Numerical simulation of heat transfer and flow of cooling air in triangular wavy fin channels

Numerical computation models of air cooling heat transfer and flow behaviors in triangular wavy fin channels(TWFC) were established with structural parameters of fins considered.The air side properties of heat transfer coefficient and pressure drop are displayed with variable structural parameters of fins and inlet velocities of cooling air.Within the range of simulation,TWFC has the best comprehensive performance when inlet velocity vin=4-10 m/s.Compared with those of straight fins,the simulation results reveal that the triangular wavy fin channels are of higher heat transfer performances especially with the fin structural parameters of fin-height Fh=9.0 mm,fin-pitch Fp=2.5-3.0 mm,fin-wavelength λ=14.0-17.5 mm and fin-wave-amplitude A=1.0-1.2 mm.The correlations of both heat transfer factor and friction factor are presented,and the deviations from the experimental measurements are within 20%.

Field experimental study on the cooling effect of mine cooling system acquiring cold source from return air

With the increase of mining depth, more and deeper coal mines are limited by heat disaster. The cooling energy in deep mine cooling system comes from mine water inrush or ground cooling tower, but we cannot adopt the two methods because mine water inrush in many old coal mines in China is limited. What is more, the cooling pipelines cannot be put in narrow pit-shaft. To settle the problem above, according to the characteristics of Zhangxiaolou Coal Mine, this paper adopts the deep mine return air as the cooling energy for deep mine cooling system. In addition, we carried out cite test to extract cold energy from return air. Through monitoring the water quantity, water temperature of cooling system and air temperature, we got the thermodynamic equilibrium parameters during the cooling energy acquisition analysis and the effect of cooling system that the temperature and humidity on working face are respectively reduced to 8-12 ℃ and 8-15% through cooling. This research offers experimental reference for deep mine cooling which lacks cooling energy.

Analysis of Cooling Characteristics in Datacenter Using Outdoor Air Cooling

Advancement of the information society has proceeded with the development of information and communication technology, and a demand on a data center has increased. In such a situation, the number of servers is increasing in a data center. Thus, the heat density in a data center is much higher than that of usual offices. And typically, almost 40% of the total power consumption is used for cooling servers in a data center. Thus, cooling effectiveness is one of the most important factors in evaluating the value of the data center. The data center taken up in this paper is located in Ishikari, where is a cold district in Japan. Using the cool outdoor air for cooling servers helps us to cut the power consumption for cooling. This paper first assesses the efficiency of Ishikari data center measuring the temperature of seven parts in a building where the cooling air flowing. Second, this paper describes the most efficient method for the operation and estimates 1.11 of PUE （power usage effectiveness）.

Forced Compressed Air Cooling System for a 300 MW Steam Turbine in Waigaoqiao Power Plant

The 300 MW steam turbine installed in Waigaoqiao Power Plant with combined HPIP cylinders of double casing structure is a product of the Shanghai Turbine Works utilizing licensed technology. It has a large heat storage capacity and good thermal insulation, so the metal temperature of first stage of HP cylinder (FSMTI) may reach 400-450℃ after shut down and it takes 7-8 days to cool to 150℃ by natural cooling, Now with a forced cooling system the cooling time may be reduced to 40 hours, so that the turbine may be opened for repair work in about 5-6 days. The cooling system for #2 unit and test procedure are briefly described below.

On the Method of Air Jet Cooling in Green Manufacturing

Green cooling is an important technology in green manufacturing. In the way of jetting, cooling airflo-w in used in the experiments of metal material cutting, by comparison of the changes of some technological factors, such as cutting heat, surface finish, in the process of jet cooling, pour cooling and natural cooling, we can draiv the conclusion that air jet cooling has a better cooling effect and green function. It can be 'widely used in both traditional and automatic green manufacturing.

Effect of cooling conditions on corrosion resistance of friction stir welded 2219-T62 aluminum alloy thick plate joint

Friction stir welding (FSW) with water cooling and air cooling was used to weld 2219-T62 aluminum alloy joints with a thickness of 20 mm. The effect of cooling conditions on the corrosion resistance of joints in 3.5% NaCl solution was investigated using the open circuit potential (OCP), the potentiodynamic polarization, and the corrosion morphology after immersing for different time. And the precipitates distribution was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the weld nugget zone (WNZ) owning positive potential, lower corrosion current density and fine and uniform precipitates, is much more difficult to corrode than the heat affected zone (HAZ) and the base metal (BM). Compared with air-cooled joint, the water-cooled joint has better corrosion resistance. In addition, the results of microstructure observation show that the potential, distribution and size of second phase particles determine the corrosion resistance of FSW AA2219 alloy joints in chlorine-contained solution.

