Analysis Of Thermal Characteristics Research Articles

Analysis of Thermal Characteristics of MEMS Sensors for Measuring the Rolling Period of Maritime Autonomous Surface Ships

Recently, with the emergence of maritime autonomous surface ships (MASS), ensuring seaworthiness has increased with the operation of MASS. Ship stability is important for safety, and technical methods for controlling a ship’s motion are required to evaluate the stability. A ship’s rolling period is estimated using microelectromechanical systems (MEMS) sensors to measure the ship’s metacentric height. However, weather changes (e.g., temperature) are drastic due to various marine environments in the sea. Hence, it is necessary to analyze MEMS sensors’ thermal characteristics for applying them to MASS. This study aims to analyze the thermal characteristics of a siX-axis MEMS sensor for its application in MASS. The experiments analyzed measurement errors and noise at six steps in the range of 25–75 °C in which the MEMS sensor can be operated. The experimental results showed that the gyroscope’s thermal error and MEMS sensor’s noise level were much larger than those of the accelerometer and the respective thermal error values along the Z-axis of the accelerometer and gyroscope were the most stable compared to those along the other axes. The findings can be applied to a measurement method of the stability of MASS employing MEMS sensors in navigation equipment.

A comparative study on harmonic analysis and thermal performance of different types of lamps for residential building

This paper investigates the analysis and study of power quality, harmonics and thermal characteristics of halogen lamps, compact fluorescent lamps (CFLs) and light emitting diode lamps (LEDs). As nonlinear loads, CFLs and LEDs produce highly distorted currents compared to halogen lamps. The harmonic absorptions of each individual tested lamp are analyzed. Then, measurements with different groups of LEDs are conducted to investigate the effects of diversity factors. Although LEDs produce considerable amount of harmonics, it is concluded that amount of harmonics can be reduced by combining various types of LEDs. In addition, it could be observed that as the number of lamps increases, the diversity factor decreases. Finally, the thermal characteristics of lamps are compared in this paper. Results show that LEDs produce less heat compared to halogen lamps and CFLs.

Surface Heat Flow, Deep Formation Temperature, and Lithospheric Thickness of the Different Tectonic Units in Tarim Basin, Western China

Abstract Herein, the new collected well-testing temperature as well as continuous steady-state temperature logs were achieved for the analysis of deep thermal structural characteristics and current thermal states of various tectonic units in Tarim Basin. Generally, geothermal gradient fluctuates in 14.6-31.1°C/km, the heat flow ranges between 31.6 and 59.2 mW/m2 with the average heat flow of 43.2 mW/m2, and these values are typical of low heat flow background in Precambrian craton basins. Furthermore, estimated formation temperature spatial distributions at 6~8 km depth are the same and are mainly under the control of basement structural pattern. At 6000 m depth, temperature is 99-188°C, which become 126-242°C and 113-215°C at 7000 m and 8000 m depths, respectively. These findings confirmed that heat flow in Tarim Basin was relatively low with similar geothermal regimes to other Precambrian craton basins around the globe. In addition, 1D theoretical crustal thermal structures in Tarim Basin were established based on the solution of the equation of steady-state heat conduction. The findings revealed that “thermal” lithosphere maximum thickness in Tarim Basin is witnessed in Manjiaer sag. Tazhong uplift thermal state differs from those of Tabei uplift and Manjiaer sag. Tazhong mantle heat flow is 23.9 mW/m2, which accounts for 48.8% of surface heat flow. Hotter thermal states of Tazhong uplift generated temperatures as high as ∼690°C in Moho. Tarim Basin heat flow distribution reveals that crustal heat flow plays a more significant role in surface heat flow and possesses typical “hot crust and cold mantle” model thermal structure properties.

Analysis of Thermal Characteristics and Electrical Signal Using a Damaged Multi-outlet

Recently, the use of multi-outlets has been increasing owing to the increased use of electrical appliances in households. The majority of users do not replace multi-outlets for several months or even years after purchase. Moreover, with the intention to save energy and prevent fire, users frequently unplug electrical appliances from multi-outlets, which may cause structural defects. Owing to a poor connection between the multi-outlet and plug, there is a risk of generating local heat, which may lead to fire. Therefore, in this study, a damaged multi-outlet with structural defects owing to long-term use is secured through repeated tests, and the risk of fire is determined based on its thermal characteristics and electrical current generated during use. It was confirmed that the temperature of the main switch was higher than that of the plug connection, and the damaged multi-outlet temperature was up to 2.4-fold higher than normal.

