Issue 2/2020

The article discusses with various options for ensuring local-area control. It focuses on the design of a thermostatic control valve in relation to the zone of proportionality and valve authority and the associated use of pre-setting on the control valves of radiators.

The paper describes drawbacks of various types of hydraulic connections and possible solutions in relation to the local control. The authors are aware that some solutions may not be feasible for a given building due to technical or economic reasons. Nevertheless, this article may serve as a guide on how to select a hydraulic connection in order to minimize future risks in the heating system operation and to achieve required energy savings.

The author focuses extensively on the issue of wood pellets, which are an important solid biofuel for household heating. He indicates the properties required by the standard and the properties for trouble-free, environmentally friendly and economical hea ting with this fuel.

The paper focuses on the evaluation of the benefits of the predictive control implementation on district heating systems (DH ). This modern method of control can be advantageously used in cases where the measuring and control system allows real-time concentration of measured data, including heat measurement, from all transfer stations into one system. Data with such frequency can be used to model a typical consumers’ heat consumption diagram in order to obtain a predictive model for each consumer. In combination with the flow and temperature model, the temperatures and flow rates in the individual parts of the system can be controlled by predictive control methods, with respect to minimization of the circulation pumps electricity costs and the heat losses during the heat distribution. The method was piloted on the DH system of the VS Chlum in Bílina and the benefits over weather compensation control are compared in the paper.

In recent years, it has been possible to encounter dozens of malfunctioning water distribution systems. Moreover, troubleshooting is often handled very unprofessionally. In the article, the author summarizes the findings about hydraulic conditions of hot water distribution systems, points out the shortcomings of the central hot water preparation system with a flow reservoir on the hot water supply pipeline (so called “bulges” on the pipeline), including the risk of microbiological water pollution.

This paper deals with an acoustic simulation, evaluation and measurement of an indoor air-conditioning unit commonly used in hotel rooms. The unit is situated in the plaster board ceiling of a hotel room above the entrance of the hotel room. The unit is used for cooling, and particularly for heating. The first step was to create a model of the real indoor air-conditioning unit from the catalogue data of a manufacturer, then built the model for the simulation of the internal sound propagation in the hotel room. The second step was to Mock-up the real hotel room. The goal of the paper is to compare the calculated data from the simulations with the measured data in-situ.

The article shows the ways of using load profiles of hot water heaters defined by Commission Regulations No 811, 812, 813 and 814/2013 to construct a cumulative hot water consumption curves. The authors point out errors commonly made by designers of hot water preparation systems in relation to the use of the load profiles. The conclusion of the article contains a comparison between consumption curves obtained with use of the hot wa ter heaters’ load profiles and real measurements in different types of buildings.

In the past, sun exposure could only be determined or verified using graphical tools. Sun path diagrams for manual use as well as diagrams implemented in computer programs were used. Recently, it is also possible to use a photography taken with a camera with a fish-eye lens. This method provides a more realistic and clearer representation of the shading conditions. As the corresponding polar sun-path diagram must be merged with the photography, there can arise a problem with selection of an appropriate diagram. Therefore, the article, among other things, introduces the necessary tools and gives guidance on how to choose a suitable sun path diagram. Part of the text is a comparison of computational relations used to determine the position of the Sun in the sky according to the existing ČSN standard versus the new European standard. The reader will also learn how to calibrate a camera with a fish-eye lens in order to verify the reliabi lity of the results.