Air Temperature Distribution Research Articles

Novel method to remotely measure air temperature distribution for indoor environments with heat sources using thermal infrared spectroradiometer

Air temperature is an important physical indicator of a built space. A novel method for remotely measuring the air temperature distribution using a thermal infrared spectroradiometer is evaluated, and an experiment using the maximum a posteriori method, which uses a priori information, is conducted with a heat source. The a priori information is the probabilistic information that the observer knows about the air temperature prior to the observation. Assuming an indoor scale (10 m), the air temperature distribution is estimated (i.e., retrieved) by discretizing the space into four layers. Accordingly, our method reduces the error in the air temperature estimation compared to the a priori information. When the layer of the heat source is known, the air temperature estimation is sensitive to the air temperature of the heated layer, even when the heat source is away from the sensor (2nd to 4th layers). The root-mean-square error (RMSE) of the heated layer decreased from 10 K (a priori) to 4.8 K. Although the RMSE of the temperature distribution was approximately the same regardless of the number of spectral channels used in the retrieval, the RMSE of the heated layer was smaller when ten spectral channels were used. In the case of a target space and spectrometer, as in this study, ten spectral channels were sufficient. These findings indicate the possibility of remotely measuring the air temperature distribution in a space with a local heat source (e.g., data centers), which is a relatively difficult case for remote sensing methods.

Physical meaning of temperature and evaluation of distribution laws (in the area of the Lake Sevan basin)

Formulation of the problem. In the work, the most general definition of temperature was discussed and presented, the temporal probability distribution of air temperature was analyzed and evaluated. Temperature has no specific definition. Thus it will be difficult to study the nature of any geophysical phenomena, including the characteristics of temperature distribution, without understanding the modern scientific definition and adjustment of temperature. The aim of the work is to give the most modern reasonable definition of temperature or what the thermometer measures, the answer to which requires a more specific scientific justification, as well as to evaluate the patterns of possible spatiotemporal distribution of air temperature in the territory of Armenia and in the area of the Lake Sevan basin. Methods. To solve the set tasks, the authors used corresponding research and published works as a theoretical basis in the work. In the work, the average monthly data of actual observations of the temperature of the ground surface air layer and the amount of precipitation of the «Center for Hydrometeorology and Monitoring» SNCO of the Ministry of Environment of the Republic of Armenia were used. It was found that temperature is a quantity characterizing the thermal state and radiation of the terrestrial and celestial bodies and, in general, the environment, which is strongly related to the entropy change of the system; temperature is the main thermodynamic characteristic of thermal equilibrium; the thermodynamic and microscopic concepts of temperature coincide; the temperature-heat (energy) difference becomes known in the sense that a system can have high energy but low temperature. The authors applied the following research methods in the article: mathematical and statistical, extrapolation, analysis, analogy, correlation, cartographic. Results. Energy depends on the geometry (dimensions) of the system, but temperature does not. A trend of increasing air temperature is observed in the RA territory, which is also a result of the entropy change of the system. It can change very quickly, depending on the environmental factors in the given area (the growth rate of greenhouse farms, the artificial filling of valleys, which are wave carriers of air flow, the relentless use of green spaces for the purpose of public buildings, and other factors) in the process of disrupting the excessively permissible norms, which are currently separate needs serious research and prevention. The long-term variability of surface air temperature in the area of the Lake Sevan basin is analyzed. The analysis carried out made it possible to give a quantitative assessment characterizing the climate change in this region over the past 98 years. An analysis of the observational data showed that the trend of climate warming is confirmed by an increase in air temperature both in winter and over a long period of time. The change in surface air temperature occurs at a rate of 0.002 ºС/year to 0.012 ºС/year and is generally 0.008 ºС/year (or 0.08 ºС/10 years) for all analyzed stations. The results obtained confirm the presence of two periods of warming observed in 1927–1970 and 1971–2021. All the results obtained in the course of the work testify to the trend of climate mitigation in the area of the Lake Sevan basin at the end of the 20th - beginning of the 21st century.

