Hot Outlet Research Articles

Numerical investigation of conical vortex tube with combined axial-tangential injection

The present work is a numerical investigation of the combined axial- tangential injection effect on conical Ranque-Hilsch vortex tube performances. An orifice in the center of the conical control valve is created, allowing the injection of compressed air axially. The computational fluid dynamics CFD commercial software ANSYS CFX has been used for the present investigation, and the mean field is determined using the Reynolds-averaged Navier-Stokes equations RANS method. The main results show that the conical configuration causes a considerable drop in temperature of the cold and hot outlet flows up to 3 °C on average and a significant increase in the cold mass flow of 25% compared to the cylindrical vortex tube with axial injection.

Mineralogy and geochemistry of rare earth elements in the Moyil Valley alteration zones, Meshkinshahr (northwest Iran)

Abstract Sabalan Mountain (northwest Iran) witnessed intense volcanic activity during the Cenozoic (Plio-Pleistocene). The result of this manifests itself in the conical geometry of the Sabalan stratovolcano and ahigh hydrothermal gradient around it, which can be detected by geological phenomena such as hot springs, smoke gases and steam outlet pores. The high hydrothermal slope and upward migration of hot water in this area have caused extensive alteration zones in the host rocks. A mineralogical study of alteration zones in thewells drilled in the Moyil Valley to the northwest of Sabalan Mountain has revealed the presence of phyllic, argillic, calcitic and propylitic alterations in volcanic rocks (trachyandesite) and alteration phyllic and propylitic ones in monzonite rocks. In chondrite-normalised rare-earth-element diagrams, trachyandesite rocks exhibit an HREEs enrichment when compared to MREEs and LREEs in propylitic and calcitic alteration zones. This result can be explained by the acidic nature of hydrothermal fluids containing complex ions such as (SO-2, Cl-). The (La/Yb)cn, (La/Sm)cn and (Tb/Yb)cn ratios for argillic, phyllic, propylitic and calcitic alteration zones have revealed that they are higher in fresh rocks compared to altered rocks, suggesting the enrichment of HREEs in comparison to LREEs and MREEs. The anomalies of Eu do not change remarkably in the argillic and propylitic alteration zones of trachyandesite rocks; apparently, alteration hadno effect on them. Such behaviour reflects the presence of gold cations in Eu+3 formed at temperatures below 250°C. Eu anomalies increased in propylitic alteration zones in monzonite rocks and calciticand phyllic alteration zones in trachyandesiterocks.

Empirical and CFD analysis of silica nanofluid using a double pipe heat exchanger

The heat exchangers are widely used in the industrial processes to either heat or cool the working fluids. They prevent the utilization of an external heat source, which highly reduces the cost of production. The Heat exchangers having high thermal conductivity are required to meet the expanding industrial needs. This study targets the enhancement of thermal energy transfer by the usage of nanofluid instead of the conventional fluid such as water, in the concentric tube heat exchanger. The nanofluid was prepared by the usage of silica nanoparticles, having distilled water as the primary fluid. The silica nanoparticles synthesized by green synthesis method are conformed by X-ray Diffraction, zeta potential, FESEM techniques. The hot liquid in the heat exchanger remains unchanged while, the conventional fluid is replaced by the prepared silica nanofluid as cold fluid. In this research, a double pipe heat exchanger is modeled and meshed using ANSYS Fluent 14.5. The heat transmission attributes of silica nanofluid in the equipment are analyzed with the help of fluent software. The amount of nanofluid used for the entire experiment was about 5 l and in order to get a 0.05% volume concentration approximately 7 g of nanoparticles were used. The results of Computational Fluid Dynamic (CFD) analysis and the experimentation were compared and justified. In CFD analysis the cold and hot outlet temperatures are 313.18 and 354.03 K respectively, while the experimental results are 322 and 346 K respectively. An improvement of 10 °C was found in the cooling of the heat exchanger upon the usage of silica nanofluid. The outcome of the present research work, reveals that the addition of nanoparticles to the host fluid leads to significant improvement of thermal properties.

