Horizontal Air Research Articles

Effect of Interface Bonding on Optimizing the Heat Transfer in Substrate Board With an Array of Heat Sources

ABSTRACTEffective heat distribution in electronic circuitry is essential to improve the performance and life of electronic components such as chips. This study presents a numerical analysis of heat transfer on a substrate board populated with an array of discrete heat sources, assumed to be placed in a horizontal air channel for forced convection cooling. The analysis of electronic packages is performed, taking into consideration the effect of thermal contact conductance (TCC) between the heat source (chip) and the substrate board. The dependence of the temperature distribution on the Reynolds number of air at the inlet and the heating power from the heat source is investigated for inlet velocities ranging from 0.6 to 1.4 m/s and observed to be significant. Temperature and heat transfer coefficient are observed to systematically increase with the increase in the heat dissipation from the heat source. Two configurations—inline and staggered—are analyzed, with the staggered configuration showing superior cooling performance. This improvement is attributed to the fact that staggered arrangements expose fewer heat sources to pre‐heated air before it exits the system. Additionally, the location of the heat source reaching the highest temperature is found to be highly dependent on the TCC of the bonding material between the heat source and the substrate. A hybrid optimization strategy is employed, by combining Artificial Neural Network (ANN) and Genetic Algorithm (GA) for optimizing the location of heat sources. ANN is used for predicting the temperature distribution, subsequently followed by GA to minimize the maximum temperature attained by the heat generating source by varying other control variables like TCC thickness, inlet velocity, and heat generation. The thickness of the bonding layer is varied from 0.225 to 0.271 mm and the heat generation is varied from 1000 to 2000 W/m2. Among them, TCC is observed to be an important parameter controlling the optimum location of heat generating sources. The results obtained from the proposed hybrid optimization strategy are compared with the simulation results and observed to be reasonably close.

A continuum from predictive to online feedback in visuomotor interception.

Interception, essential for activities like driving and sports, can be characterized by varying degrees of predictive behaviour. We developed a visually guided task to explore how target predictability and visibility influenced interception actions. The task featured a falling dot influenced by horizontal velocity, gravity and air friction, with predictability manipulated through external forces that altered the target's trajectory. We also introduced spatial occlusion to limit visual information. Our results show that low target variability favoured predictive behaviours, while high variability led to more reactive responses relying on online feedback. Manual responses displayed increased variability with changes in target motion, whereas eye trajectories maintained constant curvature across conditions. Additionally, higher target variability delayed the onset of hand movements but did not affect eye movement onset, making gaze position a poor predictor of hand position. This distinction highlights the different adaptive patterns in hand and eye movements in response to target trajectory changes. Participants maintained stable interception behaviours within and across sessions, indicating individual preferences for either predictive or more reactive actions. Our findings reveal a dynamic interplay between target predictability and interception, illustrating how humans combine predictive and reactive behaviours to manage external variability.

Broad-band, high-gain, low-frequency antennas for radio detection of earth-skimming tau neutrinos

A promising approach to detect high-energy tau neutrinos is through the measurement of impulsive radio emission from horizontal air showers initiated in the Earth's atmosphere. Observations at frequencies between 30 and 80 MHz seem particularly promising — if high-gain antennas focused at the horizon and blocking out as much as possible of the noisy sky are employed. Due to the large wavelengths, however, designing an antenna with the required properties is highly non-trivial at such low frequencies. In this article, we explore suitable antenna designs that provide the desired high gain, possess a smooth beam, are insensitive to ground conditions, are easily impedance-matched over the wide band, and are mechanically simple for deployment in large numbers in inaccessible terrain. In particular, we consider the “rhombus” antenna design for both horizontally and vertically polarized radiation a very attractive option for tau neutrino detection efforts in the atmosphere with the radio technique.

