Статті в журналах: "Thermal losse"

1

Logachevsky, Ivan A. "THERMAL IMAGE ANALYSIS." SOFT MEASUREMENTS AND COMPUTING 8, no. 57 (2022): 18–30. http://dx.doi.org/10.36871/2618-9976.2022.08.002.

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The equipment of thermal stations and heating networks, which is subject to corrosion and is often far from new, loses its original characteristics over time. Such processes, potentially leading to heat losses and coolant leaks, can lead to significant financial and environmental consequences. Infrared thermography is one of the effective problemsolving methods that helps to detect defects and reduce risks. This article discusses some details of the current project for the analysis of thermal images using convolutional neural networks.

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2

Yuan, Hong-Chun, and Xue-Xiang Xu. "Squeezed vacuum state in lossy channel as a squeezed thermal state." Modern Physics Letters B 29, no. 33 (December 10, 2015): 1550219. http://dx.doi.org/10.1142/s021798491550219x.

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In this paper, we alternatively study the evolution of squeezed vacuum state (SVS) in lossy channel by virtue of the phase space method. By using the formula of Wigner function (WF) in coherent representation and [Formula: see text] representation of quantum density operator, the WF formula in lossy channel is derived. After obtaining the analytical expressions of the WFs of the lossy SVS and the squeezed thermal state (STS), we further prove the fact that the lossy SVS is equivalent to a kind of STS. Our result is useful in dealing with the light field transmission problems in the presence of losses.

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3

Kosiński, Piotr, and Robert Wójcik. "An Impact of Air Permeability on Heat Transfer through Partitions Insulated with Loose Fiber Materials." Applied Mechanics and Materials 861 (December 2016): 190–97. http://dx.doi.org/10.4028/www.scientific.net/amm.861.190.

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The paper presents the problem of windwashing in partitions including air permeable thermal insulations. There are technical solutions, which deliberately accept the filtration of air in the insulating layer, guided by the necessity of possible drying of building materials. Some scientific papers even suggest that the air infiltration decrease the heat losses through ventilation. In result there occur heat losses in building heat balance which are underestimated and therefore difficult to take into account during calculations. Heat changes on the inner surface of the building partition occur with a delay to the initiation of the wind. However, even the short-term local wind speed loads on thermal insulations result in temperature decreasing and therefore possible condensation on the inner surface of the building partition. The article presents laboratory measurements of air permeability of loose mineral wool and laboratory investigation of the impact of air filtration on heat transfer in lightweight partitions filled with loose thermal insulation.

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4

Yamashita, Hiroyuki, Hidefumi Fujimoto, Masahiko Fujimoto, Tatsuya Tanaka, and Hiroyuki Yamamoto. "OS1-3 Thermal Efficiency improvement by increasing compression Ratio and Reducing Cooling Loss(OS1: Ultimate thermal efficiency,Organized Session Papers)." Proceedings of the International symposium on diagnostics and modeling of combustion in internal combustion engines 2012.8 (2012): 36–42. http://dx.doi.org/10.1299/jmsesdm.2012.8.36.

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5

Zhu, Fang-Long, Qian-Qian Feng, Qun Xin, and Yu Zhou. "Thermal degradation process of polysulfone aramid fiber." Thermal Science 18, no. 5 (2014): 1637–41. http://dx.doi.org/10.2298/tsci1405637z.

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Polysulfone aramid fiber is one kind of high temperature fibers. In the paper, thermal degradation behavior and kinetics of polysulfone aramid fiber were investigated by thermogravimetric analysis and differential thermogravimetric at different heating rates under nitrogen and air, respectively. The experimental results show that its initial degradation temperature is 375?C in nitrogen and 410?C in air at heating rate of 10 K/min. When temperature went to 800?C, the fiber loses all mass in air. The mass losses in the stage showed that degradation of polysulfone aramid occurs in two-step process as could be concluded by the presence of two distinct exothermic peaks in differential thermogravimetric curves.

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6

Tournemenne, Robin, and Juliette Chabassier. "A Comparison of a One-Dimensional Finite Element Method and the Transfer Matrix Method for the Computation of Wind Music Instrument Impedance." Acta Acustica united with Acustica 105, no. 5 (July 1, 2019): 838–49. http://dx.doi.org/10.3813/aaa.919364.

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This work presents a computation tool for the calculation of wind instrument input impedance in the context of linear planar wave propagation with visco-thermal losses. The originality of the approach lies in the usage of a specific and simple 1D finite element method (FEM). The popular Transfer Matrix Method (TMM) is also recalled and a seamless formulation is proposed which unifies the cases cylinders vs. cones. Visco-thermal losses, which are natural dissipation in the system, are not exactly taken into account by this method when arbitrary shapes are considered. The introduction of an equivalent radius leads to an approximation that we quantify using the FEM method. The equation actually solved by the TMM in this case is exhibited. The accuracy of the two methods (FEM and TMM) and the associated computation times are assessed and compared. Although the TMM is more efficient in lossless cases and for lossy cylinders, the FEM is shown to be more efficient when targeting a specific precision in the realistic case of a lossy trumpet. Some additional features also exhibit the robustness and flexibility of the FEM over the TMM. All the results of this article are computed using the open-source python toolbox OpenWind.

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7

Kaiser, Waldemar, Michael Haider, Johannes A. Russer, Peter Russer, and Christian Jirauschek. "Markovian Dynamics of Josephson Parametric Amplification." Advances in Radio Science 15 (September 21, 2017): 131–40. http://dx.doi.org/10.5194/ars-15-131-2017.

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Abstract. In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

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8

Pashentsev, A. I., A. A. Garmider та L. V. Pashentsenva. "МЕTHODOLODGICAL APPROACH TO ESTIMATION OF THERMAL LOSSES OF THERMAL NETWORK TAKING INTO THERMAL INTERFERENCE". Construction economic and environmental management 81, № 4 (2022): 13–22. http://dx.doi.org/10.37279/2519-4453-2021-4-13-22.

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The author’s vision of a methodical approach to estimation of thermal losses of a channel-less thermal network is presented at the base, which is the determination of specific thermal losses caused by the thermal interference process. There was carried out systematization of existing approaches to estimation of thermal losses of heat networks with identification of positive and negative features, the logical scheme of thermal interference process implementation at movement of high-temperature heat carrier in heat supply line of heat network is justified. Mathematical interpretation of methodical approach to estimation of thermal losses of channel-less heat networks is presented taking into account thermal interference, which includes twelve successively performed calculation stages.

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9

Kosiński, Piotr, Robert Wójcik, Dariusz Skoratko, and Shady Attia. "An impact of moisture content on the air permeability of the fibrous insulation materials." Journal of Physics: Conference Series 2069, no. 1 (November 1, 2021): 012205. http://dx.doi.org/10.1088/1742-6596/2069/1/012205.

