An analytical study to evaluate the impact of distributed zone fans on the air flow rate in a mechanical ventilation system

2019 ◽  
Vol 41 (4) ◽  
pp. 507-516
Author(s):  
Fa-Li Ju ◽  
Liying Liu ◽  
Xiaoping Yu
Keyword(s):  
Mechanical Ventilation ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Ventilation System ◽  
Theoretical Expression ◽  
Air Flow Rate ◽  
Rate Testing ◽  
Fan Speed ◽  
The Impact

Based on air flow rate testing of each branch fan in a distributed fan ventilation system under different branch air duct inlet static pressures, the conclusion can be drawn that there is a branch fan air flow rate deviation phenomenon. The air flow rate of the branch fan increases with the branch air duct inlet static pressure at the same branch fan speed, and the branch fan hinders the air flow rate in some cases. In this study, a theoretical expression of the deviation of the branch air duct design air flow rate was established, and the influencing factors of the deviation were determined to include the branch air duct resistance characteristics, branch fan performance, and branch air duct inlet pressure ratio. A graphic analytical method for determining the deviation of the branch fan design air flow rate was also proposed. Both methods can provide a theoretical basis for calculating and analysing the deviation of the branch fan design air flow rate in a distributed fan ventilation system. Practical application: This paper provides new data on the performance of a distributed fan ventilation system. Our results could be used to evaluate the impact of distributed zone fans on the air flow rate in a mechanical ventilation system. Crucially, we not only propose two types of methods that can be applied to predict deviations of the air flow rate in a distributed fan ventilation system caused by the branch air duct inlet static pressures but also obtain the factors that are important for understanding the true impact of the deviation of the branch fan air flow rate. This study lays an important foundation for the design and operation of building mechanical ventilation systems.

Test and analysis of air flow rate adaptive performance in a distributed fan ventilation system

2021 ◽  
pp. 014362442098600
Author(s):  
Fa-Li Ju ◽  
Qinrong Sun ◽  
Changlei Hou ◽  
Xue Huang ◽  
Xiaoping Yu ◽  
...  
Keyword(s):  
Mechanical Ventilation ◽  
Engineering Design ◽  
Flow Rate ◽  
Air Flow ◽  
Ventilation System ◽  
Adaptive Performance ◽  
Air Flow Rate ◽  
Branch Duct ◽  
Rate Adaptive ◽  
Adaptive Ability

In this study, adaptive branch fan performance in a distributed fan ventilation system was tested. The results demonstrate that the adaptive branch fan stabilises the branch air flow rate within a certain air pressure range corresponding to the branch duct inlet, and this range becomes increasingly narrow as the fan control signal is adjusted to reduce the speed of the fan. The adaptive branch fan is less affected by the main fan and other branch fans in the distributed fan ventilation system because it has a good self-adaptive ability of ventilation duct resistance characteristics and anti-interference ability of the air flow rate. Furthermore, the hydraulic characteristics of the branch fans in the distributed fan ventilation system were analysed. The new performance characterisation parameters and method for modifying the engineering design for the adaptive branch fan were presented. Practical application: This study investigates the adaptive performance of the branch fan in a distributed fan ventilation system. Our results demonstrate that the new branch fan can stabilise the air flow rate in a mechanical ventilation system. More importantly, we not only propose performance characterisation parameters of the adaptive branch fan that are important for understanding the operation of a mechanical ventilation system, but also present a method of engineering design application. This study can guide the design and operation of mechanical ventilation systems.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

scholarly journals Experimental Study and Performance Analysis of a Portable Atmospheric Water Generator

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 73 ◽  
Author(s):  
Wei He ◽  
Pengkun Yu ◽  
Zhongting Hu ◽  
Song Lv ◽  
Minghui Qin ◽  
...  
Keyword(s):  
Flow Rate ◽  
Reference Model ◽  
Air Flow ◽  
Operating Conditions ◽  
Water Yield ◽  
Air Humidity ◽  
Air Flow Rate ◽  
Thermoelectric Coolers ◽  
And Performance ◽  
The Impact

Found in some specific scenarios, drinking water is hard for people to get, such as during expeditions and scientific investigations. First, a novel water generator with only two thermoelectric coolers (Model A) is designed for extracting water from atmospheric vapor and then experimentally studied under a small inlet air flow rate. The impact of operating conditions on surface temperatures of cold/hot sides and water yield are investigated, including the air flow rate and humidity. Alternately, to determine the super performance of Model A, a comparative experiment between Model A and a reference model (Model B) is carried out. The results suggest that both the cold/hot temperature and water yield in Model A increases with the humidity and air flow rate rising. Seen in comparisons of Model A and Model B, it is found that, at an air humidity of 90% and air flow rate of 30 m3/h, the total water yield was increased by 43.4% and the corresponding value reached the maximum increment of 66.7% at an air humidity of 60% and air flow rate of 30 m3/h. These features demonstrate the advantage of Model A especially in low air humidity compared to Model B.