Thermal Characteristic Analysis of Sodium in Diluted Oxygen via Thermogravimetric Approach

As the main reactor type of the fourth-generation nuclear power systems, sodium-cooled fast reactors are now designed and built worldwide. A sodium pool cooling circulation process is indispensable in a sodium-cooled fast reactor. However, the sodium pool fire design is the basis of accidents in sodium-cooled fast reactors. The fire hazard caused by the sodium–oxygen reaction and fast reactor safety have attracted extensive attention. Dry powder is widely used as an effective fire-extinguishing agent to control sodium fire. The sodium will burn in an oxygen-depleted atmosphere when using dry powder to cover fire. In this study, the change law of thermogravimetry of melted sodium is studied by thermogravimetric analysis (TGA) and the apparent activation energy (Ea) is obtained, which has a linear relationship with the oxygen concentration. The results can provide a reference for improving the engineering design standards of sodium fire suppression systems and can also be incorporated into simulation software to improve the accuracy of fire suppression simulations.

ANA LYSIS OF THE FLOW AND THERMAL FIELDS IN BOBTAIL ROOFS HEATED FROM THE BASE WALL

Analysis of airflow and thermal characteristics of attics of bobtail-shaped pitched roofs heated through a horizontally suspended ceiling is numerically carried out in this study. Pitch angles of 14o, 18o, 30o, and 45o within the standard pitch roof range are selected. The configuration falls within Rayleigh number 3.19 x 105  Ra  2.04 x 107. A finite-volume CFD code was used to solve the mass, momentum, and energy conservation equations governing the problem. The results obtained indicate a strong influence on the shape and angle of the roof. At lower roof pitches, the flow field is characterized by multiple counter-rotating vortices asymmetrically arranged within the enclosures. Eight cells in the 14o enclosure were reduced to five in the 45o roof pitch. The size and rotating strength of a vortex increase from the left corner to the middle of the enclosures. At higher pitch angles, the vertical wall obstructed the flow leading to a number of distorted cells. The maximum velocity within the aerodynamic boundary layer along the base wall occurs at Y=0.02 with the values U=0.013 and U=0.028 in the 14o and 45o enclosures respectively. The thermal field portrays a convection system of rising hot plumes from the base wall and descending cold jets from the inclined walls; all enclosed by thin boundary layers along the walls. Graphical plots of velocity and temperature variations along some cross-sections within the enclosures enable the prediction of some important heat and flow parameters.

Experimental investigation of different-shaped microwave-heated potatoes: thermal and quality characteristics analysis for food preservation.

Food materials are consumed for nutritional purposes in the form of fruits, vegetables, plants, and meat. These contain proteins, carbohydrates, and other useful nutritional compounds and these processed foods are a rich source of nutrition. The demand and supply of hygienic food for a particular population is possible only by food preservation. It can be done by various methods such as drying, freezing, chilling, chemical preservation, and pasteurization. Drying is a method of food preservation and it can be done by solar drying, microwave heating, vacuum drying, and some other methods. Microwave heating is a fast-drying method. It utilizes electrical energy to generate heat energy. The domestic microwave oven is not harmful but a commercial-level oven may be little bit harmful, when operated on high frequency. Potato is used as a sample material with different shapes such as slab, cylindrical, and spherical. The microwave oven has been operated at four different microwave powers such as 100W, 300W, 600W, and 800W. Slab-shaped (30°C), cylindrical-shaped (31.5°C), and spherical-shaped (30.5°C) food materials achieved maximum temperatures of 83.9°C, 110.6°C, and 146.1°C respectively. The temperature variations and drying characteristics of the food samples have been monitored. An oven has achieved maximum drying efficiency of 25.65% with a slab-shaped sample. For the detection of the cracks and chemical compositions in the food samples, SEM with EDS analysis has been performed. Economic analysis of microwave oven has also been done and payback period has been found as 3.27years.

