High Temperature Resistant Materials Research Articles

Experimental system and method of aerobic thermal environment simulation based on laser heating

Considering the superior luminous intensity characteristics of lasers, a thermal simulation platform employing laser-induced heating in an aerobic environment was developed. Achieving a uniformly distributed flat-topped square laser beam output was facilitated through optical fibre bundling techniques, while precise control over laser power output was attained through current modulation. Utilising the aforementioned system, thermal shock simulation experiments were conducted in an aerobic environment, subjecting two types of high-temperature-resistant composites, namely C/C and C/SiC, to temperatures up to 1800 °C. These composites were lightweight, heat-resistant materials designed for hypersonic vehicle applications. The results show that the system and method can be used to simulate high temperatures, rapid temperature increases, and thermal shocks on C/C composite materials, with minimal variation in the coupling coefficient under aerobic conditions. The system and method can also provide key technology support for thermal-force-oxygen coupling testing of high temperature resistant materials.

Testing Framework of Polyimide-Based High Temperature Resistant Composite Materials for Aerospace Applications

기 정립되어 있는 KS, ASTM, MIL 등의 시험규격은 일반적인 조건에서의 고분자섬유복합재 시험방법을 제시하고 있다. 본 연구에서는 대기권 이상의 환경조건에서 폴리이미드 기반 고분자섬유복합재가 경험할 수 있는 열특성 및 기계적 강도 파라미터를 포괄하는 특화 시험방법을 정리 및 제안하였다. 각각의 시험방법은 본소에서 특수기능용 고분자섬유복합재를 대상으로 다양한 환경조건 하 수행된 시험들을 거치며 정립되었다. 장비기반 시험방법 이외에도 본소에서 시험의 보조적 검증수단으로 점차 활용폭이 커지고 있는 복합재 내 열 전달 분석과 같은 컴퓨터 모델링의 예시를 소개하였다. 본 연구가 유관 시험, 공공 및 연구기관에서 우주항공용 폴리이미드 기반 고온섬유복합재 시험방법 연구동향 분석에 도움이 되길 기대한다.

Study on the tensile properties and deformation mechanism of high-temperature resistant nitrogen-containing nickel-based welding material deposited metal

This article uses a new type of nitrogen-containing nickel-based flux cored welding wire as the experimental material to study the tensile properties and deformation mechanism of the deposited metal from room temperature to 900 °C. The results show that the tensile strength gradually decreases with the temperature. The plasticity gradually increases, but the lowest value appears at 700 °C, which is the phenomenon of intermediate temperature brittleness. M23C6 carbides begin to decompose at 700 °C. More carbonitrides are precipitated within the crystal with temperature. In the low-temperature zone (T ≤ 600 °C), the main deformation mechanism is the unit dislocation a/2<110> cutting precipitation phase. In the medium-temperature zone (600 °C < T ≤ 750 °C), initiation of Orowan bypass mechanism for dislocations. In the high-temperature zone (800 °C ≤ T ≤ 900 °C), the slip and climbing mechanism of dislocation is the main deformation mechanism.

Thermally stabilized polyacrylonitrile/polyphenylene sulfide composite membranes for efficient emission control in harsh environments

In harsh and complex environments, the emission of polluted air poses significant challenges to traditional filtration systems. In contrast to conventional approaches which primarily involve the incorporation of antioxidants into filter materials, this study introduces a novel methodology. Here, we employed polyacrylonitrile (PAN) as a coating for polyphenylene sulfide (PPS) fibers. Furthermore, we innovatively utilized a needle punching process in conjunction with segmented heat treatment to manufacture PAN-PPS composite filter membranes capable of withstanding extreme environmental conditions. During the segmented heat treatment process, the molecular structure of PAN coating underwent a series of changes, ultimately transforming into a heat-resistant ring trapezoidal structure, providing protection for PPS fibers that are prone to oxidation, and thereby enhancing the structural stability of composite filter membrane. Experimental results demonstrated a significant improvement in the mechanical properties of PAN-PPS composite fabric after segmented heat treatment, with the tensile strength increasing by 71.7 % and the Young’s modulus by 91.6 %. Additionally, the flame retardancy and hydrophobic properties of composite membranes were significantly enhanced, exhibiting the excellent stability and better filtration performance in extreme environments. This approach not only addresses the challenges posed by incorporating nano antioxidants into the spinning process but also significantly enhances the high-temperature resistance of the materials. This enables PAN-PPS composite filter bags to effectively control the emission of polluted gases in extreme environments. Furthermore, the thermal treatment process of the PAN coating is easy to implement and cost-effective, providing a novel strategy for the development of extremely high-temperature resistant filtering materials. This makes it possible to explore the development of flexible, high-performance air filtering materials for extreme environments in the future.

