DF Cabin Air-Quality Pollution Detection and Prevention Master’s thesis in Sustainable energy systems Rakshith Bharadwaj Ramakrishna Subramanya Department of Architecture and Civil Engineering CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden 2021 Master’s thesis 2021 CABIN AIR-QUALITY POLLUTION DETECTION AND PREVENTION Rakshith Bharadwaj Ramakrishna Subramanya DF Department of Architecture and Civil Engineering Building Services Engineering Chalmers University of Technology Gothenburg, Sweden 2021 Rakshith Bharadwaj Ramakrishna Subramanya © Rakshith Bharadwaj Ramakrishna Subramanya, 2021. Company Supervisor: Amanda Ulvmyr,CEVT Supervisor: Lars Ekberg,CIT(Chalmers) Examiner:Jan-Olof Dalenbäck,Department of Architecture and Civil Engineering Master’s Thesis 2021 Department of Architecture and Civil Engineering Building Services Engineering Chalmers University of Technology SE-412 96 Gothenburg Telephone +46 31 772 1000 Cover: Cabin Air-Quality Pollution Detection and Prevention. , template by David Frisk Printed by Chalmers Reproservice Gothenburg, Sweden 2021 iv CABIN AIR-QUALITY POLLUTION DETECTION AND PREVENTION Rakshith Bharadwaj Ramakrishna Subramanya Department of Architecture and Civil Engineering Chalmers University of Technology Abstract The purpose of this thesis is to study and test the performance of the current CEVT Air-Purification System for Multiple Air Pollutants, primarily particles but also gases. The tests are designed to reveal differences between traditional air filters and a variety of other air-purification technologies such as an air ionizer, a plasma generator, and an ozone generator. Furthermore, this research is split into two sections: The first section focuses on ex- periments conducted in a real car cabin. The measurements in a laboratory test rig make up the second part. The results of the observations made in the two settings are compared and used to evaluate the various air cleaning technologies. As expected, the efficiency of all filters is higher at lower air flow rates (lower air velocity through the filters) than at higher air flow rates. The results show that the performance of A/F-3 improved reliability in both car and lab test-rig tests, i.e. new air filters with non-active carbon typically showed slightly higher efficiency values than the other tested filters, followed by A/F-2 new air filters with active carbon coating. Among the filters with active carbon, it was only the new one that showed any measurable reduction of organic gas. Keywords: Air filter, filter efficiency, active carbon, air pollution, particulate matter, PM2.5, PM10 v Acknowledgements I dedicate the success of this master thesis by mentioning the people who made it possible, whose guidance and continuous encouragement boosted efforts and guided towards success of this master thesis. I take this opportunity to express my gratitude to Examiner Jan-Olof Dalenbäck, College supervisors Lars Ekberg and Company supervisor Amanda Ulvmyr for their guidance and regular valuable inputs during the entire master thesis period. I am fortunate to have them as supervisors for this master thesis. As they provided enormous support, technical knowledge by sharing new ideas which helped me to understand the concepts required for completing this master thesis. Finally, I would like to dedicate my appreciation to my parents for their love and continuous support during the entire duration of master studies and also I would like to thank my friends for supporting me. Rakshith Bharadwaj Ramakrishna Subramanya, Gothenburg, 2021 vii Contents List of Figures xi List of Tables xiii 1 Introduction 1 1.1 Aim of this work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Outline of the present work . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 Airborne pollutants 3 3 Tested Objects 5 3.1 Air filter with Active carbon coating . . . . . . . . . . . . . . . . . . 5 3.2 Air filter without Active carbon coating . . . . . . . . . . . . . . . . . 6 3.3 Air ionizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4 Plasma generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5 Ozone generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 Methods 11 4.1 Test set-ups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.1 Method’s used for testing in car efficiency . . . . . . . . . . . 11 4.1.2 Method’s used for testing Efficiency in LAB . . . . . . . . . . 13 4.2 Measurement instruments . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.1 Condensation particule conter (P-Trak) . . . . . . . . . . . . 16 4.2.2 Optical particle counter (Met One) . . . . . . . . . . . . . . . 17 4.2.3 Gas analyser (Brüel Kjaer) . . . . . . . . . . . . . . . . . . . 18 4.2.4 Air velocity and pressure differential instrument (Anemometer) . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 5 Results 21 5.1 Example of results for in-car testing . . . . . . . . . . . . . . . . . . . 21 5.2 Example of results from lab-testing . . . . . . . . . . . . . . . . . . . 24 5.3 Final efficiency values for ultrafine particles . . . . . . . . . . . . . . 26 5.4 Efficiency values for particles larger than 0.3 µm . . . . . . . . . . . . 26 6 Summary and Conclusions 29 6.1 Final remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 ix Contents Bibliography 31 A Appendix 1 I A.1 Results for Air-Ionizer and Plasma Generator . . . . . . . . . . . . . IV A.2 Efficiency Results for Air-Ionizer and Plasma Generator . . . . . . . IV A.3 Air Filters Used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI x List of Figures 3.1 Air filter with active carbon coating. . . . . . . . . . . . . . . . . . . 5 3.2 Air filter without Active carbon coating Filter designation: A/F-3. . . 