Air Supply Outlet Research Articles

Modeling of positive pressure ventilation to prevent smoke spreading in sprinklered high-rise buildings

This paper analyzes the positive pressure ventilation to prevent the smoke from entering the stairwell using Large Eddy Simulation in a sprinklered high-rise building with the heat release rate of 1.5 MW. Two methods are compared to get a more effective way: (1) the pressurization air flow into the stairwell from the group of multiple air supply outlets, and (2) the group of 2 air supply outlets next to the fire floor. The results have shown that to prevent the smoke from entering the stairwell, the minimum pressurization air supply volume flow rates are less in the group of 2 air supply outlets than those in the group of multiple air supply outlets. When the pressurization fan is located on the top of the stairwell, based on the mass and energy conservation, a simple method is developed to predict the airflow mass flow rates at the outlets. Further, the correlation of the average pressure in the stairwell on the fire floor and the pressurization air supply volume flow rate is developed. The minimum pressurization air supply volume flow rate to obtain smoke free zone and maximum one to avoid the door being too heavy to open during evacuation can be estimated.

Design and Simulation of an Air Conditioning Project in a Hospital Based on Computational Fluid Dynamics

AbstractThis study aims to design a novel air cleaning facility which conforms to the current situation in China, and moreover can satisfy our demand on air purification under the condition of poor air quality, as well as discuss the development means of a prototype product. Air conditions in the operating room of a hospital were measured as the research subject of this study. First, a suitable turbulence model and boundary conditions were selected and computational fluid dynamics (CFD) software was used to simulate indoor air distribution. The analysis and comparison of the simulation results suggested that increasing the area of air supply outlets and the number of return air inlets would not only increase the area of unidirectional flow region in main flow region, but also avoid an indoor vortex and turbulivity of the operating area. Based on the summary of heat and humidity management methods, the system operation mode and relevant parameter technologies as well as the characteristics of the thermal-humidity load of the operating room were analyzed and compiled. According to the load value and parameters of indoor design obtained after our calculations, the airflow distribution of purifying the air-conditioning system in a clean operating room was designed and checked. The research results suggested that the application of a secondary return air system in the summer could reduce energy consumption and be consistent with the concept of primaiy humidity control. This study analyzed the feasibility and energy conservation properties of cleaning air-conditioning technology in operating rooms, proposed some solutions to the problem, and performed a feasible simulation, which provides a reference for practical engineering.

Effect of Stratum Ventilation on Thermal Comfort and Energy Utilization Efficiency of Numerical Simulation

Numerical simulation method was used to study the effects of the thermal comfort by air supply temperature and air supply outlet angle under of the mode of stratum ventilation in an office and the indoor thermal environment was evaluated by using the energy utilization coefficient index. The study indicated that, the PPD value indoor increased initially and then decreased with the increasing of the air supply outlet angle, and the maximum value was obtained when the air supply outlet angle was 90 degrees. The effect of air supply outlet angle and air supply temperature on energy utilization was smaller in the working condition of stratum ventilation, and the energy utilization coefficient were greater than 1 in different working conditions, which showed a certain energy saving effect existed.

Air Distribution Analysis and Design of Air Duct for B10 Railway Refrigerated Car

Aiming at the problems of the air flow of railway refrigerated transport equipment, the air distribution of the B10 railway refrigerated car was optimized. This paper find the best position of air supply outlet in the car, the main part of the outlet should be placed at the distance from the position of air return side 7300mm until the tail of the car. The research has been applied and the effect is good.

Experimental Research on the Temperature Distribution of Natural Displacement Ventilation in the Room under the Influence of Wind Pressure and Air Supply

Air pollution and building energy efficiency are two hot research contents at present. Based on the comfort, energy-saving and environmental protection characteristics of natural displacement ventilation, an experiment was been conducted to explore the influence of outdoor air pressure and different parameters of air supply outlet on indoor temperature distribution. The results showed that with the outside wind pressure increasing, thermal stratification height increases. When the outdoor air pressure exceeds 0.05625Pa, the indoor temperature fluctuations caused by side air supply was greater than the bottom, therefore, natural displacement ventilation with bottom air supply is better than with side air supply in the stability of temperature. When the outdoor air pressure exceeds 0.1Pa, the stratification disorder and even doesn’t exist. From the view of comfort and energy savings, the side air supply is better than the bottom.

