Heat Transfer Coefficient Of Flow Research Articles

Flow patterns and heat transfer coefficients using a rotational diffuser coupled with a radiant floor cooling

In this research, we explore the characteristics of an HVAC system consisting of a rotational floor diffuser with an underfloor plenum, coupled with a radiant floor cooling. Numerical simulations are performed using two different meshes. Firstly, we solve the diffuser outflow entering into the room by means of a very detailed mesh.Secondly, the whole room with the radiant floor using as input the flow obtained from the former diffuser mesh. Besides, we analyze the flow visualizations that emerge near the rotational diffuser, and we demonstrate that there are two different regimes depending on the flow rate: (i) displacement ventilation that works as a radial flow, and (ii) a vertical jet with a very active mixing process for low or high flow rates, respectively. We calculate the Nusselt number versus the Reynolds number and collapse into a linear fit with different slopes below and above the Reynolds number 16,000, a limit that coincides with the previously observed change in flow patterns. Therefore, the type of flow patterns created near the diffuser only affect the level of heat transfer, but not its linear dependence. Finally, we propose another non-linear general adjustment of the Nusselt number as a function not only of Reynolds number but of the temperature ratios for all cases considered (isothermal and non-isothermal). This last non-linear regression model shows us that only inertia controls heat transfer and independence on the temperature ratio for Reynolds numbers lower than 16,000.

Experimental measurement of heat transfer coefficient and mass of deposited CaSO4 in subcooled flow boiling condition

Fouling is a common, fundamental and costly problem in heat transfer systems, which reduces thermal efficiency of equipment, increases the energy loss and causes strong damage to the heat transfer equipment in various industries. The main causes of fouling on the heat transfer surfaces are salts with inverse temperature-solubility in the fluid which calcium sulfate is one of the most important of them. In this paper, the effect of calcium sulfate fouling on the heat transfer coefficient in subcooled flow boiling was investigated. The fouling mass of calcium sulfate on the heat transfer surface was also calculated. In the experiments carried out in this study, flow rate (2.5–11.5 l/min), solution concentration (1.75–2.2 g/l), bulk fluid temperature (55–75 ℃), and heat flux (8-95 kW/m2) were variables at the mentioned ranges. The results showed that the maximum deviation in the uncertainty analysis was related to the difference between the inlet and outlet temperature of the fluid, followed by the temperature difference between the wall temperature and the bulk fluid temperature. Also, the analysis of the experimental data revealed that increasing the salt concentration, the bulk temperature, and the heat flux of the solution, the mass of deposited calcium sulfate on the heat transfer surface increases with time, resulting in a decrease in the heat transfer coefficient. Careful analysis of the experimental data also showed that the solution concentration has more important role than the heat flux and the fluid bulk temperature in fouling formation.

Forced Convection upon Heat Sink of AL-Cu for Design Optimization by Experimental and CFD Analysis for cooling of ICs in CPU.

A heat sink device is used with specific power input at 100V and 20W by the heater attached at the base plate of copper and then obtaining the average temperature of Heat sink by the help of 10 thermocouples .Two specimens of heat sinks were designed and were tested for mass flow rate and heat transfer coefficient. With base of 1.5mm&2.5mmtip thickness and another specimen with dimensions as tip0.5mm and1.00mmbase thickness are used By experimenting and CFD simulations,optimization of heat sink design was done.Then correlation and Validation foe both the specimen was done and were found satisfactory results.

Experimental characterization of magnetic field effects on heat transfer coefficient and pressure drop for a ferrofluid flow in a circular tube

In this paper, an experimental study is performed to characterize the effect of constant and alternative magnetic fields on pressure drop and heat transfer coefficient for a ferrofluid in laminar flow in a circular straight tube. The ferrofluid considered in this study is prepared using Fe3O4 nanoparticles. The verification of the size of nanoparticles is accomplished using TEM images and DLS distribution. A two-step preparation method is used to produce a ferrofluid with 0.5 and 1 wt%. The ferrofluid is stabilized using a surfactant and ultrasonic waves. The Zeta potential is employed to evaluate the stability of the ferrofluid, and the VSM to check its magnetization property. An uncertainty analysis is also performed where a maximum uncertainty of 1.8% is obtained. Experimental results are first compared with those of Shah and London equation for pure water as the working fluid. The Nusselt (Nu) number is enhanced using a ferrofluid instead of pure water for various Reynolds (Re) numbers. Next, two constant and alternative magnetic fields of 770 and 1300 G with four different Patterns are applied. The Nu number is improved by using a constant magnetic field. It is found that the Nu number is enhanced by 11.85 and 14.8% by using an alternative magnetic field with a frequency of 10 and 100 Hz, respectively. Further increase in the frequency (above 100 Hz up to 1000) does not lead to a positive outcome.

