Аннотации:
Heating of oil and oil products is widely used to reduce energy losses during transportation. The flow in the annular space
of the heat exchanger is complex and depends on many factors. The use of thin tubes in helicoid-type heat exchangers
makes it necessary to take into account the transition of the flow regime from laminar to turbulent. The semi-empirical
turbulence models traditionally used in numerical calculations do not take into account the laminar-turbulent transition. An approach is developed to determine the effective length of the heat exchanger and the temperature of the cold coolant
at its outlet in the case of a strong dependence of oil viscosity on temperature, taking into account the possibility of a
laminar-turbulent transition. Oil is considered as a heated coolant, and water is considered as a heating component. The
novelty of the developed approach lies in the application of the turbulence model, which takes into account the laminarturbulent transition, to the calculation of helicoid-type heat exchangers. For numerical simulation, the Reynolds-averaged
Navier–Stokes equations are used which are closed using γ–Reθt
turbulence model that takes into account the laminarturbulent transition. The results of numerical calculations are compared with the data obtained on the basis of the logmean temperature difference method at constant and variable viscosity. In the case of variable oil viscosity, a transition
from the laminar flow regime to the turbulent one is manifested which has a significant effect on the effective length
of the heat exchanger. The results of numerical calculations can be useful in designing helicoid-type heat exchangers.