Prediction of alpha factor values for fine pore aeration systems

2008 ◽  
Vol 57 (8) ◽  
pp. 1265-1269 ◽  
Author(s):  
S. Gillot ◽  
A. Héduit
Keyword(s):  
Flow Rate ◽  
Oxygen Transfer ◽  
Air Flow ◽  
Domestic Wastewater ◽  
Aeration Tank ◽  
Air Flow Rate ◽  
Factors Affecting ◽  
Domestic Wastewater Treatment ◽  
Alpha Factor ◽  
The Impact

The objective of this work was to analyse the impact of different geometric and operating parameters on the alpha factor value for fine bubble aeration systems equipped with EPDM membrane diffusers. Measurements have been performed on nitrifying plants operating under extended aeration and treating mainly domestic wastewater. Measurements performed on 14 nitrifying plants showed that, for domestic wastewater treatment under very low F/M ratios, the alpha factor is comprised between 0.44 and 0.98. A new composite variable (the Equivalent Contact Time, ECT) has been defined and makes it possible for a given aeration tank, knowing the MCRT, the clean water oxygen transfer coefficient and the supplied air flow rate, to predict the alpha factor value. ECT combines the effect on mass transfer of all generally accepted factors affecting oxygen transfer performances (air flow rate, diffuser submergence, horizontal flow).

Measurement of Air Flow Rate Sensitivity to the Differential Pressure Across a Server Rack in a Data Center

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Vaibhav K. Arghode ◽  
Yogendra Joshi
Keyword(s):  
Flow Rate ◽  
Data Center ◽  
Air Flow ◽  
Rate Sensitivity ◽  
Differential Pressure ◽  
Air Cooling ◽  
Air Flow Rate ◽  
Hot Air ◽  
Fan Speed ◽  
Measured Sensitivity

Presently, air cooling is the most common method of thermal management in data centers. In a data center, multiple servers are housed in a rack, and the racks are arranged in rows to allow cold air entry from the front (cold aisle) and hot air exit from the back (hot aisle), in what is referred as hot-aisle-cold-aisle (HACA) arrangement. If the racks are kept in an open room space, the differential pressure between the front and back of the rack is zero. However, this may not be true for some scenarios, such as, in the case of cold aisle containment, where the cold aisle is physically separated from the hot data center room space to minimize cold and hot air mixing. For an under-provisioned case (total supplied tile air flow rate < total rack air flow rate) the pressure in the cold aisle (front of the rack) will be lower than the data center room space (back of the rack). For this case, the rack air flow rate will be lower than the case without the containment. In this paper, we will present a methodology to measure the rack air flow rate sensitivity to differential pressure across the rack. Here, we use perforated covers at the back of the racks, which results in higher back pressure (and lower rack air flow rate) and the corresponding sensitivity of rack air flow rate to the differential pressure is obtained. The influence of variation and nonuniformity in the server fan speed is investigated, and it is observed that with consideration of fan laws, one can obtain results for different average fan speeds with reasonable accuracy. The measured sensitivity can be used to determine the rack air flow rate with variation in the cold aisle pressure, which can then be used as a boundary condition in computational fluid dynamics (CFD)/rapid models for data center air flow modeling. The measured sensitivity can also be used to determine the change in rack air flow rate with the use of different types of front/back perforated doors at the rack. Here, the rack air flow rate is measured using an array of thermal anemometers, pressure is measured using a micromanometer, and the fan speed is measured using an optical tachometer.

scholarly journals Active Disturbance Rejection Control of a Longitudinal Tunnel Ventilation System

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1871
Author(s):  
Liyun Si ◽  
Wenping Cao ◽  
Xiangping Chen
Keyword(s):  
Flow Rate ◽  
Disturbance Rejection ◽  
Air Flow ◽  
Ventilation System ◽  
Active Disturbance Rejection Control ◽  
Air Flow Rate ◽  
Long Distance ◽  
Tunnel Ventilation ◽  
Active Disturbance Rejection ◽  
Disturbance Rejection Control

This paper proposes an innovative approach for controlling pollutant release in a long-distance tunnel via longitudinal ventilation. Enhanced by an active disturbance rejection control (ADRC) method, a ventilation controller is developed to regulate the forced air ventilation in a road tunnel. As a result, the pollutants (particulate matter and carbon monoxide) are reduced by actively regulating the air flow rate through the tunnel. The key contribution of this study lies in the development of an extended state observer that can track the system disturbance and provide the system with compensation via a nonlinear state feedback controller equipped by the ADRC. The proposed method enhances the disturbance attenuation capability in the ventilation system and keeps the pollutant concentration within the legitimate limit in the tunnel. In addition to providing a safe and clean environment for passengers, the improved tunnel ventilation can also achieve better energy saving as the air flow rate is optimized.

scholarly journals Alleviating Aural Discomfort of Passengers on Shinkansen by Controlling Air Flow Rate in Ventilation System.

