Preheater Research Articles

Experimental investigation of flame state transition in a gas turbine model combustor by analyzing noise characteristics

Hysteresis of flame transition from lifted (V-shaped) to flat form is studied in a gas turbine model combustor by using acoustic measurements in connection with infrared thermometry and visual recordings. The impacts of varying several parameters including the shape of the fuel injector, flow rates, confinement (i.e., combustion chamber), and air preheat on flame shape transition and the corresponding acoustic behavior are studied using experimental measurements. It is shown that the flat flame produces noise at two dominant frequencies (related to the acoustics and hydrodynamic instabilities), and these frequencies could be used for flame shape transition prediction from the V-shaped flame, which produces different frequencies. Time–frequency wavelet analysis of the generated noise shows highly non-stationary behavior with mode hoppings for both flame states. The results show that the flame state transition hysteresis is highly dependent on the parameters that change the details of flow near the baseplate, and in this way, the higher flow rates, air preheat, and round slit injector intensify the transition hysteresis. Also, the presence of the combustion chamber was shown to be very effective in reducing the studied hysteresis.

Exergetic and exergoeconomic evaluation of an SOFC-Engine-ORC hybrid power generation system with methanol for ship application

The SOFC-Engine hybrid system is considered suitable as a marine power system due to its impressive attributes, including high efficiency and effective adaptability to variable loads. Combined with the ORC system and methanol fuel, the system's efficiency and carbon reduction can be taken to the next level. This study introduces a novel solid oxide fuel cell (SOFC)-Engine-Organic Rankine cycle (ORC) hybrid power generation system that operates on methanol. Rigorous assessments were conducted utilizing energy analysis, exergetic analysis, and exergoeconomic analysis. These evaluations aimed to pinpoint precise strategies for enhancing system efficiency while curbing expenses. The results show that the power generation efficiency of the hybrid system is 61.86%, and the exergy efficiency was 58.06%. Notably, the air preheater and engine emerge as components causing substantial exergy losses. Through exergoeconomic analysis, the exergy cost distribution across all system parts was unveiled. The reformer's exergoeconomic factor registers the highest at 77.62%. Consequently, mitigating the exergy cost associated with the reformer holds paramount importance in augmenting overall system revenue. Remarkably, the engine incurs the highest cost of exergy destruction at 10.134 $/h. Overall, this research offers pivotal insights for optimizing component performance and driving cost reductions.

Performance of a BAPVT modules coupled TEHR unit fresh air system based on micro heat pipe array

Energy consumption for heating and cooling fresh air has become a major component of building energy consumption, and there is a growing focus on highly-efficient and energy-conserving fresh-air treatment technology. This paper presents a new fresh-air system based on a high-efficiency heat transfer element, the micro heat pipe array (MHPA). It consists of a novel air-cooled building attached to a photovoltaic/thermal module (MHPA-BAPVT) and a thermoelectric heat recovery unit (MHPA-TEHR). The system uses solar energy, photovoltaic power generation, and waste heat for fresh air preheating. A series of fresh-air systems were designed, constructed, tested, and analyzed. The results reveal that on sunny winter days, the temperature of fresh air flowing through MHPA-BAPVT modules can increase by 22.15 °C. The average thermal and electric efficiency of the MHPA-BAPVT modules was 12.16% and 7.10%, respectively, and MHPA-TEHR could exceed the upper limit of passive heat recovery technology, which could generate 1.25 kW of heat per 1 kW of input electric power. The maximum ratio of total heating power to the total power consumption of the fresh-air system reached 14.94. During a typical day in the winter season, solar preheating exceeded the fresh air heat requirement by 24.34%, and the excess heat provided 292.92 MJ for building heating demand. Comparing the electric heating fresh-air unit with conventional heat recovery, the former achieved nearly zero energy consumption during the winter season. During the transitional season, the system could provide 711.82 MJ of solar energy, which improved the indoor temperature. Finally, using the experimental data and meteorological parameters of Zibo, the annual heat and electricity benefits and reduced carbon dioxide emissions of the fresh-air system were calculated. The fresh-air system in this study can fully utilize solar energy for heat collection and power generation to reduce building energy consumption and can be applied widely.