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Abstract Fibrous materials are characterized by good thermal properties, but are susceptible to air filtration. Effective air and wind protection of the building envelope eliminate the problem of air penetration of fibrous materials, but there are still many buildings where this protection has not been applied. Authors investigated the effect of moisture content on the air permeability of chosen loose fibrous materials: mineral wool, wood wool and cellulose fibers. The presented results may be used to simulate and calculate heat loses in existing buildings.

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10

Joshi, Pratik M., Shekhar T. Shinde, and Kedarnath Chaudhary. "A Case Study on Assessment Performance and Energy Efficient Recommendations for Industrial Boiler." International Journal of Research and Review 8, no. 4 (April 6, 2021): 61–69. http://dx.doi.org/10.52403/ijrr.20210410.

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As India is a developing country, industrialization is increasing day by day and there is a great need for industry energy audit. Audit helps to maintain and save energy from being wasted and helps in achieving highest efficiency of industrial equipment. This paper contains an actual industry audit report on boiler performance. This paper contains a report on Thermal analysis of boilers, thermal skin heat loss of boilers, O2 percentage control in flue gases to standard values, effect of coal additive, etc. This paper also contains a report on waste heat recovery options for thermal boiler, flue efficiency monitor, infrared thermometer, ultrasonic peak detector IR thermal imager. These equipment are used for energy assessment of boilers. Thermography survey of boiler surface is carried out to estimate the radiation and the other losses and the result of this total annual saving after insulation repairing or maintenance is Rs.8.48 lakh and investment is around Rs.6.31 lakh. Economizer performance of both the ISGEC and Thermax boiler can be improved with the help of suggested measures. It will help to save approximately rupees Rs.38.42 Lakh annually and investment on maintenance cost is negligible. In short, this paper deals with assessment of all boilers, evaluates their efficiencies and losses to identify energy saving opportunities and presents them in a report with their payback periods. Keywords: Energy, Energy audit, assessment, boiler.

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11

JUNGA, P., and P. TRÁVNÍČEK. "Analyses of the thermal characteristics of construction details at the biogas station plant." Research in Agricultural Engineering 60, No. 3 (September 12, 2014): 121–26. http://dx.doi.org/10.17221/29/2012-rae.

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This paper presents analyses of the thermal characteristics of construction details at the biogas station plant, in order to investigate the impact of the thermal bridges on the energy consumption. Thermal bridges in the building’s envelope remain a weak spot in the constructions. Heat losses of biogas plant constructions are a negative phenomenon and cause wasting of energy. If we eliminate thermal bridges in constructions we can achieve a reduction of general heat losses and save a certain amount of heat energy for utilization. Correct structural design of construction details has impact on general environmental and economic characteristics of biogas plant.

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12

Andonova, A., A. Aleksandrov, K. Peichev, and R. Georgiev. "Thermography evaluation of a bioreactor’s heat loss to surrounding environment." Electronics and Communications 16, no. 3 (March 28, 2011): 181–84. http://dx.doi.org/10.20535/2312-1807.2011.16.3.266780.

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The thermal losses of a bioreactor have to be compensated for fermentation process maintaining (the temperature first of all). In order to decrease consume heat by the bioreactor and to make up thermal losses a heat insulation has been performed. In this paper a noncontact and nondestructive thermography qualification of the thermal losses and evaluation of the heat insulation’s quality for an anaerobic bioreactor is offered. By using software Researcher a thermography analysis for three different cases (without compensated heat losses; with one layer of thermal insulation; with two layers thermal insulation) is carried out. The received results show the advantages of the used approach for qualification of different kind of heat insulations

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13

Smusz, Robert, and Michał Korzeniowski. "Experimental investigation of thermal bridges in building at real conditions." E3S Web of Conferences 70 (2018): 03013. http://dx.doi.org/10.1051/e3sconf/20187003013.

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In recent time the energy consumption of buildings may be reduced by the application of modern technologies in the construction industry. Modern building materials ensure a reduction of heat losses. However, studies show that thermal bridges may cause up to 30% of the additional heat losses through the building envelope. Therefore, a one key aspect in assessing the real thermal state of buildings is the identification of the heat losses through thermal bridges. The analytical, experimental and numerical methods are used for the assessment of thermal transmittance value of building. In the paper the authors present the experimental research on heat losses through the building under real winter conditions. Infrared thermovision technique has been used to the thermal bridges assessment in situ. IR thermography technique allowed the determination of the influence of thermal bridges on the additional heat losses. For the obtaining the surface emissivity the measurements have been also performed with the use of thermocouples system. Numerical validation of the experimental results has been performed.

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14

Zigo, Jaroslav, Peter Rantuch, and Karol Balog. "Thermal Decomposition of Loose-Fill Cellulose Thermal Insulation." Advanced Materials Research 1001 (August 2014): 379–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1001.379.

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This article deals with thermal degradation of cellulose insulation. The sample of commercially available loose-fill cellulose insulation was tested in electrically heated hot air furnace modified for thermogravimetric analysis. Weight loss, weight loss rate and CO/CO2 ratio was measured, while the sample was heated from room temperature to 530°C. Particular phases of the thermal degradation process of cellulose insulation were identified and explained. The most rapid changes caused by thermal decomposition of loose-fill cellulose insulation were reported in temperature range 270°C – 380°C. The weight loss rate reached its maximum in 308°C, which was equal to 0,198g.min-1. Two temperature ranges in which the yield of CO was higher than the yield of CO2 were detected.

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15

Farrenkopf, Felix, Andreas Schwarz, Thomas Lohner, and Karsten Stahl. "Analysis of a Low-Loss Gear Geometry Using a Thermal Elastohydrodynamic Simulation including Mixed Lubrication." Lubricants 10, no. 9 (August 24, 2022): 200. http://dx.doi.org/10.3390/lubricants10090200.

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Low-loss gears are an interesting design approach for increasing the efficiency and thermal load limits of gearboxes. The loss-optimized gear geometry concentrates sliding around the pitch point, which results in low load-dependent gear power losses. In this study, a method for modeling transient EHL (elastohydrodynamically lubricated) contacts in gear mesh considering mixed lubrication and thermal effects is introduced and applied to analyze the tribological behavior of a low-loss gear geometry. Special focus is placed on local frictional losses to analyze the role of the thermal effects of the gear mesh. Although a thermal reduction in fluid friction is observed, the overall effect on total frictional losses of the low-loss gear geometry is evaluated to be very small. The edge geometry strongly influences the lubricant film thickness and frictional power losses.

