蒸发温度对强化换热管管外核态池沸腾换热性能的影响

Effects of Evaporation Temperature on Nucleate Pool Boiling Heat Transfer Characteristics outside the Enhanced Tube

对R134a在水平强化管（Φ25 mm）外核态池沸腾进行了实验研究。通过Wilson图解法求得管内换热准则关系式,通过改变蒸发温度（5.6℃,0℃,-2℃,-4℃,-6℃,-8℃）和热流密度（4-55 k W/m^2）,得到了管外沸腾换热系数随热流密度和蒸发温度变化的规律。实验表明,管外沸腾换热系数随着热流密度和蒸发温度的升高而增加。结合实验数据,提出了一个新的管外池沸腾换热关联式,该关联式与实验数据点的偏差显示,95%的数据点的相对误差在±20%以内。

Nucleate pool boiling outside the horizontal enhanced tube（ Φ25 mm） with the refrigerant R134 a was experimentally investigated. The inner heat transfer correlation has been obtained by using Wilson graphic method. Experiments were performed at evaporation temperatures of 5. 6 ℃,0 ℃,- 2 ℃,- 4 ℃,- 6 ℃ and- 8 ℃,heat fluxes from 4 k W / m^2 to 55 k W / m^2. Experimental results show that the pool boiling heat transfer coefficient outside the tube increases with the increase of heat flux and evaporation temperature. A new heat transfer correlation of pool boiling has been put forward. By comparison with test data,the relative deviation of 95% of the correlation value is within ± 20%.