Hot Chamber Research Articles

Thermal performance of additively manufactured polymer lattices

The energy performance of buildings is a key point to achieve the sustainability goals of the modern world. The reduction of the heat loss by incorporating porosity in a monolithic material was studied. To this aim, lattice structures with varying lattice topology and specimen size were synthesised using polymer based additive manufacturing. Commercially available 3D printers and polymer filaments were utilised to manufacture such polymer lattices. Their thermal performance was characterised using a bespoke compact temperature-change hot chamber. A scaling law, based on the experimental results, has been proposed for the first time to predict the U-value of polymer lattices by correlating their effective thermal conductivities. It was observed that the lattice's relative density and the sizes of a unit cell and specimen affected significantly the U-value. Also, it was found that polymer-lattice structures can be designed to only allow a conductive mode of heat transfer when their hydraulic diameter was less than 8 mm. The effect of an AM process parameters such as the layer thickness and type of 3D printer on the U-value of the polymer lattices was also characterised and found that they had a mild effect on the U-value of the lattices. Thus, a highly optimised lattice structure, aiming at achieving the higher thermal resistance to make it suitable for energy saving applications, can be obtained using the proposed scaling law.

A Technology for Improving Regenerative Cooling in Advanced Cryogenic Rocket Engines for Space Transportation

Regenerative cooling of thrust chamber is the unique solution for the thermal management of high heat flux generated inside the combustion chamber of Cryogenic rocket engine. Heat is transferred from combustion hot gas to coolant through the channels provided on inner copper shell, thereby cools the inner wall of the nozzle. A novel technique of providing copper foam inside the channels will act as an infinite fin and also act as barrier for coolant stratification. This will improve the heat transfer to the coolant and reduce the nozzle wall temperature. Heat transfer improvement with copper foam inserts to the coolant channel is demonstrated through experiments with simulated fluids. Experiments are conducted with simulated hot gas chamber and coolant channels using water as the coolant. Copper foam with high porosity is selected to fill the channels. Hot tests are carried out with copper foam filled coolant channels and measured the coolant temperature rise and pressure drop across the channels. Tests are repeated with similar hot gas condition, but without inserting copper foam inside the channels. A substantial enhancement in heat transfer to the coolant is observed with copper foam inserts experiments, which will reduce the wall temperature. This gives a good handle on the life cycle improvement of multi-start cryogenic engines for future space transportation systems. This paper details the specification of copper foam, hardware design, experiments and measurements, and the application of the augmentation of heat transfer coefficient in operating cryogenic engines.

Puffing/micro-explosion in rapeseed oil/water droplets: The effects of coal micro-particles in water

The paper is focused on detailed experimental investigation of puffing and micro-explosions in composite water/rapeseed oil droplets in the presence of lignite and bituminous coal micro-particles in water. Gas temperature was measured using a high speed National Instruments 9219 for data collection and an S-type thermocouple. Video recording of droplet micro-explosions was performed using a Phantom Miro M310 high-speed camera. Droplets with radii in the range 1–2 mm were placed in a hot chamber with air velocities 3–7 m/s and temperatures up to 600 °C. The time to puffing/micro-explosion and average radii of child droplets generated during puffing and micro-explosions are shown to decrease with increasing gas temperature. The presence of bituminous coal led to a visible decrease in these radii. The observed times to puffing/micro-explosion were interpreted in terms of the recently developed model of the phenomenon based on the assumption that a single spherical water sub-droplet is located in the centre of a spherical fuel droplet. The time to puffing/micro-explosion in this model is associated with the time instant when the temperature at the water/fuel interface reaches the water nucleation temperature. The model predicts a decrease in time to puffing/micro-explosion in agreement with experimental observations. The effect of coal particles on this time is shown to be weak in agreement with observations at gas temperatures above 300 °C. It is shown that the times to puffing predicted by the model are close to those predicted by a simpler model in which these times are identified with the time instants when the temperature at the water/fuel interface reaches the boiling temperature of water.

