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<p>This paper deals with simulation of the fluid flow in a stirred curved-bottom vessel equipped with three curved blade impellers. The power number and the impeller flow rate number are dimensionless characteristics of the system determined from simulation results and compared with relevant experimental data or data from the literature. The model of the system was created in the conventional Gambit and Fluent program. The system is solved for two designs — for an unbaffled vessel, and for a baffled vessel.The vessel is filled with water and the impeller speed            is 100 min⁻¹. Three turbulent models were used for the solution: k-<em>ε</em>, k-<em>ω</em> and RSM. The results were compared with experimental data or data from the literature. The k-<em>ε</em> model had the smallest demands on processor time, and the results compared satisfactorily with the experimental data. The model provides comprehensive information about the characteristics of the system.</p>

Oil is necessary for most of the heat pumps, cooling and freezing equipment, for proper operation of the compressor and other moving parts. Speed of the refrigerant vapor in the critical section, which is suction piping, is strongly dependent on the evaporating temperature, but also on the actual device performance. Well-designed piping is essential to the proper function of the cooling devices or heat pumps and affects the efficiency of the device. The aim of this paper is to describe problems of returning of oil in refrigerant devices and investigate the exact solution of design of refrigerant speed for carrying the lubricating oil in all segments of refrigerant pipes. Paper is based on facts obtained during developing of new refrigeration equipment. The resulting proposal of the device was numerically verified.

Paper deals with the test procedure for evaluating performance parameters of the heat pump air water system. The objective of measurements was tuning errors and optimizes the work of the whole system. The main aim was to find the most acceptable evaporator with which the heat pump COP reached the best results. Choosing of the evaporator consisted of comparing the operating and performance characteristics of individual exchangers.

The paper describes the importance of monitoring the dust in the atmosphere of human life. It deals with the issue of dust in air ducts, approaching the methods that can be used to detect the amount of dust. For conditions for buildings in the Czech Republic there is created the methodology of quantitative and qualitative evaluation of dust sediment for the needs of HVAC and other building surfaces. The scale for visual evaluation was created and it has been elaborated the assessment of kind of particles contained in dust.