Air Temperature Drop Research Articles

Nonlinear simulation for coupling modeling of air humidity and vent opening in Chinese solar greenhouse based on CFD

The Chinese solar greenhouse (CSG) ensures farming activities to continue and allow the harvest timing to be manipulated and become an important part of Chinese agricultural facilities. Effective control of the solar greenhouse environment is critical for the well-being of crops and is important for the entire Eco-agricultural System. The rapid exchange of energy and materials in the CSG with the external environment are achieved through the natural ventilation of the upper vent and the lower vent. However, there is lack of relevant research that addresses the vent opening. In this study, the effect that the vent opening has on the CSG was studied through Computational Fluid Dynamics (CFD) simulation. The ventilation of a real solar greenhouse was simulated by establishing a 3D simulation model of the solar greenhouse with various vent openings. The main focus was the relationship between the vent opening and the air humidity changes in the CSG. This study presents a coupling between an energy balance model and a CFD model to study relationships between ventilation and humidity in a CSG. The simulation results demonstrated that natural ventilation increased along with the increasing of vent openings, which caused to a drop of air humidity and temperature in the solar greenhouse. This reduction was not a linear change in the traditional cognitive paradigm, but showed nonlinear changes through the simulation results. The requirements for the verification of simulation results were used to conduct a scale model to verify the results of the CFD experiments. The practical value and the significance of the research aims to provide basic reference for controlling the indoor air temperature and the air humidity by the natural ventilation of vents. The outcome could result in a reduction in energy consumption and GHG emissions in the greenhouse operations, which contributed to the improvement of resource efficiency and a cleaner production. These results have strong practical significance for the follow-up automation and intelligent control of CSG environments.

A novel inlet air cooling system based on liquefied natural gas cold energy utilization for improving power plant performance

The performance of gas turbine-based power plants decreases significantly as ambient temperature increases. For improving power plant performance, this paper proposes a novel inlet air cooling system based on liquefied natural gas cold energy utilization. The novel system consists of two organic Rankine cycles in series and a mechanical vapor compression chiller. A simulation-based optimization method is developed to optimize its design parameters for maximizing the power plant performance. Moreover, the off-design performances of the proposed system and the power plant with and without inlet air cooling are evaluated under different ambient conditions. The results show that the novel inlet air cooling system gives larger air temperature drop (2.1–5.3 °C) and higher cooling duty (6.9–7.3 MW) than a literature design. Furthermore, for 28–40 °C ambient temperatures, the power plant with the novel inlet air cooling produces 1.83–14.4% (6.4–52.6 MW) higher power output than that without inlet air cooling. Importantly, the novel cooling system improves the plant power output by 0.79–3.04% (2.8–11.1 MW) when compared with the literature design. Finally, the economic analysis shows that the proposed system is economically viable with a net present value of $1.6–34.4 million higher than the literature design.

서울지역 PM2.5 오염원의 시계열적 기여도 평가와 헤이즈의 유형분류

Huge hourly PM2.5 datasets monitored at the Seoul Intensive Monitoring Station (SIMS) during Jan. 1, 2013 to Dec. 31, 2014 were obtained from the National Institute of Environmental Research (NIER). A total of 12,376 samples consisting of 24 chemical variables and 3 meteorological variables had been applied for the positive matrix factorization (PMF) modeling based on a dataset segmentation scheme in the previous study (Park et al., 2019). After performing the receptor model, 14 independent PM2.5 sources were successfully identified and quantified at the SIMS. In this study, based on the meteorological variables and the previous PMF results, we assessed intensively the PM2.5 source contributions by time sequential analyses such as hourly, daily, weekly, monthly, and seasonal analyses and further we classified haze patterns into 3 types such as foreign-oriented type, domestic-oriented type, and mixed type, judging from PM2.5 source contribution. According to our intensive study on wintertime haze cases, all the episode events in Seoul area initially began with rapid and big air temperature drop for several days and then high PM2.5 concentration appeared right after rapid and big air temperature rise until air temperature rose again, which forming frontal inversion with slower wind speed and then lowering a mixing height causing concentration buildup. The most dominant PM2.5 source among 14 identified sources in Seoul area was secondary aerosol source, which was considered to be transported distantly from overseas. The seasonal source contribution was summer 15.8 μg/m³, spring 14.4 μg/m³, winter 10.4 μg/m³, and fall 5.4 μg/m³ in mass order. On the other hand, secondary nitrate source as another secondary aerosol was identified as one of domestic sources. The range of seasonal source contribution was in the range of 1.0∼2.4 μg/m³ and further weekly and monthly variations were relatively small. However, its hour variation was greatly changed, up to 4.5 μg/m³ during nighttime. We hope that the results of the study can be used as basic information whenever establishing reasonable air quality management and policy in Korea.

