Thermal Energy Input Research Articles

Compressor driven metal hydride heat pumps using an adsorptive slurry and isothermal compression

Metal hydrides have been investigated for use in environmentally friendly heat pumps. These systems operate using reversible adsorption and desorption of hydrogen from metallic compounds and can be incorporated in a cycle having a work input (compressor) or thermal energy input (generator). Some challenges faced by compressor driven metal hydride heat pumps are poor heat transfer in the metal hydride beds and high compressor discharge temperatures. To overcome these challenges, this article investigates the use of a metal-hydride slurry in conjunction with various isothermal compression techniques. Liquid-flooded, electrochemical, and liquid piston compressors were modeled and integrated into a system model in order to assess their impact on the performance of the slurry-based metal hydride heat pump system.

High-precision optomechanical lens system for space applications assembled by a local soldering technique

Soldering using metallic solder alloys is an alternative to adhesive bonding. Laser-based soldering processes are especially well suited for the joining of optical components made of fragile and brittle materials such as glass, ceramics, and optical crystals. This is due to a localized and minimized input of thermal energy. Solderjet bumping technology has been used to assemble a lens mount breadboard using specifications and requirements found for the optical beam expander for the European Space Agency EarthCare Mission. The silica lens and a titanium barrel have been designed and assembled with this technology in order to withstand the stringent mission demands of handling high mechanical and thermal loads without losing the optical performance. Finally, a high-precision optomechanical lens mount has been assembled with minimal localized stress (<1 MPa) showing outstanding performance in terms of wave-front error and beam depolarization ratio before and after environmental tests.

Photoswitched Cell Adhesion on Azobenzene-Containing Self-Assembled Films.

Stimuli-responsive surfaces that can regulate and control cell adhesion have attracted much attention for their great potential in diverse biomedical applications. Unlike for pH- and temperature-responsive surfaces, the process of photoswitching requires no additional input of chemicals or thermal energy. In this work, two different photoresponsive azobenzene films are synthesized by chemisorption and electrostatic layer-by-layer (LbL) assembly techniques. The LbL film exhibits a relatively loose packing of azobenzene chromophores compared with the chemisorbed film. The changes in trans/cis isomer ratio of the azobenzene moiety and the corresponding wettability of the LbL films are larger than those of the chemisorbed films under UV light irradiation. The tendency for cell adhesion on the LbL films decreases markedly after UV light irradiation, whereas adhesion on the chemisorbed films decreases only slightly, because the azobenzene chromophores stay densely packed. Interestingly, the tendency for cell adhesion can be considerably increased on rough substrates, the roughness being introduced by use of photolithography and inductively coupled plasma deep etching techniques. For the chemisorbed films on rough substrates, the amount of cells that adhere also changes slightly after UV light irradiation, whereas, the amount of cells that adhere to LbL films on rough substrates decreases significantly.

Analysis of a feasible trigeneration system taking solar energy and biomass as co-feeds

The trigeneration systems are widely used owing to high efficiency, low greenhouse gas emission and high reliability. Especially, those trigeneration systems taking renewable energy as primary input are paid more and more attention. This paper presents a feasible trigeneration system, which realizes biomass and solar energy integrating effective utilization according to energy cascade utilization and energy level upgrading of chemical reaction principle. In the proposed system, the solar energy with mid-and-low temperature converted to the chemical energy of bio-gas through gasification process, then the bio-gas will be taken as the fuel for internal combustion engine (ICE) to generate electricity. The jacket water as a byproduct generated from ICE is utilized in a liquid desiccant unit for providing desiccant capacity. The flue gas is transported into an absorption chiller and heat exchanger consequently, supplying chilled water and domestic hot water. The thermodynamic performance of the trigeneration system was investigated by the help of Aspen plus. The results indicate that the overall energy efficiency and the electrical efficiency of the proposed system in case study are 77.4% and 17.8%, respectively. The introduction of solar energy decreases the consumption of biomass, and the solar thermal energy input fraction is 8.6%. In addition, the primary energy saving ratio and annual total cost saving ratio compared with the separated generation system are 16.7% and 25.9%, respectively.

