Key Engineering Materials Vol. 1062

Abstract: Internal shrinkage defects often occur in sand-cast gray cast iron pump casings, particularly in areas with abrupt thickness variations where heat dissipation is limited. These defects form during the final stage of solidification when isolated liquid metal cannot be properly fed. In this study, the solidification behavior of an industrial pump casing is investigated through coupled thermal–flow simulation to analyze temperature gradients and feeding paths. The results show that delayed solidification at the flange–root junction leads to isolated liquid zones that develop into shrinkage cavities. By modifying the feeding layout, heat extraction and directional solidification toward the riser are improved. Experimental casting with the optimized design shows no visible shrinkage defects and achieves an average hardness of 42.3 HRA. These findings highlight the importance of maintaining solidification continuity to eliminate defects in gray cast iron pump casings [1].

Abstract: This study presents the comprehensive design and fabrication of a bespoke laboratory-scale Rotary Friction Welding (RFW) machine, developed by repurposing a J23 mechanical press frame to provide a cost-effective research platform. The system integrates a 7.5 kW motor with VFD control for precise rotational speeds up to 1500 RPM and a two-stage hydraulic circuit to manage friction and forging pressures. To validate the machine's efficacy, twenty experimental runs were conducted on similar-material joints, specifically AISI 304 stainless steel, AA1050 aluminum, and AISI 1030 structural steel. Mechanical testing and microstructural analysis demonstrated that the system consistently produces high-integrity bonds, with AISI 1030 steel joints achieving 100% joint efficiency and AISI 304 samples reaching ultimate tensile strengths exceeding 800 MPa. The results confirm that the reoriented horizontal frame maintains the necessary axial alignment for high-quality solid-state joining, making it a reliable and accessible tool for academic investigation into RFW process optimization.

Abstract: In open-surface evaporation systems, the simultaneous transfer of heat and mass is vital for establishing the interrelated exchange of energy and mass between liquid and gas phases. This research offers a comprehensive examination of the physical mechanisms that control evaporation in both natural and forced convection scenarios. It also assesses different theoretical and empirical approaches for calculating the heat transfer coefficient. It has been shown through experiments and numerical analyses conducted in the past that the precision of predictions regarding heat and mass transfer is greatly influenced by factors such as geometrical configurations, convection regimes, and measurement accuracy. Various analytical methods are examined, such as the heat balance equation method that connects heat flux to temperature difference and evaporation rate through interfacial energy balance, and the dimensional analysis method that formulates general correlations based on important dimensionless numbers like Nusselt, Prandtl, Reynolds, and Rayleigh. Moreover, the heat–mass transfer analogy offers a practical framework for estimating one coefficient based on the other by taking advantage of the similarity between temperature and concentration fields. Furthermore, the Ackermann correction factor is implemented to consider the effect of vapor flow on the heat transfer, thereby improving estimations of the heat transfer coefficient during evaporation and diffusion. This research creates an extensive framework for the analysis of open-surface evaporation and the enhancement of heat and mass transfer coefficient predictions. This is achieved through a combination of theoretical, experimental, and analogy-based methods, leading to improvements in the design and functioning of thermal and evaporative systems.

Abstract: Industrial pipe insulation is almost always selected from discrete catalog steps of material, thickness, and jacket/cladding, yet a large share of the literature optimizes a continuous thickness. This paper develops a directly implementable, catalog-based method that outputs the globally optimal insulation choice for each operating temperature and summarizes it as temperature bands with explicit transition points. The approach combines a physically transparent heat-loss model with a simple, robust optimization over the finite decision set.

Abstract: Environmental regulations, fluctuating energy prices, and uncertainties in the international energy markets motivate consumers to ensure their security of energy supply. One method to achieve this goal is to use heat storage equipment, which is scalable and applicable in both industrial and residential environments. The present study focuses on latent heat energy storage utilizing paraffin as a phase-changing material. A cube-shaped heat storage test device was investigated both experimentally and numerically. We used the obtained experimental data to validate our effective numerical modeling approach based on the enthalpy method. We proposed an effective numerical approach to take into account the material nonlinearities and the effect of convective flow phenomena on heat transfer processes, while neglecting the exact flow field and spatial distributions.