Condensation Heat Transfer Characteristics Research Articles

Numerical investigation on flow condensation in zigzag channel of printed circuit heat exchanger

The printed circuit heat exchanger (PCHE) has a great potential for the application in various compact energy systems. However, the there is no existing heat transfer and pressure drop correlations on condensation in PCHE zigzag semicircular channel. In this study, the flow and heat transfer characteristics of condensation in the PCHE zigzag semicircular channel were analyzed numerically. The flow patterns of annular flow, annular wavy flow and plug flow were observed in the channel, and the flow pattern transition line correlations were developed. As the mass flux increases, the transition vapor quality from annular flow to intermittent flow decreases gradually. Both the condensation pressure drop and the heat transfer coefficient reach their peaks as the vapor quality is around 0.78, and the pressure drop decreases with the increase of saturation temperature. The heat transfer coefficient decreases as the saturation temperature increases when the vapor quality is less than 0.6, while it increases slightly as the saturation temperature increases when the vapor quality is greater than 0.6. New correlations for condensation pressure drop and heat transfer in PCHE zigzag semicircular channel are developed. The average errors of the developed condensation pressure drop and heat transfer correlations are 11.0 % and 7.9 %, respectively.

Research on the R513A condensation heat transfer characteristics in horizontal microfin tubes

R513A has been proposed as alternative to R134a due to its lower GWP. So, it is necessary to investigate the condensation heat transfer characteristics and pressure drop of R513A in the horizontal tubes. The 12.70-mm-OD and 9.52-mm-OD tubes were selected for condensation tests. It was found that the R134a condensation heat transfer coefficient in the 12.70-mm-OD microfin tube was similar to the R513A condensation heat transfer coefficient, and the deviation was about −3% ∼ +9%; R513A yielded 4.44% ∼ 16.01% lower pressure drop than R134a. The R513A heat transfer coefficient of the microfin tube was about 1.42–1.74 times of that of the smooth tube, and the pressure drop was 39.11% ∼ 76.63% than that in the smooth tube. Additionally, the condensation heat transfer coefficient and pressure drop of the 9.52-mm-OD test tube were 23.88% ∼ 41.62% and 40.79% ∼ 71.86% higher than those of the 12.70-mm-OD tube, respectively. The micro-fin structure inside the microfin tube resulted in efficient heat transfer, but also increased the fluid flow power consumption. Moreover, as the tube diameter decreased, the effects of sheer stress and surface tension increased. Furthermore, experimental data were also compared with previous correlations proposed for microfin tubes. More experiments are still required to develop more applicable theoretical correlations in future.

Experimental research on condensation flow and heat transfer characteristics of immiscible binary mixed vapors on different wettability wall surfaces

In the process of biomass gasification syngas waste heat recovery, water and organic compounds in the syngas will condense at the same time, resulting in immiscible condensates adhering to the wall, which can reduce the heat exchanger heat transfer efficiency and working life. Changing the wettability of the wall surface can affect the condensate flow state on the wall surface, thus affecting the condensation heat transfer performance. Water and organic cyclohexane were used as immiscible working fluids in this paper, the condensation flow and heat transfer characteristics of the mixed vapors on hydrophilic, super-hydrophilic, and super-hydrophobic wall surfaces were experimentally investigated. The results showed that cyclohexane in immiscible condensates existed as a liquid film on hydrophilic, super-hydrophilic, and super-hydrophobic wall surfaces, while the water existed in droplets on the hydrophilic and super-hydrophobic wall surfaces, and there were two forms of channels and droplets on the super-hydrophilic wall surface. The condensation heat transfer coefficient on the super-hydrophobic wall surface was higher than that on the hydrophilic wall surface and the super-hydrophilic wall surface, with a maximum of 34% higher than hydrophilic and 45% higher than super-hydrophilic, which was related to the smaller droplet departure diameter on the super-hydrophobic surface. In addition, the super-hydrophilic wall surface had better heat transfer performance than the hydrophilic wall surface only when the immiscible condensate was a "film-channel" flow pattern. The results can provide guidance for enhancing the condensation heat transfer of the water and organic compounds binary mixed vapors.

