The pulsating flow is one of the techniques that can enhance heat transfer, therefore leading to energy saving in tubular heat exchangers. This paper investigated the heat transfer and flow characteristics in a two-dimensional in-line tube bundle with the pulsating flow by a numerical method using the Ansys Fluent. Numerical simulation was performed for the Reynolds number Re = 500 with different frequencies and amplitude of pulsation. Heat transfer enhancement was estimated from the central tube of the tube bundle. Pulsation velocity had an asymmetrical character with a reciprocating flow. The technique developed by the authors to obtain asymmetric pulsations was used. This technique allows simulating an asymmetric flow in heat exchangers equipped with a pulsation generation system. Increase in both the amplitude and the frequency of the pulsations had a significant effect on the heat transfer enhancement. Heat transfer enhancement is mainly observed in the front and back of the cylinder. At a steady flow in these areas, heat transfer is minimal due to the weak circulation of the flow. The increase in heat transfer in the front and back of the cylinder is associated with increased velocity and additional flow mixing in these areas. The maximum increase in the Nusselt number averaged over space and time in the entire studied range was 106%, at a pulsation frequency of 0.5 Hz and pulsation amplitude of 4.5. A minimum enhancement of 25% was observed at a frequency of 0.166 Hz and amplitude of 1.25.

Open-cell foams are attractive for heat transfer enhancement in many engineering applications. Forced pulsations can lead to additional heat transfer enhancement in porous media. Studies of heat transfer in open-cell foams under forced pulsation conditions are limited. Therefore, in this work, the possibility of heat transfer enhancement in porous media with flow pulsations is studied by a numerical simulation. To generate the 3D open-cell foams, the Laguerre–Voronoi tessellation method was used. The foam porosity was 0.743, 0.864, and 0.954. The Reynolds numbers ranged from 10 to 55, and the products of the relative amplitude and the Strouhal numbers ranged from 0.114 to 0.344. Heat transfer was studied under the conditions of symmetric and asymmetric pulsations. The results of numerical simulation showed that an increase in the amplitude of pulsations led to an augmentation of heat transfer for all studied porosities. The maximum intensification of heat transfer was 43%. Symmetric pulsations were more efficient than asymmetric pulsations, with Reynolds numbers less than 25. The Thermal Performance Factor was always higher for asymmetric pulsations, due to the friction factor for symmetrical pulsations being much higher than for asymmetric pulsations. Based on the results of a numerical simulation, empirical correlations were obtained to predict the heat transfer intensification in porous media for a steady and pulsating flow.

The pulsating flow is one of the techniques which can enhance heat transfer, therefore leading to energy saving in tubular heat exchangers. This paper investigates the heat transfer and flow characteristics in a two-dimensional in-line tube bundle with the pulsating flow by a numerical method using the Ansys Fluent. Numerical simulation is performed for Reynolds number Re = 500 with different frequencies and amplitude of pulsation. Heat transfer enhancement was estimated from the central tube of the tube bundle. Pulsation velocity had an asymmetrical character with a reciprocating flow. The technique developed by the authors to obtain asymmetric pulsations was used. This technique allows simulating an asymmetric flow in heat exchangers equipped with a pulsation generation system. Increase in both the amplitude and the frequency of the pulsations has a significant effect on heat transfer enhancement. Heat transfer enhancement is mainly observed in the front and back of the cylinder. At a steady flow in these areas, heat transfer is minimal due to the weak circulation of the flow. The increase in heat transfer in the front and back of the cylinder is associated with increased velocity and additional flow mixing in these areas.

Current paper is devoted to the determination of phenols in surface waters using the method of gas-liquid chromatography on the nozzle chromatographic columns with different polarities of sorbents, in the capacity of which silicone elastomers, polyethylene glycol with the molecular weight of 1500, and polyoxyethylene bis arsenate obtained by arsenating polyethylene glycol-1500 were studied. It was shown that positional isomers, para - and meta – cresols, which have almost identical boiling points, were separated on polyoxyethylene bis arsenate and on the standard sorbents (SE-30 and PEG-1000) they practically do not separate and come out with a single peak. The logarithmic retention indexes were determined for the analyzed phenols and chromatographic Rorschneider polarity factors on polyoxyethylene bis arsenate, which are extremely high for ethanol (factor y) and are associated with the formation of an intermolecular hydrogen bond in the sorbate-sorbent system. It was found that polyoxyethylene bis arsenate had a linear dependence of the logarithm of the retention time on their boiling point and dipole moments. In the case of dipole moments, there was a deviation from the specified dependence for o-chlorophenol, obviously as a result of a specific substituent effect (ortho effect). Polyoxyethylene bis arsenate was used to determine phenols in the surface waters of the Kuibyshev reservoir. For this purpose, a sample preparation system based on the conversion of phenols into brominated derivatives, which have high volatility and are fairly well analyzed by gas-liquid chromatography, was used. A comparative characteristic of the limit of detection of phenols for flame ionization and thermionic detectors was given. As a result of the determination of phenols in the surface waters of the Kuibyshev reservoir, a high content of phenols was found, which fluctuates during the different seasons of the year.