Required Heat Input Research Articles

Heat input optimization for the ignition of self-sustained smoldering remediation of contaminated soils using concentrated solar power

In this paper, we explore the industrial-scale feasibility of using concentrated solar power (CSP) as the heat source in the smoldering remediation of petroleum-contaminated soil. Approximately 5 L soil samples were loaded in a narrow-channel reaction chamber and heated from the bottom with CSP to identify the required heat input to achieve ignition. Both petroleum and granular activated carbon (GAC) were used as combustible media. GAC was selected as a cleaner-burning alternative to petroleum and could emulate petroleum-contaminated soil at a mixture of 40 g GAC per kg pool sand on a 1.5 cm bed of GAC. This mixture of GAC showed robust ignition with a minimum power input of 240 W, which was slightly higher than the power input required to ignite industrially generated petroleum-contaminated soil. Preheat temperatures in excess of 300°C were achieved in most experiments, allowing for robust ignition of the smoldering remediation process. CSP was collected using parabolic reflectors 600 mm in diameter and was delivered to the reaction chamber with fiber optic bundles. Each solar concentrator delivered between 50 and 80 W to the reaction chamber, and four concentrators were required to reliably achieve the required power input.

Dual assistance of surfactants in glycerol organosolv pretreatment and enzymatic hydrolysis of lignocellulosic biomass for bioethanol production

This study investigated an innovative strategy of incorporating surfactants into alkaline-catalyzed glycerol pretreatment and enzymatic hydrolysis to improve lignocellulosic biomass (LCB) conversion efficiency. Results revealed that adding 40 mg/g PEG 4000 to the pretreatment at 195 °C obtained the highest glucose yield (84.6%). This yield was comparable to that achieved without surfactants at a higher temperature (240 °C), indicating a reduction of 18.8% in the required heat input. Subsequently, Triton X-100 addition during enzymatic hydrolysis of PEG 4000-assisted pretreated substrate increased glucose yields to 92.1% at 6 FPU/g enzyme loading. High-solid fed-batch semi-simultaneous saccharification and co-fermentation using this dual surfactant strategy gave 56.4 g/L ethanol and a positive net energy gain of 1.4 MJ/kg. Significantly, dual assistance with surfactants rendered 56.3% enzyme cost savings compared to controls without surfactants. Therefore, the proposed surfactant dual-assisted promising approach opens the gateway to economically viable enzyme-mediated LCB biorefinery.

Dynamic Modeling of a Solar-To-Hydrogen Flexible High Temperature Steam Electrolysis Plant

Sustainble hydrogen production for use as a renewable combustible fuel and clean chemical feedstock is an important objective as the world moves towards a renewable energy future. High temperature steam electrolysis is a promising hydrogen production technology due to its reduced electric input that is offset by heat input into steam generation and steam superheating. An option to provide this heat is to use concentrating solar thermal technology that can sustainably provide heat input while renewable electricity is used for the electrolysis reaction. In this work, a solar-to-hydrogen high temperature steam electrolysis plant is designed and dynamically modeled, showing continuous hydrogen production by utilizing supplemental heating and efficient recuperative heating from the electrolysis product streams. Through this design, over 90% of the required heat input for the process can by met by a combination of solar and recuperative heat. Additionally, the plant can flexibility operate by ramping down hydrogen production and through flexible heat integration, which intelligently integrates solar heat based on solar conditions. Smooth operation with flexible hydrogen production is demonstrated which decreases electrical input during on-peak grid times and also decreases the total supplemental heat load over the course of a day from 26.1% to 24.5%. In addition, by using flexible heat integration, the plant can increase its solar heat usage by 4.1% relative to a base case. Both options for flexibility show efficient use of solar thermal energy to sustainably and continuously produce hydrogen.