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16

Cheng, H. C., C. H. Wu, and S. Y. Lin. "Thermal and Electrical Characterization of Power Mosfet Module Using Coupled Field Analysis." Journal of Mechanics 35, no. 5 (September 18, 2019): 641–55. http://dx.doi.org/10.1017/jmech.2019.19.

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ABSTRACTTemperature resulting from the joule heating power and the turn-on and turn-off dissipation of high-power, high-frequency applications is the root cause of their thermal instability, electrical performance degradation, and even thermal-fatigue failure. Thus, the study presents thermal and electrical characterizations of the power MOSFET module packaged in SOT-227 under natural convection and forced convection through three-dimensional (3D) thermal-electric (TE) coupled field analysis. In addition, the influences of some key parameters like electric loads, ambient conditions, thermal management considerations (heat sink, heat spreader) and operation conditions (duty cycle and switching frequency) on the power loss and thermal performance of the power module are addressed. The study starts from a suitable estimation of the power losses, where the conduction losses are calculated using the temperature- and gate-voltage-dependent on-state resistance and drain current through the device, and the switching losses are predicted based on the ideal switching waveforms of the power MOSFETs applied. The effectiveness of the theoretical predictions in terms of device’s power losses and temperatures is demonstrated through comparison with the results of circuit simulation and thermal experiment.

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17

Diban, Bassel, and Giovanni Mazzanti. "The Effect of Insulation Characteristics on Thermal Instability in HVDC Extruded Cables." Energies 14, no. 3 (January 21, 2021): 550. http://dx.doi.org/10.3390/en14030550.

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This paper aims at studying the effect of cable characteristics on the thermal instability of 320 kV and 500 kV Cross-Linked Polyethylene XLPE-insulated high voltage direct-current (HVDC) cables buried in soil for different values of the applied voltages, by the means of sensitivity analysis of the insulation losses to the electrical conductivity coefficients of temperature and electric field, a and b. It also finds the value of dielectric loss coefficient βd for DC cables, which allows an analytical calculation of the temperature rise as a function of insulation losses and thermal resistances. A Matlab code is used to iteratively solve Maxwell’s equations and find the electric field distribution, the insulation losses and the temperature rise inside the insulation due to insulation losses of the cable subjected to load cycles according to CIGRÉ Technical Brochure 496. Thermal stability diagrams are found to study the thermal instability and its relationship with the cable ampacity. The results show high dependency of the thermal stability on the electrical conductivity of cable insulating material, as expressed via the conductivity coefficients of temperature and electric field. The effect of insulation thickness on both the insulation losses and the thermal stability is also investigated.

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18

Alghamdi, Abdulrahman, Hamzah Alharthi, Abdulelah Alanazi, and Mohammad Halawani. "Effects of Metal Fasteners of Ventilated Building Facade on the Thermal Performances of Building Envelopes." Buildings 11, no. 7 (June 24, 2021): 267. http://dx.doi.org/10.3390/buildings11070267.

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Thermal bridging in the building envelope is one of the main causes of energy losses, even in high-efficiency ventilated building façades. In this study, the effects of point-thermal bridges attributed to metal fasteners on the heat transferred through different types of bricks were predicted. All the structural details of the substrate wall were included as well. This was accomplished with a multi-scale, finite element modelling approach used to enhance the thermal insulation efficiency of the building envelope. The effects of the metal fastener length, diameter, density and location were examined to elucidate any opportunity to minimize the heat losses caused by thermal bridging. The results demonstrated that increases in the lengths of fasteners yielded higher energy losses compared with those generated when the diameter increased. Additionally, metal fasteners caused higher energy losses by up to 30% when fixed on mortar, compared with the energy losses incurred when they were fixed on bricks.

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19

Williams, D. F. "Thermal noise in lossy waveguides." IEEE Transactions on Microwave Theory and Techniques 44, no. 7 (July 1996): 1067–73. http://dx.doi.org/10.1109/22.508639.

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20

Thibblin, Anders, and Ulf Olofsson. "A study of suspension plasma-sprayed insulated pistons evaluated in a heavy-duty diesel engine." International Journal of Engine Research 21, no. 6 (October 3, 2019): 987–97. http://dx.doi.org/10.1177/1468087419879530.

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Thermal barrier coatings can be used to reduce the heat losses in heavy-duty diesel engines. A relatively new coating method for thermal barrier coatings is suspension plasma-spraying. Single-cylinder engine tests have been run to evaluate how heat losses to piston, cylinder head and exhausts as well as the specific fuel consumption are influenced by coating pistons with two different suspension plasma-sprayed thermal barrier coatings and one atmospheric plasma-sprayed thermal barrier coating, and comparing the results to those from an uncoated steel piston. The two suspension plasma-sprayed thermal barrier coatings showed reduced heat losses through the piston and less heat redirected to the cylinder head compared to conventional atmospheric plasma-sprayed thermal barrier coating, while one suspension plasma-sprayed coating with yttria-stabilized zirconia as top coat material showed increased exhaust temperature. However, the indicated specific fuel consumption was higher for all tested thermal barrier coatings than for an uncoated engine. The best performing thermal barrier coating with respect to indicated specific fuel consumption was a suspension plasma-sprayed coating with gadolinium zirconate as top coat material.

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21

Jadhav, Sandhya, and V. Venkatraj. "Thermal losses in central receiver solar thermal power plant." IOP Conference Series: Materials Science and Engineering 377 (June 2018): 012008. http://dx.doi.org/10.1088/1757-899x/377/1/012008.

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22

Cheng, Hsien-Chie, Siang-Yu Lin, and Yan-Cheng Liu. "Transient Electro-Thermal Coupled Modeling of Three-Phase Power MOSFET Inverter during Load Cycles." Materials 14, no. 18 (September 19, 2021): 5427. http://dx.doi.org/10.3390/ma14185427.

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This study introduces an effective and efficient dynamic electro-thermal coupling analysis (ETCA) approach to explore the electro-thermal behavior of a three-phase power metal–oxide–semiconductor field-effect transistor (MOSFET) inverter for brushless direct current motor drive under natural and forced convection during a six-step operation. This coupling analysis integrates three-dimensional electromagnetic simulation for parasitic parameter extraction, simplified equivalent circuit simulation for power loss calculation, and a compact Foster thermal network model for junction temperature prediction, constructed through parametric transient computational fluid dynamics (CFD) thermal analysis. In the proposed ETCA approach, the interactions between the junction temperature and the power losses (conduction and switching losses) and between the parasitics and the switching transients and power losses are all accounted for. The proposed Foster thermal network model and ETCA approach are validated with the CFD thermal analysis and the standard ETCA approach, respectively. The analysis results demonstrate how the proposed models can be used as an effective and efficient means of analysis to characterize the system-level electro-thermal performance of a three-phase bridge inverter.

