Inlet Side Research Articles

원형 및 사각타원 전열관을 이용한 냉장고 증발기용 핀-튜브 열교환기의 공기측 열유동 비교평가

The objective of this study was to improve performance of heat exchanger for household refrigerator by modifying the shape of heat transfer tube used in the existing evaporator. In the case of a fin-tube heat exchanger, the thermal resistance accounts for 60 to 80%. It occurs in the air-side heat exchange area, which has a great influence on performance. Existing round tube was replaced with a round rectangle tube to reduce air thermal resistance and improve thermal conduction performance. When a heat exchanger with a round tube was changed to a heat exchanger with a round rectangle tube, the f-factor decreased and the j-factor increased. The pressure loss of the air side inlet was also reduced in the round rectangle tube. Thus, changing the shape of a round tube fin-tube heat exchanger to a round rectangle tube can increase the efficiency of an energy system.

Numerical Study on Rotor Cooling of Turbine in Supercritical Carbon Dioxide Cycle.

The supercritical carbon dioxide cycle is a Brayton cycle with great application prospects. As a key equipment in this cycle, the turbine machinery usually adopts a dry gas seal as the sealing method between the cylinder and sliding bearing to reduce the leakage of carbon dioxide. In this paper, the numerical model of supercritical carbon dioxide turbine rotor cooling is established, and the grid independence is verified. The effects of inlet temperature and flow rate of dry gas seal and leakage flow rate from cylinder to dry gas seal at the high-temperature inlet side of a turbine upon rotor cooling are studied. The effects of inlet temperature T in and flow rate Q v of sealing gas in a dry gas seal and leakage mass flow rate Q m from a cylinder to dry gas seal on pressure loss, outlet flow distribution, exhaust temperature, and rotor temperature distribution are analyzed. As a result, it can be found that with the increase of the inlet flow rate of dry gas seal gas and the leakage flow rate from cylinder to dry gas seal, the pressure difference between the inlet and outlet of each seal gas increases. When the inlet flow rate of dry gas seal gas ranges from 300 N m3/h to 900 N m3/h, with the leakage flow from cylinder to dry gas seal increasing from 1.3 kg/s to 2.08 kg/s, the pressure difference between inlet and outlet of each seal gas increases by 7.9% to 13.4%. The pressure difference between the inlet and outlet of each seal gas decreases with the increase of the inlet temperature of dry gas seal gas. When the inlet flow rate of the seal gas of the dry gas seal is 300 N m3/h and the leakage flow rate from cylinder to dry gas seal is 2.08 kg/s, the inlet temperature of seal gas increases from 100 to 150 °C, and the flow distribution at the outlet is basically unchanged. The research provides theoretical reference for rotor cooling design of a supercritical carbon dioxide turbine.

Study on dust pollution law and ventilation optimization of roadway excavation and shotcrete simultaneous operation

The simultaneous operation of heading machine and shotcrete machine often occurs in the process of roadway development. Many dust sources, such as cutting dust and shotcrete dust, increase the complexity of roadway dust pollution. In order to find out the law of dust migration in tunneling and shotcrete operation at the same time, and put forward effective dust control optimization measures, this paper takes a mine roadway as an example, based on Fluent numerical simulation software, the dust migration law is analyzed when the roadway driving operation and the shotcrete operation are carried out separately and when the two operations are carried out simultaneously. Moreover, the orthogonal experiment is used to optimize the ventilation parameters of the working face. Results show that the dust concentration in the roadway decreases gradually from high to low when the single shotcrete operation is on the air inlet side. On the return air side, the dust concentration in the roadway increases first and then decreases. In the single tunneling process, the dust concentration on the return air side is significantly higher than that on the inlet side, and at the 52 m section, the dust concentration basically decreases to less than 100 mg/m3. When tunneling and shotcrete work simultaneously, the dust migration distance increases, and the dust concentration decreases to less than 100 mg/m3 at the section of 55 m. Through an orthogonal experiment, the optimal combination of working ventilation parameters is obtained. This study gives a helpful guidance for dust suppression when two or more dust production processes operate simultaneously.

