Cooling Water Velocity Research Articles

Design of experimental section of a water tunnel for simulation of heat dissipation condition of seawater-activated battery

Abstract A water tunnel is a crucial experimental apparatus in hydrodynamic research, as the traditional water tunnel has drawbacks such as a small cross-sectional area of the test section and higher costs, which makes it difficult to meet the requirements of a water tunnel for simulating the heat dissipation conditions of the seawater-activated battery. This paper proposes a water tunnel specifically designed for simulating the heat dissipation conditions of seawater-activated batteries, and the water tunnel consists of an external cooling water circulation system and an internal electrolyte circulation system. The experimental section’s design determines the water tunnel’s size and key technical indexes. The temperature distribution contour maps of the experimental section were obtained using Ansys Fluent software simulation. The cooling effect was analyzed, and a cooling water flow rate of 10 m/s was selected. Pressure and velocity contour maps were obtained by simulating the experimental section of the water tunnel. The results show that when the cooling water velocity is 10 m/s, the pressure drop of the experimental section is approximately 1.76 atmospheres. The flow field is uniform and stable, and the heat dissipation power can reach 45.5 kW, meeting the technical requirements.

Numerical investigation on the heat storage/heat release performance enhancement of phase change cemented paste backfill body with using casing-type heat pipe heat exchangers

Cemented paste backfill mining technology that recycling tailings and waste rocks can effectively reduce heat damage. Heat pipe exchangers, demonstrating much higher thermal conductivity than water pipe exchangers, led to the development of a novel phase change backfill body system with a built-in casing heat pipe exchanger (HP-PCB). Numerical analysis revealed that, for the melt and solidification of a large amount of PCM, the temperature step phenomenon was observed at both heat storage and heat storage/heat release coexistence stages. Increased surrounding rock temperatures enhanced heat storage and heat release capacities, but reduced system energy efficiency. The optimal water flow velocity was identified at the laminar-turbulent transition flow rate, 0.32 m/s. An increase in water inlet temperature resulted in lower heat release capacity and system energy efficiency. The energy efficiency of the HP-PCB system exceeded that of the traditional water pipe-backfill system by 37.22%. At a surrounding rock temperature of 45 °C, cooling water velocity of 0.32 m/s, and a 6 °C inlet water temperature, the HP-PCB system achieved its highest energy efficiency coefficient, 86.38%. These findings highlight the HP-PCB system potential for efficient geothermal energy extraction in mine.

The problem of the surface condenser overall heat transfer coefficient determining at high temperatures of cooling water

The article presents a comparison of the real overall heat transfer coefficient, based on thermal tests of the condenser of the steam turbine PT-25-90 KTZ during off-design operation (with a degraded vacuum) and its expected value, calculated via the Metropolitan Vickers formula. The average cooling water inlet temperature was 61.2 °C, average exhaust steam pressure was 0.542 bar during thermal tests. The average deviation of the expected overall condenser heat transfer coefficient from the real value was 27,18%. The calculations showed a higher difference between the real and expected value at the regimes with low cooling water velocity and with high exhaust stem pressure. The obtained results showed the need to refine the methodology of the condenser's overall heat transfer coefficient calculation in the degraded vacuum mode. This can be done by adding correction factors to the water temperatures that are typical for the degraded vacuum regime.

A New Conformal Penetrating Heating Strategy for Atherosclerotic Plaque

(1) Background: A combination of radiofrequency (RF) volumetric heating and convection cooling has been proposed to realize plaque ablation while protecting the endothelial layer. However, the depth of the plaque and the thickness of the endothelial layer vary in different atherosclerotic lesions. Current techniques cannot be used to achieve penetrating heating for atherosclerosis with two targets (the specified protection depth and the ablation depth). (2) Methods: A tissue-mimicking phantom heating experiment simulating atherosclerotic plaque ablation was conducted to investigate the effects of the control parameters, the target temperature (Ttarget), the cooling water temperature (Tf), and the cooling water velocity (Vf). To further quantitatively analyze and evaluate the ablation depth and the protection depth of the control parameters, a three-dimensional model was established. In addition, a conformal penetrating heating strategy was proposed based on the numerical results. (3) Results: It was found that Ttarget and Tf were factors that regulated the ablation results, and the temperatures of the plaques varied linearly with Ttarget or Tf. The simulation results showed that the ablation depth increased with the Ttarget while the protection depth decreased correspondently. This relationship reversed with the Tf. When the two parameters Ttarget and Tfwere controlled together, the ablation depth was 0.47 mm-1.43 mm and the protection depth was 0 mm-0.26 mm within 2 min of heating. (4) Conclusions: With the proposed control algorithm, the requirements of both the ablation depth and the endothelium protection depth can be met for most plaques through the simultaneous control of Ttarget and Tf.

