Convective Rate Research Articles

An experimental study on vertical temperature profile of facade fire plume ejected from compartment with an opening subjected to external wind normal to facade

This paper investigated the vertical temperature profile of facade fire plume ejected from compartment with an opening subjected to external wind normal to the facade, which has not been quantified in the literature. Experiments were carried out using a cubic compartment (dimensions: 0.4 m) with an opening attached by a vertical facade. The vertical temperature profile in the facade fire plume under different ventilation conditions (opening geometries) and wind speeds was measured by thermocouple arrays consisting of 42 K-type thermocouples installed along the facade wall. It was found that the temperature at a given height decreased with increasing wind speed, as the air entrainment into the plume was stronger than that without wind. Then, a correlation was proposed based on physical analysis on the variation of total convective heat release rate (virtual origin) and air entrainment (correlation coefficient) into the facade fire plume, to describe the front wind effect on the vertical temperature profile. Experimental data for different opening geometries (ventilation factor) and wind speeds can be well correlated by the proposed correlation. The new findings and the proposed correlation provide a fundamental base for understanding basically the facade fire behavior with an opening under external wind normal to facade.

Tailoring the Surface Morphology and Microstructure of Electrodeposited Copper Foil with Organic Additives

Copper foil manufactured by high-speed electrochemical deposition (ED) is an essential material for its extensive applications such as the negative current collector for lithium-ion batteries (LIBs) or building up the designed connection pattern on the printed circuit boards (PCBs). Thus, producing copper foil with optimal quality and machinability depending on the end products is necessary. For example, the thickness of Cu foils for LIBs should be thin (< 10 µm) to reduce the volume and weight of batteries but the mechanical properties should remain strong enough to go through the roll-to-roll manufacturing process without fracture. In addition, the surface roughness on both sides should be identically smooth and glossy to provide the coating carbon materials with acceptable wetability and adhesion. On the other hand, Cu foils for the fifth generation (5G) high-frequency wireless devices should be exceedingly smooth because the skin depth of copper caused by the so-called skin effect is merely 0.266 µm when the transmitting frequency of signals is up to 60 GHz. Thus, a great majority of electric current passing through the conductor will flow extremely near the surface. Under such circumstances, coarse surface roughness has a significant detrimental effect on the signal loss of wireless communication devices, and consequently, the surface morphology and mechanical properties of copper foils should be further improved in order to meet the requirements for the next generation electronic devices. The microstructure of copper fabricated by ED depends highly on plating parameters, including current density, convection rate of the electrolyte, pulsed/direct current deposition, or using appropriate organic additives to ameliorate the nucleation behavior of Cu from cupric ions. Manufacturing of ED copper foils ought to operate with very high current density and high temperature to promote the yield rate for mass production, and the gelatin-based additive has been used for a long time. However, grain structure and surface roughness are coarse and mechanical properties are merely acceptable with around 250 MPa tensile strength and a 4% elongation rate for a normal 18 µm foil. In this work, we demonstrate the copper foil fabricated by high-speed electrodeposition with a current density of 450 mA/cm2 (average growth rate > 150 nm/s) from a 54oC bath, which meets the required yield rate for genuine mass-production, and tailoring the microstructure of copper with selective additives. The surface morphology of the foil facing the electrolyte side is smooth by our designed additives, and surface roughness values, Ra and Rq, are less than 100 nm, which are as smooth as foils manufactured via rolling process. In addition, the structure of copper is further tuned by a specific additive, and the grain size of copper is getting smaller as the concentration of this additive is increased. When the concentration of this additive is up to 800 ppm, the average grain size of copper is shrunk from 3 µm to 0.3 µm, and extremely unique copper texture with nearly single (220) orientation is constructed. Owing to such delicate microstructure, considerable improvement in mechanical properties with more than 40 % increase in tensile strength and 4 times increase in the elongation rate compared to the conventional gelatin-based copper foil is achieved. The surface morphology and structure of copper foil are properly characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM) and tensile testing machine, and the applied additive to tailor the structure of copper will be clearly revealed and discussed. Finally, a novel and commercially realizable scheme to fabricate copper foil with ultra smooth surface morphology and ductile mechanical properties by high-speed ED is proposed.

