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Ultraviolet germicidal irradiation is the use of ultraviolet energy electromagnetic radiation with a wavelength shorter than that of visible light to kill or inactivate viral, bacterial, and fungal species. The UV spectrum is commonly divided into UVA (wavelengths of 400 nm to 315 nm), UVB (315 nm to 280 nm), and UVC (280 nm to 200 nm). The entire UV spectrum can kill or inactivate many microorganisms, but UVC energy provides the most germicidal effect, with 265 nm being the optimum wavelength. The study of UVGI distribution is very important to show the effective of germicidal and find out a better location for UV lighting in order to improve indoor air quality.
A full-scale room (11.9 m3) fitted with a UVGI system consisting of 14 louvered irradiated the top 30 cm of the room (12 W total lamp powers per UVC lamp) and assumed maintained at 25C and 50% relative humidity. Correspondingly, there are total 1125 points of measurement and experiments were performed in some different conditions such as, height level, degree of the louver, existence of the louver, reflectivity and number of fins in the louver between the measurements. Besides the point measurement, using fluorescent material can also measure the distribution of ultraviolet irradiation. The system irradiates the upper part of a room while minimizing radiation exposure to persons in the lower part of the room.
Nowadays, people are more interest in the air quality in different environments. Especially after the outbreak of severe acute respiratory syndrome (SARS) in 2003, in which more than 8000 people were infected and over 700 people died (WHO, 11 July, 2003).As Hong Kong is an international city, there are many high rise building such as offices, shopping centers, hospitals. Many people need to stay interior area everyday. Hence, there are a lot of people who are infected by different infectious diseases through air transmission. Thus, the study of air quality in different indoor environments is now interested by different researchers in Hong Kong. One of methods to improve the indoor air quality is that using of ultraviolet (UV) energy to kill or inactivate viral, bacterial, and fungal species. Hence, the study of UV distribution can improving indoor air quality in these buildings becomes more important.
In order to prevent outbreak of infectious diseases such as SARS, we should have better information about the intensity of ultraviolet irradiation within upper-room area in indoor environments. It is found that indoor air quality can be controlled by the ultraviolet irradiation as UVC can kill the contaminants. As there is not many research papers for distribution of Ultraviolet irradiation at upper-room area, the purpose of this report is to understand the UV intensity distribution in some different conditions such as, height level, degree of the louver, existence of the louver, reflectivity and number of fins in the louver between the measurements.The system irradiates the upper part of a room while minimizing radiation exposure to persons in the lower part of the room.
There are several specific objectives:
1) To study the distribution of Ultraviolet irradiation by experimental methods.
2) To study the factors affecting Ultraviolet irradiation by experimental methods.
3) To study using fluorescent material to measure the intensity of Ultraviolet irradiation
2. Literature review
Literature review is done with a summary of literature search methods and the number of papers and articles found for the preparation work of this project. As a summary, UVGI system is affected by many factors.
2.1 In-Duct UVGI
In-duct UVGI systems are installed inside ventilation ductwork or inside AHUs. When selected to produce appropriate irradiance levels, in-duct systems are effective for surface and air disinfection. The goal of surface disinfection is to reduce or eliminate microbial growth on inÂternal surfaces of HVAC systems, typically cooling coils and drain pans. The goal of air disinfection is "on-the-fly" inactivaÂtion of microbes suspended in the air as it moves through the duct or AHU.
In-duct UVGI should always be used in combination with filtration. Filters help protect UV lamps from dust that may reduce UV output, and enhances the air cleaning capabilities of the system. Filters remove larger microbes like fungal spores that are more resistant to UVGI, while UV inactivates more susÂceptible organisms like bacteria and viruses. It is recommended that the highest-rated filter the fan motor can handle be used, while still providing adequate airflow to the space.
