Introduction. Heat dissipation is an integral part of metallurgical production. Excess heat generation can cause overheating of equipment, which can lead to accidents, damage to production equipment, and injury to workers, resulting in significant financial losses. To control excess heat in the metallurgical process, several methods are used:

Metallurgical workshops are characterized by a significant amount of heat generated during various stages of metal production, including heating, melting, molding, and casting [3]. In addition, these processes are often accompanied by the emission of dust and gases, leading to an increased concentration of hazardous substances in the air. This can complicate the working conditions for employees and require the use of specialized protective equipment, as well as the compliance with occupational safety and industrial safety requirements [4]. When working in metallurgical workshops, there is also a risk of fires, explosions, and serious thermal injuries [5].

Insufficient cooling of process installations, such as areas with a large number of power cables or local transformer substations, often causes excessive heat generation and heat accumulation, which can lead to equipment failures [6]. Therefore, it is crucial to carefully monitor temperatures at each stage of the process to ensure a stable and safe temperature condition for production facilities and electrical equipment [7]. Regular maintenance and repair of equipment, as well as monitoring of thermal radiation levels in workshops, are necessary to promptly respond to potential problems and develop strategies to address and prevent them [8]. Despite all available cooling methods, emergencies, non-standard situations, and injuries in metallurgical production remain a significant concern, although in the last ten years there has been a downward trend [9].

Analysis of the existing statistical data on accidents and injuries in the mining and metallurgical industry over the past ten years, as well as assessment of the cooling methods used, has shown the need for more effective measures to reduce thermal radiation and ensure the uninterrupted operation of equipment [10]. In this regard, the authors have developed and modeled a process of heat and mass transfer using a method of pulsating air movement, which significantly improves heat transfer with weak aerodynamic coupling [11]. The aim of this research is to study the effect of pulsating airflow on temperature parameters of air environment in conditions of low speeds and difficult aerological permeability with general ventilation in a room. The article presents the results of physical modeling of heat and mass transfer under conditions of weak aerodynamics.

Materials and Methods. The experiments on heat transfer were conducted using a physical model (Fig. 1), which had the following characteristics [12]:

Figure 1 shows a structure simulating a ventilated room in the form of a cube with sides 1 meter long. The Pulsator device was located in the central part of this volume (Fig. 2 a, 5). Its characteristics are shown below:

When planning the experiment, minimum and sufficient requirements for its implementation were established [15]. Measurement accuracy:

Figure 2 provides the diagram of the laboratory installation. The air flow generator (Fig. 2 a, 1) for general exchange ventilation, simulating the process of artificial ventilation in a room, was located on the left side at the bottom of the laboratory model (in the middle). The height distance from the base of the laboratory installation was 7 cm. The outlet of the niche (Fig. 2 a, 2), simulating a zone of obstructed aerological permeability, was in the base of a laboratory installation in the center. The niche structure itself rested against the back wall of the cube. The dimensions of the niche had the following parameters:

In the part of the niche farthest from the entrance, at a distance of 0.45 m, there was a heat source (Fig. 2 b, 3). The heat source was an incandescent lamp with a power of 25 watts. During the experiments, two types of heat transfer were studied: radiative and convective. Figure 2 provides the layout of the equipment during the experiment.

The experiment to study the processes of heat and mass transfer was carried out with the temperature values recorded by a sensor located on the floor of the niche at a distance of 0.15, 0.25 and 0.35 m (Fig. 2 b). The letters highlighted in red indicate the position of the temperature sensor during the experiment. The experiment was carried out both with stationary (without the use of a pulsator) air exchange and with the use of a pulsating ventilation mode. On each segment, 70 temperature values were recorded for 60 minutes. In accordance with the experimental program, as mentioned earlier, the niche was located on the basis of a laboratory installation, and the temperature sensor was located at measuring points A, B, and C (Fig. 2 b). The measurements were carried out in the lower part of the niche (near the floor).

The second stage of the research to assess the influence of the air movement pulsating mode consisted in the use of a screen that dissipated direct thermal radiation. This screen was located between the heat sources and the temperature measuring points. The screen was installed permanently in one place for all measurements. The screen dimensions were 0.1 x 0.1 m. The screen material was white plastic 0.001 m thick. Periodically, during the heating process, the Pulsator was turned on, for example, at the 18th minute of the experiment. It was noted that the Pulsator operation led to a decrease in the temperature rise in the niche at each measurement point. The measurements were performed using the same methodology.

In general, it was found that at the time of switching on the Pulsator, the temperature increase in the niche was 1.5 times less than when the device was turned off. In the future, similarity criteria would be used to scale the process of turbulent heat transfer in natural conditions.

Results. Based on the conducted experiments, graphs of the dependence of temperature changes on time were constructed. Figure 3 shows the results of these measurements. The absolute and relative errors were 4.45°C and 8%, respectively. The graph with the blue line shows temperature changes when using the screen, and the graph with the green line shows temperature changes (in the range from the 18th to the 30th minute of this stage of the experiment) when the pulsating air movement mode was turned on with the plastic screen installed.

After the experiments, relative temperature increments at each measurement point of stationary (marked in blue on the graph) and pulsating modes were calculated to compare them. After calculating the increments for different modes, the dependencies were obtained. Figure 4 shows a graph of the dependencies of temperature increment coefficient on time using the screen.

Further, these increments were distributed by modes and time ranges. Figure 5 shows dependency graphs of average values of relative temperature increment (ti\t0) on time in stationary and pulsating modes for the entire volume of the niche.

According to this graph, during the first 15 minutes of the experiment, the temperature increased at a slower rate using the pulsating ventilation method, and there was a steady, slight increase. Under the conditions of the steady-state regime of the process under study, the maximum rate of temperature increase was observed.

Comparison of temperature changes over the intervals of 1–15 minutes and 16–32 minutes showed that during the first interval, the efficiency of the pulsating mode was less than the temperature increase (Fig. 6). However, the characteristics remained the same during the second interval (Fig. 7).

Figure 8 shows the values of angular coefficients, which indicate the degree of efficiency of the pulsating mode compared to the stationary mode, at different time intervals. In the range from 1st to 15th minute, the angular coefficient was 3.8 times higher in the stationary mode than in the pulsating mode, which indicated a higher intensity of heat and mass transfer. In the next interval (16–32 min.), this effect was not observed.

Discussion and Conclusion. The obtained dependencies of relative temperature increments with and without the pulsator allowed us to visually compare the processes of temperature increase and obtain the angular coefficient values for these two modes. The coefficients showed that the pulsating mode reduced the temperature rise by 3.8 times within the first 15 minutes at all measured points of the niche, proving the effectiveness of the proposed method. During the subsequent time period, temperature indicators stabilized in all cases and temperature in the niche increased slightly, both with and without the pulsator on.

The pulsation efficiency was observed at a distance of at least three diameters (L = 3d) of the niche under these conditions. We found that each time the pulsator was turned on, a steady increase in turbulent heat transfer occurred. Therefore, we can conclude that this method could be used to regulate the thermal load on various pieces of equipment and several technological processes.

The experiments conducted have allowed us to obtain initial information about the effectiveness of the above-mentioned method for heat and mass transfer. Further work will continue, and experiments will aim to obtain and analyze the dimensional and dimensionless characteristics of turbulent heat and mass transfer.