Research on a novel method of air distribution to create a uniform indoor environment in a long and narrow building

Because people work a long time in buildings, good indoor thermal environments and air distributions have attracted increased amounts of attention. To improve the indoor thermal environment and air quality, an effective ventilation strategy must be used. In the air conditioning of a building, the air distribution has been identified as a significant factor that affects the indoor thermal environment. A novel method for air distribution was presented to create a uniform indoor environment along the room length direction. In this study, numerical simulations were carried out to analyse the airflow pattern and performance of the sidewall air supply (SAS) and the sidewall air supply with deflector (SASD). Orthogonal experiments were conducted to study the airflow distribution law of the deflector. The ventilation performance of the two air supply modes was evaluated by air velocity distribution, temperature distribution, horizontal temperature difference, age of air, and other evaluation indicators. The results indicate that the horizontal air temperature differences in the SASD at three heights are 46.05%, 16.44%, and 26.51% lower than those in the SAS, which has a better energy-saving effect. Moreover, the indoor air distribution performance was obtained under three influencing factors: the gap width from the deflector to the ceiling, the horizontal position, and the length of the deflector. A better deflector optimization scheme was obtained. Experimental research was carried out to verify the indoor air distribution of the SASD. This research can provide a reference for the innovative design of indoor air supply systems.

Influence of atmospheric stability conditions on wind energy density in Ali Al-Gharbi region of Iraq

Atmospheric stability is considered as one of the most important factors affecting the increase or decrease in wind speed in the atmosphere and thus affects the wind energy density. This study aims to analyze the stability of the atmospheric conditions in southern part of Iraq, specifically in the Ali Al-Gharbi region, using one of methods to determine atmospheric stability called Monin-Obukhov length . Field data of horizontal and vertical wind speed and air temperature collected at three heights (10m, 30m, and 50m) in 2017 from tower installed in Ali Al-Gharbi region. The results show that the vertical wind speed increases with height up to 30 m and decreases at 50 m, while the horizontal wind speed increases as the height increases. The friction velocity , surface heat flux , momentum flux and shear stress were calculated and the stability conditions were determined. Results revealed that stable atmospheric condition was the most frequent with about 59% occasions occurring during the year followed by unstable (40%) and neutral (1%) conditions. The highest wind energy density was in stable conditions (0 ≤ L< 200), with percentage (58% - 57%) in spring season at both heights 10m and 50m, respectively, followed by unstable conditions (-200 < L ≤ 0), while the lowest wind energy density was in neutral conditions (-200 ≤ L ≥ 200) with percentage (1.3% - 0.8%) in autumn season.Atmospheric stability is considered as one of the most important factors affecting the increase or decrease in wind speed in the atmosphere and thus affects the wind energy density. This study aims to analyze the stability of the atmospheric conditions in southern part of Iraq, specifically in the Ali Al-Gharbi region, using one of methods to determine atmospheric stability called Monin-Obukhov length . Field data of horizontal and vertical wind speed and air temperature collected at three heights (10m, 30m, and 50m) in 2017 from tower installed in Ali Al-Gharbi region. The results show that the vertical wind speed increases with height up to 30 m and decreases at 50 m, while the horizontal wind speed increases as the height increases. The friction velocity , surface heat flux , momentum flux and shear stress were calculated and the stability conditions were determined. Results revealed that stable atmospheric condition was the most frequent with about 59% occasions occurring during the year followed by unstable (40%) and neutral (1%) conditions. The highest wind energy density was in stable conditions (0 ≤ L< 200), with percentage (58% - 57%) in spring season at both heights 10m and 50m, respectively, followed by unstable conditions (-200 < L ≤ 0), while the lowest wind energy density was in neutral conditions (-200 ≤ L ≥ 200) with percentage (1.3% - 0.8%) in autumn season.

