Maximum Mass Flow Rate Research Articles

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.

Performance characterization of a novel compact dust collector with pleated filter cartridges

A compact dust collector loaded with four pleated filter cartridges is numerically studied by Computational Fluid Dynamics (CFD). The performance of the dust collector is evaluated during filtration and during backwashing, and the predictions are compared with the experimental results. In the filtration operation, the upper right corner entry design effectively guides the airflow to the two sides of the four cartridges through the air opposite-side-wall impacting and rebounding. A relatively poor filtration is found at the right side of the left lower cartridge. The CFD predictions agree well with the experimental data in terms of showing better backwash cleaning performances of the lower cartridges and at the cartridge front positions. During the 50 ms pulse-jet backwashing, the difference between the maximum and minimum air mass flow rates through a total of 16 × 2 inject holes is less than 4.0%. The high pressure of 0.5 MPa draws the air flowing from the normal exit, which acts as the majority of the backwashing air (ca. 73.7%). The hydrostatic pressure acting on the four cartridges is greater than 1750 Pa in 80% of the pulse-jet cleaning time.

Thermal Performance of a Counter-Flow Double-Pass Solar Air Heater With The Steady and Pulsating Flow

The present work studied the influence of pulsating flow as an active method on the thermal performance of a double-pass solar air heater with a tubular solar absorber. A ball valve has been used as a pulse generator mounted at the downstream flow of the solar air heater. The experiments were under indoor conditions with a constant heat flux of 1000 W/m2, and different air mass flow rates ranged from 0.01 to 0.03 kg/s. Moreover, the study covered three pulsation frequencies varied from 1 to 3 Hz. Based on the experimental outcomes, it can be observed that the heat transfer rate is enhanced by applying the pulsating flow, where it was found that the outlet temperature in the case of applying the pulsating flow rises by about 25.6 - 27% as compared with the steady flow case. Moreover, pulsating flow offers a higher effective thermal performance by about 15.2 % at the maximum air mass flow rate compared with the steady flow. In addition, the findings pointed out that varying the pulsation frequency from 1 to 3 Hz produces an enhancement in heat transfer rate and in solar heater effective efficiency, where it was found that when changing the frequency from 1 to 3, the increment of effective efficiency ranged from 3.8 to 6.9 % depending on the air mass flow value.

Multifidelity Simulation Research on the Low Reynolds Number Effect on the Engine Performance at Different Altitudes

Abstract With the rapid development of unmanned aerial vehicles, the effect of the low Reynolds number on gas turbine performance and high-altitude endurance has received extensive attention. However, the existing three-dimensional component modeling cannot meet the design requirements of the whole engine level, and the accuracy and physical principles of the existing engine empirical correction cannot be guaranteed. Through the study of a single-shaft turbojet engine, this paper adopts a versatile and accurate coupling method, which combines the volume method and the full coupling method and conducts multifidelity simulation research on the zero-dimensional engine model and the three-dimensional component model. Then, based on the high-altitude test data, under typical operating conditions, compared with the existing empirical correction method in gasturb, the accuracy of the engine inlet flow, fuel flow, thrust, and exhaust gas temperature predicted by the volume-based fully coupled method is improved by 6.2%, 7.9%, 4.7%, and 11.4%, respectively. Next, as the flight altitude rises from 0 km to 21 km, the Reynolds number reduces, the working lines approach the surge lines, and the maximum mass flow rate and the efficiency of the engine components gradually decrease. In addition, in the flow field of the components, the thickness of the boundary layer increases, the shock wave intensity decreases, and the position moves forward. The core innovation of this article is that it provides a creative multifidelity evaluation method for gas turbines to effectively solve the problems of insufficient accuracy of the existing empirical correction methods and the inability of the component design to meet the gas turbine requirements in the study of the low Reynolds number effect at different altitudes, which significantly strengthens the connection among the component internal flow field information extraction, the component characteristics analysis, and the gas turbine performance matching. Moreover, it is conducive to the scientific design of the advanced unmanned aerial vehicles' power.

