Pipe Heat Exchanger Research Articles

Twisted tapes in solar chimney-earth air heat exchangers for equipment downsizing and passive cooling

Harnessing solar and geothermal energy in hot and arid climates is an effective strategy to reduce building energy consumption. This research investigates integrating Twisted Tapes (TT) into Earth Air Heat Exchanger (EAHE) pipes within a Solar Chimney (SC)-EAHE system, aiming to reduce EAHE pipe length while meeting ventilation requirements and decreasing cooling demand. Two key innovations are introduced: first, this study pioneers the integration of TT into a SC-EAHE system; second, it comprehensively explores TT geometry optimization, analyzing the effects of width ratio and rotation rate across 77 configurations. Numerical simulations are conducted in ANSYS Fluent using the k-ε RNG turbulence model to investigate thermal performance and airflow characteristics. Findings reveal that TT integration results in a 153 % increase in Nusselt number. Additionally, it is shown that a 1 m SC diameter achieves ventilation of 4.8 Air Changes per Hour (ACH) using TT with a width ratio and rotation rate of 0.5, while reducing EAHE pipe length by 2.6 %. Increasing the SC diameter to 1.25 m, with a TT width ratio of 0.6 and rotation rate of 1.25, leads to a 13 % (35 m) reduction in EAHE pipe length while meeting a minimum outlet temperature of 290.15 K and ACH requirements. However, the benefit diminishes beyond a 1.25 m SC diameter. This study contributes to understanding of integrating TT into SC-EAHE systems, addressing the critical need for sustainable energy solutions and offering a novel and energy-efficient approach for passive cooling in extreme climates.

Two‐Dimensional Solidification Simulation of PCM Molten Salt as a Thermal Energy Storage for Stirling Engine

ABSTRACTThermal energy storage technologies have been widely used to mitigate intermittency from renewable energy sources such as solar energy. Phase change material (PCM) is a material that can be used as a heat storage medium and is available in a wide range of operating temperatures. Molten salt is one of the PCMs that has the advantage of a very high operating temperature. The PCM solidification simulation based on HitecXL molten salt using COMSOL Multiphysics software was carried out with variations in heat absorption of 1–5 kW/m2, assuming constant heat absorption. The results showed that the PCM solidification process started from the surface of the Stirling engine heat exchanger pipe. The part of the PCM that is solidified falls due to gravity, causing a phenomenon similar to a droplet. The flow that occurred was natural, driven by the buoyancy force resulting from density changes due to temperature gradients in the solidification process. The time required for the PCM to completely solidify was closely related to the amount of heat absorption; the greater the heat absorption from the pipe, the faster the PCM is fully solidified.

Improving thermal environment and ventilation efficiency in high-temperature excavation tunnels via an innovative heat insulation and cooling baffle

An increasing number of tunnels inevitably encounter high-temperature environments induced by elevated geotemperatures. The energy demand for ventilation and cooling in excavation tunnels increases significantly as the temperature of the surrounding rock increases, thereby hindering the sustainable exploitation of deep resources. This paper presents an optimization method for airflow organization in excavation tunnels that integrates thermal insulation and cooling (TIC) baffles. The proposed approach significantly improves the cooling effect of the auxiliary ventilation system while reducing energy consumption. This method offers the advantages of simplicity, convenience, and cost-effectiveness. A multifield coupling model using COMSOL software was developed and validated to analyze the system, and the application scenario was explored. Several ventilation scenarios were examined, highlighting that TIC baffles effectively reduce the heat release from the surrounding rock and lower the airflow temperature in personnel areas in the excavation tunnel. By implementing TIC baffles, the average airflow temperature in the excavation tunnel decreases by 1.5 °C to 1.8 °C, resulting in a saving of approximately 5.11 kW in cooling energy. Increasing the circulating water flow in the heat-exchange pipe of the TIC baffles or reducing the initial circulating water temperature can enhance the cooling capacity of the TIC baffles and lower the tunnel airflow temperature to a certain extent. The distance between the TIC baffles and surrounding rock significantly affects the airflow temperature between the left and right TIC baffles. An excessive length of TIC baffles (L > 7 m) leads to heat accumulation and high-temperature airflow in localized areas. In This study, a method for optimizing the thermal environment and saving energy in high-temperature excavation tunnels is proposed.