Molybdenum-14Rhenium alloy—The most promising candidate for high-temperature semiconductor substrate materials

The development of emerging high-temperature-resistant semiconductor materials is of great significance for the stability of signals and the reliability of sensors during extreme probing processes such as deep earth and space. However, current reports only focused on the properties of the semiconductor materials, neglecting the high-temperature-resistant properties of subsidiary components, such as substrate. In this study, for the first time, the feasibility of the Molybdenum-14Rhenium (Mo-14Re) alloy as a high-temperature semiconductor substrate material was verified at five temperature points (25 ℃ (room temperature, Rt.), 100 ℃, 200 ℃, 300 ℃, and 400 ℃, respectively). The results showed that the hardness (2.8 GPa to 2.4 GPa) of the Mo-14Re alloy changed slightly during the temperature up to 400 ℃; the Mo-14Re alloy generated protective Mo6+ and Re3+ oxides at different temperatures, which enhanced its oxidation resistance; the thermal expansion coefficient of the Mo-14Re alloy was 5.04 × 10−6/℃ at 400 ℃, which can be perfectly adapted to semiconductor components, such as silicon, silicon nitride, and gallium nitride. Simultaneously, the Mo-14Re alloy combined appropriate thermal conductivity, making it the most promising candidate for a new generation of high-temperature semiconductor substrate materials. This study can promote the application of semiconductor materials in extreme environments, such as high temperatures. Concurrently, this study can promote the development of deep earth exploration and aerospace fields and guide the selection of emerging high-temperature resistant substrate materials.

Research of Stirling engines applications in vehicle, electricity, heating and cooling

Natural resources are becoming more and more scarce while pollution continues to increase. It is imperative to reduce emissions and improve energy efficiency. As an efficient, low-emission machine, the Stirling engine may be an answer on the road to emission reduction and improved efficiency. Stirling engine has been used in some areas, such as nuclear-powered submarine engines, combined heat and power and Stirling cryocoolers. However, there are still several problems that cannot be ignored in Sterling generators themselves. Stirling generators, characterized by high efficiency and potential for reducing greenhouse gas emissions, face challenges, including high material and assembly costs, complex waste heat treatment processes, and the need for durable, high-temperature resistant materials. Despite current limitations, ongoing research aims to enhance conversion efficiency, minimize size, and lower manufacturing costs, with promising applications in various sectors, including transportation and household energy, representing a significant stride towards green energy power generation in the future.

High powered output flexible aerogel triboelectric nanogenerator under ultrahigh temperature condition

Triboelectric nanogenerators (TENGs) have emerged as promising devices for harvesting low-frequency energy, but its application in high-temperature environments is limited. In this article, a flexible high-temperature resistant fiber substrate material was developed using needled felt and silicon aerogel. This material demonstrated exceptional resistance, withstanding exposure to a butane flame at approximately 1300 ℃ for a minimum of 10 min without experiencing burn-through. Following the application of electrodes and protective encapsulating, a high-temperature resistant silicon aerogel and fiber felts based triboelectric nanogenerator (HTFs-TENG) was successfully created. In addition, we achieved remarkable enhancements in the electrical output performance of the HTFs-TENG by precisely regulating its dielectric properties, resulting in an impressive increase in peak voltage from 17 V to 135 V. The current output increased from 1.4 μA to 6 μA. The HTFs-TENG demonstrated remarkable adaptability, operating effectively at temperatures as high as 275 ℃ and as low as approximately − 75 ℃. Moreover, it showcased an instantaneous power density output of 31.9 mW/m2 under a 100 MΩ resistance load. The HTFs-TENG displayed impressive electrical signal response capabilities at ultralow frequencies (≤1 Hz) across various temperatures and frequencies, positioning it as an ideal self-powered vibration sensor and temperature sensor for diverse generator applications.