A solar thermal driven ORC-VFR system employed in subtropical Mediterranean climatic building

This paper investigates the configuration of solar thermal collector driven organic Rankine cycle (ORC) utilized to power air-conditioning system of the two-story office building in Paralimni, Cyprus, through a Variable-Refrigerant-Flow (VRF) system. The reason to choose this Mediterranean climate of Paralimni, Cyprus, is due to its higher dependency on fossil fuels compared to many other countries in the EU and with a high potential of harnessing solar irradiations and demand for air-conditioning (AC) loads. This location is categorized as warm temperate zones, subtropical climates and is placed in the subcategory of Mediterranean climates with humid winters and dry summers according to climatic zone, highly demanding for air conditioning. Based on the climatic data of the study area, this system can make an effective performance. Modeling the building and estimating the AC system power consumption is carried out in the DesignBuilder. Designing the organic Rankine cycle is done with EES. A solar hot water system is designed with TRNSYS to supply the required mass flow rate of water at the desired temperature of 95 °C. In this climate, the annual surface irradiation rate is 1,793 kWh/m2 whilst the AC energy requirement of a two-story building is 7,909 kWh. The employed ORC with an internal heat exchanger is designed with a constant output rate of 3.920 kW, which delivers a total of 8,154 kWh yearly. The required heat input of the ORC is supplied by a solar hot water system, employing evacuated tube collectors. The solar system consumes a 454 kWh auxiliary heating rate per year to deliver the desired mass flow rate and outlet temperature for the ORC. As a result, the designed solar-driven ORC delivers a net of (8,154 – 454) kWh = 7,700 kWh energy each year, meaning 7,700 kWh energy saving per year, equal to 97% of VRF annual energy demand. This amount of yearly energy saving yields 2,010 USD yearly capital saving as the reward of investment in this system, and defining a 20-year project, the implementation of this solar-driven power generation system at the end of the project's lifetime would save 25,049 USD.

Thermal Analysis and Testing of Different Designs of LaB6 Hollow Cathodes to Be Used in Electric Propulsion Applications

LaB6 emitters are commonly used in hollow cathodes that are utilized in electric space propulsion systems. In order to obtain necessary surface current emission densities of 1–10 A/cm2 for cathode operations, LaB6 emitters require temperatures above 1500 °C. Hence, the design for LaB6 cathodes presents thermal and mechanical challenges. In this paper, several design iterations for LaB6 hollow cathodes are presented and thermal analyses are conducted for each design. Temperature and heat flux distributions that are obtained from thermal analyses are investigated. The designs are evaluated according to the required heat input to the emitter, and the radiative and conductive heat loss mechanisms. In addition to the thermal analyses, experimental tests are conducted for different cathode designs and, based on these tests, various modes of failure are determined. Revising the cathode design and the material selection iteratively to eliminate the encountered failure mechanisms, a novel cathode design is achieved. Experimental tests of this novel cathode are conducted and current-voltage characteristics are presented for different mass flow rates and for discharge currents between 0.5 and 12 A. Tests and analysis results show that the selection of materials and design are crucial for a sturdy and long lifetime cathode.

CFD analysis of fixed matrix with glass refractory particle regenerator

The following paper presents work on the Heat Recovery System (HRS) which have been used constructively in modern industries to recover heat from the flue gases. The HRS are analysed and outcomes of various factors such as its permeability, length, D/dp ratio, and porosity of the model are studied. Various CFD simulations are shown for the results of thermal trait of model. It is hence implied that for thermal and flow simulations the modelled geometry in fluent is to be used. The CFD analysis starts with heating cycle by allowing the flue gases to enter the regenerator at the higher temperature (200 ℃) through the inlet of the regenerator bed for a cycle time of 10 mins thus charging the glass particle bed. Once the heating cycle is completed then the cooling cycle starts with the entry of air at ambient temperature at 27 ℃ for the cycle time of 10 mins regenerator entering in the counter flow direction. The simulations deduce that with the aid of Fluent software, various contours of velocity, pressure, turbulent kinetic energy and temperature are studied for regenerators of fixed bed length. The thermal efficiency of heat recovery form the fixed matrix regenerator with glass particles and D/dp ratio of 10 is calculated as 15%. This 15% increase in the thermal efficiency will improve the overall efficiency of the plant where these type of regenerators are used by 5–8% and decrease the total required heat input by 10–15%.