Failure analysis on abnormal leakage of shell and tube heat exchanger in specialty chemical plant

The shell and tube heat exchanger has been widely used in the chemical industry. However, because of complex operating conditions, the heat exchanger tubes sometimes are leaked. This paper conducted in-depth failure analysis on abnormal leakage of several tubes of a shell and tube heat exchanger, which had been used for nine years in a methyl methacrylate production facility. In order to find out the root cause of the failure, chemical analysis, metallographic structure inspection and morphology observation of the leakage tubes were carried out. The composition and properties of the tube scales were analyzed by X-ray fluorescence spectroscopic analysis (XRF), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), and energy spectrum analysis (EDS). The micro-zone features of the leaked tubes were observed with three-dimensional stereo microscope (3D-SM) and scanning electron microscope (SEM). According to the testing results and the actual operating conditions of the heat exchanger, the root cause of abnormal leakage of the tubes was finally determined. The key finding was that the terephthalic acid gas was suddenly desublimated into solid particles while its temperature was about 300 °C. Thus, the gas containing terephthalic acid particles caused erosion wear, abrasive wear and local corrosion onto the inlet side of the heat exchanger, leading to abnormal leakage of the tubes. Finally, some suggestions were put forward for the heat exchanger, which were also conducive to the safe operation and failure prevention of similar equipment.

Experimental study on the thermal management of an open-cathode air-cooled proton exchange membrane fuel cell stack with ultra-thin metal bipolar plates

Reliable thermal management ensures stable and efficient operation of proton exchange membrane (PEM) fuel cells. An air-cooled fuel cell stack with metal bipolar plates was developed, and 32 micro-thermocouples were arranged for in situ measurement of the temperature distribution. The resistance characteristic of the stack was tested in a wind tunnel, and then the effects of hydrogen pressure and airflow rate were analyzed. The results show that the highest and average temperatures in the stack exhibit a “parabolic” distribution as well as the maximum temperature difference of each single cell on the inlet side of the cathode. However, the temperature difference on the outlet side shows an “anti-parabolic” distribution. With a decrease in the airflow rate, the temperature uniformity in the stack deteriorates gradually. When the maximum pulse width modulation (PWM) duty cycle of the fans was 70% and the current density was 500 mA/cm2, the temperature difference between different single cells and inside a single cell can reach 19.7 °C and 8.4 °C, respectively. The temperature uniformity in the stack at high current densities could be effectively improved by increasing the airflow rate. In addition, the hydrogen pressure and airflow rate have a certain effect on the voltage consistency.

Self-loading microfluidic platform with ultra-thin nanoporous membrane for organ-on-chip by wafer-level processing

Embedded porous membranes are a key element of various organ-on-chip systems. The widely used commercial polymer membranes impose limits with regard to chip integration and thinness. We report a microfluidic chip platform with the key element of a monolithically integrated, ultra-thin (700 nm) nanoporous membrane made of ultra-low-stress (<35 MPa) SixNy for culturing and testing reconstructed tissue. The membrane is designed to support various in vitro tissues including co-cultures and to allow passage of molecules but not of cells. A digital laser write method was used to produce nanopores with deterministic but highly flexible positioning within the membrane. A thin layer of photoresist was exposed by accumulation of femtosecond pulses for local two-photon polymerization, which allowed nanopores as small as 350 nm in diameter to be generated through the membranes in a subsequent plasma etch process. The fabricated membranes were used to separate a microfluidic chip into two compartments, which are connected to the outside by microchannel structures. With unique side inlets for fluids, all cells are exposed to identical flow velocities and shear stresses. With the hydrophilic nature of chip materials the self-loading seeding is controlled bottom-up by capillary forces, which makes the seeding procedure homogeneous and less dependent on the operator. The chip is designed to allow fabrication by wafer-level MEMS manufacturing technologies without critical assembly steps, thereby promoting reproducibility and scale-up of fabrication. In order to establish a fully functional test system to be used in a lab incubator, a holder for the bare chip was designed and 3D-printed with additional elements for gravity driven pumping. In order to mimic physiological conditions, the holder was designed to provide not only media delivery but also appropriate shear stress to the tissue. To prove usability, murine microvascular endothelial cells (muMEC) were seeded on the membrane within the chip. Cell compatibility was confirmed after 3 days of dynamic cultivation using fluorescence live/dead assays. Cultivation proved to be reproducible and led to confluent layers with cells preferentially grown on nanoporous areas. The system can in future be cost effectively manufactured in larger quantities in MEMS foundries and can be used for a wide variety of in vitro tissues and test scenarios including pumpless operation within cell incubator cabinets.