Performance Evaluation of Domestic Refrigerator with Waste Heat Recovery System

The objective of the article is to study the performance of domestic refrigerator with waste heat recovery system. The usage of domestic refrigeration systems are increasing every day due to the requirement. During the operation of domestic refrigeration system, heat is rejected through the condensing coil to the atmosphere and leads to thermal pollution. Hence this heat can be recovered by suitable waste heat recovery system and employed for useful domestic applications. Hot chamber box has been fabricated and assembled with the domestic refrigerator. Experimental analysis has been carried out under air cooled condenser and hot chamber condenser with different loading conditions like no load, 1 litre, 3 litres, 5 litres, and 10 litres of water in the evaporator unit. COP is calculated for all the loading conditions and compared with air cooled condenser and hot chamber condenser. COP of all the loading conditions is maintained almost in the same range value. COP value is obtained in the range of 5 to 5.5 for the air cooled and hot chamber condensation modes. Hence the performance of domestic refrigerator is not changed due to the running of hot chamber box. Due to installation of hot chamber box waste heat is recovered from the condenser coil. The maximum heat recovery is arrived in the range of 31.15 to 33.66 kJ/kg.

Chemically Activated Cooling Vest's Effect on Cooling Rate Following Exercise-Induced Hyperthermia: A Randomized Counter-Balanced Crossover Study.

Background and objectives: Exertional heat stroke (EHS) is a potentially lethal, hyperthermic condition that warrants immediate cooling to optimize the patient outcome. The study aimed to examine if a portable cooling vest meets the established cooling criteria (0.15 °C·min−1 or greater) for EHS treatment. It was hypothesized that a cooling vest will not meet the established cooling criteria for EHS treatment. Materials and Methods: Fourteen recreationally active participants (mean ± SD; male, n = 8; age, 25 ± 4 years; body mass, 86.7 ± 10.5 kg; body fat, 16.5 ± 5.2%; body surface area, 2.06 ± 0.15 m2. female, n = 6; 22 ± 2 years; 61.3 ± 6.7 kg; 22.8 ± 4.4%; 1.66 ± 0.11 m2) exercised on a motorized treadmill in a hot climatic chamber (ambient temperature 39.8 ± 1.9 °C, relative humidity 37.4 ± 6.9%) until they reached rectal temperature (TRE) >39 °C (mean TRE, 39.59 0.38 °C). Following exercise, participants were cooled using either a cooling vest (VEST) or passive rest (PASS) in the climatic chamber until TRE reached 38.25 °C. Trials were assigned using randomized, counter-balanced crossover design. Results: There was a main effect of cooling modality type on cooling rates (F[1, 24] = 10.46, p < 0.01, η2p = 0.30), with a greater cooling rate observed in VEST (0.06 ± 0.02 °C·min−1) than PASS (0.04 ± 0.01 °C·min−1) (MD = 0.02, 95% CI = [0.01, 0.03]). There were also main effects of sex (F[1, 24] = 5.97, p = 0.02, η2p = 0.20) and cooling modality type (F[1, 24] = 4.38, p = 0.047, η2p = 0.15) on cooling duration, with a faster cooling time in female (26.9 min) than male participants (42.2 min) (MD = 15.3 min, 95% CI = [2.4, 28.2]) and faster cooling duration in VEST than PASS (MD = 13.1 min, 95% CI = [0.2, 26.0]). An increased body mass was associated with a decreased cooling rate in PASS (r = −0.580, p = 0.03); however, this association was not significant in vest (r = −0.252, p = 0.39). Conclusions: Although VEST exhibited a greater cooling capacity than PASS, VEST was far below an acceptable cooling rate for EHS treatment. VEST should not replace immediate whole-body cold-water immersion when EHS is suspected.

Interaction of Exercise Intensity and Simulated Burn Injury Size on Thermoregulation.