Characterization of Potential Pathogenic Cladosporium Exposure Risks from Heating, Ventilation and Air Conditioning (HVAC) in Two Cities, China

Cladosporium is widespread in Heating, Ventilation and Air Conditioning (HVAC). Some species in which are responsible for the majority of fungal infections or allergy in humans. To assess the exposure risks of Cladosporium in HVAC to human health, the colony distribution, population constituent and pathogenic species identification of Cladosporium were investigated in current study. We selected two cities, Beijing and Nanjing, representing the North and South of China respectively, for the study. Three kinds of public places including hospitals, hotels and super markets were selected and 108 air samples from 18 sampling sites were collected from air supply outlets of HVAC in summer, 2012. The collecting plates were incubated at 28°C for 2-3 weeks. Purified fungal colonies were identified at the genus and species level based on morphological and DNA sequences. Internal transcribed spacer ITS1 and ITS2 region, partial gene sequences of the translation elongation facter1-α gene (EF-1α) and the actin gene (ACT) were used for phylogenetic analysis. Among all genera detected, Cladosporium was identified to have the widest prevalence (92.3%) from HVAC, which was detected from 100 of 108 air samples. 9 species of Cladosporium were identified viz. C. breviramosum, C. cladoporioides, C. cucumerinum, C. gossypiicola, C. macrocarpum, C. perangustum, C. sp., C. sphaerospermum and C. tenuissimum. Among of them, C. cladosporioides had the highest concentration and frequency, considered as predominant species in HVAC. There were three species, C. cladoporioides, C. sphaerospermum and C. macrocarpum, distributed as opportunistic pathogen to human reported before. The total frequency of the three species was 76.29% of this genus. What’s more, C. cladoporioides and C. sphaerospermum were detected in both cities with relatively high concentration and frequency. The frequency and prevalence rate in the South were higher than those in the North, suggesting that HVAC in the South was more susceptable to Cladosporium contamination.

Computational fluid dynamics (CFD) modelling of air flow field, mean age of air and CO2 distributions inside a bedroom with different heights of conditioned air supply outlet

It was revealed in a previous related study that for an air conditioning (A/C) system used in a sleeping environment, the height of its supply air outlet would significantly affect its ventilation performance in terms of effectiveness. To further examine the underlying reasons of the differences in ventilation performance, the air flow field, distributions of mean age of air, air change efficiency and distributions of CO2 concentrations inside an experimental bedroom were numerically studied using CFD method under five different settings, where its supply air outlet was positioned at 5 different heights. The study results suggested that positing a supply air outlet at a lower level was effective in both saving energy and removing the exhaled CO2 in a breathing zone, and when a supply outlet was positioned at a higher level, less CO2 was removed from the region near the mouth of a sleeper.

Thermal Comfort Analysis of a Ship Air-Conditioning System Using Solidworks Flow Simulation

The focus of this work is to simulate and optimize thermal comfort in a ship air-conditioning system by evaluating the performance of different types of air supply outlets. Thermal comfort analyses were performed in Solidworks Flow Simulation software by changing the number, type and position of air supply outlets and the comfort was optimized by evaluating the values of temperature, velocity, PMV (Predicted mean vote) & PPD (Predicted Percentage Dissatisfied). It was concluded from the results obtained from different analyses that air supply outlet is a vital part in any type of HVAC (Heating ventilation & air conditioning) system design, as its number, type and position has significant effect on the air distribution and thermal comfort in a subject space. It was also deduced that improper selection of air supply outlet can result in room air stagnation, unacceptable temperature gradients, and undesirable velocities in the occupied zone that may lead to occupant discomfort. Through this work the importance and effectiveness of CFD (computational fluid dynamics) design tools, in the design & optimization of HVAC systems has been evaluated and it was concluded that CFD design software like Solidworks flow simulation provide an excellent provision to validate different aspects of HVAC design before actual construction.