Laboratory Study on Adhesive Ash Deposition Characteristics of Ammonium Bisulfate in Conditions Simulating an Air Preheater for Hard Coal Combustion

The ash blockage of the rotary air preheater is a serious problem of the coal-fired boiler that urgently needs to be solved, which is caused by the adhesive deposition of ammonium bisulfate (ABS) and the fly ash. A comprehensive experimental study was performed to investigate the adhesive ash deposition characteristics based on an experimental platform established. The influences of the gas temperature, the gas velocity, the mass ratio of the ABS to the fly ash (R), and the ash particle size on the ash deposition characteristics were mainly analyzed and discussed under different conditions. The experimental results indicate that the liquid ABS is the root cause of the ash particles adhering to the heat transfer elements of the air preheater. The experimental results indicate that when the gas temperature is in the range of 420–493 K, the ABS ash deposition intensity and the ABS adhesion rate both increase with the increase in the gas temperature. When it is 493 K, the ABS adhesion rates of the corrugated plate and the positioning plate both reach maximum values, which are 31.7% and 27.9%, respectively. With the decrease in gas velocity, the total ash deposition intensity, the ABS ash deposition intensity, the ABS adhesion rate, and the growth rate of the ABS adhesion all increase. The content of ABS in the fly ash is also an important factor. When R rises, the ash deposition intensity and the ABS adhesion rate increase significantly. The particle size of the fly ash has little influence on the total ash deposition intensity, but has a great influence on the ABS ash deposition intensity and the ABS adhesion rate. With the increase in the particle size in the range of 30.8–100 μm, the ABS ash deposition intensity decreases by nearly 50%, and the ABS adhesion rates of plates A and B decrease by about 43.9% and 49.6%, respectively. According to the study results, some effective measures can be taken to solve the ash blocking problem of the rotary air preheater, including using the steam air heater, optimizing the operation parameters of the soot blower, and inhibiting ABS formation.

Direct waste heat recovery from a solid oxide fuel cell through Kalina cycle, two-bed adsorption chiller, thermoelectric generator, reverse osmosis, and PEM electrolyzer: 4E analysis and ANN-assisted optimization

The present study investigates an innovative model for the utilization of redundant heat from a solid oxide fuel cell (SOFC). The proposed system comprises a Kalina cycle (KC), a two-bed adsorption chiller (AC), a thermoelectric generator (TEG), reverse osmosis (RO), and a proton exchange membrane electrolyzer (PEME). A parametric analysis is conducted to evaluate the impact of key variables on the performance of the system. Various metrics are employed, including energy, exergy, economic, and environmental (4E). The environmental analysis reveals that waste heat recovery from SOFC decreases CO2 emissions by 36.41 kg per megawatt output at the base condition. At a fuel (methane) consumption rate of 0.0743 kg/s, the system produces 2206.49 kW of power, 166.09 kW of cooling load, 404.68 m3/day of fresh water, and 18.04 kg/day of hydrogen with reported energy efficiency and exergy efficiency values of 63.91% and 51%, respectively. Besides around 60.55% of the overall exergy destruction in the entire system is attributed to the air preheater, afterburner, and water preheater of the SOFC. The system is optimized using a genetic algorithm (GA) in three separate optimization issues, aiming to minimize the total cost rate while maximizing other objective functions, such as exergy efficiency, freshwater production, and cooling load. A modern optimization model using artificial neural networks (ANNs) is employed to reduce optimization time. By considering the overall cost rate and exergy efficiency as the objective functions, the optimal point is achieved at 58.03 $/h and 59.92%, respectively. The optimum values of 120.99 $/h and 1346.30 m3/day for the objective functions of total cost rate and freshwater production, respectively, are obtained in the second issue. In the third optimization problem, the evaluated values at the optimal point are 272.6 kW and 70.69 $/h for cooling load and total cost rate, respectively. Sensitivity analysis indicates that the changes in current density significantly affect the exergy efficiency, cost rate, net power, and cooling load, while variations in the fuel utilization factor coefficient considerably influence freshwater production.