2.2 Upper-Air UVGI
Upper-air UVGI involves lamp fixtures suspended from the ceiling and/or installed on walls. Lamps are shielded to direct radiation upward and outward to create an intense zone of UV in the upper portion of the room while minimizing UV levels in occupied spaces. These fixtures inactivate airborne microorganisms by irradiating them as air currents move them into the path of the UV energy. Some louvered fixÂtures use small fans to enhance air mixing, which is a critical component of overall effectiveness.
Where an in-duct UVGI system may not be feasible, or where additional UVGI is desired to further reduce airborne infectious disease transmission, upper-air systems can provide an effective solution. Application and placement criteria for upper-air UV fixtures are provided in various publications, and manufacturer-specific advice on placement and operations should always be followed. A rule of thumb for upper-air installations has been one 30 W (nominal input) fixture for every 200 ft2 (18.6 m2) of floor space to be irradiated.16 Many effective systems have been designed to this criterion, yet it is important to note that not all 30 W lamps provide the same output of UVC energy. UVC output is dependent on the type of lamp, the lamp manufacturer, and variÂous other factors. Recent studies have suggested installing fixtures to maintain a uniform UV distribution of around 30 Î¼W/cm2 to 50 Î¼W/cm2 in the upper portion of the room.17 While essentially "normalizing" the recommended output over all lamps, this level of irradiance should be effective at inactivating most airborne droplet nuclei containing Mycobacterium, and would presumably be effective for inactivation of most viruses as well.
The overall effectiveness of upper-air UVGI systems improves significantly when the air within the space is well mixed. Although convection air currents created by occupants and equipment can provide adequate air circulation in some settings, mechanical ventilation systems that maximize air mixing are preferable. If air mixing with mechanical ventilation is not possible, fans can be placed in the room to ensure adequate mixing.
2.3 Relative Humidity
Relative humidity (RH) without a significant impact on the performance of UV lamps, and it's also impact on the susceptibility of micro-organisms is not well understood. However, Try to micro-organisms associated with the sensitivity of the RH have yielded inconsistent results, but it seems to be organisms specific. 18, 19
The relationship between reproductive health, and the k values seem complicated, but most of the studies the effect of an increase only in the relative humidity values above 70%. Recommended that UVGI system operation relative humidity less than 60%
This is in line with the recommendations of ASHRAE and other organizations to provide a comfortable, acceptable indoor air quality, reduction of indoor microbial contamination. Most upper-air UVGI systems are functioning properly to maintain relative humidity below 60%. On the contrary, in the air duct systems, often operate in high humidity levels.
2.4 Air Temperature and Velocity
Phillips Lighting (1992) states that the resonance line at 254 nm in a low-pressure mercury lamp is strongest at a particular vapor pressure that occurs in their proprietary UVGI lamps at a still air ambient temperature of about 68 F (20 C). For their lamps, this gives a lamp wall temperature of about 104 F (40 C), and the UVGI output is greatest at that temperature. At both higher and lower temperatures, the UVGI output is reduced, with the output at 50 F (10 C) being about 88% of that at 68 F (20 C). In their product literature, Westinghouse (1985) concurs. They note that the output of their UVGI lamps, like all other gaseous discharge lamps, diminishes as the temperature increases or decreases from the design temperature, which for the Westinghouse lamps is stated to be 80 F (27 C) in still air. They note that the output of one lamp at 40 F (5C) is only two-thirds of its output at 80 F (27 C.)
Westinghouse (1985) also notes that low temperatures can reduce the operating life of the lamps and that another of their proprietary lamps responds differently. Another lamp, when operated at its highest current input, is said to be much less sensitive to ambient temperature changes. Phillips Lighting (1992) makes a similar argument, saying that their medium-pressure mercury lamp, relative to the low-pressure lamp, has a higher power density and higher wall temperature and is less sensitive to ambient temperature fluctuations. High lamp output at the lower temperatures encountered in ducts is a central argument for the"high output UVGI emitter" presented by Scheir and Fencl (1998). Westinghouse (1985) further notes that low operating temperatures reduce the operating life of their lamps
The effect of airflow on UVGI lamp output is increased heat transfer that is due to the moving air. If the air moving past the lamp is ambient or cool, the lamp may be cooled below its optimum operating point, which reduces output. If the air is warm, the lamp may be heated above its optimum, which also reduces output. Lamps in the return air of building ventilation systems are likely to be slightly cooled below their optimum temperature, while lamps downstream of a cooling coil could be considerably cooled due to a combination of airflow and low temperature. Lamps designed for operation at low temperatures should also be resistant to airflow effects.
