| Title |
Study on the Heat Transfer Characteristics of Immerged and Falling Flows on Helical Tubes |
| Keywords |
Helical tube ; 나선형 코일 ; Outside heat transfer coefficient ; 관외 열전달계수 ; Film falling flow ; 액막 적하유동 ; Immerged flow ; 침전유동 ; Immerged rate ; 침전비 |
| Abstract |
An experimental study is carried out to investigate the characteristics of heat transfer of outside helical tubes. The main heat exchanger consists of twelve curved columns with each 300 mm diameter and the total length of 1.2 m copper tube having an outer diameter of 19.05 mm with 1.5 mm thickness. Water flows down the outside of helical tube, where flow patterns are the vertical film falling flow, immerged flow, and mixed-flow which is the combination of film falling flow and immerged flow. Refrigerant 11 flows the inside of the tube countercurrently. The experimental range of inside flow rate is 1.7∼3.2 l/min and outside flow rate is 21∼33 l/min. The results are presented as Nusselt number with corresponding Reynolds number for variety of outside and inside flow rates. The heat transfer rates of the mixed flow are 8 to 56% higher than those of film falling flow or immerged flow only. Interpretation of the results is given on the basis of physical reasoning and the correlation equations. |