An experimental investigation of a desalination system based on an evacuated tube collector coupled with a heat exchanger

AbstractAccording to the report published on global water stress, the world will face a huge water crisis by 2040, due to continuous decay of freshwater resources and an increasing population of human beings. To fulfill this increasing demand for freshwater, we need to find a new source. As the sea contains most of the water available on earth, desalination of sea water can be a solution. Furthermore, the use of solar energy for desalination process can make it a sustainable solution. This is why it is very important to work on solar thermal desalination system. In recent years, a lot of research has been reported on solar still integrated with evacuated tube collector (ETC) to improve its efficiency and productivity. But the problem of salt deposition in evacuated tubes was very common in these systems. So in the present work, a new solar thermal desalination system based on ETC is developed. In the present system, ETC is integrated with a storage tank, which further has a heat exchanger. Therminol 55 is used as a working fluid, which transfers heat from ETC to saline water. System performance is evaluated in terms of productivity, energy efficiency, exergy efficiency and economic feasibility. The productivity of the system is 4.2 L/m2/day. The average energy efficiency delivered by the system is 43.92% and average exergy efficiency to be 9.53%. The maximum mass flow rate of thermic fluid is 0.003962 kg/s. The freshwater production cost by the desalination system is 0.022 $/L.

Numerical study on adiabatic compressed air energy storage system with only one ejector alongside final stage compression

Sliding-pressure operation of the centrifugal compressor in the charging process makes adiabatic compressed air energy storage (A-CAES) system maintain high roundtrip efficiency. However, the final stage compressor may produce choke at low backpressure. This paper proposes an A-CAES system with one ejector alongside the final stage compressor to alleviate the choke. Dividing outlet air of the third stage compressor into two parts, one part goes into the fourth stage compressor and flows into the ejector as primary fluid. Another goes into the ejector as secondary fluid. The charging process includes two periods. A thermodynamic model of the proposed system is built for simulation study. Simulation results show that the backpressure variation range of sliding-pressure compression reduces by 39.87% with adding ejector. The maximum mass flow rate of A-CAES with sliding-pressure operation is closer to the choke margin. Increasing initial storage pressure benefits to decrease energy consumption and improve exergy efficiency of proposed system. Compared with the A-CAES with constant-pressure operation, the proposed system’s roundtrip and exergy efficiency increase with increasing entrainment ratio and initial storage pressure. For A-CAES with ejector, sliding-pressure operation, and constant-pressure operation, their maximum roundtrip efficiencies reach 57.94%, 58.32% and 55.31%, respectively, under different initial storage pressures.

Humidifying solar collector for improving the performance of direct solar desalination systems: A theoretical approach

In this paper, a new type of solar collector named humidifying solar collector, that is, a solar collector with air humidification function, is proposed. The particularity of this system compared to previous systems in the literature is that the quantity of liquid water present in the collector at each instant is equal to the quantity that will evaporate within the following unit time, no longer greater. This minimizes the quantity of liquid water present in the collector at each instant, and consequently allows to reach desired evaporation temperatures in shorter times and even under low solar irradiances, and minimizes the thermal resistance between evaporation surface and absorber caused by water depth. Then, a theoretical and comparative study by simulation using Engineering Equation Solver software between the performance of the humidifying solar collector-based solar still (proposed system) and that of the solar air heater-based humidification dehumidification solar desalination system (conventional system) is conducted. The performance parameters assessed are energy and exergy efficiencies, dry air mass flow rate required and the maximum water mass flow rate that can evaporate in that air. The results reveal that, in general case, the proposed system is fundamentally more efficient than the conventional system. For instance, for the sizes and heat transfer parameters chosen in this study, the performance of the proposed system is 1.3–32.2 times higher than that of the conventional system; its freshwater productivity under incident solar irradiance of 900 W/m2 can reach 2.923 kg/h, and can be further improved by optimizing the design of the humidifying solar collector.

