Issue 3/2006

The article deals with problems of heat loss calculations according to two valid standards: the original Czech standard ČSN 06 0210 and the adopted European standard ČSN EN 12831. The results of heat loss calculations for a standardized family house determined on the basis of both standards are presented.

The article describes selected ways applied for long-time monitoring of an inner environment in buildings, which were used by authors in the past. Namely, data loggers Testo 175/177, distributed data acquisition systems based on ADAM 4000 modules and measuring “nests” of ADAM 5000 series, respectively, were used for these purposes. Authors present experience with their operation, as well as examples of acquired data.

The traditional way of indoor air quality (IAQ) monitoring requires both considerable costs and the repeated entry of the monitoring crew into the building. Usually, it is being used as short-term measurement programs. So far, it has been implemented only in a limited number of cases. This article describes the results of continuous remote monitoring of indoor air quality at twenty second-duration intervals in 85 rooms, at eight schools in Minnesota, during the school year 2003–2004.

In the article the author presents conditions for water vapour condensing from the air on the surfaces of construction engineering structures. According to foreign measurements and data the author defines the relative humidity of indoor air at which the condensation takes place in the pores of silicate walls and in turn, initiates growth of moulds. It follows from the analysis that the surface temperature-to-dew point temperature ratio of 3 K, required by the Czech construction standard, may not be always sufficient.

The experimental results document great differences between absorption and desorption of water vapour by construction materials. In a specific experiment, the most of the water vapour was absorbed by wood and fired brick the least water vapour was absorbed by rockwool. The full release of water vapour from wood was reached after 12 days, from fired brick after 29 hours. The materials with an ability to absorb and desorb the water vapour from or to the environment can dynamically influence the control of the indoor environment relative humidity. The well-timed ventilation of retained humidity is the indispensable condition for the healthy indoor environment.

The article explains the parameter of “operative temperature” and the way to calculate it. Under a moderate indoor thermal environment where the air flow velocity does not exceed 0,2 m.s-1 the calculated operative temperature differs from the resulting globe thermometer temperature only minimally. Taking into consideration the possible measuring error, it is possible (under such conditions) to ignore the calculation and use the resulting globe thermometer temperature for the evaluation of the thermal state.

The authoresses draw the attention to the important risk to which the non-smokers are exposed when breathing in the products of tobacco burning under passive smoking. Even the passive smoking is able to endanger the human life. The article mentions the diseases endangering a passive smoker. It brings in information about the international legislative activity, namely, the General Convention on Tobacco Control.

Physical parameters of non-freezing liquids (mixtures of water and suitable additives with freezing temperature lower than 0 oC) enlarge the pressure losses in the water circuits and worsen the heat transfer in tubes of heat exchangers. The increase of flow resistance in comparison to water is significant especially at low temperatures and high concentrations of additives. The article presents the analytical relationship of the density and viscosity in dependence on the additives concentration (propylene glycol) and mixture temperature. The data are applicable to calculations of pressure losses by friction for which the algorithm is presented. In conclusion, the calculation example and an analysis of the results’ sensitivity to deviations of input quantities are also presented.

The article contains an analysis of the absorber pipe diameter influencing the heat flow to heat transfer fluid. The analysis was carried out for flate solar collectors with copper absorbers and piping, arranged in parallel. A simplifying assumption of constant heat flow along the tube length was used. For water with anti-freezing mixtures the conclusion that the choice of the tube diameter has only a small influence on the change of solar collector overall efficiency was confirmed.

Radiant heat transfer between human being and the environment, in comparison to the convection heat transfer appears to be advantageous both from the point of view of creating the thermal comfort and the energy consumption. It is because the thermal comfort is markedly influenced by the surface temperature of other surfaces. In a space with cooling ceiling it is possible to maintain a slightly higher air temperature than at air conditioning systems with convection heat transfer, and achieve the same level of thermal comfort. The mentioned attribute results in energy saving for indoor air cooling. The radiant way of cooling is advantageous even from the point of view of further hygienic aspects because it is not accompanied by undesirable impacts as noise, or possible draught.