Improving the biodiesel combustion and emission characteristics in the lean pre-vaporized premixed system using diethyl ether as a fuel additive

This paper is a lab-scale experimental study of the impact of employing diethyl ether (DEE) as an additive to waste cooking oil biodiesel with Jet A-1 on the combustion as well as emission features of a swirl-stabilized premixed flame. First, waste cooking oil biodiesel with a volume fraction of 20% was blended with Jet A-1 and symbolized as W20. Then, diethyl ether with a volume fraction of 20% was blended with 20% biodiesel and 60% Jet A-1, symbolized as W20D20. The three test fuels (W20, W20D20 blend, and pure Jet A-1) were premixed with preheated air and pre-vaporized before being admitted to the vertical cylindrical combustor having an inner diameter of 150 mm and a length of 500 mm via a swirl burner (radial type) of 0.55 swirl number and 8 straight vanes with an angle of 45°. Local flame temperatures and emissions were measured and recorded at 350 °C of preheated air with a constant equivalence ratio (φ) of 0.85. According to the findings, a relatively wide range of flame temperatures was observed in the flame of the W20 blend, while the W20D20 blend had a flame temperature distribution very close to that of the Jet A-1. The W20D20 blend reduced UHC emissions by 69.6%, CO emissions by 61.4%, and NOx emissions by 12.5% relative to Jet A-1 at the combustion chamber outlet. Overall, adding DEE to biodiesel significantly impacts both combustion and emission profiles.

Progress in Research and Development of Solid Oxide Cells, Stacks and Systems at Forschungszentrum Jülich

The defossilization of the energy sector requires the transfer of sustainable, carbon-neutral technologies and processes into application. Along with the development of a global hydrogen economy, technologies that generate, store, distribute and use hydrogen and derivatives are particularly relevant. Considerable potential in this sense is offered by the solid oxide cell (SOC), which can be operated as a fuel cell (SOFC), as an electrolysis cell (SOEC) and reversible (rSOC). Forschungszentrum Jülich has been involved in the research and development of SOCs for more than 30 years. In addition to material and cell development, stack and system development and understanding degradation effects are among the main topics today.Recently, an rSOC system with an output power of 10kW in fuel cell mode and input power of 40kW in electrolysis mode was developed. Four SOC stacks, separated and surrounded by a total of five heating plates plus an air preheater at one end and a fuel preheater at the other end, form the Integrated Module of the system; each stack has 20 layers with an active cell area of 19x19 cm². A compact and optimized design could be realized, which achieves a system efficiency of 63.3 % and 71.1 % in fuel cell mode and electrolysis mode, respectively. The system has already been tested in stationary operation modes. Current developments focus on the operating strategy, in particular on the temperature control of the stack in fuel cell mode and during the transient operation of the system.With a focus on the SOC stack, progress was made both in the area of actual stack development and in the area of clarification and optimization of performance and lifetime relevant processes. The role of contaminants, foremost silicon species and sulfur dioxide in feed gases, was investigated to support technical applications. Headway was also made in applying advanced measuring technology like fibre-optic sensors for temperature measurements in air channels. Degradation processes were investigated both experimentally and simulatively in fuel cells as well as in steam and co-electrolysis operation. On the one hand, machine learning approaches were pursued to analyze degradational patterns in SOC stacks, utilizing a specifically consolidated and curated set of long-term experiments and EIS measurements. On the other hand, a multiphysical stack model was developed that allows the relevant physical processes within the stack to be analyzed individually and coupled and thus to optimize the overall operation of the stack.In the area of the development and investigation of cells and materials, the performance of the SOC in the fuel cell mode as well as in the electrolysis mode was in the focus. In addition to operation in steam and co-electrolysis modes, operation in pure CO2 electrolysis was also researched. On single cell level the degradation behavior in the different modes of electrolysis operation was investigated. Different alternative materials were examined both on the fuel side and on the air side as well. A hierarchical degradation model framework was developed that relates changes at the level of electrode particles to changes in electrode structure, resulting materials properties and overall lifetime-performance. Model-based diagnostic allows the extraction of model parameters from experimental data, model verification as well as identification and quantification of different degradation mechanisms.Overall, therefore, significant progress can be observed in the field of cell as well as in the field of stack and system development of SOCs in fuel cell, electrolysis and reversible operation at Forschungszentrum Jülich.

