Some Aspects of Improving the Efficiency of Air Treatment in the Contact Units of HVAC Systems

2017 ◽  
Author(s):  
Alexander Gvozdkov ◽  
Olga Suslova
Keyword(s):  
Energy Efficient ◽  
Experimental Studies ◽  
Water System ◽  
Hvac Systems ◽  
Moisture Exchange ◽  
Air Treatment ◽  
Working Space ◽  
Transition Area ◽  
Criterial Equations ◽  
Heat And Moisture

One of the main issues of improving the efficiency of air treatment in ventilation and air conditioning systems (HVAC systems) is development of methodology for the realization of energy-efficient air treatment processes in the contacting units. This paper investigates the thermodynamic models of “air-water” system, considering some features of the transition area at the interface, including surface phases and boundary layers of air and water. It has a great impact on the efficiency of processes of heat and moisture exchange in the contact units HVAC systems. The paper presents the results of experimental studies to determine the air-water interfaces temperature when achieving a state of thermodynamic balance condition in contacting media (air and water) in the working space of contact units. It was found that the surface temperature is determined by state of the surface phase and depends on the direction process of heat and moisture exchange (condensation or evaporation). The temperature factor k = Tdry/Ts as a criterion for determining the effect of the state transition area on the processes of heat and moisture exchange, was used. Processing of results from experimental researches in the processes of heat and mass transfer is presented in the form of criterial equations for Nu, Nu. Results of the performed research are the basis for the formulation of theoretical ideas about the energy efficient processes and the development of a new method for calculation of the contact units HVAC systems.

scholarly journals Opportunistic Large Array Propagation Models: A Comprehensive Survey

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4206
Author(s):  
Farhan Nawaz ◽  
Hemant Kumar ◽  
Syed Ali Hassan ◽  
Haejoon Jung
Keyword(s):  
Energy Efficient ◽  
Large Scale ◽  
Performance Metrics ◽  
Experimental Studies ◽  
Cooperative Transmission ◽  
Analytical Models ◽  
Future Research ◽  
Large Array ◽  
Propagation Models ◽  
Comprehensive Survey

Enabled by the fifth-generation (5G) and beyond 5G communications, large-scale deployments of Internet-of-Things (IoT) networks are expected in various application fields to handle massive machine-type communication (mMTC) services. Device-to-device (D2D) communications can be an effective solution in massive IoT networks to overcome the inherent hardware limitations of small devices. In such D2D scenarios, given that a receiver can benefit from the signal-to-noise-ratio (SNR) advantage through diversity and array gains, cooperative transmission (CT) can be employed, so that multiple IoT nodes can create a virtual antenna array. In particular, Opportunistic Large Array (OLA), which is one type of CT technique, is known to provide fast, energy-efficient, and reliable broadcasting and unicasting without prior coordination, which can be exploited in future mMTC applications. However, OLA-based protocol design and operation are subject to network models to characterize the propagation behavior and evaluate the performance. Further, it has been shown through some experimental studies that the most widely-used model in prior studies on OLA is not accurate for networks with networks with low node density. Therefore, stochastic models using quasi-stationary Markov chain are introduced, which are more complex but more exact to estimate the key performance metrics of the OLA transmissions in practice. Considering the fact that such propagation models should be selected carefully depending on system parameters such as network topology and channel environments, we provide a comprehensive survey on the analytical models and framework of the OLA propagation in the literature, which is not available in the existing survey papers on OLA protocols. In addition, we introduce energy-efficient OLA techniques, which are of paramount importance in energy-limited IoT networks. Furthermore, we discuss future research directions to combine OLA with emerging technologies.

Development of an energy-efficient personalized thermal comfort driven controller for HVAC systems

Energy ◽  
2021 ◽  
pp. 121568
Author(s):  
Cihan Turhan ◽  
Silvio Simani ◽  
Gulden Gokcen Akkurt
Keyword(s):  
Thermal Comfort ◽  
Energy Efficient ◽  
Hvac Systems

Supporting the Energy Efficient Ship Design Process with Energy Flow Simulations: Case Efficient Cooling Water System

2015 ◽  
Author(s):  
M Elg ◽  
◽  
M Kuosa ◽  
K Tammi ◽  
P Mäkipeska ◽  
...  
Keyword(s):  
Design Process ◽  
Energy Efficient ◽  
Energy Flow ◽  
Water System ◽  
Cooling Water ◽  
Ship Design ◽  
Flow Simulations ◽  
Cooling Water System

STUDY OF EXTERNAL MASS TRANSFER DURING DRYING OF BERRY RAW MATERIALS TAKING INTO THE SHRINKAGE PHENOMENON

2019 ◽  
Author(s):  
А.В. АКУЛИЧ ◽  
Л.А. ГОСТИНЩИКОВА
Keyword(s):  
Mass Transfer ◽  
Energy Supply ◽  
Raw Materials ◽  
Mass Transfer Rate ◽  
Experimental Studies ◽  
Volume Shrinkage ◽  
External Mass Transfer ◽  
Transfer Coefficients ◽  
Ir Radiation ◽  
Criterial Equations