Effect of the coal-spreading air on airflow and low-NOx combustion within a 75 t/h coal-fired grate furnace

Coal-fired grate furnaces equipped with coal throwers, which conventionally own a low-NOx combustion framework consisting of (i) the partitioned primary air for the horizontal air staging on the grate and (ii) the coal-spreading air and secondary air for the vertical air staging in the freeboard, actually suffer from poor burnout and apparently high NOx emissions at habitual operations. While comprehensive investigations on the in-furnace airflow, coal combustion, and NOx formation, which are devoted to first explaining and then improving these problems, are absent up to now. In order to unveil the airflow, combustion, and NOx emission characteristics within a 75 t/h coal-fired reverse grate furnace, evaluate its coal-spreading air impact on the low-NOx combustion performance, and determine an appropriate coal-spreading air ratio for improving the furnace performance, both industrial-scale tests and numerical simulations were performed at the coal-spreading air ratios of 2 %, 4 %, 6 %, and 8 %, respectively. The flow-field deflection and asymmetric combustion appeared in the upper furnace, with the upward gas deflecting towards the rear-wall side and the front-half furnace part dominated by a weak recirculation zone without effective combustion. With increasing the coal-spreading air, problems of the flow-field deflection and asymmetric combustion aggravated. The combustion intensity weakened in the layer combustion zone while displayed an increase-to-decrease trend in the suspension combustion zone. In terms of indexes related to the furnace performance, burnout rate decreased continuously, and NOx emissions initially raised but then decreased. A comprehensive consideration of the coal-spreading requirement via air, flow-field symmetry, low-NOx combustion, and burnout suggests that a 2 % coal-spreading air ratio should be preferred, where NOx emissions and burnout loss were gained at 249 mg/m3 (6 % O2) and 5.75 %, respectively. It reduced NOx emissions by 49 % while raised slightly burnout loss, as compared with the corresponding levels of 486 mg/m3 and 5.4 % at the habitual case. These results not only negate the air-staging function of the coal-spreading air but also highlight the novelty of this work.

Using mobile air cleaners in school classrooms for aerosol removal: Which, where and how

Mobile air cleaners (MACs) have been proposed as a supplementary solution to combat the spread of respiratory aerosols in school classrooms. To determine which, where and how to use MACs, seven small- and medium-sized MACs were selected and assessed for different settings and configurations by 1) a decay test for determining the clean air delivery rate (CADR), and 2) a perception test with a panel of subjects, together with physical measurements, of noise and air movement. The findings show that to achieve the desired CADR (appr. 1000 m3/h for 30 students per classroom), the key factors are the induced airflow pattern and the location of the MACs. MACs with an upward air supply toward the occupied zone showed much higher CADR (max. 775–1332 m3/h) than those with a horizontal air supply (max. 219–333 m3/h). Moreover, using multiple devices simultaneously was crucial when the room size was increased, and combining mechanical ventilation could improve aerosol removal. Achieving a sufficient CADR would always lead to a noise level above the limit of 35 dB(A), yet sometimes the rating of the panel was more than 50% acceptable. The air velocities mostly fulfilled the requirement (<0.2 m/s), which aligned with the positive panel assessment. Hence, the evaluation by a panel of subjects can help to optimize the use of MACs in a classroom.

Novel THAI well arrangements for improving heavy oil recovery rate in comparison to that achievable in the conventional THAI in situ combustion technology

