• 한국대기환경학회지
• /
• 제23권6호
• /
• pp.689-698
• /
• 2007

Particular attention is paid to the validity of PM-10 measurement using beta attenuation method. In this study, the inter-comparison studies were undertaken for PM-10 sampler with different measuring methods. The three beta attenuation monitoring instruments (BAM1020, FH C-14, and DIGS-150) and filter based gravitational method using High Volume Air Sampler were collocated and mass concentrations were compared from August to November, 2006. The results of the investigation show that beta attenuation monitoring instruments are comparable with gravitational method within 10% of measurement error. For specific conditions under high humidity and high concentrations, the inter-comparison results also showed a relatively good agreement and this can be explained as the effect of inlet heating of beta attenuation instrument. Subsequently, this study shows that beta attenuation monitoring instruments can be equivalently used with reasonable validity when compared gravimetric method.

• 설비공학논문집
• /
• 제11권4호
• /
• pp.472-483
• /
• 1999

The evaporation heat transfer and pressure drop characteristics for HFC-l34a in flat plate type heat exchangers with enhanced beads were experimentally investigated. Three plate type evaporators with different geometric condition of U-turn area were tested. Mass fluxes were tested over the range of 83kg/$m^2$s to 166kg/$m^2$s, and heat fluxes were varied from 4㎾/$m^2$ to 12㎾/$m^2$. Evaporation temperature was 5$^{\circ}C$ with inlet qualities of 0.1 to 1.0. There was no notable difference in the heat transfer coefficient by geometric variation of U-turn area, but the third plate with cross-ribbed channel at U-turn area was better than others in the evaluation using volume goodness factor comparison. Also, the mixtures of HFC-l34a and PAG oil was tested to determine oil effects on heat transfer and pressure drop. As oil concentration was increased, heat transfer coefficient was increased by 22~48% up to the 3wt.%, but decreased by 14~22% at the 4wt.%. The pressure drop was increased by the maximum of 100% as oil concentration was increased.

• 한국환경과학회지
• /
• 제8권1호
• /
• pp.27-32
• /
• 1999

This study identified concentrations of all pollutants emitted from idling of vehicles such as cars, taxis, trucks, and buses. In this investigation we analyzed concentrations of $SO_2$, NOx, CO, and $CO_2$ omitted from exhaust pipe of vehicles as a function of vehicle type, mileage, exhaust volume, and fuel type using the GreenLine. Compact or light cars, which have relatively low exhaust volume, showed much higher exhaust concentrations of $CO_2$, CO, and NOx than those emitted from vehicles with high exhaust volume. Vehicles using light oil showed much higher exhaust NOx concentrations than those of vehicles using gasoline. Vehicles using LPG and compact cars showed very high exhaust CO concentration compared to other vehicles. NOx exhaust concentrations were increased with increasing the mileage of vehicles.

• 한국대기환경학회지
• /
• 제5권1호
• /
• pp.68-78
• /
• 1989

The heavy metal of suspended particulates with human health has long been studied in environmental interest concerned. This study was intended to identify harmful heavy metals of the ambient air borne dusts which were related with the respirable sizes in the aerodynamics. Two sampling sites were selected comparatively; one was in the Shinchon area, which is the commercial district with heavy traffic and the other site was in the Bulgwang area which is residential area. The supended particulates were sampled by high volume air sample with 6 cascade impactor stages. The heavy metals in terms of As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn were determined by stomic absorption spectrometry or inductively coupled plasma emission spectrometry. The samples weretaken bimothly for seven consecutive days from May 1987 to March 1988. The annual average concentration of the respirable suspended dust of which diameter is less than 10$\mum$ was 152.59 $\mug/m^3$ of the Shinchon air samples; the respirable dust was equivalent to approximately 85% of the total suspended particulates. The annual average concentration of the respirable suspended dust of the Bulgwang air samples was 112.56 $\mug/m^3$; that was approximately 86% of the total suspended particulates. The concentration of heavy metals was investigated in relation to the particle size. The concentration of Cr, Fe, Mn and V were tended to be much more in the coarse particles than in the fine particles. Cd and Pb in the fine particles were more than in the coarse particles. In the partial correlation coefficients; in the Shinchon area, high correlations among Fe, Se and Mn were determined; it is assumed that those sources would be originated from coal, gasolineand diesel. In Bulgwang area, would be high correlation among Fe, Se, Hg and Mn considered to be originated from coal, Bunker-C and heavy oil as well. From the above results, the hazardous heavy merals in air should be measured and controlled in originally their sources.

