scholarly journals Air distribution in convex wall jets for ventilation with a constant air flow

2021 ◽  
Vol 36 ◽  
pp. 37-50
Author(s):  
V. Korbut ◽  
Viktor Mileikovskyi
Keyword(s):  
Air Flow ◽  
Capital Investments ◽  
Outdoor Air ◽  
Wall Jets ◽  
Air Conditioners ◽  
Working Zone ◽  
Cooling Period ◽  
Air Supply ◽  
Convex Wall ◽  
Air Exchange

The scheme of air exchange organization using air supply above a working zone by convex wall jets that interact with each other has been substantiated. This scheme is advisable in cases where it is impossible to supply air directly to the working zone. It provides optimal microclimate parameters with minimal recirculation of polluted air from the upper zone. Simulation of the air exchange organization in an exhibition hall in International Exhibition Centre in Kyiv with ventilation at a constant air volume (CAV) has been performed. The floor area is 5258 m2, the height is 19 m, the minimum outdoor air flow is 21.667 m3/s (78000 m3/h). The current design scheme of air exchange organization is zonal. General air exchange is 43.3333 m3/s (156000 m3/h). Recirculation is accepted 50 %. The air flow supplied in the upper and middle zones is, respectively, 22.5 m3/s (81000 m3/h) and 20.833 m3/s (75000 m3/h). Inlet air has temperature 291.65 K (18.5 °C). It is supplied downward by twisted jets. There are 65 Trox VDL-AHLD-E3/800/0/0/0/RAL 9010 air diffusers with a diameter of 800 mm. The proposed scheme is single-zonal using 24 diffusers PES-D-8-10/15-0,9 4 m above the floor and air removal from the upper zone. This scheme allows halving the air exchange to the minimum outdoor air without recirculation. The air temperature should be decreased by 3.3 K to 288.35 K (15.2 °С). The number of air-conditioners is decreased twice. The calculated consumption of cold decreased by 65.58 W/m2 or 29 %, the calculated consumption of heat for the second heating – by 7.17 W/m2 or 18 %. Saving of capital investments in prices of February 2020 is 792.16 UAH/m2 or 55 %, and decrease of operating costs for the cooling period is 6.61 UAH/m2 or 15 %. Thus, the system is economically beneficial from the beginning of its installation. In the future, its operation will be simulated in a mode with a variable flow rate.

scholarly journals The use of the interaction of convex wall jets for ventilation with variable air flow

2021 ◽  
Vol 37 ◽  
pp. 7-12
Author(s):  
V.  Korbut ◽  
V. Mileikovskyi ◽  
V. Dziubenko ◽  
I.  Sachenko
Keyword(s):  
Air Flow ◽  
Branch Pipe ◽  
Geometrical Shape ◽  
Wall Jets ◽  
Cross Sectional ◽  
Working Zone ◽  
Gravitational Forces ◽  
Convex Wall ◽  
Air Circulation ◽  
Air Exchange

The most energy efficient ventilation and air-conditioning is variable air flow (VAV) depending on the needs of a room. To avoid broken air circulation by gravitational forces, the most of air diffusers should change geometrical shape and sizes using additionall automation of them. In contrast, high stability of a scheme of air exchange organization with air supply over a working zone by convex wall jets that interact with each other under conditions of variable air flow, is confirmed. This scheme is useful in cases where it is impossible to supply air directly to the working zone. Simulation of the air exchange organization in an exhibition hall of International Exhibition Centre in Kyiv with ventilation at a variable air volume (VAV) in the entire possible range of performance control has been performed. The floor area is 5258 m2, the height is 19 m. The outdoor air-flow at design conditions (100 % load) is 21.667 m3/s (78000 m3/h). The minimum load corresponds to the absence of solar radiation and only some people in the room. The minimum air-flow is 25 % of the design one. The proposal air scheme is single-zonal using 24 diffusers PES-D-8-10/15-0,9 4 m above the floor and air removal from the upper zone. The air distributor have a diameter of a cylindrical surface and an inlet branch pipe of 8 dm (800 mm). There are 10 rows of nozzles at an angle π/12 (15 °) to the horizon on each distributor. The total area of the air outlet on them is equal to 0.9 of the cross-sectional area of the inlet pipes. Due to forces of the vacuum holding of jets on the wall surfaces, the influence of gravitational forces is significantly reduced. This avoids the automation of air distribution devices to stabilize the scheme of air circulation in the room by gravitational forces. It is enough to install valves with actuators on branches of a network of air ducts. Thus, the economic benefit of the system is confirmed both at the stage of installing and during operation.

scholarly journals Numerical Study on Coupled Operation of Stratified Air Distribution System and Natural Ventilation under Multi-Variable Factors in Large Space Buildings

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8130
Author(s):  
Ziwen Dong ◽  
Liting Zhang ◽  
Yongwen Yang ◽  
Qifen Li ◽  
Hao Huang
Keyword(s):  
Thermal Comfort ◽  
Working Conditions ◽  
Distribution System ◽  
Distribution Systems ◽  
Natural Ventilation ◽  
Numerical Study ◽  
Air Distribution ◽  
Large Space ◽  
Air Conditioners ◽  
Air Supply