Air temperature and velocity generally do not affect microorÂganism susceptibility to UVGI. However, their combined effect on lamp temperature can cause significant variation in lamp output, and ultimately UV dose. Depending on the lamp used, the UV output for in-duct systems can vary by more than 60% across a range of temperature and velocity conditions typical of HVAC system operation, particularly in VAV systems where both can change simultaneously.20 Modern UVC lamps are designed to reduce the output variation experienced by lamps designed to operate at room temperatures and still-air conditions when they are used for in-duct applications. The impact of air temperature and velocity should be considered in the design of in-duct sysÂtems to ensure that desired performance is maintained across all operating conditions. Output variation due to air temperature and velocity is not a concern for most upper-air systems.
In the air duct system, increasing the effectiveness of UV is one of benefit of reflective tunnel. Reflection can be an economical way to increase the intensity of UV because of the reflected energy increases the energy. Although the surface may reflect the visible light, it may not reflect the ultraviolet light energy. For example, polished brass reflects the most of visible light, but less than 10% of ultraviolet radiation. Galvanized pipe material has UV reflectance rate of about 55%. Aluminum and other reflective materials can be used to line pipes in order to improve the effective UV intensity levels. System designers and manufacturers can provide information on improving the reflection of UV in air duct applications. Reflectivity also may be a concern about the upper-air system. For the properly designed, upper-air system installations essential for the removal from the ceiling or against a wall in the UV reflectance found that more than 10 feet (3 meters) from the lamp.
3.1 Stainless Steel Chamber
The stainless steel chamber is made as a scaled chamber for the experiment of the Ultraviolet lighting systems. The scale ratio of the chamber is a full scale room for measure the irradiance produce by different case of UVC lamp. In order to ensure the quality of insulation of the chamber, it is made by using stainless steel by the connection of welding. A UVGI system is installed in the middle of the full scale room and mounted in the overhead position 196cm above the ground surface by wire and plastic belt. The wire is mounted on the two edge of the wall by nail. This ensures the full integrity of the wall surface. The plastic belt is used to hold the louvers as the weight of the louvers is very heavy. There are great affections of the balance of the UVC light if we do not use the plastic belt. Moreover, there are two air diffusers and one T5 lamp is installed on the ceiling of the room. There are 5 surface of the room is make of stainless steel. The remaining side of wall which the door located is cover by duct tape.
3.2 Measurement Position at the Chamber
3.2.1 First measurement position
For the first measurement position, average 5 x 5 points is set up. However, there are some difficulties for the equipments to measure the reading due to the area from the wall. Besides, the side walls constrained the measurement position.
3.2.2 Second measurement position
Due to the above reason, a new measurement position is set up. These measurement positions converge to the lighting since there is a large UV intensity difference. It can easily input the data for the simulation and increase the accuracy for the changing of UV intensity.
3.3 Method of measurement
3.3.1 Preparation Work
1. Background of the room
There are some preparation work needs to be done before we began to measure UV intensity in different situations in different conditions. First, we must prove that the integrity of the original environment of room. First, we need to check the dark room conditions. Because we use double-sided tap adhere to the surface of the black paper in the room. There are some losses after we measure a set of data. After a period of time, we use an extra high-quality double-sided tap solved this query. Although the issue has been resolved, but we still need to check the status of the black paper before the start the experiment of every time we test.
2. Position and level of the UVC light
The status and level of ultraviolet light need to adjust every time due to the heavy weight of the louver that affecting the tension between the shutters and plastic tape. Therefore, we need to check their position by the ultra-infrared sensors to ensure the position correctly.
