Implementation of demand-oriented ventilation with adjustable fan network

2020 ◽  
Vol 29 (4) ◽  
pp. 621-635 ◽  
Author(s):  
Huan Wang ◽  
Guijin Wang ◽  
Xianting Li
Keyword(s):  
Indoor Environment ◽  
Ventilation System ◽  
Test Chamber ◽  
Hvac Systems ◽  
The Novel ◽  
Airflow Pattern ◽  
Colour Sequence ◽  
Axial Fans ◽  
Particle Streak Velocimetry ◽  
Occupied Zone

Airflow patterns are essential for heating, ventilation and air conditioning (HVAC) systems. Traditional HVAC systems are predesigned and operated using a fixed airflow pattern. However, the indoor occupancy and heat source always vary and therefore, the fixed flow pattern cannot efficiently maintain the required indoor environment conditions. In this study, a novel Adjustable Fan Network (AFN) for improving airflow pattern manoeuvrability is proposed. It integrates multiple small and adjustable axial fans into an AFN, enabling it to change the airflow pattern based on the actual demand with only one set of equipment. Further, the outflow characteristics of two types of axial fans were measured using a quad-view colour sequence particle streak velocimetry (CSPSV) in a test chamber. The ventilation system was then designed based on typical scenarios. Finally, the performance of the AFN was evaluated under different scenarios using a quad-view CSPSV. Based on the results, it was evident that the AFN can provide a better direct supply of air to the occupied zone under different scenarios. With the growing demand for personal thermal comfort and energy-saving in HVAC systems, the novel AFN system has a great potential to be a highly controllable terminal for demand-oriented ventilation.

scholarly journals Measurement of airflow pattern induced by ceiling fan with quad-view colour sequence particle streak velocimetry

2019 ◽  
Vol 152 ◽  
pp. 122-134 ◽  
Author(s):  
Huan Wang ◽  
Hong Zhang ◽  
Xiaowei Hu ◽  
Maohui Luo ◽  
Guijin Wang ◽  
...  
Keyword(s):  
Airflow Pattern ◽  
Colour Sequence ◽  
Particle Streak Velocimetry

Airflow pattern induced by ceiling fan under different rotation speeds and blowing directions

2019 ◽  
Vol 29 (10) ◽  
pp. 1425-1440 ◽  
Author(s):  
Huan Wang ◽  
Maohui Luo ◽  
Guijin Wang ◽  
Xianting Li
Keyword(s):  
New Technology ◽  
Three Dimensional ◽  
Air Conditioning System ◽  
Airflow Pattern ◽  
Room Size ◽  
Colour Sequence ◽  
Air Mixing ◽  
Particle Streak Velocimetry ◽  
Air Speed ◽  
Velocity Turbulence

Ceiling fans have been widely used as effective cooling and air mixing method for building environment conditioning. Understanding its airflow characteristics can be helpful to utilize ceiling fan or integrate it with background air conditioning system. However, the airflow induced by ceiling fan has different flow patterns under different rotating speeds and blowing directions. To date, it is still challenging to capture those complicated airflow fields in room scale. In this study, the airflow pattern induced by a ceiling fan was measured with a new technology, quad-view colour sequence particle streak velocimetry. A series of isothermal experiments were conducted under five rotation speed levels with downward and upward blowing directions in a room-size (4 m × 2.5 m × 3 m) chamber. Based on comprehensive three-dimensional three-component vector measurement results, the average velocity, turbulence intensity and vorticity on the middle section were calculated and used to analyse airflow patterns induced by ceiling fan. The results show that the blowing direction of the fan determines the indoor airflow pattern. When blowing downward, the flow will cause high diversion between jet core under the fan blades and surrounding region. While for upward blowing, the air speed in lower part of the room is much lower but pretty uniform. The detailed measured airflow fields can serve as reference for ceiling fan design and operation.

scholarly journals Barriers on Establishing Passive Strategies in Office Spaces: A Case Study in a Historic University Building

2021 ◽  
Vol 13 (8) ◽  
pp. 4563
Author(s):  
Nuno Baía Baía Saraiva ◽  
Luisa Dias Dias Pereira ◽  
Adélio Rodrigues Gaspar ◽  
José Joaquim da Costa
Keyword(s):  
Thermal Comfort ◽  
Indoor Environment ◽  
Hvac Systems ◽  
Heritage Buildings ◽  
Full Capacity ◽  
Free Cooling ◽  
Passive Strategies ◽  
The University ◽  
Indoor Conditions

