Rising energy prices have contributed to the development of heat pump-based heating systems in Sweden. Low flow temperature in the secondary heat distribution system to rooms is a requirement for energy-efficient systems. This increases the thermal efficiency of the heat pump and decreases thermal losses in the distribution system. Flow temperatures in water-based systems for heat distribution in buildings have been decreased from 55C to temperatures around 30C. This is to maximize the efficiency of heating systems that are based on heat pump technology.
Equivalent temperature is a thermal index used today for assessment of the thermal comfortin vehicles. Prediction of the percentage of people dissatisfied by the thermal environment iscalculated by implementing equivalent temperature in the PMV/PPD thermal index. In this work,PMV/PPD and PD (draft rate) indices are compared for vehicle conditions, with respect to air velocity and turbulence intensity. Results indicate that turbulence intensity must be taken in consideration for higher air velocities and that PD is the predominant thermal index after a certain air velocity is reached.
An experimental study was conducted in a field environmental chamber with the aim of comparingceiling-based mixing ventilation (MV) system and under-floor supply system (UF) from the perspectives of indoor air quality and thermal comfort. Six tropically acclimatized female subjects participated in the experiments and they were required to complete a set of questionnaire pertaining to IAQ and thermal sensation every 20 minutes during each exposure of 2 hours.
The mean velocity in rooms predicted by CFD simulations based on RANS equations differs from the mean (in time) magnitude of the velocity, i.e. the mean speed, in rooms measured by low velocity thermal anemometers with omnidirectional sensor. This discrepancy results in incorrect thermal comfort assessment by the CFD predictions as well as incorrect validation of the predicted velocity field. In this paper the discrepancies are discussed and identified, and a method for estimating the mean speed based on the CFD predictions of mean velocity and kinetic turbulence energy is suggested.
Within the last years CFD has become an essential tool to investigate and optimize concepts of train coaches during an early design stage to achieve best results without major modifications of the final design. The simulation of the current railroad double deck coach gives some special challenges because of the complex channel system and the different boundary conditions on each floor. First the air duct including the outlet vents is investigated and optimized. The results are used as boundary condition for the simulation of the passenger's compartment.
The main motivation behind research on control of the thermal environment inside a vehicle cabin, is since long time thermal comfort for the passengers. However, the consequences of bad thermal control in vehicle cabs go beyond the aspect of personnel thermal comfort: the processes of driver sleepiness and fatigue, two major causes for traffic accidents worldwide, are unambiguously
influenced by the present thermal comfort. This research intends to make a start with the integration
A new standard, ISO/DIS 14505 is under preparation, dealing with the assessment of the thermal environment in vehicles, based on the equivalent temperature. The scope of this paper is to demonstrate the different results obtained when evaluating the thermal environment inside a vehicle, using the three well known parameters, air temperature, operative temperature and equivalent temperature. The tests were carried out in the winter season during heat-up of the vehicle cabin.
This paper analyses an individual control system that accounts for human thermal adaptation.Although the conventional individual control system has been shown to provide a satisfactory level of thermal comfort, there are questions over its energy efficiency. It has therefore become urgent to develop a new individual control system that can ensure both energy saving and thermal comfort. In this study, the alleviation time is proposed as an energy-saving control strategy for the individual control system.
Achievement of thermal comfort can be improved if individual control of the environment is allowed,namely through a local heating system (LHS), consisting of individually controlled radiant heating panels, adapted to a common office desk to a seated person. The coupling with of a new radiative module enhances the simulating capabilities of an existing CFD numerical model. The added improvements are applied to the evaluation of the thermal performance o the LHS. A comparative analysis clearly demonstrates the relevance of a due consideration of radiative exchanges.
This paper reports the function and the performance of chair mounted isothermal airflowgenerator system. There were four air outlets on the movable armrests and the air velocity at the body surface of an occupant was adjustable with fan speed controller. The air intakes were installed on the seat and the backrest of the chair. The experiment was carried out with 16 adult persons as the subject and the TSV and CSV were investigated under three different ambient conditions (26, 28, and 30C, 50%RH).
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