Natural Gas Conversion and Organic Waste Gasification by Detonation-Born Ultra-Superheated Steam: Effect of Reactor Volume

The pulsed detonation (PD) gun technology was applied for the autothermal high-temperature conversion of natural gas and atmospheric-pressure oxygen-free allothermal gasification of liquid/solid organic wastes by detonation-born ultra-superheated steam (USS) using two flow reactors of essentially different volume: 100 and 40 dm3. Liquid and solid wastes were waste machine oil and wood sawdust, with moisture ranging from 10 to 30%wt. It was expected that decrease in the reactor volume from 100 to 40 dm3, other conditions being equal, on the one hand, should not affect natural gas conversion but, on the other hand, could lead to an increase in the gasification temperature in the flow reactor and, correspondingly, to an increase in the product syngas (H2 + CO) quality. The PD gun was fed by natural gas–oxygen mixture and operated at a frequency of 1 Hz. As was expected, complete conversion of natural gas to product syngas in the PD gun was obtained with H2/CO and CO2/CO ratios equal to 1.25 and 0.25, irrespective of the reactor volume. Liquid and solid wastes were gasified to H2, CO, and CH4 in the flow reactors. The steady-state H2/CO and CO2/CO ratios in the syngas produced from waste machine oil were 0.8 and 0.5 for the 100-dm3 reactor and 0.9 and 0.2 for the 40-dm3 reactor, respectively, thus indicating the expected improvement in syngas quality. Moreover, the maximum mass flow rate of feedstock in the 40-dm3 reactor was increased by a factor of over 4 as compared to the 100-dm3 reactor. The steady-state H2/CO and CO2/CO ratios in the syngas produced from the fixed weight (2 kg) batch of wood sawdust were 0.5 and 0.8 for both reactors, and the gasification time in both reactors was about 5–7 min. The measured H2 vs. CO2 and CO vs. CO2 dependences for the syngas produced by the autothermal high-temperature conversion of natural gas and atmospheric-pressure allothermal gasification of liquid/solid organic wastes by USS at f = 1 Hz were shown to be almost independent of the feedstock and reactor volume due to high values of local instantaneous gasification temperature.

Aerodynamic Performance of the Single-Stage Transonic Turbine With Different Reaction Degrees

A numerical method was used to investigate the reaction degree effects on the aerodynamic performance and flow structure of the single-stage transonic turbine. The SST-γ-θ turbulence model was employed to predict a transition for the boundary layer near the blade surface. This work utilized a public PW-E3 blade profile from NASA. Five different reaction degrees were adopted, corresponding to Ω = 0.15, 0.27, 0.33, 0.44 and 0.59. In addition, different off-design conditions were considered with three reaction degrees. The efficiency, blade surface pressure and high Mach number distributions were significantly associated with the reaction degrees. Results indicated that the highest efficiency point was observed at Ω = 0.33. The trailing edge shocks and the reflected waves were visible in the cascade channels. The Shock wave was easily detected in the stator channel at lower reaction degrees while it was displayed in a rotor with a higher reaction degree. When the reaction degree was increased, the high Mach number region was expanded in the rotor channels while it was reduced in stators. Besides, the highest efficiency points were also observed around π = 1.5 for all operating conditions. Furthermore, the critical pressure ratio was discovered and the maximum mass flow rate gradually decreases as the reaction degree increases.

Simulation of a Pilot Scale Power-to-Liquid Plant Producing Synthetic Fuel and Wax by Combining Fischer–Tropsch Synthesis and SOEC

Power-to-Liquid (PtL) plants can viably implement carbon capture and utilization technologies in Europe. In addition, local CO2 sources can be valorized to substitute oil and gas imports. This work’s aim was to determine the PtL efficiency obtained by combining a solid oxide electrolyzer (SOEC) and Fischer–Tropsch synthesis. In addition, a recommended plant configuration to produce synthetic fuel and wax at pilot scale is established. The presented process configurations with and without a tail gas reformer were modeled and analyzed using IPSEpro as simulation software. A maximum mass flow rate of naphtha, middle distillate and wax of 57.8 kg/h can be realized by using a SOEC unit operated in co-electrolysis mode, with a rated power of 1 MWel.. A maximum PtL efficiency of 50.8% was found for the process configuration without a tail gas reformer. Implementing a tail gas reformer resulted in a maximum PtL efficiency of 62.7%. Hence, the reforming of tail gas is highly beneficial for the PtL plant’s productivity and efficiency. Nevertheless, a process configuration based on the recirculation of tail gas without a reformer is recommended as a feasible solution to manage the transition from laboratory scale to industrial applications.