Careful selection of steaming and attrition conditions during thermo‐mechanical pretreatment can increase enzymatic conversion of softwood

AbstractBackgroundAn efficient pretreatment for softwoods prior to enzyme hydrolysis is pressurised steaming of the chips with successive attrition by disc refining and ball milling following removal of some hemicelluloses in a compression screw. For the process to be economical, thermal and mechanical energy inputs need to minimised and sugar yield maximised, so the aim of this study was to improve understanding of the behaviour of fibres during each stage of the pretreatment.ResultsRadiata pine wood chips were treated with steam at 173°C for between 3 and 144 min. The responses to refining and ball milling in terms of particle size reduction and sugar yield improved gradually as steaming time was increased to 36 min, but then an abrupt change in behaviour occurred resulting in more small particles during refining and much faster response to ball milling. This point coincides with an increase in cellulose degradation and fibre embrittlement. However, this higher steaming severity did not necessarily give highest sugar yields during saccharification as it limits the amount of energy that can be usefully applied during ball milling.ConclusionsThe results from this study can be utilised for optimisation of the pretreatment of softwoods like radiata pine. While effective in delivering high sugar yields, the steaming/refining/ball milling pretreatment is quite energy intensive but the results of this study show that significant savings in overall energy are possible by optimising relative energy inputs to the steaming and ball milling stages. © 2016 Society of Chemical Industry

Experimental investigation of direct diamond laser cladding in combination with high speed camera based process monitoring

Laser cladding is an established coating technology which is established as emerging technology for repair applications and for the fabrication of near net shape geometries. Within the scope of coating, repair and additive manufacturing applications single weld tracks are generated on a metal substrate by a laser beam and simultaneously injected metal powder. For coating applications, such as wear-resistant coatings, single weld tracks are positioned next to each other in order to form a continuous surface layer. Coatings against heavy abrasive wear often contain additional particles like tungsten carbide or diamond particles. However, by embedding wear-resistant particles like tungsten or diamond particles, varying applications can be addressed. For example, the cutting ability of industrial tools can be enhanced by embedding diamonds into a coating. In this paper, a novel approach, the direct embedding of diamonds without using a metal matrix during laser cladding is experimentally investigated. As diamonds are susceptible to heat, varying strategies for thermal energy input in the first place different laser modes of operations (continuous wave and pulsed) are investigated for direct diamond laser cladding. Major objectives of the presented research work are homogeneous diamond distribution on the surface of the sheet metal samples, low number of metal covered diamonds, and minor thermal damage to the embedded diamonds. Based on metallographic analyses, the generated samples are evaluated with respect to the previously stated objectives. During direct diamond laser cladding different phenomena like increasing width of a single weld track during one transit and varying penetration depths can be observed. In order to understand and explain these phenomena, a high speed camera is used for process monitoring. For the detection of these process irregularities, cross sections and the data gathered via process monitoring are analyzed. The results which are presented in this paper allow conclusions to be drawn about the laser diamond interaction mechanisms and about processing parameters for embedding diamonds without a metal matrix.

Constraints on energy release in solar flares from RHESSI and GOES X-ray observations

