• Proceedings of the KSME Conference
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• 2001.11b
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• pp.806-811
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• 2001

Since the characteristics of combustion and pollutant in Diesel engines were mainly effected by the characteristics of in-cylinder gas flow and fuel spray, an understanding of those was essential to the design of the D.I. Diesel engines. The improvement of volumetric efficiency of air charging into combustion chamber is a primary requirement to obtain better mean effective pressure of an engine. Since parameters such as the air resistances in intake and exhaust flow passages, valve lift and valve shape influence greatly to the volumetric efficiency, it is very important to investigate the flow characteristics of intake and exhaust port which develops air motion in the combustion chamber. In this study, two approach methods were used for design intake and exhaust port; experiment and computation which were made by using steady flow test rig and commercial CFD code. This paper presents the results of an experimental and analytical investigation of steady flow through the prototype cylinder head ports and valves of the HHI's H21/32 HIMSEN Engine.

• Nuclear Engineering and Technology
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• v.32 no.4
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• pp.350-360
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• 2000

In Korea, the dose limits are reduced and are set at the ICRP-60 iimits. However, derived limits tabulated as MPC in air and water are still specified in Notice No.98-12. There are some discrepancies between the primary dose limits and MPCs in air and water. Therefore, in order to accept ICRP-60 recommendations fully, derived limits such as ALI, DAC, ECL for radiological protection against ionizing radiation based on ICRP-60 recommendations were calculated using modified methods of those of 10 CFR part 20, dose limits and committed effective dose coefficients of the Basic Safety Standards of the IAEA. The derived limits in this study were also compared with those prescribed in 10 CFR part 20 as well as MPCs of Notice No. 98-12 in order to analyze the impact of implementing derived limits on nuclear facilities. ECLs in air and water for the control of radioactive discharge into the environment in this study are shown to have lower values (i.e. more conservative), for most part, than those in Notice No. 98-12. Especially, for uranium elements, ECLs in water are approximately a magnitude in the order of two lower than those in Notice No.98-12.

• Journal of the Korean Society of Combustion
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• v.11 no.2
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• pp.1-6
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• 2006

This report presents a study of the development of an advanced coal nozzle used in burners to reduce unburned carbon (UBC) in a tangential coal-fired boiler. To understand the mechanism of UBC reduction, experiments using conventional burners were carried out to evaluate the effects of air injection velocity, coal fineness and over fired air (OFA) on combustion efficiency. It was confirmed that ignition of pulverized coal particles close to the burner is helpful toward the complete burn of residual carbon in fly ash. These efforts indicated the additional results that UBC was strongly dependent on the primary air velocity and coal fineness; especially that UBC dramatically decreased when the weight fraction of pulverized coal under $75{\mu}m$ was over 85 %. New coal nozzles, modified from conventional nozzles, were prepared and tested to improve the combustion efficiency. Some of these nozzles offered relatively lower unburned carbon than those of conventional burners and are referred to as HPFS (High Performance Flame Stability) coal nozzles.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.30-39
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• 2001

The direct injection into the cylinders has been regarded as a way of the reduction in fuel consumption and pollutant emissions. The spray produced by the high pressure injector is of paramount importance in DISI(Direct Injection Spark Ignition) engines in that the primary atomization process must meet the requirement of quick and complete evaporation, mixing with air and combustion especially to prohibit the excessive HC emissions. The interaction between air flow and fuel spray was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside the cylinder of the DISI engine. The direct Mie scattered and shadowgraph images presented the macroscopic view of the liquid sprays and vapor fields. The velocity and particle size of fuel droplets were investigated by phase doppler anenometer(PDA) system. The processes of atomization and evaporation with a DISI injector were observed and consequently utilized to construct the data-base for the spray and fuel-air mixing mechanism as a function of the flow characteristics.

• International Journal of Air-Conditioning and Refrigeration
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• v.6
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• pp.124-135
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• 1998

A thermodynamic cycle analysis is performed for refrigerator-precooled Linde-Hampson hydrogen liquefiers, including catalysts for the ortho-to-para conversion. Three different configurations of the liquefying system, depending upon the method of the o-p conversion, are selected for the analysis. After some simplifying and justifiable assumptions are made, a general analysis program to predict the liquid yield and the figure of merit (FOM) is developed with incorporating the commercial computer code for the thermodynamic properties of hydrogen. The discussion is focused on the effect of the two primary design parameters - the precooling temperature and the high pressure of the cycle. When the precooling temperature is in a range between 45 and 60 K, the optimal high pressure for the maximal liquid yield is found to be about 100 to 140 bar, regardless of the ortho-to-para conversion. However, the FOM can be maximized at slightly lower high pressures, 75 to 130 bar. It is concluded that the good performance of the precooling refrigerator is significant in the liquefiers, because at low precooling temperatures high values of the liquid yield and the FOM can be achieved without compression of gas to a very high pressure.

