Issue 3/2008

The article draws attention to some incorrect conceptions of basic thermodynamics laws and elucidates the concept of heat as transmitted energy. Possibilities of using exergy for evaluation of heat energy utilization for the assessment of stratified heated–water storage perfection, for evaluation of recuperative heat exchangers effectiveness and for an energy audit of a heat economy of a building are described.

The article deals with an energy simulation of the conference room in General Health Insurance Company branch office in Brno, which is an example of modern administrative building with highly glazed façade. The simulation was carried out using TRNSYS 16 code with the aim, to assess the influence of increased portion of glazed areas on the energy consumption of heating and air conditioning under condition of good indoor environment. The effectiveness of various kinds of solar protection was evaluated as well.

The paper focuses on development of a simple method for design of optimal dimensions of earth-to-air heat exchangers (EAHX). The characteristic problem of the EAHX design is whether the extension of the pipe and/or addition of another pipe (decrease of air flow rate per one pipe) will lead to the thermal improvement which will balance the increase of investment costs. Therefore, a design method is developed in order to facilitate the design of EAHX.

Operational behaviour of a heating system depends among others on the heat inertia of radiators. A transient characteristic of panel radiators at different connection concept was examined. Theoretically derived transient characteristics of a warming or cooling process lead to first-order elements. Experimentally determined courses show that radiators behave different during a warming or cooling-down. They are second or higher-order elements during a warming. For the duration of a cooling-down, they act similarly as the first-order elements. Time constants of the rise and cooling time related to 63 and 90 % of the final heat outputs were obtained from the time changes of surface temperatures evaluated thermo graphically. The dead and rise time ratio during a warming is about 0,23. The ratio of the cooling-down time to 90%and 63%was determined approx. 2,5. The methodology will be used to explore sectional radiators characteristics.

Building heat supply from unconventional sources is acquiring its importance. The heat demand of energy saving houses can be to a great extent covered by the solar energy utilization. The feasibility of combined heating concepts can be assessed by an economical calculation of the investment payback period. An example of a dynamic economy calculation is described in the article.

Primary aim of the work was the charting of the aerosol particles concentration changes in the room heated by fireplace insert, or more precisely to find out how the 24-hours imissions concentration limit PM10 50 ?g/m3 under common house operation. These measuring were followed by the controlled experiment having the aim to state how the natural infiltration, combustion air flow through the fireplace and depositing processes participate on concentration reducing.

The second part of the article (completion from VVI 1/2008) is focused on heating and air conditioning system design in a presentive administrative building. Basic technical and philosophical assumptions of possible solutions are explained and conveyed in details. A proposal of a technical solution of heat and cold sources connection is shown in schemes for a winter and summer period, including possible geothermal energy utilization for a winter period. Annual specific savings of operational costs as compared to a standard solution is given at the end.

Article deals with energy consumption of buildings heated by a heat pump. For dependence of COP on the heat source temperature, values measured by a renowned Swiss laboratory are used which published measurement results of 34 heat pumps air-water and 74 heat pumps brine-water. The article contributes to implementation of the European Directive No. 2002/91/ES in the Czech Republic.

The author compares the process of electric energy production in various power station types. The nuclear type, the fossil fuel burning, coal and gas type and alternative sources are mentioned. The impact of SO2, NOx, CO and particle emissions, as well as CO2 are evaluated. The economy of all types is taken as most important point of classification of all types.

The authors of the article deal with the problems of sorted taking of emissions sample – PM10 fraction. They indicate the results of cyclone 78 mm checking measuring as PM10 sorting machine. On the dusty testing line the criteria dependence Stkm = f(Re) was found out which indicates the change of cyclone separation abilities depending on volumetric flow. By analysis of this dependence it was stated that it is possible to use cyclone 78 mm as PM10 sorting machine at emissions solid particles measuring in the range of common temperatures of 0 up to 200 °C and common flows of exhausted sample of 2 up to 6 m3/h.

For reliable and economical operation of cooling and air conditioning devices and also the heat pumps there is need of a regular operation parameters and the technical conditions check. Such a check is also a preventive measure, which can indicate some discrepancies in the device operation and call attention to possible failures, which is possible to avoid and ensure the operation reliability, personal, property and environment protection. Because new legislation and standards for appliances containing certain fluorinated greenhouse gases insist on specific regular check, the cooling device diagnosis is not just need but also the law requirement. In the article are described required regular checks, considered values, their importance for the device function and modern measuring instruments suitable for the diagnostics.