Influence of convection on the thermal storage performance of energy tunnels

The decarbonization of the built environment requires rapid growth in energy storage solutions due to the intermittent nature of most renewable energy sources. This paper focuses on the efficacy of so-called energy tunnels (i.e., tunnels equipped with pipe heat exchangers) used for underground thermal energy storage. By harnessing a 3-D thermo-hydraulic finite element model validated against full-scale experimental data, this work specifically explores seasonal, medium-temperature, thermal energy storage operations of energy tunnels. Numerical simulations are performed to unravel the influence of convection resulting from groundwater flows and airflows on the thermal energy storage performance of energy tunnels. The analyses address the impact of different groundwater flow velocities, air temperatures, and airflow velocities on the thermal losses and storage efficiency of energy tunnels used as thermal batteries. The study discourages underground thermal energy storage in the presence of convection due to significant heat losses. It shows that thermal energy storage operations via energy tunnels are feasible in site conditions characterized by no groundwater flow, limited temperature differentials between the heat carrier fluid circulating in the pipe heat exchangers and the surroundings, and thermal insulation on the tunnel intrados.

Numerical study on hydrogen desorption performance of a new MgH2 solid-state hydrogen storage device

To explore the factors affecting the hydrogen evolution performance of a new MgH2 solid-state hydrogen storage heat exchanger, this paper designs the MgH2 solid-state hydrogen storage device. The study numerically investigates the influence of operating parameters and structural parameters on the hydrogen release reaction. The results demonstrate that the hydrogen desorption rate increases as the pressure decreases from 0.3 MPa to 0.1 MPa. Moreover, the hydrogen evolution reaction rate significantly rises with an increase in the inlet temperature of the heat transfer fluid (HTF) from 600 K to 700 K. Similarly, the rate of hydrogen evolution reaction increases with an increase in the flow rate of the HTF from 0.5 m/s to 1.25 m/s. The hydrogen evolution reaction time can be notably reduced by increasing the thickness of the annular HTF layer. Compared to no annular fluid layer, the completion time of the hydrogen desorption reaction is shortened by 558 s with a 5 mm thickness. The arrangement of heat exchanger pipes plays a crucial role in the hydrogen evolution reaction, and thus a comprehensive index M is defined to evaluate its influence. A higher M value indicates slower hydrogen release efficiency of the device. By optimizing the operating conditions, the hydrogen desorption time can be shortened by 93.4 %.

Simulation on solidification process of molten salt-based phase change material as thermal energy storage medium for application in Stirling engine

Abstract Thermal energy storage technologies have been widely used to mitigate intermittency from renewable energy such as solar energy. Phase change material (PCM) is a certain material that can be used as a heat storage medium and is available in a wide range of operating temperatures. Molten salt is one of the PCMs that has the advantage of a very high operating temperature. The PCM solidification simulation based on HitecXL molten salt using COMSOL Multiphysics software will be carried out with variations in heat absorption of 1 - 5 kW/m2, assuming constant heat absorption. The results show that the PCM solidification process starts from the surface of the Stirling engine heat exchanger pipe. The part of the PCM that has been solidified will fall following the direction of gravity and cause a phenomenon such as a droplet. The flow that occurs is a natural flow caused by the buoyancy force due to changes in density due to temperature gradients in the solidification process. The time required for the PCM to completely solidify is closely related to the amount of heat absorption. The greater the heat absorption from the pipe, the faster the PCM to fully solidified.

Analysis of nanofluid and nano-enhanced phase change material (NEPCM) in a heat exchanger for thermal management of electronic devices

Thermal management of high-power electronic devices is essential to control their enormous heat generation, which is usually the cause of their damage. Scientists have found several solutions for cooling electronic devices, but a counter-current heat exchanger has never been used. In the same context, numerical research on the thermal performance of a proposed new cooling system based on a counterflow heat exchanger combined with a heat sink is conducted in this article. Cu-H2O nanofluid, n-Docosane nano-enhanced phase change material, and water were selected as coolants, and they are compared in terms of temperatures, Nusselt number, heat transfer coefficient, pressure drop, friction factor, and performance enhancement coefficient using a two-phase mixture transient model based on Finite Volume method. Two cases of the proposed system are studied to find the optimal distance between heat exchanger pipes and the hot surface. Results are compared with previous experimental data to demonstrate that the system under study is accurate. They revealed that integrating the heat exchanger with the heat sink using Cu-H2O nf as a coolant maintained the hot surface temperature below 308 K with improved heat transfer by 31.22% compared to water. 0.25 mm is the optimum distance to find the highest thermal performance of the cooling system.