Study of Particulate Fouling Inhibition Characteristics on a Novel Composite Coating

Particulate fouling is a common fouling in heat exchange equipment, it causes tube corrosion and increases flow resistance. Particulate fouling increases the hidden danger of equipment and requires high treatment costs. In this paper, a novel Ni−P−TiO2 composite coating is prepared on 316 stainless steel using electroless plating and the fouling inhibition characteristics of the novel composite coating are studied using a dynamic monitoring experimental system. The experimental results show that the fouling thermal resistance of the Ni−P−TiO2 composite coating is obviously lower than that of 316 stainless steel under the same working conditions. With the increase in cooling water velocity and inlet temperature, the surface fouling thermal resistance decreases, while, with the increase in particle concentration, the fouling thermal resistance increases. Based on DLVO theory, it is found that the surface energy of Ni−P−TiO2 composite coating is close to the best surface energy for inhibiting particulate fouling deposition, which can significantly inhibit particulate fouling deposition. Compared with the stainless-steel surface of a conventional plate heat exchanger, the Ni−P−TiO2 composite coating not only inhibits the accumulation of particulate fouling, but also reduces the adhesion strength of particulate fouling; additionally, the fouling is easier to strip off the heat exchange surface, which realizes the lasting and efficient fouling inhibition on the heat exchange surface. The research results can provide a data reference for the fouling inhibition design and daily efficient operation of heat exchangers.

Cooling challenges in a NEG-coated vacuum chamber of a light source

In a Light Source, unused synchrotron radiation is being distributed along the walls of the chambers. Due to the small conductance of the chambers, vacuum pumping will be based on the distributed concept, and then non-evaporable getter (NEG) coating is extensively used. The vacuum chambers are made of copper alloys tube, and cooling circuits are welded to the chamber to remove the heat load from the radiation generated. Filler metal creates a brazed joint between the water-cooling pipe and the vacuum chamber body. The thermal conductivity of the fillers is less than the vacuum chamber body. On the other hand, the velocity of the water in the cooling pipe is a critical parameter in thermal calculations that must be taken into account. So, in this paper, we study and investigate the effects of the filler metal and the cooling water velocity on cooling the NEG-coated chambers.

Experimental and Theoretical Investigations of a Plate-Fin Water Intercooler Equipped in a Boosted Diesel Engine

Abstract Intercoolers utilized in turbocharged engines are critically essential to efficiently improve the engine volumetric efficiency and therefore the engine specific power. Although boosting the internal combustion engines has been extensively investigated, further studies are required to provide relevant approaches to optimize the heat transfer coefficient. This paper experimentally and theoretically investigates the influence of inlet coolant velocity on heat transfer characteristics of an air-to-water intercooler equipped in a turbocharged diesel engine. This aims to optimize the heat transfer rate from water to air under typical engine operating conditions. The experiment has been conducted using a fully equipped engine testbed. The engine is turbocharged with a plate-fin intercooler. The intercooler is a perpendicular air–water heat transfer system that could be suitable for boosted marine engines or power generators. A simulation model was also developed using the finite volume model in the ansysfluent package. The distributions of inlet and outlet temperature, pressure, and velocity of air and coolant under various inlet water velocity and engine operating conditions are examined. The optimal heat transfer rate from air to water was achieved for this intercooler. The outlet air temperature after the intercooler decreases by about 10 °C, engine thermal efficiency increases by 0.7% approximately, engine power enhances by 2.5%, and the specific fuel consumption decreases by 0.82%. The CFD simulation and experiment model developed in this study for the plate-fin water intercooler could be a useful approach to optimize other intercooler systems. In this study, with a 270 × 270 × 10 mm plate-fin perpendicular air–water intercooler, an optimal cooling water velocity of 1.0 m/s, corresponding with a flowrate of 1780 liter/hr, is achieved.

