Research on Self-Circulating and Forced-Circulation Evaporative Cooling Systems for Large Offshore Wind Turbines

This paper addresses the issue of insulation breakdown in large offshore wind turbines caused by uneven internal temperature distribution, which leads to motor failure. It proposes an evaporative cooling method capable of penetrating deep into the motor for direct cooling. To enhance the efficiency of the motor evaporative cooling system and clarify the required cooling levels under different operating conditions, a comparative analysis was conducted on the effects of self-circulating and forced-circulating evaporative cooling systems on the motor. Through an experimental platform, this study conducted tests on the cooling effects of self-circulation versus forced circulation under varying thermal loads, as well as the impact of medium flow rates on system performance under different configurations. Experimental results demonstrate that the evaporative cooling system can directly extract heat from the motor interior that other cooling methods cannot remove. Compared to self-circulation, forced circulation reduces the maximum temperature of stainless steel heat transfer pipes by approximately 20°C. Evidently, incorporating a pump as the circulation power source enables the system to achieve more effective temperature reduction under high thermal load conditions. Analysis indicates that although the evaporative cooling system designed in this paper is based on a 6MW capacity, experimental results demonstrate that the system is fully capable of handling the thermal load of larger wind turbines through simple fine-tuning.