Issue 5/2019

A mathematical model of the heat pump system for wastewater heat recovery was created on the basis of an experimental testing. Its daily operation for hot water preparation was simulated for defined tapping profiles in different applications. The operating coefficient of performance of the system for a use in a family house was assessed to the value of around 2.7. The efficiency has proven to be higher for other investigated applications with higher hot water consumption or with continuous operation. Coefficients of performance of the system exceeding the value of 4.0 were reached for domestic hot wa ter preheating.

The paper describes the thermal model of a photovoltaic (PV) module. Various formulations to calculate the coefficient of heat transfer due to wind were used for thermal balance of the PV module and calculation of the operating temperature in the simulation analysis. The results of the calculation of the annual electricity production were compared with each other. Simulation of the instantaneous electrical power output of the PV module with use of different correlations can vary by up to 15 %. On the other hand, the effect on the calculation of annual production is suppressed and the models var y up to 5 %.

The building enclosure is traditionally assessed by the quality of thermal insulation in the continental climate. As the thermal insulation of a building enc losure has substantially improved over the last decades, solar heat gains comprise more important fraction in thermal balance of a building. The quality of the whole building enclosure could also be assessed by its ability to transmit solar heat gains into the internal environment. Such thermal characteristic should aggregate properties like glazing area in each facade, glazing g-value, the efficiency of fixed shading provisions and the operation of movable shading devices in one composite property. In this paper, the surrogate horizontal effective collector area is used for the characterization of solar heat gains through a building enclosure. The aggregated property is called the effective solar aperture of a building enclosure. Finally, the approximate reasonable values of the effective solar aperture are derived. The reasonable values should lead to a significant reduction in the risk of overhea ting.

In the engineering practice, the equivalent thermal conductivity of air in closed air gaps is used to calculate the thermal behavior of window or facade system details. Thus, the influence of radiation of their surfaces and of the airflow is compensated in individual cavities by adjusting the thermal conductivity coefficient of the contained air. This paper aims to compare the results of models using this method and CFD simulation. A simplified detail of a crossbeam of the Schüco facade system in combination with the insulating triple glazing served as a geometric basis. Crossbeam cavities are modeled first using the mentioned method and then in the CFD model. The results are compared with respect to the thermal transmittance of the detail and the lowest surface tempera ture.

The paper focuses on the measurement of the heat energy supply to small consumers. It deals with comparison of consumption measured by indirect and alternative method. Daily heat consumption was measured for two years. The measurement was performed at a heat exchange station with an output of approx. 20 kW. The results of the measurement are used to evalua te which of the methods is more suitable for the purpose.

The article deals with the effect of the indoor air temperature attenuation during intermittent heating on the energy consumption and the quality of the indoor environment in an existing office building with electric direct heating system. The annual electricity consumption for heating reaches almost half of the total annual electricity consumption of the building for all its services and thus represents a great potential for savings. The building is normally heated throughout the whole working day to the required air temperature of 21 °C, without any intermittent heating mode. Intermittent heating with attenuation of indoor air temperature out of working hours should bring energy savings. The question is what the savings will be and what effect will the measure have on the operation of the building. At first, the building operation settings and assumed building behaviour were verified on a building simulation model. Various operation settings of the heating system were tested in the building during January and February 2018, on the basis of the established assumptions. The findings are described and evalua ted in the article.

The BIM abbreviation has been a very frequent topic of various debates lately; it appears in public and private procurement related to construction projects, and the whole methodology is praised as well as damned. But let’s try to describe its meaning and think about ho w it can affect the future of construction projects.