Bottom Surface Temperature Research Articles

Thermohydraulic and entropy characteristics of Al2O3‐water nanofluid in a ribbed interrupted microchannel heat exchanger

AbstractIn this study, an interrupted microchannel heat sink with rib turbulators was studied for its thermohydraulic effectiveness and entropy generation in a compact space. The rib edges are modified to enhance the overall functioning of the system by reducing the pressure drop. The working fluid used was Al2O3‐water nanofluid, and increasing the Reynolds number and nanoparticle concentration triggered a reduction in the heat sink's maximum temperature. These also offer a decrease in resistance to heat transfer, and there is an improvement in the evenness of the temperature of the interrupted microchannel heat sink, as regions with the likelihood of hot spot reduced drastically. At Re = 100, increasing the nanoparticle concentration from 0% to 4% enhanced the heat transfer coefficient by 38.41% for the interrupted microchannel heat sink‐base (IMCH‐B) configuration. Under similar conditions, the convective heat transfer coefficient for the interrupted microchannel heat sink‐fillet (IMCH‐F) increased by 43.69%. Furthermore, at 0.5% concentration, changing the Reynolds number from 100 to 700 augmented the heat transfer coefficient by 70.65%. Thus, the maximum temperature of the substrate's bottom surface was reduced by 53.83°C when the system was operated at Re = 700 and nanoparticle concentration of 4%. The IMCH‐C also showed relatively close results at all observed volume fractions. For the IMCH‐C, the maximum temperature of the bottom surface was reduced by 41.98°C at Re = 700 when compared with Re = 100% and 4% concentration. Although at high Reynolds numbers and concentrations, the pressure drops are higher, the performance enhancement criteria prove that the nanofluid is superior to water and the edge modifications show significant performance improvement. More importantly, the IMCH‐F heat sink showed the optimum performance based on the performance evaluation criteria at Re = 300 and (ie, at this point, the heat transfer coefficient is maximum and the pressure drop is minimum). On the other hand, the optimal thermodynamic performance was observed at Re = 700 and . The numerical results demonstrated a potential way to exploit nano‐suspensions for thermal applications, especially for high‐energy flux systems with compact space constraints.

Modeling of Stochastic Temperature and Heat Stress Directly Underneath Agrivoltaic Conditions with Orthosiphon Stamineus Crop Cultivation

This paper presents the field measured data of the ambient temperature profile and the heat stress occurrences directly underneath ground-mounted solar photovoltaic (PV) arrays (monocrystalline-based), focusing on different temperature levels. A previous study has shown that a 1 °C increase in PV cell temperature results in a reduction of 0.5% in energy conversion efficiency; thus, the temperature factor is critical, especially to solar farm operators. The transpiration process also plays an important role in the cooling of green plants where, on average, it could dissipate a significant amount of the total solar energy absorbed by the leaves, making it a good natural cooling mechanism. It was found from this work that the PV system’s bottom surface temperature was the main source of dissipated heat, as shown in the thermal images recorded at 5-min intervals at three sampling times. A statistical analysis further showed that the thermal correlation for the transpiration process and heat stress occurrences between the PV system’s bottom surface and plant height will be an important factor for large scale plant cultivation in agrivoltaic farms.

Analysis of Heat Reduction through Technique Roof Using Innovative Insulation Technique

