Heating Tests Research Articles

Visual Inspection of the Heavy-Duty Paint Systems Used in Steel Bridges for Assessing the Level of Fire Damage

After a fire on a steel bridge, a visual inspection is necessary to rapidly determine the need for an emergency response to ensure the structural safety of the bridge and decide whether to re-open the bridge to traffic. In this study, the visual inspection methods of assessing the coated surface were reviewed, as they are crucial for the rapid estimation of the steel temperature reached during the fire, which, in turn, is required for the safety assessment of steel bridges after a fire. An electric furnace heating test was conducted on the steel specimens coated with four types of heavy-duty paint systems for steel bridges, viz., urethane, siloxane, ceramic, and fluorocarbon. The heating temperatures and durations used in the test were 100, 150, 200, 250, 300, 400, 500, and 600 °C at 30 and 60 min. Based on the heating temperature and duration, the paint-film surface conditions (discoloration, blistering, cracking, and delamination) were visually inspected for a qualitative analysis, and factors such as color difference, gloss retention, and pull-off adhesion were quantitatively analyzed. The visual inspection methods used to estimate the temperature of the paint film were reviewed. In addition, considering the reduction in the tension strength of the steel material and the coating durability performance according to the fire temperature, the determinants of the traffic stop–reopening timeline and the repair and reuse of the painting system based on the visual field inspection after a fire were suggested.

Thermal properties of geopolymer composites containing microencapsulated phase change materials

AbstractThe main objective of this paper is to investigate the possibility of using phase change materials (PCMs) as one of the components of a geopolymer and to determine the effect of PCMs addition on the thermal properties of the geopolymer composite obtained. This paper presents the results of geopolymers produced based on fly ash with the addition of microencapsulated PCMs. The geopolymer composites were prepared by adding 0%, 5%, 10%, and 15% PCM, and the curing process was carried out in two temperature ranges: 60°C and 75°C. A PCM with a melting point of 28°C (MicroCapsPCM28‐slurry [Slovenia]) was used. The composites were subjected to thermal conductivity tests in three temperature ranges (0–20°C; 20–40°C; and 30–50°C). This was followed by specific heat and density tests. In addition, the morphology of the geopolymers was determined by scanning electron microscopy. The results showed that the addition of PCMs to the geopolymer materials significantly reduces their thermal conductivity index (compared to the reference sample). Furthermore, the addition of microencapsulated phase‐change materials caused changes in the specific heat of the materials analyzed.

Verification of Bison fission product species conservation under TRISO reactor conditions

When assessing the reliability and predictive capabilities of a simulation tool, code verification is used to ensure that the implemented numerical algorithm is a faithful representation of its underlying mathematical model, including partial differential or integral equations, initial and boundary conditions, and auxiliary relationships. During this process, numerical results in a discrete solution are compared to the analytical solution of the mathematical model. In this paper, the code verification process is applied to one-dimensional spatiotemporal problems that exercise partial differential equation governing the conservation of fission product species (or mass diffusion). Numerical experiments were performed in the Bison fuel performance code to evaluate its predictive capability under various TRISO reactor conditions such as base irradiation and safety heating test conditions for either short- or long-lived fission product species, as well as a case concerning evaporation from the outer surface of a particle. The code predictions were compared with the expected exact results obtained from the analytical expressions, and the fact that they demonstrate the correct analytical behavior provides strong evidence of proper numerical algorithm implementation.

Influence and mitigation of interference by LID and LETID in damp heat and thermal cycling tests on PV modules

Accelerated aging tests as defined in testing standards such as IEC 61215 are important to assure the quality and safety of photovoltaic (PV) modules. The test conditions often contain high temperatures and sometimes carrier injection, which can cause light induced degradation (LID) effects, such as boron-oxygen LID (BO LID) or light and elevated temperature induced degradation (LETID). These effects can interfere with the interpretation of results or produce false fails or passes in certification tests. To address the most severe cases, an option for a regeneration procedure for BO LID after damp heat was recently included in IEC 61215:2021. However, positive performance deviations due to BO LID, as well as the general influence of LETID, are still not excluded. Variations of damp heat and thermal cycling tests on mini-modules built from the monocrystalline passivated emitter and rear cells (PERC) are performed and combined with latest approaches for BO LID regeneration, BO degradation, and LETID temporary recovery. The results show that LETID can superimpose procedures applied for BO LID regeneration but can be easily temporary recovered by one additional step. A combined stabilization procedure, which can exclude influences from both BO LID and LETID on accelerated aging test results, is proposed.

