Thermal Mode Research Articles

Determination of the circulation flow rate in the calculation of internal hot water supply networks

Calculations of internal ring networks of buildings have always been, are and will be an urgent task. The schemes of internal hot water supply systems change, the number of floors of buildings changes, the location of heating points from which hot water begins its journey to the consumer changes, the definition of water consumption changes, and finally the calculations themselves change, but it is undoubtedly the calculation methods for centralised hot water supply systems that are a key part of creating reliable and economical hot water supply networks in buildings. Modern methods consist of three different calculations: the supply part of the system, the circulation part with the determination of pressure losses in the entire system, and the thermal disinfection mode of the system. The circulation flow rate methodology widely used in Ukraine is based on a 1985 regulatory document and borrowed part of the calculation from the 1992 Polish regulations. As a result, questions arise that are not answered in the DBN. In terms of determining the heat losses of individual sections of the hot water system, not everything is perfect either. A building is designed for a lifespan of 50 years or more with daily, round-the-clock use of heat energy, and the heat consumption for preparation and transportation of hot water is the largest in the building and requires a detailed calculation. The DBN "Internal Water Supply and Sewerage" provides two figures for all cases: 11 and 7 W/m (specific heat losses by pipes of the internal hot water supply network). The calculated surface temperature of the pipes in different parts of the network varies, the air temperature in the premises through which the pipes pass varies, and the diameters of the pipes in certain areas change, but the two figures remain unchanged. Moreover, it is recommended that, regardless of the insulation material used for pipe insulation, the insulation thickness should be at least 10 mm. This may have been appropriate in 1985, when there were no computer programs for calculations and fewer thermal insulation materials, but now it is 2023 and the situation is completely different. The article, after analysing the regulatory documents, proposes a methodology for determining the circulation flow rate and calculating the hot water supply network in the mode of passing this flow rate.

3D coupled tearing-thermal evolution in solar current sheets

Context.The tearing instability plays a major role in the disruption of current sheets, whereas thermal modes can be responsible for condensation phenomena (forming prominences and coronal rain) in the solar atmosphere. However, how current sheets made unstable by combined tearing and thermal instability evolve within the solar atmosphere has received limited attention to date.Aims.We numerically explore a combined tearing and thermal instability that causes the break up of an idealized current sheet in the solar atmosphere. The thermal component leads to the formation of localized, cool condensations within an otherwise 3D reconnecting magnetic topology.Methods.We constructed a 3D resistive magnetohydrodynamic simulation of a force-free current sheet under solar atmospheric conditions that incorporates the non-adiabatic influence of background heating, optically thin radiative energy loss, and magnetic-field-aligned thermal conduction with the open source codeMPI-AMRVAC. Multiple levels of adaptive mesh refinement reveal the self-consistent development of finer-scale condensation structures within the evolving system.Results.The instability in the current sheet is triggered by magnetic field perturbations concentrated around the current sheet plane, and subsequent tearing modes develop. This in turn drives thermal runaway associated with the thermal instability of the system. We find subsequent, localized cool plasma condensations that form under the prevailing low plasma-βconditions, and demonstrate that the density and temperature of these condensed structures are similar to more quiescent coronal condensations. Synthetic counterparts at extreme ultraviolet (EUV) and optical wavelengths show the formation of plasmoids (in EUV) and coronal condensations similar to prominences and coronal rain blobs in the vicinity of the reconnecting sheet.Conclusions.Our simulations imply that 3D reconnection in solar current sheets may well present an almost unavoidable multi-thermal aspect that forms during their coupled tearing-thermal evolution.

Comparison of melting efficiency between blue, green, and IR lasers in pure copper welding

Pure copper parts are commonly used in many industrial products because of their low thermal resistance and high electrical conductivity. However, connecting high-quality and high-efficiency copper materials remains a challenge. This is because pure copper has low absorption of near-infrared light, making it difficult to weld stably with a near-infrared laser. Visible light lasers should realize high-efficiency laser welding of pure copper. However, there are few reports comparing the laser wavelength dependence of welding efficiency for pure copper. In this study, bead-on-plate welding was performed on pure copper plates of 2 mm thickness using a 1.5 kW blue diode laser (445 nm), a 16 kW IR disk laser (1030 nm), and a 3 kW green disk laser (515 nm). Bead-on-plate welding of pure copper was performed in the thermal conduction mode or the keyhole mode by varying the laser spot diameter and power, and the amount of melting was measured from cross-sectional observations. As a result, compared to the IR disk laser, blue and green lasers showed higher melting efficiency in both the thermal conduction and keyhole modes, and the melting behavior was more stable. In thermal conduction mode welding, the melting efficiency was 0.2% with the IR disk laser and 0.7% with the blue diode laser. In keyhole mode welding, the melting efficiency with the blue diode laser or green disk laser was about 7%, which is equivalent to that with the IR disk laser with 2.5 times the output power.

