自然循环与强迫循环条件下阻力及换热特性对比

为研究自然循环和强迫循环条件下流动及换热特性的区别,以单面加热窄矩形通道为研究对象,在压力0.2 MPa、实验段入口欠热度30~60℃的条件下,分别进行了强迫循环和自然循环条件下流动及换热实验。等热流密度条件下的阻力实验研究表明:在层流区,强迫循环和自然循环条件下的阻力特性几乎相同;在湍流区,修正后的Blasius关系式能同时适用于强迫循环和自然循环条件下的阻力预测;通过对比发现,强迫循环和自然循环条件下的转捩点雷诺数以及过渡态雷诺数区间几乎相同。换热实验研究表明:在湍流区,适用于强迫循环条件下的Gneilinski关系式能对自然循环换热能力较好预测;通过分析发现,在本实验研究范围内,自然循环与强迫循环条件下换热能力无明显区别。

Comparison of Flow Resistance and Heat Transfer Characteristics under Natural and Forced Circulations

In order to study the difference of flow and heat transfer characteristics under natural and forced circulations,the experiments on flow and heat transfer under natural and forced circulations were conducted at a narrow rectangular channel with one side heated for research object,and the subcooling from 30 ℃ to 60 ℃ with the constant pressure of 0.2 MPa.Under the condition of the same heat flux,the experiment on flow resistance shows that resistance characteristics in laminar regime under natural circulation are almost similar to those of forced circulation,and flow resistance in turbulent regime under natural and forced circulations can be predicted by the corrected Blasius formula.It is found that the Recr and the Re regions of transitional section keep the same under forced and natural circulations.The experiment on heat transfer shows that Gneilinski formula adjusted to forced circulation can forecast heat transfer characteristics in turbulent regime under natural circulation.It is found that heat transfer characteristics under forced and natural circulations have nearly no difference within the scope of this study.