Decrease In Average Temperature Research Articles

Numerical study on the synergistic effects of ultrasonic transducers and nano-enhanced phase change material in CPU thermal management

This study numerically investigates the effectiveness of concurrently applying nano-enhanced phase change material (NEPCM) and an ultrasonic field for the thermal management of a pin fin heat sink. The role of the NEPCM is to absorb heat from the heat sink wall, while the ultrasonic field generated by ultrasonic transducers facilitates the accelerated melting of the NEPCM. The study investigated how varying the number of ultrasonic transducers positioned near each side wall of the square cross-section heat sink, along with adjusting the concentration of nanoparticles in the NEPCM, impacts the heat sink's performance. The total power consumption of the transducers is assumed to be constant and an increase in their number is associated with a decrease in the power consumption of each transducer. It was observed that raising the number of transducers and lowering the nanoparticle concentration both contributed to a decrease in the CPU's highest temperature. Additionally, it was found that by using the combination of ultrasonic field and NEPCM, the average temperature of CPU can be reduced by 12.33–15.91 °C to the case without the ultrasonic field. Moreover, raising the number of transducers and lowering the nanoparticle concentration both contributed to a decrease in the CPU's average temperature.

Multiple heating loads participate in the system power regulation control strategy

With the addition of a high proportion of new energy and power electronic equipment, the power system has shown characteristics such as low inertia and significant energy output fluctuation, which has brought great challenges to power/frequency regulation and control of the power system. Therefore, this article uses the inertia characteristics of heat energy on the load side and exerts reasonable start-stop control to play a positive and beneficial role in the power regulation of the power system. Firstly, the room temperature variation process was transformed into a lumped parameter equivalent model. A lumped parameter heat transfer model of a single typical load was built in Simulink, and its dynamic characteristics were analyzed by symbolic calculation. Based on this, a time-domain simulation was carried out to explore the influence of the law of system parameters and external input on the change of system state quantity. Based on time domain simulation, the behavior of the heating load is analyzed. Then, the effects of typical and multiple loads on system power regulation at different outdoor temperatures are studied. It is found that when the average outdoor temperature decreases, the sustainable time of system power upturn will increase, and the sustainable time of downturn will decrease. The power curve of multiple loads simultaneously is more stable, and the adjustment ability is stronger. The reasonable and flexible control method of load switch setting, namely the coherent characteristic load power regulation strategy, realizes the sustainable power optimization of the load to the system in the specified period.

The effects of changes in HITRAN and the water vapor continuum model on infrared radiative transfer calculations and remote sensing applications

This study examines the implications of recent updates to the High Resolution Transmission (HITRAN) database and the MT_CKD water vapor continuum model on infrared radiative transfer calculations and satellite remote sensing applications. Specifically, it assesses the impact of the latest versions of the HITRAN database (i.e. HITRAN2016 and HITRAN2020) and the MT_CKD WV continuum model (i.e. versions 3.2 and 4.1.1) on clear-sky infrared flux calculations and the simulation of satellite infrared channels, specifically those of the Geostationary Operational Environmental Satellite (GOES) Advanced Baseline Imager (ABI). The results indicate that updates to the MT_CKD model tend to reduce atmospheric opacity, while updates to the HITRAN database have the opposite effect. The most significant differences noted are attributed to updates in the MT_CKD, leading to an increase in upward flux of 0.13 Wm−2 for the TRO and a decrease in downward flux of 0.28 Wm−2 for the MLS profile. However, these impacts are not uniform across the spectrum, atmospheric height, or among different atmospheric profiles. Notably, changes in the WV continuum model have significant effects in the far-infrared region. The updates in HITRAN exhibit pronounced differences associated with changes in the spectroscopic parameters of H2O, CO2 and O3. The results of GOES’ ABI channels indicate that changes in HITRAN lead to an average brightness temperature decrease of 0.3 K for channel 12, which exceeds the channel’s sensitivity. This research underscores the importance of continuous updates and evaluations of spectroscopic databases and radiative transfer models to improve the accuracy of atmospheric remote sensing data.