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23

Sreeshobha, Eniganti, and Raddymalla Linga Swamy. "Evaluation of insulated gate bipolar transistor valve converter based unified power flow controller reliability and efficiency." International Journal of Power Electronics and Drive Systems (IJPEDS) 13, no. 4 (December 1, 2022): 2348. http://dx.doi.org/10.11591/ijpeds.v13.i4.pp2348-2356.

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The effectiveness and reliability of the unified power flow controller (UPFC) are determined by the insulated gate bipolar transistor (IGBT) valve. Thermal losses, conduction losses, and switching losses in the IGBT valve all affect the efficiency of UPFC. The failure rate of the converter valves is influenced by junction temperature, which has an impact on the converter's reliability. Piecewise linear electrical circuit simulation (PLECS) was used to simulate two IGBT valve-based converter legs working at 12000 Hz, part number GT30F123. By reference to the switching characteristics produced by PLECS, switching losses, conduction losses, and thermal losses are analyzed. Simulation results are corroborated with analytical measurements. The chance of achieving 100%, 50%, and 0% functioning modes are among the reliability indices that are analyzed. The chance of achieving a hundred percent, fifty percent, or zero percent functioning mode is assessed. The frequency of achieving the state probability and mean time to failures (MTTF) are obtained from probabilities using the Markov model. The thermal losses, failure rate, and lifetime of the UPFC are all quantified to give a complete picture of the UPFC's performance.

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24

Carmona, R., F. Rosa, H. Jacobs, and M. Sa´nchez. "Evaluation of Advanced Sodium Receiver Losses During Operation of the IEA/SSPS Central Receiver System." Journal of Solar Energy Engineering 111, no. 1 (February 1, 1989): 24–31. http://dx.doi.org/10.1115/1.3268282.

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This article presents the measurements and experiments conducted on the external receiver: the so-called Advanced Sodium Receiver (ASR) of the Small Solar Power Systems (SSPS) Project of the International Energy Agency (IEA) in southern Spain. The basis of this experiment was to provide loss measurements for later use in determining receiver performance. The tests to evaluate thermal losses consisted in operating the receiver with the doors open and circulating the sodium in normal and reverse flow without providing any incident power from the heliostat field (flux-off technique). In this way, total thermal losses are calculated as the energy lost by the sodium. Radiative losses have been calculated based on theoretical calculations and some results have been compared with infrared thermography measurements. Conductive losses are small and have been estimated by flux-off experiments with the receiver doors closed. Convective losses were evaluated subtracting radiative and conductive losses from the total thermal losses. Optical losses were assessed using absorptance measurements of the receiver coating. A simplified analytical model has been developed to calculate losses and ASR efficiency during operation. In spite of the method’s simplicity, the results are very similar to those found by other investigators, verified simulation programs, and test results.

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25

Kadlec, R. H. "Thermal environments of subsurface treatment wetlands." Water Science and Technology 44, no. 11-12 (December 1, 2001): 251–58. http://dx.doi.org/10.2166/wst.2001.0837.

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Treatment wetlands are solar powered ecosystems, resulting in annually cyclic temperatures. This paper reports data and models for temperatures and energy flows for subsurface flow wetlands. The water temperature seasonal cycle follows the air temperature during unfrozen conditions, with small hysteresis. Winter under-ice water temperatures are approximately 2°C. The energy balance is dominated by radiation to and from the wetland, and evaporative losses. Sensible heat flows, conduction and convection are of smaller magnitude. Lateral energy losses were measured to be small. Vertical gains and losses were also small, but of importance in winter conditions. A simple model for ice formation shows that ice formation may be held to an acceptable minimum by addition of mulch or by early snow accumulation.

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26

Oterkus, Erkan, and Sangchan Jo. "Thermal and Structural Behaviour of Offshore Structures with Passive Fire Protection." Sustainable Marine Structures 4, no. 1 (January 20, 2022): 16. http://dx.doi.org/10.36956/sms.v4i1.476.

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In offshore structures, hydrocarbon fires cause the structure to loose its rigidity rapidly and this leads to structural integrity and stability problems. The Passive Fire Protection (PFP) system slows the transfer rate of fire heat and helps to prevent the collapse of structures and human losses. The vital design factors are decided in the detailed design stage. The determined design thickness must be accurately applied in the fabrication yard. However, there are many cases that the PFP is overused because of various reasons. This excessive application of the PFP is an unavoidable problem. Several studies have been conducted on the efficient application and optimal design of the PFP. However, the strength of the PFP has not been considered. In addition, research studies on the correlation between the thickness of the PFP and the structural behaviour are not widely available. Therefore, this study attempts to analyse the thermal and mechanical effects of the PFP on the structure when it is applied to the structural member. In particular, it is intended to determine the change in the behaviour of the structural member as the thickness of the PFP increases.

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27

Ingeli, Rastislav, Boris Vavrovič, and Miroslav Čekon. "Thermal Bridges Minimizing through Typical Details in Low Energy Designing." Advanced Materials Research 899 (February 2014): 62–65. http://dx.doi.org/10.4028/www.scientific.net/amr.899.62.

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Energy demand reduction in buildings is an important measure to achieve climate change mitigation. It is essential to minimize heat losses in designing phase in accordance of building energy efficiency. For building energy efficiency in a mild climate zone, a large part of the heating demand is caused by transmission losses through the building envelope. Building envelopes with high thermal resistance are typical for low-energy buildings in general. In this sense thermal bridges impact increases by using of greater thickness of thermal insulation. This paper is focused on thermal bridges minimizing through typical system details in buildings. The impact of thermal bridges was studied by comparative calculations for a case study of building with different amounts of thermal insulation. The calculated results represent a percentage distribution of heat loss through typical building components in correlation of various thicknesses of their thermal insulations.

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28

Nawalany and Sokołowski. "Building–Soil Thermal Interaction: A Case Study." Energies 12, no. 15 (July 29, 2019): 2922. http://dx.doi.org/10.3390/en12152922.

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This paper presents an analysis of thermal interaction between a building and surrounding soil. The examined building was located in southern Poland. Measurements of selected indoor and outdoor air temperature parameters were made in order to determine the boundary conditions. The soil temperature measurements were conducted at 42 points. The analysis of results is divided into four periods: summer, autumn, winter, and spring. The analysis show that weather conditions significantly affect the temperature in soil, but the range of residential building impact decreases with distance, and it varies depending on the season. The residential building impact on the soil temperature is in the range of 1.2–3.3 m. This paper also includes a study of the heat flow direction in soil and a quantitative estimate of heat exchange between a building and the soil. The greatest energy losses 2082 kWh (21.24 kWh/m2) from the building to the soil were recorded in winter. In spring, the energy losses were reduced by about 38% as compared with the energy losses in winter, and the energy losses in spring were comparable to autumn.

