Issue 4/2015

The paper deals with the simula tion of indoor environment in a da ta center a t breakdown of its cooling system. Individual components of the cooling system during the breakdown were studied in detail with respect to their influence on the course of the emergency situation, in particular the influence of the cooling circuit thermal capacity. A complex numerical model was set up in TRNSYS simulation environment to predict energy flows and air temperatures in the data center. The simulation model describes in detail the cooling system including control elements and it takes into account heat accumulation in room constructions. The model represents a real data center and it was calibrated using data from a real emergency situation. The simulation results showed that the backup of water circuit makes possible to extend the operation time of the data center at emergency.

The paper presents a study performed on the case of the church tower of the Sacred Heart of Jesus church in Prague Vinohrady, documenting the application of the energy simulation for analysis of static failures of historical constructions. The simulation software, commonly used for modelling of building energy behaviour and indoor environment quality (BPS), was used to substitute long term monitoring of the real temperature conditions. Software DesignBuilder GUI was used for the modelling, working on a computational core of the EnergyPlus, which is based on the one-dimensional model of conduction heat transfer in multilayer constructions with calculated convection coefficient. The BPS simulation took into account the effects of the climate, such as solar radiation, changes of temperature and humidity, wind speed and direction at the scale of the building model (macro-scale), for the period of one year, with detailed time-step 30 minutes. It assessed the course of the surface temperatures of used as a load in numerical thermomechanical analysis of the construction damaged by the static failures, which is commonly carried out when there is a suspicion of a stress caused by temperature changes. The results of the analysis confirmed the hypotheses that the static failures were formed due to the thermal stress.

The paper describes the current state of the art in the use of simulation by CFD method (Computational Fluid Dynamics) in the field of wind engineering specialized on the evaluation and optimization of wind comfort and wind safety for pedestrians around buildings. It discusses the challenges in the application of CFD method for modelling of atmospheric border layer, such as modelling of flow in the surrounding of the buildings and on the buildings. The paper deals also with the methods to assess the wind comfort and pedestrian safety. on a real scenario case stud y solved in CFD solver OpenFOAM.

The paper is targeting verification of the possibilities to utilize solar systems with long-term heat storage in residential buildings. Several ways are evaluated how to connect the long-term heat storage system with hot-water storage tank (system with and without use of heat pump, different ways of charging the storage tank, variants with stand-by storage tanks). The evaluation of the system is performed by TRNSYS simulation software.

The Blanka tunnel complex represents with its length of 5,5 km the longest city tunnel in the Central Europe and the longest road tunnel in the Czech Republic. The paper describes design and implementation of control algorithms for operational ventilation of tunnel complex Blanka which will be a part of northwest section of the Prague city ring road. The control algorithms are designed on the basis of physical models, taking into account internal and external environment of the tunnel. In addition, the reduction of electrical energy consumption is emphasized.

The basic prerequisite for effective operation of buildings is functional monitoring of consumptions and correct understanding of the obtained data. The appropriate interpretation of measured consumptions can reveal a lot about building operation manners, about effect of undertaken measures (insulation, window exchange, …) and possibly also reveal deficiencies in the heating, ventilation and air-conditioning (HVAC) systems. The paper is aimed to the monitoring of electrical energy consumption. Mathematical model was created on the basis of available measurements and consequently used to compare measured and predicted consumptions. Four different approaches towards energy consumption modeling are compared, namely is discussed use of polynomial models, neural networks, support vector machines (SVM) and autoregressive models. All the methods were verified using data from two different premises: shopping center and university building.

The paper presents the implementation of the Fiala thermophysiological thermal comfort model, which is suitable for evaluating the influence of dynamic and nonhomogenous environment (eg. cabins of vehicles). The Fiala model is currently one of the most advanced models in the field of heat transfer inside and outside of human body. The model also allows to predict the dynamic thermal sensation (indicator DTS) and its original version has been adopted with modifications into commercial programs dealing with heat transfer, such as for example RadTherm or Theseus-FE. We Implemented the Fiala model into Matlab and tested on experimental data available in the literature. The mathematical description of the model is based on partial differential equations describing the time varying 1D heat conduction in the living tissues. The system of these equations was solved numerically using finite-differences method.

The contribution deals with prediction of extent of the renovations of the existing building stock. A common strategy to achieve energy efficiency is utilization of funding programs. It is only one of the options to achieve the established goals, but it is used the most often. The problems are usually obtaining necessary amount of money and the impact on the behaviour of the whole system of deliveries for the implementation of energy saving measures. The basis of the dynamic model is a subsystem of the building stock, which is supplemented by a subsystem of the renovation funding. The model is specially aimed at testing of the impact of repetitive funding programs, including the influence of the investors’ behaviour. Simulation was run for case of the Czech Republic, for a period of ten years with two funding programs. The output parameters are time changes in the inventory of potential projects and refurbished buildings expressed as floor area of buildings.

The paper describes methods to determine critical concentration of gaseous mixture of natural gas (methane) with air, which is formed after leakage of the flammable gas from the disrupted low-pressure gas pipeline. The contributions deals at the same time with the verification of the mathematical calculations with experimental measurements. The appropriate method of calculation can be selected on the basis of the comparison of the calculated results with experimental data. It can reliably describe the spreading of the flammable gas in the enc losed space, and theoretically identify the places of the critical concentr ations.

The article deals with energy simulations used for design support of a new large administrative building of a bank. The presented simulations had a major influence on the design of the air-conditioning system and sources of cold and hea t for ensuring the required indoor environment parameters.