Abstract Heat exchangers are used in air conditioners, heat pumps, marine, land and air vehicles, refrigeration systems, thermal and nuclear power plants, etc. Increasing heat transfer capacity of a heat exchanger means that the volume of the heat exchanger and the material used will be reduced. Besides, effects of some geometric parameters on heat transfer and pressure drop are more complex depending on the fin structure in fin and tube heat exchangers. In this study, three of the most dominant parameters affecting the thermal-hydraulic performance of a finned and tube heat exchanger were experimentally investigated. These are fin-type (louvered and wavy fins), fin pitch and number of tube-rows. The intermittent geometric structures of louvered fins break growing of the boundary layer and reduce its thickness yielding heat transfer enhancement. On the other hand, wavy fins cause an increase in the heat transfer area due to its large flow length and create instabilities in the flow due to flow separations increasing the heat transfer coefficient. In the present study, specifically five louvered finned and three wavy finned and round tube heat exchanger prototypes were manufactured. Heat transfer and pressure drop experiments of these heat exchangers were performed at a wind tunnel in a conditioned room. Heat transfer and pressure drop characteristics were presented as heat transfer coefficient ho, Stanton number St, Nusselt number Nu, dimensionless pressure drop coefficient Cp, Colburn-j factor, Fanning friction factor f, jlouver/jwavy, flouver/fwavy, j/f1/3 ratios and JF factor. The results were examined from the point of heat transfer and pressure drop mechanisms of louvered and wavy fins for the different number of tube-rows, fin pitches and air inlet velocities. It is found that Colburn-j factors and Fanning friction f factors of the LFRTHXs are higher than those of the WFRTHXs for all the studied cases. Colburn-j factors of the LFRTHXs are higher by 16.4–6.9%, 28.5–18.3% and 25–11.7% than those of the WFRTHXs for the cases of two tube-rows, three tube-rows and four tube-rows, respectively. On the other hand, pressure drops of the LFRTHXs are significantly higher than those of WFRTHXs. However, the thermal-hydraulic performances of the LFRTHXs are still higher than that of WFRTHXs. The thermal-hydraulic performance criteria j/f1/3 ratios of the LFRTHXs are higher by 9.6–4.1%, 22.1–16% and 16.8–7.4% than those of the WFRTHXs for the cases of two tube-rows, three tube-rows and four tube-rows, respectively.

中文翻译：

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不同管排数、翅片间距和运行条件对百叶窗和波浪翅片换热器热力和水力性能影响的实验研究

摘要 换热器用于空调、热泵、船舶、陆地和空中车辆、制冷系统、热电厂和核电站等。提高换热器的传热能力意味着换热器的体积和使用的材料会减少。此外，根据翅片管式换热器中的翅片结构，一些几何参数对传热和压降的影响更为复杂。在这项研究中，对影响翅片管式换热器热工水力性能的三个最主要的参数进行了实验研究。这些是翅片类型（百叶窗翅片和波浪翅片）、翅片间距和管排数。百叶窗翅片的断续几何结构破坏了边界层的生长并降低了其厚度，从而增强了传热。另一方面，波浪形翅片由于其较大的流动长度而导致传热面积增加，并且由于流动分离增加了传热系数而造成流动的不稳定性。在本研究中，特别制造了五个百叶窗翅片和三个波浪形翅片和圆管换热器原型。这些热交换器的传热和压降实验是在空调房间的风洞中进行的。传热和压降特性表示为传热系数 ho、斯坦顿数 St、努塞尔数 Nu、无量纲压降系数 Cp、Colburn-j 系数、范宁摩擦系数 f、jlouver/jwavy、flouver/fwavy、j/f1/ 3 比率和 JF 因子。结果是从不同管排数、翅片间距和空气入口速度的百叶窗和波浪形翅片的传热和压降机制的角度进行了检查。发现对于所有研究案例，LFRTHX 的 Colburn-j 因子和范宁摩擦 f 因子均高于 WFRTHX。在两管排、三管排和四管排的情况下，LFRTHX 的 Colburn-j 因子分别比 WFRTHX 高 16.4-6.9%、28.5-18.3% 和 25-11.7%。另一方面，LFRTHX 的压降明显高于 WFRTHX。然而，LFRTHX 的热工水力性能仍高于 WFRTHX。LFRTHX 的热工水力性能标准 j/f1/3 比高出 9.6-4.1%、22.1-16% 和 16.8-7。