Friction Coefficient Resistance Research Articles

On the effectiveness of using carbamide-based salt baths for low-temperature cyanidation of improved carbon and alloy steels

Purpose. A study of cyanidation of improved carbon and alloy steels of grades 30, 30HGT, 30H13 at a temperature of 550–580 °C was carried out in baths based on carbamide and sodium carbonate. Recommendations on the use of these baths for surface hardening of carbon and alloyed improved steels used for the manufacture of machine parts are formulated. Methods. The microstructure of the diffusion layer of steels on transverse sections was studied using a Quanta FEG – 650 electron scanning microscope with an EBCD focused ion beam microanalysis system. Cyanide wear tests were performed under friction conditions analogous to those of die tools. The wear resistance of the carbonitrided samples was investigated on a SMTs-2 friction machine. The tests were performed under both dry friction and boundary friction conditions. Results. The high efficiency of the proposed bath composition at a given temperature has been experimentally shown. As a result of cyanidation, modified layers saturated with solid inclusions (ε-phases) are formed on the surface of steels, characterized by high hardness, low coefficient of friction and high wear resistance. Conclusion. According to the results of the conducted research, it can be concluded that low-temperature cyanidation of improved steels of various grades can be carried out in cyanide-free salt baths. The optimal composition of the cyanide bath is 40% carbamide (NH2)2CO; 40 % soda ash Na2CO3 and 20 % NaCl table salt. The proposed bath does not contain toxic and scarce components, therefore it is environmentally safe and very cheap and can be used with great effect in machine-building, repair and tool industries.

Numerical Analysis on Frictional Heat Effect in Polyether-Ether-Ketone (PEEK)/Steel Pair by using OpenFOAM Model

The PEEK material has been applied to a sliding bearing system in a power plant system because of its high mechanical durability. In the solid friction of the PEEK materials, the frictional heat becomes the important factor because the temperature increase due to the frictional heat causes the rapid increase of the frictional coefficient of the specimen. To maintain the low frictional coefficient of the PEEK materials, an effective cooling method for the PEEK materials needs to be developed. In this study, the passive cooling method, which attaches the heat sink to the PEEK materials, was suggested. For evaluating the suggested cooling method of the PEEK materials, the calculation model adopting OpenFOAM, which is open-source software, has been developed. Adopting some functions and libraries of OpenFOAM, the frictional heat, heat resistance, and heat transfer coefficient on the heat sink were modelled. The sliding bearing experiment was conducted and time variation of the temperature and friction coefficient in the ring specimen were measured. The temperature variation in the ring specimen was compared with the calculation result. From the numerical calculation results, the developed calculation model could simulate the temperature-time variation of the ring obtained in the experiment, when the variation of the frictional coefficient, heat resistance, and heat transfer coefficient was modelled appropriately. Based on the friction and wear test results, by applying a heat dissipation mechanism to the ring test piece, the calorific value of the PEEK material can be reduced, and it is stable. It was suggested that the friction was maintained.

Enhancing optical and thermohydraulic performance of linear Fresnel collectors with receiver tube enhancers: A numerical study

Linear Fresnel collector system is a type of solar thermal utilization installation. It is mainly used to focus solar radiation on the receiver tube to generate high temperature thermal energy which can be applied in many aspects. This study investigates five different types of receiver tube models using water as the flowing medium, which leads to improving heat transfer performance by means of being equipped with enhancers. The optical results and thermohydraulic performance of the Linear Fresnel collector system are evaluated through Monte Carlo Ray Tracing and Computational Fluid Dynamics (CFD) simulation methods. The obtained optical results reveal that the distribution of energy flux density concentrating on the receiver tube surpasses that of the parabolic trough collector system. In order to maintain an energy reception rate of 90.0% or higher, the installation height range of the receiver tube should be between 1468–1532 mm. When the sun-tracking error increases from 0.0° to 1.0°, the overall optical efficiency of the Linear Fresnel collector system decreases from 98.9% to 79.7%. The thermohydraulic performance shows that the enhancers can generate a swirling flow as its main feature, which effectively promotes the homogenization of the temperature field and destroys the boundary layer near the receiver tube wall, thus greatly improving the convective heat transfer in the receiver tube. However, the introduction of the enhancers also means that the pressure drop loss of the receiver tube increases. Furthermore, the impact of the Kenics mixer's enhancer on heat transfer and flow characteristics is further amplified as the rotation rate decreases, owing to its alternating and complex structure. Through a comparative analysis of the influence of different receiver tube models on Nusselt number (Nu), Frictional resistance coefficient (f) and comprehensive evaluation criterion (PEC) under four rotation rate conditions (y = 6.3, 8.1, 11.34, 18.9), the conclusions present that the receiver tube with an enhancer at a low rotation rate has a larger Nu than that at a high rotation rate, while the Frictional resistance coefficient changes little at different rotation rates. Therefore, the PEC is higher when the receiver tube is equipped with a low-rotation-rate enhancer. Moreover, the receiver tube equipped with a Kenics mixer at a rotation rate of 6.3 was found to be the overall optimum case, with the PEC value varying from 1.47 to 1.73.

