Average Temperature Difference Research Articles

Visualization-assisted study of a new wickless pulsating vapor chamber

With the improvement and miniaturization of electronic devices, the issue of heat dissipation is becoming increasingly prominent. In this paper, a novel wickless pulsating vapor chamber (VC) plate with Tesla valves is designed to address this problem. With the purpose to achieves continuous internal fluid circulation for heat transfer by harnessing the pulsating force generated from pressure differentials across various regions, in conjunction with the unidirectional nature of the Tesla valve structure.The working fluid used in this vapor chamber plate was perfluorohexanone. To assess the feasibility and temperature homogeneity of the design, a visualization-assisted study was conducted. The results showed that the working fluid within the vapor chamber formed a stable unidirectional circulation during heat dissipation. This circulation is crucial for effectively transferring heat away from the heat source. Furthermore, the study found that the overall average temperature difference across the vapor chamber was minimal. The average thermal resistance of the vapor chamber ranged from 0.076 to 0.105 W/K with a heat dissipation power ranging from 60 to 100 W (equivalent to a heating heat flux of 60–100 W/cm2). These research findings suggest that the new wickless pulsating vapor chamber (VC) plate, equipped with Tesla valves, is an efficient solution for heat dissipation. Its simplicity in manufacturing and low cost are crucial advantages, potentially broadening its applicability to various scenarios.

Prediction model of goaf coal temperature based on PSO-GRU deep neural network

The accurate determination of coal temperature in hidden space such as goaf has always been a worldwide problem that needs to be solved. The research of coal temperature prediction model has important practical significance for the accurate detection of loose coal temperature. Based on the coal natural ignition experiment and coal spontaneous combustion gas characterization index as the initial data set GRU neurons are used to mine the nonlinear relationship between the index gas and temperature, and the GRU model parameters are optimized by PSO to obtain the predicted value of coal body temperature. The results show that the predicted MAE value of the PSO-GRU model is 1.37 °C, 6.51 °C, 11.40 °C, 15.90 °C, 20.20 °C lower than that of the PSO-SVM, PSO-BP, BP, RF and SVM prediction models respectively. The RMSE value decreased by 0.45 °C, 4.44 °C, 10.33 °C, 15.71 °C and 24.24 °C respectively. The judgment coefficient R2 on the test set and the training set of the PSO-GRU model is 0.99, and the generalization, prediction accuracy and robustness are all good. The experimental results show that the inversion temperature error of the model is within the range of 3.87 %, the maximum temperature difference is 5.69 °C, and the average temperature difference is 2.83 °C, which can meet the accuracy requirements of the field temperature measurement.

Which physiological measurements can characterize core and surface body temperature? A case study in stable thermal environment

Core and surface body temperature are physiological indicators commonly used in human-environment researches, but which specific body temperatures can characterize them have not been thoroughly explored. A case study was conducted in three stable thermal environments, where five kinds of body temperatures (intra-abdominal temperature, oral temperature, auditory canal temperature, breath temperature, and skin temperature) and two types of thermal perception (thermal sensation and thermal comfort) votes were regularly collected. Upon comparing measurements with theoretical classification principles, we found that both oral temperature and intra-abdominal temperature exhibited characteristics consistent with core temperature, while both mean skin temperature and breath temperature exhibited characteristics consistent with surface temperature. In addition, the comparison analysis between newly proposed indicators and gold standards further confirmed application prospects, as the average temperature difference between intra-abdominal and oral remained consistently below 0.1 °C, and the average temperature difference between skin and breath exhibited a slight fluctuation around fixed values. Generally, the findings of this study provide insights into the selection and application of body temperature indicators, while reminding researchers should not blindly follow the previous standards.

Laser-Induced Temperature Changes on the Outer Surface of Titanium Dental Implants: An In Vitro Study.

