Abstract:The paper deals with the hydrodynamic properties, i.e. the consumption of mechanical energy expressed by pressure drops within a helium loop intended for the testing of decay heat removal (DHR) from the model of a gas-cooled fast reactor (GFR). The system is characterised by the natural circulation of helium, as a coolant, and assume steady operating conditions of circulation. The helium loop consists of four main components: model of gas-cooled fast reactor, model of the heat exchanger for decay heat removal, hot piping branch and cold piping branch. Using the process hydrodynamic calculations, the pressure drops of circulating helium within the main components of the helium loop were determined. The calculations have been done for several defined operating conditions which correspond to the different helium flow rates within the system.

Nowadays, the operating nuclear reactors are able to utilise only 1  of mined out uranium. An effective exploitation of uranium, even 60 , is possible to achieve in so-called fast reactors. These reactors commercial operation is expected after the year 2035. Several design configurations of these reactors exist. Fast reactors rank among the so-called Generation IV reactors. Helium-cooled reactor, as a gas-cooled fast reactor, is one of them. Exchangers used to a heat transfer from a reactor active zone (i.e. heat exchangers) are an important part of fast reactors. This paper deals with the design calculation of U-tube heat exchanger (precisely 1-2 shell and tube heat exchanger with U-tubes): water -helium.

There are the various types of heat exchangers. The selection of the heat exchanger right type is the first basic assumption for its optimal operation. The heat exchanger calculation itself is another prerequisite for its optimal operation. This article deals with the variables which are usually used to describe the stationary operation of any recuperative heat exchanger with two incoming and two outgoing streams. The knowledge of these variables, including the facts resulting from them, is necessary not only from the point of view of the calculation but also from the point of view of the evaluation of the experimental data of any heat exchanger. The variables values needed for the calculation of heat exchangers, so-called key variables, must always fall within the values range determined on the basis of generally valid knowledge about heat exchangers. The article also deals with the determination of the limit values defining the values range of these key variables.

The aim of this work is to investigate a heat performance of a Multi-Layered Oscillating Heat Pipes Heat Exchanger (ML-OHPHE) for the application of heat recovery in heating, ventilation and air conditioning systems (HVAC systems). The heat exchanger is investigated experimentally under different conditions of heat loads and filling ratios. The experimental data results are compared to the data obtained from Honeywell’s UniSim® Design Suite software. In the end the NTU analysis of the ML-OHPHE is done and a value of overall heat transfer coefficient is calculated. The results of the experiments indicate that the ML-OHPHE could serve as a completely passive heat transfer device in the application of heat recovery in HVAC systems.