Average Temperature Difference Research Articles

Effects of Boundary Conditions on Performance Prediction of Deep-Buried Ground Heat Exchangers for Geothermal Energy Utilization

An accurate prediction for deep-buried ground heat exchangers (DBGHEs) is the premise for efficient utilization of geothermal energy. Due to the complexity of the geological composition spanning thousands of meters, the configuration of boundary conditions plays a critical role in evaluating DBGHE thermal performance. This paper proposed a three-dimensional model of full-scale DBGHE involving both conductive and convective heat transfer in aquifuge and aquifer layers. The constant inlet temperature and constant heating power boundaries in the DBGHE domain, and the surface–bottom temperature and heat flux boundaries in the rock-soil domain were examined. It was found that the differences in the performance prediction caused by different DBGHE boundary conditions were closely related to the system’s operating time. The relative differences in heat extraction amount and average borehole temperature of 2000 m DBGHE caused by the two inlet boundaries on the 30th day were, respectively, 19.5% and 18.3%, while these differences on the 120th day were decreased to 8.4% and 9.9%, respectively. It was found that the constant inlet temperature boundary was more appropriate than the constant heating power condition for estimating aquifer effects on the performance of DBGHE. For the rock-soil domain, the results showed that the heat extraction amount of DBGHE under the heat flux boundary was 12.6%–13.6% higher than that under the surface–bottom temperature boundary. Particularly, when considering the velocity change of groundwater in the aquifer, the relative difference in heat extraction amount increments caused by the two types of rock-soil boundaries can reach 26.6% on the 120th day. It was also found that the thermal influence radius at the end of a heating season was hardly affected by either the DBGHE inlet or rock-soil domain boundary conditions.

Electrical–thermal–fluidic coupling Li-ion battery pack consistency study

The thermal effect of lithium (Li)-ion batteries affects its performance and service life and threatens its safety. Therefore, a new tree-shaped channel heat sink was developed for cooling Li-ion battery packs and compared with fractal and serpentine channel heat sinks. Moreover, the electrical–thermal–fluidic multi-physics simulation was implemented based on the equivalent circuit model. The temperature distribution effect on the battery pack's consistency was investigated. Different circuits were established through various series–parallel topologies, and the battery pack's discharging and temperature characteristics were examined when the cells' initial parameters were different. The results demonstrated that the new tree-shaped channel heat sink offered effective heat dissipation and small flow resistance. The decreasing temperature difference enhanced the current consistency, while the decreasing temperature rise reduced the voltage consistency. The series or parallel connection between the battery modules slightly affected the battery pack's discharging and temperature characteristics. Within the module, a reduction in the number of batteries in series or augmentation in the parallel branches reduced the battery consistency and increased the battery pack's average temperature rise and temperature difference. The battery consistency in the parallel-first topology module was better than that in the series-first topology module under the same number of parallel branches. These results are helpful for the battery pack consistency studies.

Numerical investigation of novel manifold microchannel heat sinks with countercurrent regions

Manifold microchannel (MMC) heat sink is a potential method to dissipate high heat fluxes of electronic devices. Traditional Z-type MMC is a simple configuration but usually encounters high temperature difference and pressure drop. In this work, we introduced countercurrent flows to alleviate these problems by revising the design of manifold configurations. Six cases with different manifold arrangements are numerically investigated using single-phase deionized water at mass flow rates ranging from 0.04 - 0.12 g/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The cases with countercurrent regions can reduce the maximum temperature around 5 K compared with the original cases with parallel regions. The temperature difference of the ZU-type MMC with double-layer countercurrent flow configuration is lower than 4 K, which is about 25% of the original Z-type MMC. For the revised manifold configuration with countercurrent flows, the pressure drops also decrease due to the split of inlets and outlets of the manifold. The pressure drops of single-layer and double-layer countercurrent manifolds are respectively 27.13% and 33.36% lower than that of the case with traditional Z-type manifold. This leads to a higher comprehensive performance of revised cases with countercurrent flows. Besides the better temperature uniformity, the fluid flow becomes more uniform in the microchannels for the revised case. The improved ZU-type MMC with double-layer countercurrent flow can dissipate 1100 W/cm2 for single-phase flow with a temperature increase of 80 K and a pressure drop of 22 kPa at mass flow rate of 1.2 g/s.

