Issue 2/2021

The article considers the standard EN 442-2, which assumes a linear course of the temperature exponent with height for a given type of radiators. It focuses mainly on panel radiators, although it does not omit other kinds of radiators. It points to the fact that the dependence of the temperature exponent on height is not linear and increasing for a given type, as assumed by the characteristic equation of the type. Results are based on the evalua tion of the da ta collected from the radia tor manufacturers.

The article describes the results of a study aimed at examining a brick chimney with an isostatic liner with thermal insulation from mineral wool, that was intended for the removal of flue gas from an automatic solid fuel boiler with a nominal power of 25 kW. Surface temperatures of the chimney inner walls were monitored and the condensation of water vapour contained in flue gases was recorded with relation to these temperatures during practical tests, under different operating modes with combustion of different types of solid fuels. The results of the measurements were compared with measurements performed under similar operating conditions for a geometrically identical chimney with an isostatic liner without thermal insulation.

The article deals with the comparison of different methods of calculating heat loss to soil according to the current and preceding standards. The authors compare different approaches towards calculation and show their differences on selected model case studies representing a small building – a family house and a large building – a hall. A number of various solutions and locations of the floor slab are assessed. The paper also presents results of measurements of the soil tempera ture field adopted from literature.

The article presents the principle of calculating the heat loss by ventilation according to the currently valid ČSN EN 12 831-1 standard, with an explanatory commentary. The standard contains a simplified and universal calculation method. The article discusses some data for calculation of the heat loss by ventilation through the building envelope. The calculation of heat loss by ventilation is applied to a simple example of a family house with forced equal-pressure ventilation.

The paper focuses on the field of high efficiency filtration. First, the theoretical basics of fibrous layer filtration are briefly summarized. The main separating principles are explained, as well as the link between the fractional separability of a single fibre and the fibrous layer, and the differences between the ideal and the real fibrous layer. The next part informs about testing and classification of cleanrooms where high efficiency filters find their main application. The main part of the contribution presents the information on the origin and relevance of the international standard ISO 29463 in the field of high efficiency filters and its recent integration into European standardisation. In conclusion, the current unusual situation in Europe in the field of standardisation of high efficiency filters is explained, allowing the concurrence of EN and ISO standards.

With the change of use of historical buildings arise requirements for the treatment of their thermal and humidity environment in accordance with hygiene regulations, technology requirements and investor requirements related to the future intended use of the building. The paper assesses an historical building, where air-conditioning system is used to condition the air and ensure its required purity, temperature and humidity, and automatic, comfortable, year-round, economical and health-friendly operation is required. A prerequisite for proper function of air-conditioning is a proper design project of the air handling system, realization in coordination with other contractors on the construction site and regularly managed operation of the system. Non-compliance with this process can lead to reduced tightness of air-conditioning system elements, leakage of moist air and its subsequent accumulation in spaces where air exhaust is not possible due to the structural and architectural design of the building.

The article deals with the effect of heat transfer between hot and cold water pipelines on the multiplication of the Legionella bacteria. These bacteria need a very specific environment. The ideal places for their multiplication are systems for the preparation and distribution of hot water, where it represents a significant issue. Conditions of Legionella multiplication were evaluated on the basis of the water temperature fields in the pipeline, which were calculated by numerical simulation of heat conduction in domestic hot and cold water pipelines in the CalA 4.0 software. Several variants were evaluated, differing in the geometric arrangements of the pipelines embedded in the building structures and thickness of their thermal insulation. The results of the simulations confirm the need for sufficient insulation of the water pipelines not only to ensure low heat losses of the distribution system, but also for hygienic reasons, i.e. to prevent the multiplication of Legionella.