A Simple Method of Reducing Coolant Leakage for Direct Metal Printed Injection Mold with Conformal Cooling Channels Using General Process Parameters and Heat Treatment

Direct metal printing is a promising technique for manufacturing injection molds with complex conformal cooling channels from maraging steel powder, which is widely applied in automotive or aerospace industries. However, two major disadvantages of direct metal printing are the narrow process window and length of time consumed. The fabrication of high-density injection molds is frequently applied to prevent coolant leakage during the cooling stage. In this study, we propose a simple method of reducing coolant leakage for a direct-metal-printed injection mold with conformal cooling channels by combining injection mold fabrication with general process parameters, as well as solution and aging treatment (SAT). This study comprehensively investigates the microstructural evolution of the injection mold after SAT using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. We found that the surface hardness of the injection mold was enhanced from HV 189 to HV 546 as the Ni-Mo precipitates increased from 12.8 to 18.5%. The size of the pores was reduced significantly due to iron oxide precipitates because the relative density of the injection mold increased from 99.18 to 99.72%. The total production time of the wax injection mold without coolant leakage during the cooling stage was only 62% that of the production time of the wax injection mold fabricated with high-density process parameters. A significant savings of up to 46% of the production cost of the injection mold was obtained.

Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

A system of borehole heat exchangers (BHEs) combined with pumping–injection wells is established in areas where the groundwater is shallow and the seepage velocity is weak. The pumping and injection wells are set on both sides of the BHEs. According to the three-dimensional unsteady-state heat transfer model in the aquifer, the convection–dispersion analytical solution of excess temperature is derived that considers groundwater-forced seepage and thermal dispersion effects and axial effect of the BHEs. Then, we use the dimensional analysis method and similarity criteria to build a controllable forced seepage sandbox. The software FEFLOW 7.1 is adopted and the simulation results are validated by the theoretical analysis and the indoor experiment test. On this basis, the numerical simulation is used to explore the influence of different pumping–injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, as well as the average heat transfer efficiency and the heat transfer rates with borehole depth. The results show that when the pumping flow volume increases from 200 m3 day−1 to 1200 m3 day−1, the Darcy velocity correspondingly increases to about 10 times. The average heat efficiency coefficient of the BHEs is increased by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping–injection flow volume is 400–600 m3 day−1, the increment of heat transfer rates of the BHEs reaches 12.8–17.9 W m−1 and 3.6–4.2 W m−1 per unit of borehole depth during the cooling stage and heating stage, respectively, and then decreases as the flow volume increases gradually.

Efficiency Analysis of SMA-Based Actuators: Possibilities of Configuration according to’ the Application

Shape memory alloy (SMA) actuators have recently demonstrated their potential for various applications in fields such as robotics, medicine, aerospace, and automotive. Its features, such as low weight and high force, simplicity, noiseless operation, and low cost compared with other conventional actuator, are only a few advantages of this actuator, which is receiving increasing interest among researchers. However, the use of these actuators is still limited by some of their characteristics: high position error in the cooling stage when the actuator works at frequencies that exceed the necessary cooling time and high electrical energy consumption. Different actuator configurations can help minimize these disadvantages through modifying the length, the number of cables, or the sheath used in the actuator, which modify the characteristics of the complete system. In this work, we developed different configurations of SMA actuators and tested their performance in terms of efficiency and the position error in the cooling stage. The findings demonstrate that over-dimensioned actuators are more energetically efficient and present a faster initial form recovery. The multi-wires actuator configuration produce a better response in terms of position but are less energy efficient. These conclusions allow for the selection of the most appropriate configuration based on the requirements of each particular application.

Viscosity of Liquid Nanocrystalline Alloys

Temperature dependences of the kinematic viscosity, density, and electrical resistivity of Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 multicomponent melts have been studied. We found different behavior of the temperature dependences of viscosity near the critical point Tk = 1760 K during heating, which is associated with different chemical compositions of the clusters in the melt. In the cooling stage, the activation energy of the viscous flow for these two melts is the same and equal to 43 kJ·mol-1. At a temperature of 1720 K, the relative free volume is 5.1 and 7.5 % of the total melt volume for Fe72.5Cu1Nb2Mo1.5Si14B9 and Fe84.5Cu0.6Nb0.5Si1.5B8.6P4C0.3 respectively. In the cooling stage, the electrical resistance of melt is higher than at the heating stage.

Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

A borehole heat exchangers (BHEs) combined with pumping-injection well is established in areas where the groundwater is shallow and the seepage velocity is weak. The pumping and injection wells are set on both sides of the BHEs. According to the three-dimensional unsteady heat transfer model in aquifer, the convection-dispersion analytical solution of excess temperature is derived that considers groundwater forced seepage and thermal dispersion effects and axial effect of the BHEs. Then, the dimensional analysis method and similarity criteria we used to build a controllable forced seepage sandbox. The software FEFLOW 7.1 is adopted and the simulation results are validated by the theoretical analysis and the indoor experiment test. On this basis, the numerical simulation calculation is used to explore the influence of different pumping-injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, the average heat transfer efficiency and the heat transfer rates with borehole depth. The results show that when the pumping flow volume increases from 200 m3∙d-1 to 1200 m3∙d-1, the Darcy velocity correspondingly increases to about 10 times. The average heat efficiency coefficient of the BHEs is increased by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping-injection flow volume is 400~600 m3∙d-1, the increment of heat transfer rates of the BHEs reaches 12.8~17.9 W∙m-1 and 3.6~4.2 W∙m-1 per unit of borehole depth during the cooling stage and heating stage respectively, and then decreases as the flow volume increases gradually.

Direct observation and assessment of phase states of ambient and lab-generated sub-micron particles upon humidification

We present a new analytical platform that uses a tilted and Peltier cooling stage interfaced with an environmental scanning electron microscope to directly observe and assess the phase state of individual particles as a function of relative humidity.

Evaluation of the effect of cooling on the microbiological quality of lamb carcasses

This study aimed to determine the effects of cooling on microbiological quality of lamb carcasses. Total Aerobic Bacteria Count (TABC), Enterobactericeae counts and the presence of Salmonella spp. were investigated in accordance with the Turkish Food Codex Regulation on Microbiological Criteria and European Union Commission Regulation 2073/2005. Sampling was carried out on aseptic conditions from the surface of 25 randomly selected lambs brought to slaughterhouse. The results showed that the mean TABC were 2.24±0.087 log cfu/cm2 before cooling and 2.41±0.061 log cfu/cm2 after cooling (P>0.05). The mean Enterobactericeae count was 0.21±0.11 log cfu/cm2 before cooling and 0.69±0.13 log cfu/cm2 after cooling (P<0.01). Furthermore, Salmonella spp. were determined on 3 carcasses before cooling and one another carcass after cooling. The influence of cooling on categorisation according to the legislations presented that it could potentially improve the numbers of acceptable carcasses for TABC and Salmonella spp. Nevertheless, the results exhibited that the hygiene and cooling stage of the slaughter line must be re-evaluated in terms of HACCP requirements and that corrective measures/actions must be taken.

Effect of groundwater forced seepage on heat transfer characteristics of borehole heat exchangers

A borehole heat exchangers (BHEs) combined with pumping-injection well is established in areas where groundwater is shallow but the seepage velocity is weak, which sets up pumping and injection wells on both sides of the BHEs. According to the three-dimensional unsteady state heat transfer model in aquifer, we derive the convection-dispersion analytical solution of excess temperature in aquifer that considers groundwater forced seepage and thermal dispersion effects in aquifer and the axial effect of the BHEs. Then, we use dimensional analysis method and similarity criteria to build a controllable forced seepage sandbox. The theoretical analysis is combined with the indoor experiment test to verify the correctness and accuracy of the numerical simulation software FEFLOW7.1. On this basis, we perform the numerical simulation calculation to explore the effects of different pumping-injection flow volume on the Darcy flow velocity of the aquifer where the BHEs are located, the average heat transfer efficiency and the heat transfer rates per unit borehole depth of the BHEs. The results show that when the pumping flow volume is increased from 200 m3∙d-1 to 1200 m3∙d-1, the Darcy velocity correspondingly increases to about 10 times the previous velocity. The average heat efficiency coefficient of the BHEs increases by 11.5% in cooling stage, and by 7.5% in heating stage. When the pumping-injection flow volume is 400~600 m3∙d-1, the increment of heat transfer rates per unit borehole depth of the BHEs reaches 12.8~17.9 W∙m-1 and 3.6~4.2 W∙m-1 during the cooling stage and heating stage respectively, and then decreases as the flow volume increases gradually.