Numerical study of condensation heat transfer characteristics of R134a/R290 and R134a/R1270 refrigerant blends as alternatives to replace R404A

R404A needs to be replaced due to its higher GWP in the context of green development. In this study, M1 (R134a/R290, 55/45) and M2 (R134a/R1270, 43/57) were proposed to replace R404A refrigerant. The thermodynamic properties were compared. The heat transfer and pressure drop characteristics of condensation for R404A, M1 and M2 inside horizontal microtube (D = 1 mm) at saturation temperature of 40℃ were investigated numerically. The results showed that the COP of M1 and M2 were higher than that of R404A, while the GWP of M1 and M2 is 81.83 % and 85.79 % lower than that of R404A, respectively. The heat transfer coefficients and pressure gradients increase with increasing mass flux and vapor quality, the heat transfer coefficient of M1 and M2 were on 50 ∼ 55 % and 78 ∼ 80 % higher than that of R404A. However, the pressure gradients of M1 and M2 were on 95 ∼ 110 % and 105 ∼ 115 % larger than that of R404A. The liquid film thicknesses of M1 and M2 were smaller than that of R404A. M1 and M2 could be used as low GWP alternatives to R404A with regard to thermodynamic performance and heat transfer properties. The results of the study have important guiding value for the replacement of R404A.

Flow condensation heat transfer correlation development of R32-oil mixture inside a micro-fin tube

The air-conditioners employ R32 as refrigerant because it has low GWP. The heat transfer performance of R32 in the heat exchangers would be influenced by the lubricating oil cycled with R32. In order to obtain the quantitative effect of oil on the flow condensation heat transfer characteristics, flow condensation heat transfer correlation of R32-oil mixture is needed. In this study, an experimental rig for testing the flow condensation heat transfer coefficients of R32-oil mixture is established. The test conditions covering the actual working conditions of air-conditioners are designed, including the condensation temperature ranging from 40 to 50 °C, mass flux ranging from 100 to 400 kg m − 2 s − 1, vapor quality ranging from 0.1 to 0.9 and oil concentration ranging from 0 % to 5 %. The results show that the flow condensation heat transfer coefficients decrease with the increasing of oil concentration because of the high viscosity of the oil. A new condensation heat transfer correlation is developed based on the enhanced structure of the micro-fin tube and physical properties of the working fluid, and it agrees with 82 % of the experimental results within a deviation of ± 20 %.

Two-phase flow condensation heat transfer characteristics of R-134a inside three-dimensional cylindrical micropillar enhanced tube

This paper presents an experimental investigation for evaluation of heat transfer coefficient, frictional pressure drops and flow regimes with their transitions during the condensation of R-134a inside a smooth, two microfins (MF1 and MF2) and a newly developed micropillar (MP) tubes. The experiments are carried out for a range of mass flux at an average saturation temperature of 35°C. Micropillar tube has produced the maximum heat transfer coefficient, while the microfin (MF1) tube resulted the highest frictional pressure gradient compared to other tubes. The experimental observations of microfin and micropillar tubes are plotted on the mass flux versus vapor quality flow map and Taitel and Duckler flow map to discuss the transitions within different flow patterns achieved. Visual inspection of the flow regimes with varying mass flux and vapor quality showed stratified-wavy, intermittent, and annular flow regimes. The occurrence of annular flow is found to be more in MF1 and MP tube. A performance evaluation factor (PEF) is defined to evaluate the thermal-hydraulic performance of the tubes. Using the same, it has been observed that the newly developed MP tube has a PEF value greater than unity which suggest augmentation of heat transfer coefficient at the expense of lesser pressure drop penalty.

Numerical evaluations on enhanced steam–air condensation outside S-type tubes under natural convection conditions

Steam-air condensation is extensively utilized in various industrial fields. In pursuit of better efficiency in applications, this study promoted a novel structure of heat transfer enhancing tube named S-type tube. It combines the superior heat transfer performance of short tubes and inclined tubes, demonstrating a high potential for enhanced condensate heat transfer. To evaluate the heat transfer property and obtain the optimized S-type tube structure, three-dimensional CFD methods were used, coupled with the liquid film model in STAR-CCM + software. The effcts of wall sub-cooling, pressure, air mass fraction and downward forced velocity, bend radius, horizontal section length on the steam–air condensation heat transfer characteristics outside S-type tubes were investigated. It was identified that S-type tubes can enhance the steam–air condensation heat transfer capability, and the enhanced heat transfer ability increases with the increase of pressure and the decrease of air mass fraction, and remains basically unchanged with changes in sub-cooling. The condensation heat transfer coefficients outside S-type tubes are 0.9 ∼ 1.71 times that of vertical tube range 0.2 MPa to 0.8 MPa. The main mechanisms affecting the condensation heat transfer are summarized: the scouring effect between tube segments to enhance heat transfer and the air layer pileup effect to inhibit heat transfer. The heat transfer enhancement capacity for the S-type tube is determined by the relative magnitude between the scouring effect and the pileup effect. Both effects increase as bend radius decreases; therefore, selecting an appropriate bend radius is crucial.

