Condensate Retention Research Articles

A new analytical model of condensation outside low-finned tubes for refrigerants at low temperatures and high heat flux

In this paper, a new analytical model is developed for the condensation of refrigerants outside low-finned tubes. It is based on the flow and heat transfer characteristics at low saturation temperatures and high heat flux, such as those in the LNG intermediate fluid vaporizer (IFV). Due to the increase of viscous effect at lower saturation temperature and higher heat flux, the previous condensate retention angle models are modified by adding the viscous term. At high heat flux and condensate rate, the condensate profile at the fin root is simplified to be arc-shaped and obtained directly by force analysis. Furthermore, considering the heat transfer enhancement caused by the circumferential flow at high heat flux, the convective mechanism is included for the heat transfer through the thick liquid film between the fins. The distributions of liquid film and fin surface temperature are also predicted. The present analytical model is in good agreement with different experimental and numerical results, while most deviations are within 10% for predicting the heat transfer coefficients at high heat flux. Because of the increased flow viscosity and surface tension, the optimal fin spacing and fin height increase as the heat flux increases and the saturation temperature decreases.

Entrainment Makes Pollution More Likely to Weaken Deep Convective Updrafts Than Invigorate Them

AbstractAre the results of aerosol invigoration studies that neglect entrainment valid for diluted deep convective clouds? We address this question by applying an entraining parcel model to soundings from tropical and midlatitude convective environments, wherein pollution is assumed to increase parcel condensate retention. Invigoration of 5%–10% and <2% is possible in undiluted tropical and midlatitude parcels respectively when freezing is rapid. This occurs because the positive buoyancy contribution from freezing is larger than the negative buoyancy contribution from condensate loading, leading to positive net condensate contribution to buoyancy. However, aerosol‐induced weakening is more likely when realistic entrainment rates occur because water losses from entrainment more substantially reduce the latent heating relative to the loading contribution. This leads to larger net negative buoyancy contribution from condensates in polluted than in clean entraining parcels. Our results demonstrate that accounting for entrainment is critical in conceptual models of aerosol indirect effects in deep convection.

Durability and Degradation Mechanisms of Antifrosting Surfaces.

Rapid implementation of renewable energy technologies has exacerbated the potential for economic loss and safety concerns caused by ice and frost accretion, which occurs on the surfaces of wind turbine blades, photovoltaic panels, and residential and electric vehicle air-source heat pumps. The past decade has seen advances in surface chemistry and micro- and nanostructures that can promote passive antifrosting and enhance defrosting. However, the durability of these surfaces remains the major obstacle preventing real-life applications, with degradation mechanisms remaining poorly understood. Here, we conducted durability tests on antifrosting surfaces, including superhydrophobic, hydrophobic, superhydrophilic, and slippery liquid-infused surfaces. For superhydrophobic surfaces, we demonstrate durability with progressive degradation for up to 1000 cycles of atmospheric frosting-defrosting and month-long outdoor exposure tests. We show that progressive degradation, as reflected by increased condensate retention and reduced droplet shedding, results from molecular-level degradation of the low-surface-energy self-assembled monolayer (SAM). The degradation of the SAM leads to local high-surface-energy defects, which further deteriorate the surface by promoting accumulation of atmospheric particulate matter during cyclic condensation, frosting, and melt drying. Furthermore, cyclic frosting and defrost tests demonstrate the durability and degradation mechanisms of other surfaces to show, for example, the loss of water affinity of superhydrophilic surfaces after 22 days due to atmospheric volatile organic compound (VOC) adsorption and significant lubricant drainage for lubricant-infused surfaces after 100 cycles. Our work reveals the degradation mechanism of functional surfaces during exposure to long-term frost-defrost cycling and elucidates guidelines for the development of future surfaces for real-life antifrosting/icing applications.