The toe-to-heel air injection (THAI) method is an environmentally friendly process for in situ upgrading of heavy oils and bitumen via in situ combustion (ISC). Unlike the conventional ISC that uses a vertical producer, the THAI process uses a horizontal producer (HP) well to produce the upgraded oil to the surface. Recent field data has shown that the THAI process is a relatively low-oil-production-rate technology. These considerations call for innovative solutions so that the oil production rate is improved, whilst propagating a stable, efficient, and safe combustion front. Consequently, this work has provided those solutions. Through numerical reservoir simulations, using CMG STARS, five completely new THAI well configurations, which have been labeled A01, A02, A03, A04, and A05, have been developed and studied, and their performances are compared against that of the conventional THAI process which has wells arranged in a classic SLD pattern (i.e. the best-performing conventional THAI process) and against each other. The THAI arrangements A02-A04, however, assume a horizontal air injection well, which currently is not used in field practice but may be developed in the future. In field practice, THAI is applied in a line drive configuration starting up-dip and going down on the structure whilst taking advantage of the contribution provided by the drainage due to gravity; the expansion is made one way only (by drilling new patterns in one direction only). For this reason, the classic SLD pattern refers to the case where the dip of the reservoir is significant (>2–3°). However, when the dip of the reservoir is not significant (“flat” reservoirs) there is a possibility to expand the process in both opposing directions. This is the case dealt with in this work. All configurations A01-A05 assume expansion of the THAI commercial operation in both directions. Selection criteria have been developed and used to determine the two best performing processes. For example, in terms of long-term stability, safety, and efficiency of the combustion process, a process named model A01 is the best, as it achieved 99.8% oxygen utilisation when compared with any other model. It also achieves oil recovery, due to two years of combustion only, of 30.78% OOIP, which is greater than that in the base case model. Overall, based on the weighted selection criteria, which are developed from the deepest analyses of the quantitative 1-dimensional time-dependent parameters and from thorough analyses of the qualitative 2-dimensional profiles of temperature, the combustion zone in the form of oxygen mole fraction, and the oil-flow dynamics inside the reservoir in the form of oil saturation, then model A01 is the best and is followed by model A03. The overall performance of each of these two novel methods outweighs that of the conventional THAI process. However, model A03 uses a horizontal well for injection, which is not current field practice. Therefore, future developmental work should concentrate on the novel method A01 for upgrading and recovery of heavy oils and bitumen, especially since this is low-carbon, efficient, wastewater-free, and provides upgrading inside the reservoir and hence it has a low surface footprint.

Numerical Simulation of Particle Dispersion in an Operating Room: Assessment using Horizontal Air Supply Diffuser

Numerical Simulation of Particle Dispersion in an Operating Room: Assessment using Horizontal Air Supply Diffuser

A numerical study on transport of dust particles accompanied by air gouging process and energy consumption in a circulating ventilation workshop

A modified circulating layered ventilation system is proposed to address the issue of particulate pollutants in the casting cleaning workshop, taking into account the characteristics of end treatment and production processes. By combining Reynolds Average Navier-Stokes (RANS) turbulence model and Discrete Phase Model (DPM), the particle transport law in the coupled flow process of thermal plumes generated by purified circulating airflow and heat source was explored, and ventilation energy consumption was evaluated from the perspective of particle removal energy efficiency ratio. Comparing three ventilation modes: mixed ventilation (MV), wall-based attachment ventilation (WAV), and wall-based attachment ventilation with deflector (WAV-D), it was found that the large vortex region formed by the change in airflow direction during WAV played a key role in particle transport. Placing deflector helped to reduce the impact of vortex recirculation zones generated by the intersection of airflow and plumes on particles. A higher fresh air rate will weaken the diffusion effect of particles in the horizontal air lake region. Continuously increasing the air supply volume to a certain level has little effect on the transportation of low-inertia particles, yet it still manages to effectively enhance the removal efficiency of medium-inertia particles. However, for high-inertia particles, an increase in air supply can easily lead to excessive particle concentration in local areas. When the particle removal efficiency reaches a certain level, higher supply air volume and fresh air rate may lead to a significant decrease in energy efficiency ratio.

Enhancing air pollution mapping with autonomous UAV networks for extended coverage and consistency

