Issue 4/2009

Inertia of Start Up and Cooling of Radiators

Abstract...

Authors present a new method for determination of thermal inertia of start-up T63N and cooling T63CH of panel radiators based upon the thermo-vision recording of the surface temperature. A brief description of the experiment is supplemented with the analysis of determination of a presentable value of the mean surface temperature, problems of the T63N and T63CH determination and the brief description of models in the environment Matlab/Simulink and Excel. The provided results result in the usability of the thermo-vision recording with respect to the specified task and the necessity of monitoring the course of the radiator surface temperature in its entire surface, particularly at the start-up. The radiator cooling corresponds to the behavior of the 1st range system while the characteristics of the start-up minimally to the 2nd range, which has to be reflected both in the determination of relevant inertias and simulations. The model of cooling, which ensues from the energy balance is showing a good concord with the experiment (max. relative deviation up to 6 %), the calculation ensuing from the analytic solution only up to 3%. The statistical analysis of the measured data was used formodeling the start-up.
Jančík, L., Bašta, J.154 - 157
Analysis of ventilation heat loss for various ventilation rates

Abstract...

The paper deals with the analysis of ventilation heat loss in case of various ventilation rates. A number of scenarios were analyzed for four ventilated spaces (classroom, fit center,movie theatre and an apartment). In case of the classroom the ventilation rate was set (in compliance with the decree 410/2005 Sb.) to 20 m3.h-1 and 30 m3.h-1 per person respectively. Model cases of the fit center and the movie theatre were simulated with the ventilation rates of 15, 30 and 50 m3.h-1 per person. Model situation of the apartment was simulated for the nominal ventilation rate of 0,5 h-1. Every scenario was analyzed with and without the use of heat recovery. The contribution of heat recovery to annual energy balance was evaluated. The internal heat gains and solar heat gains were not considered in the balances. The TRNSYS v. 16.1 was used as a simulation tool.
Janírek, S., Charvát, P.158 - 162
National Museum in Prague

Abstract...

The article of this author appears to be rather unusual in the VVI magazine. It ensued not only from a detailed technical research of existing heating and ventilation system installed in the National Museum but in fact from a historical exploration regarding the original system that was designed during the building designing and changes that occurred during the construction of the building, as well as later within both successful and less good reconstructions in the Museum history continuing for 125 years. The author introduces readers with the history of the National Museum from its establishment in the year 1818 under the name of “Patriotic Museum”, a ceremonial declaration of noblemen until the building completion in the year 1891. The next part begins with the detailed description of original system of heating and ventilation designed by Ing. Kelling from Dresden until uncovering deficiencies, which led to complaints of employees “due to the air heated with a coal dust and oversaturated with mould that streams in rooms and saturates them with smell so that people get sick.” There to the text are attached copies of historical drawings, which, even reduced, are then sketching in technical solutions of heating and ventilation systems. Further, there in the article are described daring and successful reconstructions of the system from the year 1922, as well as those less good that were performed during fifties and seventies of the last century. At the same time, the author documents the current situation of the system of ventilation that suffered most of all during the aforementioned incorrect reconstructions. The author thinks in the conclusive part of the article about exaggerated microclimatic requirements of certain Museum curators and warns about the danger of probable irreversible damage of the building and interiors at usage of extra high-tech air conditioning. However, he states possible solutions of the system adjustments both in the historical building and in the building of former Federal Parliament that was acquired for the National Museum, at the conclusion of the article.
Petlach, J.163 - 174
The gas pressure reduction at a low noisiness

Abstract...

It is often necessary to reduce the pressure of any gas under a significant pressure drop in different pipeline systems serving for transportation of gases. An increased noisiness surrounding the location of the pressure reduction is usually associated with the expansion, whereby the gas pressure reduction is achieved. Authors are engaged in the article in the problem from the viewpoint of both thermodynamics and acoustics. Their give attention to the design of the gas pressure reducer, at the conclusion of the article. The procedure of the calculation and the selection of the reducer geometry (sizing) is shown in a specific example.
Nový, R., Kučera, M.175 - 179
Mathematical Modeling Hybrid Photovoltaic-Thermal Liquid Collectors

Abstract...

Author informs readers on a mathematical model, which allows to assess the suitability of hybrid photovoltaic-thermal liquid collectors (PV/T) construction with respect to electric and thermal efficiency. Concurrently, he refers to risk of damage or lifetime limitation of photovoltaic modules when integrated into building envelope without possibility of efficient cooling.
Matuška, T.180 - 186
Energy Assessment of Buildings in Czech and Slovak Republics

Abstract...

The author describes certain aspects related with the assessment of the energy intensity (demand) of buildings in the Czech Republic and Slovakia. He often refers to omitted parts of the assessment and problematic examples, for which required values cannot be achieved by the assessment pursuant to existing Regulation no. 148/2007.
Šafránek, J.187 - 188
Tests of Environmental Engineering Equipment in New Buildings

Abstract...

The author describes in his article the existing practice of handing the newly installed environmental engineering systems over to clients and refers to persisting insufficiencies regarding this agenda and their consequences. He expresses his opinions substantiated by his long-term experience in this field of activity together with very significant recommendations.
Poledna, V.191 - 193