Aims. We constrain energy release and particle acceleration processes in solar flares by means of comprehensively characterizing the physical parameters of both the thermal plasma and the accelerated nonthermal particles using X-ray data. Our aim is to bridge the gap between detailed case studies and large statistical studies.Methods. We obtained time series of spectral fits and images for 24 flares ranging from GOES class C3.4 to X17.2 using RHESSI hard X-ray observations. These data were used to derive basic physical parameters for the thermal plasma (using the isothermal approximation) and the injected nonthermal electrons (assuming the thick-target model). For the thermal component, this was supplemented by GOES soft X-ray data. We derived the ranges and distributions of the various parameters, the scaling with flare importance, and the relation between thermal parameters derived from RHESSI and GOES. Finally, we investigated the relation between thermal and nonthermal parameters.Results. Temperature and emission measure of the thermal plasma are strongly correlated with the peak GOES X-ray flux. Higher emission measures result both from a larger source volume and a higher density, with the latter effect being more important. RHESSI consistently gives higher temperatures and lower emission measures than GOES does, which is a signature of a multithermal plasma. The discrepancy between RHESSI and GOES is particularly pronounced in the early flare phase, when the thermal X-ray sources tend to be large and located higher in the corona. The energy input rate by nonthermal electrons is correlated with temperature and with the increase rate of emission measure and thermal energy.Conclusions. The derived relations between RHESSI- and GOES-derived thermal parameters and the relation between thermal parameters and energy input by nonthermal electrons are consistent with a two-component model of the thermal flare plasma. Both RHESSI and GOES observe a cooler plasma component (≈10−25 MK) that is generated by chromospheric evaporation caused by a nonthermal electron beam. In addition, a hotter component (≥25 MK) is only detected by RHESSI; this component is more consistent with direct in situ heating of coronal plasma. With the exception of the early impulsive phase, RHESSI observes a combination of the evaporated and the directly heated component.

Comparison of different operation modes of a single effect thermal desalination plant using waste heat from m-CHP units

This work is an in-depth analysis of the performance behavior of a small scale single effect thermal desalination plant. The prototype, which refers to the distributed micro cogeneration field, consists of a 1 kWe Stirling engine coupled with a single effect thermal desalination plant for the simultaneous production of electricity and >150 L/day of fresh water.The prototype was able to work in two different operation modes: batch operation and continuous operation. In the former, the evaporator tank is initially filled with the salt water up to its maximum and the evaporation process ends as the salt water level reaches the top of the coil. In the latter, concentrate is continuously extracted and salt water is fed inside the evaporator tank in order to maintain brine salinity almost constant.In a previous work authors investigated the plant performance in batch operation mode finding a good agreement with the predicted results. In this work, plant performance is evaluated in continuous operation and compared to the batch operation mode. In both cases, fresh water production reached a maximum of about 7 L/h in the best operating conditions. However, despite the higher complexity of the plant, performance is worse in the continuous operation mode due to the negative effect of the continuous seawater flow. Indeed, the lower the salt content of the treated water, the lower the fresh water production due to process limits which will be extensively discussed in the paper. More precisely, the plant's average productivities were about 1.3 L/kWh and 1.16 L/kWh of thermal energy input in batch and continuous operation modes respectively.In any case, the apparatus exhibited a very good response to varying thermal power input thus confirming the opportunity to feed the desalination plant also with different forms of waste heat.Hence the proposed solution, studied for a coupling with a 1 kWe Stirling engine, can be easily applied also to the other micro-CHP technologies.

Continuous manufacturing of carboxyamidotriazoleencapsulated nanoemulsions using adaptive focused acoustics: Potential green technology for the pharmaceutical industry

Nanoemulsions containing hydrophobic drugs have a great potential in the pharmaceutical industries to improve thebioavailability of the drug. However, currently there is no cost-effective way of producing nanoemulsions in large scale.The need of subjecting emulsions to an extreme pressure of 50 MPa demands a large excess of energy for themanufacturing process, while low-energy method requires large amount of solvents. Here, nanoemulsions containing awell-characterized hydrophobic drug, carboxyamidotriazole (CAI), are produced in both batch and continuous modes todemonstrate the scalability of nanoemulsion production using Covaris’ Adaptive Focused Acoustics™ (AFA) technology.To move from batch scale to continuous flow, the acoustic and thermal energy inputs can be manipulated to adjust particlesize, while the composition and temperature of starting materials can be altered to achieve complete dissolution ofhydrophobic drugs, thus providing 100% encapsulation efficiency. Furthermore, using two AFA systems in series candrastically enhance the production flow rates, making AFA a competitive means for producing nanoemulsions in thepharmaceutical industry.