Analysis of anti-condensation mechanism on superhydrophobic anodic aluminum oxide surface

Wetting theory about superhydrophobic surfaces reveals that hydrophobicity of surfaces has great relationship with surface roughness and surface free energy. Adopt electrochemical plus fluorine silane modified method to prepare superhydrophobic surface on anodic aluminum oxide surface, which not only enhances surface roughness, but also reduces surface free energy, even the static contact angle can reach 159.2° and anti-condensation is authenticated. Based on the experimental findings, analyze the reason of anti-condensation on superhydrophobic surfaces: one is that the density of droplets formed on superhydrophobic surfaces is low and the number of droplets is little; the other is bigger static contact angle and smaller rolling angle on superhydrophobic surfaces make droplets easy to detach on smaller tilt angle. This research can solve some condensation problems of equipment using in HVAC systems, such as heat exchangers in air conditioning system, cold radiation boards, air supply outlets, and so on.

Analysis of the Solar Wall Heat Transfer and Energy Saving of Residential Ventilation

It is the considerable measure that adopting the ventilation solar wall to make up the indoor air in winter because this method embodies the effective use of renewable energy. This paper analyzes the needed volume of make-up air in the different conditions of indoor air exhaust in winter and builds a solar wall to heat the make-up air. Under the conditions of different solar wall size of air channel thickness and so on, Conclusions can be simulated by using CFD software. When the optimum cavity width B is 50mm, the height of air supply outlet D is 30mm and the volume of make-up air is 200 m3/h,the maximum temperature rise of the air rises to 24°C.But when the volume of make-up air is 600 m3/h, there has the best energy-saving effect.

A three-dimensional microfluidic approach to scaling up microencapsulation of cells

Current applications of the microencapsulation technique include the use of encapsulated islet cells to treat Type 1 diabetes, and encapsulated hepatocytes for providing temporary but adequate metabolic support to allow spontaneous liver regeneration, or as a bridge to liver transplantation for patients with chronic liver disease. Also, microcapsules can be used for controlled delivery of therapeutic drugs. The two most widely used devices for microencapsulation are the air-syringe pump droplet generator and the electrostatic bead generator, each of which is fitted with a single needle through which droplets of cells suspended in alginate solution are produced and cross-linked into microbeads. A major drawback in the design of these instruments is that they are incapable of producing sufficient numbers of microcapsules in a short-time period to permit mass production of encapsulated and viable cells for transplantation in large animals and humans. We present in this paper a microfluidic approach to scaling up cell and protein encapsulations. The microfluidic chip consists of a 3D air supply and multi-nozzle outlet for microcapsule generation. It has one alginate inlet and one compressed air intlet. The outlet has 8 nozzles, each having 380 micrometers inner diameter, which produce hydrogel microspheres ranging from 500 to 700 μm in diameter. These nozzles are concentrically surrounded by air nozzles with 2 mm inner diameter. There are two tubes connected at the top to allow the air to escape as the alginate solution fills up the chamber. A variable flow pump 115 V is used to pump alginate solution and Tygon® tubing is used to connect in-house air supply to the air channel and peristaltic/syringe pump to the alginate chamber. A pressure regulator is used to control the flow rate of air. We have encapsulated islets and proteins with this high throughput device, which is expected to improve product quality control in microencapsulation of cells, and hence the outcome of their transplantation.

Model Experimental Study on Stratified Air Distribution with 2D-PIV for High Ceiling Industrial Plant

At present, the research ways of stratified air-conditioning technology mainly have two types, experimental study and numerical simulation. In this paper, a transparent Plexiglas model was designed, of which the size was supposed to be 1/50 of the real scale. PIV technology was innovatively applied into the experiment to measure the air distribution of an industrial plant. Different air supply velocities and different kinds of air supply outlets were taken into account to discuss the influence of them. Results revealed that as the jet velocity increased gradually, the airflow’s stratification effect became more evident. When the aspect ratio changed from 1:2 to 1:8, the diffusion degree in vertical direction increased obviously. In comparison with the rectangular air supply outlet, the circular one had lower decay, longer jet distance and better contractibility. The experimental findings are useful for optimizing the design of air distribution in high ceiling industrial plant.