To measure the surface temperature distribution after using a CO2 laser to heat titanium dental implants via different power settings, application intervals, and irradiation times. A total of 10 tissue-level titanium implants (Screw-Line Promote Plus, Camlog; 4.3 × 11 mm) were placed (EpoFix, Struers) and irradiated with a CO2 laser (Denta 2, Lutronic) with a wavelength of 10.6 μm at power levels of 4 watts (Group 1), 6 watts (Group 2), 8 watts (Group 3), and 10 watts (Group 4). A continuous beam mode (setting I) and noncontinuous beam modes with 5-second (setting II) and 10-second (setting III) pause intervals were used. For each setting, a total irradiation time of 50 seconds was used and repeated 10 times. The temperature was measured using external thermocouple (Testo) in contact with the implant surface at the implant shoulder, middle, and apex. A linear regression model was used to analyze the data (P = .05). Setting I demonstrated the most rapid increase in implant surface temperature in all three test sites as well as the greatest total temperature at 50 seconds of irradiation time. The greater the pause interval (settings II and III) during the 50 seconds of irradiation, the lower the rate of temperature increase as well as the total temperature in all three test sites and with all power levels. The average temperature difference between the apex and shoulder site was significant for setting III for all groups, but not for any groups in settings I and II. Heating the internal aspect of an implant with a CO2 laser produces different temperature distribution profiles depending on the laser power level and the application interval. Laser-beam irradiation leads to a temperature gradient, which is greatest at the implant apex and smallest at the implant shoulder.

Performance enhancement of indirect solar dryer with offset strip fins: Experimental investigation and comparative analysis

In the present study, two indirect type solar dryers were designed, fabricated and experimentally investigated, one is equipped with a conventional flat plate collector, and the other is integrated with offset strip fins (OSF). The objective is to study the effect of OSF on the performance of the dryer. A series of experimental tests were conducted at the applied research unit in the semi-arid region of Ghardaia using locally available materials. The first test was starting the solar dryers with an empty chamber and the second with filled product. The peak and average temperature difference at the outlet of the collector were 11.3 and 8 °C respectively, in favor of OSF absorber. The courgette was dried to 0.69 (kg water/kg dry basis) from an initial moisture content of 26.24 (kg water/kg dry basis) in 20 h 18 min and 35 h 45 min in the solar dryer with OSF and without, respectively. The results show a high drying rate using the dryer with OSF compared the dryer with conventional collector. Also, Midilli-Kucuk model provided the best agreements between experimental and predicted moisture ratios. Average effective moisture diffusivity of 1.798x10−09 and 1.179x10−09 m2/s for the dryer with OSF and without, respectively. A 33 % increase in economic efficiency in favor the OSF dryer with 0.95 years payback period. Also, a reduced amount of GHGs makes the dryers environmental friendly.

Urban Heat Variation and Temperature Lapse Rate in the Kathmandu Valley

The rate of urbanization growth has accelerated and made urban areas comparatively warmer than surroundings which are the main issues of urban heat worldwide. The Kathmandu Valley is one of the million plus cities with the fastest rate of urbanization and consequent extreme heat. In this study, urban heat was analyzed using both in-situ and satellite-based observation and estimated temperature lapse rate. The Mann Kendell test, Sen’s slope, raster image analysis and lapse rate estimation methods were used. The results showed that average temperature difference in between urban core and surrounding was 4.07°C from 1990 to 2020. Likewise, the summer day temperature in Putalisadak was 8.8°C higher than the Nagarkot. The maximum temperature has increased in all stations where Godavari station has increased significantly (0.073°Cyr−1, p<0.0001). During all seasons, the daytime temperature is higher than the nighttime temperature. The maximum 32.86°C daytime temperature was recorded on August 4, 1pm and the minimum temperature was 3.67°C on Jan 20, 6am, 2020 at the city core. Similarly, the highest temperature was recorded at 31°C in Bagbazar and 33°C in Patan on July 10 and July 11, 2022 respectively when the humidity was lower. Satellite-based observation also shows that the urban heat scenario of the Kathmandu Valley was higher in the urban core which was ranges from 21.06 to 26.09 during 2000-2020. The temperature of the city has increased. However, temperature lapse rate in response to Nagarkot (reference station) is normal i.e decreased temperature in response to increased height. The higher lapse rate is generally found in the Godavari and lower was observed in the Machhegaoun. Overall, the Kathmandu Valley is getting more warmer compared to the surroundings. This comprehensive study is useful to explore the understanding of urban heat islands and temperature lapse rate in the major cities in compared to the surroundings in Nepal.