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Henríquez, V. Cutanda, and P. Risby Andersen. "A Three-Dimensional Acoustic Boundary Element Method Formulation with Viscous and Thermal Losses Based on Shape Function Derivatives." Journal of Theoretical and Computational Acoustics 26, no. 03 (September 2018): 1850039. http://dx.doi.org/10.1142/s2591728518500391.

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Sound waves in fluids are subject to viscous and thermal losses, which are particularly relevant in the so-called viscous and thermal boundary layers at the boundaries, with thicknesses in the micrometer range at audible frequencies. Small devices such as acoustic transducers or hearing aids must then be modeled with numerical methods that include losses. In recent years, versions of both the Finite Element Method (FEM) and the Boundary Element Method (BEM) including viscous and thermal losses have been developed. This paper deals with an improved formulation in three dimensions of the BEM with losses which avoids the calculation of tangential derivatives on the surface by finite differences used in a previous BEM implementation. Instead, the tangential derivatives are obtained from the element shape functions. The improved implementation is demonstrated using an oscillating sphere, where an analytical solution exists, and a condenser microphone as test cases.

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Ding, Xiao Feng, and Hui Chang. "Analysis of Losses and Thermal in Induction Motors." Applied Mechanics and Materials 446-447 (November 2013): 503–8. http://dx.doi.org/10.4028/www.scientific.net/amm.446-447.503.

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This paper presents an investigation into the losses and thermal characteristics of induction motors operated from pulse width-modulated (PWM) voltage supply in comparison to that operated from sinusoidal voltage supply. It was concluded that due to the abundant harmonics in the PWM waveforms, significant losses are induced in the motor by the inverter supply. The temperature ascends correspondingly. Experiments were conducted with no load and with load conditions. The losses and thermal characteristics were calculated using finite element analysis (FEA) and validated by the experiments.

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Hancock, Stephen, and Tyler Westover. "Simulation of 15% and 50% Thermal Power Dispatch to an Industrial Facility Using a Flexible Generic Full-Scope Pressurized Water Reactor Plant Simulator." Energies 15, no. 3 (February 4, 2022): 1151. http://dx.doi.org/10.3390/en15031151.

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Nuclear power plants in the United States are increasingly challenged to compete in wholesale electricity markets due to the low electricity costs and increasingly dynamic grid conditions from competing generation sources. An alternative market for nuclear power is industrial facilities that can use the thermal and/or electrical power generated by a nuclear power plant to offset the economic losses incurred by electricity market challenges. A generic pressurized water reactor (PWR) simulator was used to show the results of a basic design for a generic thermal power extraction system and tests were run using a set of procedures to show what happens when a nuclear power plant transitions from full electrical power dispatch to 15% and 50% thermal power dispatch. This type of operation leads to losses in turbine performance efficiency due to the deviation from the design operating point, but because the thermal power is also used by the industry load without conversion losses, the combined thermal efficiency of the PWR increases. For the 15% case, the thermal efficiency increased from 32% to 41.9%, while for the 50% case, the efficiency increased up to 60.1%. In addition, for 50% thermal power dispatch, the power dissipated by the condenser decreased from approximately 2000 to approximately 1300 MW (thermal), indicating a substantially diminished impact on the environment in terms of releasing heat into the cooling water reservoir.

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32

Buday, Peter, Rastislav Ingeli, and Boris Vavrovič. "Comparison of Thermal Bridges Calculate Method through Typical Details in Low Energy Designing." Advanced Materials Research 855 (December 2013): 126–29. http://dx.doi.org/10.4028/www.scientific.net/amr.855.126.

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There are several studies that have investigated transmission heat transfer losses, through building envelopes including thermal bridges. Most of the studies investigate the effect of different calculation and simulation methodologies, such as static/dynamic and 1D/2D/3D. It is essential to minimize heat losses in designing phase in accordance of building energy efficiency. Building envelopes with high thermal resistance are generally typical for low-energy buildings. In this sense thermal bridges impact increases by using of greater thickness of thermal insulation. s mentioned earlier, different measuring methods may be used to quantify building elements. This paper is focused on comparison of thermal bridges calculate method through typical systems details in buildings. The impact of thermal bridges was studied by comparative calculations for a case study of building with different amounts of thermal insulation. The calculated results represent a percentage distribution of heat loss through typical building components in correlation of various thicknesses of their thermal insulations.

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Mentzoni, M. H. "Thermal electron energy losses in air." Physics Letters A 134, no. 2 (December 1988): 125–26. http://dx.doi.org/10.1016/0375-9601(88)90947-4.

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34

Mehmood, Zahid, Ibraheem Haneef, Syed Zeeshan Ali, and Florin Udrea. "Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses." Sensors 19, no. 8 (April 18, 2019): 1860. http://dx.doi.org/10.3390/s19081860.

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Minimizing conductive heat losses in Micro-Electro-Mechanical-Systems (MEMS) thermal (hot-film) flow sensors is the key to minimize the sensors’ power consumption and maximize their sensitivity. Through a comprehensive review of literature on MEMS thermal (calorimetric, time of flight, hot-film/hot-film) flow sensors published during the last two decades, we establish that for curtailing conductive heat losses in the sensors, researchers have either used low thermal conductivity substrate materials or, as a more effective solution, created low thermal conductivity membranes under the heaters/hot-films. However, no systematic experimental study exists that investigates the effect of membrane shape, membrane size, heater/hot-film length and M e m b r a n e (size) to H e a t e r (hot-film length) Ratio (MHR) on sensors’ conductive heat losses. Therefore, in this paper we have provided experimental evidence of dependence of conductive heat losses in membrane based MEMS hot-film flow sensors on MHR by using eight MEMS hot-film flow sensors, fabricated in a 1 µm silicon-on-insulator (SOI) CMOS foundry, that are thermally isolated by square and circular membranes. Experimental results demonstrate that: (a) thermal resistance of both square and circular membrane hot-film sensors increases with increasing MHR, and (b) conduction losses in square membrane based hot-film flow sensors are lower than the sensors having circular membrane. The difference (or gain) in thermal resistance of square membrane hot-film flow sensors viz-a-viz the sensors on circular membrane, however, decreases with increasing MHR. At MHR = 2, this difference is 5.2%, which reduces to 3.0% and 2.6% at MHR = 3 and MHR = 4, respectively. The study establishes that for membrane based SOI CMOS MEMS hot-film sensors, the optimum MHR is 3.35 for square membranes and 3.30 for circular membranes, beyond which the gain in sensors’ thermal efficiency (thermal resistance) is not economical due to the associated sharp increase in the sensors’ (membrane) size, which makes sensors more expensive as well as fragile. This paper hence, provides a key guideline to MEMS researchers for designing the square and circular membranes-supported micro-machined thermal (hot-film) flow sensors that are thermally most-efficient, mechanically robust and economically viable.