Experimental study and general correlation for condensation heat transfer coefficient inside microfin tubes

This study investigated the condensation heat transfer characteristics of the pure refrigerants R1234yf and R32 in a microfin tube with a small diameter of 3.5 mm outside diameter and 3.18 mm inner mean diameter. Experiments were carried out at mass velocities between 50 and 200 kg m-2 s-1, saturation temperatures of 20 and 30 °C, and vapor quality between 0 and 1. The effects of vapor quality, mass velocity, saturation temperature, and refrigerant properties on condensation heat transfer characteristics were investigated. A new correlation is also developed to predict condensation heat transfer coefficients that can be applied to horizontal microfin tubes with inner diameters between 2.5 and 8.9 mm. The new correlation is validated with the database containing 1240 experimental data points from 10 independent research groups. The comparison results show that the three existing correlations overestimate the heat transfer coefficient data with mean deviation greater than 30.0 %. Meanwhile, the new correlation predicted the present experimental data and other researchers' data with mean deviation of 19.8 %.

Experimental Study on Condensation Heat Transfer Performance of Hydrophilic/Hydrophobic Microstructured

In order to study the condensation and heat transfer characteristics of similar microstructure surfaces, two similar microstructure surfaces, cylindrical and circular, were fabricated by femtosecond laser technology on a 0.5 mm silicon wafer. The cylindrical surface is superhydrophobic when the contact angle is more than 150°, and the circular surface is hydrophilic when the contact angle is less than 90°. The difference in condensation heat transfer characteristics between superhydrophobic and hydrophilic microstructures was analyzed, and a visual condensation experimental platform was built. Experimental research showed that: At the same flow rate, the heat transfer coefficient of the superhydrophobic surface and the hydrophilic surface decreases significantly with the increase of the surface subcooling degree, but the heat transfer coefficient of the cylindrical surface is still much larger than that of the circular surface. In addition, the heat transfer performance of the hydrophobic microstructure surface is better than that of the hydrophilic surface at medium and high-speed cooling water flow rates. Although the surface microstructures are similar in shape, the heat transfer performance of cylindrical microstructures is much better than that of circular microstructures under the same conditions, and the heat flux of cylindrical microstructures is 2.2 times that of circular microstructures.

Analysis of influence of inlet vapor quality on heat transfer and flow pattern in mini-channels during flow condensation process

Micro/mini-channel heat sinks are extensively utilized in heat dissipation systems that involve high heat flux components. These heat sinks are preferred due to their compact size and excellent heat transfer efficiency. The selection of a refrigerant condensation system for the heat dissipation system under vapor conditions is crucial. In order to investigate the heat transfer characteristics of flow condensation in a mini-channel, a visual experiment system was used with a hydraulic diameter of 2 mm and a volume flowrate of 30 mL/min, 60 mL/min, 90 mL/min, 120 mL/min respectively. The study focused on the effect of inlet vapor quality on the flow pattern and heat transfer characteristics of flow condensation in the mini-channel. The results indicate that the flow pattern in flow condensation process can be classified into annular flow, transition flow, slug flow and bubble flow in sequence along the flow direction. As the inlet vapor quality (xin) increases, the dominance of annular flow gradually increases, making it difficult to capture the bubble flow with high volume flowrate and high inlet vapor quality. This phenomenon is observed under experimental conditions when: 1) xin is equal to or greater than 0.75 at a volume flowrate of 60 mL/min, 2) xin is equal to or greater than 0.55 at a volume flowrate of 90 mL/min, and 3) xin is equal to or greater than 0.25 at a volume flowrate of 120 mL/min. The increase in inlet vapor quality is beneficial to the improvement of condensation heat transfer coefficient. In this experiment, it was observed that the local heat transfer coefficient was decreased by up to 83.7 % when comparing the lowest vapor quality to the highest at the same volume flowrate, emphasizing the significance of inlet vapor quality in the flow condensation during the heat transfer process.

