Earticle

In this study, the cooling capacity and the pressure drop of a condenser for 10kW refrigerator unit were experimentally investigated. The performance characteristics of the condenser was studied by changing the fin shape(4 types), fin pitch(5 types), tube row(4 types) and air flow rate(6 types), using the calorimeter. The optimum heat exchanger specifications were selected by comparing the capacity and the pressure drop of the condenser. In order to select the heat exchanger suitable for the condenser for 10kW refrigerator unit, both the cooling capacity and the pressure drop should be considered. From the condenser performance test by pin type, the wavy pin was selected. The optimal performance of the condenser for 10kW refrigerator unit was observed at the fin pitch of 3 mm, the tube row of 4 row, and the air flow rate of 90㎥/min.

This study reconstructed the actual fire scene and studied the risk of low-temperature ignition in the insulation material due to the heat generated when compressed refrigerant gas moves from the compressor to the condenser of the refrigerator. In addition, when the refrigerator door is open, the thermal change pattern of each part of the condenser over time was compared and analyzed. As a result of the experiment, considerable heat was generated in the process of moving from the compressor to the condenser, and when the refrigerator door was forcibly opened, the heat continued to accumulate, and it was found that the low-temperature accumulation in the insulation material could cause ignition. Through the results of this study, the ignition mechanism and fire detection options were derived to reconfigure and restore the fire scene in case of a fire due to heat storage while the refrigerator is opened.

An exergy analysis of cascade refrigeration system with R744 and R717 is presented in this paper to optimize the design and operating parameters of the system. The design for the operating parameters considered in this study include superheating and subcooling degree, cascade heat exchanger and compression efficiency, condensation and evaporation temperature in the R717 high temperature cycle and R744 low temperature cycle, respectively. The main results are summarized as follows : As the cascade evaporation temperature increases, the COP of R717 high temperature cycle increases. But the COP of R744 low temperature cycle decreases, and the COP of total cascade cycle is almost constant. As cascade evaporation temperature increase, the exergy loss in the R717 condenser and the R744 cascade heat exchanger is the largest and the lowest among all components, respectively. Therefore, in order to improve the COP of total cascade cycle and exergy efficiency() of cascade refrigeration system with R744 and R717, the exergy loss of the condenser and compressor of R717 must be reduced.

The blood preparation is important for management and classification. Because the work bench for sorting blood is not produced domestically, we have developed a work bench to classify blood through this study. Single coil system was developed to control cooling efficiency and temperature distribution. And evaporator and heater were used to reduce condensate discharge. This allow us to maintain a constant temperature and the condensation remainder below 1L. This study is expected to expand to other bio-equipment development.

Energy saving and decreasing green gas are critical issue today, so various technologies to save energy and decrease carbon dioxide in plant process have been applied to many industrial area. In this paper, the feasibility of condenser heat recovery in power plant was reviewed by verifying 에너지 평형 and simulating power plant model. Some ways to compose proper system and their possibilities were also reviewed. The amount of heating recovery and changed heating capacity were verified by simulation. There is noticeable improvement of plant performance in simulated result. Future study and experiment will show more evident results.

Hydrogen is an eco-friendly energy source and is being actively researched in various fields around the world, including mobility and aerospace. In order to effectively utilize hydrogen energy, it should be used in a liquid state with high energy storage density, but when hydrogen is stored in a liquid state, BOG (boil-off gas) is generated due to the temperature difference with the atmosphere. This should be re-condensed when considering storage efficiency and economy. In particular, large-capacity liquid hydrogen storage tank is required a gaseous helium circulation cooling system that cools by circulating cryogenic refrigerant due to the increase in heat intrusion from external air as the heat transfer area increases and the wide distribution of the gas layer inside the tank. In order to effectively apply the system, thermo-hydraulic analysis through process analysis is required. In this study, the condenser design and system characteristics of a gaseous helium circulation cooling system for BOG recondensation of a liquefied hydrogen storage tank were compared.

