Ventilation and filtration control play a critical role in determining indoor PM2.5 (particles less than 2.5 μm in aerodynamic diameter) concentrations of outdoor or indoor origin in residential environments. The objective of this study was to investigate the combined effects of flow rates and filter efficiency on indoor PM2.5 concentrations of residential buildings in Seoul, Korea. Using a particle model based on a mass–balance equation, parametric analysis was performed to examine indoor PM2.5 concentrations according to flow rates and filter efficiency under a wide range of outdoor concentrations and indoor generations. Results showed that ventilation control equipped with a medium–efficiency filter was as effective as that with a high-efficiency filter under normal outdoor concentration and high indoor generation rate conditions. It is not recommended to apply a low-efficiency filter because indoor concentration increases rapidly as outdoor PM2.5 increases when ventilation flow rate is high. For filtration control, it is important to increase both flow rate and filter efficiency in order to improve indoor PM2.5 concentration.

It is challenging to apply heat flow through a thermal bridge, which requires the analysis of 2D or 3D heat transfer to building energy simulation (BES). Research on the dynamic analysis of thermal bridges has been underway for many years, but their utilization remains low in BESs. This paper proposes a thermal bridge modeling and a dynamic analysis method that can be easily applied to BESs. The main idea begins with an analogy of the steady-state analysis of thermal bridges. As with steady-state analysis, the proposed method first divides the thermal bridge into a clear wall, where the heat flow is uniform, and the sections that are not the clear wall (the thermal bridge part). For the clear wall part, the method used in existing BESs is applied and analyzed. The thermal bridge part (TB part) is modeled with the linear time-invariant system (LTI system) and the system identification process is performed to find the transfer function. Then, the heat flow is obtained via a linear combination of the two parts. This method is validated by comparing the step, sinusoidal and annual outdoor temperature response of the finite differential method (FDM) simulation. When the thermal bridge was modeled as a third-order model, the root mean square error (RMSE) of annual heat flow with the FDM solution of heat flow through the entire wall was about 0.1 W.

The objectives of this study were to investigate the thermally activated building system (TABS) mechanism for appropriate use of the system and to apply the proper concept of TABS for each zone by using different TABS control strategies. In order to examine the TABS mechanism, dynamic simulation with EnergyPlus was used to model the office building with TABS, because the radiant heat exchange characteristics of the TABS according to the time variable was critical. The typical control concept of TABS, self-regulation, was applied in the simulation by setting the supply water temperature as room setpoint temperature. As a result, the advantage of self-regulation can be amplified by utilizing the entire thermal mass of the TABS, which can be executed by customizing to target a specific type of load. Since the large area of the office building may comprise different loads in different zones, the TABS control according to the different zone loads were proposed. By separating the control strategy from zone to zone, the proposed control strategy improved the thermal comfort by 5%, reduced peak heating load by 10%, reduced cooling load by 36%, and decrease the total energy consumption by 13%. This study demonstrated a possible improvement on self-regulation of TABS with separate zone controls.

Ventilation or filtration control is widely applied to improve indoor particle matter (PM) concentration. Adjusting the ventilation rates to control indoor PM levels can affect the concentration of other indoor pollutants and energy costs, and increasing the filtration flow rate can lower the indoor PM concentration, but also increase the fan energy consumption. In this study, we developed a ventilation and filtration control strategy to determine the optimal control mode and flow rate of the system to meet indoor PM (especially PM2.5) concentration, ensure adequate indoor air quality (IAQ), and minimize fan energy consumption. First, a dynamic model to estimate the indoor PM2.5 generation rate was developed based on the mass balance model and then verified by experiments. Next, the control limit (CL) curve was developed on the basis of the indoor PM2.5 characteristics depending on ventilation and filtration control during various indoor and outdoor PM2.5 conditions (indoor PM2.5 generation rate and outdoor PM2.5 concentration). In addition, an algorithm was proposed to determine the optimal control mode and flow rate of the system. Condition zone control can keep indoor PM2.5 below or as close to the desired target concentration as possible, maintain IAQ within acceptable ranges, and save about 15~70% of fan energy compared with the conventional rule-based control under the case condition.

In Korea, radiant floor heating systems are commonly used in residential buildings, even high-rise houses. If these existing radiant floor heating panels could be used for cooling as well, additional...

Flow rate balancing makes it possible to provide each zone with a design flow rate and to meet the heating load in a radiant floor heating system. Even though the control device of the heating system works well, insufficient water flow rates can degrade control performance and thermal comfort. The water flow rate should be adjusted appropriately to cope with the heating load of each zone. This study analyzes the effect of flow rate balancing upon indoor climate and thermal comfort in a radiant floor heating system through field survey and computer simulations. The results indicate that an increase in the dwelling floor area coincides with a more excessive uneven distribution of flow rate. As the gross floor area of the sample houses increases, the necessity of flow rate balancing for each zone becomes more crucial. An analysis was performed for additional hydraulic problems caused by hydronic devices such as header, valve, etc., and possible strategies to maintain the optimal flow-rate inside the pipes in a radiant floor heating system were suggested. Under part-load conditions the use of a dynamic balancing valve is a more effective method to prevent a cavitation as it reduces the pressure drop across a balancing valve. L'équilibrage du débit permet d'assurer à chaque zone un débit de conception et de satisfaire à la charge calorifique d'un système de chauffage rayonnant par le sol. Même si le dispositif de régulation du système de chauffage fonctionne bien, des débits d'eau insuffisants peuvent dégrader les performances de la régulation et le confort thermique. Le débit d'eau devrait être réglé de façon appropriée afin de faire face à la charge calorifique de chaque zone. Cette étude analyse l'effet de l'équilibrage du débit sur le climat intérieur et le confort thermique dans un système de chauffage rayonnant par le sol en recourant à une enquête de terrain et à des simulations sur ordinateur. Les résultats indiquent qu'une augmentation de la surface habitable coïncide avec une répartition inégale encore plus accentuée du débit. Plus la superficie hors œuvre des maisons utilisées comme exemples augmente, plus la nécessité d'un équilibrage du débit de chaque zone devient cruciale. Une analyse a été réalisée concernant les problèmes hydrauliques supplémentaires occasionnés par les dispositifs hydroniques tels que collecteur, soupape, etc., et des stratégies possibles ont été suggérées pour maintenir le débit optimum à l'intérieur des tuyaux d'un système de chauffage rayonnant par le sol. Dans des conditions de charge partielle, l'utilisation d'une soupape d'équilibrage dynamique est une méthode plus efficace pour éviter une cavitation, étant donné qu'elle réduit la chute de pression intervenant dans une soupape d'équilibrage. Mots clés: cavitation débit équilibrage hydronique chauffage rayonnant par le sol immeubles d'habitation confort thermique Corée