Search

The higher the linear speed of the gear is, the more significant the friction heat generation phenomenon will be, which is not conducive to the improvement of gear life and efficiency. Thus, it is necessary to conduct an analysis of the oil injection cooling characteristics of the gear pair under the high pitch line velocity and explore optimal cooling parameters. Based on the Hertz contact theory and gear meshing characteristics, the average contact stress, relative sliding velocity, and friction coefficient of the tooth surface were solved. Based on the heat generation theory, the average heat flux density of the tooth surface at the high pitch line velocity was obtained. Furthermore, the heat flux density of the tooth surface was used as a boundary condition, and a simulation model for the oil injection cooling characteristics of high speed gears with a pitch line velocity of 120 m/s was established. The effects of the injection speed, injection angle, and gear baffle configuration on the cooling characteristics were explored. The results show that increasing the injection speed can improve the cooling effect of the tooth surface to a certain extent. When the injection angle is 60° and the axial injection angle is 20° higher, a lower tooth surface temperature can be obtained. The axial baffle configuration has a better cooling effect on the tooth surface compared to other baffle configurations.

The mechanism of curving that occurs during the quenching process of Japanese swords has not been clearly explained. Experiments on this phenomenon were conducted using Japanese sword type specimens made of the same steel and processes as Japanese swords, and model Japanese sword type specimens made of carbon steel (S55C) and austenitic stainless steel (SUS304) by machining. Applying the simulated strains-based approach to heat treatment simulation results for these experiments found that positive plastic strain and transformation strain on the cutting-edge side are main contributors to curving generation in Japanese sword. [ABSTRACT FROM AUTHOR]

AbstractThe uniformity of cooling affects the organizational properties and product quality of the L-beam. Problems such as bending deformation of the L-beam and excessive residual stresses inside the finished product are mainly caused by uneven cooling. The jet angle is an important cooling parameter in the cooling process of L-beam. In this study, the flow field and cooling law during jet cooling of hot-rolled L-beams were investigated by means of numerical simulation using the jet angle as a variable. The jet angle is −45°∼30° on the lower surface of the short edge of the L-beam due to space limitation, and the jet angle is −45°∼45° on the rest of the parts, and the other process parameters are kept unchanged. The velocity distribution, pressure, water flow, and temperature distribution on the cooling surface and the average heat transfer coefficient were analyzed. The results show that the jet angle has a significant effect on the cooling of each part of the L-beam. With the increase of the jet angle, the asymmetry of water velocity, pressure distribution, water flow distribution, and temperature distribution on the surface of the cooling surface increased significantly. The distribution of heat flux corresponds well to the distribution of temperature. As the jet angle increases the surface average heat transfer coefficient gradually decreases, and the maximum average heat transfer coefficient appears in the vertical jet. Gravity will also have a certain effect on the cooling of the L-beam. [ABSTRACT FROM AUTHOR]

Abstract Aiming at the thermal safety and inconsistency caused by the high temperature of lithium‐ion (Li‐ion) battery, a cooling structure embedded with a flat aluminum heat pipe (FAHP) for a Li‐ion battery module is proposed. The three‐dimensional thermal model of the FAHP module is established by considering regionalized thermal radiation. The thermal characteristics of the module are compared with four progressive cooling schemes, and the temperature performance affected by different convection (hconv) and radiation (hrad) heat transfer coefficients are analyzed. Results show that, the thermal model with the thermal radiation is more precise than that without the thermal radiation under the natural convection. Adding FAHPs can effectively reduce the maximum temperature (Tmax) and the maximum temperature difference (ΔTmax,pack) of the FAHP module. Especially adding FAHPs with fins, even at 3C discharging, the average cooling performance can be improved by 33.3%, 25.0%, and 14.4% than that of natural convection, aluminum plates sandwiched between cells and FAHPs with no fins, respectively. Meanwhile, the decrease in rates of Tmax and ΔTmax,pack are gradually increasing with the increasing of hrad, but decreased with the increasing of hconv. When 5 W·m−2·K−1 ≤ hconv ≤ 35 W·m−2·K−1, the average ratio of radiation heat dissipation to total heat dissipation (η) is 35.7%, but when hconv > 55 W·m−2·K−1, η is less than 1.5%.