Numerical Study of Photovoltaic Panel Thermal Efficiency Using Multi-Cooling Process

Renewable energy sources are becoming more and more popular, regarding the pollution and non-sustainability of common energy sources. Photovoltaic is the most direct way to convert solar radiation into electricity using the photovoltaic effect. This technology generates direct current (DC) electrical power from semiconductors when they are illuminated by photons. This paper presents a mathematical model in CFD that simulates the thermal presentation of a solar thermal photovoltaic panel equipped with circler, square and elliptic pin fin cooling module. The effect of cooling water velocity on photovoltaic panel average temperature and average cooling water temperature has been studied and the effect of cooling water velocity on photovoltaic panel average temperature and average cooling water temperature. The results show that velocity contours for water flows in circular, elliptic and square pin fin cooling module with inlet water velocities (0.0002, 0.0004 and 0.001 m/s). It is noticed that for square pin fin, the velocity between the pins is higher than the other types of pins, which leads to more circulation of water and more cooling.

Experimental investigation on the heat transfer enhancement of steam condensation on tube with hydrophilic-hydrophobic hybrid surface

The heat transfer enhancement of steam condensation on tube with hydrophilic-hydrophobic hybrid surface have been investigated comprehensively through experiment. It has been found that the steam condensation heat transfer performance on the tube with hydrophilic-hydrophobic hybrid surface has been enhanced significantly compared to that with hydrophilic surface. The results show that the steam pressure, cooling water velocity (flow rate) and non-condensable gas have influences on the steam condensation heat transfer performance on both tubes. The steam condensation heat transfer enhancement on the tube with hydrophilic-hydrophobic surfaces is due to the droplet drainage from hydrophobic stripes to hydrophilic stripes accelerating the discharge and formation of condensate from the tube. This work can be a guide for the design of enhanced condensing heat exchanger.

Condensing heat transfer performance in small-diameter enhanced tubes of absorption refrigeration system: An experimental investigation

The condensation heat transfer coefficient (HTC) in an absorption refrigeration system can be increased by using a small diameter as well as enhanced tubes. The small diameter tubes can increase the convection effect by decreasing the insulation layer because of having a larger fraction of the developing boundary layer area. For enhanced tubes, at low vapor velocity, surface tension performs a dominant role in decreasing the film resistance by correspondingly adjusting the film layer. The current research uses four types of small-diameter tubes having enhanced surfaces to augment the performance of the condenser. The saturation pressure is increased from 5.75 to 7.06 kPa, and the Nusselt number shows an increasing trend. However, Tube_D, which has grooves as well as corrugation, shows a decreasing trend with the Nusselt number at a higher saturation pressure. The cooling water velocity is varied from 0.77 to 1.55 m/s, and the overall HTC increased almost linearly. The heat flux also shows an increasing trend as the subcooling is changed from 0.4 to 2.6 °C, however, the HTC decreases with the increase in subcooling. In most cases, the enhancement factor decreased at high values of saturation pressure and condensate Reynolds number, except for the dimple corrugated tube (Tube_A). Of all the condensation tubes, Tube_C which is a corrugated tube with notched fins demonstrated the worst heat transfer performance. The current experiments summarize a new empirical correlation, which reasonably predicted the data within a variation of 1%.

Heat transfer behaviour of funnel mould copper plates with high casting speed during different water supply processes

ABSTRACT In the process of high casting speed, the study of funnel mould (FM) cooling process is particularly important. Based on the copper plate temperature measured by thermocouple, a mathematical model of the inverse heat transfer problem of the thin slab/copper plate was developed to calculate the boundary heat flux, then a positive mathematical model of thin slab/copper plate/cooling water coupled heat transfer has been developed, and the influence of the cooling water flows from top to bottom in the water channels on the heat transfer behaviour of the FM copper plate was analysed. The results show that when the cooling water flows from top to bottom in the water channels was adopted, the peak temperature of the copper plate hot face decreased 117°C, the maximum temperature of the cooling water decreased 24°C. Cooling water velocity and temperature have little influence on heat transfer of copper plate.