Effect of Various Sintering Temperatures on the Friction and Mechanical Properties of PEEK/PTFE Blends

Polytetrafluoroethylene (PTFE) has a very low coefficient of friction and outstanding corrosion resistance, but its limited use is due to high wear and tear and low hardness. Polyetheretherketone (PEEK) offers low wear, high temperature resistance and a slightly higher coefficient of friction. In the research we describe here we examined the mechanical and tribological properties of PEEK/PTFE blends manufactured at various sintering temperatures (350 °C–390 °C). The experimental data demonstrated that the PEEK/PTFE blends exhibited the highest tensile strength, 22.97 Mpa, when sintered at 380 °C, making them the most resistant to breaking or deforming. The elongation at break increased with the increase of sintering temperature, and the highest value of elongation at break for the PEEK/PTFE blends was 429.16% when sintered at 390 °C, and the lowest value was 283.37% when sintered at 350 °C. The PEEK/PTFE blends exhibited the lowest coefficient of friction, measuring 0.174, when sintered at 350 °C. The lowest mass abrasion rate for the PEEK/PTFE blends was 6.04 × 10−7 mm3/N·m when sintered at 360 °C.

Effects of various proportions TiB2p-TiCp reinforced Al–Cu–Mg composites in high-temperature mechanical properties and sliding wear behaviors

Synergistic reinforcement of dual-phase particles with different sizes was always considered superior to single-phase reinforcement in composites, but there were few studies to investigate the role of each part in enhancing properties. In this work, 40 vol% (TiB2p-TiCp)/Al–Cu–Mg composites with different proportions of TiB2p and TiCp (3:1, 2:1, 1:1, 1:2 and 1:3), were fabricated by the combustion synthesis to contrast the strengthening effect of dual-phase particles from the interface stability and the characteristics of dual-phase particles. Calculated by the first principle, TiB2 (3.12 J/m2) presented better interfacial stability with Al matrix than TiC (1.61 J/m2). Under the circumstance of the same volume fraction, the composites with a higher proportion of TiB2p usually show higher yield and maximum compressive strength and effectively prevent the crack growth of composites. However, excess submicron sized TiB2p tends to produce cracks at the hexagon edge when the loads were applied and formed crack loops delaminating materials. When the TiB2p/TiCp proportion was 1:1, the plasticity and strength were beneficially balanced at the elevated temperature. Otherwise, the composite with TiB2: TiC = 3:1 possessed the best wear resistance (coefficient of friction: 0.22) at a sliding velocity of 0.32 mm/s, 30 N load) among other composites (AR12, AR11, AR21, and AR31) at 473 K, which reduced 45%, 64%, 73% and 86%, respectively. The main wear mechanism was abrasive wear when the TiB2 proportion was dominant. Submicron sized TiB2p with better interface bonding can keep the rigidity of the composites to resist the plastic flow, while TiC nanoparticles are easier to be extracted during the wear process.

Tribological properties and evolutionary mechanisms of a nanocrystalline Al-Mg-Si alloy at room and cryogenic temperatures

A nanocrystalline Al-Mg-Si alloy model was established to reveal the temperature effect in nanotribology using atomistic simulations. Compared to room temperature, the samples at cryogenic temperature (CT) exhibited an increase in both the coefficient of friction (COF) and wear resistance. At CT, the thermal activation of interface atoms reduced, thereby inhibiting surface grain rotation and sliding within the atomistic model. There was grain coarsening (suppressed at CT) instead of grain refinement typically observed for surface grains. The results also indicated that changes in load influenced the COF response, with higher loads resulting in higher COF values. The friction laws in simulation and experiment are similar.