Stratified air distribution systems are commonly used in large space buildings. The research on the airflow organization of stratified air conditioners is deficient in terms of the analysis of multivariable factors. Moreover, studies on the coupled operation of stratified air conditioners and natural ventilation are few. In this paper, taking a Shanghai Airport Terminal departure hall for the study, air distribution and thermal comfort of the cross-section at a height of 1.6 m are simulated and compared under different working conditions, and the effect of natural ventilation coupling operation is studied. The results show that the air distribution is the most uniform and the thermal comfort is the best (predicted mean vote is 0.428, predicted percentage of dissatisfaction is 15.2%) when the working conditions are 5.9% air supply speed, 11 °C cooling temperature difference and 0° air supply angle. With the coupled operation of natural ventilation, the thermal comfort can be improved from Grade II to Grade I.

scholarly journals Outdoor Air-Cooling System for a Computer Room and Its Corresponding Energy-Saving Effect

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5719
Author(s):  
JiHyun Hwang ◽  
Taewon Lee
Keyword(s):  
Power Consumption ◽  
Energy Saving ◽  
Data Centers ◽  
Cooling System ◽  
Stable Operation ◽  
Air Cooling ◽  
Outdoor Air ◽  
Air Conditioners ◽  
Air Cooling System ◽  
Saving Effect

The recent expansion of the internet network and rapid advancements in information and communication technology are expected to lead to a significant increase in power consumption and the number of data centers. However, these data centers consume a considerable amount of electric power all year round, regardless of working days or holidays; thus, energy saving at these facilities has become essential. A disproportionate level of power consumption is concentrated in computer rooms because air conditioners in these rooms are required to operate throughout the year to maintain a constant indoor environment for stable operation of computer equipment with high-heat release densities. Considerable energy-saving potential is expected in such computer rooms, which consume high levels of energy, if an outdoor air-cooling system and air conditioners are installed. These systems can reduce the indoor space temperature by introducing a relatively low outdoor air temperature. Therefore, we studied the energy-saving effect of introducing an outdoor air-cooling system in a computer room with a disorganized arrangement of servers and an inadequate air conditioning system in a research complex in Korea. The findings of this study confirmed that annual energy savings of up to approximately 40% can be achieved.

scholarly journals Study on energy loss and thermal environment through door open while air conditioner running

2019 ◽  
Vol 111 ◽  
pp. 06035
Author(s):  
Sihwan Lee
Keyword(s):  
Energy Consumption ◽  
Indoor Air ◽  
Room Temperature ◽  
Thermal Environment ◽  
Infiltration Rate ◽  
Operating Efficiency ◽  
Air Conditioner ◽  
Air Conditioners ◽  
Cooling Period ◽  
Closed State

While air conditioner is running, opening doors and windows is a great way to reduce operating efficiency and undermine the air conditioning system’s ability to bring the indoor to a comfortable temperature. The purpose of this study is to evaluate the heat loss and thermal environment through the door open while air conditioner running. To achieve this goal, using full-scale measurement with the commercial store during the cooling period, the infiltration rate, thermal environment and energy consumption of air conditioners with door opened and door closed state were measured. The measured results show that the infiltration rate at the door opened state was increased by about 21.3 times compared to the door closed state. When the set temperature of the air conditioner was 24 °C, the room temperature in the opening gate cooling was measured to be about 5 °C higher than the closing gate cooling. However, the energy consumption was measured approximately 12 kWh/day and there was no difference with door state. This means that the energy consumption is not increased if the indoor air temperature would not reach the set point temperature of air conditioner.

scholarly journals Designing Jet Fan Ventilation for an Underground Car Park by CFD Simulations

2018 ◽  
Vol 63 (1) ◽  
pp. 39-43 ◽  
Author(s):  
Miroslava Kmecová ◽  
Michal Krajčík ◽  
Zuzana Straková
Keyword(s):  
Exchange Rate ◽  
High Efficiency ◽  
Ventilation System ◽  
Cfd Simulations ◽  
Air Exchange Rate ◽  
Air Supply ◽  
Car Park ◽  
Computational Fluid Dynamics Cfd ◽  
Alternative Designs ◽  
Air Exchange

The aim of this study was to design a fire ventilation system with impulse jet fans for an underground car park. With respect to the number of parameters affecting the spread of smoke that need to be considered, there is a good chance of miscalculations if only conventional plain calculations are used in the design process. To avoid mistakes, visualize the fluid flow, and to compare the design variants it is practical to use computational fluid dynamics (CFD). In this study, CFD simulations were used to compare alternative designs of a fire ventilation system. In one alternative the exhaust shafts were located in both parts of the car park and the jet fans were directed to the corresponding shafts. The air exchange rate was 10-times per hour. In another alternative both exhaust shafts were located on one side opposite to the main air supply, and the air exchange rate was 15-times per hour. The results showed preference of the second alternative, when the smoke was completely exhausted and the visibility improved substantially, whereas in the first alternative the car park was not sufficiently ventilated even 600 seconds after the fire had been put out. The results emphasize that proper location of elements of the ventilation system is crucial to attain high efficiency of fire ventilation.

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