Experimental study on phase change heat storage of valley electricity and economic evaluation of commercial building heating

• A composite PCM of Mg (NO 3 ) 2 6H 2 O/NaNO 3 for an electric boiler was developed. • A modular PCHS unit was constructed and tested, showing stable heating performance. • The heating tests in commercial buildings show 53% savings in operating costs. • The valley power PCHS heating technology shows good application prospects. The application of valley power phase change heat storage (PCHS) in commercial building heating has practical significance for the city's sustainable development. In this study, the experimental study on valley power PCHS is carried out, focusing on the winter heating of a commercial building. An inorganic hydrated salt phase change material (PCM) of magnesium nitrate hexahydrate and sodium nitrate (mass ratio, 92:8) with a phase change temperature of 80–83 °C for an electric boiler was developed. A modular PCHS unit was constructed and tested for 2.5 months from 2018 to 2019 and 4.5 months from 2020 to 2021. The results show that the PCM is stable at about 81 °C after 240 cycles. Moreover, the heat storage and the exothermic power of the PCHS unit reached 10.95 kW and 10.15 kW in the 9-hour test, respectively. The 12-day trial of an office shows that the indoor temperature was maintained at 22–24 °C stably during the daytime working hours (7:00–17:00). Furthermore, the two-year test of the building heating shows that the valley power PCHS can effectively adapt to the outdoor environment changes. The power consumption of the PCHS unit has a negative linear correlation with the ambient temperature. In addition, the operating cost of the PCHS unit system is only 3.5 RMB/month/m 2 , which is less than half of the municipal central heating system cost of 7.5 RMB/month/m 2 , reflecting good economy, and the advantages of energy-saving, emission reduction, and environmental benefits are obvious. The findings of this study provide a valuable supplement for the heating mode and low-carbon energy utilization of urban buildings.

Multi-pass cold rolling and wire drawing process of gadolinium and its magnetocaloric effect

Owing to low ductility of magnetocaloric material (MCM)s, the plastic deformation process is quite challenging, and information available on the deformation process of MCMs is limited. In this study, the cold rolling and wire drawing processes of Gd wire including heat treatment were conducted. Uniaxial compression test of as-cast and heat treated Gd rod was conducted to evaluate the material property. The magnetocaloric effect (MCE) of drawn Gd wire was indirectly measured using a vibrating sample magnetometer (VSM). Pass schedule of cold rolling and wire drawing process for the Gd wire of Ø1.0 was designed. Finite element (FE) simulation of drawing process was conducted to investigate the drawing force for each drawing pass and strain distribution. Friction coefficient between the drawing die and Gd wire was evaluated via FE simulation and drawing experiments using a lubricant. Magnetic properties of the deformed and annealed Gd wire were evaluated and compared. The evaluated magnetic properties have shown that the presented process schedule is reasonable for manufacturing magnetocaloric wire without diminishing the magnetocaloric effect.

Utilization of Polypropylene (PP) Plastic Waste with Waste Oil Palm Empty Brunch for an Alternative Fuels

The need for plastic corresponds with the annual rise in population. Meanwhile, plastic waste that is improperly managed can negatively influence the environment. Therefore, a more promising alternative recycling process is needed to convert this waste into oil by cracking, and the process is possibly assisted by adding empty palm oil bunches. This study examines how modifications in the ratio of oil palm empty bunches to Polypropylene (PP) plastic waste influence the percent liquid produced by cracking and the heating value during the process. It is a completely randomized design (CRD) with variations in the ratio of plastic raw materials: oil palm empty fruit bunches 1:0, 1:1, 1:2, and 1:3 at a temperature of 450°C and 40 minutes duration. This resulted in liquid conversion from cracking of 80% at 1:1 of PP: TTKS 1:1. However, the addition of oil palm empty fruit bunches to polypropylene polymers does not affect the increase in the percent conversion outcomes. The results of the heat test analysis show the value of 6.681 MJ/kg and 1.512 MJ/kg.