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet

Analysis of Flow and Thermal Characteristics in a Rectangular Chamber with a Hollow Cylinder Under a Horizontal Turbulent Buoyant Jet

Sodium Caseinate and Acetylated Mung Bean Starch for the Encapsulation of Lutein: Enhanced Solubility and Stability of Lutein.

Lutein is a kind of vital carotenoid with high safety and significant advantages in biological functions. However, poor water solubility and stability of lutein have limited its application. This study selected different weight ratios of sodium caseinate to acetylated mung bean starch (10:0, 9:1, 7:3, 5:5, 3:7, 1:9, and 0:10) to prepare lutein emulsions, and the microcapsules were produced by spray drying technology. The microstructure, physicochemical properties, and storage stability of microcapsules were investigated. The results show that the emulsion systems were typical non-Newtonian fluids. Lutein microcapsules were light yellow fine powder with smooth and relatively complete particle surface. The increase of sodium caseinate content led to the enhanced emulsion effect of the emulsion and the yield and solubility of microcapsules increased, and wettability and the average particle size became smaller. The encapsulation efficiency of lutein microcapsules ranged from 69.72% to 89.44%. The thermal characteristics analysis showed that the endothermic transition of lutein microcapsules occurred at about 125 °C. The microcapsules with sodium caseinate as single wall material had the worst stability. Thus, it provides a reference for expanding the application of lutein in food, biological, pharmaceutical, and other industries and improving the stability and water dispersion of other lipid-soluble active ingredients.

Analysis of Water-Cooled Intercooler Thermal Characteristics

With the incremental power of construction machinery diesel engines, the power performance of diesel engines and the pollutant emissions from the exhaust gas have imposed increasingly stringent requirements on the intake cooling system of diesel engines. This paper compared the j/f evaluation factors for fin unit bodies of water-cooled intercooler (including straight fins and rectangular misaligned fins) by means of CFD simulation, and found that the rectangular misaligned fins had an 8% advantage in comprehensive performance. With the rectangular staggered fin intercooler, it was found that under the same conditions, the cooling efficiency of the dual-pass water-cooled intercooler is higher than that of the single-pass water-cooled intercooler, and the uniformity factor of the temperature difference field of the dual-pass water-cooled intercooler is 1.5% higher than that of the latter. The accuracy of the overall simulation of the intercooler is verified by the field test. The dual-pass and single-pass water-cooled intercooler both can maintain heat balance under working conditions, and its average air inlet temperature is 10 °C lower than that of the original air-cooled intercooler, which provides support for further reducing the engine air inlet temperature. The results provide a theoretical basis for the performance improvement of water-cooled intercoolers.

Research on the Thermal Characteristics of an 18650 Lithium-Ion Battery Based on an Electrochemical–Thermal Flow Coupling Model

Aiming at the complex experimental conditions of multi-physical field coupling in the analysis of thermal characteristics of lithium-ion batteries, a three-dimensional electrochemical-thermal flow coupling model for lithium-ion batteries was established using COMSOL Multiphysics software. Through the analysis of simulation results, the thermal characteristics of lithium-ion batteries for electric vehicles were explored from the aspects of heat generation and dissipation. It was found that increasing the charge–discharge rate and the electrode thickness will increase the temperature rise rate of lithium-ion batteries, and the temperature rise rate of lithium-ion batteries is the highest during their first time charging and discharging. Increasing the airflow velocity and reducing the size of the inlet flow area can improve the cooling effect on the cell. Under a single inlet, the cooling effect of the airflow field entering from the negative electrode is better than that from the positive electrode.