Impact of external temperature distribution on the convective mass flow rate in a vertical channel – A theoretical and experimental study

Many works have been performed on heated vertical rectangular open-ended channels. Whilst in most cases, thermal fields are quite well predicted or reproducible, there were often large unexplained variations in the experimental flow rate for apparently the same conditions. An experimental and theoretical investigation has therefore been carried out to identify the effect of external thermal stratifications on the flow rate. Four values of steady and uniform heat flux, equivalent to Rayleigh numbers between 2.9×104 and 1.6×108 were imposed experimentally either on one or both sides of a vertical rectangular channel, with various ambient thermal gradients external to the channel. It was observed that the mass flow rate was significantly reduced as the positive upward, external thermal gradient increased. A theoretical model of the phenomenon was also developed. There is an excellent agreement between the theoretically predicted and experimentally measured mass flow rates. This clearly highlights that external temperature distributions are key driving factors and their influence is accurately quantified in this work.

Synoptic Control of Convective Rainfall Rates and Cloud-to-Ground Lightning Frequencies in Warm-Season Mesoscale Convective Systems over North China

Abstract This study examines whether environmental conditions can control convective rainfall rates and cloud-to-ground (CG) lightning frequencies in mesoscale convective systems (MCSs) over north China (NC). A total of 60 identified MCSs over NC during June–August of 2008–13 were classified into 4 categories based on their high/low convective rainfall rates (HR/LR) and high/low CG lightning frequencies (HL/LL) (i.e., HRHL, HRLL, LRHL, and LRLL MCSs). MCSs with HR (HL) occurred most frequently in July (August), while those with LR or LL occurred most frequently in June; they followed closely seasonal changes. All MCSs were apt to form during afternoon hours. HRLL MCSs also formed during evening hours while HRHL MCSs could occur at any time of a day. A composite analysis of environmental conditions shows obvious differences and similarities among the HRHL, HRLL, and LRLL categories, while the LRHL MCSs exhibited little differences from the climatological mean because of its small sample size. Both the HRHL and HRLL MCSs occurred in the presence of upper-level anomalous divergence, a midlevel trough, and the lower-tropospheric southwesterly transport of tropical moist air. In contrast, LRLL MCSs took place as a result of daytime heating over mountainous regions, with little midlevel forcing over NC. The HRHL, HRLL, LRHL, and LRLL categories exhibited orders of the highest-to-smallest convective available potential energy and precipitable water but the smallest-to-largest convective inhibition and lifted indices. It is concluded that environmental conditions determine to some extent convective rainfall rates and CG lightning activity, although some other processes (e.g., cloud microphysics) also play certain roles, especially in CG lightning production.

Analysis on ventilation pressure of fire area in longitudinal ventilation of underground tunnel

In order to solve the problem of ventilation pressure loss in the fire area under the fire condition, the wind pressure loss model of the fire area is established based on the thermodynamic equilibrium relation. The semi-empirical calculation formula is obtained by using the model experiment and CFD simulation. The validity of the formula is verified. The results show that the ventilation pressure loss in the fire zone is proportional to the convective heat release rate at the critical velocity, which is inversely proportional to the upstream ventilation velocity and the tunnel cross-sectional area. The proposed formula is consistent with the law of the tunnel fire test fitting formula that results are close, in contrast, the advantage lies in a clear theoretical basis and ventilation velocity values. The resistance of road tunnel ventilation system is calculated accurately and reliably, and then an effective emergency ventilation operation program is developed. It is necessary to consider the fire zone ventilation pressure loss. The proposed ventilation pressure loss formula can be used for design calculation after thorough verification.

Heat flux measurement analysis from thin film gauge in convective heat transfer mode

In many research activities related to the heated environment near the wall or surface, measurement of transient surface temperature and determination of convective heating rate is one of the most important tasks. Since the effective measurement time available for the regime to enumerate is very small, it is essential to use temperature detectors with highly sensitive, precise and instantaneous temperature measurement properties. Thin film gauges with these properties are best suited for such short duration transient surface temperature measurements. This study focuses on the establishment of new calibration technique in convection heat transfer mode. A fabricated calibration set-up is used to supply the heat flux to the thin film gauge, which is in-house built with platinum as sensing element and quartz as an insulating substrate. The heat load applied on the thin film gauge is of impact or step type. The deduction of heat flux value is carried out with recorded transient temperature data. Moreover, the numerical analysis is also carried out to get the heat flux values. The authenticity of the experimental set up and thin film gauge effectiveness is supported by the excellent agreement of the experimental and numerical results.