An investigation of the thermal stability and mechanical properties of carbon framework materials hybridized by graphene and double benzene rings through combining first-principles calculations and classical molecular dynamic simulations

Carbon materials with a diverse hybridization of states have been studied for many decades due to their excellent customizable properties. In current work, a proposed carbon-based framework material named Double Benzene rings Graphene-based Frameworks (DBGFs) was studied. DBGFs was designed from the hybridization of 2D graphene (sp2) and 0D double benzene-ring molecules (sp2). Its thermal stability and mechanical properties were investigated using molecular dynamic simulation and first-principles calculation. The results showed that DBGFs had a relatively higher thermal stability up to 1557 K due to the interlayer cohesive strength of the double benzene rings. Furthermore, the concentration of double benzene rings directly affects the tensile and shear modulus of DBGFs, highlighting their significance as functional components. Additionally, an intermediate and metastable phase (named as “douben”) was observed under unidirectional compression of DBGFs-128 and other lower concentration of benzene rings, whereas the douben exhibits the slightly reduced thermal stability but improved mechanical properties in comparison to its original structure (DBGFs-128). In summary, these results of carbon materials show potential stratagem for designing high temperature and pressure resistant materials with hybridization of low dimensional materials in future.

Hafnium boride whiskers prepared by boro/carbothermal reduction for high-performance electromagnetic wave absorption

In this study, a chloride-assisted boro/carbothermal reduction method was employed to prepare HfB2 whiskers, aiming to address the challenges associated with large-scale preparation of HfB2 whiskers and the development of high-temperature resistant electromagnetic wave absorbing materials. When the precursors were mechanically stirred, the resulting mixture underwent calcination at 1450 °C for 3 h, leading to the formation of single-phase HfB2 whiskers. The as-synthesized HfB2 whiskers showed exceptional resistance to oxidation at temperatures up to 700 °C. The microwave absorption performance and mechanism of the HfB2 whiskers/paraffin composite were also investigated. The results revealed that the composite achieved a minimum reflection loss of −41.29 dB when the HfB2 whiskers content reached 80 wt%, while the widest effective absorption bandwidth of the composite reached 3.6 GHz when the HfB2 whiskers content increased to 82.5 wt%. This work presents a novel candidate for high-temperature resistant materials used in absorbing electromagnetic wave.

Experimental study on high-temperature resistance of alkali-activated slag concrete block masonry

The use of blast furnace slag improves resource utilization and supports the achievement of sustainable development goals. The use of alkali-activated slag cementitious material (AASCM) provides a new direction for improving the fire resistance of masonry structures. The masonry investigated in this study was alkali-activated slag crushed aggregate concrete masonry (ASCCM) in which aggregates of blocks and mortars were crushed and screened using AASCM paste specimens. The compression behavior of 12 specimens during and after exposure to high temperatures, specifically 300, 500, 600, 700, 800, and 900°C was investigated. The specimens were maintained under the target temperature for 2 h. The compressive strength and axial deformation of the specimen were recorded. The compressive strength losses during exposure to 300, 500, 600, 700, 800, and 900°C are 15.9, 20.3, 38.3, 43.9, 63.3 and 73.8%, respectively. The compressive strength losses after exposure to 300, 500, 600, 700, 800, and 900°C are 10.6, 15.8, 34.0, 37.2, 58.6 and 72.2%, respectively. The rate of loss in elastic modulus is greater than that in compressive strength. During exposure to 300, 500, 600, 700, 800, and 900°C, the loss rates of elastic modulus are 56.5, 74.4, 83.3, 86.3, 92.9 and 93.9%, respectively. After exposure to 300, 500, 600, 700, 800, and 900°C, the loss rates of elastic modulus are 49.6, 67.3, 77.5, 82.0, 90.7 and 94.5%, respectively. The peak compressive strain values are 9.9 and 11.1 times that at room temperature. Equations for calculating the compressive strength, elastic modulus, peak compressive strain, and ascending section curve of the stress–strain relationship with temperature were derived. The research results provide a new choice for high temperature resistant masonry materials, and provide theoretical basis and data support for the application of AASCM in masonry structures in high-temperature environments.