A novel combination of absorption heat transformer and refrigeration for cogenerating cooling and distilled water: Thermoeconomic optimization

A novel cogeneration system consisting of an absorption heat transformer and refrigeration system integrated with a water desalination system is proposed, analyzed, and optimized. The cogeneration and desalination systems interacted thermally. The proposed system is flexible in producing cooling and distilled water with variable fractions. Influences on system performance are investigated of the decision parameters. A maximum value of 39 °C is achieved for gross temperature lift. Also, it is observed that the condenser temperature, which is influenced by climate conditions, affects system performance. The system performance is optimized considering such criteria as exergy efficiency, the rate of distilled water production, and total product unit cost. Depending on the criteria used for optimization, the results indicate a minimum total product unit cost of 42.6$/GJ, a maximum exergy efficiency of 27.9%, and a maximum distilled water mass flow rate of 0.53 kg/s. The minimum total capital cost rate and exergy destruction cost rate are found to be 11 $/h and 3.89 $/h, respectively. Under optimized conditions, the generator is seen to contribute the most to the total exergy destruction rate. The values of levelized cost of energy and water and payback period are 0.013 $/kWh, 9 $/m3 and 1.8 year, respectively.

The Critical Diameter for Continuous Evaporation Is between 3 and 4 nm for Hydrophilic Nanopores.

Evaporation studies of water using classical molecular dynamics simulations are largely limited due to their high computational expense. This study addresses that issue by developing coarse-grained molecular dynamics models based on Morse potential. Models are optimized based on multi-temperature and at room temperature using machine learning techniques like Genetic Algorithm, Nelder-Mead algorithm, and Strength Pareto Evolutionary Algorithm. The multi-temperature-based model named as Morse-D is found to be more accurate than the single temperature model in representing the water properties at higher temperatures. Using this Morse-D water model, evaporation from hydrophilic nanopores with pore diameter varying from 2 to 5 nm is studied. Our results show that the critical diameter to initiate continuous evaporation at nanopores lies between 3 and 4 nm. A maximum heat flux of 21.3 kW/cm2 is observed for a pore diameter of 4.5 nm and a maximum mass flow rate of 16.2 ng/s for a pore diameter of 5 nm. The observed heat flux is an order of magnitude times larger than the currently reported values from experiments in the literature for water, which indicates that we need to focus on nanoscale evaporation to enhance the critical heat flux.

Experimental research on performance of an oil-free moving-coil symmetrical dual-piston linear compressor for the J - T throttle refrigerator

In order to improve the efficiency of the Joule-Thomson (J-T) throttling refrigerator, an oil-free symmetrical dual-piston moving-coil linear compressor was developed, and its principle was demonstrated in detail. As the core component of the J-T throttling refrigerator, the linear compressor provides the pressure ratio and mass flow rate required by the throttling cycle. The linear compressor prototype was tested with nitrogen to evaluate its performance at different pressure ratios, strokes, and driving frequencies. Key performance parameters have been obtained, and the experimental results show that the input power is 175.2 W, the mass flow is 1.128 g/s, the unit power mass flow is 6.438 mg/s/W, the motor efficiency, volumetric efficiency, isentropic efficiency, and isothermal efficiency is 87.7%, 81.5%, 74.9%, and 63.7% at the design parameter (pressure ratio of 3.0, stroke of 10.0 mm, frequency of 60.0 Hz), respectively. The maximum mass flow rate is 1.742 g/s, and the maximum motor efficiency, volumetric efficiency, isentropic efficiency, and isothermal efficiency is 88.1%, 94.0%, 81.2%, and 73.4%, respectively. The symmetrical dual-piston linear compressor brings large-capacity and high efficiency, which provide a useful attempt and reference for the optimization of the linear compressors for the J-T throttling refrigerator.

Flow and transmission characteristics of the multistage hydrogen Knudsen pump in the micro-power system

The multistage hydrogen Knudsen pump based on the thermal transpiration effect has exciting application prospects for hydrogen transport in the micro-power system. The multistage hydrogen Knudsen pump with the silica microchannel is beneficial to its temperature control, which can accurately provide hydrogen transport and storage for the micro-power system. In this paper, the model of the multistage hydrogen Knudsen pump with the silica microchannel is established. The effects of the microchannel height, width and parallel number on the flow and transmission characteristics of the multistage hydrogen Knudsen pump are studied by using the method of N–S equations with the slip boundary. The temperature difference, Knudsen number, thermal transpiration effect, maximum mass flow rate, maximum pressure difference and performance curve under different microchannel parameters are analyzed in detail. The results show that the thermal transpiration effect increases with the microchannel height and decreases with the microchannel width. As the number of parallel microchannels increases, the microchannel is closer to the silicon cantilever, and the thermal transpiration effect becomes stronger. The pumping performance increases with the microchannel height, width and parallel number. The pressurization performance increases with the microchannel height and parallel number. The research results have important guiding significance for the application and design of the multistage hydrogen Knudsen pump in the micro-power system.