Experimental investigation on the operation performance of photovoltaic double skin façade in winter

Photovoltaic double skin façade (PV-DSF) offers a versatile solution to address the escalating energy demands of buildings by combining power generation and indoor air temperature adjustment functionalities. Most prior research concentrated on its summer performance, while the winter season receives less attention. This paper concentrates on its operation performance in winter, to provide an experimental framework for its efficient operation. In this regard, the performance of internal circle and thermal buffer mode (both are possible operation modes in winter) were compared via control variable experiments, and the feasibility of mechanical ventilation is also examined regarding the trade-off between the energy consumption of fans and additional energy benefit. These experiments were performed in the full-size experiment rig at Harbin, China, a city with severe cold climate. The experiment results conclusively demonstrate that the internal circle mode can outperform the thermal buffer mode on a cold, sunny day by 10.9%, and the total energy-saving potential can be further increased by 12.6% if fans are activated to enhance cavity airflow. While the experimental data during partly cloudy emphasizes the significance of a suitable operation schedule and shows that PV-DSF can only be switched to internal circle mode when cavity air is fully heated.

A Shear-Sliding Rigid-Flexible Coupled Skin Variable-Sweep Wing Design and Heat-Fluid-Structure Multifield Coupling Analysis

The variable-sweep wing is very attractive for cross-speed domain aircraft. The shear-sliding rigid-flexible coupled skin variable-sweep wing and its associated mechanism are designed and optimized. The variable-sweep wing has smooth continuous deformation and rigid-flexible coupling features. The calculation model of the sliding skin patch segmentation strategy is established, and the aerodynamic characteristics of the two-dimensional airfoil before and after the deformation of the wing skin are analyzed. According to the deformation characteristics of sliding skin, the configuration of the associated mechanism is determined, and the kinematic characteristics of the reference points of each skin are calculated. The kinematic simulation verifies the force of the mechanism model at the joint of skin surfaces during the deformation process. Considering the aerodynamic heat at supersonic speed, the heat transfer, heat distribution, and structural thermal modes between the flow field and the skin are calculated based on the finite element method. The dynamic characteristics of the swept wing with different flight speeds and different morphologies are analyzed. The natural frequencies are found to be reduced by about 30% to 50% compared to cold models at supersonic speeds. Based on the results of the thermal fluid-solid coupling calculation, the skeleton structure of the swept wing is optimized, and the skeleton structure with 25% mass reduction and better performance is obtained.

Application of a clean fuel produced by electrolysis in iron ore sintering process: Brown gas injection to assist sintering

Using a clean fuel produced by electrolysis named Brown gas to assist sintering in the iron ore sintering process was proposed to reduce coke consumption and carbon emissions. The effect of additional injection of Brown gas on the combustion characteristics and the quality of the sintered ore were explored. An optimal fuel ratio was investigated by gradually reducing the coke ratio based on Brown gas injection. The experimental results show that additional injection of Brown gas improves the thermal mode of the sintering bed, improves fuel combustion efficiency, prolongs the duration time of melting temperature, and the sintered ore yield and shatter strength first increases and then decreases, reaching the maximum value at an injection concentration of 2%. Based on a Brown gas injection concentration of 2%, the coke ratio can be reduced from 4.5% to 4% without affecting the quality of the sintered ore. As the coke ratio further decreases to 3.5%, the quality of the sintered ore deteriorates even if the Brown gas injection concentration increases to 3%. Based on a 2% Brown gas injection, the consumption of coke can be reduced by 11.1%, and the carbon emissions during the sintering process can be reduced by 11.1%.