Optimization of Ranque–Hilsch vortex tube performances via Taguchi method

In this study, by considering the changes in inlet pressures, connection nozzle materials and the number of orifices, the performances of Ranque–Hilsch vortex tubes (RHVTs) were modelled by multiple linear regression method at which carbon dioxide (CO2) was used as compressed fluid, and optimum operating conditions were tried to be determined by Taguchi method. In the experiment, counterflow RHVTs having O10 mm inner diameter and 100 mm body length were used, hot fluid outlet of which was left completely open. In the tests designed using Taguchi L16 mix type (8 × 1 2 × 3) orthogonal array, 8 different inlet pressures (200, 250, 300, 350, 400, 450, 500 and 550 kPa), 2 different types of connections (parallel and series), 2 different types of nozzle materials (brass and polyamide) and 2 different numbers of orifices (4 and 6) were chosen as control factors and levels. Maximum temperature gradient (∆T) was determined as quality characteristics, and RHVT’s performance tests were done. In order to determine the effect rates of selected control factors on quality characteristics (∆T), analysis of variance (ANOVA) was applied within 95% confidence level. According to the statistical results, it was determined that ΔT values were mostly influenced by the inlet pressure and this was followed by connection type, number of orifices and nozzle material. With the confirmation test performed, reliability of the optimization was tested and confirmed.

Evaluation and Optimization of O2 Used Ranque-Hilsch Vortex Tube Performance

ABSTRACT Ranque-Hilsch Vortex Tube (RHVT) is a mechanic system which can make heating and cooling by using basic heat transfer laws with a compressed fluid. Environmental friendly RHVT is widely used in cooling systems in medicine, electronics, and computer sectors, particularly in the food sector. In this study, the performances of parallel RHVTs in which oxygen (O2) gas is used were reviewed considering different inlet pressures, nozzle materials and orifice numbers. Test results were modeled by multiple linear regression method and regression equation was derived. Besides, Signal/Noise (S/N) ratios of the designed test results were calculated using Taguchi L16 mix type (4 × 2 2 × 1) orthogonal sequence, and optimum conditions were determined. Throughout the test, hot fluid outlet valve of the counter flow RHVTs having Ø10 mm inner diameter and 100 mm body length was completely left open. As control factors and levels, four different inlet pressures (200, 350, 500, and 650 kPa), four different number of orifices (three, four, five, and six), and two different nozzle materials (brass and polyamide) were selected. For quality characteristics, maximum temperature gradient (∆T) was determined. In order to determine the effect rates of the control factors on quality characteristics (∆T), variance analysis (ANOVA) was applied to test results at 95% confidence level. According to statistical results, it was determined that the response rates of ΔT values from the control factors were determined as inlet pressure, the number of orifices and nozzle material, respectively. Validity of the optimization was checked with confirmation tests, and the optimization proved to be used in evaluation of RHVT performances.

Numerical Investigation of the Thermo-Hydraulic Characteristics for Annular Vortex Tube: A Comparison With Ranque–Hilsch Vortex Tube

Abstract In this work, a new configuration of the vortex tubes (VTs), called annular VTs, is proposed to improve the temperature separation performance. In the proposed configuration, a compartment has been added on the top of the tube wall that the separated hot outlet is repassed inside it over the hot tube. An axisymmetric swirl model of the Ranque–Hilsch (RH) and annual VTs is numerically simulated, and the thermo-hydraulic characteristics of them are compared for cold mass fractions ranging 0.2–0.8. The results illustrated that a small secondary circulation is created near the cold outlet of the RHVT that is not observed in the annular model. This secondary circulation is a destructive mechanism in VTs that results in more mixing and higher temperature in the cold outlet section. Analyzing the results indicates that using annular VT causes up to 12.51% increment of the hot outlet temperature compared to the RHVT model (which occurs at a mass fraction of 0.23). Also, up to 9.23% reduction of the cold outlet temperature is occurred (which occurs at a mass fraction of 0.37). These explanations prove the improvement of the annular VT compared to that of the conventional VTs.

RETRACTED ARTICLE: Study on various control strategies of plate type heat exchanger for non-Newtonian fluids