Prediction of the Deformation of Aluminum Alloy Drill Pipes in Thermal Assembly Based on a BP Neural Network

The connection between the steel joint and aluminum alloy pipe is the weak part of the aluminum alloy drill pipe. Practically, the interference connection between the aluminum alloy rod and the steel joint is usually realized by thermal assembly. In this paper, the relationship between the cooling water flow rate, initial heating temperature and the thermal deformation of the steel joint in interference thermal assembly was studied and predicted. Firstly, the temperature data of each measuring point of the steel joint were obtained by a thermal assembly experiment. Based on the theory of thermoelasticity, the analytical solution of the thermal deformation of the steel joint was studied. The temperature function was fitted by the least square method, and the calculated value of radial thermal deformation of the section was finally obtained. Based on the BP neural network algorithm, the thermal deformation of steel joint section was predicted. Besides, a prediction model was established, which was about the relationship between cooling water flow rate, initial heating temperature and interference. The magnitude of interference fit of steel joint was predicted. The magnitude of the interference fit of the steel joint was predicted. A polynomial model, exponential model and Gaussian model were adopted to predict the sectional deformation so as to compare and analyze the predictive performance of a BP neural network, among which the polynomial model was used to predict the magnitude of the interference fit. Through a comparative analysis of the fitting residual (RE) and sum of squares of the error (SSE), it can be known that a BP neural network has good prediction accuracy. The predicted results showed that the error of the prediction model increases with the increase of the heating temperature in the prediction model of the steel node interference and related factors. When the cooling water velocity hit 0.038 m/s, the prediction accuracy was the highest. The prediction error increases with the increase or decrease of the velocity. Especially when the velocity increases, the trend of error increasing became more obvious. The analysis shows that this method has better prediction accuracy.

Distributed deep reinforcement learning-based multi-objective integrated heat management method for water-cooling proton exchange membrane fuel cell

In order to improve the operational efficiency and stability of proton exchange membrane fuel cell (PEMFC), a distributed deep reinforcement learning (DDRL)-based integrated control strategy is proposed to solve the coordinated control problem of water pump and radiator in stack heat management system. This strategy substitutes the independent controllers of the water pump and radiator in the traditional control framework, and employs multi-input multi-output (MIMO) agents which simultaneously control the cooling water velocity of the water pump and the air velocity of the radiator, whilst monitoring the optimal global stack temperature control performance. To this end, an efficient curriculum exploration distributed double-delay deep determinate policy gradient (ECE-5DPG) algorithm is proposed for the strategy, the design of which is based on the concepts of curriculum learning, imitation learning, and distributed exploration, thus improving the robustness of the proposed strategy. The experimental results show that the proposed integrated control strategy can effectively control the cooling water velocity and air velocity simultaneously, thereby improving the operating efficiency of the PEMFC.

A validated asymptotic thermomechanical model for air-gap formation in tapered moulds in the continuous casting of steel

Abstract A recent asymptotics-based thermomechanical model is adapted and applied to the mould region in the continuous casting of round steel billets, with a view to describing the complex interplay between air-gap formation, mould taper, cooling channel width and cooling water velocity. Although the situation is steady state, the analysis leads to what is mathematically a dual moving-boundary problem for the solid–melt and solid–air interfaces, where the distance from the top of the mould region is the time-like variable in the problem. Moreover, the two interfaces are initiated at different locations. In addition, the thermal and mechanical problems are found to decouple and it is possible to solve the first ahead of the second. The model equations are solved numerically using a finite-difference method, and the approach is subsequently successfully validated against a previous finite-element model and experimental data from temperature measurements taken within the mould.