Buildings have a significant and continuously increasing impact on the environment. The powerconsumption for comfortable housing is ever increasing, which is adding additional burden to the powercrisis of the world. The main objective of this project is to reduce the heat transfer through the buildingroof by providing thermal insulation, thereby reducing the heat load on the building. Moreover, if thebuilding is to be air-conditioned then effective thermal insulation will reduce the power consumptiondrastically and saves lot of energy consumption. New innovative type of insulation is proposed in this workto reduce the heat transfer through roof structure by using seashells and coconut shells. The coconut shellsand seashells layer along with normal tiles will provide very good thermal insulation and it will maintainlow roof bottom surface temperature when compared with the normal conventional concrete roof withoutinsulation. Two identical experimental rooms were constructed on the top of the college mechanicalengineering department block and were instrumented with thermocouple and RTD along with data loggerfor obtaining continuous experimental results. The amount of heat reduction provided by the insulated roofstructure was calculated using the analytical method. Then the cooling load requirement for airconditioningand the corresponding energy cost per year was calculated for the new CAD lab of themechanical engineering department. The result showed the huge energy savings potential for thisinnovative thermal insulation technique. The electricity savings obtained is around 39.7%. when comparedwith the conventional concrete roof. This innovative technique for providing thermal insulation to thebuilding is more affordable and comfortable for living.

Fiber optic sensors enabled monitoring of thermal curling of concrete pavement slab: Temperature, strain and inclination

An intellectual system is developed to monitor concrete pavement slab subjected to external temperature fluctuations. Truly distributed fiber-optic temperature and strain sensors and an innovative Fabry-Perot interferometer-based optical fiber inclinometer are installed in the concrete pavement slab so as to monitor and evaluate its thermal curling process. The system is demonstrated to be effective in detecting the thermal curling of slab. The results substantiate that the top surface of the slab has a fast reaction rate to the heating/cooling process. The bottom surface temperature has a time-lag comparing to the top surface, which results in a sharp increase then a slow reduction in the top-vs-bottom temperature difference. In the light of the inclinometer, it is proven that the tilt angle of the curvature of the slab has a high degree of synchronization with the top-vs-bottom temperature difference. The temperature/strain distribution maps are also presented and uneven distributions of temperature and strain are captured. Moreover, taking the advantage of the multiplexing capacity of the distributed fiber-optic sensors, the coefficient of thermal expansion (CTE) of the slab can be easily obtained and used to feed a finite element model. Finally, a three-dimensional finite element model is established to completely understand the curling process measured from the monitoring system. The model and the experimental data agree well with each other. While the sensors output realistic temperature and deformations at certain locations, the validated model is able to reveal more details of the nonlinearity inside the slab.

Empirical orthogonal function regression: Linking population biology to spatial varying environmental conditions using climate projections

Ecologists and oceanographers inform population and ecosystem management by identifying the physical drivers of ecological dynamics. However, different research communities use different analytical tools where, for example, physical oceanographers often apply rank-reduction techniques (a.k.a. empirical orthogonal functions [EOF]) to identify indicators that represent dominant modes of physical variability, whereas population ecologists use dynamical models that incorporate physical indicators as covariates. Simultaneously modeling physical and biological processes would have several benefits, including improved communication across sub-fields; more efficient use of limited data; and the ability to compare importance of physical and biological drivers for population dynamics. Here, we develop a new statistical technique, EOF regression, which jointly models population-scale dynamics and spatially distributed physical dynamics. EOF regression is fitted using maximum-likelihood techniques and applies a generalized EOF analysis to environmental measurements, estimates one or more time series representing modes of environmental variability, and simultaneously estimates the association of this time series with biological measurements. By doing so, it identifies a spatial map of environmental conditions that are best correlated with annual variability in the biological process. We demonstrate this method using a linear (Ricker) model for early-life survival ("recruitment") of three groundfish species in the eastern Bering Sea from 1982 to 2016, combined with measurements and end-of-century projections for bottom and sea surface temperature. Results suggest that (a) we can forecast biological dynamics while applying delta-correction and statistical downscaling to calibrate measurements and projected physical variables, (b) physical drivers are statistically significant for Pacific cod and walleye pollock recruitment, (c) separately analyzing physical and biological variables fails to identify the significant association for walleye pollock, and (d) cod and pollock will likely have reduced recruitment given forecasted temperatures over future decades.

Cold range edges of marine fishes track climate change better than warm edges.