Linking zooplankton richness with energy input and insularity along altitudinal and latitudinal gradients

AbstractAltitudinal and latitudinal gradients are excellent venues for investigating the direct and indirect effects of air temperature, solar irradiance, and insularity on spatial patterns of aquatic biodiversity. The findings can be used to predict how lake communities will respond to increasingly extreme climate events. We explored hypotheses of energy/climate, geography, and glacial history explaining patterns in species richness in a historical dataset of crustacean zooplankton communities from 436 lakes in the Canadian Rocky Mountains. GIS‐based estimates of solar and thermal energy inputs combined with habitat area and insularity provided the best prediction of local species richness. Energetic and geographic factors explained a moderate proportion of the total variation in species richness (Generalized R2 = 0.50), and were sufficient to account for both altitudinal and latitudinal gradients in zooplankton diversity. History of deglaciation was not supported as a predictor of patterns in species richness. A post hoc analysis with a smaller dataset also found strong support for lake pH, and some support for fish presence as predictors of species richness, but these only increased the proportion of the total variation explained very slightly relative to the model including only energetic and geographic factors (Generalized R2 = 0.55 vs. 0.53). Our findings highlight the multiplicity of local and regional factors of zooplankton species richness in mountain lakes, forecasting that it will increase under a scenario of warmer and drier (i.e., less cloud cover) conditions, especially in high connectivity lakes that cease to be fed by rapidly disappearing glaciers.

Effect of Laser Beam Alloying Strategies on the Metallurgical and Mechanical Properties of Hot Forming Tool Steels

In terms of increasing lightweight designs of car body parts, the machining of high strength steels in hot stamping processes becomes of particular interest. Due to high process forces at hot stamping, the surface of such tools in the area of maximal stress is subject wear, which necessitate some local increase of microhardness to enhance the mechanical performance. Especially laser beam alloying using filler wire and beam oscillation is some suitable method to modify the mechanical properties of tool surfaces to emcompass some continuous martensitic structure, featuring a certain microhardness. Nevertheless the thermal energy input during laser beam alloying induces tempering in the heat affected zone and reduces the hardness.This paper discusses the influence of alloying strategies on the thermal energy input and the resulting metallurgical structure of modified tool surfaces. Also the cooling behavior of alloyed lines for different energy inputs per unit length is of interest. Therefore, the metallurgical microstructure is analyzed regarding microhardness as well as formation of carbides. Furthermore, a numerical thermal simulation is developed to investigate the temperature profile in the heat affected zone of the specimen. These investigations permit the control of the spatiotemporal energy input to avoid tempering of the microstructure.

Thermal modelling of a differential calorimeter for magnetic nanoparticle specific absorption rate measurement

Magnetic nanoparticles provide thermo-necrosis therapies but the impact of temperature on the surrounding tissue must be precisely controlled to avoid damage. In this paper, we investigated the design and validation of a differential calorimeter for the evaluation of the specific absorption rate (SAR) of magnetic nanoparticles within colloidal dispersions. Accuracy in the final SAR values was achieved through systematic analysis of the key sources of thermal energy inputs and thermal transport within the environment of the calorimeter, modelled by both a distributed heat equation and a lumped parameter model. This design and the two thermal capacity models used allowed subsequent experimental parameters to be evaluated from the calorimetry protocol reducing uncertainty in the SAR values. Enhanced precision in SAR values would provide additional control of tissue temperatures in thermal necrosis when employing magnetic nanoparticles as a heating source.