Investigation of Heat Transfer Fluids Using a Solar Concentrator for Medium Temperature Storage Receiver Systems and Applications

Solar concentrator collectors have the potential of meeting the medium- and high-temperature thermal energy demands of the world. A heat transfer fluid (HTF) is a vital component of a concentrating system to transfer and store thermal energy. This paper presents the design development of a solar paraboloidal dish concentrator (SPDC) and a study of selected HTFs using the storage receiver system of the concentrator. The locally designed SPDC (diameter 1.21 m and height 0.20 m) has features like light weight, effortless tracking, convenient transportation along with high optical and thermal performance. Three HTFs, silicone oil (SO), engine oil (EO) and ethylene glycol (EG), are selected based on their favorable properties for medium temperature (150–300 °C) applications. The characteristic parameters of HTFs, heating rate (Rh), instant thermal efficiency (ηith) and the overall heat loss coefficient (UL), are illustrated and determined experimentally. A new characteristic parameter, the normalized maximum fluid temperature (Tnf), is also introduced in the paper. In the heating test, the maximum attained temperatures by fluids, SO, EO and EG are found to be 240 °C, 180 °C and 160 °C, respectively. The thermal efficiencies of SO, EO and EG are determined to be 45, 36 and 31%, respectively. The heating rate of 6.56 °C/s is found to be the maximum for SO. Through the cooling test, the overall heat loss coefficient (UL) is computed to be 14 W/mK, which is the least among the three fluids compared. The high thermal performance, environmental safety and chemical stability of silicone oil make it suitable for use in concentrators for medium-temperature heat transfer and storage applications.

Analysis of a Costly Fiberglass-Polyester Air Filter Fire

In September 2020, a fire at a liquefied natural gas (LNG) plant in the Arctic areas of Norway received national attention. In an unengaged air intake, the heat exchanger designed to prevent ice damage during production mode, was supplied hot oil at 260 °C. In sunny weather, calm conditions, and 14 °C ambient temperature, overheating of the unengaged air intake filters (85% glass fiber and 15% polyester) was identified as a possible cause of ignition. Laboratory heating tests showed that the filter materials could, due to the rigid glass fibers carrying the polymers, glow like smoldering materials. Thus, self-heating as observed for cellulose-based materials was a possible ignition mechanism. Small-scale testing (10 cm × 10 cm and 8 cm stacked height) revealed that used filters with collected biomass, i.e., mainly pterygota, tended to self-heat at 20 °C lower temperatures than virgin filters. Used filter cassettes (60 cm by 60 cm and 50 cm bag depth) caused significant self-heating at 150 °C. At 160 °C, the self-heating took several hours before increased smoke production and sudden transition to flaming combustion. Since the engaged heat exchanger on a calm sunny day of ambient temperature 14 °C would result in temperatures in excess of 160 °C in an unengaged air intake, self-heating and transition to flaming combustion was identified as the most likely cause of the fire. Flames from the burning polymer filters resulted in heat exchanger collapse and subsequent hot oil release, significantly increasing the intensity and duration of the fire. Due to firewater damages, the plant was out of operation for more than 1.5 years. Better sharing of lessons learned may help prevent similar incidents in the future.