The degradation of permafrost caused by climate change and engineering disturbance significantly affects infrastructure stability and transportation safety. Two-phase closed thermosyphons (TPCTs) were widely used to tackle external disturbances by cooling the permafrost stratum in permafrost engineering. However, existing research mainly focuses on the thermal performance of TPCTs. To evaluate the spatiotemporal thermal-deformation characteristics of a composite embankment with L-shaped two-phase closed themosyphons (LTPCTs) on a permafrost slope, we built the first spatiotemporal thermal-deformation observation system for a permafrost embankment with LTPCTs and insulation along the Gonghe-Yushu Highway in the Qinghai-Tibet Plateau, as well as a contrast embankment only with insulation (as a control). The observation results during the first five-year service period indicate that: (1) The cooling performance of LTPCT is determined by the air temperature, and the exterior wall temperature at the top of the evaporator section is significantly affected by the surface ground; additionally, its maximum effective cooling scope is no more than 2.0 m; (2) The LTPCTs can effectively cool down the underlying permafrost in the middle of the composite embankment, and reduce the settlement of the centerline after the second service year; (3) The deformation in the middle of the composite embankment is mainly from the layer of −3.5 to −6.0 m under the bottom of the asphalt layer in the first three years; (4) The maximum settlement near the long sunny slope of the composite embankment can reach 4 times of that at the centerline, and the continuously increasing deformation difference along the cross section may cause longitudinal cracks of the embankment, and influence the traffic safety. Therefore, it is believed that the research results can promote acknowledge for the composite embankments with LTPCTs used in a permafrost slope. [ABSTRACT FROM AUTHOR]

Aiming at the thermal safety and inconsistency caused by the high temperature of lithium‐ion (Li‐ion) battery, a cooling structure embedded with a flat aluminum heat pipe (FAHP) for a Li‐ion battery module is proposed. The three‐dimensional thermal model of the FAHP module is established by considering regionalized thermal radiation. The thermal characteristics of the module are compared with four progressive cooling schemes, and the temperature performance affected by different convection (hconv) and radiation (hrad) heat transfer coefficients are analyzed. Results show that, the thermal model with the thermal radiation is more precise than that without the thermal radiation under the natural convection. Adding FAHPs can effectively reduce the maximum temperature (Tmax) and the maximum temperature difference (ΔTmax,pack) of the FAHP module. Especially adding FAHPs with fins, even at 3C discharging, the average cooling performance can be improved by 33.3%, 25.0%, and 14.4% than that of natural convection, aluminum plates sandwiched between cells and FAHPs with no fins, respectively. Meanwhile, the decrease in rates of Tmax and ΔTmax,pack are gradually increasing with the increasing of hrad, but decreased with the increasing of hconv. When 5 W·m−2·K−1 ≤ hconv ≤ 35 W·m−2·K−1, the average ratio of radiation heat dissipation to total heat dissipation (η) is 35.7%, but when hconv > 55 W·m−2·K−1, η is less than 1.5%. [ABSTRACT FROM AUTHOR]

ObjectivesAiming at the problems of the long response time and excessive time consumption of infrared cooling equipment, an optimization study is carried out.MethodsA special cooling method based on the combined effects of absorption, scattering of water mist particles and cooling of water film is proposed to attenuate the infrared radiation intensity of the target object and improve the response speed of the infrared cooling system. The infrared cooling characteristics of the composite nozzle and water film nozzle at different pressures are analyzed through comparative design experiments.ResultsThe test results show that under water supply pressures of 0.3, 0.5 and 0.8 MPa, the infrared cooling time of the composite nozzle is reduced by 27.9%, 47.3% and 46.2% respectively compared with that of the water film nozzle. At the moment the water mist is sprayed, the temperatures measured by the infrared thermal imaging camera are 8.62, 11.13 and 11.09 ℃ lower than the actual temperature of the target.ConclusionsThe test results show that the swirling atomizer composite nozzle can effectively control the infrared cooling time of the target object.