Superconducting high gradient magnetic separation (HGMS) has advantages to treat wastewater because it can generate high magnetic field and achieve rapid purification. In this study superconducting HGMS was applied to remove impurities from the condenser water in thermal power plant. The condenser water contained mainly hematite and maghemite and it was highly magnetized than hematite. In the HGMS tests using a 6-T cryo-cooled Nb-Ti superconducting magnet, the turbidity of the condenser water was effectively reduced up to 99.6% and the result showed better performance than that of the 0.5-T permanent magnet test. The higher magnetic field was applied in the range of 1-6 T, the more iron oxides were removed. The effect of magnetic filter configuration on the condenser water treatment was also investigated. Consequently superconducting HGMS system can be applicable to remove iron oxide impurities from condenser water in thermal power plant.

폐 탄탈륨 콘덴서에 함유된 탄탈륨 anode를 물리적인 방법으로 회수하고자 파쇄, 입도분리, 건식 자력선별 그리고 공기 분급 실험을 수행하였다. 단체분리를 위해 롤 크럿셔를 사용하여 폐회로 공정에서 8 mesh 이하로 파쇄하면, 대부분의 탄탈륨 anode는 레진과의 단체분리는 이루어지나 일부 금속과의 단체분리가 되지 않은 상태로 남게된다. 파쇄된 시료를 8/10 mesh, 10/18 mesh, -18 mesh로 분립한 결과, 금속물질은 8/10 mesh 입자에, 탄탈륨 anode는 +18 mesh에 주로 분포하며, -18 mesh에는 레진의 함량이 71.5%로 레진이 탄탈륨 anode나 금속물질보다 미립화가 쉽게 이루어짐을 알 수 있었다. 자력선별에 의한 금속 물질의 분리효율은 원료의 입도에 따라 크게 차이가 있으나, 일부 금속물질이 약자성체이거나 탄탈륨 anode와 단체분리가 이루어지지 않아 금속물질 제거율은 62.3%로 비교적 저조하였다. 탄탈륨 anode와 레진의 분리를 위한 입도별 공기 분급실험 결과, 각 입도별 최적 공기량은 각각 39 m3/h, 32 m3/h., 20 m3/h.로 나타났다. 최적의 조건으로 회수한 탄탈륨 anode의 생산율은 49.39 wt.%, 각 성분의 함량은 97.47 wt.%탄탈륨 anode, 0.9 3wt.%레진. 1.61 wt.%금속으로 탄탈륨 anode 실수율은 94.45%이었다.

Physical separation containing grinding, sieving, dry magnetic separation and air classification were carried out in order torecover Ta anode from waste Ta condenser. Rol crusher was used for the liberation of resin and metals in closed circuit system.when the waste condenser was crushed below 8mesh. When the crushed sample were divided into 8/ 10mesh, 10/ 18mesh and-18 mesh, metals was mainly remained in 8/1 0mesh in contrast to Ta anode was in + 18mesh. It was shown that resin was moreeasily crushed rather than metals from the result of that resin content was 71.5% in -18 mesh. The liberation eficiency was dif-ferent with the input size of the crushed sample and average efficiency was 62.3% due to the locked Ta anode particles. Theresults of air classification test for the crushed samples showed that optimal air flow are 39m3/h., 32 m3/h., 20 m3When the sample were separated with optimal condition, 94.45% Ta anode containing 97.47 wt.% Ta anode, 0.93 wt.% resin.1.61 wt.% metal was recovered with 49.39 wt.% yield.

폐콘덴서로부터 탄탈륨 음극을 회수하기 위하여 물리적 선별과, 염소가스와 사염화탄소를 이용한 기초 염화반응에 관한 연구를 수행하였다. Stamp mill을 이용한 파쇄, 요동테이블에서의 습식 비중선별 그리고 공기 분급을 통하여 탄탈륨 음극을 98% 회수할 수 있었다. 염소가스를 이용한 TGA분석에서 탄탈륨 음극의 최대 무게 감소는 60%였고, 사염화탄소에 의한 탄탈륨 음극의 염화반응은 탄탈륨 음극을 산화탄탈륨으로 변환한 후가 반응율이 높았다.

For recycling of tantalum from obsolete condenser, physical separations and chlorination of tantalum scraps with Cl2 and CCl4 were investigated. The recovery ratio of tantalum from obsolete condenser was 98% by using a multidisciplinary process of crushing by stamp mill, wet gravity separation by the shaking table, and air classification. In the chlorination reaction of non-oxidized Ta anode with Cl2, the highest weight loss ratio is at least 60%, while in the chlorination reaction of Ta anode with CCl4, the reaction rate for the oxidized Ta anode is faster than that of the non-oxidized Ta anode.