The Effect of Heat Exchanger Tube Structure on the Condensation Heat Transfer of R1234ze(E)/R152a Inside Smooth Tubes

Abstract In this paper, the flow condensation heat transfer characteristics of the environmentally friendly nearly-azeotropic refrigerant R1234ze(E)/R152a (mass ratio of 40:60) in smooth tubes with varying structures were numerically investigated. Under the operating conditions of mass flux of 400 kg/m2/s, heat flux of 12 kW/m2, and saturation temperature of 308.15 K, this study investigated the influence of circular tube inner diameter, elliptical tube aspect ratio, and installation orientation on condensation heat transfer, while the influence on pressure drop has not been taken into account in the present study. The results indicate that the condensation heat transfer coefficient in the tube increases as the inner diameter of the circular tube decreases. The condensation heat transfer coefficient increases by 1.086 times when the circular tube inner diameter is reduced from 10.7 mm to 5 mm. Under identical operating conditions, the condensation heat transfer coefficient of the mixed refrigerant in elliptical tubes increases with an increase in the aspect ratio. The average condensation heat transfer coefficient increases by 18.21% as the aspect ratio of the elliptical tube increases from 1 to 2. Compared to a vertical elliptical tube, a horizontal elliptical tube is more favorable for condensation heat transfer within the tube.

Experimental study on heat transfer characteristics of the phase change chambers for heat flux enhancement

One promising way to increase the output power and the thermoelectric conversion efficiency of an automotive exhaust thermoelectric generator (TEG) is to add a phase change chamber between the exhaust channel and the thermoelectric (TE) modules with the chamber surface contacting with the exhaust channel where boiling occurs being larger than that with the module surfaces where the condensation occurs. The power is increased because a phase change chamber significantly increases the heat flux through the modules; thus, increasing the temperature difference between the module hot and cold sides. Although there is a significant body of literature on phase change chambers, most prior research has focused on chambers with larger condensation areas than boiling areas since they act as heat spreaders, while little is on chambers with condensation areas smaller than boiling areas for heat flux enhancement. These chambers have great potential to improve TEG power generation by enhancing the heat flux, therefore, more studies are needed to understand the chamber heat transfer characteristics. This research experimentally investigated the heat transfer characteristics of three chambers with condensation to boiling area ratios of 1/5, 2/5, and 3/5 for boiling heat fluxes from 4.50 to 22.70 kW/m2 and deionized water filling ratios from 33 to 50%. The results show that the boiling heat transfer coefficient increases with increasing heat flux or decreasing area ratio and is weakly influenced by the filling ratio. The condensation heat transfer characteristics depend on the distribution of droplets which is strongly affected by both the heat flux and the area ratio. The influence of the filling ratio on the condensation heat transfer coefficient increases with increasing area ratio. The thermal resistance of the chamber decreases with increasing heat flux and the lowest thermal resistance is obtained at 1/5 area ratio at lower heat fluxes and at 2/5 or 3/5 area ratio at higher heat fluxes.

The Condensation Characteristics of Propane in Binary and Ternary Mixtures on a Vertical Plate

Natural gas is one of the most common forms of energy in our daily life, and it is composed of multicomponent hydrocarbon gas mixtures (mainly of methane, ethane and propane). It is of great significant to reveal the condensation mechanism of multicomponent mixtures for the development and utilization of natural gas. A numerical model was adopted to analyze the heat and mass transfer characteristics of propane condensation in binary and ternary gas mixtures on a vertical cold plate. Multicomponent diffusion equations and the volume of fluid method (VOF) are used to describe the in-phase and inter-phase transportation. The conditions of different wall sub-cooled temperatures (temperature difference between the wall and saturated gas mixture) and the inlet molar fraction of methane/ethane are discussed. The numerical results show that ethane gas is more likely to accumulate near the wall compared with the lighter methane gas. The thermal resistance in the gas boundary layer is one hundred times higher than that of the liquid film, revealing the importance of diffusion resistance. The heat transfer coefficients increased about 11% (at ΔT = 10 K) and 7% (at ΔT = 40 K), as the molar fraction of ethane increased from 0 to 40%. Meanwhile, the condensation heat transfer coefficient decreased by 53~56% as the wall sub-cooled temperature increased from 10 K to 40 K.