A state-of-the-art review on the application of heat pipe system in data centers

• The necessity and uniqueness of heat pipe system for data centers are discussed. • The heat transfer mechanism and impact factors analysis of heat pipe system is discussed. • The energy efficiency and environmental analyses of heat pipe system are summarized. • The challenges, opportunities and the future of the technology were discussed. There has been a continuous increase in the number and size of data centers because of the rapid development in the demand for data storage, networking, and computation. Electricity consumption for a conventional mechanical cooling system employed at a data center compromises approximately 30%–50% of the total energy consumption. A heat pipe system that has the advantages of high thermal efficiency, reliability, and cost effectiveness is considered promising for data center applications to reduce the energy consumption of cooling systems. This study provides a systematic review of existing heat pipe systems applied in data centers. To this end, we limit our review and discussion to the most important and related aspects, which include heat pipe system types, thermal characteristics analysis, and energy efficiency comparison. The heat transfer mechanism of the heat pipe system is described from the perspective of the evaporator and condenser. Further, the effects of the working fluid type, working fluid filling ratio, geometrical parameters, and operational parameters on the thermal performance of the heat pipe system are discussed. The energy efficiency and environmental analysis of an independent heat pipe system and an integrated system with a heat pipe were investigated. The challenges, opportunities, and future of the technology are discussed. This review is expected to contribute significantly to achieve green, sustainable, and energy-saving data centers.

(Invited) Measurement of Thermophysical Properties of Liquid Analytes Using Microfluidic Resonators via Photothermal Modulation

Temperature, being one of the fundamental parameters in the physical characterization of a material, temperature sensors with high spatial, temporal, and thermal resolution are on great demand in the field of fundamental research, protein blotting, DNA melting, drug development, biochemistry, biomedical devices, and analytical systems. Sensitive real time measurements unveil the dynamics of the analytes in a lab-on-a-chip platform where miniaturized volumes of samples are characterized when they are either rare or volume-limited. Mechanical resonators with microscale fluidic channel integrated are widely adopted as micro/nanoscale sensing platform where the resonance frequency shift of the resonators can detect minute fluctuation of physical, chemical, and biological stimulus within medium of fluidic channel at the picogram level. Even though microfluidic channels are successfully implemented for measuring thermal properties, integration with complicated QCL and static response of resonators based on static deflection delivered the results that are prone to be affected by mechanical drift and higher noise level of the photodetector. Hence the need of a simpler experimental model and dynamic response is urged. This paper reports analysis of thermal characteristics of liquid analytes using photothermal heating effect of high-speed microfluidic cantilever. While a channel-integrated resonator is modulated by a diode laser, real-time tracking of resonance frequency shift of the microfluidic resonator allows estimation of thermo-physical properties of liquid samples where the local laser irradiation results in photothermal heating of the resonator. The heating results expansion of the liquid inside the channel induces thermal stress on the walls of the channel. This thermal stress contributes to rise of the resonance frequency of the microfluidic resonator and, therefore, the frequency shift is linearly dependent of the volumetric coefficient expansion of the liquid. Also, the heating time constant is inversely proportional to the thermal diffusivity of the liquid. In addition, a higher flexural mode displays more than 3 times improved sensitivity for thermal characterization of liquids via photothermal heating.

Research of Low-Power MEMS-Based Micro Hotplates Gas Sensor: A Review

In this paper, the research status of low power micro hot plate gas sensor is reviewed. This type of sensor is characterized by the combination of MEMS technology and related insulation measures. Compared with the traditional ceramic tubular sensor, the power consumption of the sensor is greatly reduced, which provides the possibility of remote sensor arrangement and long term stable operation. This paper firstly collects the current sensor-related heat conduction, heat convection and heat radiation theories, and summarizes the calculation model of heat loss in different regions of the micro hot plate gas sensor. Then, the application examples of the finite element method in the analysis of thermal characteristics of the sensor and the common preparation process of the substrate and gas sensitive layer of the micro hot plate are listed. Finally, the main test methods of the stability and gas sensitivity of the micro hot plate gas sensor are summarized.

Temperature–Humidity Coupled Analysis in Battery Pack Based on Airflow Characteristics of Waterproof Breathable Valve

Abstract Waterproof breathable valves (WBV) are applied to the battery packs in electric vehicles due to their advantages of high efficiency waterproof and air pressure balance. With the continuity of mass transfer of WBV and uncertain thermal conditions, the dynamic thermal characteristic of the moisture inside the battery pack is difficult to obtain by experiments, especially the phase change of the moisture. To analyze WBV mass transfers to the temperature–humidity characteristic in the battery pack, this study presents a temperature–humidity coupling model of the battery pack based on the mass transfer characteristic of WBV. A mass transfer model of WBV is developed with the airflow mass transfer characteristic in air pressure difference. The proposed models verified the feasibility of dynamic thermal characteristic analysis with experiments. Finally, a practical case study on a battery pack is used to analyze dynamic characteristics of the temperature–humidity during idle and working. Using the coupling model and the WBV model, temperature–humidity distribution and the location and time attributes of moisture condensation in the battery pack are effectively obtained. The inner walls of the pack casing and the battery surface near WBV are condensation areas during environmental conditions changing.