6 3.3 Air Ionizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.4 Plasma Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.5 Ozone Generator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1 Car Test setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2 Free flow of particles at air Intake. . . . . . . . . . . . . . . . . . . . 13 4.3 Lab-Setup (Test Rig) . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.4 Lab-Setup (Test Rig) . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.5 Metallic box(Test Rig) . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4.6 Condensation particule conter (P-Trak) . . . . . . . . . . . . . . . . . 17 4.7 Optical particle counter (Met-One) . . . . . . . . . . . . . . . . . . . 18 4.8 Gas analyser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.9 Air velocity and pressure differential instrument type Swema Air 300. 19 5.1 Particle concentration measured with the MetOne particle counter for all five filters, at three different air velocities in the lab test -rig. Concentration values presented as particle number per cubic feet (p/ft3) 27 A.1 Lab test efficiency results . . . . . . . . . . . . . . . . . . . . . . . . . IV A.2 Car test efficiency results . . . . . . . . . . . . . . . . . . . . . . . . . IV A.3 Different fan speed results . . . . . . . . . . . . . . . . . . . . . . . . V A.4 Different fan speed results . . . . . . . . . . . . . . . . . . . . . . . . V A.5 Air filter 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI A.6 Air filter 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VI A.7 Air filter 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII A.8 Air filter 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII A.9 Air filter 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIII xi List of Figures xii List of Tables 3.1 Summary of tested air filters. . . . . . . . . . . . . . . . . . . . . . . 5 4.1 : Gases measured by the Brüel Kjaer 1302 gas analyser. . . . . . . . 19 5.1 Values taken for air filter A/F-1 in the car - Trial 1 using the P-Trak 22 5.2 Average efficiencies of air filter A/F-1 in the car obtained from all three trials for ultrafine particles using the P-Trak instrument. . . . . 22 5.3 Measured gas concentrations for air filter A/F-1 during Trial 1. . . . 23 5.4 Average gas concentration based on all three trial of filter A/F-1 in the car . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.5 Values taken in the test-rig for filter A/F-1. Trial 1 using the P-Trak.) 24 5.6 Average efficiencies for ultrafine particles (P-Trak) of air filter A/F-1 in the test-rig. Data from all three trials using. . . . . . . . . . . . . 25 5.7 Final average efficiency results for all five air filters when tested in the car for ultrafine particles using P-Trak . . . . . . . . . . . . . . . 26 5.8 Final average efficiency results for all five air filters when tested in the lab test-rig for ultrafine particles using P-Trak . . . . . . . . . . . 26 5.9 Difference (%) between efficiencies obtained in the car and in the lab test-rig. Results for ultrafine particles measured using P-Trak. . . . . 26 5.10 Filtration efficiency values determined for the five filters at three dif- ferent air velocities in the lab test-rig . . . . . . . . . . . . . . . . . . 28 A.1 Average efficiencies of Air filter 2 with Active Carbon (New) . . . . . I A.2 Average efficiencies of Air filter 3 without Active Carbon (New) . . . I A.3 Average efficiencies of Air filter 4 with Active Carbon (old-1) . . . . . II A.4 Average efficiencies of Air filter 5 with Active Carbon (old-2) . . . . . II A.5 Average gas concentration for Air filter 2 with Active Carbon (New) . II A.6 Average gas concentration for Air filter 3 without Active Carbon (New) III A.7 Average gas concentration for Air filter 4 with Active Carbon (old-1) III A.8 Average gas concentration for Air filter 5 with Active Carbon (old-2) III xiii List of Tables xiv 1 Introduction In recent years, awareness and mitigation of air pollution has been at the forefront due to serious implications of poor air quality, which is related to human health and well-being. Subsequently, the development in the automotive production industry is met with new challenges every day due to increasing air pollution, which have raised the interest in finding new technologies within the engine development field, which is found to be very necessary for the preservation of human well-being. The rapid progress in this field involves the advancement of air cleaner technology, as well as the development of the best possible means of testing the air quality inside the vehicle cabin. Air quality in car cabins depends mainly on outside air quality, which tends to be the determining factor for calculating the efficiency of the air filter. Air pollutants are nitrogen oxides (NOx), particulate matter (PM1, PM2.5, PM10), carbon monoxide (CO), ozone (O3) and volatile organic compounds (VOC) present throughout the air. The nature of the time people spent in their cars determines the impact of air pollution on their health. It is therefore necessary to maintain a reasonable air qual- ity inside the car. In climate control system is the most important system impacting the condition of the air inside the car cabin. For this reason, advancement in the climate system is very important for improving the air quality of the vehicle. It is also of great importance to find suitable methods to evaluate/judge the performance of systems and components used to create good car cabin air quality, e.g. air filters. Health problems from air pollution are serious nowadays. Bad air quality inside the vehicle may lead to increased respiratory disorders like asthma and bronchitis; It even may pose a risk for cancer. By looking at these health issues related to impure air inside the vehicle, it is very important for us to look at how to improve the air quality inside vehicle cabins, by evaluating possible measures to reduce the air pollution inside the vehicle cabin. This is mainly a matter of establishing knowl- edge about the efficiency of present air filters, and also a matters of searching for technology improvements. 