Effect of the urban microenvironment on the indoor air temperature of the residential building stock in the Helsinki region

Due to climate change, there is an increased risk of apartment overheating. In Nordic countries, heatwaves have not been common in the past and hence apartments are not equipped with mechanical cooling systems, so wise urban design might be a solution. This study evaluated the influence of the urban microenvironment on residential building indoor air temperature via green view index (GVI), floor area ratio and distance from the sea. We analyzed a large dataset of over 2000 apartments in the Helsinki region during summers of 2018 and 2021, where severe heatwaves were presented, and combined it with the aforementioned parameters. In the method used, closely situated buildings were clustered into groups by the microenvironment parameters. The results showed consistent correlations between clustered groups and microenvironment parameters, where the best-performing group had an indoor air temperature of about 1 °C lower than the average during the summers and 0.7 °C lower during the severe heatwaves. Building groups with higher GVI demonstrated a greater ability to endure long heatwaves, where combined influence of other urban microenvironment factors was significantly reduced. A substantial influence of sea distance and floor area ratio was observed during short heatwaves in the middle and late summer. The indoor temperature difference of the groups was compared to the average outdoor temperature difference of group areas based on the Finnish Meteorological Institute HARMONIE-AROME weather model implemented with the SURFEX module. The results revealed a consistent correlation between predicted outdoor and indoor temperatures and their distribution of group-to-area differences.

Integration of a Gamma-Type Stirling Engine with LPG Cooking Stove for Micro-Scale Combined Heat and Power Generation

The Stirling engine is one of the most versatile micro-scale prime movers for combined heat and power applications, adaptable to different levels of heat sources. This study started a unique journey that included developing, experimenting, and analyzing the Gamma-type Stirling engine. Notably, the engine design ingeniously harnesses heat from a customized cooking stove burner powered by liquefied petroleum gas. The engine fabrication resulted in a compression ratio 2.014, accommodating a volumetric capacity of 181 cc. The Stirling engine test used air as the working gas, and the initial conditions were at atmospheric pressure. Stirling engine performance was analyzed using an ideal thermodynamic cycle model and burner efficiency using the water boiling method. The modified burner attains an average temperature of 699.5°C, producing a burner power output of 5.702 kW and a thermal efficiency of 32.7% or around 1.867 kW of heat for operating the engine and cooking activities. Simultaneously, tests of the Stirling engine revealed an average air temperature difference of 146.2°C between the expansion and compression phases. The flywheel rotation speed ranges from 158 to 369 rpm. During testing, the Stirling engine obtained an average thermal efficiency of 31.08%, accompanied by an ideal power spectrum ranging from 0.3 W to 42.6 W. The highlight of this study was the maximum pressure achieved at the end of the heat absorption stage, recorded at 296.1 kPa. Importantly, these findings underscore the promising potential of micro-Combined Heat and Power systems. Integrating the gamma-type Stirling engine with the LPG stove represents novelty and paves the way for further development and advancement in sustainable energy solutions.

Predicting Ecologically Suitable Areas of Cotton Cultivation Using the MaxEnt Model in Xinjiang, China

