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Influence of Flow Rate and Inlet Geometry on the Thermal Efficiency of a Water Flow CalorimeterAbstract: The main aim of the present work is to analyze the influence of water flow rate and inlet geometry on the arc thermal efficiency of a continuous water flow calorimeter. The experimental procedure consists of varying water flow rate and testing three different calorimeter inlet seal geometries: straight seal, conical diffuser seal and seal with water flux obstacle. The experiments were designed and the results evaluated based in a one-factor statistical analysis of variance, in this case the inlet calorimeter water flow. The welding beads were deposited on low carbon steel pipes by Gas Metal Arc Welding -GMAW process, using the same parameters and welding time. The highest average thermal efficiency is 80.5% to water flow of 4 l/min, with a low statistical error, using the conical diffuser seal inlet geometry, whereas for smaller or higher flow rates the measured efficiency values were lower. The inlet with straight seal model shown all the arc thermal efficiency values with slightly lower numerical values compared with conical diffuser, while the seal with flux obstacle exhibited high statistical error.
WAAM (Wire-Arc-Additive-Manufacturing) is an additive manufacturing process which uses arc welding to produce metal parts. This process is prone to heat accumulation, i.e. a progressive increase of the interlayer temperature and molten pool size, having detrimental consequences on the material properties and on the workpiece integrity. This paper investigates the effect of air jet impingement, an active cooling technique, to prevent heat accumulation, on the surfaces of WAAM workpieces. A reference test case was manufactured using traditional free convection cooling and air jet impingement. The workpiece temperature was measured using Ktype thermocouples. The manufactured surfaces were measured using a coordinate measuring machine and compared in terms of deposition efficiency, deposit height and average arithmetical deviation. The temperature results highlight that air jet impingement is effective in preventing the occurrence of heat accumulation. The surface data highlight that air jet impingement increase the deposited height and the surface waviness with a consequent decrease of the deposition efficiency.
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