Issue 2/2009

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According to a common practice in our republic, the majority of industrial halls without specific technology-related temperature demands were ventilated only with outdoor air during the summer period. At newly constructed halls, with specific requirements for thermal comfort of employees and with technology-related requirements for the air temperature, utilization of air conditioning is necessary. A correct design of an air conditioning device requires knowledge of real cooling loads during the building operation, determination of their value should be as accurate as possible. At industrial halls with a large nominal power input of installed equipment, the internal cooling load is often a major part of the overall space cooling load. A calculation procedure of cooling load from internal heat sources is explained using examples. Three typical industrial halls were chosen as case studies: a hall with a small number of large heat sources, then a hall withmachinery with a specified temperature demand and finally a hall with a large number of small heat sources.

Despite many calculation tools related to building simulation, the interconnection amongst them is not often feasible with reasonable effort. The effectiveness of information sharing amongst already existing models is one of the key fields of further development. The paper presents the development of a model for simulation of air circulation through air-to-mass exchanger. The model is developed within Simulink environment and is validated with analytical solution. Subsequently, the model including a simple control system is integrated into existing model for building simulation. The paper demonstrates that Simulink is a powerful tool for simulation of systems based on ordinary differential equations. Because of the graphical environment, the model development is very intuitive.

The article deals with a simulation of a new concept of a micro cogeneration unit. This system produces electricity from concentrated solar radiation using Stirling solar engine (SSE) and waste heat can be utilized for heating and hot water supply of a family house. The article presents both the model of the whole system created in MATLAB® software environment and its results as well.

The author draws attention to unsuitable microclimatic conditions at driver’s cab in public mass transport. In summer, the temperatures exceed not only the optimal value but also the sustainable level for a longer exposure. The results show, that thermal comfort at the place of the driver can be reached only using air conditioning.

The part load operation of air cooled condensers and dry coolers is discussed. Different methods of control are compared according to the energy consumption and noise reduction of the heat exchanger.

The article deals with problems related to a comprehensive design process of a noise silencer for HVAC applications. Noise silencers for HVAC duct systems are mostly based on absorption principle. Better noise attenuation can be achieved with rectangular silencers, when compared to circular types. Dynamic insertion loss in particular frequency range is considered to be the main characteristic for HVAC noise silencers. However, a lot of designers forget the next important parameter – the pressure loss. The author focuses on the correct determination of pressure loss and describes possibilities of pressure loss reduction achieved by aerodynamic modifications on the leading and trailing edge of absorptive baffles. There is shown an optimal approach for choosing the silencer according to a quality criterion, which takes into account both noise attenuation in particular frequency range and pressure loss criterion, which is defined in the silencer local pressure loss coefficient.

Biofilm is nowadays quite a well known term. This article gives a more detailed view of biofilm character, structure, and composition, causes of its formation, importance, and influence on materials and mechanical devices and also a view of possibilities of biofilm removal.

Metal substances occurrence in aerosol particulate matter is considered to be a significant factor of health risk. Indoor air metal contamination is affected by contribution from outdoor particle penetration as well as indoor sources (smoking, emission from building materials and use products). This paper is aimed to metal substances investigation in indoor suspended and deposited particulate matter. Higher of content metal has been found in suspended particulate matter in comparison to the suspended aerosol.

With a kind approval of company AL-KO Therm GmbH , the author presents to the readers the optimization programme of this company, which enables an optimized design of ventilation and air conditioning devices and consequently its check in terms of investment and operation costs. The use of this programme will give energy saving devices, even with higher investment costs, an advantage over cheaper, but operationally more expensive devices with higher energy consumption.