The adaptation of spaces to different usage typologies can be complex in heritage buildings. Facilities were initially planned for a specific type of use that, when changed, require additional measures to ensure a suitable indoor environment. Passive strategies—e.g., free cooling—are commonly used as an alternative without requiring equipment installation. However, its implementation often leads to unsatisfactory conditions. Therefore, it is important to clarify the main barriers to achieving thermal comfort in readapted historic buildings. The present work investigates the thermal comfort conditions reported by workers in office spaces of a historic building in the University of Coimbra. A monitoring campaign was carried out between May and September 2020 to assess indoor conditions’ quality. Due to the current pandemic of COVID-19, offices were not occupied at full capacity. A one-day evaluation of thermal comfort was made using a climate analyzer and six occupants were surveyed on 19 August 2020. The main results highlighted discomfort due to overheating of spaces. The causes were related to the combination of inadequate implementation of the free cooling actions and the building use. Furthermore, it was recommended the installation of HVAC systems in case of full capacity.

Computational Modeling of Particulate Pollutant Transport in a Ventilated Room in the Presence of Two Heated Breathing and Rotating Manikins

2017 ◽  
Author(s):  
Seyed Ali Keshavarz ◽  
Mazyar Salmanzadeh ◽  
Goodarz Ahmadi
Keyword(s):  
Air Quality ◽  
Computational Modeling ◽  
Indoor Air Quality ◽  
Indoor Air ◽  
Rotational Motion ◽  
Indoor Environment ◽  
Ventilation System ◽  
Thermal Plume ◽  
Displacement Ventilation ◽  
Simulation Results

Recently, attention has been given to indoor air quality due to its serious health concerns. Clearly the dispersion of pollutant is directly affected by the airflow patterns. The airflow in indoor environment is the results of a combination of several factors. In the present study, the effects of thermal plume and respiration on the indoor air quality in a ventilated cubicle were investigated using an unsteady computational modeling approach. The person-to-person contaminant transports in a ventilated room with mixing and displacement ventilation systems were studied. The effects of rotational motion of the heated manikins were also analyzed. Simulation results showed that in the cases which rotational motion was included, the human thermal plume and associated particle transport were significantly distorted. The distortion was more noticeable for the displacement ventilation system. Also it was found that the displacement ventilation system lowered the risk of person-to-person transmission in an office space in comparison with the mixing ventilation system. On the other hand the mixing system was shown to be more effective compared to the displacement ventilation in removing the particles and pollutant that entered the room through the inlet air diffuser.

scholarly journals Impact of high residential density on the building technology, HVAC systems, and indoor environment in Swedish apartments

2020 ◽  
Vol 172 ◽  
pp. 09003 ◽  
Author(s):  
Akram Abdul Hamid ◽  
Jenny von Platten ◽  
Kristina Mjörnell ◽  
Dennis Johansson ◽  
Hans Bagge
Keyword(s):  
Indoor Environment ◽  
Ventilation Rate ◽  
Hvac Systems ◽  
Extreme Conditions ◽  
Residential Density ◽  
Indoor Climate ◽  
Housing Shortage ◽  
Technical Parameters ◽  
Building Technology ◽  
Combat Problems

During the last few years, there has been an increased number of overcrowded apartments, due to increased migration but also housing shortage in general, particularly in the suburbs to major cities. The question is how the indoor environment in these apartments is affected by the high number of persons and how the problems related to high residential density can be overcome. This paper aims to specify the problem by investigating and analysing the technical parameters influenced by residential density in Swedish apartments built between 1965-1974. To map the situation, 11 interviews with employees at housing companies were conducted. Based on extreme conditions described in the interviews, simulations of the indoor climate and moisture risks at some vulnerable parts of constructions were made. Simulations were focused on moisture loads and CO2 concentrations as functions of residential density and ventilation rate. Finally, measures to combat problems associated to overcrowding are suggested. The aim is that the results should be used by authorities to formulate incentives and/or recommendations for housing companies to take actions to ensure a good indoor environment for all, irrespective of residential density conditions.

Efficiency of Natural Ventilation in Central Greenhouse of Botanical Garden in Kosice

2017 ◽  
Author(s):  
Martin Kovac ◽  
Katarina Kovacova ◽  
Anna Sedlakova
Keyword(s):  
Indoor Environment ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Botanical Garden ◽  
Simulation Tool ◽  
Summer Period ◽  
Radiation Level ◽  
Glass Panels ◽  
The Right ◽  
Calculated Model

The object of paper is analysis of natural ventilation system in central greenhouse of Botanical garden in Kosice. The greenhouse was refurbished in 2015. The existing greenhouse covering from glass panels was replaced for polycarbonate panels. The ventilation system of central greenhouse is natural and there are used openings in covering (wall, roof). It is combination of thermally and wind driven ventilation. The main aim of contribution is to analyse different modes of natural ventilation during summer period mainly. The important factors that influence efficiency of natural ventilation in greenhouse are location and area of openings, temperature stratification in greenhouse, solar radiation level, wind speed and direction too. If the greenhouse is ventilated naturally only through external windows (roof windows are closed) the efficiency of ventilation is very poor. The defined modes of natural ventilation search the right location and size of opened windows in order to achieve the most efficiency ventilation of indoor environment. For this purpose the progressive dynamic simulation tool DesignBuilder is used where the geometrical and specific calculated model of whole central greenhouse was created.