This study aimed to test the hypothesis that the elevation in internal body temperature during exercise in a hot environment is influenced by the combination of exercise intensity and BSA burned. Ten healthy participants (8 males, 2 females; 32 ± 9 yr; 75.3 ± 11.7 kg) completed eight exercise trials on a cycle ergometer, each with different combinations of metabolic heat productions (low, 4 W·kg-1; moderate, 6 W·kg-1) and simulated BSA burn in a hot environmental chamber (39.9°C ± 0.3°C, 20.1% ± 1.5% RH). Burns were simulated by covering 0%, 20%, 40%, or 60% of participants' BSA with a highly absorbent, vapor-impermeable material. Gastrointestinal temperature (TGI) was recorded, with the primary analysis being the increase in TGI after 60 min of exercise. We identified an interaction effect for the increase in TGI (P < 0.01), suggesting TGI was influenced by both intensity and simulated burn BSA. Regardless of the percentage BSA burn simulated, the increase in TGI was similar across low-intensity trials (0.70°C ± 0.26°C, P > 0.11 for all). However, during moderate-intensity exercise, the increase in TGI was greater for the 60% (1.78°C ± 0.38°C, P < 0.01) and 40% BSA coverage trials (1.33°C ± 0.44°C, P = 0.04), relative to 0% (0.82°C ± 0.36°C). There were no differences in TGI responses between 0% and 20% trials. These data suggest that exercise intensity influences the relationship between burn injury size and thermoregulatory responses in a hot environment.

Thermo-environ study of a concentrated photovoltaic thermal system integrated with Kalina cycle for multigeneration and hydrogen production

Unlike steam and gas cycles, the Kalina cycle system can utilize low-grade heat to produce electricity with water-ammonia solution and other mixed working fluids with similar thermal properties. Concentrated photovoltaic thermal systems have proven to be a technology that can be used to maximize solar energy conversion and utilization. In this study, the integration of Kalina cycle with a concentrated photovoltaic thermal system for multigeneration and hydrogen production is investigated. The purpose of this research is to develop a system that can generate more electricity from a solar photovoltaic thermal/Kalina system hybridization while multigeneration and producing hydrogen. With this aim, two different system configurations are modeled and presented in this study to compare the performance of a concentrated photovoltaic thermal integrated multigeneration system with and without a Kalina system. The modeled systems will generate hot water, hydrogen, hot air, electricity, and cooling effect with photovoltaic cells, a Kalina cycle, a hot water tank, a proton exchange membrane electrolyzer, a single effect absorption system, and a hot air tank. The environmental benefit of two multigeneration systems modeled in terms of carbon emission reduction and fossil fuel savings is also studied. The energy and exergy efficiencies of the heliostat used in concentrating solar radiation onto the photovoltaic thermal system are 90% and 89.5% respectively, while the hydrogen production from the two multigeneration system configurations is 10.6 L/s. The concentrated photovoltaic thermal system has a 74% energy efficiency and 45.75% exergy efficiency, while the hot air production chamber has an 85% and 62.3% energy and exergy efficiencies, respectively. Results from this study showed that the overall energy efficiency of the multigeneration system increases from 68.73% to 70.08% with the integration of the Kalina system. Also, an additional 417 kW of electricity is produced with the integration of the Kalina system and this justifies the importance of the configuration. The production of hot air at the condensing stage of the photovoltaic thermal/Kalina hybrid system is integral to the overall performance of the system.

Design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system: preliminary results.

Nowadays global warming has increased consciousness of the dangers of energy wastefulness: in the last 50 years the temperature of the Earth’s surface rose by approximately 1 °C. The building sector is responsible for a very high percentage of world carbon emissions and with the increasing of the request for comfort, heating, ventilation and air conditioning, buildings energy consumption is rapidly growing. Consequently, it appears fundamental the role played by the improvement of buildings energy performance within global policies of emissions reduction. In this context an increasing attention is given to the energy waste reduction in tertiary sector: bars, offices, restaurants, meetings, shops, school buildings, gyms and in general in the buildings in which the minimization of the energy dissipation is requested. The present study is part of the NANOFANCOIL project (POR-FESR 2014-2020): one of the objectives was the design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system. This experimental setup was mainly composed by two climatic chambers that enabled to simulate the environmental conditions of interest. The temperature could vary from -20°C to 0°C and from 10°C to 30°C for the cold and the hot chamber, respectively (i.e. the outdoor and the indoor environment). Moreover, the climatic chamber that simulates the indoor environment could be controlled also in terms of humidity thanks to a steam humidifier that guaranteed 5 kg/h of vapour. Preliminary results about the heat transfer behaviour of a cross-flow heat recovery unit (air-to-air) for controlled mechanical ventilation systems that employs mini-channels in order to increase performance and reduce size and costs are presented here.