Last Glacial Maximum climate and atmospheric circulation over the Australian region from climate models

Abstract. The Last Glacial Maximum (LGM; ∼21 kyr ago) was the most recent time that the Earth experienced global maximum ice volume and minimum eustatic sea level. The climate changes over the Australian region at the LGM remain uncertain, including the extent of cooling in the arid interior, changes in the regional atmospheric circulations such as the tropical monsoon and mid-latitude westerlies, and changes in the balance between precipitation and evaporation. In this study, 13 climate model simulations that were included in the Paleoclimate Modelling Intercomparison Project (PMIP) Phases 3 and 4 are used to investigate regional climate (temperature, precipitation, and wind) over Australia at the LGM. The model simulations are compared with existing proxy records and other modelling studies. All models simulate consistent annual and seasonal cooling over the Australian region (defined as 0–45° S, 110–160° E) at the LGM compared to pre-industrial, with a multi-model mean 2.9 °C decrease in annual average surface air temperature over land at the LGM compared to pre-industrial. Models simulate a range of LGM precipitation anomalies over the region. Simulated precipitation changes over tropical Australasia appear to be driven by changes in circulation and moisture transport, which vary greatly between models. Surface moisture balance calculated from precipitation minus evaporation shows little change over much of the Australian land area at the LGM. Changes in the strength and position of the mid-latitude westerlies are uncertain, with wide model disagreement. These results indicate that climate model simulations do not show a robust response in either tropical or mid-latitude circulation to LGM boundary conditions, suggesting that caution is required when interpreting model output in this region. Further analysis based on model evaluation and quantitative model–proxy comparison is required to better understand the drivers of LGM climate and atmospheric circulation changes in this region.

Heating and Evaporation of Sessile Droplets: Simple and Advanced Models.

New advanced and simple two-dimensional (2D) models of sessile droplet heating and cooling and evaporation are suggested. In contrast to the earlier developed one-dimensional (1D) model, based on the assumption that heat supplied from the supporting surface is homogeneously and instantaneously spread throughout the droplet, both new 2D models consider the spatial distribution of this heat. The advanced 2D model is based on the numerical solution to the equations of conservation of mass, momentum, vapor mass fraction, and energy with standard boundary and initial conditions, using COMSOL Multiphysics code. Simple 2D and 1D models assume that droplets retain their truncated spherical shapes during the evaporation process. In the 1D model, the analytical solution to the 1D heat conduction equation inside the droplet is implemented into a numerical code. In the simple 2D model, the 2D version of this equation is solved numerically using COMSOL Multiphysics code. Droplet deformation, temperature gradients along the droplet surface, and the Marangoni effect are not considered in this model. The predictions of all three models are validated using in-house experimental data obtained from studies of sessile droplets of distilled water with initial volumes of 5.2, 3.2, and 2.2 μL, at an ambient temperature of 298.15 K, and at atmospheric pressure. The observed values of normalized droplet radii squared are shown to be close to those predicted by all three models. This allows us to recommend the application of the simplest 1D model for predicting this parameter. The time dependences of the droplet average surface temperature predicted by the advanced 2D model are shown to be close to those observed experimentally. The simple 2D and 1D models can correctly predict the initial rapid decrease in droplet average surface temperature followed by its gradual increase, in agreement with experimental data.

