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조홍기(Honggi Cho),조금남(Keumnam Cho),김정훈(Jeung-Hoon Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The objective of the present study was to calculate the pressure drop of two-phase flow in a heat exchanger with flat tubes. The heat exchanger had 15 flat tubes and both inlet and outlet headers with the inner diameter of 19.4㎜, respectively. Each flat tube had 8 rectangular channels with the hydraulic diameter of 1.0㎜. It was found that two-phase pressure drop through the flat tube showed the largest value among the other pressure loss components. Pressure drops through the tube end projection that blocked the refrigerant flow in the headers were relatively larger than those of the sudden expansion and sudden contraction. Based on the Yang and Webb correlation, pressure drop through the flat tube was larger by 43% to 72% than those of the other correlations.
조홍기 (Honggi Cho),윤백 (Baek Youn),김중호 (Jungho Kim) 대한설비공학회 2012 대한설비공학회 학술발표대회논문집 Vol.2012 No.6
The Characteristics of heat transfer and pressure drop in a concentric heat exchanger with inner tube was investigated by using a commercial CFD program. Four different inner tubes were studied. Bare tube has no fin and SPL 1, 2 and 3 have fin spirally attached on their surface. In case of SPL 1 & 3, the fin pitch is same with 1.18mm and the fin shape is triangular. However, the fin height is 1.00mm and 1.20mm for SPL 1 & 3, respectively. The fin height of SPL 2 is 1.05mm and the fin shape looks like an airfoil. The fin pitch of SPL 2 is 1.05mm. For all inner tubes with fin, the heat transfer rate increased from 1.8 to 2.3 times and the pressure drop increased from 5.5 to 8.6 times bare tube. SPL 3 with the highest fin height of 1.20mm showed the largest heat transfer rate, also the pressure drop increased significantly. It is seen that SPL 2 shows the best heat transfer and pressure drop characteristics, since SPL 2 showed similar heat transfer rate with SPL 3 but lower pressure drop by 17% than SPL 3. Since heat transfer and pressure drop strongly depend on the fin geometry of inner tube and have a trade-off relationship, the fin geometry should be selected for its application and condition.
조홍기(Honggi Cho),김태헌(Tae-Hun Kim),홍순철(Soon-Cheol Hong),김경록(Kyoungrock Kim),김중호(Jungho Kim),이창선(Changseon Lee) 대한설비공학회 2013 대한설비공학회 학술발표대회논문집 Vol.2013 No.6
The objective of present work is to investigate the performance of enhanced tubes with inner grooves by using a commercial CFD program. Four different enhanced tubes have been studied. G_0 and G_max tubes have no inner grooves on their inner surfaces, therefore, their inner surfaces are smooth. The inner diameter of G_0 and G_max are 8.9 mm and 9.9 mm, respectively. G_6 has 6 inner grooves and G_12 has 12 inner grooves. For all enhanced tubes, Serrated fins are manufactured on their outside surfaces and the inner groove is 1.0mm in width and 0.5mm in depth. As the number of inner grooves increase from 0 to 6 and 12, the pressure drops for G_6 and G_12 increased by 18% and 20% and the heat transfer rates increased by 7% and 14% under the mass flow rate of 189 kg/hr. In case of G_max, pressure drop and heat transfer rate decreased by 29% and 6% than those of G_0, because G_max have no inner grooves and its diameter is larger than that of G_0 by 1.0 mm.