Steady-state and process modeling of a novel wind-biomass comprehensive energy system: An energy conservation, exergy and performance analysis

One of the main challenges in renewable energy integrated multigeneration and comprehensive system researches is the inability to study the transient performance analysis of the system. In this study, a novel wind-biomass comprehensive energy system for power, cogeneration, trigeneration, and multigeneration is proposed. This system is analyzed in both steady-state and transient conditions using energy and exergy approaches. Rice husk is considered as the raw material for biomass fuel. The comprehensive system is modeled to produce electricity, freshwater, hot water, and hydrogen with a steam cycle, an organic Rankine cycle, a double stage refrigeration system, a proton exchange membrane electrolyzer, and a hot water chamber. Electric vehicles are integrated with the system in time-based process modeling to ensure load stability and maximize electricity production. The overall exergy and energy efficiencies of the proposed comprehensive system increase from 24.91% and 27.42% while producing electricity to, 26.08% and 35.22% when multigenerating. Based on the transient analysis, this system is capable of meeting the energy demand of a rice-producing factory, campus, and its surrounding community. The process modeling also shows the hourly performance of the system and its load stability.

Application of Refractory Metals to Facilitate Hot Chamber Aluminum Die Casting

The hot chamber die casting process is capable of producing castings of superior mechanical properties and internal integrity. However, this process cannot be used for die casting of aluminum alloys because the molten aluminum erodes ferrous alloy tooling such as the gooseneck. Ceramic gooseneck was tested, but was not accepted commercially. This work evaluates the feasibility of using refractory metals for the tooling of the hot chamber die casting process. Experiments were performed to measure the weight loss of selected materials in molten aluminum at die casting temperatures. Refractory metals with excellent aluminum erosion resistance were selected and used for making gooseneck and nozzle. These components were installed in a hot chamber die casting machine. The world’s first hot chamber die casting machine equipped with refractory metal tooling is now running at Purdue University for making aluminum alloy castings.

Review of Microstructures and Properties of Zinc Alloys

According to market data, about 15% of world zinc consumption is devoted to the production of zinc-base alloys that are used for manufacturing automotive parts, electronic/electrical systems and also, water taps and sanitary fittings, household articles, fashion goods, etc. These alloys are characterized by low melting points and high fluidity that make them suitable for foundry applications. Typically, they are processed by hot chamber high-pressure die-casting where can be cast to thicknesses as low as 0.13 mm. The die-cast zinc alloys possess an attractive combination of mechanical properties, permitting them to be applied in a wide variety of functional applications. However, depending on the alloying elements and purposes, some zinc alloys can be processed also by cold chamber die-casting, gravity, or sand casting as well as spin casting and slush casting. In this paper, a detailed overview of the current knowledge in the relationships between processing, microstructure and mechanical properties of zinc-base alloys will be described. In detail, the evolution of the microstructure, the dimensional stability and aging phenomena are described. Furthermore, a thorough discussion on mechanical properties, as such as hardness, tensile, creep, and wear properties of zinc-base alloys is presented.

Silica Precipitation in a Wet-Dry Cycling Hot Spring Simulation Chamber.

Terrestrial hot springs have emerged as strong contenders for sites that could have facilitated the origin of life. Cycling between wet and dry conditions is a key feature of these systems, which can produce both structural and chemical complexity within protocellular material. Silica precipitation is a common phenomenon in terrestrial hot springs and is closely associated with life in modern systems. Not only does silica preserve evidence of hot spring life, it also can help it survive during life through UV protection, a factor which would be especially relevant on the early Earth. Determining which physical and chemical components of hot springs are the result of life vs. non-life in modern hot spring systems is a difficult task, however, since life is so prevalent in these environments. Using a model hot spring simulation chamber, we demonstrate a simple yet effective way to precipitate silica with or without the presence of life. This system may be valuable in further investigating the plausible role of silica precipitation in ancient terrestrial hot spring environments even before life arose, as well as its potential role in providing protection from the high surface UV conditions which may have been present on early Earth.