Influence of Chloride Concentration on Fretting Wear Behavior of Inconel 600 Alloy.

The nickel-based alloy Inconel 600, strengthened by solution treatment, finds extensive application as a heat exchange pipe material in steam generators within nuclear power plants, owing to its exceptional resistance to high-temperature corrosion. However, fretting corrosion occurs at the contact points between the pipe and support frame due to gas-liquid flow, leading to wear damage. This study investigates the fretting wear behavior and damage mechanism of the nickel-based alloy Inconel 600 and 304 stainless steel friction pairs under point contact conditions in a water environment. Characterization was performed using laser confocal scanning microscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Results indicate that the friction coefficient remains consistent across different chloride ion concentrations, while the wear volume increases with increasing chloride concentrations. Notably, friction coefficient oscillations are observed in the gross slip regime (GSR). Moreover, the stability of the oxide layer formed in water is compromised, diminishing its protective effect against wear. In the partial slip regime (PSR), friction coefficient oscillations are absent. An oxide layer forms within the wear scar, with significantly fewer cracks compared to those within the oxide layer in the GSR. It is worth noting that in GSR, the friction coefficient oscillates.

Synergistic effects of a swirl generator and MXene/water nanofluids used in a heat exchanger pipe of a negative CO2 emission gas power plant

The focus on optimizing heat exchangers contributes to improved temperature control mechanisms, ensuring the sustainable operation of innovative power plants working toward negative CO2 emissions. In the realm of oxy-combustion within Negative CO2 Emission Power Plants (nCO2PP), the temperature of combustion products surpasses 3000 ( K ) . Addressing this challenge, the imperative arises to reduce these elevated temperatures to a manageable 1100 ( ° C ) . This critical cooling process is achieved through the injection of water, facilitated by the implementation of heat exchangers. The study delves into the optimization of heat transfer within the heat exchanger pipe, specifically tailored for the context of a nCO2PP. Employing a numerical simulation, the investigation explores the impact of vortex generator geometry, vane angles, single and dual propeller-type swirl generators, and the integration of a novel class of fluid, MXene/water nanofluid. Initially, the study scrutinizes propeller-type geometry at vane angles spanning from 15° to 60°. The enhanced swirl flow associated with lower vane angles leads to improved fluid mixing, fostering more effective heat transfer. Results showed that the 15-degree vane angle, with a wider circumferential coverage, may result in increased wall contact, influencing heat transfer efficiency. Subsequently, at Re = 6000, incremental rates of the Nusselt number ( Nu n − Nu s Nu s %), for θ = 15°, 30°, 45°, and 60° are 175.1, 108.8, 90.7, and 40.3%, respectively. Also, the increment rates of Friction Factor ( f n f s ) for aforementioned vane angle are 38.48, 9.26, 4.08, and 2.42%, respectively. In addition, for ∅ MXene = 0.5 % , the Nusselt number experiences considerable increments of 22.94, 24.17, 24.70, and 24.707% at Reynolds numbers of 6000, 12,000, 18,000, and 24,000, respectively, compared to pure water, emphasizing the potential of MXene to enhance heat transfer efficiency.

Empirical modeling and experimental validation of gas-to-liquid heat pipe heat exchanger with baffles

Empirical modeling of heat pipe heat exchangers (HPHX) is the most economical and appropriate method for predicting its performance and estimating long-term economic benefits in the industrial field. Unfortunately, no models can predict the performance of HPHX with baffles that show complex flow characteristics, such as a combined flow arrangement of parallel flow and counterflow. This study presents the empirical model for HPHX with baffles, which predicts thermal performance and pressure drop based on empirical correlations and theoretical relations. It fabricated the HPHX with baffles composed of 95 copper two-phase closed thermosyphons (TPCTs) and measured its effectiveness, heat transfer rate, and pressure drop. We validated the presented model based on our experimental results and literature data. The validation results confirm that it can predict the HPHX performance with high accuracy, not only for the presence of baffles but also for various HPHX geometries (heat exchanger dimensions, number of baffles, etc.) and operating conditions (temperature and flow rate of hot and cold fluids). Finally, we analyzed and discussed the composition of HPHX performance, and as a result, enhancing forced convection between the working fluid and the TPCT bundle is a vital key to improving thermal performance, especially for HPHX that utilize gas (or air) as the working fluid. It was also found that the wall material had a negligible impact on thermal performance, so it was reasonable to consider stainless steel, which is more resistant to corrosion and erosion than copper. Our results are expected to be a great reference for engineers designing and manufacturing HPHX in the industrial field.