Parametric Optimization and Efficiency Assessment of Horizontal Earth Water Pipe Heat Exchanger (EWPHE) in the Context of Bangladesh

This study aimed to evaluate the efficiency of the Earth Water Pipe Heat Exchanger (EWPHE) system in Bangladesh through simulation and experimental work carried out at Joypurhat in Bangladesh during the coldest period of the year, January. Additionally, the study sought to establish the method for selecting optimal installation parameters of EWPHE to increase performance and efficiency. A simulation model was made in the TRNSYS (v16.0) platform to determine the optimum values of design parameters. The simulation was run by altering its operating parameters, such as the rate of water flow, length of the pipe, built materials of the pipe, and the diameter of the underground pipeline. According to the findings, pipe burial can be done to a depth of 3.5 meters to achieve optimal output. The results of comparing four distinct materials, namely GI, Steel, PVC, and HDPE, show that these materials' characteristics do not significantly affect how well the systems perform. Additionally, as the water flow rate is increased, it is shown that the EWPHE performance is declining. According to the simulation results, it is concluded that a pipe with a length of 50 meters would be sufficient in the proposed EWPHE system to reach an average temperature decrease from 35 °C to 27 °C. Subsequently, in the field experiment, the EWPHE system had an average efficacy of 55% throughout January, which is quite promising. Journal of Engineering Science 14(2), 2023, 79-88

Investigasi Pengaruh Flow terhadap Pembacaan Suhu Air Sensor DS18B20 pada Shower Therapy

The shifting lifestyle trends towards prolonged periods of sitting have led to an increase in health issues such as stress, depression, and even hypertension. In the pursuit of maintaining health, therapy, particularly shower therapy, has become a popular choice for its perceived ability to provide warmth, relaxation, and alleviate fatigue. However, questions arise regarding whether the water temperature in shower therapy changes as water flows at specific rates and how this might influence the therapy's effectiveness. This research aims to observe whether the water temperature in shower therapy is affected by the flow rate using the DS18B20 temperature sensor. The method involves measuring the water temperature at rest and while it flows at various flow rates. Water flow is controlled using a dimmer on the booster pump, while temperature measurements are taken using the DS18B20 temperature sensor and water flow meter sensor. The test results indicate that water at temperatures of 38-43°C flowing through pipes experiences an average temperature decrease of approximately 1.53°C. However, the temperature decrease does not exhibit a linear relationship with the flow rate. These findings suggest the possibility of other factors, such as the surface area of the conduit (pipes), influencing the temperature reduction in shower therapy. Hence, further research to examine the impact of the surface area of the conduit on the temperature reduction in shower therapy is warranted to obtain a more comprehensive understanding.

CFD modeling of flow, combustion and NOx emission in a wall-fired boiler at different low-load operating conditions

In the context of achieving carbon peaking and carbon neutrality, the implementation of flexible peak shaving techniques is of significant importance to coal-fired units. Operating coal-fired units under different low loads can result in decreased combustion efficiency, unstable combustion, and increased emissions of nitrogen oxides (NOx) during the combustion of pulverized coal. However, few studies have been carried out wall-fired boiler under low-load operation in most papers. This paper employs numerical simulation to investigate the flow, temperature, composition concentration fields, as well as combustion stability and NOx emission characteristics of a 600 MWe wall-fired under various low-load (specifically, 400, 300, 240 and 200 MWe) conditions. The simulations demonstrate that reducing the boiler load leads to decreases in the amount of filling gas and the average temperature of the furnace. Despite the overall decrease in average furnace temperature with load reduction, the central part of the furnace can reach 1400 K at low load (200 MWe), due to the strong flame stability of centrally fuel-rich burner. The NOx concentrations for 400, 300, 240, and 200 MWe were 475.9, 498.4, 361.9 and 259.7 mg/Nm3, respectively. The NOx concentration initially increases with the load reduction, and decreases as the load is further reduced. Considering the broad industrial application prospect of flexible peak shaving of coal-fired boilers, these research results provide guidance and suggestions for different load operation of wall-fired boilers, and provide theoretical support for low load stable combustion operation of wall-fired boilers.