Biomimetic optimized vertically aligned annular fins for fast latent heat thermal energy storage

Latent heat thermal energy storage (LHTES) technology has been widely used in balancing energy demand and intermittent energy supply, as well as thermal management in buildings, but suffers from slow heat storage rates. Here, biomimetic topology-optimized vertically aligned annular fins are proposed to accelerate heat storage performance. Taking the maximum average temperature as the optimization objective function, optimized biomimetic fins can shorten the melting time by 45.9% compared with traditional fins as verified by experimental measurements. Such a fast heat storage rate is also superior to that of pitch-varying fins and diameter-varying fins by 18.4% and 23.5%, respectively. Meanwhile, the temperature uniformity is greatly improved by biomimetic fins with a reduction of average temperature difference in phase change materials (PCMs) by 75.3%. The underlying mechanism can be attributed to accelerated melting of PCMs close to the outer bottom boundary due to unique bifurcation structures of topology optimized fins. The fractal dimension of optimized fins is similar to that of leaf vein structures, demonstrating that proposed topology structures are close to Natural’s optimal solutions. This study provides novel biomimetic structures for accelerating thermal energy storage rate and promotes the application of biomimetics in LHTES techniques.

Predicting temperature of semi-solid 7075 aluminum alloy slurry prepared by a novel rheocasting route via neural network

The rapid preparation of desired semi-solid slurry with a specific average temperature and a high temperature uniformity is of essential importance for the rheocasting of high-strength aluminum (Al) alloys. In this study, a novel semi-solid slurry preparation process, namely Enthalpy Control Process (ECP), has been proposed for rapid preparation of 7075 Al alloy slurry. The machine learning approach from the aspect of neural network was utilized to predict the average temperature and maximum temperature difference of the Al slurry prepared by ECP. The results indicated that the temperature values predicted by Back Propagation Neural Network optimized by Genetic Algorithm (GA-BPNN) models exhibit an excellent fit with the experimental results. The average relative error and the coefficient of determination for average temperature of were 0.9988 and 0.027%, while the values for the maximum temperature difference were 0.9910 and 3.4%, respectively. The GA-BPNN has a great latent capacity in predicting the temperature of the semi-solid slurry.

Long-term borehole energy storage by the inlet position control for low temperature heat source application

Borehole thermal energy storage (BTES) systems are gaining attention due to their potential to efficiently store and release thermal energy. However, the conventional BTES systems often suffer from reduced efficiency under low heat source temperature conditions. This study aims to address this issue by introducing and evaluating the inlet position control method, a novel approach to enhance the BTES performance for low-temperature heat source applications. A single-cycle 3D simulation model, substantiated by experimental data from a BTES system installed in the YeonCheon region, Korea, is developed using the ANSYS Fluent program. The model investigates the heat transfer from the water heat source to the soil and compares the performance of the conventional method with the inlet position control method in terms of heat gradient contours and average temperature difference in the soil. The inlet position control method is found to improve the BTES storage efficiency by 11.90% during the early winter season of the thermal release period in the third year, compared to the conventional method. The standard deviation for simulation data is ± 1.787 with a peak error of 2.4%, indicating the effectiveness of the simulation model. Furthermore, the inlet control method enhances the BTES storage efficiency under low heat source temperature conditions and promotes faster thermal equalization, resulting in a 4.2% improvement in thermal energy release efficiency. We demonstrated the novelty of the inlet position control method in improving BTES performance and its applicability to low-temperature heat source applications. The findings have significant implications for the design and operation of future BTES systems, with the potential to expand their application in various industries and climates.