Finite element analysis on heat convection effect on air temperature distribution in a heated room

Using the finite element method to solve heat transfer problem in solid medium has been popular since last century, but heat convection effect in fluid medium makes the problem cumbersome to solve efficiently. Thermal transfer calculation of fluid medium is complicated, because solving heat convection and Navier-Stokes equation is hard. By making proper assumptions, intricate equations can be skipped, and it is possible to give rough estimate of heat transfer result through a simple and efficient calculation. Which is significant for design and verifiction of heating system for physicists and engineers. The study aims to solve the temperature distribution of a certain heat system, using finite elment method and with given assumpted air circumfluence. In the calculation, the room domain is subdivided into finite elments, and the boundary condition is given according to the heat influx and emmision, air circumfluence is introduced to simulate the effect of convection. The simplified model illustrated that the finite element method is effective in giving quantitative result of heat transfer calculation. It also qualitatively showcased the significance of heat convection, when the result is compared to calculation without any air flow.

Air velocity and temperature distribution in culverts

Uneven frost heave in roads and railways is a frequent problem in cold regions leading to degradation of structures. To improve drainage, culverts are frequently integrated into road and railway embankments. The presence of culverts changes the temperature distribution in the surrounding soil as cold air passes through the culvert. Consequently, frost depth and corresponding frost heave are increased in the vicinity of the culvert compared to the rest of the structure if frost susceptible soil is present. For an accurate frost related design, information of heat balance between the culvert and the surrounding soil is needed. A field study focusing on convective heat transfer in culverts was conducted in northern Sweden by the authors. Temperatures and air velocities in culverts of three sizes (0.6, 0.8 and 3.4 m) were recorded. Analysis of obtained data is presented in this paper with emphasis on the influence of air velocity on the temperature distribution. Influence of wind on development of airflow in culverts is also addressed. Accuracy of trained gaussian process regression (GPR) models is estimated in predicting temperature distribution inside of culverts. It is concluded, based on the field measurement data, that airflow can significantly affect temperature distribution inside culverts and development of airflow in culverts is largely influenced by the orientation of the culvert in relation to the predominant wind direction.

Study on the Influence of the Tube Bundle Arrangement on the Performance of Condenser in Nuclear Power Plant

Nuclear power generation technology is obviously a safe and economical way of generating power in modern society. As the low temperature heat source, the condenser of the nuclear power technology condenses the steam into condensate water and then establishes a certain degree of vacuum at the exhaust port of the turbine. The operation of condenser is critical to the nuclear power generation technology. In this paper, the influences of the arrangement of tube bundles on the condenser of nuclear power generation technology were investigated. Three types of condensers, including the church window type, the centripetal type, and the UT type, were analyzed using Ansys Fluent software. The steam flow velocity distribution, air concentration distribution, temperature distribution, and heat transfer coefficient distribution were studied. Under specific design conditions, the flow velocity in the church window type was large, the exhaust air concentration was small, the maximum flow rate distribution was relatively reasonable, and the air concentration distribution was more concentrated. The performances of the centripetal type and the UT type were slightly worse, and the steam condensation was less. In contrast, the condensation of the church window type was large, the relative performance was high, and the heat transfer performance was better.

メソ気象モデルWRFを用いた堺市の人口減少に対応した緑地配置シナリオの気候分析

This study aimed to understand how different green spaces allocation would moderate higher urban temperatures. Specifically, numerical simulation was performed for understanding air temperature and wind distribution in August 2020, and the Weather Research and Forecasting meso-scale meteorological model was used in Sakai City. Furthermore, we performed climate simulation under three future green spaces allocation scenarios corresponding to population decline. In addition, climate analysis maps were created for each of these scenarios, and a comparison and discussion were conducted on how Sakai City’s green spaces should be arranged to accommodate future population decline. The results showed that conservation of green spaces reduced high temperatures in the city as a whole, but the distribution trends of temperature reduction area differed among the scenarios. These results suggested that while a large area of green spaces was effective in reducing temperatures locally, the green space network can also extend the temperature reduction over a wider area.