Eksperimentalno istraživanje mehaničkih svojstava zavarenih spojeva legura AA2024-T3 dobijenih zavarivanjem trenjem sa mešanjem

Friction stir welding is a promising solid state metal joining technique. It can be used to join AA2024-T3 metal plates which cannot be welded using normal fusion welding. Post weld joint efficiency depends completely on the proper selection of process variables as the required heat input for this process is not supplied by an external source but an internal function of the variables. Apart from the process variables tool pin shape also plays a vital role on the delivery of better weld strength. A comparative experimental analysis was done to understand the improvement in the post weld properties on the usage of non-cylindrical tool pin. In order to optimise major process variable for cylindrical as well as non-cylindrical tool pin geometries thermal study had been carried out and optimum heat input conditions were analysed for AA2024-T3 plates. Comparative analyses on friction stir weld joints were made qualitatively and quantitatively to understand the improvement on the introduction of noncylindrical flat faced pin in the tool.

☆Presented during the French Chemical Engineering Congress SFGP 2019, Nantes 15–17 October 2019.Energetic study of beech wood gasification in fluidized bed reactor under different gasification conditions

The thermodynamic study of beech wood gasification was performed in a pilot scaled fluidized bed reactor at different operation conditions, including temperature range from 600 °C to 900 °C, using CO2 and steam as gasification agents and sand and biochar as bed materials. The particularity of this study was the evaluation of energy consumption of biomass gasifier based on energy balance comparison in the same experimental set-up for different experimental conditions. The comparison between pyrolysis and gasification with CO2 showed that pyrolysis required less heat input (4.4 and 5.0 MJ/kgbiomass) than gasification (6.7 and 7.8 MJ/kgbiomass) at 800 and 900 °C respectively. Meanwhile the syngas CGE were higher for gasification (0.78) as the LHV values for syngas (12.2 MJ/kg). Temperature favoured CGE and syngas LHV increase, as it also increased process endothermicity. The presence of biochar as bed material increased the syngas LHV from 3.3 to 15.4 MJ/kg for CO2 gasification and from 3.3 to 15.1 MJ/kg for steam gasification. Both gasification agents provided similar values of CGE (>0.95) at 900 °C. From 600 to 900 °C the required heat input for steam gasification it was from 1.5 to 6.9 MJ/kgbiomass, meanwhile for CO2 gasification was from 4.1 to 7.1 MJ/kgbiomass. The results offer useful details that can help for future design of gasification experiments in fluidized bed reactors.

Development of a Fluidized-Bed Reactor for Oxidative Torrefaction of Biowastes

Torrefaction is considered as a method for producing biofuels with improved characteristics compared to those of the “raw” biomass (higher calorific value, moisture resistance, better grindability). The torrefaction process is an endothermic process that is usually carried out in a gaseous atmosphere in the absence of oxygen. To reduce the required heat input, it is proposed to employ the oxidative torrefaction and conduct the process in a fluidized bed agitated with flue gases containing less than 6% oxygen. Preliminary studies of the oxidative torrefaction of sunflower husks, including thermogravimetric analysis of the treated material, have shown that the heat treatment time for the biomass should be at least 5 min. A fluidized bed is a reactor with ideal mixing of the treated material where uniform treatment of raw material particles cannot generally be attained. To overcome this disadvantage of the fluidization technique and achieve the required residence time for biomass in a fluidized bed during a continuous torrefaction process, it was proposed to equip a torrefaction reactor with a series of vertical baffles spaced at 50 mm. These baffles induce a loop-like flow of the processed biomass from the inlet to the outlet of the reactor. To investigate the residence time for husk particles in the reactor, a tracer, which was colored to husk particles' color with a water-soluble dye which did not change the weight and size of the particles, was injected into the bed of uncolored particles. Tracer samples were taken every 30 s at the outlet of the reactor and were analyzed using a special procedure to determine the fraction of colored particles in each sample. This enabled us to gauge the time during which the colored particles injected into the fluidized bed reached the point of their discharge from the bed. Studies performed in a “cold” model of the reactor showed that a series of vertical baffles in the bed can provide the required residence time for biomass in a reactor including commercial reactors. Plates can provide the necessary biomass residence time in the reactor.

