Issue 5/2008

The substantial part of the total heat output of radiant panels is their radiant component. It is the crucial factor within the scope of industry halls heating by radiant panels, influencing the thermal comfort in the heated space. The author focused on the essential parameters affecting exactly the radiant part of panels’ heat output during their design process, and gives a methodical review. A reader is comprehensibly apprised with the most important conclusions.

The article deals with an evaluation of all-year monitoring of inner environment in the conference room of General Health Insurance Company branch office in Brno. The main attention paid to the influence of high portion of glazed areas on air-conditioning demands. The energy balance assessment indicates that the solar gains exceed the heat losses since March. The measured inner temperatures confirm the need of air-conditioning on sunny days not only in summer but in transitional seasons, too. Increased solar gains can therefore be utilized only from November to February, or on half-cloudy days in spring and autumn. In the rest of the year, they should be controlled using advanced glazed systems and efficiency shading devices.

Measured energetic parameters of cooling equipment do not themselves reflect whether the equipment works within the limitation level of components, from which it is built (mainly the compressor). Such information we can obtain only by comparing these parameters with parameters read from the employed compressor characteristics, worked out for the boundary conditions of the particular measurement. Application of computer technology enables an integration of a mathematical model of a cooling circuit with real compressors directly into a measurement system and continuously compare them already during a measurement process and thus obtain important information not only about the parameters but also about the state (“condition”) of the measured equipment.

Cooling conditioning systems often represent the easiest way of thermal comfort treatment in summer and winter period for investors and users. Simple systems can be installed and operated without deeper knowledge of their limitations, systems that are more complicated would benefit from detailed information. The article briefly characterizes the systems’ conception and brings some information, which cannot be found in ordinary producers’ documentation.

The article brings an integrated view of some types of so-called alternative (non-wooden) pellets from biomass concerning their fuel qualities and evaluates their behavior during combustion in a low capacity boiler, for which they are designed. First part of the article is devoted to presentation of some results of a long-termresearch in a heating laboratory Juliska at Faculty of Mechanical Engineering CTU in Prague, and to alternative pellet characteristics in relation to the most common wood materials. The status of the legislative in relation to biofuels and status of their utilization in Czech Republic is mentioned as well. In the second part of the article are discussed current problems of polychlorinated dibenzodioxins and furans emission during biofuels combustion in details; especially there are compared different processes of their generation and possibilities of their production limitation in combustion process.

Heat pumps are currently manufactured in a wide range of usable properties. If comparing products of different manufactures, all of them must be taken into consideration. Otherwise a huge price difference of heat pumps of nearly the same heating capacity may surprise. For the simplification of comparison and certification of manufacture’s data, heat pumps are measured at norm conditions and can by eco-labeled according to Comission Decision No. 2007/742/EC. The measurement conditions and criteria for sorting based on a long termpractice of the Swiss laboratoryWärmepumpen – Testzentrum Buchs are described.

In connection with the implementation of a building energy demand evaluation, which expresses the total annual heat demand in buildings, it is useful to have referent values for different building types, which can be used in verification calculations of determined energy demands. There are comprehensibly compiled results of invoice measurements of heat energy consumption over years in different types of buildings and operation of civil housing in the article.

Principle of absorption cooling equipment, thermal circuit arrangement with its demonstration in a thermal diagram for a couple of substances water (refrigerant) – LiBr (absorbent) are described in the first part of the paper. The paper also gives brief information about the dependence of solar collector efficiency on its type and temperature of heated substance. The second part is dedicated to the description of two realized devices, which use a solar system as a driving energy source for absorption cooling equipment with a nominal refrigerating capacity of 45 and 564 kW.

Cooling appliances in hotel Hilton in Prague – Karlin were considerably damaged during the catastrophic flood in 2002. The author describes the proposed solution to changes and modifications of cooling system and unusual difficulties, which had to be surmounted during the implementation.Water from river Vltava, relatively cold due to the Vltava’s dam cascade, was used to remove condensation heat and to direct preparation of chilled water for air conditioning. Cooling water is taken from a flushing canal of a diameter 1,5 m, passing randomly at a depth of 6 m under the floor level of hotel garages. The canal access and cooling water taking itself are unusual and unique in praxis. A pumping device assembly had to be realized under the difficult conditions under the canal water level with a utilization of diving engineering. The method of perennial cool intake for air-conditioning is also atypical. Due to the large surface atrium glazing (approx. 2000m2), the interior hotel rooms situated to the atrium have a solar heat load in every year season. The utilization of the new cooling system solved former problems and guests complaints. Further effects of this way of cooling consist in high operation economy and in removing a possible risk of Legionnaires’ disease, comparing to previously operate opened cooling towers. Moreover, the operation has a 100% protection in summer extreme conditions, by using both ways of condensers cooling – Vltava/towers.

The article describes border conditions of measurements by thermovision technique. The author brings near possibilities and methodology of border measurement conditions determination and their impact on scanned thermographical record on examples from measurements in praxis.

The author presents a list of valid Czech regulations (laws, government decree and regulations), in which requirements on microclimatic conditions and ventilation of indoor environment are defined. She points out, that requirements, especially in Ministry of Health regulations, are not unified. That causes huge problems to designers, who have to deal with these requirements differently, sometimes even in a one building. Individual regulations define requirements for workplaces, another for schools or catering establishment. For some workplaces (clean rooms in health services), the requirements are not defined at all. Therefore, the author extracted the requirements into the well-arranged tables.

The article deals with practical knowledge from design and installation of pipes for refrigerant distribution in cooling appliances. Pipe system is divided according to its function in a cooling circuit and the text is replenished with a calculation of the correct duct diameter in relation to the recommended flow velocity of the refrigerant in the particular duct part. Attached figures demonstrate different correct and erroneous solutions of pipe system design. Properly designed pipe system for refrigerant distribution ensures good operation of cooling systems.