Cultivating cotton and sustaining its productivity are challenging in temperate arid regions around the globe. Exploring suitable cotton cultivation areas to improve productivity in such climatic regions is essential. Thus, this study explores the ecologically suitable areas for cotton cultivation using the MaxEnt model, having 375 distribution points of long-staple cotton and various factors, including 19 climatic factors, 2 terrain factors, and 6 soil factors in Xinjiang. The area under the curve (AUC) of the predicted results was greater than 0.9, indicating that the model’s predictions had fairly high accuracy. However, the main environmental factors that affected the cotton’s growth were the lowest temperature in the coldest month, the hottest month, the precipitation in the driest season, and the monthly average temperature difference. Further, the temperature factors contributed 71%, while the contribution ratio of terrain and soil factors was only 22%. The research indicated that the current planting area was consistent with the predicted area in many areas of the study. Still, some areas, such as the Turpan region northwest of Bayingolin Mongol Autonomous Prefecture, are supposed to be suitable for planting cotton, but it is not planted. The current potential distribution area of long-staple cotton is mainly located in Aksu Prefecture and the northern part of the Kashgar Prefecture region. The climatic prediction shows that the growing area of long-staple cotton may expand to southern Altay, central Aksu, and Bortala Mongol Autonomous Prefecture. This study will be helpful for cotton cultivation suitability areas in Xinjiang and other regions with similar environments.

Infrared thermography in the diagnosis of Achilles tendinitis. A randomized double-blind pilot clinical trial

Background: The Achilles tendon (AT) is the widest and most resistant of the osteoarticular system and has the greatest load-bearing capacity. It is involved in daily functioning and sports activities performance. Exposure to excessive stress on the calcaneus tendon (CT) can prevent an effective repair process and favor permanent injuries. Tendinopathy is a clinical syndrome resulting from disorientation of AT fibers, and inflammatory signs characteristic of tendinitis or tissue degeneration present in tendinosis can be found. The condition can manifest itself through functional changes accompanied by clinical signs such as crackling, tenderness, pain and edema. Infrared thermography is used to trace thermographic profiles, capable of detecting thermal changes related to pathologies. Objectives: The main goal of this study was to correlate AT region thermograms with clinical and functional characteristics in healthy individuals with CT pathology. Methods: The present work consists of a double-blind pilot randomized trial, of qualitative and quantitative nature. Individuals with TC tendinopathy, classified in the Tendinopathy Group (TG) and individuals without tendinopathy, classified in the Control Group (CG) participated. Assessments were performed to characterize the subjects belonging to the TG and CG: anamnesis, infrared thermography, referred pain, crepitation and thickness on palpation, algometry, arch sign test and Royal London Hospital test, pain on passive dorsiflexion, pain on lifting the heel and long jump. Results: The results obtained in infrared thermography were consistent with those obtained in the clinical evaluation for TG and GC. The results demonstrate that healthy tendons presented an average temperature difference of 0.24 ± 0.15 ºC between legs with a maximal difference of 0.4 ºC. On the other hand, unilateral tendinopathy presented an average temperature difference of 1.2 ± 0.9 ºC, however, this difference could be as big as 5.1 ºC. Conclusion: It is concluded that infrared thermography can be used safely and non-invasively to aid in the diagnosis of Achilles tendon tendinopathy.

Thermoelectric transport properties of Si, SiGe, and silicide CMOS-compatible thin films.

Characterization of thermoelectric transport properties for temperature sensing, cooling, and energy harvesting applications is necessary for a reliable device performance in progressively minimized computer chips. In this contribution, we present a fully automated thermovoltage and sheet resistance measurement setup, which is calibrated and tested for the production of silicon- and silicon-germanium-doped as well as silicide complementary metal-oxide-semiconductor-compatible thin films. A LabVIEW-programmed software application automatically controls the measurement and recording of thermovoltages at individually defined temperature set points. The setup maps average temperature and temperature differences simultaneously in the regime from 40 to 70 °C. The Seebeck coefficient calculated by means of the inversion method was used to eliminate the offset voltage influence. Finally, we present and discuss the Seebeck coefficient as well as the sheet resistance for application-specific different temperature set points of several doped poly-Si, poly-SiGe, and silicides.

