# Influence of Burner Nozzle Parameters Analysis on the Aluminium Melting Process
## 2 Experimental Research
### Heat Balance of Process  
The impact of air nozzle optimisation on the process of aluminium ingot melting needs to be determined from the heat balance results. As already mentioned above, a critical parameter in the analysis of the impact of the increased oxidizer oxygen concentration is the time the charge needs to reach the temperature of 740 \({}^{\circ}\)C. The melting time, \(\tau\), is primarily affected by the change of the overall heat transfer coefficient, \(\alpha_{o}\), to the charge in the work area. The total time required for the entire technological process is as follows:  
\[\tau=\frac{Q_{UH}}{\alpha_{o}\Big{(}\overline{t_{f}-\overline{t_{b}}}\Big{)}S}, \tag{12}\]  
\[Q_{UH}=Q_{UH1}+Q_{UH2}+Q_{UH3}. \tag{13}\]  
\(Q_{UH1}\) is the heat required for heating the material to the melting temperature, as follows:  
\[Q_{UH1}=m_{Al}\Big{(}c_{t,Al2}t_{2}-c_{t,Al1}t_{1}\Big{)}. \tag{14}\]  
\(Q_{UH2}\) is the heat required for melting the material, as follows:  
\[Q_{UH2}=m_{Al}l_{Al}. \tag{15}\]  
\(Q_{UH3}\) is the heat required for heating the melt to the casting temperature, as follows:  
\[Q_{UH3}=m_{Al}\Big{(}c_{t,Al3}t_{3}-c_{t,Al3}t_{3}\Big{)}, \tag{16}\]  
where \(m_{Al}\) is the mass of aluminium ingots (kg), \(c_{tAl1}\) is the specific heat capacity of aluminium at ambient temperature (J.kg\({}^{-1}\) K\({}^{-1}\)), \(c_{tAl2}\) is the specific heat capacity of aluminium at melting temperature (J.kg\({}^{-1}\) K\({}^{-1}\)), \(c_{tAl3}\) is the specific heat capacity of aluminium at the temperature of 740 \({}^{\circ}\)C (J.kg\({}^{-1}\) K\({}^{-1}\)), \(t_{1}\) is the temperature of the aluminium charge (\({}^{\circ}\)C), \(t_{2}\) is the melting temperature of the aluminium charge (740 \({}^{\circ}\)C) (\({}^{\circ}\)C), \(l_{Al}\) is the latent heat (J.kg\({}^{-1}\)), \(\overline{t_{f}}\) is the average temperature in furnace (\({}^{\circ}\)C), and \(\overline{t_{b}}\) is the average temperature of the charge (\({}^{\circ}\)C). The evaluation of heat flow changes on the charge was performed by measuring the temperature field in the combustion chamber by the thermocouples. The overall heat transfer coefficient, \(\alpha_{o}\), in the furnace work area is characterized by the following equation [6]:  
\[\alpha_{o}=\alpha_{c}+\alpha_{r}, \tag{17}\]  
where \(\alpha_{c}\) is the heat transfer coefficient by convection (W m\({}^{-2}\) K\({}^{-1}\)) and \(\alpha_{r}\) is the heat transfer coefficient by radiation (W m\({}^{-2}\) K\({}^{-1}\)). The value \(\alpha_{r}\) is affected mainly by the fourth power of the thermodynamic temperature and by the flue gas emissivity, which depends on the flue gas composition. When increasing the oxidizer oxygen concentration, the concentrations of CO\({}_{2}\) and H\({}_{2}\)O in flue gas rise. These components have a significant effect on the increase of the flue gas emissivity. The results of mathematical calculations for the theoretical temperature, temperature with dissociation, and flue gas emissivity (Figure 4) illustrate that a proportion of the radiation component, \(\alpha_{r}\), increases with the increase of the oxidizer oxygen concentration (the increase in flue gas temperature and emissivity). The value \(\alpha_{c}\) is influenced by the amount and flow rate of flue gas in the work area. The increase of the oxidizer oxygen concentration results in the reduction of the flue gas amount. The rate and distribution of the flue gas flow in the work area and the way flue gas flows around the charge can be influenced by the burner geometry. At the constant diameter of the burner orifice, the proportion of the convection component, \(\alpha_{c}\), in the heat transfer process in the work area is reduced (the influence of the flue gas speed and the flame length vs. flue gas temperature) due to the reduction of the flue gas quantity.