• Solar Energy
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• v.20 no.4
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• pp.17-24
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• 2000

Thermal performance of a SAAHPS (Solar and Ambient-air-assisted Heat Pump System) located in KIER is simulated with TRNSYS 14.2. The SAAHPS is composed of dual evaorators, each of which is used as a solar fluid heat source and an air fluid heat source. Polynomial coefficients data for the SAAHPS is supplied with Frigosoft, a program widely used for heat pump modeling. In general, collector area and storage volume are 2 key parameters in SAAHPS thermal performance. A parametric study is performed in this study to assess sensitivity of collector area and storage volume in SAAHPS. We concluded that firstly collector area and storage volume are the primary variables in SAAHPS thermal performance, secondly COP of SAAHPS is higher than that of conventional heat pumps. Therefore. collector efficiency can be enhanced swith SAAHPS during a heating season.

• 한국연소학회:학술대회논문집
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• 1998.10a
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• pp.79-84
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• 1998

In this paper we show design and operation of 1MWth pulverized coal combustion test facility. The test facility is consists of coal feeding system, furnace and flue gas treatment system. The furnace is equipped with a top-fired burner in order to avoid influence of gravity on the coal particles. There are two part of vertical(VP) and horizontal pass(HP) at furnace. We can measure temperature and species of coal flames in vertical pass. Also, there is horizontally arranged section where investigation regarding corrosion and deposit formation will be carried out. The burner of combustor was externally air staging burner(EASB) type made by IFRF. The pulverized high bituminous(Blair athol) coal from Australia was used as fuel, and the particle size less than 80 ${\mu}m$ was 83.4%. Overall excess air ratio was 1.2.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.870-878
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• 2003

The maintenance of thermal equilibrium between the human body and its environment is one of the primary requirements for health, wellbeing and comfort. For the effective control of indoor thermal environment, thermostat or humidistat is used. But, it is not sufficient to control the indoor thermal environment using only one or two parameters as human response for the indoor comfortable environment. So an environmental thermal index is required for the control of indoor thermal environment effectively. In this study, a PMV sensor has been developed which has integrated from various kinds of individual sensors for temperature, humidity, air velocity, radiant temperature. After applying the PMV and PPD equation, it is possible to monitor the indoor thermal environment with the sensor system, which is adopted to the circuit for optimization according to the human response with the metabolic rate and activities. The measurement was carried out to verify the performance of the integrated sensor system in comparison with existing measurement system, the PMV meter. As a result, the possibility of applying the PMV sensor to control the indoor thermal environment simultaneously was examined.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.10
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• pp.950-961
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• 2000

The objective of this study is to develop optimal alternative selection model for renewing building equipments system. Cost Breakdown Structure of LCC in HVAC systems are deduced from resonable data and factors. As for Cost Breakdown Structure of LCC in HVAC system, pertinent level, title, CBS number, and block number are determined efficiently. Especially, in addition to current cost factor, it is possible to make Cost Breakdown Structure using present worth method more clear. A model of POWER LCC ver 1.0 used to analyze primary cooling system, heating system, and air conditioning system are POWER LCC ver 1.0_/sub SYSTEM/ : C1+ C2- C3+ C4+ C5+ C6+ C7±C8+ C9- C10/sub -1/+ C10/sub -2/+ C10/sub -3/, and is implemented with consideration of Cost Breakdown Structure and their summation using present-worth method. It is programmed with one of scientific languages, MATLAB 5.3.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.14 no.1_2
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• pp.22-39
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• 1992

The purpose of this study was to evaluate hypernasality, nasal air emission, glottal stop, articulation disorder in patients with velopharyngeal incompetency(V.P.I.) and to analyze speech improvement after pharyngoplasty. In this study 61 patients with velopharyngeal incompetency were tested, and in patents with pharyngoplasty speech problems before pharyngoplasty were compared with those after pharyngoplasty. The results obtained are as follows : 1. There are few speech problems in pronouncing the vowel sounds. 2. There are many speech problems in pronouncing the pressure sounds and few speech problems in non-pressure sounds. 3. Speech problems in patients with cleft palate are influenced not by anatomical defect but by severity of velopharyngeal incompetence after palatorrhaphy. 4. Operation methods which decrease the velopharygeal incompetence must be considered for reducing the speech problems. 5. Among the 61 cases with V.P.I. 19 cases(31%) showed nasal air emission and 24 cases(39%) showed glottal stop. 6. Pharyngoplasty is of benefit to primary precipitating components such as hypernasality, nasal air emission but of no benefit to secondary compensating component such as glottal stop. 7. There as no significant difference in speech improvement between pre-and post-pharyngoplasty(p<0.05).