Cooling System Design and Thermal Analysis of Modular Stator Hybrid Excitation Synchronous Motor

Hybrid excitation synchronous motor has the advantages of uniform and adjustable electromagnetic field, wide speed range and high power density. It has broad application prospects in new energy electric vehicles, wind power generation and other fields. This paper introduces the basic structure of hybrid excitation motor with modular stator, and analyzes the operation principle of hybrid excitation motor. The cooling structure of the water-cooled plate is designed, and the effects of the thickness of the water-cooled plate and the number of water channels in the water-cooled plate on the heat dissipation capacity of the water-cooled plate are analyzed by theoretical and computational fluid dynamics methods. The effects of different water cooling plate structures on water velocity, pressure drop, water pump power consumption and heat dissipation capacity were compared and analyzed. The influence of different inlet flow velocity on the maximum temperature rise of each part of the motor is analyzed, and the temperature of each part of the motor under the optimal water flow is analyzed. The influence of the traditional spiral water jacket cooling structure and the water-cooled plate cooling structure on the maximum temperature rise of the motor components is compared and analyzed. The results show that the water-cooled plate cooling structure is more suitable for the modular stator motor studied in this paper. Based on the water-cooled plate cooling structure, the air-water composite cooling structure is designed, and the effects of the air-water composite cooling structure and the water-cooled plate cooling structure on the maximum temperature rise of each component of the motor are compared and analyzed. The results show that the maximum temperature rise of each component of the motor is reduced under the air-water composite cooling structure.

The convection cooling system of the Yakutsk permafrost seed repository

Temperature is critical to maintaining seed viability under long-term storage conditions. It has been common practice to use refrigeration systems to maintain required storage temperatures. A seed repository constructed in permafrost in Yakutsk, Russia is the first seed storage facility that relies solely on natural cold. This paper describes the design and performance of the cooling system of the repository. An innovative aspect of the cooling system is that it utilizes the patterns of temperature wave propagation in permafrost. Predicted and measured ground temperatures for the first year of operation are presented and analyzed. Results indicate that convection air cooling systems can be used to control the temperature regime in underground facilities in permafrost.

Water, land, and energy use efficiencies and financial evaluation of air conditioner cooled greenhouses based on field experiments

High temperature and humidity can be controlled in greenhouses by using mechanical refrigeration cooling system such as air conditioner(AC)in warm and humid regions.This study aims to evaluate the techno-financial aspects of the AC-cooled greenhouse as compared to the evaporative cooled(EV-cooled)greenhouse in winter and summer seasons.Two quonset single-span prototype greenhouses were built in the Agriculture Experiment Station of Sultan Qaboos University,Oman,with dimensions of 6.0 m long and 3.0 m wide.The AC-cooled greenhouse was covered by a rockwool insulated polyethylene plastic sheet and light emitting diodes(LED)lights were used as a source of light,while the EV-cooled greenhouse was covered by a transparent polyethylene sheet and sunlight was used as light source.Three cultivars of high-value lettuce were grown for experimentation.To evaluate the technical efficiency of greenhouse performance,we conducted measures on land use efficiency(LUE),water use efficiency(WUE),gross water use efficiency(GWUE)and energy use efficiency(EUE).Financial analysis was conducted to compare the profitability of both greenhouses.The results showed that the LUE in winter were 10.10 and 14.50 kg/m^(2) for the AC-and EV-cooled greenhouses,respectively.However,the values reduced near to 6.80 kg/m^(2) in both greenhouses in summer.The WUE of the AC-cooled greenhouse was higher than that of the EV-cooled greenhouse by 3.8%in winter and 26.8%in summer.The GWUE was used to measure the total yield to the total greenhouse water consumption including irrigation and cooling water;it was higher in the AC-cooled greenhouse than in the EV-cooled greenhouse in both summer and winter seasons by almost 98.0%–99.4%.The EUE in the EV-cooled greenhouse was higher in both seasons.Financial analysis showed that in winter,gross return,net return and benefit-to-cost ratio were better in the EVcooled greenhouse,while in summer,those were higher in the AC-cooled greenhouse.The values of internal rate of return in the AC-and EV-cooled greenhouses were 63.4%and 129.3%,respectively.In both greenhouses,lettuce investment was highly sensitive to changes in price,yield and energy cost.The financial performance of the AC-cooled greenhouse in summer was better than that of the EV-cooled greenhouse and the pattern was opposite in winter.Finally,more studies on the optimum LED light intensity for any particular crop have to be conducted over different growing seasons in order to enhance the yield quantity and quality of crop.

Numerical simulation of HP rotor cooling configuration using parameterized method

This paper implemented cooling configuration design on certain gas turbine HP rotor using parameterized method.It is convenient for complicated gas turbine blade modeling using parameters and also benefit for the geometry modify in later period.Parameterized modeling is the foundation of air cooling turbine blade design method engineering application.Mesh quality can be awarded when generated complicated cooling configuration blade grids,and also the increase of calculation error can arise by many mesh blocks.Film cooling and serpentine passage can effectively enhance the cooling effectiveness and protect blade.