Influence of Styrene-Butadiene-Styrene Polymer on Local Asphalt Characteristics

In this study the effect of Styrene-Butadiene-Styrene (SBS) polymer on local asphalts was investigated by comparing the performance of unmodified asphalt binder and hot mixture with binder and mixtures modified by SBS polymer modified asphalt (SBS-PMA) and its hot mixture. The comparison was made by evaluating the effectiveness of using different percentages (dosages) of this modifier to produce SBS-PMA. The penetration, ductility, elastic recovery, softening point, flash point, penetration and loss on heat tests for the asphalt binder was used. While, Marshall, indirect tensile strength (ITS), and index of retained strength (IRS) tests for the mixture was used in this study as they are the most available and economic. SBS polymer modifier was added to asphalt binders from Kirkuk governorate (KAT) and LANAZ refineries in Erbil governorate-Kurdistan region- Iraq in four percentages 3%, 5%, 7% and 9% by weight of the asphalt binder. The results showed that SBS polymer modifier significantly enhances the performance of asphalt binder and its hot mixture resulting in enhanced flexible pavements. However, adding 5% SBS leads to the best results of the Marshall test properties, and the moisture damage resistance, which increases the pavement performance against the environmental effects. Comparing the experimental results for both unmodified and 5% SBS polymer modified asphalts, showed that the replacement of the unmodified asphalt by 5% SBS polymer modified asphalt increased the stability by 26.00% for KAT asphalt and 21.34 % for LANAZ asphalt. Also, it increased the TSR by 15.63 % for KAT asphalt and 7.95 % for LANAZ asphalt and the IRS by 11.92% for KAT asphalt and 7.11 % for LANAZ asphalt. The regression analysis technique was applied to fit the mathematical relationship between the SBS polymer percentage and the Marshall stability of the hot mixture. Based on this investigation, the polymer modified asphalt is recommended to be used in new constructed roads to help reduce the amount of deterioration and maintenance cost in the region.

Characteristics of Mortar Containing Oyster Shell as Fine Aggregate.

In this study, oyster shells were processed and classified into sizes equal to or smaller than the fine aggregate threshold, and their engineering properties and fire-resistant performance were examined. The differences in heating weight loss of oyster shell aggregate (OSAs) with different particle sizes were examined using thermogravimetric analysis (TGA). The TGA results showed indicating that the temperature at which decarboxylation reaction started depended on the OSA particle size. The porosity of mortar specimens was analyzed using mercury intrusion porosimetry (MIP). The porosity area and porosity of the OSA-containing mortar increased with decreasing particle size. Mortar fire-resistant boards with heated for 2 h in accordance with the heating conditions of KS F 2257-1(methods of fire-resistant testing for structural element—general requirements) to measure their back-side temperature. The board made with OSA2.5 exhibited 273.2 °C, which is more than 90 °C higher than the back-side temperature of the board with OSA 0.6Under. Such difference was attributed to the greater heat transfer delay caused by higher porosity, porosity area, and specific surface area in OSAs with small particle sizes. The TGA results combined with the heating test results suggested that CO2 would be generated at different temperatures in boards containing OSAs with different particle sizes because of the differences in the endothermic reaction temperature.

Electric field driven printing of repeatable random metal meshes for flexible transparent electrodes

Electrohydrodynamic jet printing technology is recognized as one of the most desirable solutions for direct printing of metal meshes. However, electrohydrodynamic jet printing technology makes it difficult to achieve reproducible printing of random metal meshes due to the low stability as well as controllability of the cone jets. Here, a simple and cost-effective printing technique for fabricating flexible transparent electrodes with controlled knot-free random metal meshes was proposed. The simple and green fabrication of transparent electrodes with different random metal meshes was achieved by precisely adjusting the printing process parameters. The sheet resistance variation of the manufactured FTEs with random metal mesh was less than 10 %, showing excellent reliability and stability and environmental adaptability, demonstrating better optoelectronic performance, after 1000 cycles of bending, 180 cycles of adhesion testing, and 72 h of damp heat testing. More importantly, the diffraction experiments show that the fabricated random metal meshes can reduce the negative effects of higher-order diffraction and eliminate the moiré fringe phenomenon. A flexible touch screen application demonstrated the practicality of manufactured FTEs with random metal mesh (area: 80 mm × 130 mm, sheet resistance: 16 Ω/sq, transmittance: 86 %). The proposed method offers a very promising strategy for the efficient and green integrated fabrication of random metal meshes.