Analyzing the effect of normally distributed cooling channels on a photovoltaic thermal solar unit

Photovoltaic thermal (PVT) systems convert solar radiation into electrical and thermal energy while keeping the PV's temperature within a permissible range. This paper presents a numerical analysis of a novel normal cooling technique for the PV module and a new AI prediction model. It considers a cooling direction normal to the PV panel using rectangular cascade channels with two different orientations. This cascading of the flow inlet channels helps keep the inflow temperature as cold as possible along the PV panel. The numerical simulations are performed based on a flow rate range of 0.00024: 0.0012 LPM, insolation of 400: 1200 W/m2, convection coefficients of 5.48 and 20.7 W/m2.K, and ambient temperatures of 298 and 308 K. The proposed PVT system achieves a decrease in the cell's average temperature by 27K while improving the electrical, thermal, and overall efficiencies by 4.8%,59.5%, and 73.33%, respectively. The numerical database is used for building an ANN prediction model based on a radial base function neural network with Gorilla troops optimizer (RBFNN-GTO). The proposed RBFNN-GTO model is developed to predict the main performance parameters of the PVT which are thermal efficiency, electrical efficiency, overall efficiency, average temperature of the PV panel, and the model temperature un-uniformity. It achieves an overall correlation coefficient of 0.9997 concerning the numerical database and showed an average MSE of 5.4313E-4.

The thermal environment and thermal comfort of disaster relief tents in high-temperature composite environment

To ensure the safety and comfort of personnel inside disaster relief tents, this study investigated the distribution of the thermal environment within the tents under composite conditions of high temperature and solar radiation. Furthermore, the interior environmental comfort was evaluated. An experimental platform for tent testing was developed, utilizing a wind tunnel coupled with multiple disaster scenarios and a thermal manikin system. The experiments were conducted under various conditions, including high temperatures and radiation levels of 300 W/m2, 600 W/m2, and 900 W/m2, as well as a wind speed of 1.2 m/s. Two scenarios were considered: doors and windows open or closed. The thermal environmental parameters inside the tent were measured, and the Comfort Prediction Model for Vehicles (CPMV) was employed to assess the thermal comfort of the interior environment. The results indicated a significant temperature rise inside the tent due to the radiation environment, with the maximum top surface temperature reaching 62 °C at 600 W/m2. Notably, a clear temperature stratification was observed among the three horizontal levels inside the tent. Opening the doors and windows resulted in a reduction of temperature below the 1.8 m level. However, when the external radiation intensity exceeded 600 W/m2, the cooling effect was minimal. The temperature stratification phenomenon inside the tent disappeared in the presence of wind, leading to an average temperature decrease of approximately 10 °C. The humidity inside the tent remained lower than the outside humidity. Owing to external irradiation, the black globe temperature inside the tent consistently exceeded the air temperature. The maximum heat flux occurred on the inner side of the tent near the top when the doors and windows were closed, reaching 250 W/m2, while the central heat flux remained relatively stable. When the external radiation during summer was around 300 W/m2, living inside the tent was within an acceptable range. As the radiation exceeded 600 W/m2, the overall thermal sensation became hot, and at 900 W/m2, the interior of the tent became excessively hot and intolerable. In such circumstances, it is recommended to regulate the duration of stay or implement cooling measures to prevent heat stress.

Aircraft engine nozzle guide vane surface temperature optimization

An optimization method based on the sensitivity of global and local geometric parameters is proposed to improve the cooling efficiency of E3 engine nozzle guide vane. For 29 geometric parameters that affect the vane maximum temperature in the cooling design, the sensitivity ranking of them is firstly obtained by the DOE method. Then the most influential parameters including the diameter or location of the film cooling hole are selected as the optimization variables to decrease the maximum surface temperature of the nozzle guide vane. On this basis, to further reduce the local temperature downstream the pressure side, a new duck-paw type film cooling hole is applied. The duck-paw type film cooling hole was produced with the adjoint method through identifying the sensitivity of the geometric boundary parameters of the film cooling holes. Compared to the cylindrical holes, the duck-paw shaped film cooling hole can greatly improve the cooling efficiency under the same conditions. The duck-paw type film cooling holes are applied to the last two rows of film cooling holes located on the pressure side of nozzle guide vane. Three-dimensional conjugate flow and heat transfer analysis results show that the maximum temperature of the optimized cooling structure vane is reduced by 39K, and the average temperature decreases by nearly 20K.

