Issue 4/2006

The authoress evaluates Prague winters in term of heat demand for the last 236 years, i. e. for seasons from 1770/71 to 2005/2006. In a tabulated format and respective sequence, she presents the range of hardest and moderate winters for the period on the seasonal and monthly basis. Accompanying charts allow observing the Trends in the ten–year averages of heat demand during the 230 years, and the fifty-year averages for a period of 200 years. In both cases the graphs are presented on an individual months as well as a seasonal basis. The heat demand was determined for individual seasons by the degree day method and for the average internal temperature of 19.0 oC. For the average outdoor temperatures the Prague Klementinum temperature records were used.

The article contains the comparison of three types of flow control valves for warm-water floor heating surface capacity control. On the basis of simulation the operating effect from an adaptive, proportionally integrating, and two-position flow control valves is compared. The equitherm control equipment and the equitherm control with a feedback coupling to internal temperature are evaluated in reference to the room air temperature. As an evaluation criterion the internal temperature deviations from the desired temperature are used. The evaluation takes into consideration the different heating surface inertia. The attainable heat outputs depending of the surface temperature are indicated not only for floor but also for ceiling and wall heating surfaces.

The article deals with the applicability of renewable energy sources aimed primarily at biomass combustion. On the basis of laboratory experiments the article shows the biomass properties, analysis of fuel and ash elements and also the composition of combustion emissions. It draws attention to the possibility of producing toxic dioxins emissions. To limit these emissions an appropriate design of combustion equipment and a right choice of vegetation kinds for energy biomass are necessary. These approaches are presented in the article.

On the basis of his negative practical experience the author initiates the discussion on the design of office buildings ventilation in connection with existing legislation. He compares the minimum fresh outside air ration requirements with European regulations. From the indicated analysis it follows that the Czech regulations requirements are disproportionably overrated even if they allow for decreasing the fresh air quantity of up to 50%during the winter and summer seasons. At the same time he points to disproportionate requirements by the hygienic service personnel for designing offices and/or boardrooms ventilation.

Author of the article describes a suitable way of air humidity control for at air conditioning operation applied at production spaces of pharmaceutical industry. In case of the original SW that automatically and directly controlled the humidity content in the air according to the relative humidity sensing value, it was observed that a simultaneous humidification and dehumidification appeared when the air conditioning units were running. Also, when steam from the central source with temperatures above 100 °C was used for air humidification, the presence of fog was recorded at air conditioned spaces. Solution of these and further problems consisted of changes described in the article. In this way, author provides practically usable and instructive information that can be successfully applied in operating similar equipment.

The investor’s requirement to air-condition a production hall of 78 x 30 m, with 100 workers and an overall heat gain of 128 kW was fulfilled by implementing a rooftop air conditioning unit with direct expansion and gas reheat. The decisive aspect of the design and application success has been the use of displacement air distribution over the entire floor area. This allowed to decreasing the operating temperature difference by about a half which meant decreasing the investment and operating costs. The floor displacement air supply meant also a uniform air flow and temperature distribution in the space and maximum satisfaction of workers.

In the article the author presents a survey of daylighting solution problems. The article deals with the day lighting design methods and their verification, and first of all, with the application potential of the dynamic simulation models. In a separate chapter the survey and categorization of simulation programs for day lighting are presented. As an example, deseription of a detailed computer simulation applied to the specific schoolroom is given.

The earth-to-air heat exchanger is a device used for pre-heating and pre-cooling of fresh air. The contribution describes main principles of the newly developed numerical hygro-thermal model for transient simulation of earth-to-air heat exchangers. A validation against an analytical solution is presented.

The presented results and opinions relevant to windows and doors air permeability (generally opening closures) result from the work at the accredited testing „Laboratory of buildings opening closures, civil heat engineering and acoustics,“ at Zlín. The description of testing methods, the way air permeability has been evaluated; the standards base and critical polemic on important aspects of these problems provide a comprehensive and deeper finding. Introduced data may be used in design practice.

The article reports on the new German guideline for drinking water heating equipment planning, evaluation and use. This directive, issued in 2004, determines as to what a „good practice“ and user’s comfort should be in this area.

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