3. Angle of the louver
As the heavyweight louver, the nail of louver can not fixed the angle as a huge pressure on it. Therefore, the angle between the UVC light and louver is varied due to a long time period. We need to ensure the accurate angle from the protractor, and then start the experiment.
4. Calibration of the UV meter
The UV meter needs to set 0 numbers at no UV irradiance condition before using in the room measurement. We were informed about the importance of taking careful and patient measurements.
5. Usage of filter
The sensor is necessary to install with 2 type of filter that can measure the UVC 254nm wavelength irradiance. In the early time, we have missed the usage of the filter. Thus, the reading of the UV meter we measured is about 10 times of the truthful UVC wavelength irradiance. It needs to pay much attention on this.
The center UVGI system is operated at full power, 12 W. The UVGI system is warmed up for 30 minutes before constant irradiance reading occurred, after that the experiments were conducted. Cosine-response UV-meter is used to characterize the UVC distribution in the room. To measure the irradiance in the upper zone of the room .UV-meter were positioned at 45 planed spaced points of different height level from the floor. The UV meter is positioned by the tripod with three equally height chairs. The UV meter is need to tune its height to different height by raise or lessen the tripod's height. The height of tripod is measured by meter. Then, positioning the UV meter in one of 45 points marked on the ground by metal plummet.
1. Black Paper Measurement
1. The UV lighting is confirmed horizontal by the horizontal meter
2. The height of sensor is confirmed by the meter.
3. The irradiance reading is take place on the height of 200cm, 205cm and 210cm at 0 degree measurement.
3. The UV lighting is switched on and warmed up for 30 minutes
4. The UV sensor is ensured that facing the UV lighting directly and the metal plummet is indicated the points for measurement correctly.
5. The UV intensity is recoded from the UV meter for each measuring point
6. The measuring points are measured repeat for the height of 200cm, 205cm and 210cm and the weak lighting measurement for 205cm.
7. No ventilation was provided in this case during this period and the UVGI lamps were kept on.
8. We need to repeat the measurement until the reading of the points is symmetrical between A, B, C, D column's side and F, G, H, I column's side.
9. The 5 degree measurement for 205cm, 210cm and 215cm are repeated to measure.
10. After measure the high output lighting, the low output lighting is also measured at 205cm.
2. without Black Paper Measurement
1. The black paper is removed.
2. Repeating the same procedures for Black Paper Measurement.
3. The irradiance reading is take place on the height of 200cm, 205cm and 210cm at 0 degree measurement.
4. The irradiance reading of 205cm, 210cm and 215cm were measured at 5 degree.
5. There are ventilation supply by the diffuser and the leakage supply outside of the room.
3. Upward Measurement
1. The UV lighting is confirmed horizontal by the horizontal meter
2. The height of sensor is confirmed by the meter and no louver is included in this case.
3. The UV lighting is switched on and warmed up for 30 minutes
4. The UV sensor is ensured that facing upward to the ceiling and the metal plummet is indicated the points for measurement correctly.
5. The UV intensity is recoded from the UV meter for each measuring point.
6. The measuring points are measured for 1 lamp and 2 lamps at 200cm.
4. New Louver
1. There is no black paper included.
2. The UV lighting is confirmed horizontal by the horizontal meter 5 and the louver is tuned to horizontal 0 degree.
3. The height of sensor is confirmed by the meter.
4. The UV lighting is switched on and warmed up for 30 minutes
5. The UV sensor is ensured that facing the UV lighting directly and the metal plummet is indicated the points for measurement correctly.