Impact of Geometrical Misplacement of Heat Exchanger Pipe Parallel Configuration in Energy Piles

Shallow geothermal or ground source heat pump (GSHP) energy systems offer efficient space heating and cooling, reducing greenhouse gas emissions and electrical consumption. Incorporating ground heat exchangers (GHEs) within pile foundations, as part of these GSHP systems, has gained significant attention as it can reduce capital costs. The design and optimisation of GHEs connected in parallel within energy piles have been researched widely, considering symmetrical placement, while the potential misplacement due to construction errors and the optimal placement remain mostly unexplored. This study utilises 3D finite element numerical methods, analysing energy piles with diameters from 0.5 m to 1.4 m, equipped with parallelly connected U-tube and W-tube GHEs. The impact of GHE loop placement is analysed, considering the influence of the ground and concrete thermal conductivities, pile length, fluid flow rate, GHE pipe diameter, and pile spacing. Results indicate a marginal impact, less than 3%, on the overall heat transfer when loops deviate from symmetry and less than 5% on the total heat transfer shared by each loop, except for highly non-symmetric configurations. Symmetrical and evenly spaced loop placement generally maintains favourable thermal performance and ease of installation. This study underscores the flexibility in GHE design and construction with a low risk of thermal yield variations due to uncertainties, particularly with a separation-to-shank distance ratio between 0.5 and 1.5 in a symmetrical distribution.

Bench studies of the influence of operating conditions on operational safety of steam turbine air-cooled condensers at subzero outdoor temperatures

Condensation processes are widely spread in various branches of industrial production and, in particular, in electric power industry, where, according to experts' data, heat removal in thermodynamic cycles of steam turbine plants (STP) operating as part of combined cycle plants (CCP) and autonomously, in the 21st century will be exercised mainly in air-cooled condensers (ACC). At the same time, the use of ACC as a part of steam turbine units operating in climatic conditions typical for the Russian Federation (RF) determines the relevance of problems to be solved to ensure their safe operation at subzero outside temperatures. One of these challenges is to ensure long-term safe operation of the ACC, with the formation of ice on the inner surface of the heat exchange pipes minimized. To conduct the research, Steam Turbine Air-Cooled Condenser research and training stand was used. The paper presents the combined circuit and measurement diagram of the research and training stand, and gives a brief description of the design of the ACC. Experimental modes have been determined, and methods for processing experimental data and analyzing the results obtained have been developed. As part of the study, experiments were carried out on 18 steady-state operation modes of the stand. At the same time, the values of the main operational parameters of the ACС varied within the following limits: the temperature of the cooling air at the ACС inlet — from minus 11,5°C to minus 1,8°C; the cooling ratio — from 176 to 790. The relative weight content of air in the vapor varied from 0,051% to 0,12%. An analysis of the obtained results was carried out, on the basis of which a relationship was established that allows, for various negative temperatures of the cooling air at the inlet to the ACС, to determine the highest value of the cooling ratio at which its long-term safe operation is possible. An algorithm for using the obtained relationship is given.

Compact heat pipe heat exchanger for waste heat recovery within a low-temperature range

Heat pipe heat exchangers (HPHX) are attracting attention for being capable of effective heat exchange through phase change. Much waste heat is generated at low-temperature sources, but there has been a lack of research on this. Most previous studies focus on large HPHXs over 1 m in length. In the present study, a compact HPHX (185 × 70 × 140 mm3) with nine heat pipes was fabricated, and the potential for waste heat recovery (WHR) was investigated at low heat sources. Also, the thermal performance of the HPHX was compared with and without the fin of the heat pipe. Experiments were conducted by changing the hot-side gas temperatures (50, 75, 100, and 125 °C) and mass flow rates (0.03, 0.04, and 0.05 kg/s). The heat transfer rate and pressure loss had a linear relationship with the hot-side temperature and mass flow rate. Despite a low temperature 50 °C, more than 100 W of heat can be recovered using a compact HPHX. At least 1.8 times improved thermal performance was obtained in HPHX in which finned heat pipes were installed. These results are expected to serve as indicators for various applications that generate low-temperature waste heat, such as clothes dryers and kitchen hoods.