Condensation heat transfer characteristics and generalized correlations of R404A, R448A, and R454C in a plate heat exchanger

Although numerous studies have been carried out on alternatives to R134a and R410A to cope with regulations, the heat transfer characteristics of refrigerants with a low-global warming potential to replace R404A in a plate heat exchanger (PHE) have not yet been intensively investigated. Generally, R448A has been considered as a short-term alternative to R404A, while R454C has been nominated as a long-term alternative to R404A. In this study, the thermal and hydrodynamic characteristics of R404A, R448A, and R454C in a PHE during condensation are experimentally investigated at vapor qualities (x) of 0.2–0.8, mass fluxes (G) of 15–35 kg m−2 s−1, heat fluxes (q”) of 3–7 kW m−2, and saturation temperatures (Tsat) of 20–27 °C. The results of the analysis show that the condensation heat transfer coefficient (HTC) and frictional pressure drop (FPD) are predominantly affected by the x and G, while the q” barely affects the FPD. The average condensation HTC and FPD of R448A and R454C exceed those of R404A by 17.25–20.57% and 9.6–10.72%, respectively. Additionally, new generalized correlations of the condensation Nusselt number and frictional pressure drop for R404A, R448A, and R454C in a PHE are developed with mean relative deviations of −1.905% and 1.01%, respectively.

Numerical investigation of the gravity effect on two-phase flow and heat transfer of neon condensation inside horizontal tubes

The condensation flow and heat transfer characteristics of cryogenic neon inside horizontal tubes with diameters of 1 mm and 2 mm were numerically investigated. The mass flux ranged from 20 to 187 kg/(m2·s) for gravity levels includes zero gravity, Lunar gravity, Martian gravity, and Earth gravity. The effects of gravity on the condensation flow pattern, local condensate film distribution, and local and global heat transfer were analyzed in detail. The gravity effect on the condensation heat transfer showed three states, including enhancement, deterioration and gravity-independence, which were mainly determined by the mass flux and vapor quality. Under normal gravity, the condensation heat transfer coefficients increased with increasing mass flux and decreasing tube diameter. Under low mass flux, the cryogenic neon underwent enhanced condensation heat transfer under zero gravity and reduced gravity in the high vapor quality region but deteriorated condensation heat transfer in the low vapor quality region. By increasing the mass flux, the gravity effect was effectively suppressed, which resulted in gravity-independent behavior of condensation heat transfer in the high vapor quality region. The gravity effect significantly affected the liquid film distribution in the condensation process, with a more uniform distribution of the liquid film appearing along the circumferential direction as the gravity level decreased. However, due to the low surface tension of the deep cryogenic fluid, the condensation interface was more prone to flow instability under reduced gravity levels.

Direct contact condensation heat transfer characteristics of vapor with noncondensable gases in horizontal tubes

Direct contact heat transfer characteristics of vapor condensation with noncondensable gases in horizontal tubes are studied in this paper. A three-dimensional computational model is proposed and effects of cross-flow and droplet particles interactions are investigated. During the vapor condensation process, the convective heat transfer is attenuated due to the presence of noncondensable gases and the condensation rate is significantly reduced by 34% in the horizontal tubes due to gravity effects. A pair of counter-rotating vortex pair (CVP) is formed as influenced by adding droplet particles. Because of the centrifugal effect of vortical pair, the droplet particles are not uniformly distributed. This is not beneficial to the heat and mass transfer phenomenon. The cross-flow turbulence intensity is increased by 41.6%, as confirmed between the coherent structure in the main flow region and the CVP structure. The coherent structure can transfer energy between the CVP structure and the mainstream region, and suppress the droplet particle diffusion. In addition, the operating pressure up to 3 MPa is found to enhance the heat transfer performance. The optimal flow ratio is 1 to 8. The work provides new insights into the direct contact flow and heat transfer characteristics of vapor with noncondensable gases.

Experimental study of steam condensation heat transfer characteristics in a horizontal tube under rolling motion

As an efficient heat transfer method, in-tube condensation heat transfer is widely used in various fields, including passive residual heat removal systems (PRHRS) of floating power plants under ocean conditions. The experimental investigation aimed to study the condensation heat transfer characteristics of steam in a 25 mm inner diameter horizontal tube with a heat transfer length of 1050 mm under rolling motion. The study used a mass flux of 30 kg/(m2·s) and investigated average vapor qualities, rolling amplitude, and rolling period ranging from 0.32 to 0.79, 0 °–20°, and 10 s–20 s, respectively. The experimental results show that the condensation flow patterns under rolling conditions are more complex than those under non-rolling motion due to the influence of the rolling period and rolling amplitude. The instantaneous heat transfer coefficient (IHTC) changes periodically due to the rolling motion and has the same change period. The pulsation amplitude of the IHTC increases with increasing rolling amplitude but weakens as the vapor quality increases. The effect of the rolling period on the IHTC is much less than that of the rolling amplitude. At low vapor quality, the time-averaged heat transfer coefficient (THTC) under the rolling motion condition increases with the rolling amplitude and period, and the maximum enhancement of THTC is 44%. As the vapor quality increases, the THTC under rolling conditions is the same as that under non-rolling conditions. These findings provide important insights into the condensation heat transfer characteristics of vapor in a horizontal tube under rolling motion, which can help improve the design and operation of in-tube condensation heat transfer systems in various fields.

