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In this paper thermal modeling and optimal design of a heat exchanger for the fast axial flow (FAF) CO2 laser cooling system are presented. The log mean temperature difference (LMTD) method is applied to estimate the heat exchange performance. The tube diameter, tube pitch, tube length, number of tubes in face and depth, tube passes and fin numbers are considered as seven design parameters. Fast and elitist Non-dominated Sorting Genetic-Algorithm (NSGA-II) is applied to obtain the minimum heat exchange surface area and pressure drop as two objective functions. The results of optimal designs are a set of multiple optimum solutions, called "Pareto optimal solutions". [ABSTRACT FROM AUTHOR]

A six-temperature kinetic model for a CO2-N2-He system has been employed to describe the temporal behaviour of the output power, gain, gas temperature and the vibrational temperatures in a fast axial flow continuous wave (CW) CO2 laser. It takes into account the effects of energy transfer processes, thermal energy transport, and the dissociation of CO2 molecules. In addition, the effects of gas pressure, gas flow velocity, discharge current, discharge tube diameter and concentrations of N2, He and CO on the output power, gain, gas temperature and vibrational temperatures were studied. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical model based on the laser rate equations and the electrical circuit equations to describe pulsed CO2 laser characteristics. The dependence of laser output power and pulse shape on several parameters such as gas temperature, gas velocity, gas pressure, input power, gas pressures ratio, reflectivity of the output mirror, electrodes length and discharge gap have been investigated. This model can provide a theoretical basis for the design and analysis of TEA CO2 lasers. There was good agreement between the theoretical prediction and the experimental result. [ABSTRACT FROM AUTHOR]

The aim of this paper is the thermal analysis of the fast axial flow (FAF) CO2 laser and proposition of a complete algorithm of the heat exchanger design for this type of laser. Selection of an appropriate heat exchanger for the FAF CO2 laser, while enhancing heat exchange performance, causes less pressure drop and flow reduction. Based on the design of an industrial 1000W CO2 laser various types of heat exchangers were compared with each other and plane-finned tube heat exchanger was found to be the appropriate cooling system for the FAF CO2 laser. Finally, a compact plane-tube fined type heat exchanger, with full geometric profile and arrangement of the pipes was designed and manufactured. Moreover, the flow velocity field of the gas mixture at separator plates within the heat exchanger has been simulated and optimized using finite element method. The results show that the optimum height of separator plates is 34cm to achieve maximum output flow velocity. [ABSTRACT FROM AUTHOR]