6. The UV intensity is recoded from the UV meter for each measuring point
7. The measuring points are measured repeat again for all fins, 7fins and 4 fins.
8. The 5 degree measurement for all fins, 7fins and 4 fins is repeated to measure.
3.4 Application of LabVIEW with Grayscale pixel
3.4.1 Application of LabVIEW
At first, we use LabVIEW 7 as a platform for the connection of the web camera. The first step we need to do is that controlling the web camera in the computer. To do this application, it needs to install the NI-IMAQ for USB Cameras which this program can construct the sub-VI for connect between the computer and the web camera. Besides the NI-IMAQ for USB Cameras, it also needs to install the program which is Vision 8.5.0 Development Module. For this program, it is most important since this program is used for image processing.
After the connection between the computer and the web camera, it needs to capture the image from the web camera. The images have different pixel and it can show the value of pixel from the program of LabVIEW.
The above diagram is the VI block diagram for showing the value of pixel from the program of LabVIEW. The VI block diagram is combined by two parts. The first part is the connection of the camera. After passing though the first part of the camera, it will divide to another part which is IMAQ Image To Array. The function of this part is used to detect the income image pixel.
3.4.2 Grayscale pixels
Grayscale images are often the result of measuring the intensity of light at each pixel in a single band of the electromagnetic wave spectrum such as infrared, visible light, ultraviolet, etc. The Grayscale images can be combined from a full color image. In the case of transmitted, the brightness levels of the red (R), green (G) and blue (B) components are each represented as a decimal number from 0 to 255, or binary 00000000 to 11111111. For every pixel in a red-green-blue (RGB) grayscale image, R = G = B. The lightness of the gray is directly proportional to the number representing the brightness levels of the primary colors. White is represented by R = G = B = 255 or R = G = B = 11111111 and black is represented by R = G = B = 0 or R = G = B = 00000000, and. Since there is 8 bit s in the binary representation of the gray level, this imaging method is called 8-bit grayscale. As with 8-bit grayscale, the lightness of the gray colour is directly proportional to the number of representing the brightness levels of the primary colors.
1. The UV lighting is confirmed horizontal by the horizontal meter
2. The height of fluorescent plate is confirmed by the meter.
3. The UV lighting is switched on and warmed up for 15 minutes
4. The fluorescent plate is ensured that facing the UV lighting directly and the metal plummet is indicated the points for measurement correctly.
5. The UV intensity is recoded from the LabVIEW.
3.5.1 UV Lamps and Ballasts
Both were 36.8m long, T5 (0.73 cm diameter). The ballasts were connected to the lamps through three-pin power connectors. Power was provided to the end of lamp by wires running from power connector through the hole in the corner just above the ground outside of the room. Both high output lamps arrangement is the same, there is reflector behind the lamp to reflect and louvers to contribute the UVC ray discharge horizontal from the lamp. Their output is the same as reference data provided by supplier. They are 12W low mercury lamp but their UVC output is not the same due to relate to the different working life of them and different angle of the reflector which located inside the lamps. Because the industry does not use a standard test or reference method to measure UVGI lamp output presented in the sample technical paper. Hence, the test of lamps is through direct measurement. The two test lamps were identical visually except the UVC output is different. The two lamps output are measured by UV-meter before the experiment start and shown below
In our experiment, we mainly focus on the high output lamp.
3.5.2 UV meter ILT1400
Broadband UVC measurements require a two step zeroing process. The SEL240/TD measures both UVB (280 to 315 nm) and UVC (200 to 280 nm) wavelength light. The SEL240/UVB1/TD combination adds a sharp cut filter (UVB1) to measure only UVB. The SEL240/TD can be used alone in a single step measurement for most genera l purpose Ultraviolet applications.
3.5.3 UV sensor and Tripod
UV sensor is used to detect UV irradiance. To separate the UVA, UVB and UVC components, it needs to install the filter in front of the sensor. All ILT1400 detectors attach to the card edge at the top of the ILT1400 meter. The "L" listed in the detector model number signifies the use of the detector card edge connector required for connection to the ILT1400 Meter (ie. SEL,XRL, SPL).The detector card edge connectors have been carefully designed so that detectors and extension cables can be plugged onto the card edge both frontward and backward.