Experimental study on exhaust internal circulation desiccant wheel evaporative cooling chiller

Evaporative cooling chillers reduce the water temperature by absorbing heat during the evaporation of water without the need for compressor assistance or refrigerants. It is an energy-saving and environmentally friendly cooling technology but it needs necessary improvements in the applicable environmental area and refrigeration performance due to ambient air wet-bulb temperature limitations. To obtain chilled water below the dew-point temperature of the ambient air, an exhaust internal circulation desiccant wheel evaporative cooling chiller is proposed and experimentally investigated. A combination of a heat pipe exchanger, a desiccant wheel, an air cooler and an air heater are applied to reduce the wet-bulb temperature of the ambient air before it passes through the direct evaporative cooler. At the same time, the low-temperature and low-humidity exhaust air from the direct evaporative cooler is used to circulate to improve chiller performance. The experimental results show that the average chilled water temperature of the proposed chiller is 10.2 ℃ lower than that of the direct evaporative cooling chiller under five typical environmental conditions. The wet-bulb efficiency of the proposed chiller is the highest at high temperatures and high humidities (36 ℃ and 80% RH), which is 6 times greater than that of direct evaporative cooling chillers. Therefore, the proposed chiller expands the application range of evaporative cooling technology, which is especially suitable for humid areas with low-grade heat utilization such as solar energy.

Optimization of solar and heat pump complementary powered desiccant air conditioning system

The effective utilization of renewable heat sources is critical for energy saving in desiccant air conditioning systems. A new solar and heat pump complementary powered desiccant air conditioning system is proposed. The system consists of a solar and water source heat pump complementary reheat subsystem, a two-stage desiccant wheel, a three-stage air cooler, and a two-stage heat pipe exchanger. Simulation are performed in the transient simulation software TRNSYS, and the particle swarm optimization and the Hooke Jeeves algorithm with life cycle cost as the objective function are applied to optimize the collector area, the heat storage tank volume and the water-source heat pump power. The results show that the monthly average coefficient of performance of the system is 5.1, 5.6, 5.5 and 4.8 in June, July, August and September, respectively. Compared to the conventional air conditioning system, the new system has a 58.4% reduction in operation cost and a payback period of 6.6 years. The CO2 emission reduction rate of the new system can reach 65.2% in July and 65.1% in August, while it is the lowest in September at 62.9%. Based on the above, the new system has better energy efficiency, economic and environmental benefits.

Numerical investigation on the heat storage/heat release performance enhancement of phase change cemented paste backfill body with using casing-type heat pipe heat exchangers

Cemented paste backfill mining technology that recycling tailings and waste rocks can effectively reduce heat damage. Heat pipe exchangers, demonstrating much higher thermal conductivity than water pipe exchangers, led to the development of a novel phase change backfill body system with a built-in casing heat pipe exchanger (HP-PCB). Numerical analysis revealed that, for the melt and solidification of a large amount of PCM, the temperature step phenomenon was observed at both heat storage and heat storage/heat release coexistence stages. Increased surrounding rock temperatures enhanced heat storage and heat release capacities, but reduced system energy efficiency. The optimal water flow velocity was identified at the laminar-turbulent transition flow rate, 0.32 m/s. An increase in water inlet temperature resulted in lower heat release capacity and system energy efficiency. The energy efficiency of the HP-PCB system exceeded that of the traditional water pipe-backfill system by 37.22%. At a surrounding rock temperature of 45 °C, cooling water velocity of 0.32 m/s, and a 6 °C inlet water temperature, the HP-PCB system achieved its highest energy efficiency coefficient, 86.38%. These findings highlight the HP-PCB system potential for efficient geothermal energy extraction in mine.