Investigation of multi-stage evaporation and wave multiplicity of two-phase rotating detonation waves fueled by ethanol

In this study, a numerical investigation based on the Eulerian-Lagrangian model is conducted to explore a rotating detonation engine (RDE) fueled by liquid ethanol. The focus is on examining the characteristic phenomena of the two-phase rotating detonation wave (RDW) caused by droplet evaporation and varying inlet conditions. To enhance the evaporation of liquid fuel, pre-heated air is used, and both liquid and pre-vaporized ethanol are simultaneously injected. The distribution of ethanol droplets reveals an initial concentration near the injection surface and accumulation in the fuel-refill zone. Here, liquid droplets gradually evaporate after absorbing latent heat from the surrounding gas. The subsequent interactions between the evaporating droplets and the RDW vary with the droplet size. For droplets with diameters of d0 = 5–15 μm, after being swept by the RDW, a secondary evaporation process occurs, leading to an enlargement of the width of the reaction zone. However, the chemical reactions still predominantly take place in close proximity to the detonation front. As d0 further increases, droplet evaporation persists in the post-detonation expansion zone over a long distance until the remaining droplets are fully evaporated and eventually burned in this region. The study also analyzes the extinction of rotating detonations and the emergence of new detonation waves resulting from local explosions and consequent shock collisions. It is demonstrated that variations in the diameter of injected droplets and inlet temperature can lead to different operating modes with varying numbers of RDWs.

Development Progress of a 70% Efficient Hybrid SOFC-I.C. Engine Hybrid System for Stationary Applications up to 1 MW

Flexible and dispatchable, high-efficiency power generation supplied with carbon-neutral renewable fuels is needed to help enable defossilization of the electric grid. Pressurized, hybrid SOFC systems fueled with hydrogen, biogas, or renewable natural gas can generate clean power at ultra-high efficiency. This presentation presents an update on the development progress of a full-scale, hybrid system that targets low cost (<1000 $/kW) and ultra-high efficiency (70%-LHV) distributed power generation for applications up to 1 MW. The system features mature, metal-supported SOFC technology and the system design, control, hardware integration, and demonstration activities are funded by the U.S. DOE ARPA-E INTEGRATE Program. Some of the more novel aspects of the system include the intermediate operating cell temperature (600°C) and internal reforming capabilities which enable excellent thermal management and effectively reduce air preheater duty by >60% over more conventional SOFC systems operating near 800°C. Pressurization of the system decreases area specific resistance (ASR) and increases stack power density, thereby lowering capital cost. The use of a gasified diesel engine converts the residual chemical exergy in the anode tail-gas from the SOFC to drive auxiliaries and produce net additional power. Furthermore, the syngas engine enables a simple engine after-treatment for achieving ultra-low engine emissions (NOx, CO, PM, UHC). Updates on critical hardware advancements around pressurized multi-stack, 30 kW fuel cell modules, low-speed high efficiency rotating equipment, and ultra-high efficiency power electronics are provided. Results from experimental testing, system design and layout, and demonstration test facility capabilities are presented and discussed. The presentation concludes with a techno-economic outlook for such power generation systems in various stationary applications, as well as comparison with competing distributed generation technologies, such as solar PV-battery systems, microturbines, stationary engines, and non-hybridized SOFC technologies. Figure 1

Influence of Temperature and Water Vapour on the High-Temperature Oxidation and Cr Evaporation Behaviour of High-Cr Alloys for SOFC Cathode Air Pre-Heaters