Large Eddy Simulation and Experimental Analysis of Combustion Dynamics in a Gas Turbine Burner

Large eddy simulations (LES) and experiments (planar laser-induced fluorescence of the hydroxyl radical (OH-PLIF) and pressure transducer) have been carried out on a gas turbine burner fitted to an atmospheric combustion rig. This burner, from the Siemens SGT-800 gas turbine, is a low NOx, partially premixed burner, where preheat air temperature, flame temperature, and pressure drop across the burner are kept similar to engine full load conditions. The large eddy simulations are based on a flamelet-generated manifold (FGM) approach for representing the chemistry and the Smagorinsky model for subgrid turbulence. The experimental data and simulation data are in good agreement, both in terms of time averaged and time-resolved quantities. From the experiments and LES, three bands of frequencies of pressure fluctuations with high power spectral density are found in the combustion chamber. The first two bands are found to be axial pressure modes, triggered by coherent flow motions from the burner, such as the flame stabilization location and the precessing vortex core (PVC). The third band is found to be a cross flow directional mode interacting with two of the four combustion chamber walls in the square section of the combustion chamber, triggered from general flow motions. This study shows that LES of real gas turbine components is feasible and that the results give important insight into the flow, flame, and acoustic interactions in a specific combustion system.

Remote Sensing of Coastal Upwelling in the South-Eastern Baltic Sea: Statistical Properties and Implications for the Coastal Environment

A detailed study of wind-induced coastal upwelling (CU) in the south-eastern Baltic Sea is presented based on an analysis of multi-mission satellite data. Analysis of moderate resolution imaging spectroradiometer (MODIS) sea surface temperature (SST) maps acquired between April and September of 2000–2015 allowed for the identification of 69 CU events. The Ekman-based upwelling index (UI) was applied to evaluate the effectiveness of the satellite measurements for upwelling detection. It was found that satellite data enable the identification of 87% of UI-based upwelling events during May–August, hence, serving as an effective tool for CU detection in the Baltic Sea under relatively cloud-free summer conditions. It was also shown that upwelling-induced SST drops, and its spatial properties are larger than previously registered. During extreme upwelling events, an SST drop might reach 14 °C, covering a total area of nearly 16,000 km2. The evolution of an upwelling front during such intensive events is accompanied by the generation of transverse filaments extending up to 70 km offshore. An analysis of the satellite optical data shows a clear decline in the chlorophyll-a concentration in the coastal zone and in the shallow Curonian Lagoon, where it drops down by an order of magnitude. It was also shown that a cold upwelling front alters the stratification in the atmospheric boundary layer, leading to a sudden drop of air temperature and near-surface winds.

Energy, Exergy, Economic, and Environmental analysis for various inlet air cooling methods on Shahid Hashemi-Nezhad gas turbines refinery

In this paper, the effects of various compressor inlet air cooling methods to increase the performance of Shahid Hashemi-Nezhad gas turbines refinery were investigated. These methods included media, fogging, and absorption chillers as common inlet air cooling methods and pressure drop station as novel cooling method. By using the exergy, environmental, and economic analysis, the best method for compressor inlet air cooling was selected. Based on the results, the absorption chiller system had the highest compressor inlet air temperature drop and increased the thermal and exergy efficiencies of cycle by about 2.5 and 3%, respectively, in hot season. Using absorption chiller, pressure drop station, fogging, and media had further reduction in CO2 and CO than simple gas turbine, respectively. Finally based on the net present value and internal rate of return coefficients, the pressure drop station method is the most economically feasible option.