Numerical investigation of air entrainment and wall temperature of a real-scale infrared suppression device with slots of gradient height

The high-temperature funnel walls of the infrared suppression (IRS) device are significant sources of infrared radiation on warships, so that the cooling of the funnel walls becomes indispensable for achieving infrared stealth. In this study, the air entrainment and wall temperature distribution of a real-scale IRS device are investigated in detail. Numerical computations are performed to solve the relevant governing equations in a 2D computational domain. The RNG turbulence model and the enhanced wall treatment are used in the simulations. The present work innovatively proposes to optimize the performance of the IRS device by varying the height ratio of slots between funnels. The results show that the device has the optimal air entrainment rate and temperature distribution on the funnel walls for a slot height ratio of 1.6. In addition, the impacts of nozzle Reynolds number, funnel and nozzle overlap on the air suction and funnel wall temperature are discussed as well. When the nozzle Reynolds number gets higher, an increment in air entrainment and a decrement in funnel wall temperature are observed. The negative funnel overlap and negative nozzle overlap increase the air entrainment, but adversely affect the cooling of the funnel walls.

Study on the Air Inlet Velocity and Temperature Distribution in an Inclined Tunnel with Single Shaft under Natural Ventilation

The emergence of inclined tunnels under natural ventilation has brought many new fire safety issues. The smoke movement in the tunnel is affected by the chimney effect induced by the shaft and the downstream tunnel. The characteristics of temperature distribution in inclined tunnels are different from horizontal tunnels, which is worthy of further study. A series of conditions were carried out in an inclined model tunnel with a single shaft to investigate the temperature distribution characteristics. In this study, the longitudinal air inlet velocity is used to replace the longitudinal ventilation wind velocity. Results showed that the variation of fire source location Lf,, shaft height Ls, and the tunnel slope φ have obvious effect on the air inlet velocity. Based on the previous theories and the non-dimension analysis, the formulas of the dimensionless longitudinal inlet air velocity and the distribution of the maximum smoke temperature under the ceiling are proposed, which show good consistency with the simulation results. The reduced-scale experiments were conducted to validate the results of numerical simulation. The error range between the theoretical results and the simulation results is less than 20%.

Experimental study for comparison of thermal comfort and air age between two combined ventilation systems with chilled ceiling considering occupant density

AbstractDue to the global spread of diseases and epidemics, the need to maintain a clean indoor atmosphere has received increasing attention in recent years. Therefore, there will be a need to clearly estimate and define the areas that affect human exposure to pollutants, taking into account the occupied density, which is the primary importance of this research. The capacity of the chilled ceiling combined with mixing ventilation and personal ventilation systems has been studied and compared to the chilled ceiling with mixing ventilation in terms of mean air age, temperature distribution, CO2 concentration, and thermal efficiency, with the best flow rate of the proposed system considering the occupied density in a thermally insulated office room experimentally in the climate of Iraq (Hilla, a hot and dry climate). Twelve tests were performed for four different cooling loads with cooled ceilings (0%, 0.25%, 50%, and 80%), at a constant supply air flow rate with two PV airflow modifiers for three cases. As the cooling load treated by a chilled ceiling increased, the average air temperature increased with height in all cases. The lowest values of average air age appeared in the occupied area in the case of a chilled ceiling with mixing ventilation. This study shows that the chilled ceiling combined with a mixing ventilation and personal ventilation system with a flow rate of 7.5 L/s provides thermal comfort and higher air quality in the occupied area. based on the values of air exchange efficiency and occupants’ air exchange efficiency. As a result, a flow rate of 7.5 L/s is the best option for protecting occupants from direct pollution in the breathing zone and in the surrounding microclimate, because the lower the ventilation rate, the less air is changed for occupants.

DESIGN AND IMPLEMENTATION OF A HOT WATER HEATING SYSTEM

The heating system in winter is very necessary, especially in cold areas, and there are several ways, including the use of fuel, and because of the increase in the use of fossil fuel energy and the high cost, and the risks of toxic gases resulting from fuel combustion, and this negatively affects human health. Where a heating system was designed based on the domestic heater instead of a boiler and the use of a radiator heat exchanger, a fan that enhances the air temperature distribution system in the room, and a water pump to push water into the system with an electronic control, a system equipped with digital sensors to measure the temperature. After operating the system, the temperature of the hot water ranged from 80°C to 90°C, and the atmosphere inside the test room ranged from 17°C, the finding are good from where of energy consumption and heating in a record time at an average of 25.8°C.

