Sensitivity of the PMV index and comfort regions, aiming to improve HVAC systems

Abstract

The HVAC control systems based on thermal comfort indices, in contrast with approaches that consider only temperature and humidity, provide advantages such as the improvement of the thermal quality of the built environment. Among several thermal comfort indices, the Fanger’s model (PMV) is of paramount importance. However, the attainment of this index in real equipment is considerably difficult, due to the difficulty of measuring the mean radiant temperature, and determining individual parameters such as the human metabolic rate and the thermal resistance of human clothing. Due to those difficulties, adjustments and adaptations must be carried out and, consequently, there are errors related to these three parameters. This article proposes a sensitivity analysis of PMV, based on those three variables, through simulation. For each analysis, the behaviour of the model is analysed for different values of temperature, air velocity and relative humidity, and also for different values of the analyzed parameter. It is also important to obtain the relative importance of each parameter of Fanger’s model, independently of units and analyzed values. Based on the Monte Carlo statistical method, a sensitivity analysis has been conducted, not only for the three cited variables, but also for all six Fanger’s model parameters. As a result, a sensitivity vector is presented, whose values are dimensionless and independent of the variables and parameters, considering all possible combinations. Moreover, new comfort regions are presented, considering also individual factors.