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Flow-mixing is common in technological processes, and both ejectors and turbofans can produce an interaction between flows with different energy potentials. Ejectors have been extensively used, and their analytical models have been widely presented. To the best of the authors' knowledge, there is a lack of studies exploring the efficiencies of turbofans. The goal of this paper is to compare thermodynamic processes in these devices. Their efficiencies are compared in terms of compression and entrainment ratios. A comprehensive one-dimensional subsonic thermodynamic models of the ejector and turbofan are presented. The quantitative indices are obtained for the same initial conditions expressed as the ratio of differences in enthalpies for ideal compression and ideal expansion. When initial conditions are equal to the numeric value of the combination of the isentropic efficiency of the evaluated components (numerical case 0.16), both devices have the same efficiencies; at lower initial conditions (numerical case 0.10), a turbofan's entrainment ratio is 1.5 times and compression efficiency 1.25 times higher; at higher values of initial conditions (numerical case 0.28), the ejector is more efficient. Such distinctive characteristics of turbofans and the nature of their variation may correspond to the specific application areas of technological equipment that require certain flow-mixing parameters. [ABSTRACT FROM AUTHOR]

This paper analyzes an experimental heat pump used for heat recovery in a mechanical room ventilation system. The aim of the work is to examine the operation, control logic of the heat pump and evaluate the possibilities of its operation modes, cycle control by outdoor air temperature. A review of scientific literature and experimental tests of the heat pump were performed to achieve this goal. Tests were performed in three stages, after each stage, according to the results obtained the heat pump stand was improved and experimental modes were adjusted. During the experiment, the tendencies of the heat pump freon and air involved in the heat exchange parameters are analyzed with different combinations of expansion valve positions and compressor power. Knowing these experimental characteristics, the extent to which the combination of these two controls can be used to efficiently control of the heat pump according to the outside air temperature is assessed. Based on the results of the research the heat pump control algorithms (depending on the variable outdoor air temperature) are prepared. [ABSTRACT FROM AUTHOR]

The paper analyses the innovative internal blinds, which allow to use the solar energy, received through a window for a heating, more efficiently and to ensure a greater air velocity due to the convection. Blinds are constructed that one side is covered with material, which absorbs the solar energy and the other side is reflective. Thus, there is an ability to control an amount of absorbed solar radiation and air supply temperature between the window and the blinds. In addition, the construction of the air to provide locating elements. The elements for air deflection are additionally foreseen in the construction. Due to the natural circulation cold air falls between the blinds and the window, then warms up and rises to the top. The paper presents an empirical and theoretical assessment of an operation of the blinds. In addition, the analysis of the experimental researches of an air flow intensity and a dependency of temperature increase from external (climatic) conditions is performed. [ABSTRACT FROM AUTHOR]

The article presents results of an effective operation analysis of VGTU Environmental Engineering Faculty southern facade integrated unglazed transpired solar collector. During previous research the importance to evaluate influence to ventilation system by such type of collectors was observed. The assessment of analysed collector aerodynamics showed that under specific solar radiation and air flow conditions the amount of energy generated by collector could be smaller than the energy quantity consumed by fans for air suction. The study provides analysis of the coefficient of performance rates and quantities of generated and consumed energy under different operation conditions. The effective operation conditions of collector committed during this research could be useful for designing or creating algorithm for such device. [ABSTRACT FROM AUTHOR]

While evaluating the energy savings potential in buildings of different function we face the energy balance of current situation evaluation problem. Generally the data of energy flows quantities and the nature of their dynamics are agregated and do not reflect the indicators of the achieved microclimate. Therefore this article analyses the energy balance following the example of one-year data collection analysis in a company's building complex. The investigated problem is evaluated by the system analysis approach, i.e. the analysed object system is divided into separate subsystems which have been simulated individually but considering the subsystems joint relations in the system. The methods applied in this work are heat and mass balance of separate subsystems and statistical analysis method. The statistical analysis was used for the evaluation of the statistical reliability of the accumulated indicators (temperature, relative humidity, etc.). [ABSTRACT FROM AUTHOR]