Species around the world are shifting their ranges in response to climate change. To make robust predictions about climate-related colonizations and extinctions, it is vital to understand the dynamics of range edges. This study is among the first to examine annual dynamics of cold and warm range edges, as most global change studies average observational data over space or over time. We analyzed annual range edge dynamics of marine fishes-both at the individual species level and pooled into cold- and warm-edge assemblages-in a multi-decade time-series of trawl surveys conducted on the Northeast US Shelf during a period of rapid warming. We tested whether cold edges show stronger evidence of climate tracking than warm edges (due to non-climate processes or time lags at the warm edge; the biogeography hypothesis or extinction debt hypothesis), or whether they tracked temperature change equally (due to the influence of habitat suitability; the ecophysiology hypothesis). In addition to exploring correlations with regional temperature change, we calculated species- and assemblage-specific sea bottom and sea surface temperature isotherms and used them to predict range edge position. Cold edges shifted further and tracked sea surface and bottom temperature isotherms to a greater degree than warm edges. Mixed-effects models revealed that for a one-degree latitude shift in isotherm position, cold edges shifted 0.47 degrees of latitude, and warm edges shifted only 0.28 degrees. Our results suggest that cold range edges are tracking climate change better than warm range edges, invalidating the ecophysiology hypothesis. We also found that even among highly mobile marine ectotherms in a global warming hotspot, few species are fully keeping pace with climate.

Analysis and Optimization of Radiant Cooling Panel with Wave-Type Embedded Pipes

In this study, the radiant cooling panel with wave-type pattern pipes is analyzed and optimized through Taguchi’s design of experiments methods and grey relation method for better performance. Radiant cooling panel’s bottom surface temperature and temperature non-uniformity index are considered as the quality objective functions. Control parameters such as pipe length, the spacing between the pipes, radiant panel thickness, pipe bent radius, pipe diameter, insulation layer thickness, pipe material, panel material, insulation material, and mass flow rate of water entering the pipe are included as the control parameters of the optimization study. The performance of radiant cooling panels is analyzed through numerical simulation technique- computation fluid dynamic (CFD) method. The numerical simulation is carried out in the Fluent software, and the CFD code is checked for grid independence and validation. Through single and multi-objective optimization, the best design of the radiant cooling panel is identified, and a confirmation test is also conducted. Finally, an analysis of variance (ANOVA) calculation is made and it is found that the mass flow rate of water entering the pipe is the most influencing parameter on the performance of the radiant cooling panel.

Experimental investigation of cascading failure in 18650 lithium ion cell arrays: Impact of cathode chemistry

This study provides a comparative analysis of dynamics and hazards associated with cascading failure in lithium ion cell arrays of different cathode chemistries. Each array consists of 3 × 4 cylindrical cells with lithium cobalt oxide (LCO), lithium nickel manganese cobalt oxide (NMC), or lithium iron phosphate (LFP) cathode. Each array is mounted in a wind tunnel supplied with a controlled gas flow. Thermal runaway is induced in one cell using an electric heater and then observed to propagate through the array. Experiments are conducted in nitrogen and air environments to study the combustion impact. Time-resolved recordings of cells’ bottom surface temperatures are utilized to track the thermal runaway propagation and calculate a row-to-row propagation speed. The LFP cells are the only cells that do not always fully propagate thermal runaway. The speed of the propagation is found to be greater in air than in nitrogen. In nitrogen, all cells produce large amounts of hydrocarbons, CO and CO2, and minor amounts of O2 and H2. Total heats generated due to chemical reactions between cell components and flaming combustion of ejected materials normalized by the electrical energy stored are determined to be 3.5, 2.9, and 2.5 for LCO, NMC, and LFP cells, respectively.