A novel salt-barrier method of preparation flexible temperature resistant full-component nanocellulose membranes

With the simplification and diversification of separation technologies, nanocellulose membranes have become widely used as insulating materials. Recently, study of nanocellulose membrane modification has become a hot topic. However, the application of nanocellulose membrane has been limited due to their inadequate heat resistance and flexibility. Herein, based on the pyrolytic and thermoplastic properties of cellulose, we innovatively introduced a salt barrier scheme to regulate the degree of hydrogen bonding and thermoplastic bonding between fibers. This was achieved by adding a salt barrier agent, NaCl, in the middle of the nanocellulose to prepare and obtain flexible, high-temperature-resistant nanocellulose film materials. The full-component cellulose films thus prepared exhibited high tensile strength (8 MPa), excellent flexibility (105 mN), high electrical breakdown strength (67 KV/mm), and volume resistivity meeting the standard of insulation materials (3.23 × 1013 Ω·m). This scheme adheres to the principles of low cost, green, non-toxic and non-hazardous, providing a brand new approach for the research and development of high temperature resistant cellulose membrane materials, which is of significant commercial value and industrialization prospect.

In-situ crosslinked polyetherimide/BNNS composites with ultrahigh charged-discharged efficiency at high temperature

High performance dielectric polymer composites for capacitive energy storage have been a hot topic in recent years. However, dielectric materials tend to breakdown at high temperature, and its charged-discharged efficiency is greatly reduced. Therefore, preparing high-efficient high-temperature dielectric material is the main challenge in this field. In this work, based on the synergistic effect of in-situ composite and controlled thermal cross-linking, the thermal conducting nano filler and crosslinking system composite has ultra-high charged-discharged efficiency at high temperature. It is proved that the addition amount of BNNS for the peak performance of this kind of composite is 10 vol% and the discharge energy density is 4.58 J/cm3 and the charged-discharged efficiency reaches 96 % at 150 °C and 500 MV/m. At 200 °C and 300 MV/m, these are 1.76 J/cm3 and astonishing 95 %. It is expected to be a candidate for a new generation of high temperature resistant dielectric materials.

Failure analysis on tube weldment cracking of a high-temperature carbon black air preheater

In this study, the failure analysis on weldment joining the medium-to-high temperature steel tube (the jointed materials are S30815 and HK40Nb, respectively) sections of a high-temperature carbon black air preheater was conducted. The root cause of the cracking is identified as metal dusting appearing in the high-temperature carbon black flue gas environment, as indicated by the result of the macroscopic analysis, the chemical composition analysis, the metallographic examination, and the corrosion product analysis. As revealed by the result, the metal was directly exposed to the flue gas due to the damage of the surface protective film (i.e., Cr2O3) of the stainless-steel tube weldment. The result suggested that elemental sulfur within the flue gas and overheating in the operation destroyed the oxide film. Under the effect of the high carbon activity in the flue gas, carbon atoms were driven to attack metals. The accumulated carbon particles arising from weld reinforcement promoted the failure of the weldment. To prevent metal dusting, it is recommended to increase the amount of water vapor in the flue gas for the reduction of the carbon activity, choose high-temperature resistant materials for the prevention of direct contact between the flue gas and the material, and improve the welding quality to prevent the flue gas from being disturbed.

A thin-walled mesoscopic hybrid slit-resonator metamaterial absorber

We propose a thin-walled mesoscopic hybrid slit-resonator metamaterial with excellent broadband sound absorption performance through developing an integrated material-structure- process-functional design method. The slit-resonator structure comprehensively utilizes the advantages of the porous material, the slit-type absorber and the Fabry-Pérot resonance unit, and exhibits unprecedented excellent large-broadband absorption capability. The ultra-thin walls ensure the high-porosity of the entire structure, and the narrow channel is equivalent to a designable porous medium, which can ensure excellent broadband absorption performance in the middle- and high-frequency ranges. As the challenging in fabricating of ultra-thin large-size walls, a ceramic-containing high-temperature resistant material is employed, and a 3D printing process with a special preheating-preservation-cooling cyclic heat treatment is accordingly developed. Through the joint development of materials and processes, the high-precision preparation of large-size and ultra-thin shell structures is realized. In addition, by embedding a few Helmholtz resonant units into the designed absorber to generate discrete low-frequency absorption peaks, the lowest absorption frequency is further reduced to 1/5 of the original one. The average absorption of absorber reach 0.8 above 50 Hz and 0.85 above 200 Hz, the thickness is reduced to 1/39 of the lowest absorption wavelength, which is only about 1/10 of the absorber used in traditional anechoic chambers.

