润滑油对2种水平管降膜蒸发传热特性的影响

Effect of lubricating oil on heat transfer performance of falling film evaporation on two kinds of horizontal tubes

对R134a在光滑管和强化管管外降膜蒸发时,润滑油对换热特性的影响进行实验研究。蒸发温度为6℃,含油率分别为0.5%,1.2%,5.1%,工质喷淋密度分别为0.13,0.17,0.21 kg/(s·m)。结果表明:对于光滑管,管外换热系数随含油率的增加而增大;对于强化管,在低喷淋密度下,管外换热系数随含油率的增加先增大后减小,在高喷淋密度下,含油率的变化对管外换热系数影响不明显。在较高含油率下,光滑管存在一个最佳喷淋密度使管外换热系数达到最大,强化管管外换热系数受喷淋密度的影响较小;在较低含油率下,光滑管管外换热系数受喷淋密度的影响不明显,强化管管外换热系数随喷淋密度的增加先增大后减小。

The impact of lubricating oil on the falling film evaporating heat transfer of R134a was studied by experiments, which were conducted on the smooth tube and the enhance tube at the saturation temperature was 6 ℃with sprinkle densities of 0.13 kg/（ s· m）, 0.17 kg/（ s · m） and 0.21 kg/（s · m）, oil contents of 0.5%, 1. 2% and 5.1% respectively. The experimental results show when the spray density is constant, for the smooth tube, the tube outside heat transfer coefficient increases with the increase of oil content; for enhanced tube, under the low spray density, tube outside heat transfer coefficient first increases then decreases with the increase of oil content, while under the high density of spray, the change of oil content has not obviously influence on the tube outside heat transfer coefficient. At higher oil content, there was a suitable sprinkle density which can make the outside heat transfer coefficient to reach the maximum for the smooth tube, for enhanced tube, sprinkle density had little impact on the outside heat transfer coefficient; At low oil content, it was not obvious that the outside heat transfer coefficient was affected by sprinkle density for the smooth tube, for enhanced tube, tube outside heat transfer coefficient first increases then decreases with the increase of the spray density increases.