International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In the chemical industry, heat exchangers play a critical role in maintaining process efficiency. However, these systems are prone to frequent failures, often necessitating extensive maintenance or repairs, which in turn adversely affect the overall economic performance of industrial operations. The chemical industry commonly operates in highly corrosive environments, making corrosion the predominant failure mechanism for heat exchangers. Key factors contributing to corrosion-related failures include defects in fabrication and welding, suboptimal material selection, improper water flow or chemistry management, and the presence of corrosive species in water. This study investigates the corrosion behaviour of heat exchangers under various corrosive conditions, utilizing COMSOL Multiphysics for simulation and analysis.

There are many different models and types of heat exchangers depending on the area of use. The type of fluids involved in heat transfer and their temperature play a critical role in selecting the appropriate model. Common heat exchangers include plate exchangers, tube-type exchangers, air-cooled exchangers, and graphite exchangers. In this study, a sustainable and original heat exchanger system was designed to increase energy efficiency and reduce natural gas consumption by utilizing the waste heat from natural gas. The design prioritizes ease of maintenance and cleaning. Detailed engineering analyses were conducted, and critical engineering errors identified in previous heat exchanger designs were resolved. The developed designs were validated through test studies and experiments, leading to the final design after an optimization process.
As a result of the study, a high-capacity, energy-efficient, and sustainable heat exchanger integrated with modern technology was developed.

By using the application package ANSYS Fluent, the numerical simulation of heat and mass transfer processes in the channels of shell-and-tube heat exchanger with compact placement of tube bundles has been carried out. The fields of velocities, temperatures and pressures in the heat exchanger channel were obtained and the conditions of hydrodynamic flow in the channels and the processes of heat transfer in these channels were analyzed. A new construction of shell-and-tube heat exchanger with compact arrangement of tubes in tube bundles is proposed and developed.

During the combustion processes of fuels, fuel gasses are created which flow over the heat exchanger. The flow of fuel gasses brings ash particles which are deposited on heat exchanger surfaces and thus reduce the heat exchange efficiency. The removal of ash deposits from the heat exchanger is performed by a striker. Striker indirectly strikes the floor of the lower chamber of the heat exchanger via the mandrel and transmits kinetic energy to it. The impact results in inertial forces on the layer of deposits that are greater than those of adhesion forces between the surface of the exchanger pipes and the ash deposits. The pipes are loaded with displacement caused by the impact of a mandrel used to clean the heat exchanger, displacement caused by the operating pressure inside the pipe, and thermal elongation. The load of the pipes is cyclic, and calculation was performed according to the standards: EN 12952-3:2012-03 and EN 13445-3:2009. The calculation was performed at critical pipe cross-sections. The Abaqus/CAE2016 software package was used to determine the critical cross-sections of pipes and stress that occur in them. The model was created using beam finite elements. After analyzing the stress and applying the standards, a conclusion is reached on the fatigue strength of the drainage pipes. The heat exchanger pipes are made of austenitic W.Nr.2.5956 and 16Mo3 steels. The pipe with maximum fatigue stress of 208 MPa is made of 16Mo3 steel, which has a tensile strength from 450 to 600 MPa. Young modulus of elasticity at an operating temperature of 383 ° C is E = 173,9 GPa. The permanent strength diagram is taken from EN 12952-3: 2011 standard shows that this material can withstand 107 cycles with such fatigue stress, and the required number of cycles is determined based on the customer’s request which is the projected number of years. The plant is projected on operating 5 years. The designed number of cycles is 350400 cycles, so it is concluded that the pipes satisfy the conditions of exploitation.

The aim of this work is numerical modeling of the hydrodynamics and heat transfer of a shell-and-tube heat exchanger. For the purpose of the study a 3D model with geometric dimensions corresponding to real was created. The simulations under the same boundary conditions as experiment were carried out. The independence of solution by the density and the shape of the mesh were investigated. For verification the experimental values for fluid temperatures at the outlets from the apparatus were used. The simulations of different operation modes in the apparatus were carried out. A modification in the geometry with the aim of raising the temperature on the cold fluid at the outlet was made. Results on vectors, velocity and temperature distribution in the apparatus were obtained. On the basis of the obtained results some design changes of the apparatus in order to improve the hydrodynamics have been proposed. The obtained results can be successfully used in the design, optimization and constructing of this type apparatus, as well as in the educational process.

The description of the experimental energy-efficient ventilation system sheepfold for lambing.