发电机冷却的热力学分析与评价方法

Thermodynamic analysis and evaluation method for generator cooling

为了提高大型发电机的冷却效果,保证发电机长期安全可靠运行,建立了发电机冷却过程的数学模型,将热力学基本定律应用于模型的分析中,得到冷却过程中由于不可逆因素而引起的熵产的计算方法。通过对采用不同的冷却介质时熵产的比较来评价冷却效果的好坏,为发电机选择了较为理想的冷却介质;同时,对熵产的来源及影响因素进行了分析研究。研究结果表明,采用气体冷却时,不可逆因素引起的熵产远小于液体。由流体粘性耗散引起的熵产可忽略不计。从热力学第二定律角度评价,氢气与空气的冷却效果大体相当。

In order to improve the cooling effect of the large generator and ensure the long - term safeand reliable operation of the generator, the mathematical model of generator cooling process was estab-lished. The basic law of thermodynamics is applied to model analysis, the calculation method of entro-py production is obtained by irreversible factors in the process of cooling. The cooling effect was eval-uated by comparing the entropy production with different cooling medium, and the ideal cooling medi-um was selected for the generator. At the same time, the source and influence factors of entropy pro-duction were analyzed and studied. The results show that the entropy produced by in＇eversible factorsis much less than that of liquid when the gas is cooled. The effect of heat transfer temperature differ-ence on entropy production is very significant, and the small increase of temperature difference willincrease the entropy production significantly. Entropy production caused by fluid viscous dissipation isnegligible. From the second law of thermodynamics, the cooling effect of hydrogen and air is roughly equivalent.