Critical relative humidity of evaporative cooling in CCPP based on thermodynamic and economic analyses

A calculation and analysis to determine the feasibility of inlet air evaporative cooling systems for combined cycle power plant (CCPP) is carried out. According to the psychrometric chart, the effects of ambient temperature and relative humidity (RH) on the temperature drop of the inlet air across an evaporative cooling system are analyzed. The power differences between CCPP with and without an inlet air evaporative cooling system in different environmental conditions are investigated. Based on the thermodynamic and economic analyses, a new concept, the critical RH, is proposed to evaluate the feasibility and economics of CCPP with inlet air evaporative cooling system considering different ambient conditions. If ambient RH is lower than the critical value, an inlet air evaporative cooling system is suitable and economical for regions considered. Sensitivity analysis of the factors affecting the critical RH is also carried out. The critical RH varies with climatic condition, electricity price, fuel price and expected payback period (PBT).

Upper Ocean and Subsurface Variability in the Bay of Bengal During Cyclone ROANU: A Synergistic View Using In Situ and Satellite Observations

In this study, the upper ocean and subsurface variability during the different phases of the cyclonic storm ROANU along the western Bay of Bengal (BoB) in May 2016 are investigated by using the moored buoys, Argos, HF radar and satellite datasets in the proximity of the cyclone track. The moored buoy observations recorded a decrease of sea surface temperature (SST) by ~ 1 °C all over the track, whereas increase in salinity by ~ 1.5 PSU was detected along with the highest wind speed of 16 m s−1, pressure drop of 14 hPa and air temperature drop of 4 °C. The cooling at the cyclone centers from the satellite data indicated higher (lower) SST drops when translation speed of the cyclone was low (high) and took more (less) time to recover to its pre-cyclone state in southern (northern) BoB. Mostly, higher SST drop was observed along the right side of the cyclone track. Interestingly, the opposite phenomenon occurred before landfall, where SST drop was higher on the left due to upwelling in the head bay as observed both from wave rider buoy (WRB) at Digha and satellite SST. The WRB near Vizag showed the maximum increase in significant wave heights by ~ 2.4 m during the passage of cyclone. Argos also captured cyclone-induced drop in temperature due to upwelling and entrainment reasonably well. In the southwestern bay, significant upwelling was observed from the Argos with drop in temperature and increase in salinity in the upper layers. However, a strong stratification was observed from Argos in the northwestern BoB due to lesser salinity and higher precipitation. The currents from in situ as well as HF radar datasets measured the increase in current magnitude during the passage of ROANU. Rotary spectral analysis showed strong inertial currents with frequency ~ 2.1 days at BD11 location, with higher amplitudes of the clockwise component during the cyclone period.

Optimization of operating parameters of earth air tunnel heat exchanger for space cooling: Taguchi method approach

In the present study, CFD-based parametric analysis is carried out to optimise the parameters affecting the temperature drop and heat transfer rate achieved from earth air tunnel heat exchanger (EATHE) system. ANSYS FLUENT 15.0 is used for CFD analysis, and k-ε model and energy equation were considered to define the turbulence and heat transfer phenomena. For a straight EATHE system configuration, four design and operating parameters, i.e., diameter of the pipe (A), length of pipe (B), inlet air velocity (C), and inlet air temperature (D), are considered at four different levels in Taguchi method. The Taguchi method is used to obtain maximum air temperature drop and heat transfer rate. The best combination of parameters for achieving a maximum drop in air temperature is A1B4C1D4 and that for obtaining maximum total heat transfer rate is A4B4C4D4. Statistical analysis reveals the percentage contribution of different factors for air temperature drop in the following order: inlet air temperature (57.80%), diameter of pipe (20.66%), length of pipe (12.03%), and air velocity (9.51%), while, for heat transfer rate, pipe diameter (53.28%), inlet air temperature (30.87%), air velocity (9.40%), and length of pipe (6.45%).