Performance analysis of tower solar aided coal-fired power plant with thermal energy storage

• An innovative TSACPG system with thermal energy storage is proposed. • Solar energy is used to heat reheat steam and boiler feed water simultaneously. • Thermal performances of the system under different loads are explored. • Solar contribution and CO 2 reduction in the system are discussed. • Economic evaluation of the system with different configurations are studied. A novel tower solar aided coal-fired power generation (TSACPG) system with thermal energy storage is proposed in this paper. Based on the principle of energy grade matching and cascade utilization, the high-temperature solar energy is used to heat the first and second reheat steam extracted from the boiler and the low-temperature solar energy is used to heat the boiler feed water. The maximum steam extraction mass flow rates of the boiler under different load rates are obtained and the thermal performances are also analyzed. The results show that the maximum steam extraction mass flow rates from the first and second reheat part of boiler are 69.7 kg/s and 37 kg/s in 100 %THA (Turbine Heat Acceptance), 78.7 kg/s and 37 kg/s in 90 %THA, 81 kg/s and 31.4 kg/s in 75 %THA, 76.3 kg/s and 31 kg/s in 60 %THA, 68.2 kg/s and 31.2 kg/s in 50 %THA load, respectively. And the standard coal consumption rates can be reduced by 39.85 g/kWh, 39.47 g/kWh, 38.08 g/kWh, 35.50 g/kWh and 35.25 g/kWh, respectively. Both the boiler thermal efficiency and overall thermal efficiency of the TSACPG system descend sightly and the boiler exergy efficiency ascends. With the decline of the load, the solar-to-electricity efficiency, the power output and the proportion of solar power generation descend gradually. And they can reach up to 28.62%, 120.90 MW and 18.32% in 100 %THA load, respectively. The economic performance analysis of the TSACPG system is carried out. The system configuration and investment corresponding to different typical days, different thermal energy storage hours and capacities are considered. The payback times and the levelized costs of electricity of the solar field in different DNI level regions are analyzed. The results show that these two evaluation indices are the lowest in high level DNI region and they are on the contrary in low level DNI region. As for the environmental protection, the CO 2 emission rates are reduced by 69.26 g/kWh in 100 %THA, 68.61 g/kWh in 90 %THA, 66.19 g/kWh in 75 %THA, 61.69 g/kWh in 60 %THA and 61.26 g/kWh in 50 %THA load, respectively. The maximum annual CO 2 emission can be reduced about 526739.55 tons. The renewable energy and traditional fossil energy are integrated organically in this study and the low-carbon transformation of coal-fired power generation system is further promoted. The study also contributes to the realization of both the carbon peak and the carbon neutralization.

The second law analysis of a humidification-dehumidification desalination system using M-cycle

Humidification-dehumidification desalination (HDD) systems offer a feasible approach for the production of fresh water in inaccessible areas as they can be operational using renewable energy and require little maintenance. Various studies are being carried out to boost the system performance. In this paper, an open air open water HDD system is proposed that exploits the enhanced evaporation and condensation processes by implementing with the Maisotsenko cycle (M-cycle). The system utilizes solar energy as the energy input to heat the saline water. A thermodynamic model is formulated under steady-state conditions, considering the first and second law of thermodynamics. The energetic and exergetic performance of the system is studied. The model is first validated with the experimental data and a good agreement is found where the maximum discrepancy is about 6.0 %. Effects of different operating conditions on key performance parameters such as the Gain Output Ratio (GOR), specific energy consumption (SEC), exergy destruction, and exergy efficiency are analyzed. An improvement is observed in the GOR when the inlet air temperature is raised at constant humidity ratio. The system exhibits better performance in dry air environment when compared with humid air environment. The analysis shows a maximum mass flow rate of desalinated water of 22.3 kg/h, recovery ratio (RR) of 0.223, GOR of 3, SEC of 0.23 kWh/kg and an exergy efficiency of 43.21 %.

