Transcript
2016 International Conference on Energy Development and Environmental Protection (EDEP 2016) ISBN: 978-1-60595-360-1
Design of Indoor PM2.5 Controlling Ventilation Window Based on Multiple Layers Filtration System Xuan-Ren LONGa, Tao WENb,*, Wei-Jie GUc, Xiu-Li LINd School of Resource and Civil Engineering, Northeastern University, China a
[email protected],
[email protected],
[email protected], d
[email protected] *
Corresponding author
Keywords: Ventilation and Dust Control Window, Filtration System, PM2.5.
Abstract. A new type of PM2.5-controllable ventilation window was designed to control serious indoor air pollution. A three-layer filtration system was designed for the ventilation window, considering high concentration of outdoor particulate matter. Polyester membrane needle filter media was selected as medium efficiency filter for filtration system of ventilation window by experimental test. Controlling system of ventilation window was designed to test indoor PM2.5 concentration, temperature, air pressure, etc. Air flow rate of ventilation window and indoor air pressure could be controlled by the controlling system. Introduction Nowadays domestic air pollution is severe and haze pollution of outdoor appears more often than before. It became a dilemma choice whether opening the window or not to ventilate air indoor. A great deal of indoor pollutant comes out every day and the reduction of air flowing air cannot contribute to the elimination of the pollution, leading to poor indoor environment and the continuing appearance of “sick building syndrome”. As is known to all, people spent two thirds of their lives indoors. It is reported that the number of people who die from air pollution can amount to 111 thousand every year [1]. Therefore, it is of great significance to solve the problem of controlling indoor air pollution. In terms of the increasingly severe air pollution, especially the pollution of PM2.5, it is an effective way to choose an appropriate residential air purification facility to create a satisfying indoor environment [2]. At present, the indoor purification can be carried out by two methods. One is to make use of air-condition system or the fresh air system to control the indoor air quality, and the other is to use the air purifier indoor. The former method costs high, so there is a long way for it to be used widely. Relatively, it is more effective of the latter to solve the problem [3,4]. However, the latter only works with the door and widows closed. Once open the window and the unqualified outdoor air flows in, purification is hard to be carried out [5]. Namely, it still can’t solve the problem of indoor air quality thoroughly. In view of the above problems, this paper introduces a new type of ventilation and dust control window which not only simplifies the structure of the air supply system but also solves the problem of indoor air ventilation under poor outdoor air quality. In the meanwhile, considering the outdoor particles sizes’ wide range and its high concentration, according to the experimental analysis, a multi-layer filtering system is designed to realize saving energy and permitting flowing air under the influence of haze.
The Design of The Ventilation and Dust Control Window The Structure and Working Principle of The Ventilation and Dust Control Window The ventilation and dust control window is composed of two parts: the main body and the control part, as is shown in Fig. 1.
Figure 1. The schematic diagram of ventilation and dust control window.
The main body mainly consists of the ventilation and dust control window shell, the filter system filtration system, the fan, the control circuit box, the electric motor and so on. The filter part consists of three parts: the inefficient filter, medium efficiency filter and HEPA filter; The control part mainly comprises a liquid crystal display, detectors (one set of detectors test the outdoor pressure, temperature, and the content of PM2.5 and PM10; the other set of detectors tests the numerical value of the parameter above), integrated circuit board, power supply and so on. The Working Principle of the Ventilation and Dust Control Window (1) Owing to containing PM2.5, new air extracted by the fan from the outside will do harm to the human body if it flows directly into the interior. Composed of multi-layer filter, the window-shape ventilator filter paper box can effectively filter air particulates from the outside. The design of the multi-layer filter structure can reduce the replacement frequency of the high-efficiency filter, make good use of its purification function, realize the function to acquire new air with the window closed, filter clean air, and ensure good quality of indoor air. (2) To avoid a high indoor pressure in the process of air supply or a low negative pressure in the elimination procedure, it is the indoor and outdoor pressure sensor detector that tests the indoor and outdoor pressure and calculates the deviation. If the indoor pressure -outdoor pressure
the given range, the fan will import the outdoor fresh air into the interior by the window ventilation system, making a balanced air pressure. (3)The indoor and outdoor detector is responsible for testing the indoor and outdoor temperature. In winter, the indoor is much colder than the outdoor. If the cold outdoor air directly flows into the room, it will cause much discomfort. So we design a circuit to measure the indoor and outdoor temperature difference, which can control the resistance wire to be heated to an appropriate temperature, making the temperature inside and outside equal. With the temperature controlled in the fresh air exchanging process, the re-exchange process can achieve a satisfying effect.