In order to study the improvement effect of new air distribution on the thermal environment of high heat dissipation industrial production workshop, taking a battery material production workshop as a case, the ventilation and cooling characteristics of four air distribution forms for industrial buildings were compared, including mixing ventilation, displacement ventilation, and two new air distribution forms: stratum ventilation and impinging jet ventilation. Using computational fluid dynamics (CFD) method, the workshop airflow was simulated under the same air supply conditions. The results indicate that the mixed ventilation forms the working area temperature up to 39. 1 ℃, while the stratum ventilation, impinging jet ventilation and displacement ventilation reduce the temperature in the working area to 33. 5, 32. 8, 31. 4 ℃ respectively. According to the above cooling characteristics of air distribution, a horizontal thermal stratification thermal environment control method was proposed. Combined with this method, the parameters of air supply speed and air supply volume were studied. It is found that reducing the air supply speed can promote the horizontal stratification of the workshop temperature, so as to reduce the working area temperature without increasing the air supply energy consumption. In addition, there is a critical value of air supply volume of the workshop, below which increasing air supply volume can significantly reduce the workspace temperature, but above which increasing air supply volume can􀆳t significantly improve the cooling effect. The results can be helpful in the ventilation design of industrial buildings. [ABSTRACT FROM AUTHOR]

Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Fire Safety Science is the property of Fire Safety Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The cold storage with secondary condensation and defrosting function was used to study the cooling characteristics of litchi under different cold storage pre-cooling processes, and the heat transfer model of litchi pre-cooling process was established. The results showed that compared with other defrosting methods, the temperature fluctuation of cold storage with secondary condensation defrosting function was significantly reduced. Under the same conditions, the cooling rates of different litchi varieties were Guiwei, Huaizhi and Nuomici respectively from the largest to the smallest. The lower the temperature of pre-refrigerated storage, the faster the litchi would cool down, but the average temperature of litchi should be avoided to below 5°C to prevent cold damage. When other precooling conditions were the same, the higher the wind speed, the faster the litchi would cool down. The inhomo-geneity of litchi pre-cooled in cold storage was greater at 0 °C than 2°C. By calibrating the convective heat transfer coefficient of litchi, the pre-cooling and cooling processes of single litchi were predicted, and the feasibility of the model was verified by the experimental results. [ABSTRACT FROM AUTHOR]

Through numerical simulation and experimental verification, the flow and heat transfer characteristics of different discontinuous bionic S-shaped ribs in cooling channels were studied. The influence mechanism of different discontinuous locations, discontinuous sizes, and discontinuous numbers coupling design on the channel performance is investigated in depth. The study demonstrates that the discontinuous design can significantly enhance flow field disturbance in the discontinuous region of the S-shaped rib, thereby substantially improving channel heat transfer. Channel heat transfer changes with the discontinuity location, exhibiting a trend similar to the cosine function. The channel heat transfer has different trends with the change of the discontinuity size under different discontinuity locations. Obtained by coupling the discontinuous size of 2 P /10 with the discontinuous location of 6 P /10 single discontinuous S-shaped rib heat transfer is the best, and the ribbed wall Nu/Nu 0 is approximately 35 % higher than the continuous rib. The greatest thermal performance, which is 39 % higher than continuous ribs, is achieved by single discontinuous S-shaped ribs with discontinuous size and discontinuous location of 5 P /10 and 9 P /10, respectively. The decreased distance between discontinuities in double discontinuous S-shaped ribs leads to the flow field disturbance coupling effects of adjacent discontinuities, which further enhances the disturbance and improves heat transfer. • Flow characteristics and heat transfer of the discontinuity S-shape rib under different geometric parameters were studied. • The channel heat transfer changes with discontinuity location, showing a similar trend to the cosine function. • The distributions of channel heat transfer with the discontinuity size differs under different discontinuity positions. • Double discontinuous design could further enhance channel heat transfer and heat transfer uniformity. [ABSTRACT FROM AUTHOR]

The characteristics of flow field distribution and temperature variation of an inclined jet impinging on a steel tube surface at different positions in circumferential directions were studied via numerical simulation. By analyzing the local convective heat transfer coefficient in circumferential direction, it was shown that the downstream and upstream regions had the characteristics of typical asymmetry. As the inclination angle increases, the local convective heat transfer coefficient gradually increases in the downstream region and gradually decreases in the upstream region. When the θ of the top and bottom jet is 30°, the increases in the downstream region are 40.2% and 54.6%, respectively. Based on the study of the local convective heat transfer coefficient and temperature distribution in the circumfluence direction of a steel tube during the cooling process, it was shown that the optimal inclination angle is 0~10°. With the increase in inclination angle, the average heat transfer coefficient shows a decreasing trend overall. With the increase in jet Reynolds number, the decrease in the average heat transfer coefficient gradually decreases. When the inclination angle increases to 30°, the effect of inclination angle on steel tube cooling is obviously stronger than that of jet position. [ABSTRACT FROM AUTHOR]