Critical ignition conditions for propane/air premixtures impinging on electric heated surfaces: An experimental study

To contribute to exact predictions of the ignition of flammable mixture by a hot surface and ensure safety against fire, this study aims to clarify the critical ignition condition of a propane/air premixture impinging on a hot surface with external heating. The ignition threshold of heat flux depends on the flow velocity, but that of temperature hardly depends on flow velocity and equivalence ratio. The ignition occurred at the position where the residence time of species was the longest. It corresponds to the position of the lowest heat transfer coefficient. The temperature boundary layer thickness played a significant role in the ignition process as only the heat flux from the top, bottom, and back surfaces of the heater contributed to ignition in the presence of forced convection. The prediction model of the ignition threshold of heat flux and temperature was derived through dimensional analysis. This model effectively explains the ignition characteristics, regardless of the differences in thermal convection mode, dimensions, and geometric arrangements of a heater, as confirmed by comparison with reference data. Additionally, the ignition threshold of temperature can be predicted if the external heating power is known, and it is useful to assess the fire risk.

Increasing the Metal Heating Efficiency in High-Temperature Units

This research paper delves into the improvement of the thermal modes of metal heating in the heating wells and it evaluates the metal heating modes in high-temperature units that affect the quality of products. Consideration was given to the main factors that affect the production cost, namely, slag consumption and conventional fuel consumption at different heating temperatures and metal holding times. The described calculations can be used in industry to improve the production process and reduce the cost of production. The research topic relating to metal heating modes in heating wells is relevant in the context of increasing the efficiency of the production of metal products and reducing production costs. The main problem is the instability of thermal processes in heating wells under variable technological regimes. The purpose of this study was to improve the thermal modes of metal heating in heating wells in order to increase production efficiency and reduce costs. The effect of the technological process delays on thermal processes in heating wells has been studied. To analyze thermal processes in heating wells, a calculation method was used that enabled the assessment of the effect of the changed technological regimes on metal heating indices. The calculation of the thickness of the burning-out crust can be used to preemptively control the metal heating process and prevent the dissection and oxidation of sub-crustal gas bubbles. It will help avoid the formation of such defects as the torn edge and reduce the amount of melted metal, as well as reduce the consumption of slagged metal. The obtained results can be used in the production of metal articles for further research to improve the technological regimes of metal heating in heating wells, in particular, to take into account the influence of other factors on thermal processes and to study the possibilities of using the latest technologies to increase the efficiency and competitiveness of production.

Design-oriented dynamic model of deployable fin under time-varying elevated temperature environment

AbstractCoupling of clearance joint and harsh aerodynamic heating environment is an inevitable nonlinear factor in folding mechanism of the fin of high-speed aircrafts that remarkably modifies natural frequencies and modes of vibration from the initial design state. However, accurately predicting dynamic properties of deployable fin with full consideration of these effects is not common industry practice. A practical semi-analytical model based on Hertz contact theory and ESDU-78035 model is proposed in this study to investigate high-temperature connection stiffness of local hinged–locked mechanisms. Material property degradation and clearance variation caused by thermal expansion are comprehensively considered and quantified in this model. Vibration characteristics of the assembled deployable fin are then solved using finite element method (FEM). The real-time evolutionary process of thermal mode of the fin is discussed. And natural frequencies of fixed-value and time-varying connection stiffness are compared. The simulation results of this study demonstrate that the relative error of structure temperature between the sequential approach and fully coupled simulations is less than 6.98%. The connection stiffness (slope of the load-displacement curve) of the folding mechanism under high temperature conditions decreases by 3.52%, and the variation is mainly caused by the degradation of the elastic modulus of the material, while the clearance change due to the thermal expansion has no significant effect on the slope. The natural frequency of the deployable fin exhibits an inverse correlation with the temperature change trend, and the first three frequencies decrease by 1.67, 7.75, and 16.28 Hz compared to the initial value, respectively.

Synthesis, characterization, DFT calculations and biological activity of new Schiff base complexes