Investigation of convection cooling guide vane with conjugate heat transfer method

This paper studied a certain blade with ten radial cooling holes which employed conjugate heat transfer method. The cooling air entered the cooling channel from the bottom of the blade and went out from the top, it was not ejected into the main flow. This paper used different numerical conditions including different turbulence models,turbulence intensities,thermal conduction coefficients and the influence on fluid property via temperature variation. The temperature distribution and pressure distribution of the blade were compared with experimental data. The results show that the numerical results using different turbulence models are almost identical to experimental data even little deviation occurs at shock wave location. The trends of temperature distribution under different numerical conditions are coincident to experimental data,especially Reynolds stress turbulence model. It can be concluded that anisotropic turbulence models can simulate the transition from laminar to turbulence,and the influence of turbulence intensity on laminar region and transition region is more than that on developed turbulent region.

Numerical Simulation of Thermal Management of Lithium Battery Based on Air Cooled Heat Dissipation

In recent years,due to the rapid increase in the number of vehicles in the world,the traditional vehicles using gasoline or diesel as energy have led to serious air pollution and energy depletion.It is urgent to develop practical clean energy vehicles.The performance of electric vehicle depends on the power battery pack.The working temperature of the battery pack has a great impact on the performance of the battery,so it is necessary to carry out thermal management on the battery pack.Taking a lithium-ion battery as the research object,the temperature field of the battery pack in the charge and discharge state is simulated and analyzed by using CFD simulation software in the way of air cooled heat dissipation,so as to understand the influencing factors of uneven temperature field.At the same time,the development trend of battery temperature can be well predicted through simulation,so as to provide theoretical basis for the design of battery pack.

Effect of cooling media on bead geometry,microstructure,and mechanical properties of wire arc additive manufactured IN718 alloy

This work aims to present and explore thermal management techniques for the wire arc additive manufacturing(WAAM)of IN718 components.Excessive heat can be mitigated via air or water cooling.In this study,the material was deposited under four different heat-input conditions with air or water cooling.In air cooling,the layer is deposited in a normal atmospheric air environment,whereas with water cooling,the material is deposited inside a water tank by varying the water level.To validate the air and water cooling thermal management techniques,IN718 single-pass and multilayer linear walls were deposited using the bidirectional gas metal arc welding based WAAM setup under four different heat input conditions.During the deposition of single layers,the temperature profiles were recorded,and the geometric and microstructural features were explored.For multilayer wall structures,the mechanical properties(hardness,tensile strength,and elongation)were determined and assessed using the corresponding microstructural features explored through scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and electron backscatter diffraction(EBSD)analyses.The microstructure observed through SEM analysis in the building direction was found to be nonhomogenous compared with that in the deposition direction.Moreover,water cooling was found to govern bead characteristics,such as wall width and height.The grain size and anisotropy of the mechanical properties also decreased in the water-cooled case.Hence,water cooling is an economical and efficient method to mitigate excessive heat accumulation in WAAM-deposited IN718.

Effect of cooling pad installation on indoor airflow distribution in a tunnel-ventilated laying-hen house

Extra cooling pads on the sidewalls are needed for larger poultry houses using tunnel ventilation system.Preliminary study showed that the airflow velocity going through different aisles varies greatly when the extra pads are installed at the end of sidewalls,making a“[”-shape air inlet.Combined with field tests,the CFD(computational fluid dynamics)technology was used to study the uniformity of airflow distribution in a tunnel-ventilated laying-hen house.The air distribution was first monitored in a layer house to find the main reason resulting in the variations of airflows in different aisles.Then CFD simulations were carried out with different distances(D=2 m,3 m or 4 m)between the pads on end-wall and the extra pads on side walls.The field test showed that airflow streams from the different groups of cooling pads collided vertically at the house corners,mixed with each other,then flew towards the center of the house.This was the main reason that the wind speed in the middle aisle was much higher than in other aisles,leaving large zones of lower ventilation in the aisles adjacent to the sidewalls.The results of CFD simulations indicated that air distributions could be significantly improved when the extra pieces of pads were moved away for an appropriate distance from the end coolingpads.As far as conventional poultry house with a span of 12 m,the air speeds in different aisles were more uniform when this distance was about 3 m.