Cement rotary kiln temperature prediction based on time-delay calculation and residual network and bidirectional novel gated recurrent unit multi-model fusion

China's cement production energy consumption accounts for more than 10% of the country's total energy consumption, and its emissions account for about 60% of the country's industrial emissions. The temperature of a cement rotary kiln directly affects the quality of the final product, the energy consumption of a plant, and emissions. Therefore, it is necessary to measure, to a high degree of accuracy, the temperature of a cement rotary kiln to reduce energy consumption, emissions, and improve product quality. However, the conditions in cement kilns are complex and variable; and there are large time-delays, while temperatures are affected by historical working conditions, making temperature measurement extremely difficult. In this paper, a modelling algorithm with a residual network and a bidirectional novel gated cycle unit is used to predict the clinker exit temperature of the rotary kiln. In addition, to solve the problem of large time-delays in cement kilns, a dynamic time-delay calculation algorithm based on Mutual information and adaptive sliding windows is proposed for time series data reconstruction, and finally a Gaussian-weighted multi-model fusion is applied to the prediction results for cement rotary kilns that produce a wide range of working conditions. To verify the advantages and feasibility of the proposed method, experimental validation is carried out using original production data from a large cement manufacturing enterprise in South China. The results demonstrate that the single step prediction time of the presented approach is 0.66 s, which can predict cement kiln temperatures quickly and accurately, compared to a single conventional forecasting algorithm, the average temperature difference dropped from 11.76 °C to 3.51 °C, R2 increased from 0.43 to 0.89, 94% of the depicted temperature errors are at ± 10 °C This will provide an effective solution for online decision-making during actual cement production.

Thermohydraulic performance analysis of HCPV/T systems with impinging confined jets and symmetric multi-junction PV modules

BackgroundThis study investigates the cooling of four high-concentrator photovoltaic/thermal systems with panels that have two lines of symmetry. Liquid-submerged jet impingement is used to cool four symmetric multi-junction modules. The performance of four circular impinging jets with nozzle diameters of 1 mm under each cell is compared with that of a circular impinging jet with a nozzle diameter of 2.5 mm at the center of the heat sink. The solar radiation of 1000 suns is considered in the simulations. The flow regimes are laminar, and the results are obtained for mass flow rates within the range of 100-200 gr/min. MethodsSince the geometry of the problem is complex, no analytical solution for temperature distribution is available. Also, there are no suitable tools for measuring the temperature distribution in the flow and solid walls at the desired scales. Therefore, a three-dimensional simulation using the finite volume method by Fluent was used in this research. To apply the relationship between the cell temperature and the electrical efficiency in each iteration and achieve the new cell temperature, a User-defined Function (UDF) has been developed. FindingsThe cell arrangement on panels in both jet configurations (four nozzles and a single nozzle) gives average cell temperature differences that are less than 1°C. The single nozzle system reduces the flow pressure drop while it increases the maximum temperature of the germanium layer by 8°C and makes its temperature more non-uniform than the four nozzles system with the same configuration. The non-uniformity in the surface temperature of the germanium layer in all the models varies between 10°C and 20°C which indicates the necessity of combining this technique with another method to cool such a system.

Numerical Modeling of Thermal Behavior during Lunar Soil Drilling

This paper presents a detailed thermal simulation analysis of the drilling process for icy soil in the lunar polar region. The aim is to investigate the temperature changes that occur in the debris removal area during the drilling process. We developed a multi-level particle size simulation model that includes a thermal sieve based on geometric constraints to evaluate the influence of specific heat capacity and thermal conductivity on particle temperature. Using the central composite design method, we carried out the simulation test design and analyzed the average temperature difference of particles within and outside the range of the thermal sieve. The parameters of the discrete element model were determined by comparing the temperature of the debris removal zone in the lunar environment with the temperature simulated by the discrete element method. The results show that the thermal conductivity of the sieve ranges from 100 to 400 W/m, and the average temperature inside the thermal sieve is negatively related to the specific heat capacity. The temperature deviation of the chip removal area is ±10 °C, which is consistent with the temperature deviation observed in the lunar environment and the lunar icy regolith drilling test. Furthermore, the addition of the thermal sieve to the multi-stage particle size simulation modeling significantly reduces the calculation time by 86%. This reduction in computational time may potentially increase the efficiency of drilling operations in the future. Our study provides insights into the thermal behavior of lunar icy regolith during drilling, and proposes a numerical model of heat transfer with a thermal sieve that can effectively reduce computational time while ensuring accurate temperature calculations.