Heat Transfer Characteristics of Cold Water Phase-Change Heat Exchangers under Active Icing Conditions

Under active icing conditions, the heat transfer performance of the CPHE has a significant impact on the system’s efficiency and energy consumption. Using the enthalpy-porosity method for describing the solidification process of liquids, the simulation and analysis of the effects of different parameter changes on the CPHE heat transfer performance were conducted to clarify the effects of the changes in the intermediary side inlet water temperature, intermediate water flow rate, and cold water flow rate on the heat transfer process in the CPHE. According to our results, changing the intermediary inlet water temperature has a greater impact on the heat transfer process in the cold-water phase-change heat exchangers. For every decrease of 0.5 °C in the intermediary side inlet water temperature, the average heat transfer coefficient increases by approximately 50 W/m2-K. Changes in the intermediary water flow rate affect the cold water phase-change heat exchanger’s heat transfer process. By increasing the intermediary water flow rate, the average heat transfer coefficient of a cold water phase-change heat exchanger can be improved, but the growth decreases, and the maximum flow rate of the intermediary water should not exceed 0.5 m per second. A change in the cold water flow rate in the cold water phase-change heat exchanger’s heat transfer process has a small impact on the cold water flow rate, increasing by 0.02 m/s each, with the average heat transfer coefficient increasing by 20 W/m2-K.

Bi-directional catalyst injection in floating catalyst chemical vapor deposition for enhanced carbon nanotube fiber yield

Carbon nanotube fiber (CNT fiber) synthesized through floating catalyst chemical vapor deposition (FC-CVD) is one of the strongest man-made fibers ever synthesized. The poor carbon conversion in the FC-CVD process is one of the major hurdles in its commercial deployment. In this work, we have employed a novel method of bi-directional catalyst injection where catalysts were injected from both inlet and outlet sides of the reactor. The injection of the catalyst from the outlet into the reactor reaction zone was possible by a backflow caused by the convection vortex as predicted by the computational fluid dynamics (CFD) analysis. Bi-directional catalyst injection was able to enhance the carbon conversion by 56% compared to conventional unidirectional injection. CNT fibers obtained in bi-directional catalyst injection are a mixture of multi-walled (MW) and single-walled (SW) CNTs whereas unidirectional catalyst injection resulted in MWCNTs only. The average CNT bundle diameter dimensions were similar in both unidirectional and bi-directional catalyst injection. The amorphous carbon content was lower for bi-directional catalyst injection. A mechanism for the improvement of carbon conversion in bi-direction catalyst injection has been proposed.

CFD-DEM Simulation of Particle Fluidization Behavior and Glycerol Gasification in a Supercritical Water Fluidized Bed

In this study, a mathematical model of hydrogen production from glycerol gasification in supercritical water was established based on the CFD-DEM method. The fluidization process of a supercritical water fluidized bed and the effects of bed height and feed structure on particle distribution and residence time of feedstock were analyzed. Additionally, the temperature field in the fluidized bed, the reaction rate distribution of each reaction and the influence of wall temperature on gas yields were also studied. The simulation results show that the bubble channel is easy to form along the wall at one side of the feed inlet. When the initial bed height is high, and the double symmetric feed inlet structure is used, the residence time of the feedstock is prolonged. The pyrolysis of glycerol mainly occurs in the middle and lower part of the fluidized bed reactor, and the reaction rate of the water gas shift reaction and methanation reaction are highest near the outlet, and a high wall temperature is conducive to the glycerol gasification.

Comparative evaluation of the pump mode and turbine mode performance of a large vaned-voluted centrifugal pump

Large vaned-voluted centrifugal pump is a general machine used for large-scale water diversion. As a vane-type hydraulic machinery, it also has the ability of reversible operation. With the introduction of policies to reduce carbon emissions, the proportion of unstable new energy use has increased. The existing large centrifugal pump unit can realize the function of reverse power transfer. For peak shaving and valley filling of power grid, it has high feasibility and economy. In this paper, a large vaned-voluted centrifugal pump is simulated numerically, it is external characteristics and flow state under positive and negative rotation are obtained, its performance is predicted by best efficiency point method, and it is found that pump reversal can run at the optimum efficiency point with higher flow rate and head. Error analysis is carried out for different formulas. The flow energy dissipation (FED) of different flow rates under positive and negative rotation is analyzed. It is found that the main energy loss locates on suction side of blade, inlet and outlet part of blade and tail part of guide blade head. By comparing the flow energy dissipation distribution under the same flow conditions with positive and reverse rotation, it is found that the high energy loss area of blade mainly exists in inlet and outlet part of blade in pump mode. The high energy loss area of the blades in turbine mode mainly exists in the inlet part of the blades. This study is of great significance to the operation of low-carbon power grid assisted by existing reservoirs and hydraulic machinery.