Спосіб визначення геометричних параметрів колових підкранових колій

Висвітлено проблеми визначення геометричних параметрів колових підкранових колій. Розглянуто відомі методики контролю геометрії криволінійної підкранової колії. Із появою нових сучасних електронних тахеометрів постало завдання розроблення нового способу вимірювання підкранової колії полярного крана реакторного відділення. Запропоновано нову методику визначення геометричних параметрів колових підкранових колій за допомогою електронного тахеометра, який полягає у визначенні координат точок, замаркованих на колії. На віддалях 20 мм від краю колії з інтервалом у 2,81 м розмічують керном і насвердлюють 48 точок діаметром 3 мм. Виміри виконують з трьох станцій, на яких попередньо закріплюють встановлюють три штатива з підставками, на яких послідовно встановлюють електронні тахеометри або відбивачі. Вимірювання виконують почергово в секторах 25÷7, 7÷37, 12÷42, 25÷42 і використовують міні-призму. За результатами вимірів аналітично розраховують геометричні параметри колії і дані для оптимального рихтування. Використання способу визначення геометричних параметрів колових підкранових колій згідно з пропонованим винаходом підвищує оперативність проведення виконання геодезичної зйомки, ефективність знаходження геометричних даних та зумовлює зниження витрат часу для одержання результату. За допомогою універсального апроксимуючого алгоритму знайдено радіуси та розраховано дані для рихтування колії колового крана, що допомагає знизити затрати на виконання ремонтних робіт.

Enhancement of Performance and Energy Efficiency of Air Conditioning System Using Evaporatively Cooled Condensers

ABSTRACTThis paper presents an experimental investigation of the reduction of energy consumption in a split air-conditioning system employing evaporative cooling of ambient air flowing over the condenser coil. Direct evaporative cooling is employed at the air-cooled condenser of a split air-conditioning system to cool the air flowing over the condenser coils. Different ambient conditions of air were simulated using a heater to mimic typical high temperature environments. The effect of the cooling pad thickness on the performance of the system was investigated by varying the pad thickness from 5 cm to 15 cm in step size of 5 cm. Result shows that the temperature drop experienced by the air is dependent on the thickness of the pad, as well as the condition of the inlet air to the pad. Conditions of the exit air from the pad shows that evaporative cooling can be employed as a stand-alone method for cooling of data centers, with adequate humidity control systems in place, or its output can be used to augment the performance of existing mechanical cooling systems. A decrease in power consumption of the unit is observed, with concomitant increase in coefficient of performance (COP). In addition, results obtained show that up to 44% increase in COP, and a 20% decrease in power consumption can be achieved by employing evaporative cooling. Additionally, the COP was found to increase by about 4% for every 1°C drop in refrigerant condensing temperature. Moreover, a 1°C drop in ambient air temperature causes a drop of 0.6°C in condensing temperature of the refrigerant.

Land-sea surface air temperature contrast on the western coast of Sumatra Island during an active phase of the Madden-Julian Oscillation

The land-sea surface temperature contrast on the western coast of Sumatra Island was examined using observation data obtained from the pre-Years of the Maritime Continent (YMC) field campaign from November to December 2015. Surface observations showed that, on most days, strong daytime solar radiation caused a pronounced diurnal cycle in surface air temperatures on the island, even during the local active phase of the Madden-Julian Oscillation (MJO). Sudden drops in surface air temperature occurred frequently on the island in the late afternoon and over the sea at nighttime, accompanied by precipitation. Temperatures on the island were higher than those over the sea during the daytime and lower in the night and early morning. Prior to the local active phase of the MJO, dual maxima in the land-sea surface air temperature contrast occurred in the evening and early morning. During the local active phase of the MJO, in spite of cloudy conditions, there were still large land-sea temperature contrasts during the daytime and in the early morning. In addition to the nighttime radiative cooling of the land surface, decreases in air temperature over the land due to precipitation cooling and the lower solar insolation in the MJO active phase caused the larger temperature differences in the morning. These results suggest that the decrease in air temperature caused by precipitation cooling had a substantial effect on the land-sea surface air temperature contrast on the western coast of Sumatra Island, particularly during an active phase of the MJO.

Improving the methods of polar crane runway rail parameters during a geodesic control