Wellhead anti-frost technology using deep mine geothermal energy

The auxiliary shaft is an important location for coal mine heating in the winter, where the main purpose of heating is to prevent icing of the shaft. Wellhead heating requires characteristics of openness, no-noise and big heat loads. The original coal-fired boiler heating mode causes significant waste of energy and environmental pollution due to the low efficiency of the heat exchange. Therefore, to solve these problems, we will use deep mine geothermal energy to heat the wellhead by making full use of its negative pressure field and design a low-temperature water and fan-free heating system. Through numerical calculations we will simulate temperature fields, pressure fields and velocity fields under different air supply temperatures, as well as different air supply outlet locations and varying number of radiators in the wellhead room of a new auxiliary shaft to find the proper layout and number of radiators that meet wellhead anti-frost requirements from our simulation results, in order to provide guidelines for a practical engineering design. Tests on the Zhangshuanglou auxiliary shaft wellhead shows good, look promising and appear to resolve successfully the problem of high energy consumption and high pollution of wellhead heating by a coal-fired boiler.

Simulation and Optimization of Indoor Thermal Environment in a Ship Air-conditioning System

Abstract Crew's health and productivity is strongly affected by cabins’ thermal environment. This paper focuses on the numerical simulation of the indoor thermal environment in air-conditioned vessel cabins. The original airconditioning system of the cabin was analyzed. Three modified air-conditioning systems with different air-supply outlet locations and under-supply air-conditioning system were put forward for optimization. Air temperature, air velocity and PMV distribution were discussed under Airpak simulation. The results show that under-supply airconditioning system has good performance with little eddies and can contribute to energy saving. Indoor air temperature with under-supply air-conditioning system was 2∼4 lower than that °C with original air-conditioning system, leading to lower predicted mean vote (PMV).

Investigation of transient thermal environments

Human beings are commonly exposed to transient thermal environments in their daily life. But most of the studies on indoor thermal environment have been conducted under steady-state conditions. The aim of this paper is to summarize the investigation on human responses to transient thermal environment carried out by the indoor environment group at Tsinghua University, and to predict the possibility of using their research findings in practice. Human responses to transients have some special characteristics, which could be beneficial to environmental control. Air movement is especially effective at realizing a transient thermal environment, offsetting higher air temperature or operative temperature in warm climates. Based on the analysis of measured data, the characteristics of air movement outdoors are different from artificial air supply such as fans or air supply outlets, in the probability distribution of their velocities, turbulence intensity, and power spectrum. Based on subjective experiments, it is evident that artificial air movement, which is mainly simulated with outdoor airflow characteristics, has the highest occupant preference in warm conditions. Experimentally simulated air movement improves not only whole-body cooling, but also local cooling as from personal air supplies. Finally, it is important that introducing simulated natural air movement into the space in warm or hot conditions could significantly decrease the building's energy consumption.

Study on dynamic characteristics of natural and mechanical wind in built environment using spectral analysis

What are the differences and similarities between natural and mechanical wind in built environment? This is an interesting question that has not been well answered yet. In the paper, spectral analysis is applied to study the dynamic characteristics of natural and mechanical wind in different conditions. The results show that in the frequency region sensitive to human sensation, the power spectrum characteristics of natural wind and mechanical wind have obvious differences as well as interesting connections. The power spectrum exponent ( β value) of natural wind is between 1.1 and 2.0 in the human sensitive frequency region, while the value of mechanical wind is between 0 and 0.5 around the air supply outlet. With the diffusion of mechanical wind, β value will increase gradually and reach the value of the typical natural wind when the mean velocity is lower than 0.25 m/s. Finally, the influence of spectral characteristics on human sensation for airflow is discussed.

温風暖房空間の上下温度分布の簡易計算モデル : 空調空間の熱的特性に関する研究 第2報

In this paper we describe a simplified calculation model of vertical air temperature distribution during heating in the air-conditioned room, where air supply outlets are installed in the ceiling or the high sidewall and air return intake is installed in the low sidewall. The basic equations for the calculation are derived from a mixing process model of the room air, which is divided into complete mixing region at the upper side of the room and piston flow region at the lower side of one. It is assumed that in the former the discharged warm air is mixed with the room air completely, while in the latter the room air moves downward to the floor and its temperature gradient is formed only in the vertical direction of the room. Regression equations were derived from many experimental results for stepwise inputs of warmed air at the simulated full-scale office room. The equations give relation between the model parameter defined as a ratio of depth of the complete mixing region to the room height and Archimedes number which is induced from the supply air condition.