Pin-fins play a very important role in heat-transfer enhancement in engine combustor liners. In this engineering-scale experimental study, the flow and cooling characteristics of two- and three-layer porous laminates with pin-fins were compared. The influence of the diameter and height of the pin-fin on the flow and cooling characteristics of three-layer porous laminates was also investigated. Adding a third (impingement) layer to the two-layer porous laminate in the study increased the heat-transfer coefficient by 66.00% and the cooling efficiency by 5.90%; both performance factors were further improved as the pin-fin diameter and height in the three-layer laminate were reduced. An empirical expression for the Nusselt number of a three-layer porous laminate was obtained, with a prediction error below 5%. [ABSTRACT FROM AUTHOR]

• Effects of plate structure and channel on temperature distributions are assessed. • Applying sidewall cooling decreases the battery pack's average temperature by 4.48 ℃. • The temperature difference is within 3.84 ℃ with serpentine/parallel flow channels at 3C discharge rate. • The safe operating ranges of the battery pack are determined. Refrigerant direct cooling is currently being considered as an efficient thermal management technology in power battery systems. In this paper, four types of liquid cooling plates for power battery modules are designed and the computational model is constructed. With the model being validated, it is applied to analyze the effects of the cooling plate structure and cooling channel on the cooling and heat dissipation performances. The results reveal that for the conventional cooling method, i.e., when the cooling plate is placed on the bottom of the battery pack, a significant temperature gradient in the vertical direction is observed. On the contrary, adopting a serpentine cooling plate structure in the main wall or parallel cooling channels in the narrow side wall could significantly reduce the temperature difference of the battery pack, which can keep the temperature difference within 5 °C even under extreme conditions. Further, a detailed analysis of the heat dissipation performance based on the optimal cooling plate structure is performed to determine the safe operating range of the battery pack. It is shown that as the humidity is less than 0.73 and the evaporation temperature is below 15.43 °C, the battery pack can operate safely. However, beyond this condition range the heat dissipation characteristics of the battery pack cannot satisfy the operating requirements. This work sheds light upon the potential of refrigerant direct cooling strategy in power battery thermal management systems by properly arranging the cooling plate. [ABSTRACT FROM AUTHOR]

The industrial importance of steel is reflected in the wear resistance, which is related to its changes of microstructure and temperature changes during heat treatment. Herein, C−Si−Mn−Cr steels are produced to understand the microstructure evolution and cooling characteristics during quenching in water and air. The samples of several feature points are selected along the radial direction from the treated steel, and the temperature distribution of steel is obtained via numerical simulations. The microstructures at different temperature feature points and the corresponding hardness are studied. The results show that the quenching processes with the water−air alternating cycle regulate the temperature distribution. Martensite and pearlite phases are primarily formed during water and air cooling, respectively. In the water−air alternating cycle quenching process, the microstructure includes bainite, martensite, and retained austenite. The obtained microstructure is more ideal and the value of hardness is 525.2 HV. The maximum hardness value is 695.3 HV for water quenching, while that for air cooling is 248.2 HV. The microstructure evolution of steel at different positions is closely related to the temperature change in varied quenching processes. [ABSTRACT FROM AUTHOR]

The characteristics of flow field distribution and temperature variation of an inclined jet impinging on a steel tube surface at different positions in circumferential directions were studied via numerical simulation. By analyzing the local convective heat transfer coefficient in circumferential direction, it was shown that the downstream and upstream regions had the characteristics of typical asymmetry. As the inclination angle increases, the local convective heat transfer coefficient gradually increases in the downstream region and gradually decreases in the upstream region. When the θ of the top and bottom jet is 30°, the increases in the downstream region are 40.2% and 54.6%, respectively. Based on the study of the local convective heat transfer coefficient and temperature distribution in the circumfluence direction of a steel tube during the cooling process, it was shown that the optimal inclination angle is 0~10°. With the increase in inclination angle, the average heat transfer coefficient shows a decreasing trend overall. With the increase in jet Reynolds number, the decrease in the average heat transfer coefficient gradually decreases. When the inclination angle increases to 30°, the effect of inclination angle on steel tube cooling is obviously stronger than that of jet position.