1997 ◽  
Vol 63 (614) ◽  
pp. 3294-3301
Author(s):  
Minoru KOBAYASHI ◽  
Yasufumi SUZUKI ◽  
Katsunori AKUTSU ◽  
Satoru OZAWA
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Ventilation System ◽  
Air Flow Rate

The Impact of Air Flow Rate on Photobioreactor Sparger/Diffuser Bubble Size(s) and Distribution

2013 ◽  
Author(s):  
Anil R. Kommareddy ◽  
Gary A. Anderson ◽  
Stephen P. Gent ◽  
Ghazi S. Bari
Keyword(s):  
Flow Rate ◽  
Bubble Size ◽  
Air Flow ◽  
Air Flow Rate ◽  
The Impact

scholarly journals Pengaruh Kecepatan Fluida Pendingin (Udara) Terhadap Unjuk Kerja Dan Karakteristik Perpindahan Panas Pada Radiator Sepeda Motor Yamaha Nmax 155CC

2021 ◽  
Vol 14 (2) ◽  
pp. 106-111
Author(s):  
Ridho Syahrul ◽  
Amnur Akhyan
Keyword(s):  
Flow Rate ◽  
Air Flow ◽  
Water Flow Rate ◽  
Fluid Temperature ◽  
Air Flow Rate ◽  
Flat Tube ◽  
A Value ◽  
Fan Speed ◽  
Air Flow Velocity ◽  
Louvered Fins

Penelitian ini menggunakan metode ɛ-NTU untuk menganalisis data. Radiator yang digunakan adalah radiator sepeda motor Yamaha Nmax 155cc dengan jenis aliran vertical, flat tube dan louvered fins, kipas/fan sebagai sumber angin simulasi, dengan campuran 50% air + 50% coolant radiator. Laju aliran air konstan 4 lpm dan temperatur fluida panas konstan 80. Variasi kecepatan aliran udara yang digunakan pada pengujian kali ini adalah 4-8 m/s dan diatur menggunakan Dimmer sebagai alat bantu. Dari pengujian yang telah dilakukan didapat laju massa aliran udara yang paling besar terjadi pada kecepatan kipas 8 m/s. Laju perpindahan panas yang paling besar terjadi dikecepatan kipas 8 m/s sebesar 0,0735 kW dan panas menyeluruh terbesar juga terjadi dikecepatan kipas 8 m/s yaitu sebesar 9,50 W/m2°C. Efisiensi radiator maksimum terjadi pada kecepatan kipas 5 m/s dengan nilai sebesar 7,59. Kata kunci: Efektifitas, Metode ε-NTU, Radiator Nmax 155cc. This study uses the ε-NTU method to analyze the data. The radiator used is a 155cc Yamaha Nmax motorcycle radiator with vertical flow type, flat tube and louvered fins, fan/fan as a simulation source, with a mixture of 50% water + 50% coolant radiator. The water flow rate is constant 4 lpm and the hot fluid temperature is constant 80℃. The variation of air flow velocity used in this test is 4-8 m/s and is adjusted using a dimmer as a tool. From the tests that have been carried out, the largest air flow rate occurs at a fan speed of 8 m/s. The highest heat transfer rate occurs at a fan speed of 8 m/s at 0.0735 kW and the largest overall heat also occurs at a fan speed of 8 m/s at 9.50 W/m2°C. The maximum radiator efficiency occurs at a fan speed of 5 m/s with a value of 7.59 Keywords: Effectivenes, ɛ-NTU Method, Nmax 155cc Radiator

scholarly journals Optimization of the ventilation scheme for increasing production capacity of underground mines

2022 ◽  
pp. 89-93
Author(s):  
N.D. Iliinov ◽  
A.M. Mazhitov ◽  
A.B. Allaberdin ◽  
K.V. Vazhdaev
Keyword(s):  
Flow Rate ◽  
Underground Mining ◽  
Critical Path ◽  
Air Flow ◽  
Ventilation System ◽  
Production Capacity ◽  
Underground Mines ◽  
Air Flow Rate ◽  
Mining Operations ◽  
Mine Workings

Currently, many underground mines are revising their design solutions to increase their production capacity. This tendency is explained by the decreasing ore grades, as well as by the extensive introduction of mechanization in underground mining operations that has improved the output of mobile equipment by increasing the box capacity and engine power. Dieselpowered mobile vehicles are the most common in underground mining practice. The advantages of such engines are obvious as they generate more power than other types of engines. However, the high air demand for mine ventilation limits their application. This is associated with the need to increase the cross-sections of permanent mine workings in order to comply with the standard air flow rate with account of the increased ventilation capacity along with an increase in the inventory of mobile equipment in order to ensure the specified output of the mine. The specific features of mining operations are defined by the stage-wise character of commissioning various blocks of the deposit. Managing of production and development works provides an opportunity to ventilate the mine sections due to their consecutive commissioning, locally, with an isolated stream of air by means of mine workings that do not have the intersection of air streams. This provides a reduction of critical path of air travel up to 30% and reduction of the general mine ventilating pressure drop by at least 20% at constant air flow rate. The results of the work can be used in designing the ventilation system of underground mines both under construction and in operation.

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