Heat exchangers are expedients used to transfer of heat energy from one medium to other while preventing the two from mixing. Heat exchangers are hired in a selection of domestic, commercial, and industrial applications, such as air conditioning, power production, refrigeration, process industry, and manufacturing industry. A larger variation in the temperature affects property of non-Newtonian fluids, thus affects the uniform heat transfer process. This paper is primarily to deal the response analysis of different controllers that is regulating the outlet temperature of fluid inside the PHE is proposed. The cold fluid flow is highly influenced on the hot water temperature, the research work mainly focuses on controlling cold fluid flow. In order to attain the precise model of the system, a mathematical model by first principle methods and process history based methods were used. A PI, PID and Model Predictive Controller (MPC) are known for its better control action of the system. The controller’s performance analysed such as PI, PID and MPC controller to adjust the temperature of hot fluid outlet to a required setpoint. Performance criteria analysis value for various controllers are PI, PID and MPC. It is understood that MPC controller results lower value of performance measures compared to other controllers, this implies that it could track the setpoint by rejecting the external disturbances with less settling time and moderate oscillation. The transient performance and the error criteria of the controllers are investigated and the best controller to regulate the temperature is found out. It is found out that the MPC controller outperforms PI and PID controller from the results of simulation.

A Numerical Approach to Study the Steady State Heat Transfer Characteristics of an Annular Porous Heat Exchanger

Heat exchangers are one of the most heavily studied devices and extensive work has been performed over the years to increase their effectiveness. The present work investigates the heat transfer characteristics of an APHE (annular porous heat exchanger) in terms of different parameters. A modified design for the APHE is proposed, which resembles a conventional double pipe heat exchanger, with the annular portion of the outer pipe filled with a specific type of porous medium in order to intensify the heat transfer process. Commercial CFD package ANSYS Fluent has been utilized to investigate the performance of the proposed design numerically. Introduction of porous medium induces an increase in pressure loss which is undesirable; hence, a trade-off is present between hydrodynamic and thermodynamic performance. In the present work different inlet parameters have been modified such as different values of porosity (70% to 90%), different inlet velocities of hot fluid (1 m/s to 9 m/s), different inlet velocities of cold fluid (5 mm/s to 25 mm/s), and different inlet temperature of hot fluid (400 K to 480K), and their effects on the outlet parameters have been studied. The change in heat transfer has been presented quantitatively along with other significant parameters such as mass flow rate, pressure drop and hot gas outlet temperature. These results have been compared with the values for conventional heat exchangers in order to establish the effectiveness of APHE.

Developing an integrated structure for simultaneous generation of power and liquid CO2 using parabolic solar collectors, solid oxide fuel cell, and post-combustion CO2 separation unit

With decreasing underground resources and increasing carbon dioxide levels, human beings are forced to use renewable energies and new methods for power generation and CO2 elimination. In this paper, an integrated structure is developed for generating power and liquefying CO2 using parabolic solar collectors, solid oxide fuel cell, CO2 power generation cycle, separation unit, and CO2 liquefaction. This integrated structure generates 346.5 kW power, 82.2 kW heat and 158.7 kg/h liquid CO2. The hot flow outlet of the solid oxide fuel cell is used to supply the CO2 power generation cycle and enter the post-combustion CO2 separation unit. The parabolic solar collectors with climatic conditions in Tehran, Iran, are used to supply the heat of integrated structure and the ammonia-water absorption refrigeration cycle is employed to supply cooling for CO2 liquefaction. This integrated structure has a total thermal energy efficiency of 40.81% and SOFC electrical efficiency of 61.71%. Economic analysis is illustrated that the period of return and the prime cost of product are 6.26 years and 0.0855 US$/kWh, respectively. To simulate the developed integrated structure, the TRNSYS, HYSYS, and MATLAB software are used. Then, using the sensitivity analysis, the effects of fuel utilization coefficient, inlet flow temperature on gas turbine and fuel cell temperature on the performance of the integrated structure are investigated.

Optimization design with an advanced genetic algorithm for a compact air-air heat exchanger applied in aero engine

This work presents an optimal design method for a compact air-air serpentine tube heat exchanger (STHE), which is applied as the core component of the bearing sealing cooling system in the aero engine. A new optimization tool, coupling with the Logarithmic Mean Temperature Difference (LMTD) method and an advanced genetic algorithm (AGA) using Gray code, is proposed to optimize the STHE with unknown outlet parameters under variable working conditions. Under the given performance and structural constraints, six optimization design variables, including tube outer diameter, the transverse tube pitch, the longitudinal tube pitch, the transverse tube rows, the height and the number of elbows, are selected to obtain the maximum heat transfer capability KA per total weight. The optimization results show that, by using AGA, the target parameter distribution is narrowed from 88.31~93.86 kW/(K•kg) to 91.90~93.92 kW/(K•kg), and the proportion of the optimal solutions higher than 93 kW/(K•kg) increases from 22.62% to 94.32%. The optimization also improves the heat transfer capability KA per total weight to 93.92 kW/(K•kg), comparing with the original value of 70.08 kW/(K•kg). As the key limiting factors, the hot side maximum outlet temperature and pressure drop in the optimized STHE do not appear at the same operation mode and both of them are quite close to the given limits. It well demonstrates the validity and applicability of the proposed optimization design method using under multiple restrictions and conditions.

