Optimising human thermal comfort in recreational vehicles for ASEAN climates through mechanical ventilation strategies

The growing popularity of recreational vehicles (RVs) in ASEAN climates calls for improvement of ventilation strategies to enhance occupant thermal comfort. Current standards provide limited guidance for mobile micro-environments, where challenges such as poorly distributed airflow, fixed vent placement, varying thermal loads, and insufficient consideration of occupant behaviour persist. This study aims to evaluate human thermal comfort in a Class-B RV equipped with ceiling-mounted supply and exhaust ventilation systems, designed for four occupants, under ASEAN climatic conditions using Malaysia as a representative case study. A computational fluid dynamics approach was employed, validated through grid independence testing, turbulence model verification (SST k-ω), and comparison with both literature data and onsite measurements. The PMV-PPD model, in accordance with ASHRAE Standard 55, was applied to assess thermal comfort across nine zones within the RV. Four scenarios were simulated based on combinations of two metabolic rates (1.0 and 1.2 met) and two clothing insulation levels (0.5 and 0.61 clo), reflecting typical activities and attire in the region. In total, 36 thermal comfort combinations were analysed per case. Results showed that positioning the air inlet at central ceiling location (2.900 m, 2.027 m, −0.280 m) in Case 1a achieved the optimal airflow mixing, with in 21 out of 36 combinations falling within the comfort range and the highest thermal comfort coverage improvement (+162.5 %) compared to the reference case. In contrast, additional or relocated outlet vents near the rear worsened occupant thermal comfort due to heat accumulation from appliances, with the lowest improvement recorded at +50 %.