Phase Transformation of M2 High Speed Steel during Semi-Solid Cooling and Conventional Cooling

In this paper, the fundamental microstructure evolution of M2 high speed steel was investigated during semi-solid controlled cooling and conventional cooling, respectively. Semi-solid controlled cooling was conducted at 1260 °C with cooling rates from 0.1 to 10 °C/s, while conventional cooling was conducted at 1200 °C and 890 °C with different cooling rates. The continuous cooling transformation curves were plot according to the microstructure evolution. The results showed that microstructure transformation behavior of cooling structure in semi-solid temperature range was different from that of conventional process. For semi-solid specimen, the solid austenite dissolved more alloy elements, and the austenite stability was increased. The solid matrix was pearlite structure in the samples with cooling rate of 0.1 °C /s. When the cooling rate reached 1 °C/s, the granular pearlite disappeared and martensite lath was formed. The structure was relatively uniform, on which there were large carbide with regular shape. The solidified liquid phase showed a network shape surrounding the solid particles. The size of solid particles showed a decreasing trend with the increase of cooling rates. For conventional cooling process, the large eutectic M6C carbide and the small precipitated MC carbide could not be dissolved by austenitized at 890 °C. Increasing the austenitization temperature helped dissolving part of the carbides. The hardenability of M2 steel was high. The hardness has increased to a high level for both semi-solid and conventional specimens when cooling rate reached 1 °C/s. No obvious increase happened when cooling rate continued increasing.

Adaptive Conformal Cooling of Injection Molds Using Additively Manufactured TPMS Structures

In injection molding, cooling channels are usually manufactured with a straight shape, and thus have low cooling efficiency for a curved mold. Recently, additive manufacturing (AM) was used to fabricate conformal cooling channels that could maintain a consistent distance from the curved surface of the mold. Because this conformal cooling channel was designed to obtain a uniform temperature on the mold surface, it could not efficiently cool locally heated regions (hot spots). This study developed an adaptive conformal cooling method that supports localized-yet-uniform cooling for the heated region by employing micro-cellular cooling structures instead of the typical cooling channels. An injection molding simulation was conducted to predict the locally heated region, and a mold core was designed to include a triply periodic minimal surface (TPMS) structure near the heated region. Two biomimetic TPMS structures, Schwarz-diamond and gyroid structures, were designed and fabricated using a digital light processing (DLP)-type polymer AM process. Various design parameters of the TPMS structures, the TPMS shapes and base coordinates, were investigated in terms of the conformal cooling performance. The mold core with the best TPMS design was fabricated using a powder-bed fusion (PBF)-type metal AM process, and injection molding experiments were conducted using the additively manufactured mold core. The developed mold with TPMS cooling achieved a 15 s cooling time to satisfy the dimensional tolerance, which corresponds to a 40% reduction in comparison with that of the conventional cooling (25 s).

Review on Performance Enhancement of Photovoltaic/Thermal–Thermoelectric Generator Systems with Nanofluid Cooling

Photovoltaics (PVs) are an effective technology to harvest the solar energy and satisfy the increasing global electricity demand. The effectiveness and life span of PVs could be enhanced by enabling effective thermal management. The conversion efficiency and surface temperature of PVs have an inverse relationship, and hence the cooling of PVs as an emerging body of work needs to have attention paid to it. The integration of a thermoelectric generator (TEG) to PVs is one of the widely applied thermal management techniques to improve the performance of PVs as well as combined systems. The TEG utilizes the waste heat of PVs and generate the additional electric power output. The nanofluid enables superior thermal properties compared to that of conventional cooling fluids, and therefore the performance of photovoltaic/thermal–thermoelectric generator (PV/T-TEG) systems with nanofluid cooling is further enhanced compared to that of conventional cooling. The TEG enables a symmetrical temperature difference with a hot side due to the heat from PVs, and a cold side due to the nanofluid cooling. Therefore, the symmetrical thermal management system, by integrating the PV/T, TEG, and nanofluid cooling, has been widely adopted in recent times. The present review comprehensively summarizes various experimental, numerical, and theoretical research works conducted on PV/T-TEG systems with nanofluid cooling. The research studies on PV/T-TEG systems with nanofluid cooling were reviewed, focusing on the time span of 2015–2021. This review elaborates the various approaches and advancement in techniques adopted to enhance the performance of PV/T-TEG systems with nanofluid cooling. The application of TEG with nanofluid cooling in the thermal management of PVs is an emerging research area; therefore, this comprehensive review can be considered as a reference for future development and innovations.

Experimental investigation of desiccant dehumidification based thermoelectric air-conditioning system

Vapor compression refrigeration system (VCRS) based conventional cooling systems run on the high amount of electricity and refrigerants responsible for greenhouse emissions. To save the environment and high-grade energy, traditional cooling systems should be replaced with some environment-friendly alternative. This paper proposed alternative eco-friendly air-conditioning systems based on an amalgam of two different technologies, i.e., desiccant dehumidification and thermoelectric (TE) cooling. The proposed air-conditioning system has the following subprocess: dehumidification of moist air by the solid desiccant wheel, cooling of processed air by TE modules, and regeneration of desiccant wheel by an electric heater and waste heat from TE modules. The air conditioning system has been experimentally studied for cooling performance, cooling effect, and energy input. The maximum coefficient of performance of 0.865 can be achieved with the proposed system, and it can be used for cooling effects up to 1442.24 W to maintain the human comfort condition in the chamber i.e. approximately 22 ℃ and RH 50% defined by ASHRAE.