A Hot Water Split-Flow Dual-Pressure Strategy to Improve System Performance for Organic Rankine Cycle

The organic Rankine cycle (ORC) is widely used to recover industrial waste heat. For an ORC system using industrial waste hot water as a heat source, a novel hot water split-flow dual-pressure organic Rankine cycle (SFD-ORC) system is developed to improve the performance of the ORC. The maximum net power output was selected to compare three ORC systems, including basic ORC (B-ORC), conventional dual-pressure ORC (CD-ORC) and SFD-ORC. A genetic algorithm (GA) was used to optimize the parameters to search the maximum net power output of ORCs. The maximum net output power was taken as the standard of performance evaluation. The results show that, under the same hot water inlet temperature condition, the optimal hot water outlet temperature of B-ORC is much higher than that of CD-ORC and SFD-ORC, which indicates that less thermal energy could be utilized to convert to power in B-ORC. The optimal hot water temperature at the outlet of evaporator 1 in SFD-ORC is higher than that in CD-ORC, which means SFD-ORC could make more efficient use of the high-grade thermal energy of hot water. The SFD-ORC could obtain the highest net output power under the optimal parameter conditions, followed by the CD-ORC system, while the B-ORC has the lowest net output power. Moreover, with the increase in the hot water inlet temperature, the advantage of SFD-ORC becomes increasingly obvious. When the hot water inlet temperature is 90 °C, the net output power of SFD-ORC at is 6.22% higher than that of CD-ORC. The net output power of SFD-ORC at 130 °C increases to 9.7% higher than that of CD-ORC. The SFD-ORC presents better system performance and has great engineering application potential.

An Experimental Transient Response of a Heat Exchanger with the Al2O3/Water Nanofluid Mass Flow and Temperature Step Variations

Experimental study on using nanofluid in a cross-flow minichannel heat exchanger (MICHX) to investigate its transient behavior was completed. Step changes of temperature and flow rate in the hot liquid were applied and the dynamic performance of the heat exchanger was analyzed. Results of nanofluid were compared to water and demonstrate an enhancement of 19% in heat transfer when using 2.5 wt% concentration Al2O3/water nanofluid. Parameters such as the transient effectiveness, heat balance, response time, and outlet temperatures of both liquid and air were also studied. The empirical correlations are developed for the temperature and mass flow step variations in a MICHX to predict the hot fluid outlet temperature in the dimensionless parameters. Nanofluid showed shorter response time for temperature and mass flow step changes compared to water. The outcome of this work is of interest to designers for process control, thermal testing, characterization, and performance enhancement of compact heat exchangers.

Pressure drop and heat transfer performance of microchannel heat exchanger with different reentrant cavities

The shape of the reentrant cavities has a great effect on the pressure drop and heat transfer performance of microchannel heat exchanger (MHE). In present study, MHEs with three reentrant cavity, i.e. circular, trapezoidal, and rectangular, were designed and manufactured. The influence of the cavity shape on the pressure drop performance, heat transfer performance and comprehensive performance of the MHEs were investigated. The pressure drop and Darcy friction coefficients were largest for the rectangular reentrant cavities, indicating that it exhibited the best pressure drop performance. At the same flow rate, the MHE with circular reentrant cavities had the lowest hot water outlet temperature and the MHE with rectangular reentrant cavities had the highest temperature, whereas the results were the opposite for the cold water outlet temperature. The Nusselt number was largest for the circular reentrant cavities. This indicates that the MHE with circular reentrant cavities had the best heat performance. Finally, the comprehensive performance index η was put forward. And the result found that the MHE with circular reentrant cavities had the highest comprehensive performance.