Time-dependent creep analysis of ultra-high-temperature functionally graded rotating disks of variable thickness

Functionally graded materials (FGMs) are high temperature-resistant materials that can simultaneously maintain metallic tenacity and anti-corrosive properties. Nevertheless, using FGMs during a multi-year service life at ultrahigh temperatures is crucial. Hence, the time-dependent creep response of variable-thickness rotating disks made of FGM is investigated. Four different disk profiles of linear, concave, convex, and uniform are considered. The material's creep properties are defined by the Bailey-Norton creep law. Loading is a rotation-based mechanical body force and a uniform temperature throughout the disk. Simultaneous solution of equilibrium, stress-strain, and strain-displacement equations yields a non-homogenous differential equation containing variable and time-dependent coefficients. In an attempt to optimize the computation cost, Bat and Fish algorithms were used to optimize the initial strain presumptions. Semi-analytical solution of this differential equation gives radial and circumferential stress histories and displacement histories. To confirm the solution method, initial thermo-elastic radial stress, and the effective stress history are validated with the existing literature; there is a good agreement between the results. In addition, the finite element software ABAQUS was used to model the FGM disk thermo-elastic behavior, and the result was compared with the semi-analytical solution results. This study emphasizes the significance of accounting for creep effects in the design of FGM rotating disks, as remarkable changes in their displacements and stresses occur over time. This study emphasizes the significance of accounting for creep effects in the design of FGM rotating disks, as notable changes in their displacements and stresses occur over time.

Elucidation of the crystallization behavior and the thermodynamics property of CuO/Bi12SiO20@ SiO2-B2O3-Bi2O3-CuO glass-ceramics

Glass has good friction, lubricating properties, and great thermal stability, which has already made it to be widely used as excellent friction resistance and high temperature resistance materials for mechanical processing, and many other applications. In this study, SiO2-B2O3-Bi2O3-CuO (SBBC) system glasses were prepared via cooling the high temperature melt. The nucleation and crystal growth kinetics of SBBC system glasses were analyzed by thermogravimetric analysis and X-ray diffraction And then the value obtained was further analyzed by Gaussian fitting to give the temperature–time–transition (T–T–T) curve of SBBC system glasses under non-isothermal heating conditions. The crystallization kinetic parameters including the crystallization apparent activation energy (Ep) and the crystallization index (p) were also measured by the Ozawa and JMA methods (i.e. Ep1 = 116.4 kJ/mol, Ep2 = 50.1 kJ/mol, p1 = 3.7, p2 = 3.2). The effects of time(holding for 60 min), temperature (500 °C) and the phase of the precipitated crystal on the crystallization rate curves of SBBC system glasses were established. Furthermore, the crystal precipitation process of SBBC system glasses was verified by the typical crystal structure presented in scanning electron microscope (SEM) images, which successfully elucidated the working mechanism of the lubricating glass in high-temperature metal devices. The measurement of contact angles of the soften glass as well as the SEM-EDS analysis indicated that the early crystallization of SBBC glass has negative effect on the lubricating properties.

Study on the stability of high solid content polyether‐ether‐ketone aqueous suspension

AbstractCarbon fiber (CF) reinforced polyether‐ether‐ketone (PEEK) composite is found extensive application in various industries. Efforts have been made to enhance the interfacial binding between the resin and fibers. Herein, we report a green CF surface modification suspension coating method that could resist high process temperature by optimizing the stability of the aqueous suspension, which contains PEEK resin particles and a mixture of sodium dodecyl sulfate (SDS) and polyethylene glycol monostearate (stPEG). The optimized suspension (PEEK: SDS mass ratio= 5:1) that can meet around 500°C process requirement was then used to improve the physical interfacial binding between CF and PEEK. Based on the suspension colloidal stability, the process was optimized by tensile tests of the CF/PEEK monofilaments. The results show that the colloidal stability of the PEEK aqueous suspension with a total solid content of 20 wt.% containing stPEG‐SDS (stPEG: SDS mass ratio= 1:2) surfactant blend (PEEK: stPEG‐SDS mass ratio= 5:1) reached the optimum at a stirring rate of 750 rpm. The maximum tensile strength of the CF/PEEK monofilaments reached ~4.968 GPa at a coating diameter of 8.54 μm. This PEEK aqueous suspension provides a non‐toxic, environmentally friendly and high temperature resistant aqueous material to produce high‐performance fiber reinforced PEEK composites.