Analysis of numerical and grey relation method of the effect of helical tape insert density on the hydrothermal performance

In this study, the hydrothermal performance of the Double pipe heat exchangers(DPHEs) with a continuous and variable helical tape insert(HTI) conducted on the outer surface of the inner pipe was numerically investigated by using the generated three-dimensional(3D) computational fluid dynamics(CFD) models. The numerical analyzes were performed under variable pitch ratios (0.167≤λ≤0.500), annulus side Prandtl number(Pr) (5.9≤Pran≤7.8) and Reynolds numbers(Re) (4200≤Rean≤16000) conditions. The numerical model was first validated for the conventional equal HTI DPHE model by comparison with experimental data obtained from the literature and empirical correlations. The validated model was then used to determine the effects of the variable HTI on the outer surface of the inner pipe. The relationship between the Nusselt number(Nu) and Darcy friction factor(f) was examined by using Grey Relation Analysis(GRA) method. The using of the denser HTIs on the tube side inlet region increases Nu about 9% compared with the conventional model. The f values of the models with variable HTI densities were calculated as higher than the Equal model under all Re conditions. The obtained results from the GRA method, conventional Equal model can be used for low Re, but the Inlet model can be preferred for 14000 and above Re conditions.

Uniforming thermal distribution by air-convection aspirated in partially hollowed tetrahedral lattice porous cold plates for the drone battery

A pouch-type lithium-ion battery requires effective thermal management and a solution for temperature imbalances depending on its morphological characteristics. In this study, we present such a solution for rows of pouch-type lithium-ion battery cells controlled by aspirated air convection in a tetrahedral lattice porous cold plate, as well as by reducing the temperature imbalance in the lattice porous medium (LPM). The hollowness ratio (HR) was applied to the ligament, and its effect was investigated in the entrance region of the cold plate channel. A series of steady-state numerical simulations and experiments were conducted to demonstrate the effectiveness of the solution. As a result, the temperature deviation in the longitudinal direction of the LPM cold plate's lower substrate was 6.4°C under the 7 C-rate heat source condition. Owing to the inlet effect of forced convection due to the aspirated airflow, the lowest temperature was observed on the inlet side, and a higher temperature was observed on the outlet side. By applying the HR to the ligament of the LPM cold plate, it was confirmed that the temperature deviation decreased to 4.4°C, which was 2°C lower than that applied to the simple solid ligament. In addition, the temperature uniformity index (TUI) was 0.96, when the hollowness ratio was 0.64.

Numerical Simulation of a Flat-Sheet Membrane-based Dehumidifier with Various Serpentine Flow Channels

In the present analysis, three potential serpentine flow channel designs for a flat-sheet membrane-based dehumidifier are designed and evaluated in terms of performance metrics such as dehumidification rate (DR), approach temperature (AT), pressure drop (ΔP), and coefficient of performance (COP). The dry side inlet air temperature and relative humidity (RH) are set at 27°C and 0%, and the wet side inlet air temperature and RH are fixed at 40°C and 85%. The inlet air flow rates of the dry and wet sides are both controlled in the range of 20-60 L min−1. The simulation results revealed that the geometrical design of the flow channels has a remarkable impact on the dehumidification performance of the dehumidifier. It is outlined that the water vapor concentration and temperature distribution at the outlet of all proposed serpentine flow channels are almost identical, showing the oversized design of the three- and six-inlet serpentine channels. Under the air flow rates of 30 ∼ 60 L min−1, it is seen that the DR, AT, and ΔP of three-, six-, and nine-inlet serpentine channels are in descending order. It is found that the size and quantity of the channel outlets and inlets have a great influence on the pressure drop. Moreover, the dehumidifier with nine-inlet serpentine flow channel can provide the highest COP with a limited increase in the pressure loss. Hence, this channel design can be a good candidate to be implemented in the flat-sheet membrane-based dehumidifier. The findings of this study could be beneficial for the design of novel dehumidifiers.