Chromium evaporation and oxide scale growth are among the key degradation mechanisms associated with Solid Oxide Fuel Cells (SOFCs). It is often underestimated how the cathode air pre-heater (CAPH) made of high Cr-containing alloys in SOFC systems can contribute to cathode degradation. This study examines the effect of exposure temperature and water content on both degradation mechanisms in Inconel 625, SS309 and AluChrom 318. For the influence of water content, samples of Inconel 625, SS309 and AluChrom 318 were isothermally exposed at 850°C in dry air and air containing 1%, 3% and 9% of H2O at a high flow rate for 168 hours. For the influence of temperature, samples of Inconel 625, SS309 and AluChrom 318 were isothermally exposed at 650°C, 750°C and 850°C in a 6.0 L/min air stream containing 3% H2O for 168 hours. The evaporated Cr (VI) species were collected using the denuder technique. The formed oxide scales were subsequently analysed using XRD and SEM/EDX. The results of the surface characterisation indicated that the oxide scales formed on Inconel 625, SS309 and AluChrom 318 at high temperatures were Cr2O3, (Cr,Mn)3O4 spinel and Al2O3, respectively.The results of this study show that Cr evaporation and oxidation rates were dramatically reduced at the lower temperature used for Inconel 625 and SS309. AluChrom 318 exhibited an increased oxidation rate with increasing temperature, but it demonstrated a reverse trend to the temperature dependent Cr evaporation compared to Inconel 625 and SS309. It was also found that the amount of Cr evaporated from an alloy solely depended on the partial pressure of Cr presented on the oxide surface. At 850°C, the total mass of evaporated Cr(VI) species was found as follows: Cr2O3 (Inconel 625) > (Cr,Mn)3O4 spinel (SS309) >> Al2O3 (AluChrom 318). However, at 650 and 750°C, the total mass of evaporated Cr(VI) species was found to be: (Cr,Mn)3O4 spinel (SS309) > Cr2O3 (Inconel 625) > > Al2O3 (AluChrom 318). The significant effect of water vapour on the three tested materials appeared to be the further enhancement of Cr2O3 evaporation. At 850°C, the amount of evaporated Cr2O3 from the alloys exposed at the same humidity level corresponded to the Cr partial pressure on the surface, as follows: Cr2O3 (Inconel 625) > (Cr,Mn)3O4 spinel (SS309) > Al2O3 (AluChrom 318). The water vapour slightly increased the growth rate of Cr2O3 and (Cr,Mn)3O4 spinel formed on the Inconel 625 and SS309 surface, respectively. However, no evidence of change in the growth rate of the alumina on AluChrom 318 under the influence of water vapour in oxidising atmosphere was observed for the tested period in this study. Figure 1

Development of an innovative high-performance poly-generation plant for efficient multi-level heat recovery of a biogas-powered micro gas turbine: Environmental and Multi-criteria analysis

Nowadays, the biogas-powered gas turbine cycles in poly-generation systems play a crucial role due to increasing fuel prices, declining renewable energy sources, and environmental concerns associated with fossil fuels. Concerning the high temperature of expanded gas, a novel high-performance poly-generation plant is achievable by intelligently selecting different subsystems. This paper presents a novel biogas-fueled poly-generation plant for producing electricity, refrigeration load, distilled water, and hydrogen simultaneously using multi-level heat recovery. An extended assessment of the devised plant output is performed based on energy-exergy, environmental, and exergoeconomic criteria, in which the plant’s gas turbine inlet temperature, preheated air temperature, air compressor pressure ratio, as well as turbine inlet pressure, are considered as variables. In the following, to demonstrate the advantages of using a Stirling engine, this study investigates two scenarios to reveal its superiority, and a bi-objective optimization is performed, where the objective functions comprise minimizing the poly-generation unit products cost and maximizing the sustainability index. When the plant is operated with a Stirling engine, the plant produces 986 kW of electricity, 137.5 kW of refrigeration load, 8.39 m3/h of distilled water, and 2.96 kg/h of hydrogen. In this case, the energetic and exergetic efficiencies of the proposed system are enhanced by 2.96% and 7.89%, respectively compared to non-Stirling engine mode. Also, the carbon dioxide emissions and sustainability index are ameliorated from 606.2 kg/MWh to 588.6 kg/MWh and from 1.47 to 1.5, respectively. In addition, the sensitivity analysis indicates that in a certain ratio of PRAC, the plant's performance reaches its optimal mode. Moreover, the unit cost of products and sustainability index are improved by 9.9% and 8%, respectively, compared to the base design case with the SE.

Experimental study on the ash deposition and heat transfer characteristics of a heat pipe air preheater

In this paper, a scaled-down air preheater for a heat pipe is prepared and a visualization experiment system for ash deposition is established. The local and global characteristics of ash deposition and the heat transfer performance of the air preheater are investigated, and the effects of parameters including the gas velocity and the ash concentration are discussed. Experimental results show that a loose ash deposition is formed on the fin of the heat pipe with test time. The ash deposition mass has a maximum at Row #2 and a secondary peak at Row #6 due to the enhanced flow disturbance. With increasing gas velocity, the mass of ash deposition on the windward side gradually decreases, but there is a mass peak on the leeward side. The effect of gas velocity on the mass of ash deposition in the heat pipe fins is severe on the windward side. When the gas velocity reaches or exceeds 10 m/s, the ash deposition mass on the fin is mainly concentrated on the leeward side (>80.1%). Furthermore, as the gas velocity increases or the ash concentration decreases, the total ash deposition mass in the preheater decreases, and the overall heat transfer coefficient increases. The descending range of the heat transfer coefficient over the test time decreases from 10.0% to 4.3% as the gas velocity increases from 6 m/s to 12 m/s and increases from 3.2% to 7.8% as the ash concentration increases from 23 g/m3 to 38 g/m3.