In the context of today's pressing air pollution challenges, accurate and consistent air pollution mapping plays a pivotal role in understanding pollutant distribution and identifying pollution sources. While current technologies, including sensors and unmanned aerial vehicles (UAVs), have begun to address this issue, the full potential of UAV-based solutions remains largely untapped. This pioneering numerical study demonstrates the effective feasibility of precise and consistent air pollution mapping in local areas that exceed the coverage capacity of a single UAV. The approach involves employing multiple UAVs, which requires rigorous mission planning encompassing various complex stages. These stages include subdividing the mapping area into manageable sub-areas, evaluating the technical capabilities of each UAV, assigning specific tasks to UAVs, and conducting individual mapping operations. By endowing UAVs with full autonomy, horizontal air pollution maps are generated across different layers within the designated area. This method's distinct advantage is its simultaneous acquisition of vertical profiles at all points within the study region, eliminating the need for additional efforts. Through strategic technical analysis, it was revealed that each UAV's mission coverage area could be expanded by over 30%, leading to more consistent air pollution mapping. Furthermore, this finding suggests a reduction of up to 25% in the total number of UAVs required for studies covering significantly larger areas.

Ventilation performance evaluation of an operating room with temperature-controlled airflow system in contaminant control: A numerical study

This article investigates the efficacy of temperature-controlled airflow systems in modern operating rooms for contaminant control, a critical factor in preventing surgical site infections. We have conducted experimental measurements in an operating room equipped with temperature-controlled ventilation to map the airflow field and contaminant dispersion (airborne particles with diameters ranging from 0.5 to 1 μm). The results were used to validate the computational fluid dynamics code, which was then employed to simulate and examine different conditions, including contaminant release locations and air supply rates. Realizable k-epsilon and passive scalar models were utilized to simulate airflow and airborne particle phases. We assessed the airflow distribution and contaminant dispersion, utilizing indices such as ventilation and air change efficiency scales. The analysis provided quantitative insights into the distribution and removal of contaminants, as well as the speed at which the room air was replaced. Contamination was found to be effectively reduced when contaminants were released near exhaust outlets or under central unidirectional inlets. The presence of the operating table caused a big distortion of the central downward airflow, forming a horizontal air barrier at the periphery. Under this unique interior configuration, an appropriate air supply ratio between central and periphery zones was required to achieve optimal overall ventilation performance.

Experimental Study on Two-Phase Countercurrent Flow Limitation in Horizontal Circular Pipes

The two-phase countercurrent flow limitation (CCFL) in horizontal channels is important in relation to nuclear reactor safety. In this study, we aim to investigate the CCFL characteristics and the flow behaviors in horizontal circular pipes with small diameters. The effects of pipe diameter and the water head in the upper plenum on CCFL characteristics are experimentally studied. An image-processing technique and statistical treatments are implemented to analyze the horizontal countercurrent flow. The results show that the CCFL characteristics for the horizontal circular pipes with small diameters can be well correlated using the dimensionless parameters, which are based on adding fluid viscosity to the Wallis parameters. The CCFL characteristics are significantly affected by the pipe diameter and are slightly affected by the water head above the horizontal pipe. The gas–liquid interface fluctuates with certain periods, and flow pattern transitions happen in the horizontal air–water countercurrent flow. As the air flow rate increases, the occurrence location of the liquid slug appears to shift towards the water entrance. In addition, the further away from the water entrance, the lower the average of liquid holdup.

Effect of the Backboard on the Pyrolysis Front Morphology of Downward Flame Spread: A Simulation Study

In order to investigate the influence of the backboard on the morphology of the pyrolysis front, this study employed the fire dynamics simulator (FDS) to conduct simulation research, aiming to quantitatively analyze the reasons for the differences in the morphology of the pyrolysis front under two conditions: with and without the backboard. By comparing the surface temperature distribution, flow field, and air entrainment velocity at the bottom of the pyrolysis front made of polymethyl methacrylate (PMMA) under different conditions, it was found that the presence of the backboard not only reduced the surface temperature of PMMA at the bottom of the pyrolysis front and the temperature difference between the edge and middle, but also changed the flow field at the edge and suppressed the horizontal air entrainment velocity at that position, especially for thinner PMMA. These factors ultimately result in a larger angle of the pyrolysis front during the burning stable stage under the condition with the backboard compared to the condition without the backboard. In addition, the trend of horizontal air entrainment velocity at the edge position under different conditions also provide data support for the qualitative observation and analysis of previous experiments phenomena.