Flow-pattern based prediction of flow boiling heat transfer in horizontal tubes with circumferentially varying heat flux

In order to describe the heat transfer coefficient during flow boiling in horizontal tubes with circumferentially varying heat flux, flow pattern-based models from the literature are validated and adapted using measurement data of the local and the circumferentially averaged heat transfer coefficient. Such boundary conditions occur when the wall temperature at the circumference is constant and the tube is partially wetted. The most important adaption is the calculation of the nucleate boiling contribution as a function of the local heat flux and not of the circumferentially averaged heat flux. Further adjustments concern the heat transfer coefficient in the dryout regime and during wavy flow. The database used to validate the method encompasses heat transfer coefficients of flow boiling of CO2 at saturation pressures from 10 bar to 60 bar, mass fluxes from 25 kg m-2 s-1 to 300 kg m-2 s-1, local heat fluxes up to 230 kW m-2, and vapor qualities from 10 % to 99 %. By applying the proposed adjustments, the quality of the prediction of the data is improved from 56 % to more than 80 % of the data within an error interval of ± 30 %. In addition, the comparison of local heat transfer coefficients provides a validation of the basic structure of the model and identifies the potential and the need for further refinement.

Heat transfer and flow regimes during counter-flow steam condensation in flattened-tube air-cooled condensers

Experimental results for counter-flow steam condensation in a 5.7 m-long air-cooled condenser tube with a flattened-tube cross section are presented. The tube is inclined at upward inclination angles from 0.5° to 40°, with both the vapor inlet and liquid outlet at the lower end of the tube. The effect of inclination angle on flow regimes, void fraction, capacity and heat transfer coefficient is presented. In addition, a water-cooled test section provides local steam-side heat transfer coefficient along the tube circumference at increased accuracy to that determined in the air-cooled test section. The range of condensation pressures tested is 88–120 kPa and all tests have a mass flux of less than 4.2 kg m−2 s−1. Stratified flow is found for nearly all conditions and locations in the condenser. Flooding of this stratified condensate layer is found for tube inclination angles of 5° and lower. This flooding is found to reduce the condenser capacity. The results are compared to those for co-current flow in the same condenser tube. Capacity is found to be unaffected by the flow configuration (counter-flow vs. co-current) when flooding does not occur. Steam-side heat transfer coefficient is also found to be unaffected by flow configuration for all conditions tested.

Two-phase flow pattern and heat transfer coefficients of R245fa/R134a under non-uniform heat flux

The non-uniform distribution of the heat flux commonly occurs in systems where vapor-liquid phase changes, such as nuclear reactors, and aerospace thermal control systems. This poses a great challenge on the study of pressure drop, heat transfer coefficient, and flow pattern prediction. In addition, flow patterns and heat transfer characteristics are usually affected by differences in fluid properties (viscosity, density, and surface tension), thermodynamic conditions (pressure, temperature), and geometric dimensions. At present, most of the researches on non-uniform heat flux are concentrated in systems with pure working fluids. However, compared to the pure working fluid, the mixed working fluid, particularly the zeotropic working fluid can improve the cycle efficiency and has great application potential, chiefly due to the temperature glide. There are few studies on the two-phase flow pattern and heat transfer characteristics of the zeotropic working fluid under non-uniform heat flux. Aiming at the problem of vapor-liquid phase change of zeotropic working fluid under non-uniform heat flux boundary conditions, a two-phase flow boiling experimental system in a horizontal tube with a 10 mm inner diameter under non-uniform heat flow was established. The studied zeotropic working fluid is R245fa/R134a with a mass fraction of 0.7:0.3. Experiments were performed at conditions where the mass flux ranges from 175 to 373 kg/(m2 s), while the heat flux ranges from 9.95 to 47.57 kW/m2. Using a high-speed camera and image processing technology, the gray values of the observed bubble flow, plug flow, stratified flow, and annular flow were analyzed, and the flow patterns under both non-uniform and uniform heat flux were demonstrated. Effects of the vapor quality, mass flux, heat flux and saturation temperature on the two-phase heat transfer coefficient were analyzed. And on the basis of experimental data, the prediction accuracy of four commonly used correlations was evaluated. The results show that the gray value of bubble flow and plug flow fluctuate widely, while the gray value fluctuation range of stratified flow and annular flow is relatively small. The typical flow pattern under non-uniform heat flux is the same as flow pattern under uniform heat flux. With the same amount of the additional heat, under the condition of non-uniform heat flux, the initial vapor quality of annular flow is advanced, and the proportion of the annular flow is larger than the non-annular flow. The main reason for this phenomenon is that the flow instability caused by non-uniform heat flux accelerates the transition of intermittent flow to annular flow. In addition, the heat transfer coefficient changes little at the lower vapor quality, and the heat transfer coefficient of the intermittent flow region is independent of vapor quality. In the annular flow region with higher vapor quality, the heat transfer coefficient increases with the increase of vapor quality. The heat transfer coefficient increases with the increase of mass flux and heat flux. The saturation temperature has little effect on the heat transfer coefficient in the convection boiling region and has a certain influence in the nucleate boiling region. Furthermore, the prediction ability of the four correlations is poor in the non-annular flow region. Relatively, the prediction accuracy of the Sun & Mishima correlation is the highest in the annular flow region.