A Case of Study of a Concentrating Solar Power Plant with Unfired Joule-Brayton Cycle

A solar closed air Brayton cycle, with rated power of 50 MW, was considered. The system is composed of a concentrating solar tower with volumetric receiver, an intercooling and regenerating gas turbine and an evaporative tower cooling system. The characteristic feature of the system is a control strategy able to adjust the plant in a large range of load, maintaining net electric conversion efficiency almost constant. The concentrating solar power (CSP) plant operates without adding fuel and can heat air up to a maximum temperature of 850°C, at the solar tower outlet. The numerical analysis was performed by SAM for the solar tower and by Thermoflex © for the assessment of the performance of the whole system. The thermal energy input was calculated on the basis of the DNI of the TMY from Seville. Results show an electricity production greater than 75GWh per year, with a significant sparing fossil fuel consumption and avoided CO2 emissions.

“Salty” conversation

Thiel replies: When thinking about potential toxicity, which Neal Reid mentions, it’s key to remember that almost all the material in the brine originated in the ocean. Nevertheless, ensuring environmentally friendly disposal continues to be an active area of research, and modern outfalls are very effective at dispersing the brine flow so as to minimize local increases in the concentration of salts and other dissolved compounds. A study for the Carlsbad desalination project in California concluded that properly designed outfalls have “impacts that extend only a few tens of meters from the discharge.”11. S. Jenkins et al., Management of Brine Discharges to Coastal Waters: Recommendations of a Science Advisory Panel, tech. rep. 694, Southern California Coastal Water Research Project (March 2012), p. ii. The Carlsbad plant also mixes the reverse-osmosis brine with seawater used for cooling a colocated power plant prior to discharge, which reduces its salinity before it hits the ocean. And as for the comparison to nuclear waste, let’s not forget that the diffusion time for the salt in the disposed brine is orders of magnitude less than the half-life of radioactive waste!To answer Jonathan Allen’s concern, the kWhe values given for the evaporative systems are exergetic values of the heat input. That approach uses the Carnot efficiency between the desalination system’s top temperature, which often reaches 70 °C, and an ambient temperature of 25 °C to convert between heat and work. The cost of the thermal energy input itself may be less than for electricity, but the costs associated with constructing, for example, a solar-thermal collector or a heat exchanger required to use waste heat can be significant. Lower energy consumption may not imply lower cost, but reverse osmosis is far and away the dominant choice of recent installed desalination capacity.Desalination powered by renewable energy is a topic of great interest to many in the desalination community—myself included!REFERENCESSection:ChooseTop of pageREFERENCES <<CITING ARTICLES1. S. Jenkins et al., Management of Brine Discharges to Coastal Waters: Recommendations of a Science Advisory Panel, tech. rep. 694, Southern California Coastal Water Research Project (March 2012), p. ii. Google Scholar© 2015 American Institute of Physics.

Thermal window insulation

A definite requirement of the building envelope is to separate the natural environment from the indoor environment. Energy is one component of the environment that we sometimes wish to capture, harness, or reject. How can these actions be best performed to yield passive benefits such as solar heating or shading?This research focuses on control of solar radiation, and the role windows play as transfer medium between indoor and outdoor environments. A timely control of solar thermal energy input, and building thermal energy output with the use of operable window insulation is investigated during the heating season in the local Toronto climate.This is done through a combination of 3D finite element mathematical model and field performance tests. Model results and field tests reveal an energy imbalance attributed to unpredictable solar gains and spectrally-dependent emissivity of materials. Simulation results of the daily control show little improvement over use of a static system for a western building façade. The negligible difference versus a static system is attributed largely to human-error deficiencies associated with timely controls.

Light-Triggered Responsive Janus Composite Nanosheets

We report the synthesis of light-triggered Janus composite nanosheets and their Janus performance. Onto the amine-group terminated side of silica Janus nanosheets, a photo-responsive spiropyran-containing polymer (PSPMA) brush has been prepared by ATRP, while the other side terminated with hydrophobic octyl groups is preserved. Upon UV irradiation, the hydrophobic PSPMA side becomes hydrophilic since the hydrophobic spiropyran changes to the hydrophilic zwitterionic merocyanine form (or vice versa with visible light). Consequently, the PSPMA/silica composite nanosheets become Janus from hydrophobic or vice versa. The Janus composite nanosheets can serve as a responsive solid emulsifier, thus the stability of the emulsions can be remotely triggered with light. Unlike those pH- or temperature-responsive Janus materials, the light-triggering process requires no additional input of chemicals or thermal energy.