Experimental and numerical investigation on thermal and hydraulic performance of novel serpentine minichannel heat sink for liquid CPU cooling

A novel serpentine design for minichannel heat sink is investigated experimentally and numerically to enhance thermal performance of the heat sink for liquid CPU cooling. The heat sink is fabricated from aluminum and is located in a plexiglass container. The channels have square cross section with deep and width of 2 mm. Mass flow rate and inlet temperature effect on the performance of the maze serpentine heat sink are studied. Five different mass flow rate varies between 0.0017 kg/s and 0.0087 kg/s and three different inlet temperature (15°C, 20°C and 25 °C) is investigated. Pure water is used as the coolant. The results indicate that by changing the minichannel design from straight to the proposed mazed shape geometry, baseplate temperature decreases 11.2% and Nusselt number increases 4.2 times in the maximum mass flow rate. Thermal resistance is decreased in the novel maze serpentine minichannel heat sink and by increasing mass flow rate the difference get larger so that maximum convective thermal resistance difference for and the novel maze serpentine minichannel is 54% that is observed in the lowest mass flow rate. Also, higher thermal performance is achieved in the maze serpentine minichannel heat sink.

Discharge characteristics of non-gravity-driven powder in horizontal silos

Powder flow inside horizontal silos is essential to ensure the efficient operation of the spacecraft using powder engines under horizontal flight positions. In the present work, the discharge characteristics of non-gravity-driven powder in the horizontal silo were investigated experimentally, with an emphasis on the half cone angle, aeration position, and additional pressure. The experimental results show that the mass flow rate first increases with decreasing half cone angle and then approaches saturation. Aerating at the cylinder was proved to be able to significantly increase the mass flow rate compared with the previous aeration at the cone. Increasing the additional pressure can effectively improve the mass flow rate, but there is a limit value called pressure surcharge limit to maximize the discharge rate. And aerating at the cylinder can further increase the pressure surcharge limit as well as the maximum mass flow rate, which is close to the ideal flow rate based on the liquid-like hypothesis. Finally, an index η is proposed to evaluate the overall flow-promoting effect to determine the optimal aeration position.

Studying the design parameters of an auger filler in packaging black pepper seeds using the discrete element method

Auger fillers are vastly used in the food industries for packaging edible seeds, spices and powders. This research studies the effects of design parameters on the mass flow rate of black pepper seeds discharged from an auger-filler and the required input power. These parameters were auger angular velocity, diameter and pitch-to-diameter ratio and agitator angular velocity. It is intended to reach an optimal design of the auger filler with higher efficiency. To investigate the effects of the parameters and to reduce the number of simulations, the Taguchi algorithm is used. The obtained data from 16 discrete element simulations are analyzed using analysis of variance (ANOVA). It is concluded that the most effective parameters on the output mass flow rate and the required power are the auger outer diameter and pitch-to-diameter ratio, respectively. Finally, the best outcome corresponding to the maximum mass flow rate and the minimum required power is found to occur at the auger angular velocity of 550 rpm, the agitator angular velocity of 25 rpm, the auger outer diameter of 2 inches, and pitch-to-diameter ratio of 1.5.

Capillary trees for passively pumping water

Capillary flows are an attractive feature for passive water harvesting as they require no external driving force to pull the fluid out within the capillary network. Here we analyze the architecture of capillary flow networks in a steady state, and the impact of the network morphology on the maximum mass flow rate that can be extracted for a fixed network volume and fixed network footprint. We develop a search algorithm to test the possible locations of all the junction and bifurcation nodes and the changes in diameter ratios with the objective of obtaining the maximum mass flow rate from the network. We define the capillary strength as a local indicator to determine the geometrical parameters of each channel that allow the overall mass flow rate to be sustained. It is shown that the diameter ratio of connected tubes for maximum mass flow rate depends on the distance from the network outlet, and therefore does not follow the Hess–Murray law. The superiority of dendritic architectures in the roots and canopy branches of capillary trees is demonstrated.