Effect of laser welding process parameters on dissimilar joints of AISI 316 and nickel 201

Abstract The dissimilar butt welding of nickel 201 and AISI 316 was investigated using 4 kW CO2 laser welding machine. The effects of welding power (2580 - 3420 W), welding speed (450 - 1150 mm/min), focal position (-1 to 0 mm), beam angle (84 - 96 degrees) and Beam offset (0 - 0.2 mm) on the welded bead geometry like depth of penetration (DP), bead width (BW), area of penetration (AP) and heat input (HI) were analyzed with Response Surface Methodology (RSM). The central composite design was used for this experimental plan. Mathematical equations were formed to find the required heat input and weld profile responses dissimilar butt welding process. Output responses reflect the results for mathematical models within the range of process parameters used. Numerical optimisation technique was used to identify the optimal condition region of all this laser welding process. It helps to achieve better process parameter combination for the controlled responses of this process. Depth of penetration is the most important output response to achieve the good dissimilar joint. The welding power and welding speed are the two factors which influencing more on the strength of dissimilar joint even though all the other three factors are involving. The beam angle does not show any considerable change on bead width and Fusion Zone Area (FZ) and also there is no significant influence of the beam offset on bead width. An optimization results were confirmed by experiments to validate values of the process parameters values found from RSM. In microstructure studies some delta ferrite is seen in the interdendritic region and also the solidification shows columnar grains. The tensile test results the fracture in the base metal which proves that the weld strength is good as expected

Active grain growth control with distributed heating

Microstructure affects the physical properties and behavior of materials. While metallurgists have long studied microstructure characterization and evolution, thermo-mechanical material processing to achieve a desired microstructure remains largely experience-based. This paper presents a distributed thermal control methodology for the microstructure evolution. We consider the problem of achieving a uniform microstructure, starting from a non-uniform initial distribution. This is a common goal in material processing, as uniform microstructure implies consistent macroscopic properties. To illustrate the approach, we consider an example process with a multi-zone micro-heater array controlling the grain growth of a copper thin film. Cascaded temperature and grain-growth models characterize the process dynamics – finite element method (FEM) models the temperature field in response to the heater input, which in turn drives the microstructure evolution through a biased Monte-Carlo (MC) model. The high order combined FEM/MC model is used as the validation “truth” model. For the control design and analysis, a simplified model is developed to only capture the essential trend in the full model. Using the simplified model and dividing the copper thin film into multiple spatial zones with measurable grain statistics in each zone, we obtain a nonlinear multi-input/multi-output control design model. Using the simplified model, this paper presents the development and comparison of three control methods: 1. Direct output feedback from the measured mean local grain sizes to the heater current. 2. Model predictive control (MPC) using a finite horizon optimization to compute the required heat input at each control step. 3. Inner-outer loop control with temperature as the surrogate input for the outer loop and using the heater current to achieve the required temperature in the inner loop. All three methods achieve uniform microstructure in grain growth in the higher order FEM/MC simulation. Direct output feedback is the simplest to implement, but has the slowest convergence. MPC shows fast convergence but requires model-dependent on-line optimization. Inner-outer loop demonstrates good compromise between model-dependence and rate of convergence.

GTA pulsed current welding of thin sheets of SS304 producing superior quality of joint at high welding speed

Thin sheets of austenitic stainless steel (SS304) are assembled using various pulse parameters of pulsed current gas tungsten arc welding. The sheets are joined with high welding speed for higher production rate, but the mean current is enhanced with higher welding speed for maintaining required heat input to get a sound joint. Application of pulsed current gas tungsten inert gas welding for joining of SS304 has been found advantageous in the form of production of weld joints with better mechanical and metallurgical characteristics. It has been observed that there can be elimination or lesser humping in weld joints. Undercut or dipped weld faces are also not found due to application of pulsed current. There is improvement of tensile strength and hardness by 12.5 and 12%, respectively. The enhanced tensile strength and hardness is justified through TEM micrograph showing presence of dislocation.