Evaluation of Thermal Properties of Cement-Exfoliated Vermiculite Blocks as Energy Efficient Building Envelope Material

Abstract Lightweight exfoliated vermiculite (EV) aggregate particles were mixed with cement-mortar to form exclusive cement-EV specimens of 1:0.5, 1:1, and 1:1.5 wt. % proportions, respectively. The thermal conductivity of these specimens was determined using a fabricated experimental setup, wherein the top and the bottom surface temperatures of the specimen were measured with respect to the heat flux within a specific time interval. Properties such as thermal resistivity, thermal transmittance, thermal performance index (TPI), and thermal damping are investigated using empirical relations and compared to that of the conventional cement-mortar specimen. The compressive strength was determined in accordance with the ASTM C31 standards for 7 and 28 days of curing. From the results, it was identified that the compressive strength of cement-EV 1:1 was 13.5 % less than cement-EV 1:0.5. The strength of cement-EV 1:1.5 was observed as 72 % and 51 % less than that of cement-EV 1:0.5 and 1:1, respectively. This is due to the increase in the porosity of the specimen. A significant reduction was noticed in the thermal conductivity of cement-EV 1:1.5 value (0.189 W/mK), with an increased value of resistivity (5.29 mK/W) when compared to that of the cement-mortar specimen. The TPI of the cement-EV 1:1.5 was reduced to 57 % less than the TPI of the cement-mortar, with an indication of the higher thermal stability of the material. Similarly, the results also showed an increase of 56 % and 71 % damping values for cement-EV 1:1 and 1:1.5, respectively. Hence, cement-EV proportions provide satisfactory strength and thermal properties for its usage as a lightweight building envelope in residential constructions, with higher thermal resistance and stability against fluctuating external temperature ranges.

Leidenfrost Pattern Formation and Boiling

We report on Leidenfrost patterns and boiling with compressed sulfur hexafluoride (hbox {SF}_6). The experiments were carried out in a large aspect ratio Rayleigh–Bénard convection cell, where the distance between the horizontal plates is comparable with the capillary length of the working fluid. Pressures and temperatures were chosen such that the bottom plate was above and the top plate was below the liquid–vapor transition temperature of hbox {SF}_6. As a result, hbox {SF}_6 vapor condenses at the top plate and forms drops that grow in size. Leidenfrost patterns are formed as the drops do not fall but levitate by the vapor released in the gap between the hot bottom plate and the colder drops. When the size of these drops became too large, one or more vapor bubbles—chimneys—form inside them. We determine the critical size for the formation of a chimney as a function of the capillary length. For even larger drops and extended puddles many disconnected chimneys occur that can grow to sizes large enough for the formation of new drops inside them. By varying the temperatures and the pressure in the system, we observe various such patterns. When the area covered by a puddle becomes large it touches the hot bottom plate locally and boils off rapidly. This can be attributed to a local reduction of the bottom plate surface temperature below the Leidenfrost temperature.

Numerical Analysis On Fluid-solid Coupling Cooling Of Minimal Surface Lattice Structure

This paper established the minimal surface lattice structure cooling model, researched the fluid-solid coupling cooling properties in addition flow by interface function transmit and compared the cooling properties of different minimal surface lattice and bar lattice in the same density. The influence of cooling fluid velocity was considered. The thermal stress and impact stress of the structure was analyzed by sequential coupling method. The result showed that the minimal surface structure had better cooling properties. The bottom temperature decreased with the increase of coolant flow velocity. There was a threshold for different structures, when the flow rate exceeded this value, the bottom surface temperature will not decrease. Stress analysis showed that stress concentration occurred at the junction of lattice and panel. The overall stress decreased first and then increased with the increase of flow rate.