CFD Analysis of Solar Greenhouse Thermal and Humidity Environment Considering Soil–Crop–Back Wall Interactions

In the study of solar greenhouses, microclimate, soil, and back walls have an important influence on the greenhouse thermal environment because of their good heat storage and release characteristics. The transpiration of crops makes indoor humidity increase sharply, which is the main factor affecting indoor humidity distribution. Therefore, it is of great significance to grasp the microclimate change law of solar greenhouses and study the coupling effect of thermal and humidity environment. In this paper, based on computational fluid dynamics (CFD), a three-dimensional model of the thermal and humidity environment of a solar greenhouse is established, and the indoor temperature and humidity distribution under the influence of soil, crops, and back walls are considered. The CFD model initialization uses binary fitting functions to fit the temperature distribution of soil, back wall, and air. The distribution law of the temperature field and relative humidity field of the solar greenhouse under three different working conditions is simulated, that is, the insulation is uncovered and the ventilation window is closed during the day (G1), the insulation is uncovered and the ventilation window is opened during the day (G2), and the insulation is put down and the ventilation window is closed at night. (G3). The results show that the simulation results are in good agreement with the actual results under the three working conditions, and this paper can provide a reference for the improvement of the greenhouse structure and environmental regulation.

Numerical Analysis on the Optimisation of Thermal Comfort Levels in an Office Located inside a Historical Building

The present study examines the possibility of thermal comfort optimisation inside an office room where, due to historical heritage, it is possible to modify neither the energetic characteristic of the envelope nor the position of the inlet air vents. The distribution of global and local thermal comfort indices is evaluated in both heating and cooling conditions by establishing a computational fluid dynamics (CFD) model validated against experimental data. The obtained results demonstrate a striking asymmetry of the air velocity and temperature distribution due to the low energy efficiency of the building. In heating mode, the predicted mean vote (PMV) values were improved if the discharged air from the fan coil was at its maximal velocity. However, at the same time, the vertical air temperature gradient increased by around 0.5 °C in each working station. In the cooling condition, in the absence of the solar radiation, the minimal air-flow rate satisfied the acceptable range of the draught rate (DR), whereas in the presence of a solar load, it could not meet the required cooling load in all positions, leading to higher floor temperature. The findings of this study allow for identifying and rearranging the optimal position of working stations in terms of thermal comfort.

Experimental and numerical study of the sunspot's effect on the dynamic thermal behavior of a room equipped with an earth-air heat exchanger, in the heating season

The main objective of this research is to study the dynamic thermal behavior of the indoor air in a room equipped with an Earth Air Heat Exchanger under the sunspot effect during the heating season. For this purpose, an experimental setup was installed to measure the temperature under the effect of the sunspot movement at different locations (indoor air temperature, wall surface temperature and blowing temperature). A numerical model of the sunspot was developed under Fluent (CFD) to accurately determine the distribution of indoor air temperature, wall surface temperature, and sunspot location for any time and location. The experimental results have allowed the study to carry out two numerical model validation. The first concerning the position and shape of the sunspot and the second concerning the ground surface temperature. With a relative error of 2.57%, there was good agreement between the simulated and experimental results. The experimental results showed that the temperature difference between the irradiated and shaded areas for the floor surface and indoor air is 9.5 °C for 789.62 W/m2 of solar power received by the test cell's glazing. The numerical results showed that the average floor surface temperature is 6.85 °C higher when a sunspot is present than when its effect is ignored. These results demonstrated that on sunny days, the energy contribution of the sunspot is greater than that of the EAHE.

Measurement and evaluation of ambient temperature distribution in Mubi town, Adamawa State, Nigeria

This paper is based on measurement of ambient (air) temperature distribution in Lamurde, Mubi South local government area, Nigeria. HTC-2 digital LCD thermometer and hygrometer electronic meter manufactured by Shenzhen Oway Technology Co. Limited Guangdong, China was used to collect data in the study area and compared with the National Aeronautics and Space Administrative (NASA) values. The results of the research revealed the maximum air temperature of 29.30oC against 33.70oC (NASA). Instat 3 and Microsoft Excel statistical package were used to analyze the data obtained. The results of T-test revealed p value of 0.0009 which is considered as extremely significant at 95% confidence interval and F-test showed that f (0.08) ≤ F (0.42) which revealed that there is no significant difference between the two data because it has 75% correlation coefficient. The study concluded that the data obtained could be used for research purpose and recommended that other sophisticated equipment should be used to validate the data.