Numerical study on the interfacial heat and mass transfer characteristics of bubble direct contact condensation with the effect of non-condensable gas

Bubble condensation is one of the fundamental issues in the direct contact condensation, which is also affected significantly by the existence of non-condensable gas. In this study, a further investigation is carried out on air-steam bubble condensation with the Proportion Integration Differentiation (PID) control model which adjusts the mass transfer coefficient of Lee model in each time step by comparing the parameters obtained in the simulation with the ones calculated based on the empirical correlations originated from the experiments. Furthermore, species transport equations are employed to obtain the local mass fractions of steam and air. The proposed simulation schema is verified by the existing experimental data.Results show that the air-steam bubble condensation can be divided into initial and stable stages. The mass transfer coefficient used in Lee model can be regarded as linear growth over time at each stage, but with different slopes. The non-condensable gas can weaken the heat and mass transfer of condensation, but stabilize the bubble deformation. The present study also reveals the influences of subcooling and initial bubble diameter on the air-steam bubble condensation, which is expected to be instructive for better understanding the effect of non-condensable gas on the interfacial characteristics of bubble condensation in subcooled water.

A Modified Correlative Model for Condensation Heat Transfer in Horizontal Enhanced Tubes with R32 and R410A Refrigerants

An experimental study was performed that compared tube side condensation heat transfer characteristics of enhanced tubes (hydrophobic surface tubes (HYD), herringbone micro fin tube (HB), and a composite hydrophobic/herringbone (micro fin) tube (HYD/HB)) to the performance of a smooth tube (ST). The condensation heat transfer coefficient (HTC) was calculated from data that were recorded for smooth and enhanced tubes that had an outer diameter (OD) of 12.7 mm. Data were collected (as a function of mass flow rate) using a couple of refrigerants (R410A and R32), for saturated temperatures of 35 °C and 45 °C, with vapor qualities that ranged from 0.8 to 0.2. Several previously reported smooth tube HTC models were used to calculate values that could be compared to experimentally obtained HTC values. The correlation model that demonstrated the best accuracy (for the conditions considered) was then modified for use with the enhanced tubes from this study. Results from the modified correlation show differences with experimental values that ranged from −10% to +17%; the new modified correlation demonstrates high prediction accuracy. An accurate correlation allows the evaluation of enhanced heat transfer tubes for use in high-efficiency heat exchanger systems. The development of this new model is significant in the study of enhanced heat transfer.

Condensation heat transfer and pressure drop characteristics inside smooth and enhanced tubes with R410A and R32

An experimental investigation was performed to evaluate the condensation heat transfer characteristics for R32 and R410A inside four horizontal round tubes with 12.7 mm outer diameter. The saturation temperatures were 35 °C and 45 °C, the vapor qualities ranged from 0.2 to 0.8, and the mass flux ranged from 50 kg m−2 s−1 to 200 kg m−2 s−1. Different inside surface structures of the four tubes were smooth (ST), hydrophobic (HYD), herringbone (HB) and hydrophobic/herringbone (HYD/HB), respectively. Effects of mass flux, vapor quality, refrigerant and saturation temperature on condensation heat transfer in different tubes were discussed with the aid of flow pattern visualizations. Experimental results show that the heat transfer coefficient of R32 was higher than that of R410A due to different physical properties of the refrigerant. HB tube had the highest heat transfer coefficient at low vapor quality and HYD tube was the best at high vapor quality. The performance enhancement factors (PEF) of HB tube and HYD tube were better, ranging from 1.07 to 1.4 and from 1.02 to 1.31, respectively. However, as the composite of HB and HYD, the HYD/HB tube had the lowest overall performance, with the PEF ranged from 0.94 to 1.12. Additionally, the specific sensitivity factor (SSF) was used to evaluate the influence of various parameters on heat transfer and pressure drop.