Thermal comfort analysis based on PMV/PPD in cabins of manned submersibles

In this study, we proposed a PMV-based method to evaluate the variations in thermal characteristics of the cabin of a submersible craft and the comfort levels of the crew during manned deep-sea missions. Based on the characteristics of tasks performed during a submersible deep-sea mission, we modified the criteria used by our model for clothing and activities, and then investigated other human factors found in the cabin as well. To test and verify our method, we used the averages of the environment data (depth, temperature, and humidity) from a Jiaolong mission that included six 7000 m deep-sea dives in the southern Mariana Trench. MATLAB was employed to calculate the PMV index and PPD, and to draw the PMV/PPD dynamic curves. The results showed that the PMV value changed constantly between [-2, +3]. The cabin thermal environment was dynamic and in continuous change, including a short period of a warm state and a long, continuous cold state. Because the submersible cabin lacked an air conditioning system, this paper analyzed the two-state thermal comfort based on regulating the air velocity of the ventilation system. Our detailed findings can be used by the submersible design institutes to evaluate the thermal comfort of oceanauts on manned submersibles, and to coordinate the energy distribution of air conditioning systems for cabins in the future.