(4)There is a diversion structure in the upper part of the shell, which can prevent the protruding part of the ventilator window from being affected by the rain and maintain its drying and hermetic performance, wind resistance and waterproof performance. (5)There is a hermetic device around the filter box which is a fully enclosed, ensuring a good air impermeability of the window ventilator. (6)There is a noise reduction device around the draught fan and the wall of the motor, with which the noise can be reduced to the accepted range for the human body, not affecting normal indoor activities. (7)The liquid crystal display will always show the indoor and outdoor temperature, humidity and PM2.5’s and PM10’s numerical values so that we can clearly observe the smog-proof and fresh air-exchanging effect that the window ventilator makes. The Design of The Filtration System The Structure of The Filtration System
Figure 2. The schematic diagram of the filtration system.
As is shown in Fig. 2, the filtration system consists of three kinds of filter media (the low efficiency, the medium efficiency and the high efficiency), upper cover plate, under cover plate, left cover plate, right cover plate and two kinds of sealing strips with different models and specifications. Working in a completely sealed environment, this system can reach the goal of exchanging the indoor and outdoor air. The upper cover is design with an 80 degree slope, matching with the 80 degree slope of the shell. The lower part of the shell has a rib plate, which can firmly fix the filter box in the device. Therefore, the box won’t be skewed by the increasing flowing air and can avoid generating cracks, achieving a highly-filtering effect. The Filter Media Selection It is not scientific of the ventilation and dust control windows that the indoor air filter has only one layer of high-efficiency filter material, because it cannot cope with the high concentration pollutants outside. This filtration system is designed with a combination of the low efficiency material, the medium efficiency material and the high efficiency material so as to effectively prolong the filter material’s service life and filter particles of different sizes. Among them, the low efficiency filter medium belongs to a type of widely-used filter net which is 5.5mm thick and made from fiberglass. Under the filtration velocity of 2m/s, the efficiency of filtering 150µm particulates can reach more than 60%. As for the high efficiency filter medium, it uses the commonly-used material HEPA which can filter more than 99% particulates of more than 0.3µm [6,7].
However, due to its large size, the medium efficiency filter material is difficult to be installed in the ventilation widow. Therefore, this paper introduces the bag-type dust filter material into the filtering system, and will focus on the selection of the medium efficiency filter. The Selection of The Medium Efficiency Filter Media There are three kinds of filtering media that have been tested for their filtration performance. Respectively, they are polyester fiber needled filter (a), PPS spunlace filter (b), and polyester membrane needle filter (c). Their performance parameters can be seen in table 1. In addition, the three materials have been tested for the counting efficiency and concentration efficiency on particles, the results of which are shown in Table 2, Table 3 and Fig. 3. Table 1. The parameter characteristics of experimental samples. Mass area ratio (g/m2)
Specimen
Operating Temperature(
Breathability (m3/m2•min)
Thickness(mm)
A
503.03
1.96
12.31
≤130
B
511.82
1.79
4.36
≤160
C
501.12
1.62
2.42
120
℃)
Table 2. The particle counting efficiency of the filter media with the wind blowing in the 2.0 m/min. Specimen
0.3~0.5µm
0.5~1.0µm
1.0~3.0µm
3.0~5.0µm
A
18.33%
22.42%
34.44%
71.63%
B
58.63%
64.21%
72.98%
89.30%
C
92.82%
95.53%
98.02%
99.23%
Table 3. The weighing filtration efficiency of different filter media for PM2.5 gauge under different wind speed. Wind speed(m/min)
Specimen 1.5
2
2.5
3
A B
28.28% 64.12%
25.35% 59.75%
23.81% 57.70%
21.20% 56.00%
C
95.70%
95.65%
95.65%
95.40%
Figure 3. The weighing filtration efficiency of different filter media for PM2.5 gauge under different wind speed.