High-throughput laser fabrication of Ti-6Al-4V alloy: Part I. Numerical investigation of dynamic behavior in molten Pool

In the present work, an innovative high-throughput method was developed to fabricate a Ti-6Al-4V alloy via pulsed laser melting with water-cooled copper mold. Moreover, a three-dimensional transient model was established via numerical simulation to reveal the dynamic mechanism of heat transfer and fluid flow of the molten pool during high-throughput laser fabrication processes. Different laser powers, laser pulse durations and Marangoni coefficients were adopted to perform the numerical simulations, revealing the underlying physics of the heat transfer and fluid flow during the melting and solidification process. Special attention was paid to the cooling rate of the molten pool affected by cooling water velocity. Numerical results indicated that a “button” sample can be prepared in a short time of 200 ms by adjusting the processing parameters in this high-throughput preparation process. The maximum temperature of the molten pool was attained at the center underneath the laser beam and decreased radially outward. There was vigorous fluid flow mainly driven by thermal-capillary force in the molten pool. With increases in laser power and laser pulse duration, both the peak temperature and velocity of the molten pool increased. Accordingly, a high cooling rate was obtained under high cooling water velocity. Furthermore, the Marangoni effect fully changed the flow direction of the molten pool fluid, and the Marangoni convection flow influenced the temperature distribution of the molten pool. A new principle of the metallurgical dynamic behavior for the high-throughput laser fabrication process was established in this study and can provide technical guidance for high-throughput preparation experiments, such as laser parameter selection, structural control, and performance optimization.

Convective filmwise condensation on the outer surface of a vertical tube: A theoretical analysis

In this study, laminar filmwise condensation on the outer surface of a vertical tube in the presence of a flowing vapor is theoretically investigated. Analytical solution is obtained for the condensation on an isothermal tube wall when the film thickness is much smaller than the tube radius. The presence of vapor shear stress acting on the liquid-vapor interface was found to enhance the condensation heat transfer by accelerating the condensate film flow. The shearing enhancement factor increases almost linearly with the increase in vapor velocity. In addition, the influence of the vapor shear also increases with the reduction in the tube radius. The combined effect of surface tension and vapor velocity on the condensation heat transfer characteristics of the vertical tube was also investigated. From our investigation, it was determined that the surface tension has negligible effect on the condensation heat transfer performance of mini- and macro-size tubes. However, the influence of the surface tension becomes prominent for condensation on micro-size tubes. The influence of the Kelvin effect was also studied and it was found that the Kelvin effect is insignificant for condensation on micro-size tubes or tubes of larger sizes. A conjugate heat transfer analysis was also performed with cooling water flowing in the internal tube channel and flowing vapor condensation on the outer tube surface. In this analysis, the variation in the tube wall temperature was considered. A good comparison between our theoretical model and experimental results was achieved. The condensation heat transfer coefficient decreases as the cooling water velocity increases. The condensation heat transfer coefficient predicted for countercurrent flow configuration is larger than that for cocurrent flow configuration. The condensation heat transfer coefficients of both cocurrent and countercurrent configurations are larger than those where the tube wall is isothermal. For both cocurrent and countercurrent flow configurations, the thermal resistance lies mainly on conduction through the tube wall and convection of cooling water at the inlet condensing region whereas the dominant thermal resistance gradually shifts to the condensate film as the distance increases from the top of the tube. The tube wall temperature is affected by a combined effect of the thermal resistance distribution and the variation in the overall temperature difference.

Determination of thermal resistance at mould-strand interface due to shrinkage in billet continuous casting – Development and application of a novel integrated numerical model