Performance of Regenerative Air Preheater of Pulverized Coal Fired Boilers

Abstract: The air preheater (APH) is the final heat trap in the boiler's flue gas path. Effective pre-combustion coal drying and efficient combustion in the boiler are required for APH to operate efficiently. The effectiveness of heat transfer in APH is significantly influenced by the characteristics of relative humidity and ambient air temperature (AAT). Relative humidity (RH) and air density are also impacted by variations in AAT, which in turn alters the heat capacity of the air. If there is insufficient reserve heat exchange capacity in APH, an increase in AAT will diminish the possibility of waste heat recovery. Additionally, a change in AAT will affect the power consumption of the fans and the leakage through various seals.

Statistical Analysis of Regenerative Air Preheater of Pulverized Coal Fired Boilers

Abstract: The data gathered from the field study and different parameter recorders connected to the data acquisition system of the distributed control system panel for measuring flow, pressure, and temperature are subject to typical systematic instrumentation measurement uncertainties with regard to the primary measuring elements, sensors, transducers, amplifiers, digital converters, and recorders, as well as the effects of the environment. The acceptability of data is statistically confirmed by taking into account the unpredictability of the inaccuracy in recorded parameters for temperature, pressure, and flow measurement. The statistical output on the measured and expected air flow through the APH (ma) in relation to different AAT (Tae) is summarized

Design, multi-aspect analyses, and multi-objective optimization of a novel trigeneration system based on geothermal and municipal solid waste energies

The study of multi-source energy systems, due to higher performance and producing various products, is an interesting subject. The current study designs a multi-source system including a gas turbine cycle with CH4 and municipal solid waste digester, a geothermal system with an organic Rankine, organic flash, and a double-effect absorption refrigeration subsystem to produce power, cooling, and heating loads simultaneously. The thermodynamic and economic analyses are utilized to estimate the system’s performance and multi-objective optimization has been applied to define the optimum state of the system concerning two scenarios. The results indicate that the system provides 423.4 kW net power, 384.7 kW heating load, and 106.3 kW cooling load with 39.28% exergetic efficiency and 6.67 years payback period. These values are improved to 664.9 kW net power, 446.5 heating load, 42.01% exergetic efficiency, and 6.05 years payback period at the best optimum scenario. The sensitivity analysis reveals that the air compressor’s pressure ratio mainly impacts the net power, heating load production, and net present value. The cooling load production and exergetic efficiency are mainly affected by the air preheater effectiveness variation.

Experimental and modeling investigation of partial oxidation of gasification tars

Among the methods to reduce tar emission, the partial oxidation (POX) of biomass gasification tars has been studied both experimentally at a pilot-scale and numerically. The gasification producer gas was obtained at a temperature of 800 °C in an air-blown fluidized bed with an equivalent ratio (ER) of 0.25. For the POX unit, two secondary ER values were selected: 0.05 and 0.10, with the option of pre-heating air or not. Multiple advanced analytical methods were employed to provide a detailed composition of the producer gas, tars and acid gases. The POX unit demonstrated the ability to reduce tar levels by 60 to 90% depending on the secondary ER (from 6.5 to 2.4 and 0.72 gtars/Nm3, excluding benzene). The lighter tars were almost completely eliminated. The permanent gases were barely modified while the light hydrocarbons (except C2H2) and benzene were significantly reduced. Consequently, there was a slight decrease in the lower heating value. These results were compared to an isothermal plug flow reactor model, which utilized a detailed radical kinetic scheme constructed from various sources to account for all the species measured during the experiments as well as soot mass yield. The model provided relatively accurate predictions of the hydrocarbon species variations, even though it did not consider the mixing between air and syngas at the inlet of the POX unit.