Numerical Assessment of Fan-Ducting Coupling for Gas Turbine Ventilation Systems

2015 ◽  
Author(s):  
Alessandro Corsini ◽  
Giovanni Delibra ◽  
Stefano Minotti ◽  
Stefano Rossin
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Static Pressure ◽  
Numerical Study ◽  
Characteristic Curve ◽  
Ventilation System ◽  
Maximum Pressure ◽  
Term Operation ◽  
Axial Fans ◽  
Pressure Discontinuity

Gas turbines enclosures entail a high number of auxiliary systems which must be preserved from heat, ensuring therefore the long term operation of the internal instrumentation and of the data acquisition system. A dedicated ventilation system is designed to keep the enclosure environment sufficiently cool and dilute any gas coming from potential internal leakage to limiting explosion risks. These systems are equipped with axial fans, usually fed with air coming from the filter house which provides air to the gas turbine combustion system, through dedicated filters. The axial fans are embedded in a ducting system which discharges fresh air inside the enclosure where the gas turbine is housed. As the operations of the gas turbine need to be guaranteed in the event of fan failure, a backup redundant system is located in a duct parallel to the main one. One of the main requirements of a ventilation fan is the reliability over the years as the gas turbine can be installed in remote areas or unmanned offshore platforms with limited accessibility for unplanned maintenance. For such reasons, the robustness of the ventilation system and a proper understanding of coupling phenomena with the axial fan is a key aspect to be addressed when designing a gas-turbine system. Here a numerical study of a ventilation system carried out with RANS and LES based methodologies will be presented where the presence of the fan is synthetized by means of static pressure discontinuity. Different operations of the fans are investigated by means of RANS in order to compare the different operating points, corresponding to 1) clean and 2) dirty filters operations, 3) minimum and 4) maximum pressure at the discharge section. Large Eddy Simulations of the same duct were carried out in the maximum loading condition for the fan to investigate the unsteady response of the system and validate its correct arrangement. All the simulations were carried out using OpenFOAM, a finite volume open source code for CFD analysis, treating the filters as a porous medium and the fan as a static pressure discontinuity according to the manufacturer’s characteristic curve. RANS modelling was based on the cubic k-ε model of Lien et al. while sub-grid scale modelling in LES was based on the 1 equation model of Davidson. Computations highlighted that the ventilation system was able to work in similarity for flow rates between 15 m3/s and 23.2 m3/s and that the flow conditions onto the fan suggest that the aerodynamic stress on the device could be reduced introducing in the duct flow straighteners or inlet guided vanes.

scholarly journals House owners’ experience and satisfaction with Danish low-energy houses - focus on ventilation

2019 ◽  
Vol 111 ◽  
pp. 04006
Author(s):  
Henrik N. Knudsen
Keyword(s):  
Energy Consumption ◽  
Air Quality ◽  
High Performance ◽  
Indoor Environment ◽  
Ventilation System ◽  
Low Energy ◽  
Energy Class ◽  
Single Family ◽  
Environment Temperature ◽  
Low Energy Consumption

The purpose of this study was to evaluate house owners’ experience and satisfaction with the first Danish detached low-energy single-family houses, built according to energy class 2015 before these supplementary requirements became standard for all new dwellings. A questionnaire survey was carried out among owners of newly built energy class 2015 houses. The paper presents the house owners answers to questions on their overall satisfaction, their heat consumption, and their satisfaction with the indoor environment (temperature, draught, air quality, noise and daylight). There is a focus on issues related to having a mechanical ventilation system, i.e. satisfaction with the air quality, does the air feel dry in winter, and does the ventilation system make noise and how the airing behaviour is in winter. As many as 370 out of 869 house owners, corresponding to a response rate of 43%, answered the questionnaire. There was an overall satisfaction with the new low-energy houses. More than 90% of the house owners perceived the indoor environment as satisfactory. The energy consumption was as low as expected by 59%, while only 7% answered that it was higher than expected. Compared with previous similar studies, problems with technical installations have decreased. However, there is a need for continued focus on the commissioning of new and not necessarily thoroughly tested, high-performance installations and new designs. Based on the survey a series of recommendations are given that might help to achieve both a low energy consumption and satisfied occupants of new low-energy dwellings.

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