Investigation of Wear Properties and Corrosion Resistance of Electrodeposited Ni-P-PTFE Nanocomposite Coating on Mg-Li alloy

Ni-P-polytetrafluorethylene nanocomposite coatings based on Mg-Li alloy were successfully prepared by utilizing electrodeposition method. The nanocomposite coatings were investigated employing scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The microstructure and composition of the coating were studied by friction, wear and corrosion tests. The experimental results reveal that when the concentration of PTFE is 3 g / L, deposition temperature is 70 °C, current density is 2 A/dm2, and pH of the plating solution is approximately 5.5, a uniform and dense Ni-P-PTFE nanocomposite coating is formed on Magnesium alloy substrate, and it exhibited a low coefficient of friction (∼1.5) and superior abrasion resistance. The co-deposition of PTFE particles can effectively reduce the friction coefficient and wear rate, and the wear mechanism is characteristic cutting wear. Under artificial seawater conditions, the experiments have demonstrated that the nanocomposite material possesses a corrosion current density of 3.9×10-5 A/cm2.

Development and evaluation of CrAlAgN self-lubricating coatings for high temperature metal forming dies

Conventional lubricants are widely used for die release as well as for cooling assistance on the die surface. However, lubrication is difficult at high temperatures. Oxidation and scaling occur on the work pieces that lead to poor surface finish and a possible warping of the material during cooling. The aim of this research is to develop self-lubricating CrAlAgN nanocomposite coatings for metal forming dies and evaluate their thermal fatigue resistance and wear behavior at elevated temperatures. The CrAlAgN coatings with different Ag contents have been deposited by plasma-enhanced magnetron sputtering. The structure and properties of the coatings were systematically studied to determine the optimal Ag content for achieving a combination of good adhesion, thermal fatigue resistance, and surface lubricity at elevated temperatures. The thermal fatigue resistance of the coatings was evaluated using thermal cyclic testing by cycling the coatings from room temperature to 800 °C up to 1200 cycles. The high temperature wear behavior of the coatings was evaluated using a tribometer up to 900 °C. Good thermal fatigue resistance and low coefficient of friction (COF) were observed in the CrAlAgN coatings with an Ag content in the range of 5–10 at. % at 800 °C. The CrAlAgN coating with 10 at. % Ag exhibited the lowest average COF of 0.05 at 800 °C. The COF of thick CrAlAgN coatings (8 at. % Ag) decreased from 0.5 to 0.2 from 500 to 900 °C, accompanied by an increase in the wear rate under more aggressive wear test conditions. The lubricity of the CrAlAgN coatings at high temperatures was attributed to the lubrication effects from the mixed oxides and encapsulated Ag diffused toward the surface. To further evaluate the coating performance, a hydraulic hot forging punch was coated with a thick CrAlAgN (8 at. % Ag) coating and evaluated in the industrial forging process. The preliminary in-plant trials demonstrated that the coating significantly reduced the dimensional distortion and wear for the forging punch.

Isolated slug traveling in a voided line and impacting at an end orifice

Driven by upstream high-pressure steam, liquid slugs in nuclear power plant pipelines impact the end orifice at high speed, leading to bursting pipelines and threatening the plant's safety. This research aimed to accurately and efficiently assess the dynamic behavior of an isolated slug driven by pressurized air in a voided line with an end orifice. An improved one-dimensional (1D) model for the slug motion and impact was established. The dynamic variation of the pressure at both the slug's tail and front, the variation of the slug length, and the frictional resistance coefficient in the model was obtained by three-dimensional (3D) computational fluid dynamics (CFD). Based on 27 cases with different pipeline diameters and tank pressures, it was observed that the driving air pressure had a quadratic relationship and that the slug length had a constant rate of decrease vs the slug tail displacement. Finally, the decrease in the driving air pressure behind the slug, the increase in the air pressure ahead of the slug, the holdup coefficient, and the friction factor obtained from the 3D CFD results were interpreted in the 1D model, and the velocity histories of the liquid slug were found to be in excellent agreement with the 3D CFD solutions.

Numerical Study of Effects of Inhomogeneous Roughness on the Ship Friction Resistance

The cleanliness of a ship hull is crucial for energy saving. Biofouling, which can cause microbiological corrosion, can also increase ship resistance. If left unchecked, this can lead to inefficient energy use and increased emissions, contributing to global warming. Ship resistance is a critical factor in ship design, which affects ship powering. The analysis of friction resistance due to biofouling on a ship hull requires an examination of the distribution of roughness height (ks), which is randomly distributed. In this study, an analysis of friction resistance coefficient (CF) due to inhomogeneous roughness is carried out with the help of CFD simulations with a full-scale model at 19 kn and 24 kn. The roughness of three ship segments, namely aft-hull, midship, and fore-hull, varies with ks values of 125 μm (P), 269 μm (Q), and 425 μm (R), respectively, while maintaining the same wetted surface area (S) in each segment. According to the simulation results, the RQP model produces the highest CF of 2.154 x 10-3, while the PQR model produces the smallest CF of 2.119 x 10-3 each at speed 24 knots. The CF contributes an average of 72.2% CT.

