Issue 4/2020

The article summarizes the current knowledge about the course of the COVID-19 disease pandemic, which is caused by the coronavirus SARS-CoV-2. It provides basic information about the transmission of the virus and its survival in the environment and deals with the possibilities of di sinfection of large areas.

The article deals with the issue of air in heating systems and the possibilities of eliminating the problems it causes. It focuses on the issue of permanently aerated heating system, on the relation of aeration with the operating temperature of the hea ting system, and on the pressure distribution in the hea ting system.

The presented study focused on the monitoring of a masonry chimney with an isostatic liner intended for removal of flue gases from a low heat output combustion plant burning solid fuels. The paper includes theoretical calculation of the condensation temperature of the water vapour contained in flue gases of various fuels in dependence on the amount of the excess combustion air. It also describes practical tests to determine time courses of inner wall temperatures of the isostatic liner at several heights of 7.5 m high chimney, including verification of the real dew point temperature of the flue gas. Information on the formation of condensate on the inner wall of the isostatic liner was obtained by newly designed sensors based on the principle of measurement of the resistance between two electrodes.

With respect to the seriousness of the issue and the time delay concerning the filter classes conversion between ČSN EN 779:2012 and ČSN EN IS O 16890-1:2018 for filters for general ventilation, the following chapters briefly present the characteristics of the new filter classification and summarize the main differences between the two classification systems. An overview of the available approximate conversion relationships that can contribute to the accelera ted implementation of the new filter c lassification system is presented.

The article compares performance parameters of fan convectors available on the Czech market, as stated by the manufacturers in their design documentation. It mentions the most common problems in the operation of fan convectors, which can be caused by improper system design. It deals with the boundary conditions of the design, which must be taken into account for trouble-free operation and use of the system. The paper presents examples of fan convectors designs. Polemic is conducted over common design practice, i.e. the design of a system according to the cooling capacity. The trickiness of such a design approach is demonstrated. It is indicated how to proceed so that the fan convectors serve their purpose, i.e. ensure the thermal comfort of the occupants.

This paper introduces an innovative concept for autonomous wall-curtain facade module that integrates functions air-conditioning, lighting, shading as well as renewable energy storage and generation. The facade module will be equipped with advanced control to coordinate all mentioned functions. Active facade module also enables autonomous thermal adaptation to given indoor and outdoor conditions. This paper is mainly focused on the testing of a single-thermoelectric-cell unit developed for initial performance assessment is presented. Based on the presented measurements, recommendations for further development of full-scale unit with nominal cooling load 640 W, that is suitable for a typical office (22 m2 floor area), are discussed. This paper contains part-load efficiency characteristics of the testing cooling unit. The influence of temperature drop between indoor and outdoor surfaces of the facade is also considered. All efficiency characteristics are evaluated based on experimental measurements.

The effective thermal capacity and thermal time constant are properties of the whole building that influence the thermal performance under transient boundary conditions. This paper first derives a method for estimating the values of effective heat capacity and time constant and presents probable ranges of values of both parameters for different types of buildings and building components. Analytical solutions of thermal performance of the building are then presented for two dynamic situations – intermittent heating and harmonic oscillation of external temperature and solar irradiation. Analytical solutions reveal the aggregated thermal parameters which affect the thermal behavior of buildings in both model cases. The analytical solution for harmonically oscillating boundary conditions was subsequently used to study the overheating of buildings. Relationship was derived for the maximal specific solar aperture such that the daily maximum value of the indoor temperature falls below the required value.

The paper deals with noise issues related to operation of air-water heat pumps. It compares the noise parameters available to designers of systems with heat pumps and the actual measured values of the in-situ sound pressure levels obtained during the house final inspection. For illustration, two installations with a typical location of heat pumps in front of the family houses were selected. Measurement and calculation were performed for both cases. Technical data from manufacturers are evaluated and compared with measured and calculated values in the conc lusion of the pa per.