IMPROVING ENERGY EFFICIENCY CABLE PRODUCTION

During the energy calculation is made at different temperatures of the heating surface. The influence of the speed of pulling on the cost of the finished products of cable products. The interrelation of speed broaching and temperature of the heating surface.


Introduction
The manufacturing process of cables consists of several stages: drawing, cure, drawing, extruding, winding on a spool.The most energy-consuming is the cure.This physicalchemical process takes quite a long time intervals (hundreds of seconds) occurs at a low pulling rate and high temperature heat insulating product.It is also necessary to monitor the temperature of the surface of the insulating layer, which should not exceed the temperature of the beginning of the thermal decomposition of the material sheath.
Each plant produced dozens of cable products.They are classified into solid and stranded, power, installation, monitoring, mine cables, control cables, etc.
Table 1 shows the prices for power cables unarmored several manufacturing plants.The purpose of this work to reduce energy consumption and improve resource efficiency of production of cable products.To achieve this goal have been resolved following tasks: 1. Determination of the minimum energy associated with a decrease in temperature of the heating surface.
2. Determination of the effect of speed on the energy consumption of production broach.

Problem statements
When setting objectives assumed that the cable is passed through a specialized camera with different heating temperature (543 K, 593 K).It is considered [1], that the output of such a chamber is a product characterized by a high degree of polymerization of the insulating sheath over the entire thickness [1].The term "complete polymerization" [2] means the end of the chemical process in the insulating layer to the condition φ≈1 (φ -degree of completion of the main chemical reaction).
As a first approximation when modeling the system shown in fig. 1.

Fig. 1.
Scheme for solving the problem of heat transfer area at 0≤t≤t p : 1-cable core, 2cable shell, 3 -the air heating chamber.
It was believed that the cable consists of a core 1 and shell 2. A product with an initial temperature Т 0 and constant speed w c moves through the heating chamber.The shell is heated at a significantly higher temperature 3. Vault chamber temperature (initial temperature of the air in the chamber) Т v taken much more Т 0 .As a result, overheating of the cable insulating layer is polymerized.Weight completion determined by the degree of polymerization of the insulating material and φ describes the quality of the final product.Time of completion of the polymerization (φ≈1 through the entire thickness (r 1 <r <r 2 ) shell) t p is the primary integral characteristic of the process.
When setting objectives into account convective and radiative heat transfer mechanisms.
Selecting a cylindrical coordinate system for modeling due to the fact that the cable products are often multi-layered elongated along the axis of symmetry of the long cylinders [3].To consider setting an axially symmetric (fig.1).

Mathematical model
The system of differential equations of unsteady heat transfer in a partitioned system "heating chamber -air -insulation shell -core cable" (fig.1), corresponding to the physical formulation of the problem, has the form [4,5].
The system of nonlinear nonstationary differential equations ( 1) -( 4) with appropriate boundary conditions is solved by finite difference method [6].Difference analogues of differential equations (1) -( 4) are solved locally one-dimensional method.For solving nonlinear equations, the method of iterations.To assess the reliability of the results of numerical modeling were used algorithms based on the verification of the conservativeness of difference schemes used [7,8,9].

Results and discussion
Consider energy as the temperature of the heating surface of the Ths1 = 543 K and Ths2 = 593 K speed and pulling cable products υ = 1 m / s.
Electricity tariff of 5 rubles per 1 kW / h at the cable company.
processes near boundary between two layers was supported by the scientific schools grant NSH-7538-2016.8.

Table 1 .
Cost of power unarmored cables.