Issue 1/2016

The paper focuses on monitoring, analysis and description of the thermal dynamic of a panel radiator outside the thermally steady state. It is based on the temperature field distribution on the front side of the heat exchange surface, monitored by the thermal imaging camera. Monitored radiator was the Korado Radik classic Type 10 in modular size 500 × 1000 mm with one-sided connection from the top to the bottom, in the heat-up phase. The thermographic image of the front plate was divided into 9 parts with equal surface area. In each of the parts were graphically assessed the values of the transport delay, dead time, heat-up time, time constant and heat-up inertia, as the dynamic variables describing the speed of change of the thermal state. The relationship of these values is described, with respect to the geometry of the particular radiator and the time-dependence of their change.

The contribution evaluates the effect of three important parameters (combustion air shortage, not-well maintained chimney and boiler) on the change in quality of the natural gas combustion and operation safety of the appliance. The common gas boiler with atmospheric burner was used for the experiment. The limited air supply, poor draft conditions and not-well maintained chimney were simulated by closing the chimney damper. The not-well maintained appliance was simulated by covering the boiler heat exchanger. The results show that the combustion gases were released to the testing space at approx. 50% closing of the chimney damper and approx. 80% clogging of the boiler heat exchanger. 10x higher concentrations of poisonous CO comparing to the normal operation were measured for 60% clogging of the boiler heat exchanger. Regular maintenance of boiler and chimney increases opera tion safety of combustion a ppliances.

Micro Cogeneration is one of the pillars of the decentralized energy supply, as a part of the so called Smart Grids concept. The economy of deployment of a micro cogeneration unit based on Stirling engine is evaluated for the conditions of the Czech Republic in the years 2012 and 2015, using a parametric balance model of a family house with known data about the energy consumption. There were considered two cases, with standalone unit and in parallel with electricity accumulation. The results of the calculation show relatively high absolute values of savings, but the simple payback period for the micro cogeneration unit is over 26 years in all cases, which makes the micro cogeneration for family houses still hardly applicable. Results may however significantly vary with respect to the actual diagram of the electric energy demand. In general, the unit is suitable for buildings with higher consumption of both hea t and electricity.

Unlike in the case of refrigeration systems with carbon dioxide, the temperatures of the heated heat transfer medium usually predetermine the operation of heat pumps with CO2 to supercritical cycle for the whole year. The article follows two basic applications, i.e. with large temperature increase of the heated heat transfer medium and with small temperature increase. It explains the advantages and disadvantages of use of the carbon dioxide as a refrigerant in hea t pumps by comparison with subcritical c ycle of another refrigerant.

In the previous article the attention was paid to the rules of the FMEA methodology. This article concretizes them further and sets out the criteria for the practical use of the FMEA methodology in the field of facility management. For clarity, a questionnaire survey was used in five buildings. Its results serve as a basis for the development of a very specific FMEA methodology, as described below. The outcome is a description of the operation although speculative, yet based on the real knowledge derived from the operational practice. This article includes in addition to the definition of the criteria and their individual values also determination of the risk priority indica tor.

The paper describes results of humidity measurement at the wing G4 of the historical building of the maternity hospital U Apolináře in Prague, where ventilated air cavity was implemented during the restoration, in order to reduce humidity in the masonry. The experimental measurement verified the theoretical assumptions of the efficienc y and functionality of the used rehabilita tion method.

The paper presents method to determine outdoor air states in winter and summer, for design of heat exchangers in ventilation and air-conditioning systems. The climatic data from the last 30 years (1985-2014) has been used for the determination. The output is tabular values of temperature and enthalpy of the outdoor air which were inserted in the annex of the standard ČSN 12 7010/Z1 on the basis of the presented analysis, with a defined percentage incidence for the 35 selected cities of the Czech Republic. The annex of the standard is accompanied by a commentary, which provides guidance on the use of the presented c limatic data.

The paper shows, on the example of one particular badly done implementation of a solar thermal system at a residential building in Prague, faults in its design (and subsequent implementation), which are not unique. Improper selection of elements with limited size leading to reduced function and inefficient operation do not occur only in small systems assembled by inexperienced companies, but also in large systems implemented at residential buildings by well-established developers.

The number of installed automatic biomass burning low-power boilers has significantly grown in the last decade. The ecological benefit of burning biomass in these devices depends not only on the design of the device, but also on the algorithm controlling the combustion process. One of the important input data for proper function of the current control algorithms is the calorific value of the used fuel. This information cannot be continually monitored in an economically viable way. The contribution presents a mathematical model of the combustion process, which allows continuous estimation of the fuel calorific value, based on the values of the other measured quantities.

The active fire safety devices, by which are in the contribution meant especially electric fire alarms, stabile fire extinguishing means and devices for smoke and heat removal, are an important part of building security systems. For the proper function of these systems it is necessary to pay attention to the priority how to put into operation the particular device, their coordina tion and interaction between them. The principles of the prioritizing how to put into the operation the individual active fire safety devices are described on the basis of the reasons for the devices installation and their priority or eventually secondary protection targets. The attention is paid also to the coordina tion of the fire safety means.