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Ingeli, Rastislav, Jozef Podhorec, and Miroslav Čekon. "Thermal Bridges Impact on Energy Need for Heating in Low Energy Wooden House." Applied Mechanics and Materials 820 (January 2016): 139–45. http://dx.doi.org/10.4028/www.scientific.net/amm.820.139.

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Energy need for heating is depend on the heat loss of the builing. It is essential to minimize heat losses when designing and building energy efficient buildings. For an energy-efficient building in a cold climate, a large part of the space heating demand is caused by transmission losses through the building envelope. The low-energy buildings are enevelope construction with high thermal resistance. The impact of thermal bridges was studied by comparative calculations for a case study building with different amounts of insulation. In the low-energy buildings are envelope construction with high thermal resistance. When more insulation is used the relative impact of thermal bridges increases. In these buildings is necessary to specify each thermal bridges. This thesis deals with the influence of thermal bridges on energy need for heating in low energy wooden houses.

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Aleksakhin, Alexander, Iryna Dubynskaya, Ilona Solyanyk, and Zhanna Dombrovs’ka. "The community heating network’s thermal condition assessment." Collected scientific works of Ukrainian State University of Railway Transport, no. 197 (December 22, 2021): 136–42. http://dx.doi.org/10.18664/1994-7852.197.2021.248328.

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Heat losses at the heating network’s distribution pipelines were identified for Karkivcommunity. Heat losses’ calculation is performed in view of the underground pipelines’ installationin non-accessible ducts. The heating system water temperature is accepted in line with the heatingnetwork temperature chart and according to the design outdoor temperature value for heatingpurposes. Specific heat losses in the network section’ pipelines are accepted at the level of standardvalues for the specified network laying method. The water flow rate at the heat pipeline sections isdefined as per the design heat loads from the buildings connected to the heat supply network. Theheat pipeline segment with uniform diameter is accepted as the rated section. The soil temperatureat the heat pipeline axis laying depth is accepted as 5°C. The heat losses at the structural networkelements are considered by 1.15 coefficient. The calculations are performed in view of the heatingsystem water flow rate and temperate changes along the heat pipeline length. While analyzing thethermal condition of the return pipelines of the community heating network, the changes in the heatcontent of the heating system water flow in the main direction pipeline during mixing with the waterflow from the branches of the main direction line are taken into account. Considering the averagetemperature of the coldest five days consecutively, the total energy loss in heating pipeline for a groupof buildings in Kharkov region are equivalent to 180.8kW.In view of the ambient air temperature changing over the heating period for Kharkiv cityclimate conditions and the current schedule for quality heat energy supply to the consumers controlthe annual heat losses in the community heating network pipelines were calculated. The soil temperature change at the heat pipeline installation depth during the heating period was notconsidered.Heat losses in the microdistrict network for the year are 2184 GJ. The data obtained can beused to compare options when developing a strategy for reforming the microdistrict heat supplysystem.

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37

Stine, W. B., and A. A. Heckes. "Energy and Availability Transport Losses in a Point-Focus Solar Concentrator Field." Journal of Solar Energy Engineering 109, no. 3 (August 1, 1987): 205–9. http://dx.doi.org/10.1115/1.3268207.

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This paper presents the results of an experimental study of the losses in transporting thermal energy from a field of 114 point-focus solar collectors to a central thermal energy conversion system at the Solar Total Energy Project (STEP), Shenandoah, Georgia. Conduction and convection heat losses from the collector field piping and solar collector receivers and radiant energy losses from the solar collector receivers were measured. At normal operating conditions the steady state heat losses per unit of collector aperture area are 130 W/m2 (41 Btu/hr-ft2). The thermal mass of the collector field was found to be 3.92 kWh/°C (7,440 Btu/°F), which implies that 17 percent of the energy collected on a typical day is used to warm the field piping to its operating temperature. The loss of availability from the collectors and the field piping shows that only 21 percent of the available solar energy falling on the collector field is delivered to the power cycle for conversion into electricity.

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38

Calderon Arenas, Jose Antonio. "Axisymmetric modelling of transient thermal response in solids for application to infrared photothermal radiometry technique." Revista Mexicana de Física 65, no. 1 (December 31, 2018): 54. http://dx.doi.org/10.31349/revmexfis.65.54.

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To induce temperature changes on the sample surface by the incidence of a monochromatic modulated light beam and detect the changes produced in the thermal radiation emission is the basic principle of the infrared photothermal radiometry technique. Until now, in order to analyze the thermal response mathematical models based in an one-dimensional model were used considering a sample with a finite thickness and an infinite incidence surface, as well as, the linear approximation of the Stefan-Boltzmann Law in the calculus of the heat losses due to thermal radiation. In this work, analytical and numerical models for the 2D heat diffusion in homogenous finite solid samples, are presented. These models were obtained by solving the heat diffusion equation, under cylindrical symmetry, considering mixed boundary conditions to include radiation and convection heat losses through the surfaces of the sample, and a monochromatic Gaussian excitation beam impinging on the front of the sample. The analytical models were obtained by solving the governing equations, considering the well-known linear approximation of the Stefan-Boltzmann law in the calculus of the heat losses due to thermal radiation. To analyse the effects of the non-linearity of the heat losses by thermal radiation on the thermal transient response, in the numerical model it was taken into account the full expression of the Stefan-Boltzmann law, and the transport equation was solved numerically by means of the Finite Element Method (FEM). The analytical solution for the oscillatory thermal response reveals the close dependence of the thermal response on the ratio of thickness to the radius of the sample, represented by the form factor sf. Both, the analytical and the numerical solutions were employed to simulate the thermal response of homogenous materials, and compared with experimental results reported elsewhere by part of our same research group. Finally, the difference between the thermal response predictions, from the analytical and numerical models, were analyzed.

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39

Elstub, Laura J., Shimra J. Fine, and Karl E. Zelik. "Exoskeletons and Exosuits Could Benefit from Mode-Switching Body Interfaces That Loosen/Tighten to Improve Thermal Comfort." International Journal of Environmental Research and Public Health 18, no. 24 (December 12, 2021): 13115. http://dx.doi.org/10.3390/ijerph182413115.