1 1. Introduction 1.1 Aim of this work The goal of this thesis project is to analyze and evaluate the air cleaning performance of alternative air cleaning devices for various air pollutants, mainly particles, but also selected gases. Another goal is to explore two alternative experimental methods: One where measurements are made in a real vehicle cabin, and the other where measurements are made in a specially designed a laboratory filter-test rig. 1.2 Outline of the present work This thesis is divided into two sections: A background to the measured air pollu- tants is given in chapters 2. The tested objects are described in chapter 3 and the measurement methods are summarized in chapter 4. The first part of chapter 5 shows detailed results from one selected filter-test of each test set-up (car cabin and test-rig). This structure is intended to facilitate the understanding of the methodology used. In the last part of chapter 5 the results from all filter tests are summarized. The full collection of data collected for all test cases is presented in the Appendix. 1.3 Limitations This thesis work mainly involves testing the filtration efficiency of air filters using air pollutants present in a laboratory setting in Gothenburg. Most of the measure- ments comprise small airborne particles in so called ultra-fine size range. A large fraction of the particles originate outdoors, and are typically generated by vehicles with combustion engines. However, in order to reach a high enough concentration, test-particles were added to the air by burning candles in the laboratory. SO, the added particles were generated by combustion, just as the naturally occurring parti- cles. This speaks for a clear relevance of the test particles used. Note that generation of test-particles by candle burning is a commonly used procedure in aerosol testing. However, the test particles used in the lab-tests do not necessarily have the same properties as typically occurring outdoor particles, which in cities typically is dom- inated by vehicle exhaust. So, the test were made with test particles that in some respects might be different from the particles the filters would be exposed to during real operation of the car. A final remark is that the single particle property that dominates the filtration efficiency is the particle size. From the experiments the particle size is known, at least to a large extent. 2 2 Airborne pollutants Based on the particle size, airborne pollutants may be categorized into various groups, consisting of particles with a dimension of < 10 µm (PM10), small particles with a dimension of < 2.5 µm (PM2.5) and even smaller particles with a dimension of < 0.1 µm (PM0.1). Particles smaller than 0.1 µm are denoted ultrafine particles or nano-particles. Many studies have determined that contaminants with small dimensions/sizes (ul- trafine particles) may be especially harmful and cause health problems for humans. Pollution from automobiles is a primary cause of such airborne pollutants. Also large particles may show negative health effects, such as pollen of various sorts. Sizewise there is a border around 5 nano-meters (0.005 µm). Above that size the theories of airborne particles, aerosol physics, apply. Below that size, the objects are no longer called particles, they are gases and vapors. Gases of relevance to outdoor air quality, and consequently of relevance to car-cabin air quality are carbon monoxide (CO), nitrogen dioxide (NO2), various volatile or- ganic compounds (VOC), such as benzene, touene and xylene. VOCs and carbon monoxide is directly generated and emitted by combustion engines. Nitrogen dioxide is typically a secondary pollutant, generated by oxidation of nitrogen monoxide un- der the influence of ozone (O3). Outdoors, near traffic, O3 is generated by chemical reactions involving VOCs and sunlight. 3 2. Airborne pollutants 4 3 Tested Objects A number of different air filters and air purifying devices were tested, such as, particle filters without active carbon, particle filters with active carbon, an air ionizer, a plasma generator and an ozone generator. Table 3.1: Summary of tested air filters. Air Filters Type A/F-1 Active carbon Air Filter used in car for 7500 Kms A/F-2 NEW Active carbon Air Filter A/F-3 NEW Air Filter without Active carbon coating A/F-4 Active carbon Air Filter used in car for 30000 Kms A/F-5 Active carbon Air Filter used in car for 30000 Kms and Dusty 3.1 Air filter with Active carbon coating Figure 3.1: Air filter with active carbon coating. 5 3. Tested Objects Regular air filters assist with the cleaning of polluted air, such as pollen extraction, dust particles, soot and fresh ventilation inside the cabin. The air-conditioning in- side the cabin that removes odours is also maintained by carbon coated air filters. Traditional air filters are strong enough to carry out some of the above operations, but the Active Carbon Air Filter is an even better form of air filter. It’s the most common form of air filter that has been used for a long time in many vehicles. The primary benefit of using active carbon filters is that it not only filters dust particles, it also eliminates odours, helping to keep the vehicle cabin to be a healthy and comfortable environment. Active carbon coating, with the assistance of the adsorption process, helps to cap- ture potentially harmful gases such as nitrogen dioxide on the carbon coated surface, as the active carbon filter fabric is extremely porous in nature, making it effective in filtering not only particles, but also gases and odours. The tested filters designated A/F-1, A/F-2, A/F-4 and A/F-5, see Table 3.1, are of this type. Details of the tested filters properties has not been provided by the manufacturer of vendor. Thus, the total filter area, nominal air flow rate, face velocity, rated pressure drop, and the amount of active carbon are unfortunately unknown to the author and cannot be specified in this report. 