Experimental research of supersonic flow heat transfer in the wake of a backward-facing step

The results of an experimental study of heat transfer for a supersonic flow behind a backward-facing step are presented. Input flow Mach number was 2.2, Reynolds number was over 20 million when calculated with the use of the dynamic boundary layer length from the critical section to the exit section of the nozzle. The height of the step ranged from 8 to 14 mm. The thickness of dynamic boundary layer for plane model flow was about 6 mm in the region of nozzle exit section. The heat transfer coefficient and adiabatic wall temperature for the wake flow behind the step have been analysed in comparison with the plane model flow. The experiment was made with the use of chromel-kopel thermocouples with thermal compensation of cold junction, stagnation and static pressure meters, NI LabView powered programs of experimental automation. The graphs of the wall temperature, stagnation flow temperature, adiabatic wall temperature, the stagnation and static pressure, the distribution of the temperature recovery coefficient and the relative Stanton number along the model length are presented.

Boiling heat transfer coefficient and pressure drop of R1234yf flow inside smooth flattened tubes: An experimental study

In this study, the boiling flow of R1234yf inside flattened tubes is experimentally investigated to determine the heat transfer coefficient and pressure drop. The experiments were carried out on a round tube of 8.2 inner diameter and three flattened tubes with internal heights of 6.2, 5.1 and 2.8 (aspect ratios of 1.5, 2, and 4), with mass velocities between 110 and 410 kg/m2s, and vapor qualities between 0.1 and 0.9. The experimental data were analyzed to determine the effect of vapor quality, mass velocity, and flattening the tubes on the heat transfer coefficient and pressure drop. Also, the performance evaluation criterion (PEC) was used to investigate the effect of flattening on the heat transfer coefficient and pressure drop simultaneously. The results showed that for the flattened tubes with 1.5, 2, and 4 aspect ratios, the heat transfer coefficient enhances up to 53%, 99%, and 154%; while the pressure drop increases up to 54%, 167%, and 270%, respectively, compared to those of the round tube. In addition, according to the results, the enhancement factor increases with the aspect ratio, and the tube with the aspect ratio of 2 showed the highest PEC at high mass velocities.

The effect of twisted tape inserts on heat transfer and pressure drop of R1234yf condensation flow: An experimental study

This paper deals with condensation flow inside plain and twisted tape inserted (TTI) tubes with diameter and length of 8.7 mm and 700 mm, respectively. R1234yf, identified as a viable alternative for R134a with low global warning potential (GWP), is examined as the working fluid. The heat transfer coefficient and the pressure drop of the flow are measured in different mass velocities and vapor qualities ranging 160–310 kg m−2 s−1 and 0.12–0.84, respectively. A well-equipped test rig consisting of a test condenser and other necessary equipment is employed to precisely adjust the test conditions. Experimental results for the plain tube are compared with some well-known correlations. As a result, Shah and Souza et al. equations are the most reliable equations to predict the flow heat transfer coefficient and its pressure drop, respectively. Different twisted tape inserts with three twist ratios of 6, 9, and 12 are exploited to study the effect of twisted tape geometry. The results indicate that up to 42% and 235% increment in the heat transfer coefficient and the pressure drop, respectively, is associated with implementing twisted tape inserts. In addition, it was shown that, among some correlations proposed previously in the literature, the experimental heat transfer coefficient and pressure drop in TTI tubes can be predicted by Akhavan Behabadi et al. and Hejazi et al. correlations with reasonable accuracy. According to the results, the twist ratio of 6 gives the highest increase in the heat transfer coefficient, while the ratio of 9 is associated with the highest overall enhancement ratio.