Spatial Analysis of Nanofluidic-Embedded Biosensors for Wash-Free Single-Nucleotide Difference Discrimination.

In this work, we demonstrate that the analysis of spatially resolved nanofluidic-embedded biosensors permits the fast and direct discrimination of single-nucleotide difference (SND) within oligonucleotide sequences in a single step interaction. We design a sensor with a linear dimension much larger than the channel depth in order to ensure that the reaction over the whole sensor is limited by the convection rate. Thus, the targets are fully collected, inducing a nonuniform spatial hybridization profile. We also use the nanoscale height of the channel, which enables us to minimize the amount of labeled molecules flowing over the sensor and hence to reduce the fluorescence background, to carry out real-time hybridization detection by fluorescence microscopy. Taken together, these design rules allow us to show that the spatial hybridization profile depends on the duplex affinity, and we speculate that the on and off-rate constants can be inferred during target injection, which is not possible in local analysis where the dissociation step through rinsing must be conducted. We finally manage to discriminate a GT mismatch on a microRNA sequence by optimizing the interaction temperature and the probe design after a few minutes of interaction in a single step protocol. This work may be applied to any biosensing transduction scheme with spatial resolution, e.g., surface plasmon resonance imaging, integrated into nanofluidic channels for applications where high oligonucleotide sequence selectivity and short analysis times are required.

On the Utility (or Futility) of Using Stable Water Isotopes to Constrain the Bulk Properties of Tropical Convection

AbstractAtmospheric water‐vapor isotopes have been proposed as a potentially powerful constraint on convection, which plays a critical role in Earth's present and future climate. It is shown here, however, that the mean tropical profile of HDO in the free troposphere does not usefully constrain the mean convective entrainment rate or precipitation efficiency. This is demonstrated using a single‐column analytical model of atmospheric water isotopes. The model has three parameters: the entrainment rate, the precipitation efficiency, and the distance that evaporating condensates fall. At a given relative humidity, the possible range of HDO is small: its range is comparable to both the measurement uncertainty in the mean tropical profile and the structural uncertainty of a single‐column model. Therefore, the mean tropical HDO profile is unlikely to add information about convective processes in a bulk‐plume framework that cannot already be learned from relative humidity alone.

Heating and Moistening of the MJO during DYNAMO in ECMWF Reforecasts

Reforecasts produced by the ECMWF Integrated Forecast System (IFS) were used to study heating and moistening processes associated with three MJO events over the equatorial Indian Ocean during the Dynamics of the Madden–Julian Oscillation (DYNAMO) field campaign. Variables produced by and derived from the IFS reforecast (IFS-RF) agree reasonably well with observations over the DYNAMO sounding arrays, and they vary smoothly from the western to eastern equatorial Indian Ocean. This lends confidence toward using IFS-RF as a surrogate of observations over the equatorial Indian Ocean outside the DYNAMO arrays. The apparent heat source Q1 and apparent moisture sink Q2 produced by IFS are primarily generated by parameterized cumulus convection, followed by microphysics and radiation. The vertical growth of positive Q1 and Q2 associated with the progression of MJO convection can be gradual, stepwise, or rapid depending on the event and its location over the broader equatorial Indian Ocean. The time for convective heating and drying to progress from shallow (800 hPa) to deep (400 hPa) can be &lt;1 to 6 days. This growth time of heating and drying is usually short for convective processes alone but becomes longer when additional microphysical processes, such as evaporative moistening below convective and stratiform clouds, are in play. Three ratios are calculated to measure the possible role of radiative feedback in the MJO events: amplitudes of radiative versus convective heating rates, changes in radiative versus convective heating rates, and diabatic (with and without the radiative component) versus adiabatic heating rates. None of them unambiguously distinguishes the MJO from non-MJO convective events.

The dynamics of miscible viscous fingering from onset to shutdown

We examine the full ‘life cycle’ of miscible viscous fingering from onset to shutdown with the aid of high-resolution numerical simulations. We study the injection of one fluid into a planar two-dimensional porous medium containing another, more viscous fluid. We find that the dynamics are distinguished by three regimes: an early-time linearly unstable regime, an intermediate-time nonlinear regime and a late-time single-finger exchange-flow regime. In the first regime, the flow can be linearly unstable to perturbations that grow exponentially. We identify, using linear stability theory and numerical simulations, a critical Péclet number below which the flow remains stable for all times. In the second regime, the flow is dominated by the nonlinear coalescence of fingers which form a mixing zone in which we observe that the convective mixing rate, characterized by a convective Nusselt number, exhibits power-law growth. In this second regime we derive a model for the transversely averaged concentration which shows good agreement with our numerical experiments and extends previous empirical models. Finally, we identify a new final exchange-flow regime in which a pair of counter-propagating diffusive fingers slow exponentially. We derive an analytic solution for this single-finger state which agrees well with numerical simulations. We demonstrate that the flow always evolves to this regime, irrespective of the viscosity ratio and Péclet number, in contrast to previous suggestions.