• 한국물환경학회지
• /
• 제20권1호
• /
• pp.86-92
• /
• 2004

Lab-scale experiments have been carried out to investigate ammonia stripping with a modified spray tower for removing ammonia nitrogen from swine wastewater. The operating conditions such as initial pH, temperature, air flow, hole size of distributor determining the diameter of water drops, and influent solids concentration were closely examined focusing on removal efficiency of ammonia. As a result of the experiment, in order to achieve high rate of ammonia removal by the air stripping system, the air flow rate must be supplied at high rate with sufficiently high initial pH, temperature. The optimum operating condition to meet the residual ammonia concentration of 300 mg/L was the initial pH of 11.0 at $35^{\circ}C$ with the air flow rate of 20 L/min. It also showed that the smaller hole size is, the higher removal rate of ammonia is expected. However, when used a small sized distributor (2 mm), the flooding problem at the upper column occurred due to clogging of the hole. With regard to the influent solids concentration, it was showed that the lower concentration of solids, the higher removal rate of ammonia. The removal of particulate materials in influent led to improve the removal efficiency of ammonia, rather than to control the operating condition including initial pH, temperature, and air flow. The empirical correlation between KLa and operating parameters would be driven as, $K_{La}=(0.0003T-0.0047){\cdot}G^{0.3926}{\cdot}L^{-0.5169}{\cdot}C^{-0. 1849}$. The calculated $K_{La}$ from proposed formula can be used effectively to estimate the optimum reaction time and to calculate the volume of modified spray tower system.

• 센서학회지
• /
• 제27권3호
• /
• pp.199-203
• /
• 2018

In this study, we develop a methane sensor module that can detect low concentrations below 5,000 ppm and measure up to the detection limit of 50 ppm with the NDIR method, with a long lifetime and high accuracy. Methane ($CH_4$) is one of a representative greenhouse gas, which is very explosive. Thus, it is important to quickly and accurately measure methane concentration in the air. To adjust the methane sensor for industrial field applications, a NDIR-based small sensor was implemented and characterized, where its volume was $4cm{\times}4cm{\times}2cm$ and its response time ($T_{90}$) was less than 30 sec. These results demonstrate that the proposed sensor is commercially available for low-concentration measurement, low volume, and fast response application, such as IoT sensor nodes and portable devices.

• 한국대기환경학회지
• /
• 제23권4호
• /
• pp.466-477
• /
• 2007

To understand particle pollution phenomena caused by vehicles, black carbon (BC) concentrations were continuously monitored using an aethalometer at a roadside in Seoul during the period of May 79 to 25, 2005. The BC concentration was highly fluctuated for a short duration, responding to the traffic situation on the road. The lowest BC concentration was observed between 2 and 5 a.m. The local highest BC concentrations were observed during the periods of both morning and evening rush hours. Change in traffic volume accounts for the trend of hourly averaged BC concentrations from the late evening to the morning. Particularly, the slower increase of BC concentration on Sunday seems to respond directly the lower traffic volume in the morning rush hours. From the comparison with a previous work, it is concluded that the BC concentration around midday hours might be dependent on the distance from a road.