Determination of the Rational Mode of Mutual Loading of Traction Engines of Main Electric Locomotives

Purpose. The actual state of many of the existing testing stations for traction electric machines does not meet modern requirements for the organization of repair and technical control. At most of these stations, mutual loading stands with low energy efficiency are used. The purpose of the work is to determine the rational mode of loading electric traction machines, which will ensure a decrease in the total power of the power sources of the test station, an increase in energy efficiency and the quality of tests. Methodology. The methodological basis of the work is the general theoretical provisions and principles of the systematic approach of theoretical electrical engineering, theoretical mechanics, the theory of electric machines and converters. The substantiation of the energy and electromechanical principles of mutual loading of traction electric machines is performed using the basics of generalization and systematization of physical quantities and concepts, the theory of electric circuits, the theory of mechanical systems, and the theory of electric machines. The analysis of thermal processes and energy parameters of the electric machine test system was performed using the theory of heating a homogeneous solid body and known methods of calculating thermal circuits. The results of theoretical studies have been confirmed experimentally. Findings. The analysis of the expression for determining the energy efficiency coefficient of heating the windings of traction electric machines, obtained in the work, shows that the starting current is the most rational when testing the traction motors of electric rolling stock of mainline transport for heating. The use of this load current allows reducing the electricity consumption for tests by 20-30% (compared to the hourly mode) without reducing the quality of tests, as well as reduces the time of heating tests by three to four times. Originality. The expediency of conducting the heating tests of traction motors of main electric rolling stock with a load current equal to the current of the start-up mode has been scientifically substantiated, which ensures the energy efficiency increase of the tests and a corresponding reduction in the total cost of electricity for acceptance tests. The method of analytical determination of the weighting coefficients of influence on the temperature excess of the armature winding of electric losses was proposed, the use of which allows evaluating the influence of the mutual loading modes of the tested traction electric machines on the discrepancy degree of the thermal loads of their armature windings. Practical value. The results of theoretical studies allow determining the rational modes of mutual loading of traction electric machines, which make it possible to reduce the electricity consumption for conducting their heating tests and shorten the time of conducting heating tests. In addition, it becomes possible to propose a method of evaluating the quality of acceptance tests of traction electric machines, which takes into account the discrepancy degree in the thermal loads of the windings.

The Temperature and Pore Pressure Distribution of Lightweight Aggregate Concrete Slabs Exposed to Elevated Temperatures

Concrete has good fire resistance. However, once exposed to rapidly increasing temperatures, concrete may suffer from thermal stress-induced spalling or pore pressure-induced spalling. Compared with normal-weight concrete (NWC), lightweight aggregate concrete (LWAC) has a low thermal conductivity and is more prone to cause a higher temperature gradient under the action of high temperatures. This poses a hidden concern to the fire safety of general LWAC structures. Therefore, this study aimed to investigate the temperature and the pore pressure distribution of LWAC slabs under one-dimensional heating tests and to compare them with NWC slabs. The test variables were the moisture content of the specimen (oven-dried and air-dried), target temperature (600 and 800 °C), and heating rate (5 and 10 °C/min). The temperature and the pore pressure distributions were measured separately by thermocouples and pressure gauges embedded in different positions of the specimen. The test results show that the maximum pore pressure (Pmax) of the LWAC slabs was generally higher than that of the NWC slab at a distance of 10 mm from the heated surface when the specimen was in an oven-dried state. However, at 30 and 50 mm from the heated surface, the Pmax of the NWC slab tended to be higher. This shows that the Pmax distribution of the LWAC slab was closer to the heated surface when the specimen was in an oven-dried state, while the Pmax of the NWC slab occurred further from the heated surface. Further, as the heating rate increased, a higher pore pressure was generated inside the specimen and the pressure rose more rapidly. In particular, at a target temperature of 800 °C and a heating rate of 10 °C/min, the corner spalling phenomenon appeared on the air-dried LWAC slab.

