Ferenc Kalmár

Analysis of water sorption and thermal conductivity of expanded polystyrene insulation materials

This article presents the results of water sorption properties investigation and thermal conductivity measurements of expanded polystyrene thermal insulation materials with different mass densities. The sorption behaviour of the expanded polystyrene materials was achieved in a Climacell 111 type climatic chamber, after drying in a Venticell 111 type desiccator apparatus. The relative humidity varied from 25% to 90% at 293 K for 240 min. The thermal conductivity of each sample was determined using a Holometrix 2000 (HLS) heat flow meter. In this article, the sorption isotherms, sorption kinetics, thermal conductivities and the prediction of changes in function of water content of four pure expanded polystyrene (30, 100, 150, 200 and grey) slabs with different densities (14, 17.5, 23.7 and 27.5 kg/m3) and one expanded polystyrene mixed with graphite are given (grey expanded polystyrene). Practical application: The thermal conductivity as well as the moisture content are key thermal transport properties of building materials. The role of insulating materials in the building energy and moisture balance is more significant when compared with the other materials of the building structures. The laboratory measurements of these values of the insulating materials are very important either for the manufacturers or the contractors. The available bibliographic data for these materials are strongly incomplete and somewhere out of date.

Examination of the change of the overall heat transfer coefficients of building structures in function of water content

Nowadays, the most applied insulation material in the building sector is the expanded polystyrene. Different types of expanded polystyrene are used but more widely used is the graphite added type. Our research focuses on the analysis of heat conductivity and sorption properties of expanded polystyrene as these two are the most important physical properties from energy saving point of view. In this paper, the variation of heat transfer coefficient of an insulated wall is analysed in function of humidity content of insulation material. Brick and concrete walls with 0.4 m thickness were chosen for substrate and 0.1 m expanded polystyrene (30, 100, 150, 200 and the so-called grey expanded polystyrene) materials were applied as insulating layers. The investigations of sorption behaviour of the materials are important from the point of view of fundamental research and building technology as well. Sorption data taken from our previous measurements results were used for predicting the change of the overall heat transfer coefficients of different wall structures constituted this way. Practical application: The present technical note is based on our previous measurement results. Water can cause undesirable changes in the building structures and introduced in this article. During the fixing procedure of the additional insulating of a given building bad weather conditions (high relative humidity and/or low external temperature) can dominate. These phenomena can be imagined for building new houses. By the ‘in-building’ of the moisture into the wall structure, numerous and measurable change can happen in the U-value of the building envelope. The presented changes are estimations only, but can be used and can also help for planning and executing the insulating process.

Effects of thermal mass, ventilation, and glazing orientation on indoor air temperature in buildings:

In the last years in European countries, important measures were taken in order to reduce the energy need of buildings. Nevertheless, the energy need for cooling of buildings is rising. In most cases, to assure the required operative temperature, air conditioning systems are installed. Consequently, in summer period, the power networks of different European countries are overloaded. In order to determine the effects of glazed area orientation, air change rate, and thermal mass on the indoor air temperature, at the University of Debrecen, the Passol Laboratory was built. Measurements were performed from 2009 to 2013. Using the methodology given by EN ISO 13790:2008, the variation of indoor temperature was calculated and the theoretical values were compared with values obtained from measurements. The indoor temperature variation and the energy need for cooling were analyzed for different building structures, different orientations of the glazed area, and air change rates. The calculations have proven that the energy need for cooling can be reduced even to 25% of the thermal mass and the air change rate is chosen properly.

Simulation of the internal temperature in the Passol Laboratory, University of Debrecen

Abstract Nowadays the facades of newly built buildings have significant glazed surfaces. The solar gains in these buildings can produce discomfort caused by direct solar radiation on the one hand and by the higher indoor air temperature on the other hand. The amplitude of the indoor air temperature variation depends on the glazed area, orientation of the facade and heat storage capacity of the building. This paper presents the results of a simulation, which were made in the Passol Laboratory of University of Debrecen in order to define the internal temperature variation. The simulation proved that the highest amplitudes of the internal temperature are obtained for East orientation of the facade. The upper acceptable limit of the internal air temperature is exceeded for each analyzed orientation: North, South, East, West. Comparing different building structures, according to the obtained results, in case of the heavy structure more cooling hours are obtained, but the energy consumption for cooling is lower.

Innovative method and equipment for personalized ventilation.