Effect of Thermal Convection on Density Segregation in Binary Granular Gases with Dissipative Lateral Walls**Supported by the National Natural Science Foundation of China under Grant No 11404104, and the Natural Science Foundation of Hubei Province of China under Grant No 2014CFC1127.

Molecular dynamics simulations are employed to investigate the effect of thermal convection induced only by dissipative lateral walls on density segregation of the strongly driven binary granular gases under low gravity conditions. It is found that the thermal convection due to dissipative lateral walls has significant influence on the segregation intensity of the system. The dominant factor in determining the degree of segregation achieved by the system is found to be the relative convection rate between differing species. Moreover, a qualitative explanation is proposed for the relationship between the thermal convection due to dissipative lateral walls and the observed segregation intensity profiles.

Increasing potential for intense tropical and subtropical thunderstorms under global warming

Intense thunderstorms produce rapid cloud updrafts and may be associated with a range of destructive weather events. An important ingredient in measures of the potential for intense thunderstorms is the convective available potential energy (CAPE). Climate models project increases in summertime mean CAPE in the tropics and subtropics in response to global warming, but the physical mechanisms responsible for such increases and the implications for future thunderstorm activity remain uncertain. Here, we show that high percentiles of the CAPE distribution (CAPE extremes) also increase robustly with warming across the tropics and subtropics in an ensemble of state-of-the-art climate models, implying strong increases in the frequency of occurrence of environments conducive to intense thunderstorms in future climate projections. The increase in CAPE extremes is consistent with a recently proposed theoretical model in which CAPE depends on the influence of convective entrainment on the tropospheric lapse rate, and we demonstrate the importance of this influence for simulated CAPE extremes using a climate model in which the convective entrainment rate is varied. We further show that the theoretical model is able to account for the climatological relationship between CAPE and a measure of lower-tropospheric humidity in simulations and in observations. Our results provide a physical basis on which to understand projected future increases in intense thunderstorm potential, and they suggest that an important mechanism that contributes to such increases may be present in Earth's atmosphere.

Improvement of fire-tube boilers calculation methods by the numerical modeling of combustion processes and heat transfer in the combustion chamber

This paper presents the results of study on determination of degree and nature of influence of operating conditions of burner units and flare geometric parameters on the heat transfer in a combustion chamber of the fire-tube boilers. Change in values of the outlet gas temperature, the radiant and convective specific heat flow rate with appropriate modification of an expansion angle and a flare length was determined using Ansys CFX software package. Difference between values of total heat flow and bulk temperature of gases at the flue tube outlet calculated using the known methods for thermal calculation and defined during the mathematical simulation was determined. Shortcomings of used calculation methods based on the results of a study conducted were identified and areas for their improvement were outlined.

Methods for Estimating 2D Cloud Size Distributions from 1D Observations

Abstract The two-dimensional (2D) size distribution of clouds in the horizontal plane plays a central role in the calculation of cloud cover, cloud radiative forcing, convective entrainment rates, and the likelihood of precipitation. Here, a simple method is proposed for calculating the area-weighted mean cloud size and for approximating the 2D size distribution from the 1D cloud-chord lengths measured by aircraft and vertically pointing lidar and radar. This simple method (which is exact for square clouds) compares favorably against the inverse Abel transform (which is exact for circular clouds) in the context of theoretical size distributions. Both methods also perform well when used to predict the size distribution of real clouds from a Landsat scene. When applied to a large number of Landsat scenes, the simple method is able to accurately estimate the mean cloud size. As a demonstration, the methods are applied to aircraft measurements of shallow cumuli during the Routine ARM Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) campaign, which then allow for an estimate of the true area-weighted mean cloud size.