Suppression of thermal coupling noise in the SERF atomic co-magnetometer

Heating the alkali metal vapor cell to obtain high atomic density is a prerequisite for realizing the high-precision measurement for spin-exchange relaxation-free (SERF) co-magnetometer. However, the thermo-magnetic and thermo-optical coupling noise caused by the temperature diffusion from the alkali vapor cell is one of the main factors restricting the co-magnetometer performance at present. Here the influence of heating on the SERF co-magnetometer was comprehensively studied, and the thermal error model of the system was established. A novel heat insulation structure for the co-magnetometer was designed, and the effectiveness was verified through monitoring of characteristic temperature points. Compared to the conventional oven support, the average maximum temperature difference within 12 h of the optical path and magnetic shielding systems (OPMSS) decreased by 52%, the bias instability of the co-magnetometer decreased by 24%, and the noise of the co-magnetometer at 1 Hz decreased by 33%. The experimental results demonstrate that this method reduces the temperature fluctuation of the OPMSS, effectively suppresses the thermal coupling noise, and thus improves the performance of the SERF co-magnetometer. Moreover, this method is also applicable to other quantum sensors based on alkali metal vapor cell.

Test on fouling detection of ballast based on infrared thermography

To facilitate rapid, accurate, and convenient detection of ballast fouling, this paper proposes simplified computational models based on thermodynamic principles to analyze the surface temperature of clean and fouled ballast. The feasibility of employing infrared thermography for fouling detection on ballast is validated through analysis. Outdoor experiments are conducted to investigate the impact of various factors, such as the degree of fouling, the type of fouling, the intensity of solar radiation, and rainfall, on the surface temperature of the ballast. The research findings reveal that water exacerbates the difference in heat transfer rates between clean and fouled ballast. The fouled ballast has a higher thermal capacity compared to the clean ballast. In general, a lower fouling level and a higher solar radiation intensity result in a higher average surface temperature of the ballast when the external environment is stable and there is no shading. The intensity of solar radiation directly affects the temperature of the ballast surface. Additionally, the level of fouling primarily affects the temperature difference on the ballast surface for different degrees of fouling. When the percentage difference in average surface temperature between clean and fouled ballast exceeds 3.9% in this experiment, it is advisable to promptly assess the operational condition of the ballast and perform maintenance if necessary. On the sunny day, the temperature differences between the clean ballast and those with fouling levels of 20% and 40% are 1.22 °C and 2.01 °C, respectively. However, on the cloudy day, the maximum difference is only 0.3 °C. The temperature differences increase from 1.51 °C and 2.42 °C to 2.29 °C and 4.72 °C before and after rainfall, respectively. During nighttime, the average surface temperature of the ballast does not differ significantly between different levels of fouling. It is recommended to use infrared thermography for fouling detection on ballast during sunny afternoons or after rainfall. But further research is needed to explore its application during nighttime.

An air-cooled system with a control strategy for efficient battery thermal management

Air-cooled systems are widely used in electric vehicles for the thermal management of battery packs. Due to the low specific heat capacity of air, design of air-cooled systems is required to improve the temperature uniformity of battery packs. However, structural design of the system cannot meet the requirement of battery thermal management under varying operating conditions. In this study, a parallel air-cooled system with a control strategy is developed for efficient cooling of battery packs under varying operating conditions. The performance of the air-cooled systems with different single flow types is investigated numerically, with the results verified by experiments. A control strategy based on the temperature difference among battery cells is proposed for the system with J-type flow, and the mechanism by which traditional systems fail in temperature difference control is revealed. To address this issue, an efficient thermal management system that integrates different flow types is proposed and relevant control strategy is developed, with decreased widths of the parallel channels on both ends. The proposed system with the control strategy reduces the temperature difference among battery cells by switching the flow type on demand and guiding more cooling air to the battery cell with high temperature. The numerical results of the cases with high current discharge rate and with varying random operating conditions show that the developed system enables the temperature difference to be controlled below 0.5 K after several switches of flow type. The average temperature difference among the battery cells in the developed system is reduced by more than 67% compared to that with J-type flow alone. The proposed system with the relevant control strategy is efficient for thermal management of battery packs under varying operating conditions.