Design of Heat Pipe Air Preheater for 10 t/h Gas-Steam Boiler

This design is aimed at energy -saving and designed a heat pipe air preheat to recover 10T/H steam gas boiler flue heat waste heat, thereby increasing the efficiency of the boiler and reducing gas consumption. This article first introduces the thermal pipe, heat pipe heat exchange, and boiler thermal system, and then focus on the design and optimization of the heat pipe air heater. This design optimizes the thermal pipe specifications of the heat pipe air heater and the parameters of the fins. At the same time, the sealing structure, the fixed structure, and the airport structure are optimized. Subsequently, the UG software created a three -dimensional physical model model and rendering model, and finally proposed corresponding countermeasures on equipment corrosion, thermal pipe life and tube vibration problems. This design uses Excel software to make design calculation tables. Through input parameters, the results of the results of the number of thermal pipes can be obtained.

The impact of different methods of drying and preparation method on the basic chemical composition of hay

The paper presents the results of three different ways of storing the dried mass of hay: bulk, small bales and large roll bales, as well as the impact of three drying methods: natural in the field, artificial drying with cold air and drying with dehumidification (warm air). In the tested meadow in the first swath, the results of chemical analyses showed differences in the method of drying hay. Regarding the tested drying method, the content of dry matter (DM) had significant differences between the storage methods as well as all variants with pre-heated air drying, where the average value of DM was in the interval of 86.18-93.01%. The content of mineral substances for certain methods of preparation and drying ranged from 5.77% to 7.72% on average. The highest content of crude proteins was in all variants of artificial drying and it ranged from 98.6 to 165.7 g/kg DM and had a statistically significant difference. Both methods of artificial post-drying had a significant impact on the cellulose content (33.76% to 28.86%) compared to drying in the traditional way because postponing the mowing time increases the cellulose content. The drying method had a statistically high significant difference on the content of neutral detergent fibres (NDF) and acidic detergent fibres (ADF), while the method of storage had no major impact. Knowledge of changes in the quality of hay during the growing season is of particular importance form the aspect of ruminant nutrition and balanced rations. The amount and quality of obtained hay is significantly affected by the time of mowing, height of mowing, swath, fertilization, floristic composition and weather conditions during drying of the green mass.

Effect of Temperature and Water Content on the Oxidation Behaviour and Cr Evaporation of High-Cr Alloys for SOFC Cathode Air Preheaters

High temperature alloys are being investigated for use in cathode air pre-heater for solid oxide fuel cell systems because of their high thermal conductivity, formability, manufacturability, and superior mechanical properties. However, it is well-known that high temperature alloys often contain a high concentration of Cr which presents a risk of evaporation and contaminating the cathode of the solid oxide fuel cell (SOFC). The oxidation and Cr2O3 evaporation mechanisms of the alloys including alloy 625, SS309, and alloy 318 have been investigated by varying temperatures and water content of the exposure atmosphere. For the influence of water content, the alloys were isothermally exposed at 850 °C in dry air and air containing 1%, 3% and 9% of H2O at a high flow rate for 168 h. For the influence of temperature, the alloys were isothermally exposed at 650 °C, 750 °C and 850 °C in a 6.0 L/min air stream containing 3% H2O for 168 h. The results of this study show that Cr2O3 evaporation and oxidation rates were dramatically reduced with decreasing temperatures for alloy 625 and SS309. Alloy 318 exhibited a decreased oxidation rate with decreasing temperature, but it demonstrated a reverse trend to the temperature-dependent Cr2O3 evaporation compared to alloy 625 and SS309. The major effect of water vapour on the three tested materials appeared to be the further enhancement of Cr2O3 evaporation.

겨울철 난방에너지 절감을 위한 이중외피형 태양열 집열시스템 설계 조건별 성능 분석

Double-skin facade (DSF) consists of two or more layers between which air flows. DSF can be used as a passive system by harnessing natural ventilation and preheating effect for heating, cooling, and ventilation. It can also be used with an active system either by simply alternating the passive mode with the existing active systems. Based on the capability of a DSF in providing preheated air by solar heat gains, this paper proposes a DSF-inspired solar heating system (hereinafter, the double-skin solar heating system) for integration into a building’s active system. This system warms up the air inside the DSF cavity and delivers the preheated air into an air-handling unit (AHU). We examined the architectural and material parameters of the system and analyzed the energy performance to quantify the benefit of such a system. For parametric analysis, a case study of a medium-sized office building was set up where the double-skin solar heating system was installed, and the geometry and thermal properties of the system were investigated. The parametric analysis demonstrated that the width of the double-skin solar heating system is the most influencing factor.