• Journal of Chest Surgery
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• v.39 no.7 s.264
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• pp.505-510
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• 2006

Background: Small animal cardiopulmonary bypass (CPB) model would be a valuable tool for investigating path-ophysiological and therapeutic strategies on bypass. The main advantages of a small animal model include the reduced cost and time, and the fact that it does not require a full scale operating environment. However the rat CPB models have a number of technical limitations. Effective maintenance and control of core temperature by a heat exchanger is among them. The purpose of this study is to confirm the effect of rectal temperature maintenance using a heat exchanger of cardioplegia system in cardiopulmonary bypass model for rats. Material and Method: The miniature circuit consisted of a reservoir, heat exchanger, membrane oxygenator, roller pump, and static priming volume was 40 cc, Ten male Sprague-Dawley rats (mean weight 530 gram) were divided into two groups, and heat exchanger (HE) group was subjected to CPB with HE from a cardioplegia system, and control group was subjected to CPB with warm water circulating around the reservoir. Partial CPB was conducted at a flow rate of 40 mg/kg/min for 20 min after venous cannulation (via the internal juglar vein) and arterial cannulation (via the femoral artery). Rectal temperature were measured after anesthetic induction, a ter cannulation, 5, 10, 15, 20 min after CPB. Arterial blood gas with hematocrit was also analysed, 5 and 15 min after CPB. Result: Rectal temperature change differed between the two groups (p<0.01). The temperatures of HE group were well maintained during CPB, whereas control group was under progressive hypothermia, Rectal temperature 20 min after CPB was $36.16{\pm}0.32^{\circ}C$ in the HE group and $34.22{\pm}0.36^{\circ}C$ in the control group. Conclusion: We confirmed the effect of rectal temperature maintenance using a heat exchanger of cardioplegia system in cardiopulmonary bypass model for rats. This model would be a valuable tool for further use in hypothermic CPB experiment in rats.

• Journal of the Korean Wood Science and Technology
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• v.37 no.1
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• pp.94-104
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• 2009

It is urgently required to develop the production of fermentation-heat energy from the waste agricultural and forest biomass and its effective heat exchanging system for the supply of warm water to rural households and greenhouses. In this study 3 helical-type and 1 plate-type heat exchangers using 3 different waste biomasses [e.g. hardwood (HW) sawdust (100%), softwood (SW) sawdust : HW sawdust (50 : 50) and HW sawdust : grass (90 : 10)] were applied in order to find out the best heat recovery system. The heat exchanger was basically considered to improve the overall heat recovery efficiency, to minimize heat loss and to simplify manufacturing, assembling and breaking up the fermenting beds. The helical-type heat exchanger (HX-H3) installed in fermenting bed of HW sawdust : grass (90 : 10) showed relatively higher temperature profiles, in particular mid- and upper-parts than lower and surface parts during 45-day fermentation process. The maximum temperature was ranged from $40^{\circ}C$ to $65^{\circ}C$ with average $60^{\circ}C$. The water temperature of tank outlet was ranged to $33{\sim}48^{\circ}C$ during whole measuring periods. By the way plate-type one (HX-P) installed in same biomass compositional fermenting bed showed $64.5{\sim}76.5^{\circ}C$ at center part, and $43{\sim}56^{\circ}C$ and $42{\sim}58^{\circ}C$, water tank and tank outlet temperatures, respectively, during 100 day measurement. It could be concluded that the plate-type heat exchanger (HX-P) provides not only the effective heating for the rural households and greenhouses, but also having the best heat recovery performance, easy manufacturing, assembling and breaking up the systems.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.10-17
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• 2002

The objective of performing this study is to develop low emission condensing gas boiler. To reduce NOx and CO, three reasonable distances between burner and heat exchanger were decided through the experiments of model plane burner. Three burners with different diameter were made and then emission characteristics were examined. The optimum burner geometry was determined from flame stability, pollutant emission characteristics and applicability to the practical boiler system. In the domain of equivalence ratio 0.68~0.85, turn-down ratio of the burner designed by this research was extended to a wider range of 5 : 1. Thermal efficiency of the boiler developed by this study reached to 97% (LHV basis) of heating water efficiency at heating load of 20,000 kcal/hr when fueled by both of LNG or LPG. Emission ($O_2$=0%, wet basis) of NOx and CO concentration was 26 ppm and 85 ppm when fueled by LNG, 41 ppm and 113 ppm when fueled by LPG respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.892-897
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• 2020

Previous plastic heat exchangers are expensive because the mold must be newly manufactured depending on the air conditioning space. On the other hand, danpla is so thin that the heat exchange performance is excellent. Moreover, danpla can be used easily in ventilation systems in view of fabrication. This study proposes correlations for the cooling performance of an indirect evaporative cooling system. The experimental apparatus consisted of a heat exchanger, spray nozzle, fan, thermostat, pump, and measuring sensors for temperature, humidity, and airflow rate. The results showed that the effectiveness decreased gradually as the airflow rate increased. In addition, there was an optimal condition in terms of effectiveness. The performance prediction correlations were determined using the experimental data from various conditions. The proposed correlations showed performance accuracies within 4 % error.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.6
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• pp.1959-1970
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• 1996

Effects of oscillatory flow upon heat transfer characteristics have been studied experimentally for oscillating flow in a circular tube. The experimental apparatus was designed to simulate the heat exchangers of the Stirling or Vuilleumier cycle machines and the test section consists of heater and cooler. Measurements were presented of heat flux, axial wall temperature distribution, and radial temperature profile of the working fluid for several cases of oscillation frequency and swept distance ratio. The influences of two main parameters, frequency and tidal displacement of the oscillation were investigated. Then the heat transfer coefficient at the heater is obtained. The carried by the authors with a assumption of oscillatory laminar slug flow.

