Issue 1/2021

The article concerns a wood burning appliance, which consists of a built-in appliance with a heater (hotwater fireplace insert) and a heat storage tank. The assembly was manufactured as an alternative to existing local solid fuel burning appliances, which are commonly available on the market. It is intended to serve as an additional source of thermal energy for heating of buildings with low heat demand. The article describes the results of combustion tests of two prototypes of hot-water fireplace inserts with integrated accumulation, which differed from each other in the volume of the heat storage tank. Combustion tests were carried out in a calorimetric chamber in order to determine the course of heat output (heat energy supplied to the surroundings of the appliance), the course of heating power (heat energy supplied to the heating water) and the ability of the tested appliance to accumulate thermal energy in the heat storage tank. Combustion tests were aimed at comparing different operating conditions. The article also compares the time courses of heat outputs of a conventional local appliance and the hot-water fireplace insert with integra ted accumulation.

The article deals with experimental verification of properties of an acoustic absorber, which is, unlike standard absorbers, placed in a direct sound field of the source. This brings advantages described in the paper. The aim of the measurement was to verify the effect of the absorber on the noise exposure of workers present in the acoustic near and far fields of the source, to determine its noise attenuation and to identify the types of noise sources for which the absorber is s uitable.

The article describes a heat pump with ground boreholes as a source of heat and cold for a university building in the center of Prague. Measured data from the operation of the system were analyzed and the issue of parallel heat and cold production was discussed in the context of sustainable development and buildings with minimal energ y consumption.

The assessment of the amount of daylight in buildings that was used until now was based on a model of an evenly cloudy winter sky and used the daylight factor D [%] as a criterion. The new European standard ČSN EN 17037 makes it possible to evaluate the amount of daylight by irradiance of the reference plane in the interior throughout the year. The new assessment necessarily includes other states of the sky than cloudy sky, including the effect of direct solar radiation. This radiation affects the brightness of shading obstacles to an extent depending on the cardinal direction of the shading obstacle. Brightness is an important characteristic of shielding obstacles and it must be considered for daylight calculation. The article deals with the assessment of brightness conditions on the front facades of objects depending on the c loud cover of the sky.

The current era is characterized by the development and use of alternative fuels to power road vehicles. However, new fuels bring not only more environmentally friendly operation of cars, but also new risks that accompany their use. One of the issues related to the operation of cars is their parking. First of all, parking in collective garages requires a considerable range of security measures, arising from the high number of cars. Emerging risks are the impetus for the creation of new standards with the target to ensure safe operation. However, the portfolio of alterna tive fuels is quite broad and each requires specific safety con ditions. Although there are currently basic rules for preparation of design proposals, some issues related to the safe operation of garages will have to be resolved in the future. One of them may be the safety ventilation. The article describes the current state of standards related to the safe operation of collective garages from the point of view of safety ventilation. Selected current trends related to the described issue are presented as well.

The article analyzes the thermal load from artificial lighting for different types of rooms and light sources based on the requirements for general workspace lighting. The aim of the article is to determine the indicative values of the heat load from artificial lighting for the purpose of air conditioning systems design. The current method of calculating the average illumination of indoor spaces and the available data from the of lighting systems manufacturers were used for the analyses.