Building thin-walled titanium alloy skin using conventional laser beam welding (LBW) frequently suffers from undesirable seam quality due to the V-shaped notch; a typical assembly error occurs after skin rolling with a specific sheet thickness range. This work proposed an improved scheme with metal bridging capacity and liquid film stability to overcome this by executing a pulsed laser beam and spot irradiation in a flat-top mode. Welding was performed on 1.5 mm-thick Ti6Al4V sheets configured in the butt joint with a reserved notch geometry, which is 20 degrees between the groove surface. We also conducted numerical modeling and solutions concerning the heat-flow-phase dynamics using an enhanced ray tracing algorithm. Results show that the as-build weld beads, characterized by middle rippers, slight depression, and edge ridges, present superb continuity and uniformity when applying an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. Effective metal bridging across the notch error is achieved at both pulse duration and interval phases due to not only the complete melting of welding side but also the enhanced melt film stability against the surface tension. The cooling of the weld pool starts with a sharp temperature drop at ∼3×105 K/s (on average) during the keyhole collapsing regime, then slows down due to the damped up-down oscillation of the free surface combined with the natural convection-conduction effect. The flow pattern of molten metal changes from squeezing-like to vortexes and finally to a backfilling mode, depending on the evolution of keyhole geometry. Although the keyhole dynamics differs, various process conditions regarding heat input and pulse energy yield effective metal bridging of a single weld spot and sufficient refusion between the adjacent weld spots, ensuring the well-overlapped weld bead formation. [Display omitted] • PLBW Tailored PLBW with top-hat beam spot were performed on Ti6Al4V skin sheets configured in butt joint with a V-shaped notch geometry. • As-build beads present superb appearance with an average heat input of 40–90 J/mm and a pulse energy of 187.5–750 J. • Metal bridging across notch is initially achieved at root surface and is further enhanced as keyhole advances and grows. • Keyhole collapse promotes melt convection between cold pool edge and hot keyhole tip leading to a sharp cooling stage. • Melt can be squeezed, vortical, or in a backfilling pattern during a typical pulse cycle depending on keyhole regime. [ABSTRACT FROM AUTHOR]

Summary: The batteries have been continuously for obtaining the high voltage platform and high density of energy with long lifecycle. The operating temperature of the battery cell has a significant effect on the thermal performance. This paper aims to consider the 18 650‐type lithium‐ion battery pack's thermal characteristics with the thermoelectric module using ferrofluid as a coolant. The experiment apparatus is test to determine the lithium‐ion battery pack's temperature distributions. Effects of the relevant parameters; hot and cold side flow rates (0.03‐0.05 m3/hr), supplied voltage through thermoelectric (8‐12 V), coolant types (De‐ionized water and ferrofluid), and ferrofluid concentrations (0.005%‐0.015% by volume) on the battery pack's cooling performance are considered. It is found that the thermoelectric cooling system significantly affects the battery pack cooling and gives the temperature of battery below 30°C. Higher cold and hot side flow rates can decrease average battery cell temperature by 3°C to 5°C, and the obtained uniformity temperature is below 3°C. Besides, ferrofluid concentration significantly reduces the average battery cell temperature when compared with deionized water. The proposed cooling system demonstrates the advantage of the electrical vehicle battery pack with the thermal cooling system. However, the optimized battery thermal management system still performs much better than the original one for various coolant flow rates and for the situation of heat generation rate. [ABSTRACT FROM AUTHOR]

To establish an efficient and clean cooling tower, a mechanical draft wet cooling tower (MDWCT) with the condensation plume module is studied. A 3D mathematical model is conducted, the width of the channel within the module is the main research variable, while the outlet water temperature, water saving rate, and plume are the main outputs. Three types of outputs are optimized by the NSGA-II multi-objective optimization algorithms, and the entropy weight TOPSIS method is used to find the optimization operating point. Results show that increasing the width of the wet channel is not conducive to plume abatement and water conservation, but is beneficial for reducing the outlet water temperature. However, increasing the width of dry channels results in an opposite phenomenon, and the outlet water temperature and water saving rate are more sensitive to variation in the dimension of the dry channel. When the width of dry channels enhances from 0.01 m to 0.02 m , the water saving rate average grows by 4.68% with the increase accounting for approximately 72.11%, and the outlet water temperature ascends by 0.62 °C. The three optimization output values are 23.62 °C, 16.31%, and 0.018 kg/kg, and the corresponding wet and dry channels width are 0.03 m and 0.02 m respectively. [ABSTRACT FROM AUTHOR]