Analysis of thermal transport and entropy generation characteristics for electroosmotic flow through a hydrophobic microchannel considering viscoelectric effect

We investigate the thermo-fluidic and entropy generation characteristics for electroosmotic flow through a hydrophobic microchannel with the consideration of viscoelectric effect. A closed form expression for the velocity is obtained from the analytical solution of the momentum and continuity equations together with the Poisson-Boltzmann equation and thereafter the temperature field is computed numerically. The flow velocity, flow rate, average Nusselt number, and average total entropy generation are computed by varying the slip coefficient, viscoelectric coefficient (f), Brinkman number (Br), and thermal Peclet number(Pe). Results reveal that the viscoelectric effect decreases the flow velocity and percentage decrement in flow rate due to the viscoelectric effect is larger for the slip case and reaches up to 40.09%. The value of the average Nusselt number decreases with f at lower value of Br, and the effect is opposite at higher values of Br. Although the heat transfer enhancement is more with the interfacial slip, the augmentation decreases with f and increases with Pe. The value of average total entropy generation decreases with the increase in f, and decrement is substantial at higher values of Br.

Screw thermal characteristic analysis and error prediction considering the two-dimensional heat transfer structure

Screw thermal characteristic analysis and error prediction considering the two-dimensional heat transfer structure

Comparative analysis of thermal runaway characteristics of lithium‐ion battery under oven test and local high temperature

SummaryLithium‐ion batteries are increasingly used in the field of new energy vehicles. Thermal runaway is the biggest potential safety hazard. In order to achieve safer battery and battery design, it is necessary to fully understand thermal runaway. In this paper, the thermal abuse model of lithium‐ion battery is established, and the accuracy of the model simulation is verified through experiments. The thermal runaway characteristics of the battery under the oven test and local heating conditions are compared and analyzed. The results show that under the condition of 200°C oven test in more than 10 000 seconds to thermal runaway, the local heating under the condition of the thermal runaway in more than 500 seconds, and the oven temperature distribution more uniform on the surface of the test under the condition of the battery, the temperature distribution is almost consistent when thermal runaway. According to the characteristics of local heating mode, the small heating area cannot occur thermal runaway, and found that in the process of thermal runaway battery anode and electrolyte reaction to generate heat is the main cause of thermal runaway battery. This result can be used to guide the effective prevention of thermal runaway of lithium‐ion batteries and prevent spreading.

Hydrothermal analysis of heat transfer and thermal performance characteristics in a parabolic trough solar collector with Turbulence-Inducing elements

In present survey, a numerical study of fluid flow and heat transfer in a solar parabolic trough collector containing turbulence-inducing elements on wall of collector has been performed. Elements have helical profile throughout the pipe. The three-dimensional numerical simulations have been done by finite volume method using a commercial CFD code. The spatial discretization of mass, momentum, turbulence kinetic energy, turbulence dissipation rate and energy equations has been achieved by a second-order upwind scheme. SIMPLE algorithm has been used for velocity–pressure coupling. To calculate gradients, Green-Gauss cell-based method has been utilized. Generally, obtained numerical results are presented in two sections. In first part, examinations have been done to indicate impact of number of elements on collector efficiency. Five models including two, four, six, and eight numbers of turbulence-inducing elements have been analyzed. The results indicated that at VInlet = 0.32 m/sec, thermal efficiencies of models with two to six number of elements are greater than plain PTC by 6.6, 13.2, 20.6, and 27.6%, respectively. In second section, various types of element cross-section including rectangular, triangular, trapezoidal, and quasi-triangular has been investigated. Results depicted that maximum thermal efficiency belongs to case with rectangular cross-section at VInlet = 0.2 m/sec by 29% improvement.