Metallic integrated thermal protection structures inspired by the Norway spruce stem: Design, numerical simulation and selective laser melting fabrication

With the development of hypersonic vehicles and reusable launch vehicles, the design of integrated thermal protection (ITP) structures needs to meet the demanding requirement of thermal protection. More complex geometries, such as lattice structures and bio-inspired structures, have been introduced into the design of ITP structures, aiming to enhance the thermal protection performance. Additive manufacturing holds high flexibility in processing and enables more complex designs, which is suitable for the fabrication of complex ITP structures. In this paper, inspired by the structures of Norway spruce stem, a series of ITP structures with different gradient hollow designs was proposed and manufactured by selective laser melting (SLM). The steady-state and transient thermal behavior of those bio-inspired ITP structures were investigated by finite element method (FEM). To verify the accuracy of the FEM simulation results, Ti6Al4V components with different bio-inspired ITP structures were fabricated by SLM and thermal conductivities of those SLM-processed components were experimentally measured. The FEM thermal simulation revealed that the gradient-structure with larger hollow tubes near the top and bottom plates and smaller hollow tubes in the center possessed the lowest bottom surface temperature of 262.8 °C, which was 21.4 °C lower than the structure with the highest bottom surface temperature. The thermal conductivity measurement revealed that the gradient-structure, with the lowest bottom surface temperature obtained by FEM thermal simulation, had the lowest thermal conductivity of 2.321 W/(m⋅K), which was about 29% lower than that of the structure possessing the highest thermal conductivity.

Multi-criterion optimization of thermohydraulic performance of a mini pin fin heat sink operated with ecofriendly graphene nanoplatelets nanofluid considering geometrical characteristics

This paper aims to examine and optimize thermal and hydraulic characteristics of an ecofriendly graphene nanofluid in a pin fin heat sink for cooling of electronic processors. The cylindrical fins with different diameters and heights are employed. By increasing each of the parameters of concentration, fin height and fin diameter, the bottom surface temperature decreases while the pumping power intensifies. Meanwhile, the temperature distribution becomes more uniform, which can decrease possibility of hot spot formation. The fin height has more significant effect on the temperature compared with the fin diameter. Although adding the nanoparticles improves the cooling noticeably, the pressure drop and pumping power do not experience significant variation. The surface temperature and pumping power are considered as the objective functions, and optimal values of the concentration, fin diameter and fin height are obtained for minimizing them. The compromise programming method is employed along with the genetic algorithm to include viewpoints of designer in the optimization. The fin height has a rather similar effect on the two objective functions, whereas the concentration and fin diameter vary the pumping power much lower than the surface temperature. Finally, employing the nanofluid with high concentrations is recommended for utilization in the heat sink.

Evaluations of heat treatment on polymer adhesive bonding and thermal-induced failure of two-layer through-silicon via structures

In the present study, upper and lower substrates made of p-type Si were bonded using benzocyclobutene (BCB) glue, which was then solidified via rapid thermal annealing at various chamber atmospheres. Inductively coupled plasma was applied to prepare through-silicon via (TSV) holes that penetrated the wafer-BCB-wafer (WBW) composite specimen. SiO2 and Ti films and copper pillars were deposited and filled in sequence to form the WBW TSV structure. These specimens were prepared for thermal tests to determine the earliest failure (fracture) time (Tfailure) for the Ti and SiO2 films and the time required for electrical current breakdown (TBD) in the specimens. Theoretical models, including the Johnson-Cook (J-C) fracture model and a numerical scheme, were developed to predict the Tfailure values for the Ti and SiO2 films. Black’s equation was applied to determine the variations of specimen activation energy with externally applied bottom surface temperature and electrical voltage. The numerical results for (Tfailure)Ti, (Tfailure)SiO2, and TBD are obtained quite close to those from the experiments. The elastic modulus of the solidified BCB material can be increased by fabricating the WBW structure under high vacuums. A relatively lower BCB elastic modulus can lower the maximum strain energy density required for fracture in the SiO2 film of the TSV structure, thus effectively increasing TBD. The rate of effective activation energy is the dominant factor for TBD. The effective activation energy in the preparation of BCB bonding decreases with increasing the vacuum.

