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Abstract
In this paper, a simplified zonal model for the evaluation of the spatial distribution of the air temperature in a thermal zone is presented. This model, in which the air flow is caused only by buoyancy forces, is implemented in ALMABuild. The model is used for the analysis of the effect of the temperature sensor positioning on the control system behaviour and on the indoor comfort conditions. This analysis is performed considering a multi-zone building composed by three offices, focusing the evaluation to the central one. The office is heated by means of a radiator in which the hot water flow rate is varied by a valve controlled via a room temperature sensor. By means of numerical simulations, indoor comfort conditions, energy consumptions and control system response are evaluated for three different sensor positions (far from the radiator, in the middle of the office, close to the radiator), two radiator sizes (one obtained by imposing a high supply water temperature, 80 °C, the other a low supply temperature, 60 °C) and two control strategies (weather compensation and fast restart). The results presented in this study and demonstrate how complete dynamic energy simulation tools can provide to the designer important information, like the room temperature sensor position that should be close to the emitter and far from cold external walls, for the optimal design of HVAC systems.
Highlights
After the adoption of the Energy Performance of Buildings Directive [1] in 2010, designers are asked to develop buildings which are able to guarantee high comfort conditions but, at the same time, with lower consumptions of primary energy
In the most diffuse Building Energy Simulation (BES) software (i.e. TRNSYS [2] and EnergyPlus [3]) each thermal zone is characterized by a single value of the indoor air temperature because, typically, a onenode model is adopted for the evaluation of the convective heat transfer
The indoor thermal comfort conditions in Office 2 during the winter season are analysed by means of the estimation of: (i) the comfort time ( c), i.e. the percentage of the winter working time in which the operative temperature in the blue region of Figure 2 is between 19.5 and 20.5 °C; (ii) the overheating time, i.e. the percentage of the working time during which overheating conditions are observed in the blue region of Figure 2
Summary
After the adoption of the Energy Performance of Buildings Directive [1] in 2010, designers are asked to develop buildings which are able to guarantee high comfort conditions but, at the same time, with lower consumptions of primary energy. In the most diffuse BES software (i.e. TRNSYS [2] and EnergyPlus [3]) each thermal zone is characterized by a single value of the indoor air temperature because, typically, a onenode model is adopted for the evaluation of the convective heat transfer. This unique value of the air temperature coupled to a thermal zone represents the uniform value of air temperature obtained in presence of a perfect air mix; in this way, the spatial distribution of the air temperature within the zone is lost. It becomes impossible to use this software in order to obtain detailed information about the local indoor comfort conditions in a room
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