Variability and trends of near-surface wind speed over the Tibetan Plateau: The role played by the westerly and Asian monsoon

Near-surface wind speed exerts profound impacts on many environmental issues, while the long-term (≥60 years) trend and multidecadal variability in the wind speed and its underlying causes in global high-elevation and mountainous areas (e.g., Tibetan Plateau) remain largely unknown. Here, by examining homogenized wind speed data from 104 meteorological stations over the Tibetan Plateau for 1961–2020 and ERA5 reanalysis datasets, we investigated the variability and long-term trend in the near-surface wind speed and revealed the role played by the westerly and Asian monsoon. The results show that the homogenized annual wind speed displays a decreasing trend (−0.091 m s−1 per decade, p < 0.05), with the strongest in spring (−0.131 m s−1 per decade, p < 0.05), and the weakest in autumn (−0.071 m s−1 per decade, p < 0.05). There is a distinct multidecadal variability of wind speed, which manifested in an prominent increase in 1961–1970, a sustained decrease in 1970–2002, and a consistent increase in 2002–2020. The observed decadal variations are likely linked to large-scale atmospheric circulation, and the correlation analysis unveiled a more important role of westerly and East Asian winter monsoon in modulating near-surface wind changes over the Tibetan Plateau. The potential physical processes associated with westerly and Asian monsoon changes are in concordance with wind speed change, in terms of overall weakened horizontal air flow (i.e., geostrophic wind speed), declined vertical thermal and dynamic momentum transfer (i.e., atmospheric stratification thermal instability and vertical wind shear), and varied Tibetan Plateau vortices. This indicates that to varying degrees these processes may have contributed to the changes in near-surface wind speed over the Tibetan Plateau. This study has implications for wind power production and soil wind erosion prevention in the Tibetan Plateau.

Numerical Analysis of Air Supply Alternatives for Forced-Air Precooling of Agricultural Produce

Precooling agricultural produce is an intensive, energy-consuming process. To improve the efficiency of forced-air precooling and ultimately contribute to energy sustainability for postharvest storage of fresh produce, we designed three alternative air supply systems, simulated their cooling performances over a 96 h precooling process in a cold storage facility storing Chinese cabbages, and then compared their performances with a conventional design. All models were developed on a large scale on the basis of validated computational fluid dynamics models. The horizontal air supply scheme shortened the seven-eighths cooling time by 18.8%, and its maximum cooling rate increased by 19.7% compared to the conventional air supply scheme. The seven-eighths cooling time under another alternative design, the vertical air supply scheme, was 9.4% lower than the conventional, with the maximum cooling rate increasing by 10.5%. However, the maximum cooling rate of the last alternative design, the perforated ceiling air supply system, was 6.6% less than the conventional scheme, resulting in a 6.3% longer seven-eighths cooling time. The heterogeneity index of temperature implied that the horizontal air supply offered better overall cooling uniformity than the other designs, which can be attributed to its evenly distributed airflows and well-organized air movement paths, based on the combined analysis of temperature contours and air velocity contours at selected planes. Our findings are expected to provide practical guidelines for the refinement of the air supply system to improve its energy sustainability in forced-air precooling.

FDTD Analysis of Electric Field and Step Voltage in a Clay‐Wall House Struck by Lightning

The density of lightning flashes is quite high in Rwanda and its neighboring countries in Africa. In rural areas of these countries, there are still many clay‐wall houses. Sometimes people in clay‐wall houses are fatally injured by direct lightning strikes to the houses. In this paper, the electric field in a clay‐wall house and the step voltage on the floor, associated with a direct lightning strike to the house, are analyzed using the finite‐difference time‐domain (FDTD) method. Also, the electric field and the step voltage in the same clay‐wall house but with a horizontal air termination conductor connected to buried vertical bar earth conductors or a square ring earth conductor via bare or insulated down conductors are analyzed using the FDTD method. It has been shown that installing these protection systems reduces the inside electric field and the step voltage on the floor particularly if insulated down conductors are employed. © 2024 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Study on the gas phase migration and distribution characteristics in horizontal well air sparging remediation