In this research, the heat and flow analysis in a condenser of vehicle HVAC system was investigated numerically regarding the different shapes of the condenser tube. The velocity, pressure, and temperature distribution of the test fluid(R-134A) inside the tube were numerically calculated for the optimum design of the condenser tube for two different length with four different inlet velocities. In addition, the local pressure and temperature distributions for total tube length were calculated and the variation of pressure drop of the R-134A with flow rate were also calculated numerically. The tube at case 1 with less curved elbows was determined for the better design than case 2 in the aspect of energy-effective shape of the condenser tube.

As the use of capacitors in electrical appliances and electrical control circuits increases, the related electrical fire is increasing. There are various parts such as resistors, coils, and capacitors that make up an electric circuit. Among them, the ignition of a capacitor with a temporary charging function is closely related to the structural characteristics of the capacitor. Capacitors can explode due to various reasons, and the high heat generated when they explode ignites the inflammable dielectric, which in turn burns the inflammable materials such as the surrounding electric wires and spreads into a fire. In this paper, the ignition mechanism is studied by conducting a reenactment experiment on the various probabilities that can be ignited in an electric capacitor, and the prevention measures to be applied to the fire prevention are presented.

The cascade refrigeration cycle system has been used mainly to obtain the ultra-low temperature. In this study, the effects of internal and outdoor temperatures at chamber on the heat capacity of fin-tube heat exchangers were examined. In addition, refrigerant line patterns as well as refrigerant type for cascade cycle were optimized. The results in this study show that the refrigerant line patterns have greater effect on the sensible capacity than the total capacity. Also, the condenser heat release rate for R717-R744 cycle varies the ratio of 46 % with outdoor temperature by comparing with that of 24% for R134a-R410a cycle.

Two-phase thermosyphons are devices that can transfer large amounts of heat flux with the boiling and condensation of the working fluid resulting from small temperature differences. A two-phase thermosyphon consists of the evaporators, an insulation unit, and the condensers. The working fluid inside the evaporator is evaporated by the heating of the evaporator in the lower part of the two-phase thermosyphon and the evaporated steam rises to the in the upper part to transfer heat in response to the cooling fluid outside the tube. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. The resultant condensed working fluid flows downward along the inside surface of the tube due to gravity. These processes form a cycle. In the present study, condensers with various insert devices of a loop type two-phase thermosyphon which is 480mm wide, 68mm long, and 1,000mm high was used. The heat transfer pipes in the loop type two-phase thermosyphon were 15mm in diameter and 1,000mm in length and 98 heat transfer pipes were installed in loop type two-phase thermosyphon. The inside of the condensers with various insert devices was composed of heat transfer pipes installed to increase the heat transfer surface area of the heating media in the heat transfer pipes condensers with various insert devices. Using refrigerant R134a as a working fluid for the loop type two-phase thermosyphon to conduct heat transfer performance experiments for changes in the temperature of the cooling air outside the condenser and changes in the mass flow rate. According to the results of the present experiments, as the spaces between internal discontinuous pins decreased, pressure drops increased. Changes in the temperatures at the outlet of the condenser were shown to be a little smaller. Therefore, it can be seen that as the spaces between internal discontinuous pins decreased, the heat transfer performance increased. As the temperature of the air flowing in the condenser with various insert devices increased, the condensation heat transfer rate of the thermosyphon increased. As the condenser with various insert devices refrigerant inflow temperature increased, the condensation heat transfer rate of the condensers with various insert devices of the thermosyphon heat exchanger increased.

Reactive power procurement has been identified as an important ancillary service. The cost characteristics must be able to recover the lost opportunity cost component of generator reaching the field limits and causes the decrease in its active power when the reactive demand in the system increases. The Synchronous condensers supply reactive power to maintain the voltage and reduce the burden on the synchronous generators. In this paper, the cost characteristics of reactive power support by the generator are proposed based on its capability chart. A non-linear optimization problem formulation is proposed to compute both real and reactive power nodal prices for pool electricity market model with hydro condenser. The marginal prices at each node have been determined for both real and reactive power considering the minimization of fuel cost, reactive power cost, and cost of condenser. The cost characteristics of reactive power have been determined based on the existing methods and the proposed method. The comparison of the results obtained with existing method is also provided. The results have been determined for IEEE 24 bus test system.