Development of a method for determining corrosion damage of fuel element claddings of a nuclear power unit by using acoustic resonance method in a hot chamber environment

As part of the strategic research program of state corporation Rosatom, carried out by the Technological Platform “Closed Nuclear Fuel Cycle with Fast Neutron Reactors”, a research to equip protective cells with original equipment, including ultrasonic flaw detectors for primary post-reactor non-destructive research of the properties of critical materials of fast neutron reactors, is being performed. In this paper, we present a method developed for determining corrosion damage of fuel claddings by the acoustic resonance method in hot chamber conditions, and a description of the experimental installation.

Energy, exergy and environmental analyses of a biomass driven multi-generation system

In this research, a biogas driven multi-generation system is presented. The multi-generation system consists of a gas cycle, steam cycle, absorption cycle, hot water producing chamber and hot air producing chamber. The biogas used as thermal input source is derived from agricultural waste specifically maize silage and chicken manure. Thermodynamic analysis is done with energy and exergy approach. The exergy destruction within major components of these systems are also analysed. The environmental analysis for this research focuses on the carbon emission reduction. The energy and exergy efficiency of the system respectively increases from 25.16% and 18.61% when generating electrical energy only, to 73.15% and 27.27% when multi-generating.

Corrosion tests in water of fuel elements irradiated in the world’s first NPP reactor

Spent nuclear fuel (SNF) storage in reactor spent fuel pools (SFP) is one of the crucial stages of SNF management technology: it requires special measures to ensure nuclear and radiation safety. During long-term storage in water-filled SFPs, leak-tight canisters in which SFAs are usually placed can become unsealed, which will result in the development of corrosion processes in the fuel element (FE) claddings. We studied fragments of spent fuel elements of the AM reactor of the World’s First NPP during their long exposure in the aqueous medium. The aim of the study was to obtain experimental data on the corrosion changes in the FE claddings and fuel composition during storage as well as on the release of radioactive fission products from them. For the study, a laboratory facility for exposing fuel elements in the water was developed and experimental fragments of fuel elements were made. The study was carried out in the hot chamber of the SSC RF-IPPE. The change in the activity of the water was estimated by the γ-dose rate from the selected water sample. The diameter measurements and metallographic studies were carried out in various sections of FE fragments. Corrosion tests were carried out on fragments of spent fuel elements of the AM reactor of the World’s First NPP that were stored for a long time (more than 50 years – FEs with U-Mo fuel and ~ 20 years – FEs with UO2 fuel) using standard technology – first in SFP canisters filled with water and then in dry canisters in the air. Placing the fuel elements in the water did not lead to through damage to the FE claddings and a significant change in the size (diameter) of the outer cladding. Metallographic studies of the FE fragments after the corrosion tests showed the presence of intergranular and local frontal corrosion on the surface of the claddings, the depth of which exceeded the depth of the cladding corrosion defects before testing. The rate of radionuclide release from the fuel composition was estimated by the γ-dose rate of water samples taken from the glasses with FE fragments. Throughout the test period, the dose rate of water samples from the glasses with defect-free FEs remained constant. The dose rate from water samples taken from the glasses with the FE fragments with an artificial defect grew during storage.