Effect of thermal management system parameters on the temperature characteristics of the battery module

In the present inquiry, a novel electric-thermal coupled model is devised to delve into the battery module's temperature distribution characteristics at different ambient temperatures and discharge rates. The accuracy of temperature prediction accuracy is contingent upon the experimental determination of the entropy heat coefficient and convective heat transfer coefficient. In the absence of a thermal management system for the battery module, an escalation in the discharge rate correlates with an increase in the average temperature, average temperature rise, and maximum temperature difference, while a decline in the initial ambient temperature relates to a decrease in these values. Under typical vehicle driving cycle conditions, the average temperature curves show peaks before the end of the cycle. The wider speed range, longer testing time, and reduced regularity of the driving cycles cause both the average temperature and maximum temperature difference to increase. Further research is done into the effects of coolant flow rate and temperature, and contact thermal resistance on the efficiency of thermal management systems. Gradual decrease in the average temperature transpires as the coolant flow rate increases, but excessively high flow rates engender a larger maximum temperature difference. As the coolant temperature decreases, both the average and maximum temperature difference decrease, but temperature uniformity is worsened. The average and maximum temperature difference generally rise when the thermal contact resistance increases, and a low thermal contact resistance leads to a more uniform low-temperature distribution.

Integration of Sentinel–1 and Landsat–8 data for identifying deformation risk of hydraulic engineering in seasonally frozen salinization regions

Hydraulic engineering has positive effects on agricultural production and soil desalination. However, freeze–thaw cycles can cause instability in canal slopes, emphasizing the need for effective deformation monitoring. Using Sentinel-1B data acquired from November 2017 to August 2019 and applying the small baseline subset (SBAS) InSAR method, two unstable canal segments with vertical deformation rates exceeding –40 mm/year were identified in Songyuan, Northeast China. The canal slopes uplifted in winter and experienced accelerated subsidence in spring, with the shady slope experiencing a deformation rate approximately 10 mm/year faster than the sunny slope. Further investigation, integrating Landsat–8 data collected from November 2017 to August 2019, revealed that the shady slope received less thermal radiation than the sunny slope, with an average annual temperature difference on the land surface of approximately 1 ℃. In winter, the saline–alkali soil particles formed a thick unfrozen water film, which, driven by temperature and soil–water gradients, migrated towards the freezing front, froze, and caused soil frost heave. The shady slope experienced longer freezing periods and deeper frozen depths, up to 240 cm, causing more unfrozen water migration and greater uplift deformation than the sunny slope. In spring, as temperature rose, the soil thawed from the surface downward. Notably, the shady slope thawed at a slower rate than the sunny slope, forming a frozen lens near a depth of 100 cm. Frozen lens acted as a barrier for meltwater infiltration, impeding the dissipation of pore water pressure, making the shady slope prone to surface landslides. The integration of multiple data sources is beneficial for identifying deformation risk in hydraulic engineering.

Low-emissivity interior wall strategy for suppressing overcooling in radiatively cooled buildings in cold environments

Buildings with radiative cooling can significantly reduce energy consumption for cooling, but the overcooling phenomenon also occurs in cold seasons, which causes negative effects in buildings. Herein, a strategy of using low-emissivity interior surfaces to reduce the heat loss from humans to cold walls is proposed to suppress the negative overcooling effect of radiative cooling. Comparative experiments are conducted based on two small-scale boxes with internal heat sources and low/high emissivity interior surfaces. Results show that the heater temperature in the box with the low-emissivity interior surface is higher than that with the high-emissivity surface, with maximum and average temperature differences of 2.3 °C and 1.8 °C, which indicates that the radiative heat insulation effect is achieved for humans by the low-emissivity interior surface. Moreover, large-scale building modeling is performed, which not only confirms the existence of the overcooling phenomenon but also shows over 30% of heat loss can be avoided for internal heat sources by applying low-emissivity interior surfaces under overcooling conditions. Importantly, we found that interior surfaces with low emissivity under cold seasons and high emissivity under hot seasons can fully explore the potential of passive radiative cooling for buildings, which can guide the next-generation material design for energy-saving buildings.