From Table 2, it can be seen that the filtration effect of the three kinds of filter materials on the particulates is very different. The filtration efficiency of the fiber coated needle punched felt to dusts of more than 0.5-1µm is above 95%, while the polyester fiber needled felt is only 22%. From Table 3 and Fig. 3, it can be known that among the three materials, polyester resin coated filter material has the highest weight efficiency of more than 95% on PM2.5, and the filtration speed and particle size have a very small impact on it. It is followed by PPS spunlace filter whose weight efficiency is 56%-64%. The polyester needle punched filter has the lowest weight efficiency of only about 20% - 30% in the experiment. In conclusion, the polyester coated needle felt can be chosen as the filter material in the ventilation and dust control window system. The Design of The Control System Principle of The Control System The control system of the ventilation and dust control window is composed of a sensor, an information time collector, a single chip microcomputer, a data memory and a LED display, as is shown in Fig. 4.
Figure 4. The structure of the control system.
The control system is under the control of SCM STC89C52 and observe the fuzzy PID feedback control principle. It works as long as the concentration of PM2.5 is in the given ranged and has the function of self-organization and the ability of processing PM2.5, air pressure and temperature at the same time and keeping PM2.5 and temperature stable in the space environment. The control system first collects data by sensors, dealing with the data of the temperature and the concentration of the PM 2.5. Then the data will be stored in the memory storage. The system will control the fan speed and the state of wind extraction. Ultimately natural wind and comfortable living environment can be formed. The design of the control system mainly includes data acquisition and transmission, data processing and control. The detailed descriptions are as follows. Data Acquisition and Transmission The data acquisition process first collects outside information by the temperature sensor, PM2.5 sensor, and pressure sensor. Within the control frequency of the information regularly sampler, the process will transform the state data into signals and deliver it to the next level of signal processor. The control process is shown in Fig. 5.
Figure 5. Control system function.
Data Processing and Control The SCM will analyze data about PM2.5 delivered by the sampler and state data read by the memorizer. Those data will be sent to the central processor after signal processing (as in Fig. 5). Under the priority control, by determining what the PM2.5 concentration is under the outdoor temperature and comparing with the present working condition of the ventilation window, the motor will be triggered to control the air volume. The specific process is as follows: (1) Data reading and analysis Data information will be input through a WiFi remote control device and sensors, and the system preset operation data will be read and converted into digital signals through the D/A. Then the settings information will be saved (such as Fig. 6). Then digital signals of the control information and the sample information will be analyzed to determine the state of the indoor and outdoor environment. Micro controller reads the state of the present environment and determines whether the wind turbine needs to be triggered or not according to the data range of preset temperature, PM2.5, etc.
Figure 6. Flow chart.
(2) Control system After the motor being controlled after the instructions, it will control the rotate speed of the fan and the state of wind supply and extraction according to the set data standard so as to control the whole working condition of the dust control ventilation window. Conclusions This paper puts forward a new design scheme of ventilation and dust control window aiming at solving the problem of indoor PM2.5 pollution and air circulation, and makes a detailed design of the filtering system and the control scheme of the dust control ventilation window. Through the design, test and analysis, the following conclusions are obtained: 1. By filtering the natural wind introduced from the outside, the dust control ventilation window can control the PM2.5 with flowing wind allowed and ensure enough fresh air indoors. 2. In order to prolong the service life of the filter core, it is proposed that the medium efficiency filter material be applied to the dust control ventilation window. By testing and analyzing, it is recommended to use polyester film coated needle felt as the filter material. 3. The control system controlling the rotation speed of the fan and the state of wind supply and extraction, indoor air pressure adjustment can be realized, making indoor pressure in a micro positive state and preventing wind from flowing through cracks. Therefore, indoor air quality can be improved at its source. 4. The installation of WIFI and 2.4G wireless transmission system can make the machine switch controlled intelligently and reduce waste of resources under a clean indoor air condition.
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