Oxygen Behavior in High Temperature Plasma and its Applications to Hydrocarbon Fuels

Oxygen molecules breakdown to atoms by impact dissociation of electrons in a microwave oxygen torch. Typical atom density of oxygen in a microwave torch is a few times of 1018/cm3 produced within millisecond time scale. Dwelling time of an oxygen fluid element in a discharge tube is longer than 10 milliseconds, which is much longer than the atom production time. The oxidation coefficient of hydrocarbon fuel in oxygen atoms is usually about one million times faster than that in oxygen molecules. As an example of applications, oxygen atoms are applied to dimethyl ether, which is relatively a large molecular structure. The initial breakdown species of DME molecules in a high-temperature reaction chamber are hydrogen, carbon monoxide and methane, which is also breakdown to CO and H2 by oxygen atoms. Abundance of water may be generated in a reaction chamber of relatively low-temperature lower than Tg = 1500K, hindering an efficient production of synthetic gas. DME disintegration in a hot chamber by a microwave oxygen torch is experimentally observed. Experimental observation is somewhat agreeing with theoretical predictions.

Performance Analyses of a Renewable Energy Powered System for Trigeneration

In this research, a novel trigeneration powered by a renewable energy (RE) source is developed and analyzed. The trigeneration system is designed to produce electricity, hot water, and cooling using two steam cycles, a gas cycle, hot water chamber, and an absorption cycle. The RE source considered in the scope of this study is biogas generated from chicken manure and maize silage. The energy and exergy analysis of the trigeneration system is performed with the aim to achieve higher efficiencies. The efficiencies are presented based on power generation, cogeneration (electricity and cooling) and trigeneration. The overall trigeneration energy and exergy efficiency for the system developed is 64% and 34.51%. The exergy destruction within the system is greatest in the combustion chamber.

Energy modeling of a solar dish/Stirling by artificial intelligence approach

Solar energy is a renewable energy resources that is available across the world. A solar dish/Stirling system means a parabolic dish concentrator and a Stirling engine combined to generate mechanical and/or electrical output power. In this system, the input energy of Stirling engine is provided by sunlight as a source of heat. This study presents the effect of different variables on the power generation and efficiency of the system. In addition, artificial intelligence approach is employed to model a solar dish/Stirling system. For this target, a huge dataset was provided by considering a wide range of input variables. The intelligent methods are group method of data handling (GMDH) type neural network, adaptive neuro-fuzzy inference system (ANFIS) and multilayer perceptron (MLP) neural network (ANN). The MLP and ANFIS are optimized with particle swarm optimization (PSO) and genetic algorithm (GA). The intelligent methods are trained with inputs and targets. The considered input parameters are the ratio of focal point to dish diameter, hour of day, solar radiation, geometric concentration factor and working gas specific constant. The power generation, global efficiency, heat used to run the Stirling cycle, hot Stirling chamber temperature and engine speed are selected to be the targets. The results depict that the intelligent methods operate successfully for energy modeling of the solar dish/Stirling system and the statistical indicators illustrate that the ANFIS-PSO method performs better than the other developed methods.

Methane Disintegration by Water Vapor in a Hot Chamber heated by Using a Microwave Steam Torch

An analysis of the behaviors of water and methane in a hot chamber indicates that methane and water molecules mutually help to disintegrate each other. Oxygen atoms from water disintegrate methane, and methane also self-dissociates. A substantial dissociation of methane by these processes occurs at chamber temperatures higher than T = 1500 K. Methyl (CH3) from these dissociations is very instrumental for the disintegration of water molecules. Meanwhile, the majority of methyl molecules undergo disintegration by oxygen atom, producing an abundance of formaldehyde (CH2O), which self-dissociates immediately to carbon monoxide and hydrogen molecules. Hydroxyl (OH) may convert carbon monoxide to carbon dioxide at a very high temperature of T = 1900 K. An experimental observation shows that methane dissociates in a hot steam chamber heated by a microwave torch. Methane disintegrates completely at temperature higher than 1200 °C (= 1480 K) without any catalyst, as expected from the analytical study.

PRORAČUN KOMORNE SUŠARE ZA PEČURKE

U okviru rada prikazan je primer proračuna i konstrukcije jedne konvektivne komorne sušare sa podovima za sušenje pečurki. Cilj rada je razmatranje više mogućih rešenja za zagrevanje agensa sušenja, sa fokusom na upotrebu obnovljivih izvora energije umesto konvencionalnih goriva, pre svega toplotnih pumpi. Na osnovu definisanog sistema, odabrana je odgovarajuća konstruktivna izvedba sušare.