DEM Investigation on the Flow and Heat Transmission Characteristics of Multi-Size Particles Mixed Flow in Moving Bed

The moving bed heat exchanger (MBHE) has been widely applied in the recovery of waste heat of industrial particles. Currently, investigations focus on uniform-size particles in the MBHE, but few studies are conducted on multi-size particles produced by industrial granulation. Therefore, based on the discrete element method (DEM), the heat transmission model of multi-size particles is established, and flow and heat transmission processes of typically normal distribution particles in the MBHE are studied. In conclusion, there are significant differences in particles tangential velocity and contact number in local regions of a heat exchanger pipe, resulting in different local heat transmission coefficients. In addition, the increases in outlet particle velocity and inlet particle temperature significantly enhance the heat transmission. When the outlet particle velocity grows from 1 mm/s to 5 mm/s, the overall heat transmission coefficient increases by 36.4%, and as the inlet particle temperature rises from 473 K to 873 K, the overall heat transmission coefficient increases by 16.1%.

Influence of different types of pipes on the heat exchange performance of an earth-air heat exchanger

An earth-air heat exchanger (EAHE) is a green technology suitable for regulating the thermal environment of buildings; however it requires a large space and high construction costs. In this study, five types of pipes, such as aluminum, stainless steel, polyvinyl chloride, corrugated, and perforated corrugated pipes were selected as the heat exchange pipes to study the effects of pipe material, roughness of pipe, and bottom perforation on the performance of the EAHE under short-time, intermittent, and continuous operation conditions, and to identify the most suitable EAHE pipe. The results showed that in the case of thinner wall thickness, the pipe material had a negligible effect on EAHE performance, with a preference for cheaper pipes. Compared to smooth pipes, corrugated and perforated corrugated pipes significantly improved the heat transfer performance and reduced the pipe length by 28.33–33.33% and 22.67–29.33%, respectively. Although perforations in the bottom of the pipe could increase the heat exchange between the air inside the pipe and the lower soil layer, accelerate the recovery of the soil temperature, and increase the cooling time, it significantly reduced the heat exchange efficiency. Thus, the corrugated pipe with the best overall performance indicated that a pipe with rough surfaces was the most suitable pipe type for EAHE. This can significantly lower the amount of space and money needed for EAHE construction, making it suitable for a variety of building types and contributing to the solution to the issue of rising global temperatures brought on by the use of conventional energy in the construction sector.

A method for assessing non-uniformity of thermally induced stresses in the cross-section of energy piles

The non-uniform distribution of thermally induced stresses within energy piles presents a significant challenge when assessing their thermo-mechanical behavior. This study proposes an innovative approach to assess the non-uniformity of thermally induced stresses in energy piles by employing a novel parameter known as the concentration coefficient of thermally induced stress (Kth). Kth serves a dual role: firstly, it quantifies the non-uniformity of thermally induced stresses in the cross-section of energy piles, and secondly, it enhances the accuracy of determining the average thermally induced stress and axial force in energy piles when combined with field testing. Sensitivity analyses were performed using both the Taguchi method and the full factorial test method to investigate the influence of various factors on Kth. The descending order of impact weights for each influencing factor on the non-uniformity of thermally induced stress is as follows: pile-soil stiffness ratio, pile configuration, soil's Poisson's ratio, soil-pile thermal expansion coefficient ratio and slenderness ratio, with pile-soil stiffness ratio, pile configuration and soil Poisson's ratio combined effects take up over 90% of the observed variations in Kth. Notably, when the soil stiffness is low, Kth can exceed a value of thirteen, indicating an extreme non-uniformity in the thermally induced stress distribution across the cross-section. Additionally, a lower number of heat exchanger pipes is associated with a more non-uniform thermally induced stress distribution, but the non-uniformity tends to stabilize as the number of U-shaped heat exchanger pipes exceeds three.

Experimental study on heat power of wet and pipe sections of wet/dry cooling tower with extended surface pipe exchanger

A hybrid system for recirculated water cooling of industrial enterprises is proposed. The major feature of the cooling system is a wet/dry cooling tower with an inner pipe exchanger. To enhance the heat transfer process, the outer surface of the heat exchanger pipe has fins. Design and function of the experimental setup are described. The goal of this work is to evaluate experimentally the heat power of the wet and pipe sections of the cooling tower. Results were presented as dependencies of the heat power in the wet/dry cooling tower on the mean gas velocity (from 0.89 to 3.20 m/s) and the ratio of the weight flow rates of the gas/liquid phases at various irrigation rates (13.7-35.6 m3/(m2.h)).