Multi-objective optimization of cooling air distribution of grate cooler with different inlet temperatures by using genetic algorithm

The paper discussed a multi-objective optimization model of the cooling air distribution of a grate cooler according to the analogy

Modeling and Optimization of Heat Dissipation Structure of EV Battery Pack

In order to solve the problems of high temperature and inconsistency in the operation of electric vehicle（ EV） battery pack,computational fluid dynamics（ CFD） simulation method is used to simulate and optimize the heat dissipation of battery pack. The heat generation rate at different discharge magnifications is identified by establishing the heat generation model of the battery. In the forced air cooling mode,the Fluent software is used to compare the effects of different inlet and outlet directions,inlet angles,outlet angles,outlet sizes and inlet air speeds on heat dissipation. The simulation results show that the heat dissipation effect of the structure with the inlet and outlet on the same side is better than that on the different sides; the appropriate inlet angle and outlet width can improve the uniformity of temperature field; the increase of the inlet speed can improve the heat dissipation effect significantly. Compared with the steady temperature field of the initial structure,the average temperature after structure optimization is reduced by 4. 8℃ and the temperature difference is reduced by 15. 8℃,so that the battery can work under reasonable temperature and temperature difference.

Forced Convective Air Cooling from Electronic Component Arrays in a Parallel Plate Channel

This paper discusses air forced convection heat transfer from inline protruding elements arranged in eight rows. The streamwise and spanwise spacings between elements were varied using a splitter plate that can be positioned at three different modular configurations. A set of empirical formulas waspresented to correlate the experimental data for the design of air cooling systems. Arrays of components with one odd-size module have been tested also. Experimental results show that blocks near the entrance and behind the odd-size module have improved performance compared with uniform arrangements. Accordingly, temperature sensitive components are suggested to be arranged in these locations.

Creation of Air-Cooled Mn Series Bainitic Steels

The development and mechanical performances of new type air-cooled Mn series bainitic steels including granular bainitic steels, FGBA/BG duplex steels, CFB/M duplex steels, medium carbon bainite/martensite steels, cast bainitic steels invented by the authors are summarized. The novel series of bainitic steels are alloyed with Mn, and several series bainitic duplex microstructures can be easily obtained under the condition of air cooling through unique composition design. The invented idea, the principle of alloying design, the strengthening mechanism, and the evolution of the microstructure of new type air cooled Mn series bainitic steels are presented. Furthermore, the applications in different fields of these Mn series air cooled bainitic steels with different strength level are also introduced. It is suggested that the significance of the development of the air cooled Mn series bainitic steel can be summarized as follows： reducing costs of both raw materials and production; good combination of strength and toughness; self-hardening with high bainitic hardenahility by air cooling from hot working without additional quenching-tempering treatment or quenching procedure; large savings in energy resources; and reduced environmental pollution.

The effects of portable cooling systems on thermal comfort and work performance in a hot environment

There are some special spaces in which there is no air conditioning or the people are in move,thus exposing people to a hot environment.In this study,portable cooling systems were proposed and their effects on thermal comfort and work performance were investigated at an air temperature of 32°C.Four conditions were established:cool air towards breathing zone(A),chest and back cooling(B)#combined cooling(C)and no cooling(D).Twenty-eight subjects were exposed to the four conditions in a counterbalanced order.During each exposure they performed tasks and made subjective assessments,while multiple physiological parameters were measured.Compared with no cooling(D),cool air towards breathing zone(A)and chest and back cooling(B)improved work performance by 17.5%and 19.25%,respectively,while decreased the subjects'thermal sensation,skin temperature,and heart rate.When the two cooling systems were combined(C),larger improvements in thermal comfort and work performance were achieved than no cooling(D);the mean thermal sensation rating decreased from 2.4 to 0.7;work performance increased by up to 33%,and physiological parameters including skin temperature,pulse,heart rate and salivary alpha-amylase significantly decreased.The present results suggest that the proposed portable cooling systems could maintain thermal comfort and work performance in a hot environment,while potentially improve air quality for some special spaces.

Comparative Study of Convective Heat Transfer Performance of Steam and Air Flow in Rib Roughened Channels

A comparative experimental study of heat transfer characteristics of steam and air flow in rectangular channels roughened with parallel ribs was conducted by using an infrared camera. Effects of Reynolds numbers and rib angles on the steam and air convective heat transfer have been obtained and compared with each other for the Reynolds number from about 4,000 to 15,000. For all the ribbed channels the rib pitch to height ratio(p/e) is 10, and the rib height to the channel hydraulic diameter ratio is 0.078, while the rib angles are varied from 90° to 45°.Based on experimental results, it can be found that, even though the heat transfer distributions of steam and air flow in the ribbed channels are similar to each other, the steam flow can obtain higher convective heat transfer enhancement capability, and the heat transfer enhancement of both the steam and air becomes greater with the rib angle deceasing from 90° to 45°. At Reynolds number of about 12,000, the area-averaged Nusselt numbers of the steam flow is about 13.9%, 14.2%, 19.9% and 23.9% higher than those of the air flow for the rib angles of 90°,75°, 60° and 45° respectively. With the experimental results the correlations for Nusselt number in terms of Reynolds number and rib angle for the steam and air flow in the ribbed channels were developed respectively.