Thermal and hydrodynamic characteristics of single-phase flow in manifold microchannels with countercurrent regions

Manifold microchannel heat sink is promising to dissipate high heat fluxes for electronic devices due to its high surface to volume ratio. Traditional Z-type manifold encounters fluid flow maldistribution and a high temperature difference. In this work, two inlets and countercurrent flows are introduced into the manifold arrangement to alleviate these problems in the Z-type manifold microchannels. Six cases with different manifold arrangements are numerically investigated using single-phase HFE-7100 at mass flow rates ranging from 56.8 to 117.78 mg/s. The results show that the maximum temperature, average temperature, and temperature difference of the revised arrangements are all lower than these of the traditional Z-type manifold arrangement. The minimum temperature difference for an ideal multi inlet manifold arrangement can be less than 0.2 K, while the value is about 5.3 K for the traditional Z-type manifold arrangement. The revised arrangement can also improve the uniformity of mass flux distributions. The ratio of the maximum to the minimum mass flux within microchannels is 12.83 for the traditional Z-type manifold, while this value is about 5.82 for cases with two inlets and countercurrent zones. A longer flow path and a higher local pressure drop in the revised arrangements results in higher pressure drops than the traditional Z-type manifold microchannels. Compared with the traditional Z-type arrangement, heat transfer coefficients and performance evaluation criterion are higher for the improved cases. The presence of a countercurrent zone can improve the comprehensive performance of the manifold microchannel. New criterion based on the thermal resistance calculated at the maximum temperature is proposed to evaluate the cooling performance of electronics.

Monitoring of a Living Wall System in Santo Domingo, Dominican Republic, as a Strategy to Reduce the Urban Heat Island

Given the current need to reduce the Urban Heat Island (UHI) worldwide, one of the strategies that can contribute to this mitigation is green façades. In this context, the aim of this research is to evaluate a Living Wall System (LWS) as a strategy to reduce the urban heat island in Santo Domingo, Dominican Republic, using outdoor test cells. This research was focused on the monitoring of two different façades, an LWS and a reference façade, during the warmer months. For the comparison, the parameters measured were air temperature, relative humidity, surface temperature and environmental variables. In addition, thermal images were taken. Results reveal that during the days selected, the average outdoor air temperature difference between the LWS compared to the reference façade was 5.3 °C, whereas during the day, the average was 3.3 °C. Concerning surface temperature, in the case of the LWS, the temperature was higher and had greater fluctuations than the reference façade. This behavior was confirmed by the results obtained with thermal images. In conclusion, using an LWS in a tropical climate helps the urban microclimate, which contributes to urban heat island effect mitigation during the warmer months.

Optical and thermal performance analysis of a compact solar collector with heat-pipe evacuated tube

Process industry consumed 15 % to 30 % of the global energy, and 40 % of it is thermal energy demand in the range of 80 °C-250 °C. To produce mid-temperature heat, a new solar collector was designed with heat pipe evacuated tube, including several parallel micro-parabolic troughs, heat pipes, double-layer vacuum tubes contained in a compact frame and an external mechanical solar tracker. In addition, the selective absorbing coating (SAC) was applied on the inner surface of the vacuum tube, and the gap between the heat pipe and the vacuum tube was filled with heat transfer oil. Since the height of the designed collector was only 124.5 mm, it can be easily integrated with buildings. Genetic algorithm (GA) was used to optimize the structural parameters based on maximum obtained solar energy of the collector, and theoretical analysis and numerical simulation are carried out for optical and thermal performance of the collector. The analytical and numerical results showed that the annual average optical efficiency is 57.6 % and the thermal efficiency is 30.6 % at 250 °C when the normalized temperature difference is 0.23. By exergy analysis, the collector has a maximum exergy efficiency of 15.5 % with operating temperature of 204.4 °C, which is the station of the best thermal performance of the collector. Furthermore, theoretical model was verified to be valid by a prototype. Overall, the proposed collector is suitable for mid temperature industrial applications and integrated with rooftop.