Horizontal well air sparging (AS) technology has been proven to be efficient in remediating saturated soils and groundwater contaminated with volatile organic compounds (VOCs). Nevertheless, the airflow patterns and the mechanisms governing uniformity in the horizontal well AS process remain elusive, and a quantitative characterization of the zone of influence (ZOI) has yet to be determined. In this study, we employed both model experiments and numerical simulations to investigate the distribution patterns of lateral airflow in horizontal air sparging tubes within a porous medium. The influence of parameters such as air sparging pressure, groundwater flow, the inclination angle of the air sparging tubes, and the diameter of the medium particles on the distribution patterns of gas-phase transport in horizontal well AS was analyzed. The results show that both groundwater flow and the inclination of air sparging tubes disrupt the uniformity of gas distribution. The ZOI area of AS is observed as an oblong shape in the horizontal plane and a parabolic contour along the boundaries. Additionally, a mutual influence is identified between groundwater flow and AS airflow. Furthermore, the inclination of air sparging tubes results in the formation of preferential flow near the air source end. The ZOI of horizontal AS demonstrates a positive correlation with air sparging pressure and a negative correlation with medium particle diameter. All of the results elucidated above provide valuable information for the design and theoretical modelling of AS within horizontal wells for groundwater remediation.

Effect of horizontal and radial airflow fans on the microclimate of single-span greenhouses and their yield

The present study evaluated and compared the distribution patterns of microclimatic parameters within greenhouses to provide insights into optimizing growing conditions and maximizing crop productivity. Experiments were conducted from January to March 2023 at Sangju Smart Farm Innovation Valley, Sangju-si, South Korea, in two adjacent greenhouses covered with two polyolefin layers and a thermal screen layer. The distinctive design of the radial airflow fan connecting to the external environment and ability to uniformly blend air, demonstrated superior performance than the horizontal air flow fan. The adoption of radial airflow fans could greatly influence commercial production by enhancing the distribution of microclimate variables, resulting in improved greenhouse efficiency and ultimately leading to increased crop yields.

Metrological Evaluation of the Building Influence on Air Temperature Measurements

This paper describes the metrological procedure carried out for the evaluation of the building influence on air temperature measurements. This evaluation aims to produce reliable conclusions, information, and data to contribute to the WMO siting classification schemes for air temperature measurements. For this purpose, a field experiment was designed, deployed, and carried out. As a result, one-year-lasting air temperature measurements were collected and analyzed. In this field experiment, a 200 m wide building is the unique artificial heat source and the unique object projecting shades over a flat surface (no discernible slope) in an open space bigger than 40,000 m2, covered with short grass. Eight calibrated thermometers, equipped with the same model of artificially ventilated radiation shields, were set up at a height of 1.5 m from the ground and at different distances from a 200 m wide building. This configuration provides the observation of the horizontal air temperature radially distributed from the building and, as a conclusion, it enables the quantification of the building influences on air temperature measurements at different distances from the building. This document describes the field experiment, the analysis procedure, the evolution of the building influence on air temperature measurements along the day, and the impact of other meteorological parameters on this building effect. Two different building effects are observed: the positive building effect, where the air temperature decreases with the distance to the building, and the negative building effect, where the air temperature increases with the distance to the building. It is also noticed that the building influence is higher on clear days and the daily maximum building influence values are directly linked with the corresponding maximum solar irradiance. The influence of wind on the building effect is also analyzed, reaching the conclusion that due to characteristic of local winds, in terms of low speed and direction, the wind impact could be considered as negligible. The maximum values of building influence on air temperature measurements, the associated uncertainty analysis, and the conclusions are presented in this paper. All these points have been addressed using metrological principles with the purpose of giving consistency and robustness to the evidence presented here.