Issue 5/2024

The paper aims at evaluating the indoor environment of a selected educational building in the summer period, in terms of thermal stability and the possibility of reducing indoor spaces by night ventilation. Experimental measurements of indoor air temperature inside the common corridor of the school were carried out in August 2022 and 2023. The maximum daily indoor air temperatures were found to be close to 40 °C. Although there are various options to remedy this issue, for existing buildings the solution may be challenging. The paper shows that even simple measures such as night ventilation through open windows can improve the building indoor environment in terms of indoor air temperature.

Regular cleaning of air handling systems in office buildings and industrial halls should be part of the building maintenance. Air handling systems that are not properly maintained pose certain risks. This paper highlights the importance of regular cleaning of air handling systems, especially in view of the increased fire risk and sick building syndrome.

Technical building equipment systems have a significant impact on energy consumption and considerable potential for savings through the application of effective control. Traditional control often suffers from data 4heterogeneity and inconsistency. The introduction of a unified data description using semantic modelling and ontologies addresses this issue. Semantic description improves system interoperability, facilitates data analysis and visualization, and supports automatic error detection and predictive maintenance. This paper presents an overview of ontologies such as Brick Schema, Project Haystack, and Digital Buildings Project, and shows a practical example of implementing Brick Schema in a technical building system.

The design of complicated parts of drainage systems in high-rise buildings (mainly foul water stacks) is based on the calculation of the pressure resistance of the odor trap and the following hydraulic assessment. Due to the lack of design standards, the calculations must be based on older foreign research, but various uncertainties arise in the calculations and some methods are very difficult to verify and trace. For this reason, designers of sanitary installations avoid hydraulic assessments and rather reach for other stack system solutions, which are more expensive in terms of investment, but at the same time avoid demanding hydraulic calculations. One of the uncertainties is precisely the consideration of water evaporation in the calculation of the pressure resistance of the odor trap. The paper deals with mathematical analysis and experimental measurement of the suitability of considering water evaporation from the odor trap and the effect on its pressure resistance.

The article describes the development of a new type of local ventilation unit with heat recovery for residential buildings, focusing on its acoustic performance. The primary objective was to ensure compliance with the sound pressure level limits in the residential environments, as specified by relevant regulations, particularly concerning the presence of tonal noise components in the sound spectrum of the ventilation unit. The development process of the device involved four prototypes, with various noise reduction methods gradually tested. These methods included using absorbent materials to line the airways, optimising the number of fan blades in combination with adjusting its rotational speed, incorporating insulation to soundproof the noisy components of the unit, addressing manufacturing defects of the fans, and using of nanomaterials. In addition to standard methods of sound pressure measurement, FFT analysis was employed to more precisely identify the issues and trace the causes of the tonal noise. Through optimising the prototype, a 3.7 dB reduction in sound pressure level (at 2000 rpm) was achieved compared to the initial prototype, and the tonal noise components were eliminated. This allowed the unit to operate with higher sound pressure limits in indoor living environments, while also enhancing acoustic comfort for users.

Even distribution of water flowrate in the grid of parallel pipes is important for a proper function of ceiling water radiant panels. The lengths of these pipes can reach up to 150 m, which makes the investigation of operating conditions in laboratories or on real installations very difficult. In this context, CFD modelling and simulation appears to be a more suitable approach for the analysis of flow distribution in parallel pipe systems. The paper presents a model for CFD simulation of water flow in the pipe grid of a radiant panel. It is based on a substitution of long straight pipe sections. This surrogate model properly represents pressure losses in pipes while it avoids the problem with a full-length pipe model. The results from simulations with model grids of shortened pipes were validated by laboratory measurements. The model was finally used to evaluate the uniformity of water flow distribution in parallel pipe systems which are mounted in real radiant panels.

The paper is the first in a two-part series focussing on the development of a prototype water-based radiant ceiling panel produced using innovative 3D concrete printing technology. It briefly introduces methods for experimentally determining surface emissivity. The emissivity determination using the pyrometer – reference contact thermometer method is described in detail and demonstrated through a practical example of eleven samples, each 3D printed from concrete with different material composition and surface finish. The paper describes calibration of the temperature sensors used, the preparation of the experimental set-up and the evaluation of the measurements, including the determination of measurement uncertainties. Based on the measurements, the most suitable concrete mix for the 3D printing of the radiant panel envelope was selected. The results of this experimental study will be used in the follow-up paper, which will focus on computer simulation of the innovative radiant panel using the CFD method, with the goal of predicting its radiant efficiency.

The article presents a study analysing the potential for renewable heat utilisation within the Cérka project, which aims to revitalize the unused Frenštát mine area in Trojanovice. The initial study from the year 2022 focused solely on heat sources based on renewable sources of energy. The basic characteristics of the compared systems are presented in the paper, including an assessment of their annual utilization and the projected cost of heat.