Performance of summertime temperature and wind fields under different background winds in Kowloon, Hong Kong

The increasingly frequent urban extreme heat events are adversely affecting human health and the economy worldwide. In the last three decades, Kowloon, Hong Kong, one of the most densely populated urban areas in the world, has witnessed a rapid warming rate of 0.31 °C/decade. An in-depth study of the wind and temperature environment is needed to explore the urban warming mechanisms in Kowloon. Using semi-idealised Weather Research and Forecasting (WRF) simulations, we investigated the wind flow fields over the Kowloon area under various background wind conditions. The evolution and interaction of urban heat island circulation, sea–land breeze circulation and mountain circulation under calm weather conditions were also studied. We examined weather photos of Kowloon to identify cloud locations and evaluate our predicted urban plumes. We also explored the association between background wind and spatial air temperature distribution in Kowloon. Northeasterly wind conditions can lead to high temperatures at the foothills of mountains situated northeast of Kowloon; a streamline analysis showed that heat advection accounts for this phenomenon during the day, while a possible foehn-like wind plays an important role at night. These insights into the wind and thermal environment in Kowloon can contribute to the interpretation and prediction of extreme heat events.

Experimental and Numerical Simulations of a Solar Air Heater for Maximal Value Addition to Agricultural Products

Agriculture is the backbone of Pakistan’s economy. Currently, the agricultural sector is facing many challenges, especially post-harvest losses, which result in lower yield and profitability. These losses may be reduced by developing indigenous post-harvest processing technologies, such as drying out of agricultural products to enhancement of their sustainability and reduce transportation costs. The country has the advantage of an abundant amount of solar insulation, which can be effectively utilized to operate post-harvest machinery, particularly solar heaters and dryers. Currently, conventional solar heaters face challenges due to lower efficiencies. Therefore, in this study, a solar air heater (SAH), having a size 1220 × 610 × 65 mm, was designed and developed to be connected to a milk powder spray drying system for converting raw milk to powder. Computational fluid dynamics (CFD) were used to anticipate air flow and temperature distribution across the SAH to evaluate optimal performance parameters. An air mass flow rate of 0.01 kgs−1 was required, with the CFD predicting an outlet temperature of 82 °C compared with the experimental observation of 73 °C. The pressure drop across the SAH was recorded to be 0.0000434 bar at this flow rate, which is negligible, with the SAH operating near ambient pressure. The overall heat loss coefficient for convection was 2.27 W. m −2·K−1. The energy losses from the SAH were 37% and the useful energy was 63% of the total energy provided to the SAH. The breakeven point of SAH at a minimum of 4 h of daily usage was 3700 h or 2.5 years. The solar air heater used as a preheater for a spray dryer can save 30 PKR·kWh−1 of energy.

Investigation on the indoor environment during a whole cooking process under constant make-up air organization in a Chinese-style residential kitchen

A large amount of heat and particles generated from cooking have a negative impact on occupants’ thermal comfort as well as the indoor environment in the kitchen and adjacent rooms. Although heat generation rate and emission strength of particles are largely affected by oil temperature and cooking duration, there is a lack of quantification on the impact of the indoor environment during the whole cooking process. This study applies a computational fluid dynamics method to simulate air temperature, velocity and particle distribution in a kitchen and indoor environment during a 10-min and after 2-min cooking process with constant make-up air organization from window opening in a Chinese-style residential kitchen. User-defined function was defined for dynamic oil temperature and emission rate based on experimental results from previous studies and was interpreted in FLUENT for transient simulation within 12 min. Results indicate that heat spread remarkably after 30 s of oil heating. Air temperature experienced an increase of about 10.0°C around the occupant during the whole cooking process. For particle distribution, a large variation in the kitchen was observed after 4 min. Particle concentration in an indoor environment was increased dramatically after 6 min. Further studies on the transmission mechanism of heat and particles from the kitchen space to an adjacent room under different cooking scenarios are needed for the design and control of kitchen ventilation.