Effect of condensate flow rate, surface tension, density and vapor velocity on condensate retention of wire wrapped tubes

Simulated condensation has been conducted on three wire wrapped tubes having same root diameter but different fin spacing of 1.5 mm, 2 mm, and 2.5 mm. Different fluids (ethanol, ethylene-glycol, and water) are used for condensation by providing them to the tubes through tiny holes in inter-fin spacing on the top of the surface of tubes. The major parameters are to be controlled in this research are fin spacing, vapor velocity, condensate flow rate and ratio of surface tension density of the fluid. Obtained results show that flooding angle (calculated from the top of the tube to the level where fluid fills the fin) rises by increasing fin spacing. Also, retention angles increase by reducing ratio of surface tension density of fluid. Acute flooding angles at zero air velocity and zero flow rate, elevates by increasing air velocity. However, obtuse flooding angles at static conditions drop by reducing air velocity. An interesting result is obtained regarding retention angle which remains almost even for the higher condensation flow rates until the tube gets inundated with condensation. Moreover, critical flow rates for all the tubes against using different working fluids are measured. Results obtained for static conditions have good correspondence with already available authentic data for flooding angle. Pictures showing condensate retention angles have been included in this paper.

A Multispecies Pseudoadiabat for Simulating Condensable-rich Exoplanet Atmospheres

Abstract Central stages in the evolution of rocky, potentially habitable planets may play out under atmospheric conditions with a large inventory of nondilute condensable components. Variations in condensate retention and accompanying changes in local lapse rate may substantially affect planetary climate and surface conditions, but there is currently no general theory to effectively describe such atmospheres. In this article, expanding on the work by Li et al., we generalize the single-component moist pseudoadiabat derivation in Pierrehumbert to allow for multiple condensing components of arbitrary diluteness and retained condensate fraction. The introduction of a freely tunable retained condensate fraction allows for a flexible, self-consistent treatment of atmospheres with nondilute condensable components. To test the pseudoadiabat’s capabilities for simulating a diverse range of climates, we apply the formula to planetary atmospheres with compositions, surface pressures, and temperatures representing important stages with condensable-rich atmospheres in the evolution of terrestrial planets: a magma ocean planet in a runaway greenhouse state; a post-impact, late-veneer-analog planet with a complex atmospheric composition; and an Archean Earth-like planet near the outer edge of the classical circumstellar habitable zone. We find that variations in the retention of multiple nondilute condensable species can significantly affect the lapse rate and in turn outgoing radiation and the spectral signatures of planetary atmospheres. The presented formulation allows for a more comprehensive treatment of the climate evolution of rocky exoplanets and early Earth analogs.

Evaporator Frosting in Refrigerating Appliances: Fundamentals and Applications

Modern refrigerators are equipped with fan-supplied evaporators often tailor-made to mitigate the impacts of frost accretion, not only in terms of frost blocking, which depletes the cooling capacity and therefore the refrigerator coefficient of performance (COP), but also to allow optimal defrosting, thereby avoiding the undesired consequences of condensate retention and additional thermal loads. Evaporator design for frosting conditions can be done either empirically through trial-and-error approaches or using simulation models suitable to predict the distribution of the frost mass along the finned coil. Albeit the former is mandatory for robustness verification prior to product approval, it has been advocated that the latter speeds up the design process and reduces the costs of the engineering undertaking. Therefore, this article is aimed at summarizing the required foundations for the design of efficient evaporators and defrosting systems with minimized performance impacts due to frosting. The thermodynamics, and the heat and mass transfer principles involved in the frost nucleation, growth, and densification phenomena are presented. The thermophysical properties of frost, such as density and thermal conductivity, are discussed, and their relationship with refrigeration operating conditions are established. A first-principles model is presented to predict the growth of the frost layer on the evaporator surface as a function of geometric and operating conditions. The relation between the microscopic properties of frost and their macroscopic effects on the evaporator thermo-hydraulic performance is established and confirmed with experimental evidence. Furthermore, different defrost strategies are compared, and the concept of optimal defrost is formulated. Finally, the results are used to analyze the efficiency of the defrost operation based on the net cooling capacity of the refrigeration system for different duty cycles and evaporator geometries.

