The NUT indicates the actual area of heat exchange, thus, for the same values of minimum transfer capacity and global coefficient, the larger the NUT, the larger the physical dimension of the equipment.
The NUT is the measure of the size of the exchanger, determined by the equation below: (11) With NUT and C.
Details of baffles are show in the Figure 3, and they are in a distance of 4.88 cm. Simulation Considerations The studied flow is based on the following considerations: 1) Permanent and turbulent flow; 2) The fluid is Newtonian and incompressible and the physicochemical properties are constants; 3) Non-isothermal process; 4) There is no occurrence of chemical reactions; 5) It was not considered the gravitational effect; 6) No mass and momentum transfer at the interface; 7) The interfacial drag forces (forces of lift, wall lubrication, virtual mass, pressure and turbulent dispersion of solid) were neglected; 8) The fluid circulating in the shell and in the tube is water. Calculation Memory of the Heat Exchanger For the calculation of the Nusselt coefficient on the tubes side, the correlation proposed by Petukhov, found in  , were used, which is valid for the Reynolds range of 10 ≤ Re ≤ 5 × 10 and Prandtl 0.5 ≤ Pr ≤ 2000, in the way: (1) where f is the friction factor.
Using the ANSYS CFX software was constructed on the domains tetrahedral mesh, with 625,398 and 1,828,214 tetrahedral elements, according to Figure 4 and Figure 5. The Nusselt number is a dimensionless one that relates the convective heat transfer with diffusive transfer being defined as: (2) where h is the heat transfer coefficient (W・m).
The heat exchange process between two fluids that are at different temperature gradients and are separated by a solid wall occurs in many applications within the engineering, and the equipment for this process is called a heat exchanger.
Heat transfer in a heat exchanger usually involves the convection process in each fluid and conduction through the wall separating the two fluids  .
Given the effectiveness and the maximum exchange capacity, it is possible to find the heat transfer between the currents and the thermal conditions of both at the outlet of the shell and tube heat exchanger, as well as the Mean Logarithm of Temperature Differences (MLDT).
(13) where the temperature differences are defined by: (14) (15) For the method (MLDT) the dimensionless parameters P and R are determined: (16) (17) where R is the ratio of the fluids heat capacities and P represents the thermal effectiveness with respect to the cold fluid.
The results were compared with Excel generated worksheets calculated using the existing equations and correlations. Introduction Heat transfer is thermal energy in transit, occurs due to a temperature difference in the medium and can happen by conduction, convection or irradiation.
The thermal exchange process is defined as any operation or operations sequence performed on one or more materials aiming at varying its energy, composition, size or any other physicochemical properties  .