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Exoskeletons and exosuits (exos) are wearable devices that physically assist movement. User comfort is critically important for societal adoption of exos. Thermal comfort (a person’s satisfaction with their thermal environment) represents a key design challenge. Exos must physically attach/interface to the body to apply forces, and these interfaces inevitably trap some heat. It is envisioned that thermal comfort could be improved by designing mode-switching exo interfaces that temporarily loosen around a body segment when assistive forces are not being applied. To inform exo design, a case series study (N = 4) based on single-subject design principles was performed. Our objective was to assess individual responses to skin temperature and thermal comfort during physical activity with a Loose leg-sleeve interface compared with a Form-Fitting one, and immediately after a Form-Fitting sleeve switched to Loose. Skin under the Loose sleeve was 2–3 °C (4–6 °F) cooler after 25 min of physical activity, and two of four participants reported the Loose sleeve improved their thermal comfort. After completion of the physical activity, the Form-Fitting sleeve was loosened, causing a 2–4 °C (3–8 °F) drop in skin temperature underneath for all participants, and two participants to report slightly improved thermal comfort. These findings confirmed that an exo that can quickly loosen its interface when assistance is not required—and re-tighten when it is— has the potential to enhance thermal comfort for some individuals and environments. More broadly, this study demonstrates that mode-switching mechanisms in exos can do more than adjust physical assistance: they can also exploit thermodynamics and facilitate thermoregulation in a way that enhances comfort for exo users.

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40

Schuchardt, Georg K. "Integration of Decentralized Thermal Storages Within District Heating (DH) Networks." Environmental and Climate Technologies 18, no. 1 (December 1, 2016): 5–16. http://dx.doi.org/10.1515/rtuect-2016-0009.

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Abstract Thermal Storages and Thermal Accumulators are an important component within District Heating (DH) systems, adding flexibility and offering additional business opportunities for these systems. Furthermore, these components have a major impact on the energy and exergy efficiency as well as the heat losses of the heat distribution system. Especially the integration of Thermal Storages within ill-conditioned parts of the overall DH system enhances the efficiency of the heat distribution. Regarding an illustrative and simplified example for a DH system, the interactions of different heat storage concepts (centralized and decentralized) and the heat losses, energy and exergy efficiencies will be examined by considering the thermal state of the heat distribution network.

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41

Tian, Haonan, Zhongbao Wei, Sriram Vaisambhayana, Madasamy Thevar, Anshuman Tripathi, and Philip Kjær. "A Coupled, Semi-Numerical Model for Thermal Analysis of Medium Frequency Transformer." Energies 12, no. 2 (January 21, 2019): 328. http://dx.doi.org/10.3390/en12020328.

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Medium-frequency (MF) transformer has gained much popularity in power conversion systems. Temperature control is a paramount concern, as the unexpected high temperature declines the safety and life expectancy of transformer. The scrutiny of losses and thermal-fluid behavior are thereby critical for the design of MF transformers. This paper proposes a coupled, semi-numerical model for electromagnetic and thermal-fluid analysis of MF oil natural air natural (ONAN) transformer. An analytical model that is based on spatial distribution of flux density and AC factor is exploited to calculate the system losses, while the thermal-hydraulic behavior is modelled numerically leveraging the computational fluid dynamics (CFD) method. A close-loop iterative framework is formulated by coupling the analytical model-based electromagnetic analysis and CFD-based thermal-fluid analysis to address the temperature dependence. Experiments are performed on two transformer prototypes with different conductor types and physical geometries for validation purpose. Results suggest that the proposed model can accurately model the AC effects, losses, and the temperature rises at different system components. The proposed model is computationally more efficient than the full numerical method but it reserves accurate thermal-hydraulic characterization, thus it is promising for engineering utilization.

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42

Buday, Peter, Rastislav Ingeli, and Miroslav Čekon. "Influence of Thermal Break Element Applied in Balcony Slab on Internal Surface Temperature." Advanced Materials Research 1057 (October 2014): 79–86. http://dx.doi.org/10.4028/www.scientific.net/amr.1057.79.

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Reduction of energy use in buildings is an important measure to achieve climate change mitigation. It is essential to minimize heat losses when designing and building energy efficient buildings. For an energy-efficient building in a cold climate, a large part of the space heating demand is caused by transmission losses through the building envelope. To achieve this, it is necessary to have processed a detailed design of buildings. Thermal bridges have to be eliminated in the design of buildings. Thermal bridges occur as point ones or linear. One of the specific details that create thermal leakage is located in balcony slabs. The balcony is one of the main reasons of the increased heat loss of buildings. The presence of thermal bridge in constructions of balcony envelopes influences the energy consumption, durability of the building envelopes, and also the thermal comfort of occupants. This paper is focused on advanced analysis of thermal performance of thermal break element applied in balcony slab with parametric correlation to the thermal properties of wall building envelope.

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Bosak, Mykola, Oleksandr Hvozdetskyi, Bohdan Pitsyshyn, and Serhii Vdovychuk. "THE RESEARCH OF CIRCULATION WATER SUPPLY SYSTEM OF POWER UNIT OF THERMAL POWER PLANT WITH HELLER COOLING TOWER." Theory and Building Practice 2020, no. 2 (November 20, 2020): 1–9. http://dx.doi.org/10.23939/jtbp2020.02.001.

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Analytical hydraulic researches of the circulating water cooling system of the power unit of a thermal power plant with Heller cooling tower have been performed. Analytical studies were performed on the basis of experimental data obtained during the start-up tests of the circulating water cooling system of the “Hrazdan-5” power unit with a capacity of 300 MW. Studies of the circulating water cooling system were carried out at an electric power of the power unit of 200 - 299 MW, with a thermal load of 320 - 396 Gcal/hr. By circulating pumps (CP), water mixed with condensate is fed to the cooling tower, from where it is returned through the turbine for spraying by nozzles in the turbine steam condenser. An attempt to increase the water supply to the condenser by increasing the size of the nozzles did not give the expected results. The amount of the water supply to the circulating pumping station depends on the pressure loss in the circulating water cooling system. The highest pressure losses are in hydro turbines (HT), which are part of the circulating pumping station. Therefore, by adjusting the load of the hydro turbine, with a decrease in water pressure losses, you can increase the water supply by circulating pumps to the condenser. Experimental data and theoretical dependences were used to calculate the changed hydraulic characteristics of the circulating water cooling system. As a result of reducing the pressure losses in the section of the hydro turbine from 1.04 to 0.15 kgf/cm2, the dictating point for the pressure of circulating pumping station will be the turbine steam condenser. The thermal power plant cooling tower is designed to service two power units. Activation of the peak cooler sectors of the cooling tower gives a reduction of the cooled water temperature by 2-4 °С only with the spraying system.