Investigation of the Effective Voltage and Performance of Thermocells

Thermocells, also called thermogalvanic cells, are a promising technology that can efficiently harvest low-grade waste heat with direct thermoelectric conversion. The cells operate under a temperature difference, with one electrode on the hot side and the other on the cold side. The recently developed electrodes, such as porous carbon materials and pin-structured electrodes, have led to a temperature gradient even inside one of the electrodes. However, it still remains an open question of what temperature difference determines the open-circuit voltage of thermocells. Here, we investigated the effective voltage of a thermocell with thick electrodes. The temperature difference that determines the voltage turned out to be the smallest temperature difference between anode and cathode electrodes, the average temperature difference, or in between, depending on the internal resistances of the cell. We also verified the validity of normalized power density estimated from the open-circuit voltage. In addition, a strategy was demonstrated to improve the power density of a thermocell that consists of thick electrodes. The results provided here would help devise high-performance thermocells with optimized electrode structures.

A candidate strategy for low-temperature preheating of lithium-ion batteries based on supercooling salt hydrates

Preheating is necessary for lithium-ion batteries to avoid severe performance degradation and potential safety hazards at temperatures below 283.15 K. Supercooling salt hydrates as latent heat storage materials provide a promising candidate to preheat batteries in an extremely low-temperature environment. This paper selects Na2S2O3⋅5H2O (STP) and CH3COONa⋅3H2O (SAT) with deep supercooling properties and a prismatic LiFeO4 battery as the study objects. A parametric study is carried out to obtain an optimal design. The target preheating temperature of the battery is 293.15 K. After weighting the preheating time, effective utilization, specific energy, and specific power, the configuration that all the sides of the battery are covered with a salt hydrate thickness of 8.0 mm is considered to be the optimal design at 253.15 K. Heating rates are 0.236 K/s and 0.205 K/s for SAT and STP, respectively. However, when the ambient temperature increases to 273.15 K, the effective utilization of SAT and STP decreases by 30.46 % and 34.41 %, respectively. When the discharge rate increases from 1C to 5C, the state of charge (SOC) relative to the cut-off time of SAT and STP reduces from 85.45 % to 56.69 % and from 82.95 % to 57.46 %, respectively. This means a higher effective utilization is provided for a high discharge rate. Due to a higher melting point and higher fusion of heat, SAT shows a faster-preheating rate and higher effective utilization relative to STP, while the difference in average battery temperatures is slight.

Outdoor Thermal Performance of Photovoltaic Devices with Enhanced Daytime Radiative Cooling Glass

The increase in the operating temperature decreases the efficiency and the lifetime of photovoltaic (PV) systems. Radiative cooling effect offers a promising solution to passively reduce the operating temperature of PV modules using the atmospheric window (AW). Glass is a well‐known material used as front cover of PV modules. It presents a fairly good emissivity in the AW although a low‐absorption resonance at 9–10 μm decreases its overall emissivity, hampering its radiative cooling capacity. This effect can be reduced by tailoring the glass surface. Herein, glass samples are microstructured and characterized obtaining a decrease in reflectance and a substantial increase of the emissivity in the AW. Next, the glass samples are laminated with solar cells and installed outdoors without any convection barrier and monitored in open‐circuit configuration for almost half a year. The days are sorted by three meteorological conditions: sunny, partly cloudy, and cloudy days, which correspond to a decreasing availability of the AW. The average temperature difference between two samples is 0.8, 0.7, and 0.1 °C for the sunny, partly cloudy, and cloudy days, respectively. The maximum temperature difference obtained is 2.0 °C. No correlation between temperature difference and wind speed is observed.