3.2 Air filter without Active carbon coating Figure 3.2: Air filter without Active carbon coating Filter designation: A/F-3. Cabin air filters helps in cleaning contaminated air by filtering pollen, dust particles, soot and provides fresh clean air inside the cabin. Air filter without active carbon coating basically refers to air filter without any active carbon coating on its fabric. 6 3. Tested Objects Details of the properties of the tested filter A/F-3 has not been provided by the man- ufacturer of vendor. Thus, the total filter area, nominal air flow rate, face velocity, rated pressure drop, fiber material and fiber diameter are unfortunately unknown to the author and cannot be specified in this report. 3.3 Air ionizer Figure 3.3: Air Ionizer. The air ionizer is a system used to eliminate particulate matter from indoor condi- tions. The device is composed of two electrodes at its end, as seen in 3.3, which, as high voltage current is transmitted through the device, produces a discharge be- tween the two electrodes. The discharge leads to airborne particles being electrically charged, which makes them prone to deposit on surrounding surfaces. Thus, the ion- ization enhances particle removal from the air. Details of the properties of the tested air ionizer has not been provided by the man- ufacturer of vendor. Thus, neither the voltage or ionization capacity, nor any other important properties are known to the author and cannot be specified in this report. 7 3. Tested Objects 3.4 Plasma generator Figure 3.4: Plasma Generator. Plasma generator is also one of the air purification devices that, with the aid of carbon fiber brushes present at the tip of the device, generate ions (negative and positive charged particles) helping to remove particles in the air and to control foul smells in indoor environments. Details of the properties of the tested plasma generator has not been provided by the manufacturer of vendor. Thus, neither the voltage or ionization capacity, nor any other important properties are known to the author and cannot be specified in this report. 8 3. Tested Objects 3.5 Ozone generator Figure 3.5: Ozone Generator. The ozone generator is a system developed for the creation of ozone gas. The ozone generator used here has an ozone generation capacity of 10,000 mg per hour and is claimed be able to eliminate bad odours. With the aid of a fan, the ozone is spread throughout the room. 9 3. Tested Objects 10 4 Methods There are two parts to this thesis study, the first part relates to the conduct of experiments to determine the varying efficiency of various air filters using the test car provided by CEVT and the second part is to conduct a related experiment in a laboratory by building a custom test rig with similar conditions as during the test in the car. The time interval for each reading taken in all experiments is one minute each. In this thesis two new air-filters with and without active carbon coating are tested along with one active carbon air filter used which has run for 7500 kilometers (km) and two old used active carbon air filter used which has run for 30000 km. 4.1 Test set-ups 4.1.1 Method’s used for testing in car efficiency In this process, two types of air filters are used, namely air filter without active carbon coating and air filter with active carbon coating, five separate air filters are considered for measuring efficiency among which 3 air filters used are (old) carbon coated filters and one new air filter with and without carbon coating are used. The devices used in these procedures are P-Trak for measuring the concentration of particles mainly in the ultra fine size-range, gases such as CO2, VOC and water vapor, etc. In this process, air within the lab hall is used as a concentrate upstream and air from the steel chamber (clean room) flows freely through the lab hall, few candles are constantly burned to produce additional particles within the lab hall as well as in the clean room. Using two P-Trak instruments efficiency of each air filter are calculated at three separate air velocity/flow corresponding to (30.3,60 and 115.2 l/s), corresponding to the car air conditioning fan speed 1-3-7 shall be determined using an air flow measurement system (velocity meter). The devices used in these procedures are a condensation particle counter, model P- Trak, for measuring the concentration of particles mainly in the ultra fine size-range. Measurements were also made with an IR-spectrometer, model Brüel Kjaer 1302, in order to determine the concentration of gases such as CO2, total concentration of VOCs, aldehydes and water vapor. In this process, air within the lab hall was used, together with an additional supply of particles generated by burning candles 11 4. Methods in an adjacent test chamber. Air from the test chamber was released close to the air intake to the car cabin. Using two P-Trak instruments, one was sampling air before the tested filter and the other was sampling after the filter, inside the car. The filtration efficiency of each air filter was calculated at three separate air velocities/airflow rates corresponding to an air supply of 30.3 l/s, 60 