Theoretical analysis and design of fire protection and thermal insulation of parallel wire or strand cables

In this study, a transient heat flow model has been established for parallel wire or strand cables at high temperature by employing the lumped thermal mass approach, and the numerical solution of the surface temperature as a function of time in each layer of the steel wire or strand inside the cable was calculated. Accuracy of the theoretical method is verified through uniform heating test of 73Φ15.7 mm steel strand cable. The results calculated show that temperature field inhomogeneity of cable section is overestimation on the condition that heat conduction inside the cable is not considered. Considering heat conduction or not, the maximum temperature difference of the core steel stand at the same time point is 373 . Unprotected 73Φ15.7 mm cable is damaged in only 12 min in UL1709 fire, and arrangement of fire protection layer around cable can effectively retard the temperature rise of cable surface. The experimental results are in good agreement with the theoretical calculation values in early stage of fire, and the temperature difference between the two is within 10%. Besides, the numerical calculations were analyzed in accordance with the fire protection requirements limiting the surface temperature of cables. It was observed that the minimum thickness of the fire protection layer required to meet the PTI DC45.1-12 standard was linearly related to the numerical value of the section factor of the outermost layer of steel wires or steel strands in the equivalent model, and the slope of the function was approximately equal to the conduction coefficient of fire protection layer, as the cable was subjected to fire for 30 min. Further, based on this, a simple method was proposed to calculate the minimum thickness of the fire protection layer for parallel wire or strand cables.

Performance and mechanism evaluation of dopamine-hexamethylene diamine-iron tetraoxide composite rubber powder incorporated styrene-butadiene-styrene modified asphalt

• The microwave absorber PDA-HDA-Fe 3 O 4 was synthesized by a one-pot facile method. • PDA-HDA-Fe 3 O 4 /SBS-RP-MA realized improved viscoelasticity and rutting resistance. • PDA-HDA-Fe 3 O 4 /SBS-RP-MA had high microwave absorption. • Some functional groups of PDA-HDA dispersed agglomeration of Fe 3 O 4 in asphalt. In order to improve the mechanical properties, high temperature rheological properties, and self-healing of modified asphalt, the microwave absorber iron tetraoxide (Fe 3 O 4 ) was modified and polydopamine-hexamethylene diamine-Fe 3 O 4 (PDA-HDA-Fe 3 O 4 ) was prepared, which was compounded with rubber powder/styrene butadiene styrene modified asphalt (RP-SBS-MA). Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy analyses confirmed that chemical composition and crystal morphology of PDA-HDA-Fe 3 O 4 remained unchanged. Scanning electron microscopy and atomic force microscopy revealed that the surface morphology of the modified Fe 3 O 4 was altered which could increase the mechanical interlocking interaction with the base asphalt. Dynamic shear rheometer test showed that at 46 °C, the storage modulus and loss modulus of 1 %PDA-HDA-Fe 3 O 4 /RP-SBS-MA were respectively 61.96 % and 69.65 % higher compared to that of RP-SBS-MA. The results of the multi-stress creep recovery test showed that at 3.2 kPa, the strain of 1 %PDA-HDA-Fe 3 O 4 /RP-SBS-MA was reduced by 54.16 % compared to that of RP-SBS-MA. Microwave heating tests analysis showed that the temperature of 1 %PDA-HDA-Fe 3 O 4 /RP-SBS-MA was 20.48 % and 2.41 % higher than those of RP-SBS-MA and 1 %Fe 3 O 4 /RP-SBS-MA, respectively. This was attributed to the improved microwave absorption capacity of the modified asphalt upon the addition of PDA-HDA-Fe 3 O 4 . These convincing results of the newly prepared PDA-HDA-Fe 3 O 4 /RP-SBS-MA could be envisioned of great promise for designing advanced functional asphalts for targeted applications.

48.2: Formation of potential barriers at grain boundaries in multicomponent ZnO‐based transparent thin films

The article discusses the reasons for the deterioration of the electrical characteristics of ZnO‐based thin films in conditions of both high humidity and high ambient temperatures. Based on the standard damp heat test, in which thin samples subjected to temperature 85�C and relative humidity 85 % for 1000 h, it is shown that the stability of electrical performances of the transparent ZnO‐based films may be increased with an increase in the temperature of their deposition, which, in turn, leads to the formation of denser compact films. It is shown that the porous structure formed in ZnO‐based films, which leads to poor thermal stability, is due to the relatively low mobility of adatoms on the growing surface during film deposition at relatively low substrate temperatures. The analysis of the obtained data shows that the key factor determining both the composition and state of grain boundaries (GBs) in nanocrystalline ZnO‐based films, as well as the formation of potential barriers at the GBs is the possible segregation of impurity materials at the GBs, which depends on the arrangement of impurity atoms with respect to Zn in the series of metal activity. The conditions for the amorphization of complex composite oxide structures are considered.

