Issue 3/2023

The article deals with various possibilities and research concepts of controlling heat pumps operating in heating systems. It also presents methods for controlling the thermal performance of heating systems with heat pumps and conc ludes with recommenda tions for the most suitable solution.

The paper deals with the acoustic simulation, evaluation, and measurement of the noise of an outdoor airtowater heat pump unit installed by a single-family house. The contribution deals with several variants of heat pump placement and their influence on the resulting noise situation in the protected outdoor areas of neighbouring buildings and compliance with or exceedance of the hygienic limits.

The paper focuses on the experimental verification of the use of CO2 as a tracer gas for the detection of leakages in air handling systems, instead of the widely used tracer gas of sulphur hexafluoride (SF6 ), which is subject to legislative restrictions. Verification of the applicability of CO2 is accompanied by the definition of measurement uncertainties.

The paper describes the possibilities of modelling rotary regenerative heat exchangers for heat recovery. Based on a literature review, the paper summarizes dimensionless correlations e -NTU used for design calculations and recalculations of the operating states of rotary heat exchangers. Special attention is given to the issue of heat transfer in the heat exchanger rotor channel in the form of a comparison of the available correlations for the calcula tion of the Nusselt number in the laminar flo w region.

The paper evaluates the operation of the heating system of a logistics centre after 5 years of operation, where the heat source is a cascade of air-to-water heat pumps. Particular attention is paid to the real operation of the bivalent heat sources of the system under extreme cold outdoor conditions over the fiveyear period under considera tion, taking into account the assumptions of the original design.

The article discusses the advantages and disadvantages of an ejector application for refrigerant flow circuits. Coefficients of performance for heating and cooling have been evaluated using an example of an air-to-water heat pump design, for several refrigerant circuit variants. On the basis of the results of the analyses, the main advantages of using an ejector were highlighted. They are especially the relatively high coefficients of performance for heating and cooling for a particular circuit design. Finally, the paper discusses the possible risks of using an ejector in a refrigeration cycle for mobile applications and the possible problems in a year -round operation under variable c limatic conditions.