l/s and 115.2 l/s. These values correspond to the car air conditioning fan speed 1, 3 and 7, respectively. As mentioned above measurements were made by positioning the P-Trak instrument at two different positions, before and after the air-filter. The particle measuring po- sition inside the car cabin was in the middle of the front passenger seat (after the air filter measurement point). Outside the car, the sampling was made before the air intake valve (before air filter measurement point). All values are reported at a time interval of 1 minute for each particular measure- ment and the average value is taken to know the overall particle count for each different air filter at different air velocity/flow rate. This process is replicated until the findings are reasonably consistent. After calculation of both after and before particle count values using the P-Trak instrument, all values are tabulated, the av- erage value is taken, and the performance of each air filter is calculated. Efficiencies for both new and old air filters are compared at the end and the best air filter is recommended for increased performance. Apart from this, a further experiment is being carried out with air-ionizer and plasma generator systems to decide the best possible air-purification technology among them. This trial was also carried out with the P-Trak instrument using the same technique inside the car and the findings are tabulated and the correct air purification technology is recommended at the end of the experiment. Ozone generator is one of the air purification instruments that has been tested inside the car and it is found to be very dangerous to run since it begins to emit ozone at a very high level, which is found to be very harmful to humans, and aside from that, even after the ozone generator has been switched off the ozone generated by the instrument have stayed inside the car for a longer period of time. 12 4. Methods Figure 4.1: Car Test setup. Figure 4.2: Free flow of particles at air Intake. 4.1.2 Method’s used for testing Efficiency in LAB In order to perform the laboratory experiment, a custom test setup is designed con- sisting of a metal box enclosure with sealants to prevent air leakage and two turbo fans are used to force outside air into the metal box inside which the test specimen (air filters) is mounted. In this laboratory process, a series of tests were carried out using the P-Trak and the met one particle counters. Experiments are carried out in two parts, first calculating the particle count without an air filter inside the metallic box and then measuring the particle count with an air filter inside the metallic box using the same instru- ments so that the accuracy is preserved. In this experiment, the measuring point for all the experiments is kept constant, the measurement point is set at the escape 13 4. Methods point of the test-rig. During the examination, air inside the lab hall is used as an upstream concentration and air from the test chamber flowing freely through the lab hall. Few candles are constantly burned to produce particles within the lab hall as well as in the test chamber. Using a single P-Trak and Met One particle counter each filter was tested at three air velocities/flow rates corresponding to a face velocity of 1.5 m/s, 2.99 m/s and 5.73 m/s, respectively. The values were measured using a hot-wire anemometer. These air velocities are comparable to the velocity/flow rates used in the car tests of the previous test set-up. Values were reported with a time interval of 1 minute for each particular measure- ment and an average value is taken to know the overall particle count for each different air filter at different air velocity/flow rate. This process is replicated un- til the findings are reasonably consistent. After calculating both with an air filter and without an air filter inside the metallic enclosure, the particle count values are calculated using a single P-Trak instrument, both values are tabulated, the average value is taken and the performance of each air filter is estimated. Efficiencies in both new and used air filters are compared at the end and the better air filter is recommended for increased performance. In the laboratory test using the Met One particle counter values, the equivalent performance of each air filter is calculated on the basis of the different particle sizes 0.3 ,0.5, 1.0, 3.0, 5.0 and 10 µm and the results are tabulated. Measure each filter at three air velocity/flow values equivalent to the velocity/flow rate used in the car tests. But in the lab test no concentration was measured before the filter: Instead, measurements were made without a filter in the box (representing the upstream concentration value). Then measurements were made with the various filters in the box. Adjust the desired air velocity for each filter. Repeat tests until consistent results are obtained. This was made first for one of the speed stages, then for the second, and finally for the third level. The particle measuring position is in the middle of the circular duct after the filter box in the test rig. 14 4. Methods Figure 4.3: Lab-Setup (Test Rig) Figure 4.4: Lab-Setup (Test Rig) 15 4. Methods Figure 4.5: Metallic box(Test Rig) 4.2 Measurement instruments 4.2.1 Condensation particule conter (P-Trak) The P-Trak is a handheld device used to detect airborne particles. The instrument measures particles from about 0.02 µm to 1 µm, but the vast majority of the particles are below 0.1 µm in size (ultrafine), particularly when the particle content of the air is infused by source of combustion. 