Steam reforming of tars at low temperature and elevated pressure for model tar component naphthalene

A process of pressurized gasification and power generation in a hybrid system of Solid Oxide Fuel Cell (SOFC) and gas turbine enables an efficient use of biomass. This process requires tar reforming in order to protect the SOFC from plugging. Tars must be converted at 5 bar absolute pressure (bara) while avoiding secondary steam reforming of methane in order to reduce the required heat input for the tar reformer. This can be realized at low reforming temperatures (<700 °C) where methane conversion is reduced due to chemical equilibrium. A laboratory-scale test rig is introduced, which enables an investigation of the steam reforming of the model tar component naphthalene at up to 5 bara. Deactivation of the nickel catalyst caused by coke formation was detected. Despite the reduced amount of free active centers on the catalyst surface, stationary naphthalene conversions are possible at temperatures between 600 °C and 700 °C. The lower the temperature, the more active centers are covered. For stationary conditions a hyperbolic approach for the reaction rate of steam reforming of naphthalene is developed and parameters for 650 °C and 700 °C are determined.

Predictive control based double-electrode submerged arc welding for filet joints

Double-electrode submerged arc welding (DE-SAW) is an innovative process to achieve the same metal deposition rate at reduced heat input. To maximally take advantage of this new capability, the heat input needed to produce acceptable welds needs to be reduced. A joint gap is successfully introduced to reduce the required heat input but it introduces variations affecting currents/heat input. To minimize the resultant variations in currents and resultant welds, the process is modeled and a multivariable predictive control algorithm is developed to control the currents at desired levels. Experiments verified the effectiveness of the resultant feedback controlled DE-SAW process.

Finite element simulation of a two-dimensional standing wave thermoacoustic engine

A finite element analysis has been performed on a theoretical two-dimensional standing wave thermoacoustic engine using the linearized thermoacoustic equations in the frequency domain. This analysis is used to obtain the stability curve of the thermoacoustic engine, which in turn is used to calculate the oscillation onset temperature difference across the stack. The results are compared with existing theory including the long-pore approximation, as originally derived by Rott et al. In addition, the time-averaged effects of the acoustic wave are obtained using weakly nonlinear thermoacoustic theory. This includes the second order time-averaged equations for energy, momentum, and continuity. The saturation amplitude of the acoustic pressure oscillation and the required heat input to sustain the oscillation is obtained. The theory allows for calculation of acoustic streaming patterns. The particle path calculations provide insight to the minor loss mechanism occurring at the interface between the stack and the free tube for low acoustic velocity amplitudes (laminar flow).

금형재료용 주철의 다이오드 레이저 표면경화처리에 관한 연구(I) - 금형재료에 따른 표면경화 특성 -

본 연구에서는 거의 모든 기반산업에서 필수적인 생산기술로 사용되고 있는 금형의 기계적 성질을 향상시키기 위해 고출력 다이오드 레이저를 이용하여 두 종류의 금형재료용 주철을 표면경화처리하였다. 우선, 구상흑연 주철인 FCD550 소재에 대하여 열처리 특성을 파악한 후, 편상흑연 주철인 HCI350 소재를 열처리하여 두 소재의 표면경화 특성을 비교하였다. 경화부의 경도는 두 시험편 모두 모재에 비해 3배 이상의 경도 상승을 보였지만, 재료에 포함된 흑연의 함유량 및 형상의 차이에 의한 재료의 열전도 도에 따라서 FCD550 소재에 비해 HCI350이 열처리하는데 있어서 더 많은 입열이 요구되었다.

Diffusion of gaseous products through a particle surface layer in a fluidized bed reactor

