• 자원리싸이클링
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• 제9권3호
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• pp.13-21
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• 2000

본 연구는 폐용제를 가열, 증발 및 음축과정을 거쳐 용제를 회수하는 시스템의 열교환기 해석에 관한 것으로, 고온 열매체유로 가열되는 이중관형 열교환기를 사용하여 용제 증발과정의 열전달 특성을 분석하고 용제유량과 가열온도에 따라 물, 벤젠 및 알칼벤젠의 증발을 위해 요구되는 전열면적을 분석하였다. 폐용제 회수장치는 용제 공급펌프 이중관형 열교환기, 진공 스프레이 챕버 및 응축기동으로 구성되며, 이중관형 열교환기는 용제액을 열적 포화온도를 가열시키는 구간과 포화된 용제액을 증발시키는 구간으로 구성된다. 관 내 용제의 증발을 위한 전열면적을 열평형 모델링에 의해 예측하였고, 이중관형 열교화기의 관 내 온도분포 측정을 통해 이론값과 비교 분석하였다. 용제유량 0.1~0.51l/mm 및 가열온도 130~$260^{\circ}C$의 범위에서 용제유향 증가 및 가열온도 감속에 따라 단위전열면적당 열전달양이 감소하기 때문에 용제 증발을 위한 전열면적은 증가하였다. 관 내 용제 증발을 위한 전열면적의 이론적 분석결과는 측정값과 일치하였으며, 이중관형 열교환기를 사용한 폐용제의 증발과정을 통해 용제를 회수하는 기술에 적용이 가능하다.

• 자원리싸이클링
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• 제9권4호
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• pp.28-36
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• 2000

본 연구는 입자가 혼합된 용제를 이중판형 열교환기 내에서 가열 및 증발과정을 통해 건조이자와 용제로 분리하여 회수하기 위한 연속식 순간 진공건조 시스템 해석에관한 것이다. 진공건조시스템은 용제 공급펌프, 이중관형 열교환기, 진공 스프레이 챔버 및 응축기로 구성된다. 연속적으로 공급되는 용제는 이중관형 열교환기 내에서 가열, 팽창 및 증발되며 관 출구부에서 팽창된 증기가 진공 스프레이 챔버 내로 분사되고 증기는 응축기로 수송되어 용제로 회수되고 입자는 관성력에 의해 증기로부터 분리되어 건조된다ㅣ. 안료입자가 함유된 벤젠 및 알킬벤젠의 분리 및 회수성능 실험을 수행한 결과, 습분양 1.1%로 건조된 안료입자를 94% 회수하였고, 99.9 wt%의 고순도 벤젠을 88% 회수하였다. 평균직경이 $6.5\mu\textrm{m}$인 안료입자를 진공건조시스템의 이중관형 열교환기에서 관출구부의 고속 분사에 의한 폭발적 분산력에 의해 입경이 14%감소된 $5.6\mu\textrm{m}$ 크기의 건조 안료입자를 회수하였다. 따라서 진공건조시스템은 용제에 함유된 입자를 건조 및 분리하여 미분제 제품으로 히수하는데 효율적이며 폐용제 정제용으로 적용이 가능하다.

• 한국지열·수열에너지학회논문집
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• 제15권4호
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• pp.8-15
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• 2019

In order to design coaxial-type Ground Heat Exchangers (GHEXs) efficiently, the effect of components (i.e, heat exchange pipe and grouting material) on the thermal performance of coaxial-type GHEXs should be identified in advance. In this paper, three coaxial-type GHEXs with different configurations were constructed in a test bed. Then, the effect of heat exchange pipes and grouting materials on the thermal performance of coaxial-type GHEXs was investigated by performing in-situ thermal response tests (TRTs) and thermal performance tests (TPTs). In the TRTs, the effective thermal conductivities of the coaxial-type GHEXs with concrete grouting and STS pipes were improved by 6.15 and 22.7%, respectively compared to those of bentonite grouting and HDPE pipes. Additionally, in the TPTs, the use of concrete grouting and STS pipes in the coaxial-type GHEXs enhanced the in-situ thermal performance by 15 and 33.8%, respectively.

• 설비공학논문집
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• 제11권3호
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• pp.339-348
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• 1999

A computer model was developed in order to predict the temperature distribution and the performance of the vertical tube-in-tube ground coil heat exchanger. This model has been validated by experimental results conducted by ORNL. The heat exchanger performance with the variation of the length is calculated and compared. As results, the heat exchanger performance is proportional to the length but the performance per unit length decreases. The minimum performance of 70m - PVC heat exchanger during cyclic operation for a week is obtained 20,054kJ/h for cooling operation and 13,915kJ/h for heating operation. And minimum temperature difference is $4.64^{\circ}C$ for cooling operation and $2.64^{\circ}C$ for heating operation. In each case, it is noted that the temperature difference between the pipe and the far-field occurs within 0.8m from the heat exchanger.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.741-747
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• 2023

In this study, the heat transfer characteristics were numerically analyzed to investigate the possibility of utilizing cooling water using liquid nitrogen. From the study, as the mass flow rate of the hot fluid increased, the heat transfer rate increased by 8.9-81.7%. And lowering the inlet temperature of the hot fluid resulted in increase in the heat transfer rate by 33.8-71.5%. As for the filling level of liquid nitrogen, as higher filling level led to a decrease in the outlet temperature and an increase in the overall heat transfer coefficient.

• 대한설비공학회지:설비저널
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• 제11권2호
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• pp.1-9
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• 1982

Friction losses and heat transfer characteristics were studied experimentally for fully developed tubulent flow in tubes with twisted tape swirl generators. Data were obtained for pitch- to-diameter ratios from 8.10 to 25.71 with water under forced convection cool ins conditions. The experimental results of this and that of previous swirl flow investigation by Smithberg and Landis were compared. Nusselt number and friction data are combined in a constant pumping power comparision for swirl and straight flow, which indicates that improvement of 2.0 times in the best performance can be obtained with twisted tape-insert tube. A twisted tape-insert tube is recommended in the case of low temperature difference in heat-exchanger.

• 설비공학논문집
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• 제12권3호
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• pp.309-314
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• 2000

Experimental results for heat transfer characteristics of natural refrigerants R-290, R-600a and HCFC refrigerant R-22 during evaporating inside horizontal double pipe heat exchangers are presented. The experimental apparatus is basically a vapour heat pump system, composed of a compressor, a condenser, expansion devices, a evaporator, and some other peripheral devices. The test sections were horizontal double pipe heat exchangers, which were a pair of smoothed tube, having 10.07 mm ID, 12.07 mm OD, and grooved inner fin tube, having 12.70 mm OD, 0.25 mm fin height, and 75 fins. The local evaporating heat transfer coefficients of natural refrigerants were not much affected with the mass velocity than R-22 and it could be interpreted that the local evaporating heat transfer coefficients of R-22 were increased more than those of R-290, R-600a according to the increment of mass velocity. Moreover, the maximum increment of the heat transfer coefficient was found in R-290. The average heat transfer coefficient was obtained the maximum value in R-290 and the minimum value in R-22. It reveals that the natural refrigerant can be used as a substitute for R-22. In the grooved inner fin tube, 70% of the increment of the heat transfer coefficient was obtained compared to the smoothed tube.