Composition, structure, and wear resistance of (TiZrNbMoTa)CxN1-x high entropy alloy carbonitride coatings prepared by reactive radio-frequency magnetron sputtering

HEN has high hardness and good toughness but a high coefficient of friction and poor wear resistance. In this study, a high hardness, toughness, and wear-resistant HECxN1-x coating was prepared by reactive radio-frequency magnetron sputtering (RFMS) technology. The phase composition, microstructure, mechanical properties, and tribological properties of the HEN and HECxN1-x coatings were investigated. The results show that all coatings have single-phase rock salt structures. The double anion lattice structure of the HECxN1-x coating produces a high lattice distortion effect and grain refinement effect, which realizes the strengthening and hardening of the coating. When the [C]/([C] + [N]) ratio is 0.3, the hardness of the HECxN1-x coating reaches the maximum value of 41.7GPa, and when the [C]/([C] + [N]) ratio is 0.4, the coating toughness reaches the maximum value of 0.91GPa, which are 48 % and 203 % higher than HEN. The self-lubricating effect of supersaturated precipitated amorphous carbon makes the HECxN1-x coating achieve excellent tribological properties. Among them, HEC0.5N0.5 coating has the best tribological properties, its coefficient of friction (COF) is 0.391, which is 148 % lower than that of HEN coating, and the wear rate is reduced to 1/15 of HEN coating, which is one order of magnitude reduction. Introducing the C element based on HEN can effectively solve the problems of high friction coefficient and poor wear resistance of high entropy nitride ceramic coatings.

Theoretical modeling and multi-parameter influence analysis of piston wind in the ultra-high-speed elevator hoistway

The high-speed airflow generated when an ultra-high-speed elevator runs in the hoistway will cause a significant piston effect. Therefore, it is essential to study the variation law of the piston wind in the hoistway and the influence of different parameters on the piston wind in the hoistway. This paper first establishes the theoretical model of the piston wind in the hoistway when the elevator ascends, descends, and intersects based on the unsteady flow theory of the Bernoulli principle. The effectiveness and accuracy of the theoretical model are verified through experimental measurements and numerical simulations. Second, based on the verified theoretical model, the influence of the five parameters of the car speed, car height, hoistway height, blockage ratio, and frictional resistance coefficient on the variation law of the piston wind and ventilation rate in the hoistway is systematically analyzed. Integrating the five parameters, a multi-parameter universal theoretical formula for hoistway ventilation rate is proposed. Finally, a gray correlation analysis is performed on each influencing parameter, which showed that the piston wind in the elevator hoistway is most affected by the blockage ratio, followed by the car speed, hoistway height, and frictional resistance coefficient, and is least affected by the car height.

Experimental Study on the Coefficient of Internal Frictional Resistance in the Annular Gap during the Plunger Gas Lift Process

Plunger gas lift process technology is an economical solution to the problem of gas well liquid buildup. However, in-house simulation experiments revealed that the high-speed movement of the plunger may lead to fluid leakage and generate annular gap frictional resistance. To address this issue, a detailed experimental study was conducted to comparatively analyze five existing frictional-resistance models, which were found to have significant deviations. Therefore, we propose a new model of annular gap frictional resistance and validate it with experimental data, and the results show that the new model is more accurate and reliable. We also conducted a comparative analysis of production-site examples by using VB programming and found that when considering the annular gap frictional resistance, the upward travel time of the plunger was delayed, the difference between the upper and lower end face pressures was significant, and the difference in speed was 1.73 m/s. This indicates that the annular gap frictional resistance cannot be ignored and is crucial for optimizing plunger gas lift process technology and improving the drainage efficiency of gas wells.

