A ventilated cavity wall is often proposed in the building envelope design as an alternative to thetraditional wall, mostly due to its ability in reducing the thermal load during the hot season. In order to be recommended as a solution for improving the thermal comfort, a thorough analysis of its performance under all possible scenarios is required. For assessing the thermal performance of the cavity wall, an experimental model has been built and tested at the DECivil of IST.
Subjective experiments were conducted during the summer season and the winter season in order toclarify the multiplied effects of humidity and indoor chemical pollutants on subjective comfort and productivity. Lower concentration of formaldehyde was observed at low humidity than at high humidity. Subjects rated the acceptability of air lower at the beginning of the exposure in the environments polluted with formaldehyde. On the other hand, lower humidity caused subjects to rate air quality higher in clean air.
In order to clarify the effects of humidity on subjective comfort and productivity under transient conditions in summer, subjective experiments were conducted. Subjects were exposed to 30C/70%RH for 15 minutes in Chamber 1. Then they moved to Chamber 2, in which 4 different conditions were set, and stayed for 180 minutes. For all 4 conditions, SET* was kept constant at 25.2C. Skin wettedness on left chest and skin moisture on left forearm decreased more at low relative humidity. No significant difference in subjective task performances was found among all conditions.
This paper deals with the study of natural ventilation in a building under tropical climates. Roomair distribution is analyzed with a statistical approach. The building is a cube with two opposing outdoor large openings. The cube is modeled using the RNG k-e model. A dimensionless velocity coefficient for different wind directions is evaluated for each indoor cell of the grid. Cumulative distribution function of this coefficient is calculated at different height to point out the influence of the wind direction.
Subjective experiments were carried out to evaluate thermal comfort of inhomogeneous thermalenvironment created in task area using floor air outlet. Subjects are allowed to control freely the air volume supplied from the floor air outlet and the angle of elevation of the central axis of the air jet discharged from the floor air outlet to get their thermal comfort.
Nevertheless the proven benefit of a cyclist helmet in preventing serious head injuries whena crash occurs, many cyclist still refuse to wear a crash helmet. The main reason for not wearing acyclist helmet is the sensation of discomfort encountered when wearing one. This paper evaluates and analyses - for the first time - both local and global temperature levels and moisture production in order to obtain insight in the interaction between both mechanism, as a response to differences in effort level, air velocity and air temperature, and how to improve its thermal comfort features.
The paper presents a method of designing thermal comfort conditions in a room with an UnderFloor Air Distribution system (UFAD). A two-phase algorithm is based on: a steady or unsteady heat and mass transfer theory in the first step of computation and thermal comfort calculation in the second step. This method is implemented as the computer program UFAD_NET.
Natural night ventilation is an energy efficient way to improve thermal summer comfort.Coupled thermal and ventilation simulation tools predict the performances. Nevertheless, the reliability of simulation results with regard to the assumptions in the input, is still unclear. Uncertainty analysis is chosen to determine the uncertainty on the predicted performances of natural night ventilation. Sensitivity analysis defines the most important input parameters causing this uncertainty. The results for a singlesided ventilation strategy in a single office are discussed.
The compatibility of energy conservation and thermal comfort in Japanese house with high air-tightness and insulation equipped with the whole-housing heating, ventilation and air conditioning (H.V.A.C.) system was examined by a numerical analysis. In addition to the present situation, several scenarios for achieving the compatibility were supposed. Thermal environment, thermal comfort and electricity consumption of H.V.A.C. system were analyzed throughout a year for each scenario. A combination of proper scenarios was found to be achieved the compatibility.
The maximum velocity in the occupied space is an important aspect of the thermal comfort. The velocity field is controlled by the position of the inlet devices, the introduced momentum flux and the thermal load of a room. Isothermal room air flow velocities depend on the position of the inlet devices and the introduced momentum flux only. Increasing the thermal load of the room leads to a more and more unstable flow situation. Finally, the flow field is dominated by buoyancy effects and it develops a new stable flow structure.
Login