Effect of Different Inlet/Outlet Port Configurations on the Thermal Management of Prismatic Li-Ion Batteries

Abstract The performance and life cycle of Li-ion batteries are governed by the maximum temperature and uniformity of temperature distribution in the battery pack, and an efficient thermal management system is highly desired to keep the operating temperature of the battery pack within safe operating limits. Air cooling has received extensive attention in the area of battery thermal management. However, performance intensification of air-cooling modules is essential while keeping the simplicity of design to satisfy the weight and space constraints of electric vehicle (EV) applications. In the current work, efforts have been made to design a simple and generalized air-cooling module for efficient thermal management of Li-ion batteries. The current work explored the effect of two common air flow configurations: side inlet and side outlet (SS) and side inlet and front outlet (SF), with different number of inlet/outlet ports (single inlet and single outlet, single inlet and two outlets, two inlets and single outlet, and two inlets and two outlets) on the thermal and hydraulic performance of Li-ion battery pack. Subsequently, a new design of battery module with an open outlet port is proposed. It is observed that the way fluid leaves the cooling module significantly influences the flow and temperature distribution uniformity of the battery pack. Significant improvement in the fluid flow distribution and lower temperature fluctuation are maintained by the SF designs as compared to the SS designs. Among all SS designs, only SS-Ib at Vin ≥ 5.6 m/s and SS-IV at Vin ≥ 4.8 m/s are found suitable for the thermal management of Li-ion battery pack, whereas all SF designs maintained desired Tmax and ΔTmax conditions at Vin ≥ 4.8 m/s. Furthermore, the new design (SF-V) with an open outlet results in the reduction of Tmax by 7 °C and ΔTmax by 64.5% as compared to base design (SS-Ia) at the same pressure drop penalty.

Flow Characteristics and Optimization Design of the Stator–Rotor Cavity of the Full Tubular Pump

The full tubular pump device is taken as the research object in this article. This research method adopts the numerical simulation technology based on the SST (Shear-Stress-Transport) k-ω turbulence model to explore the internal flow characteristics of the stator–rotor cavity of the full tubular pump and optimize the stator–rotor clearance structure. The research shows that under the design conditions, compared with the axial flow pump, the torque increases by 47.91 N·m at the stator–rotor cavity structure and the efficiency decreases by about 20%. The torque at the rotor clearance of the full tubular pump accounts for about 50% of the torque at the rotor. Since there is a large area of backflow on both sides of the cavity, and there is a vortex structure on the inlet side of the cavity, it shows that the rotor structure and its area greatly affect the operating efficiency of the pump device. With the reduction in the rotor force area, the clearance length, and the outer diameter of the disc, the operating efficiency of the pump device gradually increases. Under the design conditions, the optimized model has a maximum efficiency increase of 14.04% and the torque at the cavity rotor is reduced by 39.25 N·m. The results show that the operating efficiency of the full tubular pump is closely related to its rotor structure area, and the force area of the rotor structure needs to be controlled in the actual design process.

Size reduction and enhanced power generation in ORC by vaporizing LNG at high supercritical pressure irrespective of delivery pressure

LNG regasification terminals generate power with Organic Rankine cycle (ORC) using LNG as the heat sink. A 3-stage ORC designed for regasification pressure of 70 bar(a) produces the highest net power with appropriate temperature approach in each heat exchanger and it is higher by 108 kW for LNG flow of 30 kg/s compared to the fixed temperature approach of 5 K. For 30 bar(a) delivery pressure, a regasification pressure of 70 bar(a) instead of 30 bar(a) produces about 17% higher net power and 1.9 times reduction of total heat exchanger area. The sizing parameter of the turbine becomes 12.3% lower. The analysis shows that total outlet volume flow rate through turbine, pump inlet and hot side of heat exchangers are 24.5%, 28.2% and 25.0% lower respectively for 70 bar(a) regasification pressure. The total capital investment for 30/30 bar(a) and 70/30 bar(a) systems are 18.8% and 21.8% respectively higher than that of 70/70 bar(a) system. For the delivery pressure of CNG at 30 bar(a), the net present value of 70 bar(a) regasification pressure is 1.7% higher than that for 30 bar(a) regasification pressure. This is over and above the flexibility of operation that the regasification terminal achieves with supercritical LNG.

A Numerical Study of Dual-Inlet Air-Cooled PV/T Solar Collectors with Various Airflow Channel Configurations

The multi-inlet air-cooled photovoltaic/thermal (PV/T) technology not only avoids the poor heat transfer conditions of single-inlet PV/T air collectors but also reduces photovoltaic (PV) peak temperature and improves solar energy utilization. Since air-cooled PV/T collectors use no more than three inlets, the increase in thermal efficiency is significantly more effective. Therefore, a numerical analysis of an air-cooled PV/T solar collector with two side inlets was performed. The heat transfer efficiency and flow characteristics were then investigated for various air channel configurations. Increasing the area of the second inlet improves thermal and electrical efficiency. As the length ratio of the front and rear airflow channels is reduced, the average outlet temperature first decreases and then increases. The heat-exchanging quantity of the dual-inlet air-cooled PV/T collector is minimal. The thermal efficiency of the dual-inlet air-cooled PV/T collector can be elevated by increasing the angle between the solar panel and the bottom plate. However, the average temperature of the solar panels is increased and the photoelectric conversion efficiency decreased. This design will achieve a reduction in carbon emissions and an increase in the proportion of clean energy in a low- or zero-carbon green building.