Efficacy of a hybrid nanofluid in a new microchannel heat sink equipped with both secondary channels and ribs

This paper aims to evaluate the thermohydraulic attributes of a hybrid nanofluid containing graphene–silver nanoparticles in a microchannel heat sink equipped with the ribs and secondary channels. In addition to the heat transfer surface increment, the ribs direct the flow towards the secondary channels, and intensify the flow mixing. Meanwhile, the secondary channels increase the flow area, which reduces the pressure drop due to the presence of the ribs. The results show that combining the three approaches, namely employing the nanofluid, ribs and secondary channels in the microchannel improves the heat sink performance significantly. With increasing either concentration or Reynolds number, the temperature decreases, the temperature uniformity enhances, and the regions with highest temperatures become smaller. Additionally, the average convective heat transfer coefficient enhances with increasing the concentration and Reynolds number such that with increase of the concentration from 0 to 0.1% at Re = 100, a 17% enhancement happens in the convective heat transfer coefficient. Moreover, the bottom surface temperature decreases with increment of the concentration such that a 3.42 K reduction occurs with increasing the concentration from 0 to 0.1% at Re = 100. Meanwhile, the flow experiences a greater pumping power at higher Reynolds numbers and concentrations.

Experimental study of the heat transfer characteristics of supercritical pressure R134a in a horizontal tube

This study experimentally investigates the heat transfer characteristics of R134a at supercritical pressures in a 10.3 mm horizontal tube to provide basic heat transfer data and heat transfer correlation. The experiments cover wide parameter ranges of p = 1.02–1.2 pc, G = 400–1500 kg/m2 s, and q″ = 20–100 kW/m2. The influences of the heat flux, the mass flux and the pressure on the wall temperature and heat transfer coefficient are analyzed. The results show that in a horizontal tube, the buoyancy effect due to density variations causes non-uniformity of the wall temperatures in the circumferential direction. The heat transfer deteriorates along the top surface at high q″/G (heat flux to mass flux ratio), while the heat transfer along the bottom surface is enhanced at all operating conditions. The pressure mainly affects the heat transfer coefficient on the bottom surface at small q″/G because of the cp variation with pressure. Nine heat transfer correlations are evaluated with the results showing that the Dittus–Boelter type correlations with property modifications have acceptable accuracy for the bottom surface but all of the correlations fail to predict the heat transfer coefficients on the top surface. A new correlation using a buoyancy parameter to include the buoyancy effect is then developed to predict the top surface temperatures and a DB type correlation with property modifications is used to predict the bottom surface temperatures. Results show that the new correlations agree well with the data.

The laboratory evaluation of incorporating ceramsite into HMA as fine aggregates

The aim of this paper is to explore hot asphalt mixture (HMA) with potential cooling capacity through adding ceramsite. Ceramsite asphalt mixtures (CAM) are prepared by adding ceramsite to replace fine aggregate with different ratio. Marshall and pavement performance tests were performed to test the pavement performance of CAM. Indoor radiation and outdoor radiation tests are carried out to evaluate the thermal properties of CAM. Results indicate that the Marshall Stability and dynamic stability of CAM increase with the increasing ceramsite ratio from 0% to 60%. The retained MS and low temperature performance of CAM nearly do not change with ceramsite ratio, but the tensile strength ratio decreases with ceramsite ratio. However, all values of the tensile strength ratio are above the requirements of specification. In the aspect of the thermal properties of CAM, the addition of ceramsite can effectively reduce the thermal conductivity of asphalt mixtures. Also, ceramsite is helpful in reducing the temperature of pavement and enhancing the ability of heat resistance, and the optimal effect can reduce the bottom surface temperature about 2.6 °C when ceramsite ratio is 60%. Because of the improvement in the dynamic stability and the thermal conductivity, CAM can have a good rutting resistance and the recommended ceramsite ratio is 60%.

