Testing of a Radiant Wall Cooling System with Pipes Coupled to Aerated Blocks

Thermal output, surface temperatures, and supply and return water temperature were measured for a wall cooling system involving pipe attached to a wall section made of thermally insulating blocks. The experiment was performed for warm climatic conditions typical of, e.g., summer in Central and Northern Europe. The outdoor environment was simulated by a climatic chamber while the indoor climate was simulated by attaching a hotbox to the wall surface. The sensitivity of thermal output to several design parameters was investigated by 2D numerical simulations. The measurements showed a fast thermal response of the wall system. The cooling output was 38.3 W per m2 of the cooling area which equalled about 4.8 W/m2 per 1 K temperature difference between water and hotbox. The lowest surface temperature of 19.6 °C was measured at the pipe. Thus, the cooling output could be enhanced by reducing the surface temperature closer to the dew point temperature. The temperature of water in the pipe was very close to the surface temperature. It was illustrated how this characteristic of the wall cooling system tested positively affects the efficiency and cooling capacity of an air-to-water heat pump

Effect of energy renovation on indoor air quality in multifamily residential buildings in Slovakia

Buildings are responsible for a substantial portion of the global energy consumption. Most of the multifamily residential buildings built in the 20th century in Central and Eastern Europe do not satisfy the current requirements on energy efficiency. Nationwide measures taken to improve the energy efficiency of these buildings rarely consider their impact on the indoor air quality (IAQ). The objective of the present study was to evaluate the impact of simple energy renovation on IAQ air exchange rates (AER) and occupant satisfaction in Slovak residential buildings. Three pairs of identical naturally ventilated multifamily residential buildings were examined. One building in each pair was newly renovated, the other was in its original condition. Temperature, relative humidity (RH) and the concentration of carbon dioxide (CO2) were measured in 94 apartments (57%) during one week in the winter. A questionnaire related to perceived air quality, sick building syndrome symptoms and airing habits was filled by the occupants. In a companion experiment, the IAQ was investigated in 20 apartments (50%) of a single residential building before and after its renovation. In this experiment, concentrations of nitrogen dioxide (NO2), formaldehyde and total and individual volatile organic compounds (VOC) were also measured. CO2 concentrations were significantly higher and AERs were lower in the renovated buildings. Formaldehyde concentrations increased after renovation and were positively correlated with CO2 and RH. Energy renovation was associated with lower occupant satisfaction with IAQ. Energy retrofitting efforts should be complemented with improved ventilation in order to avoid adverse effects on IAQ

Evaluation of Indoor Environment in Apartment Buildings Before and After their Refurbishment

The objective of the study is to analyse and evaluate the indoor environment of the apartment buildings before and after their refurbishment. Thermal comfort and indoor air quality were taken into consideration based on both objective and subjective evaluation. Thermal indoor environment was evaluated in six blocks of dwelling buildings situated in Slovakia. Evaluation of the thermal indoor environment was based on the recording of the indoor temperature and the relative humidity before and after refurbishment. The subjective evaluation was based on a questionnaire survey, which includes data such as the thermal perception, inhabitant’s behaviour and personal background of 244 respondents living in the buildings before refurbishment and 236 respondents living in the buildings after refurbishment

Investigation of polyurethane electrospinning process efficiency

The electrospinning process efficiency of different PUs has been investigated. Specific attention has been paid to understand the role of PU soft segments and synthesis type on the stability of the PU solution and electrospinning process as well as on the quality/property changes of the produced nanofibres. PU samples before and after the process were analyzed rheologicaly and relaxation spectra were determined for all of them from frequency dependent loss and storage moduli measurements. It has been found that rheological analysis of PU, which is used for electrospinning process, can be useful tool from electrospinning process efficiency and optimization point of view. Nanolayers homogeneity during several hours of manufacture in optimized electrospinning process is proved by selected properties from aerosol filtration. © 2009 American Institute of Physics

Morphology of nano and micro fiber structures in ultrafine particles filtration

Selected procedures permitting to prepare homogeneous nanofibre structures of the desired morphology by employing a suitable combination of variables during the electrospinning process are presented. A comparison (at the same pressure drop) was made of filtration capabilities of planar polyurethane nanostructures formed exclusively by nanofibres, space polycarbonate nanostructures having bead spacers, structures formed by a combination of polymethyl methacrylate micro- and nanofibres and polypropylene meltblown microstructures, through which ultrafine particles of ammonium sulphate 20-400 nm in size were filtered. The structures studied were described using a new digital image analysis technique based on black and white images obtained by scanning electron microscopy. More voluminous structures modified with distance microspheres and having a greater thickness and mass per square area of the material, i.e. structures possessing better mechanical properties, demanded so much in nanostructures, enable preparation of filters having approximately the same free volume fraction as flat nanofibre filters but an increased effective fibre surface area, changed pore size morphology and, consequently, a higher filter quality. © 2011 American Institute of Physics

Energy retrofitting of a single-family house

This article shows a real ongoing project called RenoActive, which is financed by company Velux. In cooperation with the company mentioned above an old single-family house was chosen to renovate. Three energy alternatives had been calculated: Standard, Comfort and Deluxe. The thermal insulation system of the building is almost the same in all three alternatives. The alternatives mostly appear in the building services systems. This article evaluates the energy consumption and investment differences between the alternatives

Energy conservation by retrofitting of dwellings

This article investigates the impact of energy renovation on the indoor environmental quality of apartment building during heating season. The study was performed in one residential building before and after its renovation. Energy auditing and classification of the selected building into energy classes were carried out. Additionally, evaluation of indoor air quality was performed using objective measurements and subjective survey. Thermal environment and concentration of CO2 was measured in bedrooms. Higher concentrations of CO2 was observed in the residential building after its renovation. The concentrations of CO2, in some cases exceeded the recommended maximum limits, especially after implementing of energy saving measures on the building. The average air exchange rate was visible higher before renovation of the building. The current study indicates that large-scale of renovations may reduce the quality of the indoor environment in many apartments, especially in the winter season