Processing and crystallographic structure of non-equilibrium Si-doped HfO2

Si-doped HfO2 was confirmed to exist as a non-equilibrium state. The crystallographic structures of Si-doped HfO2 were studied using high-resolution synchrotron X-ray diffraction and the Rietveld refinement method. Incorporation of Si into HfO2 and diffusion of Si out of (Hf,Si)O2 were determined as a function of calcination temperature. Higher thermal energy input at elevated calcination temperatures resulted in the formation of HfSiO4, which is the expected major secondary phase in Si-doped HfO2. The effect of SiO2 particle size (nano- and micron-sized) on the formation of Si-doped HfO2 was also determined. Nano-crystalline SiO2 was found to incorporate into HfO2 more readily.

Refuse derived fuel (RDF) plasma torch gasification as a feasible route to produce low environmental impact syngas for the cement industry

Plasma torch gasification (PTG) is currently researched as a technology for solid waste recovery. However, scientific studies based on evaluating its environmental implications considering the life cycle assessment (LCA) methodology are lacking. Therefore, this work is focused on comparing the environmental effect of the emissions of syngas combustion produced by refuse derived fuel (RDF) and PTG as alternative fuels, with that related to fossil fuel combustion in the cement industry. To obtain real data, a semi-industrial scale pilot plant was used to perform experimental trials on RDF-PTG.The results highlight that PTG for waste to energy recovery in the cement industry is environmentally feasible considering its current state of development. A reduction in every impact category was found when a total or partial substitution of alternative fuel for conventional fuel in the calciner firing (60 % of total thermal energy input) was performed. Furthermore, the results revealed that electrical energy consumption in PTG is also an important parameter from the LCA approach.

Non-Destructive Inspection of Adhesively Bonded Joints using Amplitude Modulated Thermography

The goal of this work is to design thermal waves specifically for pulsed-phase infrared thermography (PPT) of bonded joints and to test their effectiveness on adhesive lap joints in carbon-fiber reinforced polymers structures. The method was applied to both single and double lap joint specimens to test different defect depths and multiple lap joint interfaces. An optimal thermal wave was designed for each specimen type based on the blind frequency information obtained from square pulse thermal wave excitation of the lap joint specimens. Modifications to the optimal thermal wave were then implemented based on the physical limitations of the lamp systems and different threshold settings for the blind frequency calculation. Thermal input waves based on the linear combination of discrete frequency waves were also implemented. The discrete frequency waves improved the defect image contrast in both the single and double lap joint specimens, while the optimal thermal input wave had the opposite effect and instead highlighted surface features. The difference in performance between the two thermal input waves is presumed to be due to the ability to separate frequency components in the transformation of data and not due to a critical thermal energy input threshold.

Emission and heat transfer characteristics of methane–hydrogen hybrid fuel laminar diffusion flame

The effect of adding hydrogen to methane on the emission and heat transfer characteristics of a laminar diffusion flame was investigated. The total input thermal energy for each test was kept constant. The results showed that adding hydrogen increased the temperature, decreased the flame length, and significantly increased the soot-free length fraction. CO and CO2 emission decreased with the addition of hydrogen. The more efficient oxidation of CO to CO2 at higher hydrogen fractions was the main contributor to the reduction of CO, whereas decreased carbon input was the dominant factor for the reduction of CO2. The NOx emission increased owing to the increase of prompt, thermal NOx formation and NNH pathway. The ratio of radiative heat flux to total heat flux decreased, and the radiative heat flux did not exceed 5% of the total heat flux. The addition of hydrogen improved the total heat flux by approximately 20%.