Experimental investigation of heat transfer during flow condensation of HC-R600a based nano-refrigerant inside a horizontal U-shaped tube

This experimental study investigates the effect of MWCNT (multi-walled carbon nanotube) nanoparticles on condensation heat transfer characteristics of R600a/oil mixture inside a horizontal U-shaped tube. The experiments are organized in three parts: (i) pure refrigerant flow, (ii) refrigerant-oil mixture flow with oil mass fraction of 1%, and (iii) R600a/oil/MWCNT nano-refrigerant flow with nanoparticle mass fractions of 0.1, 0.2, and 0.3%. The condenser consists of two 135 cm straight sections and a U-bend with the inner diameter of 8.7 mm and the curve ratio of 21 installed in a 6 cm polyethylene shell. The tests are carried out in a wide range of operating conditions, including condensation pressure of 510–630 kPa, mass velocity of 140, 187, 233, and 280 kg/m2s, and vapor quality of 0.04–0.75. The results show that at low vapor quality, adding lubricating oil into the refrigerant improves the heat transfer coefficient of the mixture in comparison to the pure refrigerant, while this trend is reversed at medium and high vapor quality due to the lubricating oil impact on the condensation liquid film. In addition, the nano-refrigerant flow heat transfer coefficient increases with mass velocity while there is a critical vapor quality in which the local coefficient becomes maximum. Based on the results, using 0.3% of MWCNT causes maximum local heat transfer enhancement up to 68.2%, in comparison to the pure refrigerant. Heat transfer enhancement by adding nanoparticles is more effective at low and intermediate vapor quality.

Operational behavior and heat transfer in a thermosiphon desorber at sub-atmospheric pressure. Part I: The model

The thermosiphon desorber or bubble pump is advantageous in absorption cooling devices, since the processes of refrigerant desorption and solution pumping is combined in one hermetical unit. This supersedes the necessity of a mechanical solution pump. In the application with NH3/H2O the thermosiphon desorber typically operates at a pressure of around 15 bar with a liquid vapor density ratio in the range of 102, which is in a well-known regime of two phase flow. Nevertheless, for the application of thermosiphon desorbers in H2O/LiBr absorption chillers, which are commonly operated at a pressure below 0.1 bar with the liquid vapor density ratio in the range of 104, there is a lack of heat transfer correlations for two-phase flow.First attempts to fill this gap of flow boiling heat transfer correlations in the thermosiphon desorber at sub-atmospheric pressures is presented in this paper. A model is formed by solving simultaneously the mass, energy, and momentum equations. The well-known correlations for predicting single-phase and two-phase flow heat transfer coefficient and frictional pressure drop have been reviewed to find a possibility for applying them to the thermosiphon desorber. The mass flow rate and heat transfer behavior with the different flow length of the riser tube and with changing the pressure has been theoretically studied in the model. For verification, the model has been compared to experimental data using pure water. This will be presented in the second part of the paper.

Experimental research on subcooled boiling heat transfer for natural circulation flow in a vertical 3 × 3 rod bundle

To meet the requirement of passive safety, natural circulation has been applied in cooling the nuclear reactor core. In comparison with the great successes in predicting subcooled boiling in simple geometries such as pipes, annuli and rectangular channels, few researches have been performed for rod bundle. We performed subcooled boiling heat transfer experiments in a vertical 3 × 3 rod bundle under upward natural circulation flow condition. The experiments were performed under pressure from 0.2 MPa to 1.0 MPa, mass flux from 162 to 411 kg/m2/s, heat flux from 31 to 271 kW/m2, local subcooling from 0 to 25 °C and thermodynamic vapor quality from −0.05 to 0. The experimental results were compared with the predictions of 14 subcooled boiling correlations. The comparisons showed that the new Shah correlation and Thom correlation can accurately predict the heat transfer coefficient of natural circulation flow in the rod bundle within a deviation of 30%. The average deviations of new Shah correlation and Thom correlation are 3.98% and 2.54% respectively. According to the discussion of three kinds of correlation, we found that empirical correlations can better predict the subcooled boiling than semi-empirical correlations.