The SEL240 254 base detector contains a specially coated 0.33 cm2 UV stabilized silicon cell with a quartz window. The SEL033 is one of our most commonly used sensors. It can be used with a large assortment of filters, input optics and calibrations and covering the broad spectrum of 200 - 1100 nm.
3.5.4 UV Lighting and Original Louver
The louver is used to reduce and centralize UV irradiance. The UV lighting is equipped with concentric 14 black louvers of 0.7 cm spacing. The height of the louver is about 11 cm and they were installed so that the lower edge was located 1.96 m above the floor and the top was 14.5 cm below the ceiling. This arrangement discharges a band of UVGI in the upper level of the room, with an average depth of about 20 cm. The depth of the band is different throughout the room, the narrowest distance being closest to the lamps at 15 cm and the widest discharge height is about 20cm.
3.5.5 New Louver
As the fins inside the original louver is fixed, a new louver is designed which can removed the fins inside the louver.
3.5.6 Metal plummet
The metal plummet connected to the center of Tripod. The function of the metal plummet was a pointer to indicate the point for measurement.
3.5.7 Fluorescent Material
In order to reflect the value of UV which was emitted from the UV lighting, the fluorescent materials are applied.
In the case of dark room situations, the irradiance of three different level 200cm, 205cm and 210cm are measured. The results of the UV meter measurements for the UVGI lamps operating are presented in the above figure. The above contour shows 0 degree louver with high output lighting test. For the horizontal level with UV lighting which is 205cm, the UV irradiance peak in the region closest to the luminaries and the area along the diagonals of the room. In the case of 205cm, there are two set of measurement with different UV light. For the strong light, the highest value of 205cm was 432ÂµW/cm2. For low output lighting, the maximum value is 381Î¼W/cm2 and the minimum is 2.4Î¼W/cm2. The UV irradiance value decrease far away from the lamp in the case of 205cm. At 200cm, it shows that the UV irradiance value is low but increase far away from the lamp and all readings is almost 30ÂµW/cm2. The maximum value is 45.2Î¼W/cm2 and the minimum is 0.5Î¼W/cm2. There is same case occurred at 210cm but the UV irradiance value is lower than the readings of 200cm and all the readings is lower than 3ÂµW/cm2. The maximum value is 2.9Î¼W /cm2 and the minimum is 0.61Î¼W /cm2. Besides, all the reading in this set measurement data is symmetrical.
The UV irradiance with UV lamps operating at 5 degree upward is also measured. At horizontal level of the louver, the UV irradiance readings at 205cm are the largest value. However, when the UV lamps operate at 5 degree upward of the louver, the UV irradiance is shifted from 205cm to 210cm. In the case of 205cm, there are two set of measurement with different UV light. For the case of 205cm of high output lighting at 5 degree, the maximum value is 375Î¼W/cm2 and the minimum is 0.42Î¼W/cm2. For the low output lighting, the maximum value is 259Î¼W/cm2 and the minimum is 0.42Î¼W/cm2.Besides, it shows that the UV irradiance decrease at 205cm and 210cm respectively. Moreover, the above contour shows that the value of UV irradiance increase at the back side at 215cm. However, in the case of 215cm, the maximum value is 30Î¼W/cm2 and the minimum is 0.1Î¼W/cm2.Besides, all the reading in this set reading is symmetrical. Hence, it proves that the louver is affected the UV irradiance direction and intensity form this contours.
4.1.2 2 Lamps with Original Louver
In the case of dark room situations, the irradiance at level 200cm with situation of one lamp and two lamps is measured. The UV meter faces to the roof of the room to measure the irradiance at eye level since there is no different between one lamp and 2 lamps as the sensor can face the either lamp only.
In the case of 200cm with one lamp, the maximum value is 107Î¼W/cm2 and the minimum value is 0.1Î¼W/cm2. In the case of 200cm with two lamps, the maximum value is 92.6Î¼W/cm2 and the minimum value is 1.2Î¼W/cm2. Moreover, all the reading is symmetrical in this set data. From the above contour, it can conclude that using 2 UV lighting in the room can provide an average UV irradiance condition and it can increase the efficiency of inactivate viral, bacterial, and fungal species.