At the University of Debrecen, a new method and equipment for personalized ventilation has been developed. This equipment makes it possible to change the airflow direction during operation with a time frequency chosen by the user. The developed office desk with integrated air ducts and control system permits ventilation with 100% outdoor air, 100% recirculated air, or a mix of outdoor and recirculated air in a relative proportion set by the user. It was shown that better comfort can be assured in hot environments if the fresh airflow direction is variable. Analyzing the time step of airflow direction changing, it was found that women prefer smaller time steps and their votes related to thermal comfort sensation are higher than mens votes.

Effects of solar radiation asymmetry on buildings’ cooling energy needs:

Over the last several years, the energy used for air conditioning in buildings increased in most European countries because of the high heat loads during the summer and the occupants’ increased comfort needs. The aim of our research was to determine the incident solar radiation on horizontal and vertical surfaces and to investigate the heat loads of buildings with different orientations of the glazed areas and different thermal masses in the building structures. Using the measured hourly global radiation data for the years 2009–2013, the diffuse and direct incident solar radiation was determined for the horizontal and vertical surfaces. A statistical analysis of the daily energy yield from solar radiation and the daily mean outdoor temperatures was conducted. The number of symmetric and asymmetric days was determined for torrid days. Using the methodology provided by standard EN ISO 13790:2008, the cooling energy demand and daily energy need for cooling was determined and evaluated for representative days of the analyzed years.

Comfort and energy analysis of heating up

Abstract The research work was done in the Building Physics Laboratory of the Department of Building Services and Building Engineering, University of Debrecen. The test room could be heated by radiator, wall, floor and ceiling heating. The main goal of this research was to see how the internal temperature varies during the heating up period, how much is the increment during the 3 hours measurement and how much the energy consumption is. This paper presents the results of the research work. The obtained results have proven that in our case the ceiling and radiator heating gave the higher increment of operative temperature and the lower energy consumption.

An indoor environment evaluation by gender and age using an advanced personalized ventilation system

In a closed space, appropriate thermal comfort and proper indoor air quality are extremely important in order to obtain the optimal work performance and to avoid health problems of the occupants. Using advanced personalized ventilation systems, different comfort needs can be locally satisfied even in case of warm environments. Thermal sensation and the subjective evaluation of indoor air quality of young and elderly people, men and women respectively, were studied in warm environment using advanced personalized ventilation system combined with total volume ventilation system. Using an advanced personalized ventilation system, 20 m3 h−1 air flow was alternately introduced by three air terminal devices built-in the desk and placed on a horizontal plane at the head level of the sitting subject. Thermal sensation was significantly cooler in case of young women in comparison with the other groups. Odor intensity was evaluated to be significantly lower in case of elderly women in comparison with the other groups. Evaluation of air freshness is in correlation with the general thermal sensation. Variation of the direction of the air velocity vector has a cooling side-effect, which, in warm environments, might be useful in order to improve the thermal comfort sensation. Practical application : From the basic factors that influence the thermal comfort sensation, air velocity is the one and only parameter that must be treated as a vector. The air flow velocity has an important effect on the convective heat quantity released by the human body, but the changes in the air velocity direction have a cooling side-effect. This cooling side-effect should be exploited properly in warm environments by advanced personalized ventilation systems to improve the thermal comfort sensation of the occupants without supplementary energy use.

Interrelation between glazing and summer operative temperature in buildings

Nowadays large transparent surfaces are widely used in office and public buildings. The positive effect of great views and natural light on people’s comfort is well known, but the high glazed ratio of building facades can lead to excessively high cooling energy demands. The heat load can be reduced by using glazing with high reflexion coating outwards and low emission coating inwards, triple panes and inert gas between the panes. Choosing proper thermal mass can further help in reducing the amplitude of the indoor operative temperature. In this paper the effects of solar factor of glazing, heat transfer coefficient of windows, windows area and thermal mass were analysed in an imaginary room with 3.0×4.0×2.8 m dimensions. As the results show the effect of the overall heat transfer coefficient is negligible. The effect of solar factor depends on the orientation. The expected differences between the amplitudes of the operative temperature are between 0.5 to 6 K for the analyzed room, depending on the thermal...

Exergy Quality of Buildings

Energy labeling of buildings is accepted and used in all European countries. Depending on the yearly specific primary energy consumption the energy quality of a building is expressed using a country specific method. Consequently primary energy is the basis of building energy class. Primary energy is obtained using different country specific transformation factors for gas, electricity, wood, biomass etc. However different quantities of warm water and steam can have the same energy content. Calculating the exergy content of used energy a better classification of buildings can be achieved. This paper presents a method to analyze residential buildings from exergy point of view. It was found a transformation factor between energy and exergy: 0.075.