Schiff bases ligand (HL) was produced by condensing 4-aminobenzohydrazide with N-(4-chlorophenyl)-2-(4-formylphenoxy)acetamide. Cobalt (II), nickel (II), and copper (II) acetate and ligand are reacted to form 1:1 complexes. By using electronic spectra, magnetic susceptibility measurements, infrared data from 1H NMR, and XRD studies, the ligand and its metal complexes have been characterized. According to the spectrum data, the ligand functions as a monobasic bidentate, coordinating with the nitrogen atom of azomethine (−CN−) group and the oxygen atom of carbonyl group in enol form. An octahedral structure has been proposed for Co(II), Ni(II), and Cu(II) complexes according to magnetic and electronic spectrum analysis. Using the DFT method, the computational investigations of the ligand and its metal complexes showed the bond lengths, bond angles, and quantum chemical parameters. To determine the thermal stability and mode of thermal degradation of hydrazone ligand and its complexes, thermogravimetric analysis was approved out on the samples. Two calculated method, Horowitz-Metzger and Coats-Redfern, were used to calculate the characteristics of the composites' thermal degradation mechanisms at each step, including their breakdown kinetics. The ligand and its complexes were investigated for their cytotoxicity in vitro compared to human amnion (WISH) and epitheliod carcinoma (Hela). The Ni(II) complex showed highly inhibition against (WISH) growth (IC50 = 18.28±1.8 μM) with relationship to the produced chemicals and other common medications. The interaction between the ligand and its complexes with the genetic tumor (3hb5) receptor was examined using docking experiments.

Procedure for simulating radiators of liquid cooling systems of avionics

Setting the problem. Analysis and assessment of the thermal mode of radioelectronic equipment (RES) in modern radioelectronic equipment is the most important task that is solved at the stage of design and development of the future device. Therefore, the choice of cooling system for heat-loaded structures is an integral component that must be solved in the early stages of design. The use of a modern set of computer-aided design tools (CAD) throughout the entire process of creating RES allows you to take into account all possible problem areas without resorting to the manufacture of a layout and prototype. Modeling of thermal characteristics and heat exchange processes provides for modeling procedures and ensuring the thermal regime mainly at the stage of design and topological design. At the same time, the analysis of thermal characteristics, as a rule, carried out after solving any design synthesis problem (placement, layout, selection and development of block structures, racks, etc.), if the modeling results are unsatisfactory, the design changes. Thus, in order to reduce time costs and reduce the iteration of the design process, it is necessary to solve the issues of ensuring the thermal regime in the early stages. Most often, the problem can be solved by increasing the area of the heat-emitting surface (radiator), but in some cases there is a need for additional cooling, in our case, additional use of liquid cooling. This is the reason for the relevance of the development of the methodology for modeling radiators of liquid cooling systems of the RES. Purpose. Present the methodology for simulating radiators of liquid cooling systems of the RES, the reliability of which could be confirmed by the results of analytical calculations and data of a full-scale experiment. Results. A mathematical statement has been formed, a modeling technique has been proposed and procedures for optimizing the cooling system have been implemented. Based on the developed 3D model of a radiator with a liquid cooling system, multivariable analysis procedures are implemented using modern computer-aided design tools. The liquid cooling system was optimized using modern software modeling tools, in particular the Solidworks Simulation program.

Observation of thermal acoustic modes of a droplet coupled to an optomechanical sensor

The bulk acoustic modes of liquid droplets, well understood from a theoretical perspective, have rarely been observed experimentally. Here, we report the indirect observation of acoustic vibrational modes in a picoliter-scale droplet, extending up to ∼40 MHz. This was achieved by coupling the droplet to an ultra-sensitive optomechanical sensor, which operates in a thermal-noise limited regime and with a substantial contribution from acoustic noise in the ambient medium. The droplet vibrational modes manifest as Fano resonances in the thermal noise spectrum of the sensor. This is among the few reported observations of droplet acoustic modes and of Fano interactions in a coupled mechanical oscillator system driven only by thermal Brownian motion.

Non-destructive evaluation of internal cracks in glass fiber reinforced composites using the laser shearing interferometry method

Laser shearing interferometry is one of the new methods of non-destructive testing, which is based on the interference of monochromatic waves reflected from the surface of the sample. This method can evaluate the entire surface of the sample with high accuracy and speed, by directly measuring the out-of-plane displacement gradient. In this paper, the possibility of detecting subsurface cracks with various lengths and angles in composite samples has been investigated using the shearing method and thermal stimulation system. To this aim, artificial and controlled cracks of different lengths and angles were created in the manufactured composites. After validating the performance of the shearing arrangement, two radiation heat sources were used to apply the load on the samples. The effect of loading size variables, shearing size and direction, crack length, and their angle on the quality of the results was investigated. The results show that the change in loading size plays a more important role than the change in shearing size in correct crack detection. To achieve the best results in crack detection on the selected samples, optimal loading in thermal mode equal to 12 and 15 seconds from the front of the sample was obtained. Moreover, the optimal size of the shearing in the examined composite samples was estimated to be about 10% of the width of the image recorded by the camera. Using the optimized values, all subsurface cracks were identified.