Numerical investigation on flow and heat transfer characteristics of helium–xenon gas mixture in rod bundles

The helium-xenon(He–Xe) gas mixture with low Prandtl number and good heat transfer characteristics suits for the advanced high heat flux and compact gas-cooled reactors. A numerical simulation was conducted on the flow, heat transfer, and turbulent mixing characteristics of He–Xe gas mixture in a tightly arranged triangular rod bundle subchannel. The transition characteristics of He–Xe gas mixture in rod bundle structure were obtained. The friction resistance coefficient, Nusselt number(Nu), and turbulent mixing factor β was corrected within the Reynolds number(Re) range of 3 × 102 - 1.8 × 105. The research results indicate that the transition occurs at Re equal to 2000 and forms a transition zone within the Re range of 2000–5000; The Blasius correlation can describe the wholly turbulent flow precisely, but it is suitable to adopt a new formula in the transition zone; The local Nu prediction performance of the modified Peckett correlation is in good agreement with the numerical simulation results, and the Petukhov correlation with shape correction and temperature correction factors has good prediction results on global Nu; The turbulent mixing factor using Re and shape parameters can better describe the mixing characteristics. This study has reference value for the design of rod bundle reactors using He–Xe gas mixtures as working fluids.

Annealing Effect on Mechanical and Tribological Behaviors of Nanoscale Mechanics of Zr60Cu25Al5Ag5Ni5 Thin-Layer Metallic Glasses for Engineering Materials Applications.

A new and unique alloy formulation design strategy has been developed in order to fabricate thin-layered metallic glasses (TLMGs) with superior fracture resistance and low coefficient of friction (COF) during the nanoscratching test. Due to the outstanding properties, TFMG could be applied for different uses, such as for surface coating, biomedical, bioimprinting, electronic devices, spacecraft, and railway, all of which need surface fracture resistance. The fabricated Zr-based metallic glass was prepared from Zr, Al, Cu, Ni, and Ag above 99.9 Wt % in purity by arch melting techniques. TFMGs were coated on silicon wafer by sputtering the vapor deposition method from bulk metallic glass then annealed below glass transition temperature Tg ∼ 450 °C for 10, 30, and 60 min. Nanoindentation and nanoscratch tests were used to investigate nanomechanical and nanotribological properties, and atomic force microscopy (AFM) was used to examine the surface morphology and microstructures of TLMG. The nanoindentation data indicated that the average hardness of metallic glasses increased from 9.75 (as-cast MG) to 13.4 GPa (annealed for 60 min). Coefficients of friction for the cast sample, annealed for unannealed, 10, 30, and 60 min, were 0.062, 0.049, 0.039, and 0.03, respectively, as well as the wear depths were 201.56, 148.43, 37.32, and 25.27 nm, respectively. These studies show that the coefficient of friction and wear rate decreases when the annealing time increases as a result of atomic reordering and structural relaxation that occurred at longer annealing times. Furthermore, continuous wear process, wear depth, wear track volume, and contact area decrease with increasing annealing time. This study can be used to design protocols to prepare novel TLMGs, which have outstanding mechanical and tribological properties for engineering materials applications.

Microstructure evolution, phase formation, mechanical and tribological response of deep cryogenically treated hard WC-6%Co cutting bits

Improving the productiveness of rock cutting bit is an essential requirement for sustainable mining. Different heat treatment techniques are employed in the past to improve the proficiencies of cutting bits. Out of them, cryogenic treatment (CT) is accepted as a viable method for expanding the service life of a variety of cutting tool materials. The intention of the present study is to evaluate the effect of cryogenic treatment under varying soaking duration (12, 24 and 36 h) on hardness and wear resistance of WC-6%Co rock cutting bits. It also addresses the underlying mechanisms that CT carries in the modifications of microstructure and phase transformation. The β-Co phase fraction has been significantly reduced due to cryogenic treatment. The wear resistance of both cryo-treated and untreated bits was examined by scratch test and sliding wear test. From the results, an increase in hardness (CT 24–13.09 %) was observed as compared to UT, which is associated with a transformation from face-centered cubic α-cobalt (FCC α-Co) to hexagonal close-packed ε-cobalt (HCP ε-Co) phase due to cryogenic treatment. The coefficient of friction and wear resistance for the cryo-treated bits correspondingly increases in comparison to the untreated bit. CT 24 bit exhibits the maximum hardness of 2212 HV, an elevated COF (16.64 %) and the highest wear resistance (87.15 %) compared to UT and other CT bits. From the results, cryogenic treatment of cutting bits can be recommended for rock cutting application in mining industries.