16 4. Methods Figure 4.6: Condensation particule conter (P-Trak) 4.2.2 Optical particle counter (Met One) Met one Particle counter is a portable instrument used to determine particle count based on a wide variety of particle sizes 0.3, 0.5, 1.0, 3.0, 5.0, 10 µm from the emission source. The Met One device is very useful in measuring the efficiency of air filters based on each particle sizes as mentioned above. 17 4. Methods Figure 4.7: Optical particle counter (Met-One) 4.2.3 Gas analyser (Brüel Kjaer) The Brüel and Kjaer Multi-Gas Detector will simultaneously test different gases in consecutive samples of air taken with a thee interval of approximately 1-2 minutes. Such gases seen by the gas analyser are the total concentration of aldehydes (cali- brated for acetaldehyde), carbon dioxide, Total Organic Carbon (TOC) and Water Vapor. In the gas analyser, these gases are represented symbolically as shown in the table 4.1. Figure 4.8: Gas analyser 18 4. Methods Table 4.1: : Gases measured by the Brüel Kjaer 1302 gas analyser. Symbol Gas Unit A Acetaldehyde ppm D Carbon dioxide ppm E TOC ppm W Water Vapour Tdwe 4.2.4 Air velocity and pressure differential instrument (Anemometer) Swema air 300 is an instrument used to measure the air velocity and pressure differ- ential with separate sensors attached to the instrument. This instrument was used for measurement of the pressure drop and face velocity of the tested filters, as well as the air flow rate in the test duct of the test-rig. Figure 4.9: Air velocity and pressure differential instrument type Swema Air 300. 19 4. Methods 20 5 Results Results for filtration efficiencies of different air filters and air purification devices are presented, along with input and output data obtained from lab test and in car test. 5.1 Example of results for in-car testing In this section, test results for air filter A/F-1, obtained from the in-car testing, are presented. Table 5.1 shows the particle count before and after the air filter together with the calculated filtration efficiency. The average efficiency based on five consec- utive measurements is presented. The procedure was repeated for a total of three fan speeds, corresponding to three different air flow rates. The entire procedure described above was repeated three times, each repetition named Trial-1, Trial-2 and Trial-3. The efficiency values from each of the three trials and the grand average are shown in Table 5.2. The experiments, Trial-1, Trial-2 and Trial-3, were then repeated for all five different air-filters. The final result from all trials and all filters are presented under a separate heading last in this chapter. 21 5. Results Table 5.1: Values taken for air filter A/F-1 in the car - Trial 1 using the P-Trak Speed Average Air flow rate (l s−1) Tr No Before A/F After A/F Efficiency Average (%) 1 30.2 1 3960 888 0.77 74 2 3690 925 0.74 3 3310 879 0.73 4 3070 855 0.72 5 2910 815 0.71 3 60 1 3160 982 0.68 65 2 2930 1080 0.63 3 2890 1050 0.63 4 3140 1070 0.65 5 2890 1030 0.64 7 115.2 1 3160 1660 0.47 48 2 3040 1710 0.43 3 2990 1650 0.44 4 2930 1450 0.50 5 2810 1360 0.51 Table 5.2: Average efficiencies of air filter A/F-1 in the car obtained from all three trials for ultrafine particles using the P-Trak instrument. Average Airflow Rate (l s−1) Efficiency (%) Average (%) 30.2 74.02 7470.97 76.2 60 65.2 6768.44 66.21 115.2 47.63 5152.98 53.19 22 5. Results In addition to particle measurements, the concentration of gases was also measured inside and outside the car. The gases include aldehydes, carbon dioxide, TOC and water vapor. Table 5.3 shows the concentrations measured for filter A/F-1 during Trial-1. Average gas concentrations calculated for all three trials are shown in Table 5.4. Table 5.3: Measured gas concentrations for air filter A/F-1 during Trial 1. Symbols A D E W Scenario Acetaldehyde (ppm) Carbon- dioxide(ppm) TOC (ppm) Water Vapour (Tdwe) Outside the Car 0.0024 521 2.65 4.03 0.0033 521 2.74 3.97 0.0031 520 2.85 4.02 0.0030 531 2.97 3.96 0.0032 524 2.80 4.15 Average 0.0030 523 2.8 4.0 Inside the Car 0.0027 522 2.85 4.04 0.0030 523 2.91 4.06 0.0032 527 2.94 3.99 0.0029 526 2.96 3.95 0.0032 527 2.92 4.00 Average 0.0030 525 2.92 4.01 Table 5.4: Average gas concentration based on all three trial of filter A/F-1 in the car Gases Outside the car (concentration) Inside the car (concentration) Acetaldehyde (ppm) 0.0029 0.0030 Carbon-dioxide (ppm) 539 544 TOC (ppm) 3.25 3.16 Water Vapour (Tdwe) 3.85 3.91 23 5. Results 5.2 Example of results from lab-testing In this section, results from the test-rig measurements are presented. Table 5.5 presents the results obtained when testing filter A/F-1 with respect to ultrafine par- ticles with the P-Trak. Measurements were made with and without the air filter inside the test rig. The efficiency values were determined by comparing these con- centrations; the concentration without filter representing the upstream value, and the concentration with the filter representing the downstream value. The measure- ments were repeated for the three air velocities shown in the table, each representing the same fan speeds as shown in Table 5.1, above. In the same way, the experiment were done for all five different air-filters, each consisting of 3 sets of Trials named Trial-1, Trial-2 and Trial-3. The results from all trials of filter A/F-1 are shown in table 5.6, which contains the average efficiency values for all three trials and eventually the average efficiency value. The final result from all trials and all filters are presented under a separate heading last in this chapter. Table 5.5: Values taken in the test-rig for filter A/F-1. Trial 1 using the P-Trak.) Average Air ve- locity(m s−1) Tr No Without A/F With A/F Efficiency Average (%) 1.5 1 55000 14100 0.74 73 2 53200 14000 0.73 3 50000 13500 0.73 4 49600 12900 0.73 5 48400 12800 0.73 2.99 1 58500 28300 0.51 56 2 53400 25100 0.53 3 