Comparison of simulation and experimental test results of the turbocharger temperature for two gasoline direct injection engines

Understanding heat delivery in a multifaceted and vital engine component, such as the turbocharger, is important for improving engine performance and efficiency, but it is challenging to determine. In this paper, the temperature distribution in a turbocharger body was measured experimentally using a thermal camera, and a one-dimensional simulation of a turbocharger was developed for the temperature distribution. As part of the work, an innovative method is used to determine the thermal radiation constant of the turbocharger housing. In this method, the complete turbocharger system was first installed in a laboratory furnace and, at each stage, the temperature of the furnace was carefully adjusted. After temperature stabilization, a thermal image was taken with a thermal camera, and the radiation coefficient was obtained. Finally, a measurement of the temperature distribution was performed on the engine's test cell for the turbochargers of two three-cylinder gasoline engines (i.e. engines 1200 cc and 999 cc). The experiments include steady-state and transient tests. The transient tests include hot and cold tests at various operating conditions. The results showed that the maximum temperature of the turbine housing varies linearly with inlet gas temperature. Also, the axial distribution of the temperature in the compressor volute shows that temperature increases from the inlet side to the bearing housing side. Based on the numerical results, the maximum turbine housing temperature for engine 1200 cc is 679 °C and for engine 999 cc is 523 °C.

Taylor bubble formation and flowing in a straight millimetric channel with a cross-junction inlet geometry Part II: Gas-liquid mass transfer

• Mass transfer was studied during bubble formation at a cross-junction. • Accuracy of resazurin-based technique was improved by advanced image systems. • Different mechanisms were observed for the developing O 2 concentration fields. • Oxygen concentration fields were measured during and after bubble pinch-off. • A scaling law relating k L a and f c was proposed to gather literature data. Using the resazurin-based colorimetric technique and advanced image acquisition, the equivalent oxygen concentration fields inside the liquid slugs were measured during and after the bubble formation stage at a cross-junction in a straight millimetric channel. Firstly, two different mechanisms were identified for the development of oxygen concentration fields depending on the two-phase Reynolds numbers (Re TP ). Under low Re TP , a jet-like central oxygen concentration ‘finger’ occurred between the newly formed bubble and the gas finger at the bubble pinch-off point. Right after the bubble pinch-off, the dissolved oxygen was transported first by the entering liquid from two side inlets, and later by the developing recirculation loop inside the liquid slug. Under higher Re TP , two highly concentrated oxygen concentration spots were formed near the bubble rear and the channel wall region, and a much more complex flow structure in the liquid slug appeared. Then, whatever the operating conditions, it was observed that the averaged oxygen concentrations inside the liquid slug followed a nearly linear relation as a function of the axial position in the channel, and that the related mass flux density decreased as far as the bubbles flowed along the channel’s length. The bubble formation process could be decomposed into three stages when considering the temporal evolution of the cumulated oxygen mass and depending on the development of the liquid slug. At last, the overall volumetric liquid side mass transfer coefficients ( k L a ) were deduced from the concentration fields, and found to linearly increase with the recirculation frequencies, leading to a scaling law.

Influence of fluid inlet–outlet on hydrothermal evaluation for different serpentine mini‐channel heat sink configurations

AbstractIn the current study, numerical and experimental investigations of the hydrothermal performance of three configurations of a serpentine mini‐channel heat sink (MCHS) were conducted. The outcome of one inlet with two outlets has been studied for two new models, namely, A and B, and compared with the traditional MCHS model. Model A has a central side single inlet, then the channel is directly split and the two outlets are on the other side. In Model B, the single side inlet passes to the other side, and then it splits and the outlets are on the same inlet side. The numerical solution is obtained by using the commercial ANSYS Fluent 2020 R2 under laminar flow conditions. The current study's numerical results were compared and validated with the experimental results of the traditional model. The results reveal that the total performance factor has considerably improved, according to the findings for the model (A and B). The average total hydrothermal performance for Model B is 1.48 and for Model A is 1.53 as compared to the traditional MCHS. However, the temperature distribution, maximum base temperature, Nusselt number, and thermal resistance of Model B are best as compared to Model A.