Experimental study on shell side heat transfer characteristics of two-phase propane flow condensation for vertical helically baffled shell-and-tube exchanger

Vertical helically baffled shell-and-tube heat exchangers (HBHXs) occupy smaller ground areas compared to horizontal HBHXs and have been used as propane condensers in liquefied natural gas (LNG) plants. The heat transfer characteristics of propane in the shell side of vertical HBHX were investigated in the present study. The flow patterns and heat transfer coefficients in the shell side of a vertical HBHX test sample were obtained, and the results were compared with the existing data of the horizontal HBHX. The experimental conditions cover mass flux of 20–40 kg m−2 s−1, heat flux of 3.0∼7.0 kW m−1, and vapor quality from 0.2 to superheated. It is found that the variation trend of propane heat transfer coefficient with the increase of vapor quality in the vertical HBHX shell side is similar to that of the horizontal one. However, opposite to the horizontal HBHX, the heat transfer coefficient increases with the rise of heat flux for two-phase propane in the vertical HBHX shell side, probably arising from the influence of convection heat transfer in the liquid film. The heat transfer coefficient of two-phase propane in the vertical HBHX is 15–55% lower than that in the horizontal one, due to the thicker liquid film on tubes in the vertical HBHX. A correlation was developed to predict the heat transfer coefficient, and it agrees with 93% of experimental data within a deviation of ±20%.

Development of A Process for Predicting the Overall Heat Transfer Coefficient for Transient Heat Transfer in An Exhaust System using CFD

The analysis of heat transfer of automotive exhaust system is most important since their prominence in the design and also in the optimization phase of exhaust after treatment system.This paperdeals with the process which can be useful to predict the overall heat transfer coefficient for the transient flow of pipe in the after treatment system. This considers the convection of heat along gas flow, the convection between gas and wall, conduction through wall, radiation and of course convection to the ambient. Governing equations are obtained for the transient flow in a pipe for calculating gas temperature and wall temperature at distance x and time t. Analytical solution will be computed using CFD techniques for these governing equations. From the obtained analytical solution to the transient flow in pipe an excel tool will be developed which can be able to give the outlet temperature of the pipe in transient flow at length x and time t, total heat loss from pipe to the ambient, overall heat transfer coefficient for the pipe.

CFD-Assisted model development for estimation of hole-ablation diameter of a pressure vessel during severe accidents

To evaluate the released radioactive materials to an environment under a nuclear severe accident, it is necessary to analyze the ex-vessel phenomena. The releasing diameter is one of the most essential parameters to estimate the ex-vessel phenomena. The diameter is enlarged because the wall of a reactor vessel melts due to the high temperature of corium flow. In this study, a hole-ablation model was developed based on the one-dimensional heat balance equations for molten corium flow, crust layer, and molten layer of the reactor vessel, respectively. Moreover, the heat transfer coefficient for the situation of discharging flow was obtained using computational-fluid-dynamics. As a result, we proposed the enhancement factor, 1.57, to be multiplied by the heat transfer coefficient for an external turbulent flow. We found out that the strong effect of the critical thickness of the molten wall layer on the thicknesses of the crust layer and the molten wall layer. We suggested the relationship between the critical thickness of the molten wall layer and the ratio of the superficial velocity of the molten wall layer to that of the corium discharging flow. The proposed model was compared with the Pilch model: the mean averaged error (MAE) of the present model was 9.51%, whereas that of the Pilch model was 36.13%. In the case of the low superheat of the corium where the crust can be produced, the Pilch model without the crust formation model predicts the much larger final-hole diameter than the present model does.

Experimental and analytical study of transient convection at film flow-wall interface using infrared thermography

The convection heat transfer of transient flow usually involves transient temperature and transient heat flux at the flow-wall interface. For experimental studies on this type of convection heat transfer problems, it is difficult to take measurement at the flow-wall interface, particularly for liquid flow. A substrate with small thickness can be used. One surface is exposed to the flow, while, on the free surface, there is a thin-skin heat source providing a constant and uniform heat flux, and the temperature at the free surface is measured using infrared thermography. Then the heat transfer coefficient of the transient flow can be obtained based on the temperature measured on the free surface. Two experimental tests of water droplets impacting a water film flow are conducted using this method. We solve a 1-D transient conduction problem, and the derived solution is used to calculate the heat transfer coefficient for the two experiments. Additionally, the lumped capacitance method (LCM) and the present analytical method are compared for calculating convection heat transfer.

