earticle

영어

Thermal performance of surface water heat exchanger(SWHE) is insufficiency because the material of submersible tube in SWHE such as the high density poly ethylene(HDPE) has low thermal conductivity as well as the tube have thicker HDPE. For the U value increasing in SWHE, 32A polyethylene(PE) covered stainless steel corrugated tube(PECCT, STS 0.25㎜, PE 0.5㎜ for anti corrosion) apply to SWHE in the surface water source chilling(SWSC) system in this study. U value of PECCT in SWHE will higher than the traditional HDPE tube because PECCT consist of high thermal conductivity material such as STS, the thickness of PE layer is tinny(0.5㎜), and the convection heat transfer rate of inner/outer layer is higher than the traditional smooth HDPE tube. The purpose of this study is the verification of thermal performances about PECCT in SWHE through the comparison of thermal performances of PECCT(32A) and the traditional HDPE tube(32A). U values of two tubes were experimentally obtained by the small SWSC system(1HP), the water chambers in the laboratory. The experiment show that U values of HDPE tube, PECCT were 7.499, 11.153(W/K) per meter, friction factor of HDPE tube, PECCT were 0.024, 0.048, COP of HDPE tube, PECCT were 1.903, 3.248 at conditions that the natural convection of outer tube and 0.7m/s fluid velocity, respectively. At conditions that the forced convection of outer tube(approximately 0.1m/s velocity of outer water) and 0.7m/s fluid velocity, U values of HDPE tube, PECCT were 8.151, 13.759(W/K) per meter, COP of HDPE tube, PECCT were 2.129, 3.485 respectively. Proposed tube in this study has reasonable pressure rating, long term durability. However, since the thickness is so thin, the system may require the chemical agent for protection from inner surface corrosion.

한국어

수열원냉동기 수중 열교환 배관에는 고밀도폴리에틸렌(HDPE) 배관이 주로 사용되고 있지만, 이는 낮은 열전도도와 재료의 두께 때문에 열성능이 미흡한 실정이다. 본 연구는 수중 열교환 배관의 열성능 개선을 위하여 32A 폴리에틸렌피복STS주름관의 수열원냉동시스템 적용을 제안하였다. 그리고 이의 적용에 관한 검증을 위하여 실험실 내에서 구성된 1RT 수열원냉동실험장치를 통하여 재래의 HDPE배관과 제안배관의 열성능을 실험적으로 비교분석하였다. 수조의 자연대류 조건에서 HDPE배관과 제안배관의 열관류율은 각각 7.499, 11.153(W/K)로, 강제대류 조건에서 각각 8.151, 13.759(W/K)로 나타났다. 두 배관의 마찰계수는 0.024, 0.048로 각각 나타났다. 두 배관의 COP는 강제대류 조건에서 각각 2.129, 3.485로 나타났다. 제안 배관은 적정한 내압과 내구성을 지니고 있지만, 얇은 배관 두께와 관련하여 내부 부식억제제 투입장치의 필요성이 있다고 본다.