4.1.3 No Louver
In the case of 200cm, the maximum value is 1860Î¼W/cm2 and the minimum is 0.42Î¼W/cm2. In the case of 205cm, the maximum value is 3000Î¼W/cm2 and the minimum is 1.4Î¼W/cm2 .In the case of 210cm, the maximum value is 3000Î¼W/cm2 and the minimum is 2.5Î¼W/cm2. Besides, all the reading in this set data is symmetrical. From the above contour, it can conclude that occupants cannot use UV lighting in the room under no louver condition as the UV intensity value is too large.
In the case of 205cm with all fins of louver, the maximum value is 465Î¼Wcm2 and the minimum is 2.8Î¼W/cm2. In the case of 205cm with 7 fins, the maximum value is 555Î¼W/cm2 and the minimum is 4.5Î¼W/cm2 .In the case of 205cm with 3 fins, the maximum value is 602Î¼W/cm2 and the minimum is 3.3Î¼W/cm2.
The UV irradiance with partial fins of new louver is measured. For the 0 degree new louver with high output lighting test, the highest value of 205cm is 465ÂµW/cm2 and the UV irradiance value decrease far away from the lamp. At 7 fins, it shows that the UV irradiance value is larger than all fins reading and the highest value of 7 fins is 555ÂµW/cm2. There is same case occurred at 3 fins and the UV irradiance value is the highest reading in 3 sets data at 205cm and the highest value of 3 fins is 602ÂµW/cm2.
The UV irradiance with partial fins of new louver with 5 degree is also measured. In the case of 205cm with all fins of louver, the maximum value is 1108Î¼Wcm-2 and the minimum is 6.2Î¼W/cm2. In the case of 205cm with 7 fins, the maximum value is 1211Î¼W/cm2 and the minimum is 5.9Î¼W/cm2 .In the case of 205cm with 3 fins, the maximum value is 1680Î¼W/cm2 and the minimum is 7.4Î¼W/cm2. All the UV irradiance value decrease far away from the lamp in all fins, 7 fins, and 3 fins. Besides, all the readings in 3 fins louver is the highest irradiance value compare with all fins and 7 fins. For the above contours, it proves that the louver fins are affected the UV irradiance direction and intensity.
The UV irradiance with different background material was also measured. The maximum value with black paper measured by UV meter is 432ÂµW/cm2 and the maximum value without black paper is 257ÂµW/cm2. Besides the case of 205cm, the maximum value is 17.3Î¼W/cm2 and the minimum is 0.1Î¼W/cm2 in the case of 200cm. Also, the maximum value is 1.1Î¼W/cm2 and the minimum is 0.1Î¼W/cm2 in the case of 210cm. There have some mistake occur at the above data. In normal situation, the readings without black paper should be larger than the readings with black paper since there is a reflectance with stainless steel. However, the experience reading is opposite. The reasons of an error occurred in this set data due to the change of air temperature or velocity as the ventilation system is operated. Hence, there is an error occurred in this set data. Although the data should be having an error for intensity, it can know that the UV irradiant is also diverge to 200cm and 215cm form the above contour.
There is same case in the 5 degree without black paper. In the case of 205cm, the maximum value is 251Î¼W/cm2 and the minimum is 1.1Î¼W/cm2. In the case of 210cm, the maximum value is 58Î¼W/cm2 and the minimum is 0.72Î¼W/cm2. There have same mistake occur as the 0 degree data. In this situation, the readings without black paper are smaller than the readings with black paper. Hence, the experience reading is opposite normal situation. The reasons of an error occurred in this set data due to the change the air temperature or velocity as the ventilation system is operated. Hence, there is an error occurring in this set data.