This paper examines a solid conversion process during hydrolysis and decomposition of cupric chloride in a thermochemical copper–chlorine (Cu–Cl) cycle of hydrogen production. Reaction rate constants and the time required for complete solid conversion are determined by a shrinking-core model. Diffusion of gaseous reactant occurs through a film surrounding the particle, after which the reactant penetrates and diffuses through a layer of ash to the surface of the unreacted core. The shrinking-core model for spherical particles predicts the reaction of gaseous reactant with solid at the particle surface, and diffusion of gaseous products through the ash, back to the exterior surface of the solid. The hydrolysis reaction is also analyzed with respect to chemical equilibrium conversion and required heat input. Effects of varying operating parameters are examined, including the temperature, pressure, excess steam, inert gas and hydrogen chloride (HCl) in the steam. At a temperature of 375 °C, complete conversion of CuCl 2 can be achieved by controlling the excess steam, operating pressure and inert gas supply. Addition of HCl in the steam supply increases the excess steam requirement for conversion of cupric chloride solid, and the upper limit for HCl concentration increases with temperature and inert gas composition. The addition of inert gas may also reduce the excess steam requirement, thereby reducing the heat requirement. These new results have valuable utility for equipment scale-up in the thermochemical Cu–Cl cycle of hydrogen production.

Open cycle traveling wave thermoacoustics: Energy fluxes and thermodynamics

In an open cycle traveling wave thermoacoustic engine, hot gas steadily flows into the hot side of the regenerator, replacing the hot heat exchanger as the primary energy source for the engine. In such an engine, interactions between the acoustic, convective, conductive and thermoacoustic energy fluxes facilitate conversion of the input thermal energy into acoustic energy. This study describes the energy flux interactions throughout the engine, thus clarifying the important role of the mean temperature difference that exists between the mean flow of hot gas and the hot-side regenerator interface in the open cycle engine. Furthermore, this study derives an optimal regenerator interface temperature that maximizes the acoustic power output of the engine for a given thermal energy input. The acoustic power output and thermal efficiency of the open cycle engine are compared to those in a closed cycle engine in which a crossflow heat exchanger is used to supply the required heat input. By accounting for the effectiveness of the heat exchanger, it is shown that the open cycle has the potential to achieve higher efficiencies than the closed cycle in converting the thermal energy in a stream of gas into acoustic energy.

Petrogenesis of Mesozoic, Peraluminous Granites in the Lamoille Canyon Area, Ruby Mountains, Nevada, USA

AbstractTwo groups of closely associated, peraluminous, two-mica granitic gneiss were identified in the area. The older, sparsely distributed unit is equigranular (EG) with initial εNd ∼ − 8·8 and initial 87Sr/86Sr ∼0·7098. Its age is uncertain. The younger unit is Late Cretaceous (∼80 Ma), pegmatitic, and sillimanite-bearing (KPG), with εNd from −15·8 to −17·3 and initial 87Sr/86Sr from 0·7157 to 0·7198. The concentrations of Fe, Mg, Na, Ca, Sr, V, Zr, Zn and Hf are higher, and K, Rb and Th are lower in the EG. Major- and trace-element models indicate that the KPG was derived by muscovite dehydration melting (&amp;lt;35 km depth) of Neoproterozoic metapelitic rocks that are widespread in the eastern Great Basin. The models are broadly consistent with anatexis of crust tectonically thickened during the Sevier orogeny; no mantle mass or heat contribution was necessary. As such, this unit represents one crustal end-member of regional Late Cretaceous peraluminous granites. The EG was produced by biotite dehydration melting at greater depths, with garnet stable in the residue. The source of the EG was probably Paleoproterozoic metagraywacke. Because EG magmatism probably pre-dated Late Cretaceous crustal thickening, it required heat input from the mantle or from mantle-derived magma.

Calculation of molten pool shape on directed plasma fabrication

Directed Plasma Fabrication (DPF) is a rapid tooling process based on controlled deposition of molten powder particles according to computer controlled patterns. It makes fully dense, near net shape metal components without molds or dies, and without forming, pressing or forging systems.Experimental works were carried out using conventional low current Plasma Transferred Arc Welding system, and metallic powder was stellite #21. Cylindrical shapes were successfully deposited with dimensions of 0.8–1.2mm wall thickness. Critical parameters were plasma current stability and powder supply. Other key factor was the melting efficiency M, which is defined as the ratio of given heat input into base metal and required heat input to melting of deposited metal. The other was is a non dimensional operating parameter, n proposed by N. Christensen. Better deposition efficiency was obtained in case of lower melting efficiency M, this means shorter arc length and slower traveling speed when the same plasma current conditions are applied.