This paper describes an investigation into the combined effects of magnetoconvection and an externally applied magnetic field on the thermal performance of vegetable oil-based magnetic nanofluids with different volume fractions of magnetic nanoparticles. The mineral-based oil has conventionally been used in power transformers because it has high dielectric strength and good cooling performance under normal operating conditions. Because of the environmental impact, eco-friendly vegetable-based transformer oils have been substituted for mineral-based insulating oils. To date, related studies have only reported on the characteristics of dielectric breakdown in vegetable oil-based magnetic nanofluids without any real electromagnetic systems. Furthermore, the thermal characteristics of vegetable oil-based magnetic nanofluids have not yet been fully investigated. Thus, the aim of this paper was to examine the cooling performance by adding magnetic nanoparticles to the vegetable-based transformer oil. To quantitatively analyze this effect, a multi-physics technique that incorporates magnetic-thermal-fluidic fields was developed as based on quasi-static magnetic field approximation and conjugate heat transfer. To validate the numerical results, corresponding experiments were successfully carried out via application in a simple electromagnetic system with varying insulating liquids. [ABSTRACT FROM AUTHOR]

As the key heat transfer components for large-scale natural draft dry cooling tower (NDDCT), the cooling deltas perform poorly when subjected to ambient crosswinds, thus leading to the cooling performance degradation of NDDCT. To enhance the cooling delta's heat transfer capabilities, the effect mechanisms of aerodynamic field equalizing, i.e. air equalizing, on the deltas were studied by the validated three-dimensional (3D) numerical model. For the deltas arranged around NDDCT, the aerodynamic fields, the air flow rates, and the water temperature were all analyzed for cooling columns composing deltas. By comparing the two situations with air equalizing or without in the midst of cooling delta, it could find that the air equalizing diminished the air flow rate differences between the two columns in one delta, which improved the cooling characteristics of the poorer-performing columns mostly at the delta's leeward but deteriorated those of the better-performing columns mostly at the delta's windward. With the air equalizing, the cooling characteristics of the two columns in one delta were balanced. And then the cooling characteristics of most deltas and the whole NDDCT were improved to some extent at varying crosswind speeds, which was significant for the design optimization of conventional delta-type radiators. [ABSTRACT FROM AUTHOR]

To investigate the effects of spray precooling parameters on the cooling characteristics of litchi fruit, a spray precooling test platform was established. “Huaizhi” litchi fruit was chosen as raw materials for this study. The effects of spray temperature and spray flow rates on the cooling coefficient, 7/8 cooling time, and cooling uniformity, as well as the characteristics of multilayer litchi spray cooling, were studied. For spray precooling of single layer litchi, the lower the spray temperature was, the bigger the cooling coefficient was, the shorter the 7/8 cooling time was, and the worse the temperature uniformity of the fruit was. When the spraying temperature was less than (5±0.5)℃, the 7/8 precooling time was shortened, and the precooling unevenness increased significantly (P<0.05). The effects of spray temperature to achieve rapid precooling was limited. Therefore, a spray temperature of (5±0.5)℃ could be chosen in the actual precooling process, and it could maintain the precooling uniformity and accelerate precooling rate of litchi. With the increase of pray flow rate, the cooling coefficient initially increased and then stabilized, and the 7/8 precooling time initially shortened and then leveled gently, and the fruit temperature uniformity increased. The 7/8 precooling time had a quadratic function relationship with the spray flow rate. The 7/8 precooling time decreased slowly when the spray flow was higher than 5.9 L/(s·m2). This was because the contact area between the litchi and cold water increased more slowly than the flow rate. Therefore, the flow rate of litchi spray precooling could be selected to be 5.9 L/(s·m2), which could improve the precooling efficiency and reduce the energy consumption of the pump. When multilayer litchi fruits were stacked, the closer the spray nozzle was, the bigger the cooling coefficient was, the shorter the 7/8 precooling time was, and the better the temperature uniformity was. The relative precooling time had a quadratic function relationship with the number of layers, and the number of critical precooling layers was 4.1. When the number of litchi stacks was larger than or equal to 4, the relative precooling time varied little. To improve the precooling efficiency, the number of litchi stacks should be bigger than or equal to 4. However, as the number of layers increased, the precooling uniformity gradually deteriorated. When the multilayer litchees were stacked, the cooling rate of each layer was inconsistent, the precooling time was longer, and the precooling final temperature was not coordinated. The whole process of precooling took 14.02 minutes. After precooling, the σ of the middle longitudinal section was 0.14, and the average temperature was 7.15 ℃. In single layer litchi spray precooling, the spray temperature could be selected as (5±0.5)℃, and the spray flow could be selected as 5.9 L/(s·m2). The parameters of the single layer litchi spray precooling were used to precool the multilayer litchi, and the number of layers of the best stack of litchi was found to be 4. The research results provided reference for the design of litchi spray precooling equipment and single-layer and multilayer litchi precooling applications. [ABSTRACT FROM AUTHOR]