The purpose of this work is to show that using electronic flexible rulers, digital gradienters, electronic motometers and other special-purpose tools effectively solves the problem of automating the measuring process of polar crane runway rails geodesic parameters. It is recommended to use the special modifications for eliminating appreciable and systematic errors. The existence of radiation in the Atomic Power Station premises offers insights into the process of geodesic works. People can access the reactor building only when the reactor is not working. That's why the developed methods of geodesic measurements should provide the highest quality and reliability of obtained results, as well a partial or full measurements automation. The results of geodesic measurements are influenced by the air vibration, oscillation, and temperature drops between the floor and runwail rails levels [1–3]. During this, the contractor has to take the necessary measurements as fast as possible, which can decrease the quality and cause raw miscounts. There are a lot of methods for determining the planned-high-altitude positions of runway rail. The most famous among them are Ruskov [4, 5] and Burak methods.[6, 7]. According to the Burak method, the rail axis is marked as the middle of the surveying rod and the distances between the rail axis points are measured. According to the measurements, the radius of rail axis and the deviation of rail axis points from the radius are determined. However, this famous method is too time-consuming. It requires using 50m tape measures for measuring the distances between the rail points. It doesn't provide efficiency of measurements and further control of rail lining. Except this, you have to lift or drop the crane mechanisms to take the measurements. Deformations of runway rails may lead to the outage of works. The geometric runway rail parameters are checked in the first days of PPR, before starting the technological repair operations [7, 8]. The periodicity of defining the runway rail parameters depends on the conditions of its operation and reliability of under the crain constructions. In average, it is one cycle a year during the PPR according to the requirements in regulatory documents. That's why increasing the efficiency of geodesic checking of runway rails reliability by incorporating new methods and technologies is a significant task.

Quantifying the impact of release operations and weather conditions on the flow and temperature dynamics in the cascade-reservoir system

The objective of this study was to investigate the flow dynamics and temperature characteristics under different reservoir operation scenarios and weather conditions in the river-reservoir system, which can be used to set scientific guidelines for river management and conservation planning strategies. The calibrated three-dimensional model provided simulated unsteady water surface elevation, temperature, velocity and discharge at different layers (depths) in different locations. A series of operation scenarios were modeled to understand and quantify formation, propagation, and disappearance of density currents that are resulted from combinations of daily repeated large release (DRLR) of different durations and solar heating. DRLRs (140 m3/s) with longer durations pushed the bottom cold water further downstream and maintained the bottom water temperature cooler. Variations of weather conditions (e.g., drops of air temperature and solar radiation) directly controled variations of bottom-layer water temperature. The daily drop rate of bottom temperature was related to the rate and duration of air temperature drop. Under the practice for the water turbines running at downstream, it clearly showed the shocking withdrawal and stopping effect from the downstream operation. The velocity for the whole cross-section were almost increased with same magnitude of about 0.1 m/s at GOUS and JML.

Effects of green roofs’ variations on the regional thermal environment using measurements and simulations in Chongqing, China

In the present work, field measurement and simulation method were employed to investigate the effects of several green roofs variables on regional thermal environment in Chongqing (29°N, 106°E), China. Field experiments were conducted in two typical places. The real influence of green roofs on ambient environment was analyzed and compared with the simulation results. The software ENVI-met was employed to simulate 29 cases with different factors, including green roofs types, vegetation coverage, building height, arrangement position and regional layouts. With the aim to investigate the effect of the green roofs thoroughly, different design factors of green roofs were taken in consideration. From the aspect of cooling effect, it can be found that enclosing layout has the maximum air temperature drop, which is up to 0.5 °C. From the perspective of the uniformity of regional environmental temperature distribution, the regional thermal environment of scattered layout is better than enclosing and array layout as a whole. In addition, with the same vegetation coverage, the effectiveness of air temperature dropping of the whole region differed according to the arrangement position. Centrally arranging the green roofs upwind can effectively reduce the air temperature of the whole region. These findings can be used to improve the regional thermal environment by designing the green roofs reasonably.

Use of Larch Light Rings for an Evaluation of Volcanic Explosivity Index

Volcanic eruptions lead to a global short-term drop in air temperature, including a shortening of the growing season. A reaction to these short-term climatic changes is the formation of light rings (LRs) in Siberian larches growing in the Siberian Subarctic area. The relationships between mass formation (and spatial spread) of LRs and the Volcanic Explosivity Index (VEI) are shown based on an analysis of larch cores collected at 18 points in the northern forest–tundra from 67°32′ to 167°40′ N. The eruptions with VEI = 6 and higher statistically differ from weaker eruptions by the number of LRs and their spatial distribution. The doubtful dates of several strong eruptions are discussed.