Effect of Modified Flow Schemes of Heat Transfer Fluid on the Performance of a Solar Absorption–Cooling System for an Educational Building in Pakistan

Performance of solar absorption cooling systems (SACS) is the focus of contemporary studies for decreasing the electrical energy consumption of buildings as the conventional cooling system of buildings is the main consumer of electrical energy during the summer season in hot–humid climates. In this study, the performance analysis of SACS by manipulating different flow schemes to the heat transfer fluid between different components of the system was performed. TRNSYS model of SACS in an education building located at the city of Peshawar (34.00 N, 71.54 E), Pakistan to encounter the peak cooling load of 108 kW (during operating hours of the building i.e., 09 a.m. to 05 p.m.) is developed and all possible flow schemes of heat transfer fluid between the system’s components were compared. In Scheme-1 (S-1), a conventional flow pattern is used in which the hot water exiting from the chiller unit flows directly toward the stratified thermal storage unit. In Scheme-2 (S-2), the modified flow pattern of hot water exiting from the chiller unit will divert towards the auxiliary unit, if its temperature exceeds the temperature at the hot side outlet of the tank. Another modified flow pattern is Scheme-3 (S-3) in which the hot water leaving the chiller to keep diverting towards the auxiliary unit unless the outlet temperature from the hotter side of the tank would reach the minimum driving temperature (109 °C) of the chiller’s operation. Simulations in TRNSYS evaluates the SACS’s performance of all the schemes (conventional and modified) for the whole summer season and for each month. In general, S-3 with evacuated tube solar collector results in better primary energy saving with the smallest collector area per kilowatt for achieving 50% primary energy saving for the whole summer season.

Experimental study on effect of operating parameters on performance of serially cascaded wastewater source heat pump

In order to maximize the recovery of heat energy from shower greywater, improve the operation stability of the wastewater source heat pumps and reduce the complexity of the system, a serially cascaded wastewater source heat pumps (SCWSHP) with large temperature difference was proposed. In this paper, an experimental system for testing the heating performance of the SCWSHP was built. The heating performance of the SCWSHP was analyzed under various operating conditions. And the operating conditions of the SCWSHP were discussed in order to realize that the amount of hot water heated by the SCWSHP is greater than the amount of greywater recovered. The results showed that when the greywater inlet temperature and out temperature are 30 °C and 6 °C, respectively, the outlet temperature of hot water can be heated to 50 °C if tc,i is 15 °C. But the maximum outlet temperature of hot water can only reach 41 °C if tc,i is 9 °C in order to guarantee the operation demand of the system. For the lower tap water inlet temperature, the shower greywater inlet temperature must be increased in order that the hot water outlet temperature can reach 45 °C. If tc,i is 6 °C, the greywater inlet temperature should be improved to 35 °C. As long as the outlet temperature of hot water meets the operation requirements, the hot water flow rate should be increased as much as possible, but the flow rate of greywater should be consistent with that of hot water. The results can provide key references for design and operation of the SCWSHP system.

Thermal–electrical–structural performances of hot heat exchanger with different internal fins of thermoelectric generator for low power generation application

In this study, an electro-thermo-structural coupled numerical analysis is conducted to evaluate the thermal, electrical, and structural performances of a thermoelectric generator system. The hot heat exchangers with six different internal fin structures are compared in terms of temperature distribution, pressure drop, net power output, overall efficiency, and stress using the coupled numerical approach. Experiments are conducted on the heat exchanger with straight fins to validate the accuracy and reliability of the proposed coupled analysis. The hot gas outlet temperature, coolant outlet temperature, power output, and stress predicted using the coupled approach are validated within errors of 1.5, 6, 3, and 5.45%, respectively. Among the proposed heat exchanger designs, the heat exchanger with inclined fins and that with the combination of inclined and perpendicular fins exhibit higher net power outputs and overall efficiencies. The heat exchanger with the inclined fins and that with the combined fins exhibit overall efficiencies of 1.81 and 1.88% and net power outputs higher by 29 and 35%, respectively, than those of the heat exchanger with straight fins at the hot gas temperature of 600 °C. At the hot gas temperature 600 °C, the maximum stresses induced in the heat exchanger with the inclined fins and that with the combined fins are approximately 25.87 and 26.53 MPa, respectively, which are lower than the maximum allowable stress of 70 MPa.

Planning and Public Health professionals' experiences of using the planning system to regulate hot food takeaway outlets in England: A qualitative study.