50300 23500 0.53 4 47300 20200 0.57 5 42500 18300 0.56 5.73 1 61000 19800 0.67 56 2 45700 17700 0.61 3 35300 15600 0.55 4 26900 13400 0.50 5 21300 11680 0.45 24 5. Results Table 5.6: Average efficiencies for ultrafine particles (P-Trak) of air filter A/F-1 in the test-rig. Data from all three trials using. Average Airflow Rate (m s−1) Efficiency (%) Average (%) 1.5 73.72 7372.87 73.67 2.99 54.43 5658.77 55.09 5.73 55.99 5656.14 54.81 25 5. Results 5.3 Final efficiency values for ultrafine particles Table 5.7 shows the final average efficiency results for all five air-filters when tested in the car for ultrafine particles using the P-Trak. Table 5.8 shows the corresponding results for the same filters when tested in the lab test-rig. Table 5.9 shows the dif- ference between the results in the previous tables expressed as efficiency percentage- units (%). Table 5.7: Final average efficiency results for all five air filters when tested in the car for ultrafine particles using P-Trak Air flow (l/s) A/F-1 A/F-2 A/F-3 A/F-4 A/F-5 30.2 74 76 80 79 68 60 67 72 75 76 62 115.2 51 62 61 65 44 Table 5.8: Final average efficiency results for all five air filters when tested in the lab test-rig for ultrafine particles using P-Trak Air flow (m/s) A/F-1 A/F-2 A/F-3 A/F-4 A/F-5 1.5 73 84 90 65 62 2.99 56 54 59 60 50 5.73 56 49 53 47 45 Table 5.9: Difference (%) between efficiencies obtained in the car and in the lab test-rig. Results for ultrafine particles measured using P-Trak. (%)Difference A/F-1 A/F-2 A/F-3 A/F-4 A/F-5 1 1 -11 -13 18 9 2 16 25 21 21 19 3 -10 21 13 28 -2 5.4 Efficiency values for particles larger than 0.3 µm The values obtained from the MetOne particle counter are seen in Table 5.10, 5.11 and this experiment is carried out in the same manner as the previous approach for evaluating the performance of the air filters, i.e. measurements made with an air filter inside the test rig and without an air filter inside the test rig. For each air filter, several samples were taken with and without filter. Figure 5.10 shows the 26 5. Results concentration values measured and Table 5.11 shows the calculated filter efficiency values of each particle size for all the various filters. An average efficiency value could be calculated for each filter and each air velocity. However, the table shows only the individual efficiency values determined. Figure 5.1: Particle concentration measured with the MetOne particle counter for all five filters, at three different air velocities in the lab test -rig. Concentration values presented as particle number per cubic feet (p/ft3) Without Filter With Filter Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm 1.5 262932 28453 10796 243 78 2 1.5 68256 4583 1526 38 0 0 2.99 237936 22781 9285 315 84 2 2.99 141839 8513 1824 35 3 0 2.99 188787 13884 5682 219 72 3 2.99 119575 6347 1381 36 6 0 2.99 171432 10875 4438 185 85 10 2.99 105776 5369 1194 14 6 0 5.73 113337 25508 8108 208 112 29 5.73 56171 11409 2522 52 11 6 5.73 125862 24104 7173 218 84 16 5.73 47922 10324 2162 25 13 2 5.73 129726 23689 7040 196 70 6 5.73 45099 10121 2013 29 7 0 Without Filter With Filter Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm 1.5 449962 58507 16089 259 72 1 1.5 125350 11996 2554 23 9 0 1.5 346533 41862 11800 198 49 3 1.5 102608 9157 2050 26 7 0 1.5 260625 28825 8675 103 47 0 1.5 84881 7457 1544 27 9 0 2.99 165108 9713 3326 161 60 3 2.99 111323 6447 1598 26 3 0 2.99 154760 8822 3481 222 72 3 2.99 83382 4130 1063 41 11 1 5.73 73711 22100 6554 143 83 4 5.73 47383 10947 1941 22 8 0 Without Filter With Filter Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm 1.5 357230 25162 7156 322 150 4 1.5 53150 3518 1096 55 16 0 1.5 261569 20851 7392 374 148 9 1.5 43593 2927 954 36 15 2 1.5 207315 17141 7039 448 206 4 1.5 37782 2629 875 37 24 0 2.99 142687 10305 4795 237 102 4 2.99 77912 6539 2295 61 17 0 2.99 129861 8610 3853 205 91 5 2.99 66891 5066 1842 55 15 0 2.99 131432 8726 3653 204 70 3 2.99 58403 3686 1310 43 20 0 5.73 69828 20479 5520 107 54 6 5.73 53997 8166 1589 22 6 3 5.73 68276 19958 5403 94 48 1 5.73 30909 5529 1007 9 3 0 Without Filter With Filter Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm 1.5 140305 7267 1793 74 24 1 1.5 79074 2944 683 21 20 2 1.5 123453 5859 1542 45 16 2 1.5 69631 2683 620 20 3 0 2.99 154776 9180 3384 198 49 3 2.99 123467 5580 1215 29 7 0 2.99 149009 7762 3144 165 79 5 2.99 114024 4169 887 15 9 0 5.73 67619 13862 4316 120 47 7 5.73 27913 3781 688 37 26 3 5.73 48019 11835 3566 83 53 1 5.73 25194 3430 611 16 3 1 5.73 43110 11387 3288 91 40 7 5.73 24081 3166 574 8 1 0 Without Filter With Filter Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm Speed (m/s) 0.3 - 0.5 µm 0.5 - 1 µm 1 - 3 µm 3 - 5 µm 5 - 10 µm >10 µm 1.5 947393 297137 90017 838 140 1 1.5 964866 103729 18597 174 31 3 1.5 1084673 233903 56283 532 113 7 1.5 790611 70712 12650 127 35 1 1.5 1089353 167609 35911 383 88 2 1.5 633329 49954 8996 116 25 0 A/F-4 A/F-4 A/F-5 A/F-5 A/F-3 A/F-3 A/F-1 A/F-1 A/F-2 A/F-2 27 5. Results Table 5.10: Filtration efficiency values determined for the five filters at three different air velocities in the lab test-rig Filter A/F-1 Speed (m/s) 0.3-0.5µm 0.5-1µm 1-3µm 3-5µm 5-10µm >10µm 1.5 74% 84% 86% 84% 100% 100% 2.99 38% 56% 76% 88% 94% 100% 5.73 59% 57% 70% 83% 88% 100% Filter A/F-2 Speed (m/s) 0.3-0.5µm 0.5-1µm 1-3µm 3-5µm 5-10µm >10µm 1.5 70% 77% 83% 84% 85% 100% 2.99 46% 54% 69% 85% 88% 100% 5.73 34% 51% 69% 85% 90% 100% Filter A/F-3 Speed (m/s) 0.3-0.5µm 0.5-1µm 1-3µm 3-5µm 5-10µm >10µm 1.5 83% 86% 86% 88% 89% 100% 2.99 56% 58% 64% 79% 79% 100% 5.73 39% 66% 76% 85% 90% 100% Filter A/F-4 Speed (m/s) 0.3-0.5µm 0.5-1µm 1-3µm 3-5µm 5-10µm >10µm 1.5 44% 57% 61% 64% 81% 100% 2.99 - - - - - - 5.73 - - - - - - Filter A/F-5 Speed (m/s) 