Influence of heatsink from upper boundary on the industrial premises thermal conditions at gas infrared emitter operation

The results of mathematical simulation of the heat transfer processes in the closed domain, which corresponds to production accomodation with the gas infrared emitter operation condition are presented. The system of differential Navier-Stokes equations in the approximation of Boussinesq is solved. The comparative analysis of thermal conditions formation in the closed domain is carried out taking into account heat withdrawal through the upper enclosing construction and under the conditions of its heat insulation. The essential transiency of the analyzed heat transfer process and the influence of heat withdrawal from one of the outer boundaries on the mean temperatures values in largedimension industrial premises are established. The distinguishing feature of modern industry becomes the rigid savings of energy consumption, as a rule, for the purpose of reduction in the economic expenditures. Localization of systems and heat supply sources is one of the ways for reduction in total energy expenditures for the heating of large production accomodations (local heating of separate workplaces). As the most acceptable version the system of gas infrared emitters (GIE) [1] can be used. Scale GIE introduction in the production is strongly limited because of the insufficient experimental and theoretical study of convective heat transfer in the largedimension accomodations with the gas infrared emitters operation conditions. For the mathematical simulation of the studied process the process description of free convection in air region and thermal conductivity in enclosing constructions (Fig. 1) is necessary. In the problem statement system conjugate heat transfer equations [2–5] was used as a base. All energy from emitter came to bottom medium interface HH. To analyze the significant factors impact on the thermal modes in the manufacturing conditions of GIE operation two versions of the heat transfer problem statement were considered. The first version: heat insulation conditions are satisfied on all outer boundaries of solution region. The second: on upper boundary of solution region y = H (Fig. 1) heat exchange condition with environment is satisfied. The problem was solved in the dimensionless formulation. The system of equations describing the heat transfer in the system has the form: 1 Sh + U X + V Y = 2 X2 [( 1 √ Gr ) ] + 2 Y 2 [( 1 √ Gr ) ] + 1 2 X , (1) This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Article available at http://www.epj-conferences.org or http://dx.doi.org/10.1051/epjconf/20147601006 EPJ Web of Conferences Figure 1. Solution area: 1 – air; 2 – walling construction; 3 – infrared emitter.

The distinguishing feature of modern industry becomes the rigid savings of energy consumption, as a rule, for the purpose of reduction in the economic expenditures.Localization of systems and heat supply sources is one of the ways for reduction in total energy expenditures for the heating of large production accomodations (local heating of separate workplaces).As the most acceptable version the system of gas infrared emitters (GIE) [1] can be used.Scale GIE introduction in the production is strongly limited because of the insufficient experimental and theoretical study of convective heat transfer in the largedimension accomodations with the gas infrared emitters operation conditions.
For the mathematical simulation of the studied process the process description of free convection in air region and thermal conductivity in enclosing constructions (Fig. 1) is necessary.In the problem statement system conjugate heat transfer equations [2][3][4][5] was used as a base.All energy from emitter came to bottom medium interface H H .
To analyze the significant factors impact on the thermal modes in the manufacturing conditions of GIE operation two versions of the heat transfer problem statement were considered.The first version: heat insulation conditions are satisfied on all outer boundaries of solution region.The second: on upper boundary of solution region y = H (Fig. 1) heat exchange condition with environment is satisfied.The problem was solved in the dimensionless formulation.
The system of equations describing the heat transfer in the system has the form: 1 Sh g -acceleration of gravity, m/s 2 ; a -thermal diffusivity, m 2 /s; -thermal expansion coefficient, K −1 ; Bi = L/ -Biot number; -coefficient of heat exchange between the external environment and the area under consideration solutions; Pr = ν t /a -Prandtl number; T 0 -temperature of the gas and solid at the initial time, K; U , V -dimensionless velocity; -solid wall thermal conductivity, W/(m•K); 1,2relative thermal conductivity; ν t -dynamic molar ratio (turbulent) Viscosity, m 2 / s; -dimensionless time; n -vector normal to the surface; -dimensionless analog current function.
In the second variant, the boundary condition (6) when y = H has the form: where e -dimensionless environment temperature.
In solving the problem (1)-(10) the algorithm [4, 5] developed for the numerical solution of natural convection in closed rectangular regions with local energy sources was used.Accounting for the turbulence effects produced in the approximation of algebraic Prandtl model: where l m -the mixing way; x,y -coordinates, m; -velocity component, m 2 / s; k -the universal constant of proportionality is independent of the Reynolds number.To accomplish the task the following values of the dimensionless temperature were used for the heaterit = 1, the initial -= 0, for the environmente = −0.1.
Figure 2 shows typical results of numerical conjugate heat transfer modeling for two options: taking into account the heat sink from the upper boundary y = H of solution field and insulation provided on this border.
Temperature distributions (Fig. 2) in considered solution area illustrate the intensive circulation of air near the heater surface and bottom enclosing structure heated by a heat flow from GIE.It is important to note that the temperature reaches the maximum values near the heater surface for the two variants of the problem statement.
Due to the heat sink from the top surface of the reinforced concrete slab the air temperature near it is much lower than in the case of upper border thermal insulation.The obtained mean air temperatures values (Fig. 3) in the closed domain indicate a significant heat outflow to the environment (Fig. 2).

Figure 2 .
Figure 2. Temperature field (a, c) and isolines of the stream function (b, d) in terms of upper boundary (a, b) thermal insulation and heat sink at the upper boundary (c, d) for time moment t = 60 000.

Figure 3 .
Figure 3. Average air temperature values of the air inside the field solutions for the variant with the upper limit of the heat sink (1) and its insulation (2) for the time t = 60 000.