Influence of using nanofluid and phase change material on the performance of a solar thermal panel to provide the required energy of an office building in a mine

This paper examines the effect of using fins installed on tubes placed under a solar panel (SOP) numerically. The SOP is employed to generate electricity and hot water in a mine. The helical fins are mounted around the tubes under the SOP. By changing the cross-section of the fins, unsteady simulations are performed. Besides, OM37 phase change material (PCM) is utilized under the SOP and the tubes are placed inside the PCM. Alumina water nanofluid (NFD) flows inside the tubes, which are analyzed in two phases. The results show that for models M1 and M2 in 1500s, the use of tubes with a DIT of 5 mm under the SOP leads to a decrease in the SOP's average temperature of 8.58 and 8.24° respectively. The use of model M2 results in a lower outlet temperature (T-O) of the NFD when the tube DIT is 3 mm. Model M1 leads to a lower NFD T-O most of the time. Using the designed solar system can provide 56% of the hot water needed in the hot seasons and 18% of the hot water needed in the cold seasons for the building placed inside the mine.

Numerical research on ammonia-coal co-firing in a 1050 MW coal-fired utility boiler under ultra-low load: Effects of ammonia ratio and air staging condition

Co-firing ammonia (NH3) with coal for thermal power generation is a promising strategy for achieving global carbon neutrality. However, the drawbacks of NH3 combustion (e.g., narrow flammability limits, low theoretical flame temperature, high NOX emissions, etc.) can negatively impact the performance of coal-fired boilers, particularly for large-scale ones operating under ultra-low loads. As such, this study was conducted to investigate the ultra-low-load combustion characteristics of a 1050 MW coal-fired boiler when employing NH3-coal co-firing technology. Three-dimensional numerical simulations of ten combustion scenarios were performed to examine the effects of the NH3 co-firing ratio (ranging from 0% to 80%, by calorie) and air staging condition (Separated Over Fire Air (SOFA) ratio ranging from 4% to 24%) on temperature, gas species distributions, and emissions. Results show that as the NH3 co-firing ratio increases to 80%, the in-furnace average gas temperature decreases by 100 ∼ 200 K. The oxidation of NH3 takes precedence over the reduction of NO with NH3, leading to a surge in NO emissions· NH3 slip can be prevented at ultra-low loads due to the rapid consumption of NH3 near coal burners. Meanwhile, CO2 emissions reduce to 20% of that observed in pure coal firing. The increased H2O content in flue gas promotes coal burnout through the water–gas reaction, while the high H2O emissions may potentially cause low-temperature corrosion. At a SOFA ratio of 16%, a relatively large high-temperature region is achieved in the furnace, indicating more stable combustion under ultra-low loads. Excessively small or large SOFA ratios can reduce combustion intensity in the primary combustion zone while contributing to lower NO emissions.

Pore-scale modeling of gravity-driven superheated vapor flooding process in porous media using the lattice Boltzmann method

In this work, a hybrid method combining interparticle-potential multiphase LBM, finite difference method and characteristic-line wetting scheme, is developed for pore-scale simulation of superheated vapor displacing liquid, driven by gravity, in a porous geometry. The influence of injected vapor superheat, surface wettability and gravity on two-phase displacement and heat transfer processes is investigated. Results show that in thermal displacement, the vapor-liquid interface is unstable and trapped liquid blobs gradually evaporate into vapor. At low vapor superheat degrees, the displacement efficiency, as compared to isothermal displacement, is significantly improved, but it reduces as the vapor superheat degree rises due to the shift of displacement patterns. At all contact angles considered, the displacement always exhibits viscous fingering, although vapor flowpaths become wider with increasing surface wettability. The final vapor saturation is insensitive to surface wettability, but reducing contact angle leads to a less even temperature distribution inside vapor and a decrease in final average vapor temperature. In addition, increasing gravity is found to reduce vapor front temperature, but it almost has no effect on final average vapor temperature because the final average vapor temperature does not only depend on specific interfacial length but also on fingering number and inlet flow rate.

