Mobile air conditioning (MAC) systems play a critical role in ensuring occupant thermal comfort, particularly under extreme ambient conditions. Any delay in compressor engagement directly affects cabin cooldown performance, impacting both perceived and measured comfort levels. This study assesses the thermal comfort risks associated with compressor engagement delays of 6.5 seconds and 13 seconds under varying ambient conditions.
A comprehensive frontloading approach was employed, integrating 1D CAE simulations with objective and subjective experimental testing. Initial simulations provided insights into transient cabin heat load behavior and air distribution effectiveness, enabling efficient test case selection. Physical testing was conducted in a controlled climatic chamber under severe (>40°C) ambient condition, replicating real-world scenarios. Objective metrics, including cabin air temperature, vent temperature and cooldown rates, were measured to quantify thermal performance variations. To capture the human perception of comfort, subjective evaluations were conducted using jury assessments. Trained jurors provided feedback on perceived temperature uniformity, initial thermal shock and overall cooling effectiveness. Comparative analysis between the two delay scenarios revealed significant differences in early-stage occupant thermal comfort, with prolonged compressor engagement delay leading to delayed cooldown, increased discomfort perception and reduced thermal acceptability, especially in high-temperature conditions.
Results highlight the importance of compressor engagement timing in optimizing both system efficiency and occupant comfort. The study demonstrates that a 13-second delay can exacerbate thermal discomfort, particularly under severe ambient conditions, potentially affecting customer satisfaction. By integrating simulation-driven frontloading with targeted physical testing and subjective assessments, this methodology provides a robust framework for evaluating thermal comfort risks in automotive HVAC systems. The findings support informed decision-making for MAC system calibration, ensuring an optimal balance between energy efficiency and occupant well-being.