Issue 3/2020

Due to the current epidemic of Covid 19 respiratory disease, various inaccurate information about respirators and protective masks have been appearing. In this article we provide information on the nomenclature, design and function of these protective devices, their characteristics and rela ted requirements.

The paper presents the results of a study, the aim of which is to point out important factors that will influence the choice of a ventilation unit with heat recovery (HR ) for balanced pressure ventilation of a family house. With use of a general example, it discusses the factors determining the minimum efficiency of the heat recovery exchanger for the climatic conditions of the Czech Republic. The pressure loss of the heat exchanger, the energy consumption of the fans, the energy consumption of the air preheating as frost protection, etc., are taken into account. The minimum efficiency is determined by the energy balance with regard to current prices and primary energy. From these results, the effect of efficiency on the return on investment in the system is further discussed.

The article describes the results achieved in the pilot testing of the diagnostic syste m of air handling (HVAC) units based on the analysis of data measured by instrumentation and control systems (i&cs). the diagnostic system includes over 50 rules for checking the air handling units (AHU) operation. over 80 air handling units were involved in the pilot testing. the article aims to present the diagnostics of air handling units on specific examples and to indicate possible scenarios of the use of the system in ever yday practice.

The paper summarizes findings concerning measurement and modelling of dynamic behaviour of radiators. The mathematical black-box model in the MATLAB software is briefly described (on an example for a panel radiator type 10 – 500 × 1000), including its underlying assumptions and boundary conditions. The aim is to acquaint the reader not only with the possibilities offered by dynamic modelling, but also with the knowledge gained from experimental measurement of opera tional behaviour of radia tors.

In the City of Prague centre, an investor had an intention to convert the unused attic space of a historical palace with original Renaissance roof truss into a habitable floor. It was necessary to design such a solution that would not worsen the humidity conditions and would not jeopardize the original timber elements. The requirements of the National Heritage Institute and the architect predetermined the use of very efficient thermal insulation above the rafters. The paper introduces and discusses several design solutions for new roofing layers and the critical detail near the eaves, considering both passive measures and active heating elements, and presents their hygrothermal assessment. Two criteria were used for evaluation: the interior surface temperature under winter design boundary conditions and the relative humidity in the area of the timber elements under average January boundary conditions. The presented assessment illustrated hygrothermal implications of different design measures and helped to identify acceptable solutions for further design phases.

When using thermal insulation, great emphasis is usually placed on the cost of the insulation material without a thorough assessment of its properties. However, in addition to unwanted heat losses, improper selection of thermal insulation can cause other problems, such as too high surface temperature of the device, insufficient temperature of heat transfer medium at the end of the pipeline at the point of consumption, risk of condensation of passing steam or flue gases and subsequent corrosion of pipes, etc. Thermal insulation quality is particularly important for investors, as insulation will only fulfil its intended purpose if it has the properties declared by the manufacturer. European product standards do not specify limits for the properties. However, the designer has the opportunity to choose a product on the market for which the manufacturer is able to prove its quality controlled by an independent third party – testing laboratory (meeting the limit curves according to the German standards AGI Q, or voluntar y quality certifica tes).

The author presents a basic overview article on water management, water resources, global trends of water consumption and possibilities of water supply. It also deals with the requirements for quality of water used both inside and outside the building. Last but not least, the article shows the basic possibilities of waste water reuse by its transformation into service water for reducing drinking wa ter consumption in buildings.

The article deals with various cold distribution systems for air conditioning equipment in buildings and their influence on the cooling factor of the cold source. It presents possible design solutions that minimize the overall energ y demands of the production and distribution of cold for air co nditioning in buildings.