Joining C/C composite in a few seconds using refectory high entropy alloy fillers via spark plasma sintering

C/C composites were flash joined with ZrHfNbTa and TiZrHfTa refectory high entropy alloy fillers using spark plasma sintering within a short time frame of 16 s. The influence of different fillers on the joint morphology, shear strength at room temperature, and fracture behavior was investigated. The results indicated that the ZrHfNbTa filler completely transformed into carbide after flash SPS joining for 16 s, while the TiZrHfTa filler exhibited a (Ti-Zr-Hf-Ta)C phase, along with a small amount of TiTa rich alloy phase in the central area. The shear strengths of the obtained C/C composite joints using ZrHfNbTa and TiZrHfTa fillers at room temperature were close, with value of 16.0 ± 2.4 MPa and 14.1 ± 2.0 MPa, respectively. This work introduces a novel and flexible processing approach for joining high temperature resistant materials.

Study on cross-scale temperature effect and damage failure evolution constitutive model of phthalazine ether sulfone ketone

Poly(phthalazine ether sulfone ketone) (PPESK) is a new type of thermoplastic resin materials with high temperature resistance and corrosion resistance. However, the failure evolution regularities of PPESK at different temperatures still remain poorly understood, which greatly limits the application of this composite. Therefore, quasi-static tensile/bending tests and microscanning microscopic characterization were used to study the multi-scale failure constitutive equation of PPESK. Based on cross-scale experimental observation methods, the spatial damage morphology of materials at different temperatures is explored, and the temperature boundary effect of PPESK is proposed to reveal the failure and failure mechanisms of materials in a wide temperature range. The initiation and evolution of pores at the micro scale of PPESK and the cumulative damage caused by craze propagation and cracking are essential factors of material failure, which also exhibit strong temperature sensitivity. The specific manifestation is the high-temperature viscous flow effect of the resin at the micro scale, as well as the gradual evolution trend of quasi-brittleness and viscoelastic-plasticity between the 295 K–472 K temperature range in the macro performance, which increases its plastic deformation ability by 1–5 times. Specifically, the mechanism of cross-scale micro-pore initiation and crack propagation was introduced, and a cross-scale, fully three-dimensional failure damage evolution constitutive model of PPESK was constructed for the first time in a wide temperature range. The secondary development of the material constitutive model in the finite element software was carried out, and the construction of the constitutive equation of the PPESK cross-scale failure was completed. Finally, the mapping relationship between the material's crack failure form, mechanical behavior, and the constitutive model was further verified by experiments. It is established that the proposed PPESK multi-scale failure constitutive model enables one to effectively describe the complex mechanical response and failure law of thermoplastic resin materials under temperature gradients. Moreover, this theoretical tool is promising for the design of independently controllable high-temperature resistant thermoplastic resin materials, thereby providing important guidance means for engineering applications.

Thermal performance enhancement of a red-hot air furnace for a micro-scale externally fired gas turbine system

Externally-fired gas turbine (EFGT) has been considered an option in variable combined heat and power energy systems. The key elements in such systems are the high-temperature heat exchangers (HTHE), in which the working fluid (typically air) is heated by flue gas. Since both flows are separated, the solution is considered advantageous for utilization of biomass featuring high levels of particulate matter emissions. An increased interest in these devices has therefore been observed along with the development of small-scale CHP units utilizing locally available biomass. The effectiveness of HTHE, along with the inlet turbine temperature, appears to be one of the main factors influencing the efficiency of EFGT-based systems. Numerous studies on the HTHE designs have been carried out, basically focusing on the use of high-temperature resistant materials to provide safe conditions for long-term operation under elevated temperatures. There is a lack of research considering other methods to improve the effectiveness of the HTHE. The paper presents the analysis of thermal performance of the laboratory-scale 20 kW red-hot air furnace to demonstrate the HTHE effectiveness enhancement by adding water to airflow. The experimental results showed a significant increase (by almost 45%) in the heat exchanger effectiveness for the case of ∼10%wt. water addition. This is due to the enhanced heat capacity of a cooling medium and its absorption properties that results from the steam content. The proposed method for effectiveness increment appears to be beneficial to compensate for the low effectiveness of air-to-fumes tube HTHE.