Sublimation pit distribution indicates convection cell surface velocities of ∼10 cm per year in Sputnik Planitia, Pluto

The ∼106 km2 Sputnik Planitia, Pluto is the upper surface of a vast basin of nitrogen ice. Cellular landforms in Sputnik Planitia with areas in the range of a few × 102–103 km2 are likely the surface manifestation of convective overturn in the nitrogen ice. The cells have sublimation pits on them, with smaller pits near their centers and larger pits near their edges. We map pits on seven cells and find that the pit radii increase by between 2.1 ± 0.4 × 10−3 and 5.9 ± 0.8 × 10−3 m m−1 away from the cell center, depending on the cell. This is a lower bound on the size increase because of the finite resolution of the data. Accounting for resolution yields upper bounds on the size vs. distance distribution of between 4.2 ± 0.2 × 10−3 and 23.4 ± 1.5 × 10−3 m m−1. We then use an analytic model to calculate that pit radii grow via sublimation at a rate of 3.6−0.6+2.1×10−4 m yr−1, which allows us to convert the pit size vs. distance distribution into a pit age vs. distance distribution. This yields surface velocities between 1.5−0.2+1.0 and 6.2−1.4+3.4 cm yr−1 for the slowest cell and surface velocities between 8.1−1.0+5.5 and 17.9−5.1+8.9 cm yr−1 for the fastest cell. These convection rates imply that the surface ages at the edge of cells reach ∼4.2–8.9 × 105 yr. The rates are comparable to rates of ∼6 cm yr−1 that were previously obtained from modeling of the convective overturn in Sputnik Planitia (McKinnon et al., 2016). Finally, we investigate the surface rheology of the convection cells and estimate that the minimum ice viscosity necessary to support the geometry of the observed pits is of order 1016–1017 Pa s, based on the argument that pits would relax away before growing to their observed radii of several hundred meters if the viscosity were lower than this value.

Momentum Flux of Convective Gravity Waves Derived from an Offline Gravity Wave Parameterization. Part I: Spatiotemporal Variations at Source Level

Abstract Spatiotemporal variations in momentum flux spectra of convective gravity waves (CGWs) at the source level (cloud top), including nonlinear forcing effects, are examined based on calculations using an offline version of CGW parameterization and global reanalysis data for a period of 32 years (1979–2010). The cloud-top momentum flux (CTMF) is not solely proportional to the convective heating rate but is affected by the wave-filtering and resonance factor and background stability and temperature underlying the convection. Consequently, the primary peak of CTMF is in the winter hemisphere midlatitudes, associated with storm tracks, where a secondary peak of convective heating exists, whereas the secondary peak of CTMF appears in the summer hemisphere tropics and intertropical convergence zone (ITCZ), where the primary peak of convective heating exists. The magnitude of CTMF fluctuates largely with 1-yr and 1-day periods in major CTMF regions. At low latitudes and Pacific storm-track regions, a 6-month period is also significant, and the decadal cycle appears in the southern Andes. The equatorial eastern Pacific region exhibits a substantial interannual to decadal scale of variabilities. The correlation between convective heating and the CTMF is relatively lower in the equatorial region than in other regions. The CTMF in 10°N–10°S during the period of the pre-Concordiasi campaign approximately follows a lognormal distribution but with a slight underestimation in the tail of the probability density function. In Part II, the momentum flux and drag of CGW in the stratosphere will be examined.

Manufacture of Copper Foils for the Current Collector of Lithium-Ion Batteries By Electrochemical Deposition