It is so surprised that the irradiance of measurement is more significant for the black paper room than the reflected room. The reason why may be the ratio of reflected irradiance in the measurement height is so small in total irradiance. Another reason may be the wall material will absorb the irradiance by the light source. The last reason as case 4 measurement is under ventilation status. The cooler air stream or the lower humidity of the room may be lessening the irradiance on the upstream of the room. Therefore the irradiance of the reflected room is lower than the black room.
4.4 Fluorescent measurement
When the UV irradiance meets the fluorescent material, it will show the different intensity. As the result shows in Different level before, there are different pixel values showed in the LabVIEW.
There is a large different between the UV lighting on and off. The fluorescent material shows the UV intensity directly. After that, the LabVIEW can show the grayscale pixel value. This method is more convenience than using the UV meter to measure the UV intensity value since UV meter is a point measurement but using fluorescent material plate is a 2 dimension measurement.
This is an example using in the 0 degree with high output power lighting. When the fluorescent plate is located at the point 2, the mean pixel value is 255. For the horizontal level with UV lighting which was 205cm. The highest value of 205cm is 432ÂµW/cm2 and the UV irradiance value decrease far away from the lamp. When the fluorescent plane is located at the point 3, the mean pixel value is decrease. Moreover, when the fluorescent plane is located far away the UV lamp, the pixel value also decrease far away from the UV lamp. It can use this VI to do some management for the web camera and know the pixel from the LabVIEW. Moreover, after getting the data of pixel, it can do image processing from the Vision 8.5.0 Development Module. It can make a setting for a range of intensity or pixel from the image.
Besides all fins with new louver, the above diagram shows that the LabVIEW using in 7 fins with new louver. When the fluorescent plane is located at the point 2, the mean pixel value is 255 as the UV intensity value is 347ÂµW/cm2. The UV irradiance value decrease far away from the lamp. When the fluorescent plane is located at the point 3, the mean pixel value is decrease to 216. Moreover, when the fluorescent plate is located far away the UV lamp, the pixel value also decrease far away from the UV lamp. It shows the pixel value is 42 and the UV intensity is 48.2ÂµW/cm2 when the fluorescent plane is located at the point 7.
The above diagram shows that the LabVIEW using in all fins with new louver at 5 degree. When the fluorescent plate located at the point 2, the mean pixel value is 255. For the horizontal level with UV lighting which is 205cm, the UV irradiance peak in the region closest to the luminaries. The highest value of 205cm was 550ÂµW/cm2 and the UV irradiance value decrease far away from the lamp. When the fluorescent plane located at the pt 4, the mean pixel value is decrease. Moreover, when the fluorescent plane is located far away the UV lamp, the pixel value also decrease far away from the UV lamp. It shows the pixel value is 61 and the UV intensity is 64.8ÂµW/cm2 when the fluorescent plane is located at the point 7.
The above diagram is the calibration curve which is combined from the above result. It shows that the grayscale level is directly proportional to the number of representing the brightness levels of the fluorescent colors. The brightness level of the fluorescent colors depends on the intensity of UV. However, we can see the limitation from the above calibration curve as grayscale value is 255 when the maximum value is about 280ÂµW/cm2.
To conclude the above result, it is know that the different height level will provide different reading in UV lighting. In normal situation, the reading should be applied for inverse square law as UV is one kind of EM Wave. However, the UV distribution can be affected by many factors such as the height level, air temperature, velocity. Besides, there has a louver in front of the UV lighting in the chamber. Hence, inverse square law is not applied in this experiment but it can nearest the real life and application of hospital.
Hence, the above results can be used to find out the best mounting location of UV lighting since it shows that the intensity in different conditions such as, height level, degree of the louver, existence of the louver, reflectivity and number of fins in the louver between the measurements. For using of ultraviolet energy to kill or inactivate viral, bacterial, and fungal species, the above factors must be concerned. The system irradiates the upper part of a room while minimizing radiation exposure to persons in the lower part of the room.
For the Future development, it needs to consider the measuring
In this experience, there are some factors need to improve,