A computational case study on the thermal performance of a rectangular microchannel having circular pin-fins

This paper concerns the hydraulic and thermal performances of a three-dimensional rectangular microchannel with circular pin-fins. Laminar flow with Reynolds values (Re) between 50 and 150 was investigated. A total of 20 cases were considered. Fifteen of them were carried out for circular pin-fins with 3 fin spacing-to-fin diameter ratios (l/d = 2, 4, and 6) and 5 Re values (Re = 50, 75, 100, 125, and 150) for a constant fin height-to-channel height ratio (h/H = 0.25). The others were run without the use of circular pin-fins in the computational domain. The pressure drop and velocity distribution contour plots were obtained. Average outlet temperature and average Nusselt number (Nu) were used to study microchannels’ thermal performances. The validation process was performed for the Nu and friction factor, with absolute errors of less than 2% and 7%, respectively. The increase in Re and decrease in fin spacing caused an increase in Nu and a decrease in average outlet temperature. The pressure drop increased with increasing Re and number of fins. Therefore, thermal and hydraulic performances were found to depend on them. The predicted results indicated that the maximum average outlet temperature, pressure drop, and Nu were obtained for the smallest l/d. Comparing the microchannel with l/d = 2 to the microchannel without fins for Re = 150, the average outlet temperature of the microchannel with l/d = 2 is increased by nearly 0.23%. At Re of 150, the pressure decrease in the microchannel with l/d = 2 is nearly 23% greater than in the microchannel without fins. The average Nu of the microchannel with l/d = 2 is approximately 9% greater than that of the microchannel without fins when the Re is 150.

Perbedaan Kompres Bawang Merah dan Tepid Sponge terhadap Penurunan Suhu Tubuh pada Balita Demam di Wilayah Kerja Puskesmas Kedungmundu Semarang

Fever in children is a condition that often causes anxiety, so mothers often givefebrifuge when their child has a fever. This is done by parents because feverreducing
 drugs, both those obtained with a doctor's prescription, and thosethat are sold freely in stalls, are considered to be able to make a child's healthcondition better in a relatively short time. Objective: To prove the differencethe effectiveness of giving shallot compresses and tepid sponges on decreasingbody temperature in toddlers who have fever in the Kedungmundu HealthCenter Semarang Work area. Research Method: using a Quantitative a quasiexperimentalmethod using a Quasi Experiment research design with a pretes and post-test two group design.The sample is 34 people with Purposive Sampling technique. Test the normality of the data with the Shapiro wilk test, parametric test Paired sample t test Wilcoxon non-parametric test. Result: The results showed that in the tepid sponge group the average temperature decrease of 0.976oC (S.D ± 0.3270) whereas in the onion compress group red the average temperature decrease was 1.106oC (S.D ± 0.3699). The difference in the average decrease the temperature between the two groups was 0.1294oC (95% CI -0.3733 – 0.1145). T test results no in pairs obtained a significance value of 0.288 (ρ > 0.05) and Conclusion is that there is no difference in the effectiveness of lowering body temperature in toddlers with fever after giving the shallot intervention and in the group with the tepid sponge intervention. There was no significant difference in mean temperature difference between the tepid sponge group and the shallot compress group, but the red onion compress reached normal temperature faster than the tepid sponge

Study on the Influence of Air Inlet and Outlet on the Heat Dissipation Performance of Lithium Battery

The heat dissipation characteristics of the lithium-ion battery pack will have an effect on the overall performance of electric vehicles. To investigate the effects of the structural cooling system parameters on the heat dissipation properties, the electrochemical thermal coupling model of the lithium-ion power battery has been established, and the discharge experiment of the single battery has been designed. The voltage and temperature curves with time are similar to those obtained from the numerical model at various discharge rates, and the experimental results are relatively accurate. Based on this model, the height, angle, and number of different air inlets and outlets are designed, and the heat dissipation characteristics of different structural parameters are analyzed. The results show that the maximum temperature decreases by 3.9 K when the angle increases from 0° to 6°, the average temperature decreases by 2 K and the maximum temperature difference decreases by 2.9 K when the height increases from 12 mm to 16 mm, and the more the number of air inlets and outlets there are, the better the heat dissipation effect is. Therefore, the air vent of the battery cooling system has an important impact on the heat dissipation characteristics of the battery, which should be fully considered in the design.