A Mathematical Model of Local and Average Heat Transfer in Channels with Heat Transfer Intensifiers

The expressions derived previously from the three-layer Owen model of a turbulent boundary layer and the Deissler and the van Driest models are demonstrated to be valid for predicting heat transfer coefficients in the entrance region of channels. The basic parameters in these expressions are the dynamic velocity, dimensionless viscous sublayer thickness, and dimensionless turbulent boundary layer thickness. Correlations are presented for predicting these parameters in the entrance region of a plate or circular pipe. The predicted heat transfer coefficients agree with the available data. With consideration of the fact that the friction and the heat transfer laws established by S.S. Kutateladze and A.I. Leont’ev are conservative with respect to disturbances in the turbulent boundary layer, parameters of the expressions for average heat transfer coefficients in channels with heat transfer intensifiers (such as roughness, transverse ring protrusions, and annular groves in pipe walls) were determined. In calculating friction and heat transfer, the main characteristics are the dynamic velocity and the ratio of the friction coefficient on a smooth surface to that on a surface with heat transfer intensifiers. The expression was derived for calculating the Nusselt number as a function of the Reynolds number and the friction factor. The predicted average heat transfer coefficients agree well with the experimental data and the predictions by empirical correlations. Calculations were performed in a wide range of Reynolds number (from 104 to 106) and smooth-to-intensified surface friction factor ratio (from 1.92 to 9.2). The proposed correlations can be used for predicting local heat transfer coefficients in the entrance region on a body in a flow and average heat transfer coefficients in intensified channels.

Local heat transfer of saturated flow boiling in vertical narrow microchannel

In this experimental study, saturated flow boiling in a one-side-heating vertical narrow rectangular microchannel is conducted with deionized water as the working fluid, the mass flux is in the range of 120 kg/m2s – 360 kg/m2s, the wall heat flux varies from 6 W/cm2 to 24 W/cm2 and the inlet vapor quality is 0.03 or 0.1. The bottom surface of the microchannel is constructed of two different material, one is the untreated hydrophilic silicon wafer with a contact angle of 65° ± 3°, the other is the super-hydrophilic silicon wafer deposited with a thin film of 100-nm-thickness silicon dioxide through PECVD with a contact angle less than 5°. The flow patterns in almost all experimental conditions are the annular flow and the heat transfer mechanism is dominated by convective evaporation, the heat flux transfers through the conduction and convection in the thin liquid film and evaporation at the interface between the vapor and liquid. The thinner the liquid film, the greater the heat transfer coefficient. The local dryout phenomenon is observed on the untreated hydrophilic surface while the super-hydrophilic surface can keep the liquid film uniform and restrict the occurrence of local dryout phenomenon. Through the evaluation of the correlations of heat transfer coefficient, this study proposes the modified Li and Wu [18] correlation as a formula for calculating the heat transfer coefficient of saturated flow boiling in a vertical narrow one-sided heating microchannel.

Experimental investigation on non-boiling heat transfer of two-component air-oil and air-water slug flow in horizontal pipes

Gas-liquid slug flow in horizontal pipes occurs frequently in industrial applications and its heat transfer characteristics are very important but complicated due to the intermittent flow structures. This paper aims at investigating the heat transfer mechanism of both air-oil and air-water slug flow in horizontal pipes. An experimental setup was fabricated to investigate the flow and heat transfer characteristics of air-oil and air-water slug flow under cooling conditions in horizontal pipes. The test section was made of a copper pipe with I.D. of 26 mm and a polyvinyl chloride pipe with I.D. of 63 mm using concentric geometry. The effect of flow parameters, such as liquid flow rate, gas flow rate, two-phase pressure drop multiplier, void fraction and slug frequency on heat transfer of gas-liquid slug flow was comprehensively investigated. The heat transfer coefficient of two-phase flow was significantly improved by the introduction of air and the maximum two-phase heat transfer enhancement ratio for air-water and air-oil flow were 150% and 300%, respectively. The circumferential temperature distribution and local heat transfer coefficient were also investigated. The local heat transfer coefficient at the bottom was around 25% higher than that at the top due to the uneven distribution of liquid and gas inside the pipe. Finally, a semi-empirical heat transfer correlation for gas-liquid slug flow was developed based on Reynolds and Chilton–Colburn analogies. The newly developed correlation predicts 96% of the present experimental two-phase heat transfer data within ±20% error and the mean relative deviations of the correlations are estimated to be -2.02% and +2.85% for Ref ≤ 2300 and Ref > 2300, respectively. This research helps researchers and engineers to better understand the heat transfer mechanism of gas-liquid slug flow.