Analysis and Design of Flexible-Surface Induction-Heating Cooktop With GaN-HEMT-Based Multiple Inverter System

The flexible induction cooktop, which can provide an unlimited cooking area, utilizes a cost-effective method in which one inverter shares multiple working coils. However, this method has resulted in consumer needs such as reducing both the initial pot detection time and the noise caused by the relay operation. This article presents a hardware implementation and control method for a flexible induction cooktop with multiple GaN-HEMT-based inverter systems. As one way to meet consumer needs, this implementation method does not require a relay and offers the advantage of real-time pot detection and noise minimization. However, the inverter design should include the magnetic coupling effect while maintaining high performance and high power density. This article proposes an inverter design method considering the limited space and an implementation method that minimizes the effect of magnetic coupling without an additional power stage. The feasibility of the proposed implementation method is evaluated based on the results of a heating test with a 3.3 kW prototype.

Study and Analysis of Different Absorber Geometry of Compound Parabolic Solar Collector and its Effect on Thermal Efficiency for Heating Water for Sanitary Use

Abstract: This project is focused on carrying out a study of the absorber geometry of the parabolic solar collector compound for heating water for sanitary use, to evaluate the temperature gradient between the inlet and outlet of the water of this concentraDDDtor collector, and the efficiency achieved according to the absorber configuration to later compare it with collectors with a conventional flat absorber surface. The parabola of the reflector of the composite parabolic solar collector was obtained considering the circular absorber, with a concentration ratio of 4 plus 10% of this, to consider a truncation of the reflector, the circular absorber was configured with a small absorber plate of aluminum which has a thermal conductivity of 401 W /mK The values obtained experimentally in the collector were based on the data collected in the field files. It was considered to experience the heating of water on different days with the climatic conditions, cloudy, partially cloudy and sunny, with a totally clear sky. The water heating tests were carried out with two types of geometric configuration of the absorber of the composite parabolic solar collector; circular absorber and configured circular absorber, with which a water outlet temperature of 61 ° C and 76 ° C and a thermal efficiency of 60% respectively were obtained, these results were presented taking into account a climatic condition (sunny day) approximately the same for the two absorber configurations, and with average values of wind speed, ambient temperature and solar radiation.

A Novel Slug Heat Test Theoretical and Indoor Model Research for Determining Thermal Property Parameters of Aquifers and Rock-Soil Skeletons

As important parameters for characterizing heat transfer, thermal property parameters of aquifers and rock-soil skeletons have important research significance in the development and utilization of geothermal resources. The slug heat test is inspired by the slug test, and the heat is instantaneously excited in the test well so as to change the temperature of test section in the test well instantaneously. Based on the thermal radial convection-dispersion theory and the principle of heat conservation, the theoretical model of the slug heat test is established, and the model is solved by Laplace transform and inverse transform to obtain multiple sets of standard curves under different conditions. The slug heat tests were conducted in the indoor model, the slug heat test data under different hydrodynamic conditions were fitted with the standard curves and the thermal property parameters, including effective thermal conductivity, stagnant thermal conductivity, thermal mechanical dispersion coefficient, thermal dispersive degree, thermal diffusivity, heat capacity of aquifer, heat capacity and thermal conductivity of rock-soil skeletons, were accurately obtained. The test results are in good agreement with the empirical values. Meanwhile, the effective thermal conductivity of the aquifer also clearly increases with the increase of flow rate. The excitation temperature difference had little effect on the effective thermal conductivity of the aquifer. At the same time, numerical simulation methods are used to establish a numerical model consistent with the indoor test model, and the numerical model is assigned with the thermal property parameters obtained from the indoor slug heat test, and the measured values of temperature changes in the test well during the slug heat test under different hydrodynamic and excitation strength conditions are compared with the simulated values for verification. The research results show that the slug heat test has the characteristics of high applicability, simple operation and rapid testing, and can effectively determine the thermal properties parameters of aquifers and rock-soil skeletons.