Multi‐Functional and Stretchable Thermoelectric Bi2Te3 Fabric for Strain, Pressure, and Temperature‐Sensing

AbstractFiber‐based electronics are essential components for human‐friendly wearable devices due to their flexibility, stretchability, and wearing comfort. Many thermoelectric (TE) fabrics are investigated with diverse materials and manufacturing methods to meet these potential demands. Despite such advancements, applying inorganic TE materials to stretchable platforms remains challenging, constraining their broad adoption in wearable electronics. Herein, a multi‐functional and stretchable bismuth telluride (Bi2Te3) TE fabric is fabricated by in situ reduction to optimize the formation of Bi2Te3 nanoparticles (NPs) inside and outside of cotton fabric. Due to the high durability of Bi2Te3 NP networks, the Bi2Te3 TE fabric exhibits excellent electrical reliability under 10,000 cycles of both stretching and compression. Interestingly, intrinsic negative piezoresistance of Bi2Te3 NPs under lateral strain is found, which is caused by the band gap change. Furthermore, the TE unit achieves a power factor of 25.77 µWm−1K−2 with electrical conductivity of 36.7 Scm−1 and a Seebeck coefficient of −83.79 µVK−1 at room temperature. The Bi2Te3 TE fabric is applied to a system that can detect both normal pressure and temperature difference. Balance weight and a finger put on top of the 3 × 3 Bi2Te3 fabric assembly are differentiated through the sensing system in real time.

Evaluation of the outdoor thermal environment for three typical urban forms in Nanjing, China

Urban form has been proved to be an important factor that significantly influences the microclimate as well as the outdoor thermal comfort at the pedestrian level in urban spaces. Various kinds of urban forms arise from rapid urbanization, accompanying different thermal environments in urban spaces. However, some severe urban climate issues, such as the urban heat island phenomenon, emerge in dense urban areas frequently, especially in large cities with hot and humid climates. In this study, three different archetypes, including the freestanding, scattered, and enclosed types, were selected as the representatives of typical urban forms in the central area of Nanjing city. The outdoor microclimates of these urban forms under typical summer conditions were simulated for calculating the thermal comfort index. The effects of urban form characteristics on the thermal environment were compared and analysed. The results show that the maximum differences in average air temperature, mean radiant temperature, and PET index between these three typical plots could achieve 5.4 °C, 24.2 °C, and 12.4 °C, respectively. Furthermore, the scattered urban form was evaluated to be holding the best outdoor thermal environment in comparison to the others based on a holistic and comprehensive view. Finally, some basic design suggestions based on the results and relevant discussions were recommended for urban design in the cities with similar climate conditions.

Transferring heat accumulated by asphalt pavement from inside to outside through carbon fibers

On the Qinghai-Tibet Plateau, intense solar irradiation will cause serious heat accumulation in asphalt pavement. Downward heat transfer will disturb the permafrost under subgrade, thus leading to a series of subgrade and pavement diseases. This makes construction of asphalt pavement in the permafrost regions of the Qinghai-Tibet Plateau a world-class challenge. This paper proposes for the first time a transversal heat transfer channel in asphalt pavement, which can quickly transfer heat accumulated in pavement to road shoulders. Finite element software ABAQUS was used to simulate the rutting plate with high axial thermal conductivity carbon fibers inserted transversely. Under the constant heat load of 500 W/m2, the heat flux near the carbon fibers showed the characteristic of convergence. The maximum transverse heat flux in the carbon fibers reached 4.97×107W/m2, which was 14 times that in the asphalt mixture. Meanwhile, the maximum vertical heat flux in the carbon fibers reduced to 2.62×106W/m2, which was 12 % less than the asphalt mixture. The effective thermal conductivity of composite specimens with different carbon fiber parameters was studied through control experiments. When the axial thermal conductivity, volume fraction and number of carbon fiber bundles increased to 100 W/m·°C, 10.72 % and 4 bundles respectively, the transverse ETC of composite specimens increased to 4.05 W/m·°C, 7.09 W/m·°C and 16.18 W/m·°C respectively. They were 3.12 times, 5.45 times and 12.45 times of the control group. The radial thermal conductivity of carbon fibers has a significant effect on the vertical ETC. When it decreased to 0.2 W/m·°C, the vertical ETC decreased by 6.15 % compared with the control group. The temperature variation trend of specimens were measured by a laboratory irradiation experiment. The maximum temperature difference between the control group and the experimental group at 0 mm was 5.81 °C, and the average temperature difference within 2 h was 5.14 °C. The maximum temperature difference at 50 mm was 3.84 °C and the average temperature difference within 2 h was 3.24 °C. The results showed that the transverse heat transfer channel can reduce downward heat transfer. The application of the channels will enhance transverse heat release and relieve heat accumulation of asphalt pavement. This can create a low temperature state for pavement structure and has a positive effect on maintaining the stability of the permafrost regions on the Qinghai-Tibet Plateau.

