a compromise of a 3.38% reduction in the overall efficiency.

Molecular dynamics simulations of unsteady evaporation of thin liquid argon layer into a vacuum

The unsteady evaporation of liquid argon layer into a vacuum was studied based on molecular dynamics technique using the LAMMPS package. The comparison of the mass flow rate with the known kinetic theory analytical equations was carried out for several temperatures of the liquid layer. It was obtained that after short relaxation time mass flow rate ceases to depend on time for some period. The relaxation time for mass flow rate was estimated. It turned out that this time depends on the temperature of the liquid layer and decreases with increase of its temperature. The mass flow rate values predicted by molecular dynamics simulation are found to be well described by some analytical formulas from kinetic theory. The temporal dynamics of the liquid layer was investigated. The linear dependence between film thinning rate and mass flow rate values was obtained both in the quasi-steady regime and out of it. It was found that liquid interface temperature depends on liquid thickness by power law with an exponent independent of initial liquid film temperature.

A new statistical approach to identify critical mass flow rate in CO2 nozzles near saturation conditions

The pressing needs to increase efficiency in heat pumps require refined design of various system components. In common reverse cycles, the throttling valve performs pure energy dissipation, and therefore it is well suited to be replaced by technologies such as ejectors and turbines, to augment system performance. In both two-phase turbines and two-phase ejectors a supersonic convergent-divergent nozzle is commonly required, which is responsible for accelerating the refrigerant fluid from the high-pressure part (e.g. condenser) to the low pressure part (e.g. evaporator). In the design phase of these nozzles, the accurate prediction of the maximum mass flow rate, also known as the critical mass flow rate, is particularly complex due to the two-phase nature of the expansion. In this paper, a new statistical approach to determine the value of the critical mass flow rate for CO2, as refrigerant fluid, is presented and assessed. This approach is based on the MF (Massflow Factor) parameter, which well correlates the value of mass flow rate in sonic conditions. The relationship shown here is based on open experimental information and it is validated on data from the open literature and the industry. The relative error on critical flow rate is less than 15% in the validation range, placing this statistical approach at a level of accuracy comparable to other physical models. An example of design is provided in this paper to demonstrate the potential of the relationship found. This approach provides the designer with a straightforward and validated basis for a reliable preliminary design of expanding two-phase nozzles.