The solidification and cooling of a continuously cast billet, slab or cylinder (generally a concasting) is a very complicated problem of 3-D transient heat and mass transfer. This paper is focused on the derivation of boundary conditions, i.e. the values of the heat transfer coefficient (HTC) on all boundaries of the concasting machine (CCM). The definition of boundary conditions is the most difficult part of the investigation of the thermokinetics of this process. The boundary conditions in the numerical model of the temperature field of the concasting are defined as the heat transfer by convection. This HTC includes the so-called reduced convection coefficient corresponding to heat transfer by radiation. This paper therefore continues with a discussion on heat transfer coefficients under air-water cooling jets, which spray the concasting in the so-called secondary-cooling zone.

A conception with ground as a heat sink directly for cooling of the buildings in cold areas is presented. A corresponding experimental system was constructed in Harbin area and operated in summer in 2006. Some important performance parameters, such as the cooling seasonal performance factor (CSPF) and the average heat rejection rate unit depth of borehole, were obtained and some analyses for the system characteristics are made. The experimental results show that the ground sink direct cooling system (GSDCS) presented has great potentialities in energy saving within a specified region. [Copyright &y& Elsevier]

In the dry centrifugal granulation process to treat liquid blast furnace slag, it is critical to clarify the cooling and crystallization characteristics of slag particles, which greatly determine their subsequent reutilization and waste heat recovery. Here, we investigated the cooling characteristics of a single slag particle by simulation in terms of crystal phase content variation, temperature and velocity distributions, average cooling rate, etc. The most influential operating parameter was demonstrated to be the particle size and the dimensionless average cooling rate was determined, thereby helping regulate the cooling process more effectively. Moreover, the exploration in the slag composition indicated that reducing the corrected optical basicity was extremely beneficial to promote the particle quality. In the selection of thermophysical parameters, we concluded that constant viscosity was feasible, while density, conductivity and heat capacity should keep temperature-dependent. These results are expected to provide guidance for the application of dry centrifugal granulation technology. [Display omitted] • The order of importance for various operational parameters is determined. • The average cooling rate of slag grains characterizing cooling degree is predicted. • Slag component with smaller Λ corr is able to promote granulated particle quality. [ABSTRACT FROM AUTHOR]

To analyze and to optimize the cooling conditions at blown film extrusion lines, the cooling air stream has been determined by using a hot wire anemometer. The velocity and temperature profiles of the air stream and the air pressure along the bubble have been measured. During film extrusion the significant process parameters and the cooling air ring geometry have been varied.The goal of these studies is to gain a theoretical description of the cooling air stream. Therefore, the experimental results represent a good basis for developing and checking the results of such a model. [ABSTRACT FROM PUBLISHER]

Over the last two decades, the dimensions of electromechanical systems have decreased to micro, even nano scale, as well as the capacity of these systems has increased, leading to the gradual increase of heat flux density. Hence, the conventional cooling methods cannot completely remove heat from the surface. Electrospray cooling is a novel method used in high heat flux systems with small surface area. In literature, studies investigating the relationship between electrospray cooling and spray characteristics are limited. In the present work, electrospray and cooling characteristics were determined for 3different nozzle diameters, 2 different nozzle – plate separation distances, 4 voltages and 3volumetric flow rates. The relationship between mean flow velocity, mean particle diameter and electrospray modes also were determined by digital image processing. The cooling enhancement ratio (CER) values were calculated for varying voltages, mean flow velocities and mean particle diameters. As a result, it was observed that with the increased voltage, the CER and mean flow velocity increased and the mean particle diameter decreased. According to the experimental results, the maximum value of CER was determined to be 1.9, where the mean velocity of the deionised water and the mean particle diameter were 9 m/s and 102 μm, respectively. [ABSTRACT FROM AUTHOR]