• 대한기계학회논문집B
• /
• 제26권3호
• /
• pp.402-409
• /
• 2002

Experiments were performed with double-concentric diffusion flame(DDF) in order to investigate the characteristics of soot formation and temperature distributions. The flame size and shape of the DDF are similar to those of the well-known normal co-flow diffusion flame(WF), except the formation of a tiny inverse flame near the central tube exit. A laser light extinction technique was used to measure the soot volume fractions. The temperature distributions in the flame were measured by rapid insertion of a R-type thermocouple. Soot concentrations along the flame axis of the DDF were higher than those of the NDF. However, the maximum soot volume fraction of the DDF along the periphery of the flame was lower than that of the NDF. It is mainly due to the effect of nitrogen-dilution from the inner air. Measured temperature distribution explains these trends of soot concentration. The temperature along the flame axis was also higher in DDF than that of the NDF. However, the flame temperatures at the flame front of the two flames were almost same regardless of the inner flame. This phenomenon means that the inverse flame inside the DDF did not affect on the flame structure including the temperature and soot concentration, except the region around the flame axis.

• 한국환경보건학회지
• /
• 제25권3호
• /
• pp.51-57
• /
• 1999

This study was carried out to investigate the concentrations of Ni, Cr and Cu, to analyze the correlations among those, and between concentrations and traffic volumes by type of car in roadside ambient air at Chongro-, Chungkechon- and Kangnam terminal- area in Seoul from October 1st to October 31st in 1997. The results were as follows ; 1. The means of concentrations of Ni in roadside ambient air were 34.1, 25.1 and 23.6 ng/m$^3$ at Chungkechon, Kangnam terminal and Chongro area, respectively. The highest concentrations of Ni by time were 26.8 in the evening, 45.5 in the evening and 49.4 ng/m$^3$ in the forenoon at Chongro, Chungkechon and Kangnam terminal area, respectively. 2. The means of concentrations of Cr in road side ambient air were 97.7, 80.1 and 70.9 ng/m$^3$ at Chong, Chungkechon and Kangnam terminal area, respectively. The highest concentrations of Cu by time were 205.3 in the evening, 114.4 in the evening and 92.3 ng/m$^3$ in the forenoon at Chongro, Chungkechon and Kangnam terminal area, respectively. 4. The tendencies of concentrations of Ni and Cr by time were similar to each other. Especially, at Kangnam terminal area, correlation coefficients between concentrations of Ni and Cr and the traffic volume of bus were high(r=0.997,0.975). 5. The tendency of concentration of Cu and the traffic volume of passenger car at each area were high(r=0.832, 0.968) 6. Correlation coefficients between Cu and Zn, and between Ni and Cr were 0.762 and 0.842, respectively. This means that the possibility of co-existence of Cu-Zn or Ni-Cr is very high.

• 한국환경보건학회지
• /
• 제42권2호
• /
• pp.102-111
• /
• 2016

Objectives: This study was conducted to evaluate the use of polyurethane foam disk passive air samplers (PUF PAS) for better measurement of atmospheric polychlorinared dibenzo-p-dioxins/furans (PCDD/Fs) concentrations compared to PUF PAS combined with high volume air samplers (HVS). Methods: Air samples were collected by a low volume air sampler (LVS) and PUF PAS. A total of two pairs were continuously collected for six months, but the PUF was replaced every two months. Results: A good correlation was shown ($R^2=0.8595$, p<0.0001) between atmospheric PCDD/Fs concentration measured by the LVS and PUF PAS. The average air sampling rate ($1.5m^3/day-sampler$) of all PCDD/Fs congeners showed a middle of the means which were measured using a HVS by other researchers in different cities. In addition, the air sampling rates of the LVS for each congener made less difference than did those of the HVS. Conclusion: It was found that measurements using the LVS were less influenced by atmospheric peak PCDD/Fs concentrations. However, trace POPs such as PCDD/Fs may involve relatively large analytical errors in measurement, and as a result the air sampling rate of the respective PCDD/Fs isomer is also likely to involve errors. The method of using a regression straight line between the concentrations obtained from the LVS and those from the PUF PAS was judged higher than the method using the air sampling rate, since the former compensated for the experimental errors in the process of evaluation of atmospheric PCDD/F concentrations using the PUF PAS.