On the Performance of Diffuse Ceiling Ventilation in Classrooms: A Pre-Occupancy Study at a School in Southern Sweden

The implementation and application of diffused ceiling ventilation (DCV) is gradually gaining momentum, especially in Denmark, Finland, and the Netherlands. In countries such as Sweden, the application is limited despite the favorable conditions for implementation. The current study investigates the performance of DCV and mixing ventilation in a pre-occupancy field study for newly renovated classrooms in Southern Sweden. Two classrooms at the school were installed with diffuse ceiling ventilation while the rest had mixing ventilation. The objective of the study was to compare and evaluate the ventilation performance in terms of indoor environmental quality parameters such as thermal comfort, air quality indexes, airflow, and temperature distribution. Pre-occupancy measurements were performed in two classrooms with similar room characteristics, with one room running under mixing ventilation and the other under DCV. Constant temperature anemometers, thermocouples, and INNOVA thermal comfort were used to measure the indoor air speeds, temperature, and thermal comfort, respectively. Tracer gas measurements, with SF6, were performed to assess air quality. Additionally acoustic measurements were conducted to assess the acoustic benefits of DCV on reducing ventilation noise. The results demonstrate that DCV offers similar indoor environmental conditions to mixing ventilation but has better acoustic performance especially on reducing the ventilation noise. Indoor environmental conditions were very homogeneous under DCV with mixing ventilation showing tendencies for short circuit ventilation. This study demonstrates that DCV has a potential for implementation in Swedish schools with minimal system modification on existing ventilation and air distribution systems.

Study on winter thermal environmental characteristics of the atrium space of teaching building in China's cold region

The thermal environment of atrium space is complex and its formation mechanism is special. The scientific evaluation of atrium space can help guide the development of appropriate ventilation and heating modes, reducing energy consumption and improving thermal comfort. Through field measurement and questionnaire, the indoor thermal environment and its un-uniform characteristics of the atrium space in winter, as well as the user's behavior habits and subjective thermal feeling are systematically analyzed. Statistical regression analysis method is used to fit and evaluate factors such as operative temperature and thermal comfort, quantitatively reveals the thermal environment needs of atrium users. The study demonstrate that the predicted thermal sensation vote is slightly cold, and the measured thermal neutral temperature of the occupants is lower than the predicted thermal neutral temperature. Furthermore, this study demonstrates the distribution of air temperature in horizontal direction and its influencing factors; in addition, reveals the trend of air temperature with time and height and establishes a fitting equation between air temperature and elevation. The data obtained in this study can provide valuable reference for the construction and operation of college atrium space in cold regions.

A simple method for the estimation of minimum and maximum air temperature monthly mean maps using MODIS images in the region of Murcia, Spain

Air temperature records are acquired by networks of weather stations which may be several kilometres apart. In complex topographies the representativeness of a meteorological station may be diminished in relation to a flatter valley, and the nearest station may have no relation to a place located near it. The present study shows a simple method to estimate the spatial distribution of minimum and maximum air temperatures from MODIS land surface temperature (LST) and normalized difference vegetation index (NDVI) images. Indeed, there is a strong correlation between MODIS day and night LST products and air temperature records from meteorological stations, which is obtained by using geographically weighted regression equations, and reliable results are found. Then, the results allow to spatially interpolate the coefficients of the local regressions using altitude and NDVI as descriptor variables, to obtain maps of the whole region for minimum and maximum air temperature. Most of the meteorological stations show air temperature estimates that do not have significant differences compared to the measured values. The results showed that the regression coefficients for the selected locations are strong for the correlations between minimum temperature with LSTnight (R2 = 0.69–0.82) and maximum temperature with LSTday (R2 = 0.70–0.87) at the 47 stations. The root mean square errors (RMSE) of the statistical models are 1.0 °C and 0.8 °C for night and daytime temperatures, respectively. Furthermore, the association between each pair of data is significant at the 95% level (p<0.01).