Manufacture of copper foils by electrochemical deposition is a mature and indispensable technique in the modern industry, and one of the important products is the copper clad laminate for printed circuit board industry. In recent years, as the rapid increase in electric cars industry, the demand for Cu foils acting as the current collector of negative electrodes for lithium-ion batteries (LIBs) surges strikingly. Nonetheless, the method to produce Cu foils for LIBs could not be conducted by electrochemical deposition but by rolling, since the rolled copper foils provides a double side smooth surface, which is crucial to achieve good capacity retention rate of LIBs. Moreover, rolled copper foils possess excellent mechanical properties such as tensile strength to ensure the foils pass through the following roll-to-roll coating process without fracture. Unfortunately, rolled Cu foils are much costly in comparison with the electroplating, especially for thin foils since it require more times of rolling and annealing the copper ingot. Meanwhile, the surface roughness of electrodeposited Cu foils on both sides is distinctively different by the conventional electrolyte composition, which is known to deteriorate the capacity retention rate of LIBs. Consequently, we introduced several organic additives that had been applied in copper damascene plating into copper foils plating, and attempted to manufacture Cu foils with optimal quality that can meet the requirements to be adopted into LIBs. Unlike damascene process, the target of using additives is not to change the deposition rate of copper, but to modify the surface morphology and strengthen the structure of the deposited copper. In addition, the applied current density of Cu foil plating usually ranges from 500 to 1000 mA·cm-2, which is 20 times more than damascene plating. Correspondingly, the convection rate in the plating bath ought to be extremely high to make sure the limiting current density higher than the applied current density. Therefore, the electrochemical behavior of each additives has yet to be studied under such high current densities and strong flow-rate environments. Last but not least, the degradation rate of the organic additives may be much faster since the current density is much higher. To produce Cu foils with consistent quality, understanding the bath aging problem and the proper method to maintain the bath is very important. In this research, the effects of the selected additives on the structure and surface morphology of deposited copper, the electrochemical behavior of additives under high current density, and the full consideration to solve the bath aging issue will be presented. Ultimately, a proper solution to manufacture Cu foils for LIBs by electrochemical deposition will be proposed.

Insight into mass transfer by convective diffusion in anaerobic granules to enhance biogas production

Mass transfer in anaerobic granule is crucial for efficient biogas production, but so far the fundamental understanding remains poor. This study aims at gaining an insight into convective diffusion to enhance mass transfer within small (0.5–1mm), medium (1.5–2mm) and large (3–3.5mm) granules. The convective diffusion rates (FCD) of granules at a superficial liquid velocity of 3m/h were 2–3 magnitudes greater than molecular diffusion rates (FMD), and significantly enhanced the biogas production rate of small, medium and large granules by 4, 1.5 and 1.3 folds. The granules were permeable in nature as fluid collection efficiency (η) of small, medium and large granules of 0.97, 0.89 and 0.58 indicated, and were of cluster–cluster formation as fractal dimension (Df) revealed. The large granules possess best mass transfer condition and highest biogas production rate because they had highest FCD due to the biggest permeable area despite lowest η. This work for the first time elaborates the important roles of internal structures in terms of permeability and fractal dimension on the convective mass transfer in anaerobic granules, and it also highlights the importance of molecular diffusion. The results could facilitate upgrading the understanding of mass transfer process in anaerobic granules to enhance biogas production.

Effects of a three-lobe swirl generator on the thermal and flow fields in a heat exchanging tube: An experimental and numerical approach

The current experimental study primarily focuses on the effects of an injected swirling flow on the thermal performance of the test tube. The swirl generator is a helically twisted tube with a three-lobe cross section. To evaluate the thermal performance of the test tube equipped with the swirl generator, the Nusselt number and the friction factor are considered as the target outcomes. The study is carried out for different values of twist-angle (90⩽θ⩽360) and length (1⩽l⩽4) as the main geometrical parameters of the swirl generator, and the Reynolds number varies from 5000 to 30000. The experimental study is accompanied by a comprehensive Large Eddy Simulation (LES). The generated swirling flow and its dissipation rate along the test tube are numerically investigated in details. The numerical results clarify the potential of the swirl generator to enhance the convection rate. The Smagorinsky approach is used to model the effects of the sub-grid scales on the flow field. The simulation is performed using an open-source CFD code named OpenFOAM. The results show that the swirl generator leads to a significant enhancement in Nusselt number accompanied by an acceptable increase in the friction factor.

Thermal performance enhancement in a heat exchanging tube via a four-lobe swirl generator: An experimental and numerical approach

The effects of a new swirl generator on thermal and flow fields in a heat exchanging tube are investigated experimentally and numerically. The swirl generator is a tube with a four-lobe cross section helically twisted with four different angles (θ=90, 180, 270 and 360). In the experiments, the heat transfer rate and pressure drop are measured as the main outcomes to extract the role of swirl generator on the thermal performance of the test tube. The experimental study is performed for different Reynolds numbers in the range of 6000–30,000. The experimental results reveal that the swirl generator makes an enhancement up to 87% in the heat transfer rate and an increase up to 48% in the pressure drop. The experimental results are supported by Large Eddy Simulation (LES) of the generated swirling flow. The study applies open-source CFD code named OpenFOAM. It is proved that the swirl generator creates an intense swirling flow at the tube inlet. The numerical results show that the high tangential and axial velocity components, near the tube wall, are the main reason of the better convection rate for the tube equipped with the swirl generator.