Takeaway food outlets offer limited seating and sell hot food to be consumed away from their premises. They typically serve energy-dense, nutrient-poor food. National planning guidelines in England offer the potential for local planning policies to promote healthier food environments through regulation of takeaway food outlets. Around half of English local government areas use this approach, but little is known about the process of adoption. We aimed to explore experiences and perceived success of planning policy adoption. In 2018 we recruited Planning and Public Health professionals from 16 local government areas in England and completed 26 telephone interviews. We analysed data with a thematic analysis approach. Participants felt that planning policy adoption was appropriate and can successfully regulate takeaway food outlets with the intention to improve health. They identified several facilitators and barriers towards adoption. Facilitators included internal co-operation between Planning and Public Health departments, and precedent for planning policy adoption set elsewhere. Barriers included "nanny-state" criticism, and difficulty demonstrating planning policy effectiveness. These could be considered in future guidelines to support widespread planning policy adoption.

A Unit for Local Cryotherapy Based on the Ranque–Hilsch Vortex Effect

The possibility of using the vortex effect in a unit for local cryotherapy is demonstrated. The block diagram of the developed unit and the results of pilot tests are presented. It is shown that the technological efficiency of the Ranque–Hilsch vortex tube used in the unit can be increased by forced cooling of the tube housing or solely of its hot flow outlet.

Pressure Drop and Heat Transfer Performance of Microchannel Heat Exchanger With Circular Reentrant Cavities and Ribs

Abstract The rib arrangement has an important influence on the pressure drop and heat transfer performance of a microchannel heat exchanger (MHE) with circular reentrant cavities and ribs. In this study, four kinds of MHEs with circular reentrant cavity and ribs were designed, namely, circular reentrant cavities (circular), circular reentrant cavities and single-sided ribs (circular—single), circular reentrant cavities and odd-symmetric ribs (circular—odd), and circular reentrant cavities and double symmetric ribs (circular—double). The effect of the rib arrangement on the pressure drop and heat transfer performance of MHEs was numerically investigated by ansysfluent 15.0. The experimental platform was then designed and built for the subsequent experimental verification. The results showed that the pressure drop between the inlet and outlet of the MHE with circular reentrant cavities and ribs increased as the inlet flow increased. At the same inlet flowrate, the pressure drop between the inlet and outlet of the MHEs was largest for the circular reentrant cavities and double symmetric ribs, followed by the circular reentrant cavities and odd-symmetric ribs, circular reentrant cavities and single-sided ribs, and the circular reentrant cavities. The presence of the rib structure increased the inlet and outlet pressure drop of the MHE. The MHE with circular reentrant cavities and double symmetric ribs had the largest inlet and outlet pressure drop, followed by that with circular reentrant cavities and odd-symmetric ribs, that with circular reentrant cavities and single-sided ribs, and that with circular reentrant cavities, indicating that the latter exhibited the best pressure drop performance. At the same inlet flowrate, the MHE with circular reentrant cavities had the highest hot water outlet temperature and the MHE with circular reentrant cavities and double symmetric ribs had the lowest temperature, whereas the results were the opposite for the cold-water outlet temperature. This indicates that the heat transfer performance was best for the MHE with circular reentrant cavities and double symmetric ribs, followed by that with circular reentrant cavities and odd-symmetric ribs and that with circular reentrant cavities and single-sided ribs.

Numerical simulation of temperature heterogeneity inside the AP1000 upper plenum and hot leg

The high-fidelity simulation for nuclear reactor has attracted more attentions recent years and it could provide much deeper understanding of the thermal hydraulic features in the reactor pressure vessel, promoting the reactor design optimization or operation guidelines making. The temperature heterogeneity in hot legs induces the deviation of reactor core power level estimation. In order to investigate the lateral flow at the reactor upper plenum and temperature heterogeneity in the hot legs of AP1000, a multi-scale coupling method was proposed with the computational fluid dynamics (CFD) and sub-channel analysis in this paper. The sub-channel analysis code, COBRA-EN, was used to calculate the coolant temperature distribution at core outlet and provide the accurate boundary conditions for CFD simulation. A detailed CFD analysis model from the core outlet to hot leg outlet was established. The main internal components including control guide tubes with eight large opening windows on it and support columns were kept, while other little components including control rod assemblies were omitted to decrease the total mesh quantity. Compared with the temperature field at core outlet, the maximum temperature difference at the entrance of the hot leg drops 10.0 K after the strongly mixing in the upper plenum. The hotter coolant from central fuel assemblies remains at the upper part of the hot leg, while the cooler coolant from peripheral fuel assemblies stays in the lower part of the hot leg. The temperature heterogeneity and its evolvement along the hot leg were analyzed.