0.3-0.5µm 0.5-1µm 1-3µm 3-5µm 5-10µm >10µm 1.5 - 68% 77% 75% 73% 100% 2.99 - - - - - - 5.73 - - - - - - 28 6 Summary and Conclusions The results and conclusions of the measurements are summarized below: • As expected, it can be inferred that, at lower air flow rates (low air velocity through the filters), the efficiency of all filters is higher than at higher airflow rates. • It was found that the new filter with active carbon (A/F-2) reduced organic compounds measured as aldehydes and total organic compounds (TOC) some- what, while there was no substantial reduction of gasses in any other filter. • Filter A/F-3 in both scenarios (in-car and lab test-rig tests) showed somewhat higher particle removal efficiency values compared to the other filters. This means that the new/unused air filter without active carbon typically showed somewhat higher particle filtration efficiency values than the used filters and the filters with active carbon. • Filters A/F-4 and A/F-5, showed lower particle removal than the other filters. These two filters had been in use for about 30,000 km which is substantially longer than the third used filter (A/F-1, 7,500 km). • The used filters had substantially higher pressure drops than the new filters. • Air-purification machines such as air-ionizer, plasma generator and ozone gen- erator were tested in the car cabin. There was no added air cleaning effect from these devices, i.e. thy did not contribute to any air quality improvement. • The tests using the ozone generator in the car cabin showed a substantial in- crease of the ozone concentration. The ozone concentration remained high for an extended period of time even after the ozone generator had been shut off. Ozone is a known health hazard and should not be generated in spaces for human occupancy. 29 6. Summary and Conclusions 6.1 Final remarks The measurements indicate higher performance for the new filters than the used. One of the used filters had quite a low mileage (7,500 km). This filter clearly per- formed better than the other two used filters, which had substantially higher mileage (30,000 km). It is suggested that future tests comprise testing of used filters with various mileages fairly evenly distributed over a relevant span. This is needed in order to determine in detail how the performance degrades with increasing mileage. Among the filters with active carbon, it was only the new one that showed any measurable reduction of organic gases. Thus, there seems to be too little carbon in the filter for any extended gas filtration efficiency. 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Appendix 1 Average Airflow Rate (l s−1) Efficiency (%) Average (%) 30.2 82.00 79.374.54 81.34 60 81.10 76.4171.54 76.60 115.2 72.38 64.8656.81 65.39 Table A.3: Average efficiencies of Air filter 4 with Active Carbon (old-1) Average Airflow Rate (l s−1) Efficiency (%) Average (%) 30.2 79.31 68.2063.11 62.18 60 68.04 61.8658.69 58.86 115.2 45.64 44.1145.06 41.62 Table A.4: Average efficiencies of Air filter 5 with Active Carbon (old-2) Gases Outside the car (concentration) Inside the car (concentration) Acetaldehyde (ppm) 0.0029 0.0021 Carbon-dioxide (ppm) 547 557 TOC (ppm) 2.7 2.09 Water Vapour (Tdwe) 6.46 6.46 Table A.5: Average gas concentration for Air filter 2 with Active Carbon (New) II A. Appendix 1 Gases Outside the car (concentration) Inside the car (concentration) Acetaldehyde (ppm) 0.0032 0.0035 Carbon-dioxide (ppm) 598 597 TOC (ppm) 3.40 3.55 Water Vapour (Tdwe) 6.00 5.99 Table A.6: Average gas concentration for Air filter 3 without Active Carbon (New) Gases Outside the car (concentration) Inside the car (concentration) Acetaldehyde (ppm) 0.0029 0.0027 Carbon-dioxide (ppm) 527 524 TOC (ppm) 3.18 3.32 Water Vapour (Tdwe) 9.31 9.29 Table A.7: Average gas concentration for Air filter 4 with Active Carbon (old-1) Gases Outside the car (concentration) Inside the car (concentration) Acetaldehyde (ppm) 0.0028 0.0025 Carbon-dioxide (ppm) 593 585 TOC (ppm) 3.71 3.43 Water Vapour (Tdwe) 9.23 8.22 Table A.8: Average gas concentration for Air filter 5 with Active Carbon (old-2) III A. Appendix 1 A.1 Results for Air-Ionizer and Plasma Genera- tor Test results of Air-ionizer and Plasma generator done in the earlier stages of the thesis with different air flow rate and different efficiency results. A.2 Efficiency Results for Air-Ionizer and Plasma Generator Figure A.1: Lab test efficiency results Figure A.2: Car test efficiency results IV A. Appendix 1 Figure A.3: Different fan speed results Figure A.4: Different fan speed results V A. Appendix 1 A.3 Air Filters Used Following Figures shown below are the Air filters used in this Thesis project. Figure A.5: Air filter 1 Figure A.6: Air filter 2 VI A. Appendix 1 Figure A.7: Air filter 3 Figure A.8: Air filter 4 VII A. Appendix 1 Figure A.9: Air filter 5 VIII List of Figures List of Tables Introduction Aim of this work Outline of the present work Limitations Airborne pollutants Tested Objects Air filter with Active carbon coating Air filter without Active carbon coating Air ionizer Plasma generator Ozone generator Methods Test set-ups Method’s used for testing in car efficiency Method's used for testing Efficiency in LAB Measurement instruments Condensation particule conter (P-Trak) Optical particle counter (Met One) Gas analyser (Brüel Kjaer) Air velocity and pressure differential instrument(Anemometer) Results Example of results for in-car testing Example of results from lab-testing Final efficiency values for ultrafine particles Efficiency values for particles larger than 0.3 µm Summary and Conclusions Final remarks Bibliography Appendix 1 Results for Air-Ionizer and Plasma Generator Efficiency Results for Air-Ionizer and Plasma Generator Air Filters Used