Nonlinear thermal buckling analyses of functionally graded circular plates using higher-order shear deformation theory with a new transverse shear function and an enhanced mesh-free method

This study presents nonlinear buckling analyses of functionally graded (FG) circular plates in thermal environments using a mesh-free method. The thermal buckling response is formulated based on higher-order shear deformation plate theory in which a new transverse shear function is incorporated to better represent the displacement fields. An enhanced mesh-free radial point interpolation method (RPIM) in which the shape functions are constructed without any fitting parameters by virtue of the radial basis function in a compactly supported form is developed and utilized to explore the thermal buckling behavior. A radial basis function in a compactly supported form is proposed and included in the RPIM. Two types of FG circular plates with different FGM orientation, i.e., metal–ceramic FG circular plates and ceramic–metal FG circular plates, are considered in the analyses. The effectiveness and accuracy of the enhanced RPIM based on the higher-order shear deformation theory is first confirmed by simulating a numerical example found in the literature and comparing the results with the analytical solutions. Detailed parametric studies are then performed to investigate the effects of the volume fraction, plate thickness-to-radius ratio and metallic surface temperature on the critical buckling temperatures of FG circular plates subjected to various through-thickness temperature distributions. Results demonstrate that the enhanced mesh-free RPIM based on the higher-order shear deformation plate theory with the proposed transverse shear function can effectively predict the thermal buckling responses of FG circular plates, and that the volume fraction, plate thickness-to-radius ratio, bottom surface temperature and FGM orientation have considerable effects on the critical buckling temperatures.

Effects of SiO2 film thickness and operating temperature on thermally-induced failures in through-silicon-via structures

In the present study, the experimental results of the thermally induced failure (fracture) time for the components of copper through‑silicon via (TSV) structures and the time for electrical current breakdown (TBD) are obtained to investigate the effects of the thickness of the SiO2 film and the operating temperature. The numerical scheme is also developed to solve the distributions of transient temperature and stress in the specimen and the equivalent stress/strain for the elements in the Ti, SiO2 and Si components of the TSV structure. The equivalent element stress solutions incorporating with the Johnson-Cook (J-C) fracture model are provided to identify the earliest failure element and time in each of these three components and the TBD of the structure via the definition for the D factor. The applied models and numerical scheme are confirmed to be trustworthy from the comparison of the numerically predicted and experimental results for these failure time parameters. The effects of the operating temperature of specimen's bottom surface and the film thickness of SiO2 on these time parameters have been evaluated precisely. The TBD time is elongated by increasing the thickness of either SiO2 or Ti film if the bottom surface is operating at a fixed temperature. The earliest failure time (tfailure) for the components of Ti, SiO2 and Si wafer and the TBD are always reduced by the rise of operating temperature.

Effect of slot-jet position on the cooling performance of the hybrid trapezoid channel and impingement module

This paper investigated the effect of slot-jet position on the cooling performance of the hybrid trapezoid channel and impingement module. Cooling performances of trapezoid channels with different slot-jet positions were comparatively discussed using the realizable k-ε turbulent model. Apart from the channel with α = 0.25 (the dimensionless distance that the slot-jet deviates from the symmetry axis of trapezoid channel), both the temperature and the temperature difference (the difference between maximum temperature and minimum temperature) of the module bottom surface firstly decline and then rise with the increase of α. When the slot jet is at the position of α = 1.00, the module achieves the minimum bottom temperature. While the slot jet is at the position of α = 0.50, the module reaches the minimum bottom temperature difference. Considering the bottom temperature and bottom temperature difference, the slot-jet position α = 0.75 is recommended in the practical application. Besides, the difference among the cooling performances of channels with different slot-jet positions gradually decreases with the increase of pump power. Furthermore, the cooling performance of the channel with α = 0.25 is deeply affected by the pump power. At the low pump power, both bottom temperature and bottom temperature difference of the channel with α = 0.25 are larger than that of the channel with α = 0.00. While at the high pump power, not only is bottom temperature of the channel with α = 0.25 lower than that of the channel with α = 0.00, but also temperature difference of the former is smaller than that of the latter.