Optimizing the air flow pattern to improve the performance of the air-cooling lithium-ion battery pack

The change in the structure of the air-cooling battery thermal management system (BTMS) is demonstrated to improve its cooling performance. In previous research carried out by the authors investigating a 4 × 9 21,700 battery module, several exit areas close to the entrance area were designed and examined. The direction of the entrance area is perpendicular to the cooling channel, while the direction of the exit area is parallel to the cooling channel. A simulation analysis of the BTMS is carried out to optimize the cooling performance. It is found that with the gradual increase in the wind speed, the outlet position is gradually shifted towards the inlet area wall. This can maintain the average temperature, maximum temperature, and maximum temperature difference of the battery module at the lowest levels. The polynomial fitting method is used to establish the mathematical relationship between the distance from the center surface to the leftmost wall of the outlet area of the BTMS, the wind speed, and the main cooling index when the discharge rate is 2C. On this basis, the best fitting function is obtained, and the model is established for verification.The two BTMS models were validated at wind speeds of 8 m/s, and the average temperature of both BTMS was very close to the predicted value, with maximum deviations of 0.57 % and 1.01 %, respectively. This fitting method could help to design a better air-cooling BTMS.

Исследование неравномерного распределения поверхностной температуры организма человека с помощью инфракрасного термометра на примере измерения температуры кисти

The front and back surface temperature of the hand was investigated with method of the medical thermography in the article. We used the infrared thermometer (UNI-T, China) and portable computer thermograph IRTIS-2000 (IRTIS, Moscow, Russia). The study was conducted on a group of subjects, consisting of 50 people, 17 men and 33 women, aged 18 to 23 years. The average temperature difference between the palm and the back of the hand was 0.21 ± 0.16 °С. It was also found that not all subjects had a palm temperature higher than the temperature of the back of the hand. A ten-day study was conducted separately on one patient to determine how the temperature difference of the left and right hands changed in the morning, afternoon and evening. He initially had a temperature on the back of his hand higher than his palm. Analysis of the data for the entire sample confirmed the assumption that the surface temperature of the palm is higher than the temperature of the back (р < 0.05). However, when the groups of men and women were examined separately, the difference was negligible (р > 0.05). The discussion part includes articles that studies hand temperature in obesity and vibration disease.

Numerical Simulation of Heat Transfer Characteristics of Finned Tube Heat Exchanger at Different Flow Velocities

A heat exchanger is an important component where high-temperature hot air and normal-temperature water exchange heat. The heat exchange area of the finned tube heat exchanger is calculated by the rated working conditions. However, with the decrease of the heat storage temperature, the hot air temperature at the outlet of the thermodynamic energy storage device changes in a large range, directly affecting the heat exchange capacity and efficiency of the finned tube heat exchanger. This paper’s three-dimensional model is established. The heat exchanger of the finned tube is designed according to the temperature of the outlet section and the return section temperature of the heat storage system. The thermodynamic physical parameter property and characteristics of which heat exchanger’s finned tube in the air’s velocity range of 1∼10 m/s are simulated by fluent software. The velocity, temperature, pressure, and heat exchanger coefficient distribution characteristics at different positions along the airflow direction are obtained. The simulation results show that the mean flow velocity is 2.0 m/s and 5.0 m/s at the inlet cross-section. The average temperature difference between the inlet and outlet is 69.5 K and 100.5 K, respectively. The fin surface temperature difference between the first and eighth rows of finned tubes is 12.5 K and 14.4 K, respectively. The air pressure loss at the air channel inlet’s section and outlet’s section is 16.1 Pa and 69.4 Pa, respectively. When the inlet flow rate change from starting at 1.0 m/s and ending at 10.0 m/s, the tube’s wall coefficient of heat transfer, which is the second level of finned tubes, only increases by 1.8 times. The tube’s wall coefficient of heat transfer of the eighth level of finned tubes increases by the maximum, to 5 times the original, but the heat energy exchange capacity of which the second level of finned tubes is always the strongest.