During helicopter flight, variations in temperature and humidity within the equipment cabin are critical to the safe operation of onboard electronic devices. As flight altitude increases, the resulting drop in temperature may cause water vapor within the cabin to condense, potentially leading to circuit short circuits, metal corrosion, and reduced instrument accuracy. To address these issues, an energy-efficient thermal management system is proposed for the equipment cabin, which utilizes residual heat from the lubricating oil system (LOS) to generate hot air. This increases the cabin air temperature and reduces the relative humidity (RH), thereby preventing condensation. An intelligent control strategy has been developed to dynamically adjust the openings of cold-side and hot-side control valves based on real-time changes in cabin temperature and RH. When the internal temperature exceeds a threshold or the RH surpasses acceptable limits, the system prioritizes either cooling or dehumidification to maintain an optimal operating environment. Mathematical modeling and computational fluid dynamics (CFD) simulations were conducted to validate the effectiveness of this approach. The results indicate that following the introduction of hot air from the LOS, the cabin air temperature rapidly rises above the dew point, while the RH significantly decreases, effectively preventing condensation formation. Key areas achieved temperatures above 34 °C and RH levels below 70% within 360 s.