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44

Baker, Alvin F. "Solar Central Receiver Thermal Loss Test Method." Journal of Solar Energy Engineering 112, no. 1 (February 1, 1990): 2–5. http://dx.doi.org/10.1115/1.2930756.

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This paper presents a test method for determining the thermal loss from a solar central receiver at normal operating conditions. The thermal loss determined by this test method is independent of knowing the incident solar power onto the receiver. Thermal loss includes losses from emitted radiation, convection, and conduction. Reflected radiation is accounted for by an effective solar absorptance. The paper describes the test method and derives the equations used to evaluate the receiver thermal loss from the test.

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45

Maddah, Sadeghzadeh, Ahmadi, Kumar, and Shamshirband. "Modeling and Efficiency Optimization of Steam Boilers by Employing Neural Networks and Response-Surface Method (RSM)." Mathematics 7, no. 7 (July 15, 2019): 629. http://dx.doi.org/10.3390/math7070629.

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Boiler efficiency is called to some extent of total thermal energy which can be recovered from the fuel. Boiler efficiency losses are due to four major factors: Dry gas flux, the latent heat of steam in the flue gas, the combustion loss or the loss of unburned fuel, and radiation and convection losses. In this research, the thermal behavior of boilers in gas refinery facilities is studied and their efficiency and their losses are calculated. The main part of this research is comprised of analyzing the effect of various parameters on efficiency such as excess air, fuel moisture, air humidity, fuel and air temperature, the temperature of combustion gases, and thermal value of the fuel. Based on the obtained results, it is possible to analyze and make recommendations for optimizing boilers in the gas refinery complex using response-surface method (RSM).

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46

Russo, Roberto, Davide De Maio, Carmine D’Alessandro, Daniela De Luca, Antonio Caldarelli, Eliana Gaudino, Marilena Musto, and Emiliano Di Gennaro. "Enhancing the solar-to-thermal energy conversion in high vacuum flat plate solar collectors." EPJ Web of Conferences 266 (2022): 07005. http://dx.doi.org/10.1051/epjconf/202226607005.

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In solar flat plate collectors, the high vacuum insulation suppresses the convective losses increasing the collector efficiency. The solar-to-thermal energy conversion efficiency in such solar thermal collectors is mainly defined by the optical and radiation losses of the selective solar absorber. We present the full process of design, optimization, fabrication, and characterization of multilayer coatings specifically thought for working in high vacuum flat solar thermal collectors at different operating temperatures, from 100 °C to 300 °C. We discuss the relative importance of absorptance and emittance in determining the collector thermal efficiency. The robustness of the performance of the coatings related to the unpreventable errors in layer thickness during the manufacturing stage is also considered through a genetic optimisation algorithm.

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47

Simer, Abhishek, Akanksha Maurya, and Anoop Kumar. "Thermal Performance Improvement of Modified Hemispherical Cavity Receiver with Air Curtain." IOP Conference Series: Materials Science and Engineering 1259, no. 1 (October 1, 2022): 012008. http://dx.doi.org/10.1088/1757-899x/1259/1/012008.

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Abstract Heat losses from solar cavity receivers degrade the efficiency of solar parabolic dish collector system. Specifically, increased convection losses emulate a significant contribution in decreasing the performance of the modified solar cavity receiver and hence, reducing these convection losses has become a matter of great concern. The Air curtain plays a crucial role in minimizing the convection losses. This work proposes an air curtain-based modified cavity receiver wherein a plane nozzle is placed on the face of receiver to produce air curtain effect. Air curtain will prevent hot air from escaping the modified cavity receiver and increase the stagnation zone inside it to reduce natural convection on the surfaces. Numerical analyses are performed considering different air velocities and receiver orientations to evaluate the effect of air curtains on the convection losses. The impact of plane air nozzle parameters like outlet temperature, inclination, and outlet velocity of the nozzle on convection losses are shown and these parameters’ optimal value is evaluated. Our results state that the air curtain attached to the modified solar cavity receiver significantly improves performance by reducing the convection losses.

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48

Devineni, Gireesh Kumar, Aman Ganesh, and Neerudi Bhoopal. "Power Loss Analysis in 15 Level Asymmetric Reduced Switch Inverter Using PLECS Thermal Model & SIMULINK Precise Models." Journal Européen des Systèmes Automatisés 54, no. 1 (February 28, 2021): 73–84. http://dx.doi.org/10.18280/jesa.540109.

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Power losses are the most critical metrics in power converters analysis and has a significant impact on economic and technological assessments due to its sufficient approximation. This article aims to prove that the power losses (Switching & Conduction losses) are very low in low frequency switching modulation in contrast with high switching frequency modulation. Two switching modulation techniques Phase Disposition (PD-multi carrier-based pulse width modulation at high switching frequency) and Selective Harmonic Elimination Pulse Width Modulation (SHEPWM-fundamental switching frequency) are considered for the power loss assessment in 15-level reduced switch asymmetric multi-level inverter. This work proposed a simplified model for calculation of switching losses in multilevel inverters using MATAB SIMULINK. Further, the thermal model of the proposed inverter is implemented on PLECS for analyzing the power losses. The comparative analysis of switching and conduction losses of the proposed inverter with the PLECS thermal model and MATLAB precise models are integral part of this research.

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Umnyakova, Nina, and Mikhail Gandzhuntsev. "To the determination of heat exchange conditions near the inner surface of walls with reflective thermal insulation from aluminium foil." MATEC Web of Conferences 196 (2018): 02035. http://dx.doi.org/10.1051/matecconf/201819602035.

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Materials with a low coefficient of surface radiation intensively reflect the radiant component of the heat flux and reduce heat losses through the building envelope. When designing building structures with reflective thermal insulation it is necessary to evaluate the efficiency of its application. However, at present there are no methods for calculating the value of thermal losses through external walls in the presence of reflective thermal insulation on internal surface of the wall, as well as there are no data on the values of heat transfer coefficients at the inner surface of building envelope with reflective thermal insulation. In this regard, in the climatic chambers of NIISF RAABS, complex thermal engineering studies were carried out. For this a cellular concrete wall 2,8 x1,2 m was put up into the chamber with reflective thermal insulation on the inner surface and without it. The obtained results of experimental studies, presented in the work, allowed obtaining numerical values of heat transfer coefficients at the inner surface of walls with reflective thermal insulation, and use the obtained data in further calculations.

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Basharov, M. M., and A. G. Laptev. "Determination of thermal losses for gas separators with high thermal loads." Thermal Engineering 62, no. 14 (December 2015): 1028–31. http://dx.doi.org/10.1134/s0040601515140025.

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