关键词: 双螺旋片, 强化传热, 套管换热器, 数值模拟

Abstract: Experimental and numerical methods were adopted to study the heat transfer enhancement effect for double-pipe exchangers by installing high and low double strand helix fins on the outer wall of inner tube. The double-pipe heat exchanger with single high helical fin was treated as referenced structure. The curvature ratios were set to 0.44, 0.321 and 0.131 and the Reynolds number was in the range of 4000 to 20000. The impact of the ratio of low to high helical fin heights on the average Nusselt number of shell wall Nu_m and flow resistance coefficient f were studied. The comprehensive heat transfer performances of heat exchanger were examined at the same pump power condition. The study on heat exchanger with ε=0.44 showed that enhanced heat transfer effect was distinct when l/W value is greater than 1/2. The condition of l/W=3/4 is an optimal plan. For this case, the Nu_m of heat exchanger with double helical fins was improved by 10.8 percent on average compared to that of single high fins. PEC values are in the range of 1.044 to 1.204 within the researched scope. The study on heat exchangers with different ε values showed that PEC values are raised with the increases of curvature ratio ε at the same l/W values, which indicates that low and high double helical fins are more suitable to double-pipe exchangers with larger curvature ratio.

Key words: double stranded helix fins, heat transfer enhancement, double-pipe heat exchanger, numerical simulation