Comprehensive Chemical Cleaning of Flue Gases of Thermal Waste Treatment Plants Using a Catalytic Filter

The efficiency of integrated gas emissions treatment in thermal waste treatment units from dust particles and fossil sour traces of SO2, HCl and HF, as well as volatile organic compounds (VOCs) and dioxins at 300–400 °C of the gas mixture with a ceramic gas filter with aluminosilicate fibers added with catalytic MgCr2O4. The efficiency of sorption purification of tail gases from SO2, HCl and HF during the test period was 79–90 %, which depended on the supply of slaked lime to the catalytic filter to prevent catalyst deactivation. Thermal mode of chemical refining (300–400 °C) provided effective catalytic purification from VOCs, CO, and dioxins in combination with the chemisorption recapture of catalytic poisons and dust, preventing neither sorbent degradation nor damage to the catalyst.

Features of the resistive response to ozone of semiconductor PdO sensors operating in thermomodulation mode

This work is dedicated to the issue of increasing the selectivity of semiconductor PdO sensors in case of ozone detection. Thin PdO films were obtained using thermal sputtering of Pd and its subsequent oxidation. We characterised the obtained material using X-ray diffraction analysis and optical spectroscopy. We studied the gas-sensing properties of thin films in the mode of periodically changing temperature. The use of the thermal modulation mode allowed discovering the extremes of the resistive response of the PdO sensor in ozone, which helped to increase the selectivity of the sensor while detecting this gas. We suggested a possible mechanism of ozone chemisorption, which determined the specific form of the thermally modulated PdO response. The studies of the resistive response of PdO sensors under the conditions of ultraviolet illumination confirmed the suggested mechanism of ozone chemisorption

Reliability control of a thermoelectric cooler with changes in ambient temperature

The paper presents the development of method of thermoelectric system reliability indexes control for providing thermal modesof radio electronic equipment, based on thermoelectric coolers medium temperature variation. A mathematical model for investigating influence of the environment temperature variation on the reliability performance of a single-cascade thermoelectric cooler at a given temperature level of cooling, thermal load, geometry of thermoelement branches for different characteristiccurrent operating modes is considered. The results of calculations of the basic parameters, reliability indices, dynamic characteristicsand the analysis of dependences are given for revealing the peculiarities of control processes. It is shown that decreasing the medium temperature at a given chiller design decreases the operating current, increases the cold-productivity, and decreases the time of reaching a steady-state operating mode for various characteristic current operating modes. The time to steady-state operation decreases from the minimum failure rate to the maximum cooling capacity at a fixed medium temperature. The minimum steady-state operation time is ensured in maximum cooling capacity mode. Reduction of such significant for control indices as the amountof consumed energy for different characteristic current operation modes, required heat dissipation capacity of the radiator, time of reaching the steady-state mode is noted. Analysis of research results has shown that it is possible to control indicators of reliability of a single-stage cooler of a given design by changing the medium temperature by changing the value of operating current. A change in the medium temperature of the thermoelectric cooler due to an external supporting device makes it possible to vary the reliability indices and to find a compromise between the reliability, dynamics and cooling capacity of the thermal mode support system.

A numerical study on performance efficiency of a low-temperature horizontal ground-source heat pump system

Exploitation of shallow ground and its low-grade heat potential is fundamental to designing 5th generation district heating and cooling (DHC) networks. Horizontal ground-source heat pump (HGSHP) systems are a common way to utilize shallow geothermal energy. Realistic estimation and prediction of performance of a HGSHP system and shallow ground thermal behaviour should consider the whole system including building heating and cooling load, heat pump and ground heat exchanger, and the ground. This should be accompanied by realistic atmospheric and ground conditions. In this paper, a three-dimensional coupled thermal–hydraulic model with realistic boundary conditions adopting a whole system approach is presented. Dynamic heat pump coefficient of performance (COP) that depends on seasonal variation of heating/cooling demand and ground conditions are also considered. Model validations are conducted against experimental and analytical results in literatures. The model is applied for evaluating a HGSHP system to support development of a 5th generation DHC network on a potential site in the UK. Several influencing factors, such as ground moisture transfer, building thermal load mode, buried depth of ground loops, and initial ground temperature profile are studied to assess performance efficiency of the HGSHP system and evolution of ground thermal behaviour in response to heat extraction or rejection into the ground. The results show that 5% of the monthly total heat demand of the site could be met by the designed HGSHP system, consisting of 200 U-shaped ground loops buried at the depth of 3 m and pure water as the heat carrier. Overlooking the ground moisture transfer or hyperbolizing the ground saturation would overestimate the load-carrying capacity of the HGSHP system. The HGSHP system is more efficient with a higher heat pump COP under the heating and cooling mode than under the heating-only mode. Predicted performance of the HGSHP system improves with buried depth of the ground loops. The results also show that a 1 ℃ increase in the undisturbed ground temperature could suffice up to 8% of the monthly total heat demand of the site.