Исследованы закономерности внешнего массообмена при сушке ягодного сырья для различных способов энергоподвода. Установлено, что ягоды при сушке подвержены значительной объемной (72–81%) и линейной (35–43%) усадке, которую необходимо учитывать при расчете коэффициентов массоотдачи. Объекты исследования – ягоды черники, красной и черной смородины. Проведены экспериментальные исследования по сушке ягодного сырья при конвективном и конвективном с ИК-излучением способах энергоподвода. Исследования проведены при скорости сушильного агента хса1,2 м/с и температуре tса 70°С. Получены критериальные уравнения внешнего массоообмена при сушке ягод для периода постоянной скорости, учитывающие объемную усадку. Определено, что при сушке с конвективным энергоподводом объемная усадка при одном и том же значении критерия Рейнольдса оказывает на 12–20% большее влияние на интенсивность массоообмена для красной смородины по сравнению с черникой и черной смородиной. При сушке с конвективным энергоподводом, ИК-излучением и предварительным прокалыванием объемная усадка наиболее существенно влияет на массообмен для черной смородины, протекающий в 1,5–1,8 раза интенсивнее по сравнению с черникой и красной смородиной. Полученные критериальные уравнения могут быть использованы при расчете и проектировании установок для сушки ягодного сырья. The laws of external mass transfer during drying of berry raw materials for various methods of energy supply are investigated. It is established that the berries during drying are subject to significant volumetric (72–81%) and surface (35–43%) shrinkage, which must be taken into account when calculating the mass transfer coefficients. The objects of the study were various berries: blueberries, red and black currants. Experimental studies have been carried out on the drying of selected berries both in the case of convective and convective methods with IR radiation. Investigations were carried out at a drying agent velocity хса1,2 m/s and its temperature tca70°С. The criterion equations of external mass transfer during drying of berries for a period of constant speed, taking into account the volume shrinkage, are obtained. It was determined that during drying with convective energy supply, volume shrinkage with the same value of the Reynolds criterion on 12–20% has a greater effect on the mass transfer rate for red currants. When drying with convective energy supply, IR radiation and preliminary piercing, the volume shrinkage most significantly affects the mass transfer for black currants, which is 1,5–1,8 times more intense than blueberries and red currants. The obtained criterial equations can be used in the calculation and design of berries dryers.

Temporal changes of mobile forms of 90Sr on Pripyat River floodplain in vicinity of Chornobyl NPP: measurements and risk assessments for river water contamination

2021 ◽  
Author(s):  
Gennady Laptev ◽  
Oleg Voitsekhovych ◽  
Valentyn Protsak ◽  
Mark Zheleznyak ◽  
Kenji Nanba ◽  
...  
Keyword(s):  
Coming Out ◽  
Water Contamination ◽  
Soil Layer ◽  
Experimental Studies ◽  
Water System ◽  
Water Soluble ◽  
Computational Grids ◽  
Exclusion Zone ◽  
Drastic Increase ◽  
Fuel Particles

<p>Since the 1986 Chornobyl accident transport of radionuclides by Pripyat River shares more than 90% of the annual total flux of radioactivity coming out the Chornobyl Exclusion Zone (ChEZ).  90Sr was the main contributor to this flux. In course of time destruction of the accidentally dispersed "fuel particles" leads to increase of mobile, e.g. water-soluble, forms of 90Sr  on territories affected by, while fixation of 137Cs in soil is reflected by significant reduction in 137Cs aquatic transport outside the ChEZ.</p><p>Heavily contaminated floodplain of the Pripyat River, located in vicinity of ChNPP upstream of Yaniv Bridge up to Ukrainian - Belorussian border, was considered as a “hotspot” with highest risks to the Pripyat and Dnipro water contamination due to recurrent flooding of these territories. This was evidently elucidated after the 1991 ice jam event when drastic increase of 90Sr in water was observed. The dikes splitting leftbank floodplain from the Pripyat river channel were constructed in 1992-1993. Yet, it is still important to quantify the amount of 90Sr that can be washed off the floodplain due to potential dike breakage caused by the extreme floods. </p><p>Key parameters used to describe status of radionuclide in reaching equilibrium in soil-water system are the distribution coefficient (Kd) and kinetic rate that is reciprocal of typical time scale of desorption processes. These parameters subsequently were estimated in 1991 on the basis of batch experiment carried out with the soil monoliths sampled from the Pripyat floodplain ( Laptev and Voistekhovich, 1991). Results were used in the 2D model COASTOX for justification the construction of protecting dikes (Zheleznyak at al., 1992).</p><p>To analyze current ability of 90Sr to be washed off the floodplain, soils monoliths were collected in 2020. The experimental studies of the soil cores collected from same location as the monoliths allowed to estimate mobile speciation of 90S and calibrate mass-exchange parameters. Amount of the readily exchangeable forms of 90Sr in soils significantly increased from 10-30% in the first years after the accident up to 65-75% as to 2020. Results of field and laboratory  studies were used for simulation the scenarios of 90Sr washing off the floodplain during the dikes breaks on the basis of contemporary version of COASTOX model, that includes the parallel algorithms for numerical solution of the model equations on the unstructured computational grids for multi CPU and GPU systems. Approaches for the modelling of the secondary release of 90Sr due the rapid destruction of “fuel particles” are considered. Taking into account two concurrent processes - decrease of amount of 90Sr in uppermost soil layer due to decay and downward vertical migration (1), amid increased amount of exchangeable forms of 90Sr (2), one could project subsequent increasing of 90Sr  in Pripyat and Dnipro river waters downstream the source in case of the dike breakage scenarios. On the other hand, computer simulation suggests that the maximal values of the 90Sr concentrations expected to be not higher than the measured ones during the high floods events after the accident.</p><p> </p>

scholarly journals Determining the effective drop size when modeling heat and moisture exchange in the spray chamber

2019 ◽  
Vol 1382 ◽  
pp. 012081
Author(s):  
A Ch Zandaraev ◽  
R Sh Mansurov ◽  
T A Rafalskaya ◽  
N N Fedorova
Keyword(s):  
Drop Size ◽  
Spray Chamber ◽  
Moisture Exchange ◽  
Heat And Moisture
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