An industrial continuous casting process of steel billet is analysed using a novel, integrated numerical model for the heat transfer and solidification of the molten metal as it passes through the mould. One of the major difficulties related to determination of thermal resistance at the mould-strand interface is addressed in the present study. Contrary to empirical or semi-empirical methods commonly used in the industry for determination of the heat transfer at the interface, the present work deals with the determination of the interfacial thermal resistance by adopting a novel mathematical approach. A two-dimensional, transient, finite difference method based code is developed for a plane slice of molten steel moving with a given casting speed down the mould. The resultant solidification and thermal shrinkage are calculated from the temperature distribution and knowledge of the temperature dependent density of steel. The heat transfer from the cast strand to the cooling water is modelled by a network of thermal resistance. The model is validated against experimental data obtained from literature. The numerical results reveal a dominant role of advection of the gaseous mixture of air and other components from pyrolysis of casting oil, in the interfacial gap formed due to the shrinkage of steel, which has not been considered previously in the formulation of thermal resistance. The numerical model is also used to analyse the heat transfer in the mould and the growth of the solidified shell as the strand moves down the mould. In particular, the corner regions of the strand are found to be hotter than the off-corner regions, due to non-uniform heat transfer across the periphery. Also, the effect of casting speed in the mould is found to be dominant in comparison to other casting parameters, such as mould thickness and cooling water velocity.

Cooling efficiency and cooling intensity of cooling staves in blast furnace hearth

The main function of the cooling system is to help preserve the refractory lining for as long as possible, but the evaluation indicators of blast furnace cooling system have not been studied in detail. In the study, the blast furnace cooling system was analyzed in-depth from the perspective of cooling essence and heat transfer principle based on the investigation of many blast furnaces. The concept of cooling efficiency and cooling intensity of the blast furnace hearth cooling system were proposed with quantitative characterization. The results show that the cooling efficiency is 88–99% and the cooling intensity is 70–95% generally. The effect of the cooling water velocity and specific surface area on cooling efficiency and cooling intensity are analyzed from a view of optimizing the design. Improving the specific surface area of cooling system and increasing the cooling water velocity can increase the cooling efficiency and cooling intensity. The specific surface area can be designed to be more than 1.1 and the water velocity should be greater than 1.5 m/s. Finally, the blast furnace operation strategy taken in the actual production process and the methods for improving the cooling intensity and cooling efficiency are assessed.

Numerical analysis of the downhole flow field with compressible fluid in hydrothermal jet drilling

A novel hydrothermal jet drilling technology is proposed, which is expected to be suitable for the exploitation of subsurface hydrocarbon resource or geothermal energy. The flow field is analyzed with compressible fluid. Influences of jet temperature, jet velocity, cooling water velocity, and cooling water temperature are discussed. Gray correlation method is used to compare the effects of different factors and further verification is performed. Simulation results are validated by results from experiments and analytical models. The values of specific heat are relatively high in the annulus because the hydrothermal jet undergoes the pseudo-critical point. Despite higher temperatures of the hydrothermal jet, the annular high temperature fluid can be effectively cooled. Considering both thermal effect and impact, it may be better to keep the hydrothermal jet temperature in the range of 700 K–800 K under the conditions of this paper. Under different cooling water velocities, the varying trend of the borehole wall temperature corresponds with that of the specific heat. The cooling water velocity has the most significant impact on the variation of the annular temperature, with the following sequence being jet temperature, jet velocity and cooling water temperature. Adjusting cooling water velocity may be the most efficient and cost-effective way for the hydrothermal jet drilling.

One-day performance evaluation of photovoltaic-thermoelectric hybrid system

Almost all of the researches about the photovoltaic-thermoelectric (PV-TE) hybrid system focus on the steady-state performance assuming solar irradiance is constant (1000 W/m2) and ignoring the influence of changing solar radiation with time. In this paper, a theoretical model for obtaining the coupling system one-day performance is established. Detailed one-day changes in coupling system temperatures, powers, efficiencies are revealed. The thermal concentration ratio is discussed and is optimized to increase the one-day average efficiency. Influences of photovoltaic efficiency temperature coefficient, thermoelectric Z value, water cooling mass and velocity are discussed. The one-day performances of pure PV and PV-TE hybrid system are compared. The results show that the coupling system can obtain the highest one-day average efficiency by optimizing the thermal concentration ratio. The highest one-day average efficiency of the hybrid system decrease with the rise of the photovoltaic temperature coefficient and increase with the thermoelectric Z value augmenting. The mass of the cooling water has a remarkable positive effect on the hybrid system performance while the impact of the cooling water velocity is tiny. The hybrid system one-day capability is preferable to the pure PV system when the thermoelectric Z value is large or the photovoltaic temperature coefficient is small.