• Journal of the Korean Geotechnical Society
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• v.30 no.7
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• pp.55-61
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• 2014

The need of geothermal energy is constantly increasing for economical and environmental utilization. Horizontal ground heat exchangers (GHEs) can reduce installation cost and increase efficiency. There are many kinds of GHEs, and it is known that slinky and spiral coil type GHEs show high thermal performance. Therefore, this paper presents experimental results of heat exchange rates in horizontal slinky and spiral coil type GHEs installed in a steel box whose size is $5m{\times}1m{\times}1m$. Dried Joomunjin standard sand was filled in a steel box, and thermal response tests (TRTs) were conducted for 30 hours to evaluate heat exchange rates by changing different pitch spaces of horizontal slinky and spiral coil type GHEs. As a result, spiral coil type GHE showed 30~40% higher heat exchange rates per pipe length than horizontal slinky type GHEs. Furthermore, long pitch interval (Pitch/Diameter=1) showed 200~250% higher heat exchange rates per pipe length than short pitch interval (Pitch/Diameter=0.2) in both spiral coil and horizontal slinky type GHEs, respectively.

• Journal of Energy Engineering
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• v.4 no.3
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• pp.420-428
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• 1995

현재 사용하고 있는 액화천연가스 기화기는 관내부로 -162$^{\circ}C$의 액화가스가 흐르고, 관외부로 발전소 증기응축기 출구에서 배출된 20~3$0^{\circ}C$의 해수를 흐르도록 하여, 두 유체사이의 온도차로 기화시키는 간접접촉방식 열교환기가 사용되고 있다. 그러나 간접접촉방식 열교환기는 두 유체사이의 큰 온도차로 인한 금속재료의 피로현상과 해수의 염분에 의한 재질의 부식 및 미생물 부착 등의 원인으로 열전달효율이 저하되고 있다. 따라서 본 연구는 관을 중간매체로 하는 간접접촉식 열교환기대신 액화천연가스와 기화용수인 물을 직접접촉시키는 방법으로 이용하여, 위와 같은 문제점들을 근본적으로 해결하려 한다. 본 실험에서는 기화기내의 수위 500 mm와 물의 유량 10 l/min을 일정하게 고정시키고, 액화천연가스의 유량 0.12 ㅣ/min, 0.36 l/min, 0.6 l/min, 기화기내의 압력을 100 kPa, 300 kPa, 500kPa로 변화시키면서 기화기내의 기포, 온도분포, 급팽창현상, 동결현상 및 기화후 수분함유량등의 비등특성을 규명하였다. 실험결과 기화기내의 압력이 증가할수록 기포는 작고 균일한 분포를 이루고, 폭발적인 급팽창현상은 일어나지 않았다. 또한 동결현상은 액화천연가스의 기화를 방지하지 못하였으며, 기화된 천연가스내의 수분함유량 몰%는 압력과 유량이 증가함에 따라 감소하는 경향을 보이고 있다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2189-2195
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• 1992

The performance of heat exchanger as an energy conversion device can be described by the available energy output and efficiency. The efficiency is defined as the ratio of the available energy output and the exergy of the heat source flow. In present study, a counterflow heat exchanger is analyzed and the conditions to obtain maximum output is numerically determined. As a result, the avilable energy obtained by the cold flow can be determined as functions of the heat capacity flow, the cold flow inlet temperature and the heat transfer capacity of heat exchanger. At the maximum output condition the heat capacity flow of the cold fluid is larger than that of the heat source, and the heat capacity flow ratio is equal to the ratio of the cold flow inlet temperature and the atmospheric temperature. And the avilable energy output increases as the heat transfer capacity of the heat exchanger become larger, but in the economic point of view there is also an optimum heat transfer capacity for a given heat source flow.

• Journal of Energy Engineering
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• v.20 no.3
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• pp.209-215
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• 2011

In this study, for efficiency enhancement of low temperature heat exchanger, the thermal conductivity and the viscosity of carbon nanofluids and oxidized carbon nanofluids were measured at $10^{\circ}C$ and $25^{\circ}C$, respectively. Carbon nanofluids were made by ultrasonic-dispersing ones in distilled water after Multi-Walled Carbon Nanotubes (MWCNTs) mixed Sodium Dodecyl Sulfate (SDS, 100 wt%), Polyvinyl pyrrolidone (PVP, 300 wt%) each. Oxidized carbon nanofluids were made by ultrasonic-dispersing Oxidized Carbon Nanotubes (OMWCNTs) in distilled water. The thermal conductivity of carbon nanofluids was measured by using a transient hot-wire method. The viscosity was measured by using a digital viscometer. As a result, the thermal conductivity of oxidized carbon nanofluids was the highest of those compared and the other carbon nanofluids at the same mixture ratio and temperature, and the viscosity was measured the lowest of those compared and the other carbon nanofluids.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5045-5050
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• 2015

As modern houses are constructed with high-density and high-insulation, there is benefit to reduce energy consumption, but there are many side effects raised from polluted air. To solve the problem, a ventilation system is used to improve a indoor air quality. In this study, we tested the parallel flow type heat exchanger used in a heat exchanger of an automotive air conditioner. And we experimentally estimate ventilation performance of HRV(heat recovery ventilator) with heat-pipe according to working fluid filling quantity and ventilation. The working fluid was R22, which was filled from 40 to 60 (%vol.) by 10(%vol.). Ventilation based on the front velocity was measured from 0.3 m/s to 1.5 m/s by 0.3 m/s intervals. Refrigerant filling quantity with the highest efficiency was found to depend on the ventilation. From this study the optimal refrigerant filling quantity in accordance with the ventilation of the detachable heat pipes was found experimentally.