Study of Cyclic Plasticity and Creep Ratchet Behavior of PTFE

Due to its superior corrosion resistance and low coefficient of friction, polytetrafluoroethylene (PTFE) is extensively used in the aerospace, machinery, chemical, and pharmaceutical industries. However, PTFE components encounter complex alternating stresses, resulting in ratchet and creep, which will affect the component’s reliability. It is therefore necessary to clarify the PTFE’s resistance to ratchet and creep. In this paper, uniaxial ratchet and tensile creep experiments were conducted at five temperatures on a PTFE dog-bone tensile specimen. At various temperatures and stress levels, the effects of average stress and stress amplitude on the cyclic plastic behavior of PTFE were investigated. It is demonstrated that the ratchet strains and strain rates at 23 °C are greater than those at 50 °C. The reason for this is that the PTFE material exhibits different crystal states at these two temperatures. At temperatures above 50 °C, the ratchet strain and ratchet strain rate increase with temperature. At temperatures above 100 °C, the ratchet strain and ratchet strain rate of PTFE materials increase more rapidly due to the glass transition. By analyzing the creep strain and ratchet strain of specimens subjected to varying levels of average and amplitude stress, it was discovered that the creep strain and ratchet strain caused by the average stress under the same stress increment were greater than those caused by the amplitude stress.

К РАЗРАБОТКЕ ВЫСОКОЭФФЕКТИВНЫХ ПОРИСТЫХ ПОРОШКОВЫХ ФРИКЦИОННЫХ ПОКРЫТИЙ ДЛЯ РАБОТЫ В МАСЛЕ

The issues of development and research of new high-performance porous powder friction coatings for operation in oil with increased coefficient of friction and wear resistance, obtained by plasma spraying, are considered in relation to cones of synchronizers of gearboxes and disks of friction and brake units. The characteristics of the developed porous powder coatings and the technological parameters of their production for friction devices of transmissions of tracked vehicles with a high specific power are given.

Tribological and thermomechanical evaluation of polypropylene nanocomposites containing different dimensional structures of carbon and ceramic nanoparticles

ABSTRACT This study describes the development of PP nanocomposites using hydrothermally assembled carbon nanotubes (CNTs)/barium titanium (BT) (denoted as BTC) and graphene nanosheets (GNs)/boron nitride (BN) (denoted as BNG) nanoparticles. The PP nanocomposites were fabricated via the development of a masterbatch using polypropylene maleic anhydride (PPMA), followed by diluting with pure PP via melt compounding. The wear resistance and thermomechanical properties of the nanocomposites exhibited a substantial improvement, where about 96.8% increase in wear resistance and low coefficient of friction were recorded. While about 230% increase in glass transition temperature was measured with the nanocomposites relative to the pure PP. The developed nanocomposites have potential applications in automobile and other machine components where high wear resistance and thermal-mechanical properties are required.

Коефіцієнт гідравлічного опору тертя капілярів за малих чисел Рейнольдса

Heat transfer pump circuits with liquid or two-phase heat transfer fluids are widely used in thermal management systems in both space and ground applications. These systems play an important role in maintaining the optimal temperature and heat distribution in various processes and devices. Such systems use throttles to ensure efficient distribution of coolant flows through the hydraulic network. It is especially important to ensure the reliability of the system at low coolant consumption. Therefore, a rational approach is to manufacture throttles in the form of capillary segments. Capillary throttles can regulate the flow of coolant with high accuracy, which makes it possible to improve control over the thermal regime of the system. To calculate and determine the characteristics of such throttles, it is important to know the coefficient of hydraulic friction resistance λ, which is used in the Darcy formula. This coefficient depends on various factors, including the geometry of the throttle, physical properties of the heat transfer fluid, and flow conditions. Therefore, the aim of this study was to determine the value of the hydraulic friction resistance coefficient λ. In this work, experiments were performed with the shedding of copper capillaries of different internal diameters (0.8-1.2 mm) in water and isopropyl alcohol. The experiments were carried out in the laminar and transient regions, in the range of Reynolds numbers from 250 to 6050. Conclusions. In the laminar region (Re < 1185), it is recommended to use the Poiseuille formula. In the transitional and turbulent regions (1185 < Re < 6050), it is recommended to use the Blasius formula. The results of the experiments made it possible to obtain data on the value of the hydraulic friction resistance coefficient λ. These data can be used to calculate throttles in similar heat transfer systems. Moreover, the paper provides recommendations on the use of well-known formulas for calculating throttles, which allows engineers and designers to effectively implement these elements in their projects. Thus, the research conducted in this paper has important practical implications for the development and optimization of heat transfer systems in space and terrestrial applications.