Healthy Buildings 2017 Europe July 2-5, 2017, Lublin, Poland

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1 Healthy Buildings 2017 Europe July 2-5, 2017, Lublin, Poland Paper ID 0188 ISBN: Dispersion of pollutants released at floor level under three types of heating systems: A CFD study. Laura Stasiuliene,*, Andrius Jurelionis 1 1 Kaunas University of Technology (KTU), Kaunas, Lithuania * Corresponding laura.stasiuliene@ktu.lt SUMMARY Floor heating and hot water radiator heating, as well as air heating in combination with heat recovery ventilation are most frequently used systems in modern buildings. These three systems are different from perspective of air temperature distribution and ventilation effectiveness. The aim of this study was to evaluate personal exposure of the occupants to airborne pollutants emitted at the floor level in rooms with three different heating systems combined with mixing ventilation. A three-dimensional steady-state numerical analysis was performed in a room heated by three different heating systems combined with two air distribution methods at the air change rate of 2 h-. The pollution source was simulated as benzene in the centre of the chamber. Heated dummy was used to estimate the effects of convection generated by the occupant as well as personal exposure. The results indicate that inhaled-to ambient pollutant concentration is higher in air heating and radiator heating. Positive effect of floor heating on ventilation effectiveness and personal exposure was observed. KEYWORDS Floor heating, air heating, radiator heating, personal exposure, ventilation effectiveness 1 INTRODUCTION A variety of technologies are used for heating buildings. Floor heating, radiator heating and air heating combined with mechanical ventilation are most frequently used systems in buildings nowadays. The performance of these three systems are significantly different. Floor heating provides consistent air temperature and low level air velocities in rooms. Radiator heating and air heating systems create uneven pools of warmth and vertical air temperature gradient is present. Higher temperatures and air velocities occurs above radiators compared to other parts of the room in radiator heating systems (Gökhan et al, 2010). A layer of warm air in the upper part of the room can be formed in air heating systems. Air heating is also sensitive to the air distribution equipment used (Krajčík et al, 2012; Feist et al, 2005). Dispersion of pollutants is influenced by location of pollutant source, supplied air flow, contaminant density (Heiselberg, 1996; Mundt, 2001). The results of the study on ventilation

2 effectiveness and thermal comfort in rooms with floor heating and warm air heating performed by Krajčik et al (2012) showed that ventilation effectiveness depends on the position of the air terminal devices. The study of Golkarfard and Telibizadeh (2014) showed that the deposition ratio of particles and the percentage of suspended particles in rooms with radiator heating system were higher in comparison to the floor heating. The isothermal pollutants released at floor level can be transported to breathing level by human convective boundary layer (CBL) (Licina et al, 2014). The most frequent sources of such pollutants are floor coverings, cleaning products, varnishes and others that emit volatile organic compounds (Kim, 2010; Katsoyiannis et al, 2008). Ventilation effectiveness and personal exposure to pollutants released at floor level in rooms with air heating and floor heating combined with mechanical ventilation was evaluated by our previous studies (Jurelionis et al, 2016). The aim of this study was to evaluate and compare personal exposure of the occupants to airborne pollutants emitted at the floor level in rooms with three different heating systems combined with mixing ventilation. 2 METHODS Computational fluid dynamics (CFD) software Flovent (Mentor Graphics, USA, 2015) was used to predict contaminant dispersion in the three-dimensional room with dimensions of m and ambient conditions of +20 C (Figure 1). Six cases of air heating, radiator heating and floor heating combined with two types of mixing ventilation were created for the numerical analysis. Low Reynolds number LVEL K-epsilon turbulence model with Double Precision Solver (DPS) was selected for steady-state numerical simulations. Figure 1. Room geometry used in the CFD simulation with air exhaust and two air supply systems, pollution source, and heated dummy.