Concerning the justification of the working characteristics and construction parameters of the bearing assembly of the upper support of the pellet furnace shafts

Problem. Metallurgical industry requires raw material for further steel production. One of the technological chain element is grid furnace, equipped with shafts, which hold the grid with raw product during heating. Insufficient cooling of the shafts provides the durability decrease and interruption of the technological process during the shafts’ failure. The article presents the results of research into the working conditions of the upper support shafts of the metallurgical furnace.
 Goal. The goal of the paper is to find the absolute thermal expansion of the shaft by means of thermal transient methods and identify the required bearing clearances to extend durability and reliability of the technological element. Results. Using the method of finite elements, the calculation of the thermal mode of operation of the part was carried out and the absolute values of thermal expansion under the condition of forced cooling were determined. Originality. Finite element analysis has been used to examine the necessity of bearing clearances correction as well as working regimes of steel construction. Practical value. To determine the cooling modes, experimental tests of the cooling system were carried out. Based on the results of working out the temperature modes of operation, attention is focused on the sufficiency of thermal clearances in bearing units and the operating modes of rolling bearings. In order to substantiate the working characteristics of the bearing assemblies, experimental studies of the effectiveness of the lubrication system and consistent grease were conducted.

Investigation of thermal mode of hot-rolling mill working rolls in order to improve the accuracy of calculating the thermal profile of their barrels’ surface

Thermal mode of the working roll barrel in a hot-rolling mill is a significant technological factor that affects the steel strip quality, its cross section, and durability of working rolls. A reliable calculation of the temperature mode parameters makes it possible to determine the thermal profile shape and the best profiling of the roll barrel surface, as well as to reduce defects in steel strip flatness. The most common is the balance model of roll thermal mode. Its accuracy is largely determined by thermophysical constants, in particular, the heat transfer coefficients of the rolls: contact – with the strip and convective – with cooling water. There are various data on the values ​​and methods for calculating these coefficients, but most of them do not take into account the presence of pauses in rolling rhythm of the finishing group of stands, the duration of which is significant. Failure to take this factor into account entails significant errors in calculations of the thermal mode. A passive experiment was carried out, during which surface temperatures of the working rolls’ barrels were measured using a thermocouple at several points along their length immediately after they fell out. Also, the parameters of steel strip rolling before roll change were determined: rolling rhythm coefficients, strip reduction in stands, water consumption for cooling rolls and some others. As a result, an empirical equation was obtained for calculating the contact heat transfer coefficient, taking into account the main technological factors. The use of refined coefficients for calculating the temperatures of the roll barrel significantly increased the accuracy of predicting the thermal mode, in particular, the thermal profile of the working roll, based on values ​​of the rolling parameters.

Optimization of Approaches to Analysis of Lignin by Thermal Decomposition.

The ratio of monomeric units is one of the main characteristics of lignin, which affects the possibilities and strategies for further processing. Pyrolytic and thermal desorption decomposition of lignins followed by mass detection of macromolecule fragments are the most common methods for determining the amount of lignin structural units. Two methods of thermal decomposition of lignin were studied: thermal desorption-GC/MS (TD-GC/MS) and pyrolysis-GC/MS (Py-GC/MS). It was noted that, when using different thermal decomposition modes, the composition of the products changes, which affects the accuracy of determining the amount of lignin structural fragments. This article investigated the influence of the sample weight, the thermal decomposition temperature, and the duration of the process in various modes on the quantitation of the lignin structural units. The optimal process conditions were established. It was shown that the DS-Py-GC/MS with cryofocusing, a sample weight of 0.2-0.4 mg, and heating from 50 to 400 °C at a rate of 120 °C/min are preferable. The HSQC NMR was used as a comparison method to obtain the content of the S/G/H units. The results showed the applicability of the proposed approaches to hardwood lignins close to native.