Experimental investigations on a forced convection solar air heater using packed bed absorber plates with phase change materials

ABSTRACTIn this work, the performance of a forced convection solar air heater was evaluated using using three packed bed absorber plate configurations and compared with flat absorber plate. The phase change material (paraffin wax) was packed in the pin-fin, trianglular and circular absorber plate configurations. The performance parameters such as, outlet air temperature, thermo-hydraulic efficiency, exergy efficiency and pressure drop were predicted and compared. The results showed that the packed bed absorber plate configurations using paraffin wax have higher outler air temperature in the range of 2–5°C with 3–40% higher thermo-hydraulic efficiency and 2–20% higher exergy efficiency when compared to flat absorber plate. However, the packed bed absorver plates have higher pressure drop when compared to flat absorber plate.

Characterizing the Air Temperature Drop in Mediterranean Courtyards from Monitoring Campaigns

As microclimate modifiers, courtyards may be a good passive strategy for enhancing thermal comfort and reducing the energy demands of buildings. Thus, it is necessary to be able to quantify their tempering effect in dominant summer climates. This is frequently done using calculation methods based on CFD, but these have the drawback of their high computational cost and complexity, so their use is limited to advanced users with a high level of knowledge. Thus, an alternative is required based on a simplified method that can explain and predict the air temperature drop in courtyards. This would be extremely useful for professionals looking for the optimal design of this kind of space through energy assessment programs integrating these methods. This study proposes a simplified method of characterization that aims to identify the functional dependencies of the decrease in air temperatures in courtyards, and so to predict the air temperature inside them from that outside, if available. From the results of several experimental campaigns, three variables have been identified that characterize the decrease in the air temperature in courtyards, all of which depend on the confinement factor of the courtyard. Finally, the proposed predictive method was validated by means of an additional monitoring campaign. The results show a good fit of the calculated values to the measured ones, R2 being equal to 0.98.

A Feasibility Study of Supersonic Air Flow for Cooling Application

The theoretical study of steady, one-dimensional, isentropic, compressible fluid flow suggests that a convergent-divergent passage is required for accelerating a compressible fluid to supersonic velocities. It also reveals that along with pressure, temperature of the compressible fluid continuously decreases along the flow passage. Air is also a compressible fluid which is freely and abundantly available. Keeping these facts in mind the possibility of obtaining supersonic flow with the help of compressed air is first studied theoretically. A convergent divergent nozzle is designed and developed for obtaining supersonic flow of air. An experiment is carried out for various back pressures for verifying supersonic flow and measuring the exit temperature of air. It is observed that supersonic flow can be obtained with minimum back pressure of 1 bar. Exit temperature of air can be varied by changing the back pressure of the nozzle. Temperature drop of air as high as 18.23 0C could be obtained. These factors prove the potential of supersonic air jet as a good and environmentally friendly cooling medium especially for localized cooling applications.

Branched GDGT-based paleotemperature reconstruction of the last 30,000 years in humid monsoon region of Southeast China

The use of bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct mean annual air temperatures (MAATs) and environmental pH from soils has sparked significant interest in the terrestrial paleoclimate community. However, the reconstruction of these climate proxies from peat bogs is rare in monsoonal regions of the East Asia. This research was carried out on a core from the Shuizhuyang (SZY) peat bog located in Fujian Province. Branched GDGT (brGDGT) indexes were used for reconstructing the paleoclimate of the last 30calka. The aim was to evaluate quantitatively the MAAT and pH values since the Last Glacial Maximum (LGM) in the subtropical zone of China. Results show that the CBT-MBT′-derived MAAT at MIS 3 is about 15.6°C on average, which is followed by a significant fall at the LGM (11.7–12.1°C). The temperature difference between the LGM and the present-day value is as high as 5.8°C. The synchronous variation of biomarker and pollen proxies indicates that replacement of subtropical evergreen broadleaved forests by cold-tolerant, deciduous broadleaved forests was driven by the significant drop in air temperature. Our results also indicate that the Younger Dryas event lasted from about 12.9 to about 11.3calka, and cooling event at 3.2calka in the late Holocene was detected, showing the sensitivity of peat bogs to rapid cooling. Our pH reconstructions indicate that the pH of the bog rose during Heinrich 1 and Bølling-Allerød periods, probably due to low precipitation, and were lowest in the Holocene thermal maximum between 8ka and 2.5ka, probably due to higher precipitation. The decoupling of reconstructed MAAT and pH during particularly deglaciation and YD periods supports the hypothesis that the variations in temperature and precipitation are not always synchronous.