Issue 6/2018

The article presents a virtual model of a standing person in an indoor environment. A virtual manikin is placed in the room with displacement ventilation where the cold air supplied to the room at low velocity is heated by heating sources and rises up due to buoyancy forces. The calculation is carried out for three different turbulence models: k-w SST, k-e Realizable and k-e RNG. The simulation results are compared with experimental data using velocity and temperature profiles in four transverse planes. As a result, the verified model of a person is obtained that can further be applied to the particular conditions.

Numerical simulations are becoming an integral part of the design procedure of buildings, building systems and technologies allowing for not only evaluating the building energy demands and indoor quality but also for studying the influence of various design parameters and aspects of a building’s internal microclimate. In this case study, a numerical simulation of an internal microclimate in an industrial building in the simulation software BSim 2002 was performed in order to assess the internal microclimate, examine the effect of precooling and determine the required cooling capacity. Furthermore, this article deals with the analysis of the influence of excessive internal gains caused by bogie-hearth chamber furnaces and their implementation into the simulation software. The results illustrate the minor effect of precooling for this case study and the insufficiency of the cooling ca pacity in the investiga ted industrial object.

This paper deals with simplified lumped parameter thermal models of a building. Lumped parameter building thermal models break down building components into a small number of temperature-uniform parts and can be graphically depicted in resistance-capacitance (RC) thermal circuits. The number of unknown variables is extensively reduced which, as a result, considerably increases the speed of the calculation. First, three principal lumped parameter building thermal models are described. Simplifying assumptions on the lumped parameter models are commented on. Then, a simple method for estimating the input parameters from the available information about the buildings is proposed. Finally, comparison with the measured data is reported.

The paper presents the problem of unsatisfactory indoor environmental quality in the Chapel of Holy Stairs in the north of the Czech Republic, which is represented by a high value of air moisture leading to the degradation of the historic interior and frescoes. In order to understand the overall hygro-thermal properties of the airflow in the chapel, monitoring of the air temperature and relative humidity in the chapel and the cloister was carried out. The monitoring data, which provides a basis for examining the initial condition of the Chapel, is used for the calibration of the numerical model developed within the current research. The model is created in a simplified form based on physical principles and the heat balance method. The numerical model enables one to find a suitable control algorithm for the adaptive ventilation system The main aim of this work is to present the benefits and limitations of adaptive ventilation. The analysis highlights the influence of the controlled air supply on the indoor environmental quality and the overall reduction in the amount of air moisture.

The paper deals with the customisation of the supply air temperature in a personalised ventilation system and its impact on the air flow, the efficiency of the ventilation, and the thermal comfort of the human body. The system was designed to enable customisation of the surrounding environment conditions mainly for people working in open space types of offices. Our measurement evaluated the system design and efficiency in different temperature states of the air: for the isothermal flow and for the heating and cooling of the supply air. A prototype of the micro air handling unit (a device for personal air customisation) was used for the measurement, a thermal manikin was used to simulate the convective boundary layers around a sitting human body. A Particle Image Velocimetry (PIV) was used to measure and visualise the air conduction and airflow interaction. The thermal manikin was also measuring the thermal comfort of the user in different modes of operation.

One disadvantage of highly insulated buildings is their overheating, with the subsequent necessity of removing excess heat. This is often done via mechanical cooling. However, increased energy consumption related to mechanical cooling is far from compatible with achieving zero-energy buildings. This paper presents a detailed description of a control mechanism that can be implemented in newly designed or even existing buildings with a VAV (Variable Air Volume) ventilating system, which leads to a significant reduction in the annual energy consumption of mechanical cooling. A control strategy has been developed 40% when using ventilative cooling. The maximum efficiency was found in the range between 0.5 and 0.7 times the nominal volumetric flow rate.

The increasing digitalisation of data is resulting in the need for ever greater computational capacity, which in turn leads to the increasing energy consumption in data centres. A large percentage of this energy use arises from the need to mechanically remove an enormous amount of heat from the data centre environment. In fact, in current practice, the mechanical infrastructure (especially cooling systems) of the data centre accounts for up to half of the overall energy consumption. To reduce the energy consumption of the mechanical infrastructure, several economisation methods are commonly implemented in cooling systems, one of which is the application of a direct air-side economiser addressed in the current research. The use of an air-side economiser has been shown to lead to major savings of the cooling electricity demand, and, as such, it has been widely used as a necessary addition to conventional cooling systems. This study analyses the energy breakdown of data centre cooling systems that include an air-side economiser in order to determine which components within the system are responsible for the major energy consumption. This study investigates, via a computational simulation, the impact of the use of a conventional cooling system and a system with an air-side economiser on total energy demand in three locations representing different climate regions in Europe. The study is especially focused on the energy demand related to the humidity treatment in the data rooms, since the effect is rarely considered in the overall DC energy balance. The results demonstrate, as expected, that the air-side economiser can yield major savings of around 62.5% to 78.7%, depending on the given climate regions. However, the key result of this study is that the humidity treatment necessary for the direct air-side economiser system may consume up to 34.8% of the total energy demand of the cooling system with the air-side economiser.

This work highlights the Building-Integrated Photovoltaics (BIPV) potential in two urban areas with different characteristics in the city of Prague. The representative building blocks were selected and the CitySim software tool was used for the assessment of the hourly irradiation profiles on each surface over a one-year period. Considering appropriate irradiation thresholds, suitable surfaces were then quantified. Integration criteria are discussed and suitable BIPV applications are proposed considering, not only energy performance, but also their impact on the quality of the built environment. The Photovoltaic (PV) potential is compared with the estimated local electricity demand derived from the population distribution within the building block. Analysis indicated that only 5.5% of the total area can be used in Vinohrady and 13.7% in Jizni Mesto contributing by 32% and 31% on average on the hourly electricity demand, respectively. The PV generation exceeds the local non-baseload demand during the summer period, but is less significant during winter. A preliminary financial analysis reveals a payback time of 17.5 and 20 years for Vinohrady and Jizni Mesto areas, respectively. It is evident that, even in the areas with a sensitive built environment, adoption of solar energy is still possible for balancing local electricity needs.