3 One wall of the solution domain was imitating outside wall of the room. Temperature difference between cold wall and other walls of the solution domain was 3 C. Floor surface temperature was set to +24 C in cases with floor heating. The boundaries for cold wall and warm floor were defined as fixed temperature surfaces, and therefore radiation from these surfaces was estimated without the change of the surface temperatures due to absorbed radiation. Two types of mixing ventilation patterns (four-way air supply and high level wall grille air supply) was chosen for the numerical simulation as commonly used in modern buildings. Air change rate was set to 2 ach. Air supply diffusers ( m) were simulated as the uniform air jets by using the Box method (Nielsen PV, 1992). High level wall grille ( m) was simulated as a fixed flow opening with the free area ratio of Air exhaust diffuser ( m) was simulated as in-ceiling openings with the free area ratio of 0.5. Supply air temperature was set 5 C higher than the set-point room air temperature in cases when air heating was used. Supply air temperature was set as equal to room air temperature in cases with floor heating and radiator heating. Simplified geometry of heated dummy (1.7 m 2 surface area) was used to simulate convective and radiative heat flux from the dummy. The distance between the dummy and the wall was 0.2 m. Heated dummy located in the supply air side was used to estimate the effects of convection generated by the occupant as well as personal exposure. The pollution source was simulated as floor air inlet with very low air velocity equal to 0.01 m/s in the middle of the room. Properties of the pollution source were selected similar to benzene: molecular weight 78 g/mol, diffusivity in primary fluid 8.8e 06 m 2 /s, viscosity 7.43e 06 Ns/m 2. It was considered that pollution generation at the floor level was the mixture of air and benzene at 80,000 ppm concentration at air flow rate of 0.01 l/s. Pollution concentration in the supply air was set to 0 ppm. Cartesian grid was used with the number of grid cells varying in the range from 100,000 to 150,000 depending on the air distribution scheme. The density of the grid was increased close to the air supply equipment and localized close to the heated dummy. 3 RESULTS CFD simulations were performed for 6 overall cases. In Figures 2 and 3, the sections of the model at the height of 0.1 m above the floor and through the heated dummy are presented for each case with different heating types and different air supply patterns. Vertical air temperature gradient in cases with radiator heating, air heating and floor heating was 0.69, 0.85 and 0.06 C/m respectively. Air temperature simulation results are not presented due to limitations on the length of the article. CFD simulations showed that dispersion of near floor pollutants in the room in cases with radiator heating and air heating are influenced by convective flows generated by the occupant. In these cases pollutants were transported towards thermal dummy and this means that personal exposure was higher. In cases with floor heating pollutant flow was directed to the opposite side to the cold wall. This affect influenced personal exposure of the dummy and it was lower.

4 A B Radiator heating Air heating Floor heating Figure 2. CFD prediction results of floor released contaminant dispersion in the room (high level wall grille air supply); A the section of the model at the height of 0.1 m above the floor; B the section of the model through the heated dummy

5 A B Radiator heating Air heating Floor heating Figure 3. CFD prediction results of floor released contaminant dispersion in the room (inceiling four-way air supply diffuser); A the section of the model at the height of 0.1 m above the floor; B the section of the model through the heated dummy 4 DISCUSSION In this study human respiration was not considered, in order to compare the results with experiment which were carried previously. The point source of pollutants was selected for this study. The patterns of pollutant dispersion between the cases with pollutants generated by larger surfaces and single small pollution sources were tested and were similar in both cases.

6 5 CONCLUSIONS CFD simulations showed that personal exposure to pollutants released at floor level depends on heating type and is higher in cases with radiator heating and air heating. Positive effect of floor heating on personal exposure was observed. 6 ACKNOWLEDGEMENT This work was supported by the European Social Fund under the Global Grant Scheme (Project No. VP1-3.1-ŠMM-07-K ). 7 REFERENCES Feist W., Schnieders J., Dorer V., and Haas A Re-inventing air heating: Convenient and comfortable within the frame of the Passive House concept. Energy Build, 37, Golkarfard V. and Talebizadeh P Numerical comparison of airborne particles deposition and dispersion in radiator and floor heating systems. Advanced Powder Technology, 1; 25(1): Gökhan S., Nuhsin K Numerical analysis of air flow, heat transfer, moisture transport and thermal comfort in a room heated by two-panel radiators. Energy and Buildings, 43, Heiselberg P Room air and contaminant distribution in mixing ventilation. ASHRAE Transactions, 102 (2) Jurelionis A., Gagytė, L., Šeduikytė L., Prasauskas T., Čiužas D. and Martuzevičius D Combined air heating and ventilation increases risk of personal exposure to airborne pollutants released at the floor level. Energy Build, doi: /j.enbuild Jurelionis A., Stasiuliene, L., Prasauskas T. and Martuzevičius D Dispersion of indoor air pollutants emitted at nea-floor levels in rooms with floor heating and mixing ventilation. Indoor and Build Environment, doi: / X Katsoyiannis A, Leva P, and Kotzias D VOC and carbonyl emissions from carpets: A comparative study using four types of environmental chambers. J Hazard Mater, 4/1; 152(2): Kim S Control of formaldehyde and TVOC emission from wood-based flooring composites at various manufacturing processes by surface finishing. J Hazard Mater, 4/15; 176(1 3): Krajčík M., Simone A., and Olesen B.W Air distribution and ventilation effectiveness in an occupied room heated by warm air. Energy Build, 55, Licina D, Melikov A, Pantelic J, Sekhar C, and Tham KW Human convection flow in spaces with and without ventilation: personal exposure to floor-released particles and cough-released droplets. Indoor Air, doi: /ina Mundt E Non-buoyant pollutant sources and particles in displacement ventilation. Build. Environ, Nielsen PV. Description of supply openings in numerical models for room air distribution. ASHRAE Transact 1992,