Study on the temperature field in the cutting zone for machining monocrystalline silicon wafer using free abrasive multi-wire saw

With increasing applications of integrated circuits, the requirements for the quality of the corresponding substrate silicon wafers have become more stringent. Slicing is a key step in the manufacturing of silicon wafers. At present, free-abrasive multi-wire saw (MWS) technology is commonly employed for substrate silicon wafer processing. However, the actual temperature field in the cutting zone is unclear because of the narrow cutting zone in multi-wire sawing. Although a simulation method was adopted in this study, the distribution of the slurry in the cutting zone remains ambiguous, causing a large difference between the simulation results. The temperature field is an important cause of warpage, which significantly affects wafer quality. In this study, an experiment and simulation of the temperature field in the cutting zone of a MWS of monocrystalline silicon with free abrasives were performed. First, an experiment was designed to measure the temperatures at different positions in the cutting zone. Then, based on the experimental data of the fluid pressure distribution and the temperature field in the cutting zone, after obtaining the heat source model, a simulation analysis was conducted, and the results are consistent with the experimental results. Finally, based on the heat flux model, the temperature field distribution in the cutting zone under different cutting conditions was simulated and analyzed. Temperatures of 36.7, 39.4, 40.7, and 42.8 °C were obtained at 22.5, 62.5, 137.5, and 177.5 mm, respectively, from the slurry entrance in the cutting zone. According to the heat source model based on the pressure distribution data of slurry in the cutting zone, the temperature values obtained via simulation at 22.5, 62.5, 137.5, and 177.5 mm from the slurry inlet were 35.4, 37.4, 41.5, and 43.1 °C, respectively. The maximum temperature difference is 1.8K°C, and the average temperature difference is 0.2K°C. Thus, the validity of the heat source model was verified. Further, based on the heat source model, the maximum temperature for cutting a 300-mm monocrystalline silicon wafer was predicted as 48.4 °C. Moreover, the wire speed was found to greatly influence the maximum temperature in the cutting zone. Tension also affects the temperature of the cutting zone, but to a lesser extent than the wire speed.

Optimization of the Thermal Environment of Large-Scale Open Space with Subzone-Based Temperature Setting Using BEM and CFD Coupling Simulation

A cruise ship, which has large-scale open spaces, has an uneven cabin thermal environment in the cruise public space, leading to overcooling or poor cooling issues. Therefore, optimizing the thermal environment of public spaces during a cruise should be the priority. According to the space functions of the cruise ship, the large public space is divided into three subzones: the entertainment area (Subzone I), the round-table dining area (Subzone II), and the square-table dining area (Subzone III). To create a uniform, stable, and comfortable thermal environment, this study proposes a subzone-based temperature setting approach to independently adjust the thermal environment of each subzone. Coupling simulation of building energy modeling (BEM) and computational fluid dynamics (CFD) was adopted in this study to determine proper temperature setpoints of the subzones under different occupancy rates. The results indicate that, compared with a single-temperature setpoint for the entire public space, the subzone-based temperature setpoints could achieve a uniform thermal environment. The average temperature difference among the three subzones was 0.68 °C. Moreover, the airflow between two adjacent subzones considerably affected the BEM results of energy consumption of the air-conditioning system.