Thermal performance analysis of a large scale water pit heat storage

Solar thermal application is an effective approach to achieve carbon neutrality. The large scale water pit heat storage (PTES) is a key component to ensure the stability of large-scale solar thermal plants. Based on the model of type 1535-1301, this paper performs a 2D simulation investigation of the long-term thermal performance of PTES using Trnsys. The accuracy of this model was verified by comparison with measured data from the solar plant in Dronninglund, Denmark. The results show that the average error between the model and the actual measurements is only 3%. In addition, it can be found that the PTES average temperature decreases from 24°C to 12°C before the 80th day due to heat losses. During the charging period from the 80th to 250th days, the PTES average temperature increases to 68°C. In which the PTES formed a temperature stratification with 80°C at the top and 40°C at the bottom. The sloping soil temperature boundary expands and shows a non-uniform stratification of 70-10°C with 10m thickness. The average temperature of the PTES gradually decreases to 16°C during the discharge period after the 250th day. The actual charging and discharging energy are 11,868 MWh and 11,250 MWh per year, respectively, and the total heat loss is 1,157 MWh. The storage efficiency is as high as 90.1% because PTES is used for both long-term and short-term energy storage. This paper reveals the dynamic thermal process of PTES throughout the year to provide a reference for designers.

Heat transfer enhancement by inserting a radiation enhancement plate in turbine blade internal cooling channel

A novel method of inserting a radiation enhancement plate in a turbine blade internal cooling channel is established in this paper. It can extend cold surfaces for radiation and thus enhance total heat transfer. Numerical investigations are carried out to explore the flow and coupled convection and surface radiation in the rotating channel for different channel models. The results indicate that the model inserting the radiation enhancement plate roughed with W-shaped ribs (model D) exhibits the highest cooling performance. Compared with the existing channel model (model A), the total Nusselt number ratio and the performance evaluation criterion increase by 90.53% and 21.67%, respectively, and the maximum and average temperature decrease by 339.80 K and 73.07 K, respectively. In addition, the heat transfer difference between the leading and trailing walls caused by the Coriolis force is remarkably reduced. Influences of pertinent parameters including the Reynolds number, the rotation number, the wall heat flux, and the wall emissivity are also investigated. It is demonstrated that the method has an excellent self-enhancement effect.

Characteristic analysis and optimization of special-shaped micro-textured multi-oil wedge sliding bearing

In order to deeply explore the potentials of micro-texture on enhancing the performances of a multi-oil wedge sliding bearing, a three-oil-wedge radial sliding bearing is taken as the prototype to simulate its bearing pressure, friction coefficient and temperature with the CFD method. According to the prototype bearing, the elliptic opening offset parabola micro texture(EOOPT) is designed. The response surface method is used to analyze the influence of EOOPT parameters on characteristics of the three-oil-wedge radial sliding bearing, and its corresponding quadratic regression equations are established. The multi-objective optimization of EOOPT parameters is carried out to obtain the optimal EOOPT parameters. The simulation results show that the sequence of influences of EOOPT parameters on the average bearing pressure and friction coefficient of the radial sliding bearing is as follows: short half axis, semi-major axis, depth, offset, texture evenly distributed angle. The sequence of influence on average temperature is depth, semi-major axis, texture evenly distributed angle, offset, short half axis. Compared with the prototype bearing, the average bearing pressure of the optimal-parameter micro-texture bearing increases by 13.7%, while the friction coefficient and average temperature decrease by 13.8% and 8.3% respectively.