Influence of sensible heat release on the performance of displacement ventilation in a train compartment

Abstract

It is well known that the human metabolism reacts on different ambient temperatures with a variation of the amount of released sensible and latent heat. However, the impact of this behavior on the performance of ventilation systems and the results of ventilation studies using thermal manikins is not yet investigated and reported in the literature. Accordingly, our aim is to address this issue for a displacement ventilation scenario in a passenger train compartment. Thermal manikins are used, comprising a similar blockage as real human do. A computer controlled system allows for a precise adjustment of the sensible heat released by each manikin. The study was conducted in a generic laboratory, representing the lower cabin of the DLR’s next generation train (NGT). In a first step, tests at variable mean cabin temperatures are conducted with human subjects. These are analyzed in terms of sensible and latent heat release of real humans. In a second step, the cabin was fully equipped with thermal manikins. For different amounts of sensible heat released by the manikins, the large-scale flow fields and the temperatures at selected positions are evaluated. At the conference, we will present results, comprising that the amounts of sensible and latent heat released by the human subjects fits the standard within the errors, using the temperature on chest level as mean cabin temperature. Astonishingly, the mean flow field is not influenced significantly, which we ascribe to the limited rate of fresh air available through the fresh air lake. The performance of the displacement ventilation system, quantified by the heat removal efficiency as a figure of merit decreases with increasing mean cabin temperature during human subject test, while is stays stable during test with thermal manikins.