EVALUATION OF THE RADIANT COOLING CEILING PANELS WITH A REVERSIBLE HEAT PUMP

Thermal comfort is one of the basic prerequisites for appropriate operating of the building. Ensuring thermal comfort in the summer means creating suitable thermal conditions in the interior. The present article evaluates the operation of radiant ceiling cooling, which is a suitable alternative for conventional cooling systems. Experimental cooling systems using a reversible heat pump as a source of chilled water were analyzed. The presented results indicate the ability of the system to ensure the required interior temperature under suitable climatic conditions using appropriate time management and sufficient accumulation. The required temperature is 24.51 °C and the deviation does not exceed ± 0.5K.

Effect of a Geothermal Heat Pump in Cooling Mode on the Housing Environment and Swine Productivity Traits

This study compared the effects of the cooling mode of a geothermal heat pump (GHP) system with those of a traditional cooling system (ventilation fans) inside a pig house on the internal house temperature, harmful gas emissions, and the growth performance of the pigs. During the 19-week experimental period, the temperature inside the house connected to the GHP cooling system was significantly lower (p < 0.05) than that of a house with a conventional cooling system. Similarly, the temperature–humidity index (THI) was significantly reduced (p < 0.05) in the GHP cooling system-connected pig house. Furthermore, the concentrations of ammonia (NH3) and hydrogen sulfide (H2S) were also decreased significantly in the GHP-installed pig house (p < 0.05). However, no differences were observed in the concentrations of particulate matter (PM2.5) and formaldehyde (p > 0.05). The pigs reared in the GHP-equipped pig house gained significantly more weight (p < 0.05) by the end of the experiment. The GHP cooling system can therefore be implemented as a renewable, environmentally friendly energy source in pig farms for sustainable swine production without adversely affecting the productivity parameters.

The effects of vacuum cooling to post-pasteurized honey on diastase enzyme activity and physical properties of Riau Forest Honey

Honey is defined as a traditional natural liquid which usually has a sweet taste derived from the nectar of flowers. The main component of honey is a natural saturated sugar solution consisting of a mixture of complex carbohydrates and contains various important micro-nutrients such as vitamins, minerals, enzymes, and organic compounds. These micro-nutrients are very susceptible to damage during the honey processing process. In this study, a cooling method in the form of vacuum cooling was applied with the aim of maintaining the micro-nutrients in honey. Vacuum cooling that is applied after the pasteurization process aims to release the latent heat trapped in the honey in a relatively short time and minimize damage to micronutrient, especially the diastase enzyme. The research design consisted of 2 factors, namely the volume chamber consisting of 12.5%, 25%, and 50%. The second factor is the cooling method which consists of conventional and vacuum cooling. The samples from the research were tested on diastase enzyme activity and the physical properties of honey such as moisture content, density, and acidity. The results showed that cooling with the vacuum cooling method had lower water content, low acidity, high density, and better diastase enzyme activity compared to conventional cooling.

Design, Optimization and Validation of Conformal Cooling Technique for Additively Manufactured Mold Insert

Injection molding is a cyclic process comprising of cooling phase as the largest part of this cycle. Providing efficient cooling in lesser cycle times is of significant importance in the molding industry. Conformal cooling is a proven technique for reduction in cycle times for injection molding. In this study, we have replaced a conventional cooling circuit with an optimized conformal cooling circuit in an injection molding tool (mold). The required heat transfer rate, coolant flow rate and diameter of channel was analytically calculated. Hybrid Laser powder bed fusion technique was used to manufacture this mold tool with conformal channels. The material used for manufacturing mold was maraging steel (M300). Thermal efficiency of the conformal channels was experimentally calculated using thermal imaging. Autodesk MoldFlow software was used to simulate and predict the cooling time required using conformal cooling channels. The results showed a decrease in cooling time and increase in cooling efficiency with the help of conformal cooling in additively manufactured mold insert.

Novel Air-Cooled Thermosyphon Cooling System for Desktop Computers

The trade-off between efficient cooling and low power consumption is a goal that has always been very desirable in electronics cooling, especially nowadays that power densities of processing units are increasing. Conventional cooling solutions do not have the necessary cooling capacities for these power densities or require significant power consumption. In this study, a novel air-cooled thermosyphon cooling system for desktop computers is presented and experimentally tested. The thermosyphon comprises a vertical micro-channel cold plate as the evaporator and a horizontal air-cooled multiport coil as the condenser. The thermosyphon has a total height of 12 cm and operates with a fan speed of 1700 RPM. The working fluid selected for the thermosyphon loop is R1234ze(E), chosen for its advantageous thermophysical properties and nearly zero-GWP (Global Warming Potential). The test results presented in this paper aim to analyze thermosyphon’s thermal and hydraulic performance by studying the trends of thermal resistance and mass flow rate as a function of different operating conditions. The maximum heat rejection under safe conditions is 250 W, corresponding to a heat flux of about 18 W/cm2.

Three-Dimensional Transient Finite Element Cooling Simulation For Injection Molding Tools

Plastic injection molding is one of the most popular manufacturing processes for mass production, and optimizing the mold cooling system is critical for reducing the cycle time and improving the final part quality. Conventional cooling simulation uses the boundary element method to perform the cycle-averaged analysis, which is a simplification due to computational resources limitation. This paper develops a three-dimensional transient cooling simulation method based on the finite element method, which can simulate the complex mold system accurately and efficiently. It is shown that this method finishes the transient cooling analysis in 478 seconds on the real-world injection molding mold with more than 6.9 million tetrahedral elements. Its accuracy is compared against the experimental results with the maximum temperature error less than 4%, and the average temperature error less than 1%.