A semi-empirical model for retained condensate on horizontal pin-fin tube including the effect of vapour velocity

During condensation process, the formation of condensate film is main resistance to retard heat transfer. This liquid condensate on horizontal pin-fin tube is known as condensate retention that generally blocks the lower part of tube and act as an insulation resulting in the form of resistance to heat transfer. Various, tube geometries experimentally tested with different pin-fin longitudinal and circumferential thickness and spacing, pin-fin height, internal and external tube diameters under the effect of vapour velocity are selected for model development. As it is extremely important to estimate the extent of condensate retention on such pin-fin tubes in order to make more effective horizontal pin-fin tubes in terms of heat transfer. The development of semi empirical correlations for condensate retention on pin-fin tubes as a function of vapour velocity (forced convection condensation) is proposed in this paper. Various geometric parameters and fluids are considered for model development. Accurate data are used for the model development. The proposed model which is based upon the dimensional analysis successfully predicts available data to within 5%. Relative standard deviation was about 2.44, 2.30 and 1.73 for water, ethylene glycol and refrigerant respectively. The development of such a semi empirical model is the first important step required for the development of full-scale heat transfer model of condensation heat transfer on horizontal pin-fin tubes during forced convection.

Superhydrophobic fins with inclined arrangement for enhancing energy saving of air-cooled wet heat exchangers

The energy consumption of the air-cooled heat exchangers such as evaporators operating under wet conditions is much higher owing to the condensate retention and bridging. The retained condensates and condensate bridging could narrow down the free airflow passage in the fin side and can adversely increase the airside pressure drop, which raises the fan power consumption. Effective condensate drainage can minimize the fan power consumption in such thermal management systems. Accordingly, this work proposes a superhydrophobic heat exchanger with an inclined fin arrangement that can effectively remove condensates and minimize the airside pressure drop. In this work, the departure droplet diameter of the untreated and superhydrophobic surfaces is predicted using the force balance analysis. A rationally based correlation is proposed to describe the condensate shedding ability of the different fin surfaces through dimensionless analysis. It is found that the departure droplet diameter of the superhydrophobic surfaces is almost 90% smaller than that of the untreated surfaces. The superhydrophobic fins offered remarkable condensate shedding characteristics. Consequently, the superhydrophobic heat exchangers with inclined fins provided a pressure drop reduction of up to 70%. The effect of inclination angle and the superhydrophobic coating on the heat transfer rate is negligible.

AN OVERVIEW OF RECENT PROGRESS IN CONDENSATION HEAT TRANSFER ENHANCEMENT ACROSS HORIZONTAL TUBES AND THE TUBE BUNDLE

The present paper presents a review of condensation heat transfer across smooth and enhanced horizontal surfaces due to its significance in refrigeration, air conditioning and heat pump applications. The emphasizes is on the recent understanding of experimental as well as the semi-empirical correlations to investigate the heat transfer phenomena during condensation associated with enhanced geometries. An effort has been made to submit free-convection condensation effects outside of single tubes and the tube bundle with the influence of tube geometries, condensate retention and gravity on film condensation; however, comparison of forced convection is also presented. Alternative of conventional refrigerants in condensation process by low-global warming potential (GWP) refrigerants is addressed as well due to increase in atmospheric burden affected by hydro-fluoro-carbons (HFCs). Although many researchers have reviewed the condensation impact across enhanced surfaces, a few of them revised its behavior across pin-fin tubes. The effects of geometry, surface wettability, and operating conditions on the location, amount and form of condensate film are discussed. Various theoretical models prediction with the new experimental data across pin-fin tubes is also revealed. This review is distributed into two main sections: the first section focuses on condensation across enhanced tubes, sub dividing the study into integral-fin and pin-fin tubes based on theoretical and experimental investigations. It covers the geometrical effects concerning three dimensional (3D) surfaces, fin density, fin spacing and fin thickness. The later part of the paper concentrates on condensation behavior across the tube bundle incorporating the effects of fin density and refrigerant mixtures highlighting both theoretical and experimental knowledge. Recent research shows an agreement between theoretical and experimental models in the defined area; though, a considerable amount of work on semi-empirical correlation formulation is visible in the literature. The strength of this paper is the latest findings on condensation against different geometrical parameters of extended surfaces specifically across pin- fin tubes and the tube bundle. Finally, theoretical enhancement factors along with many heat transfer correlations are presented and recommendations are suggested for the future work.

Energy-saving of air-cooling heat exchangers operating under wet conditions with the help of superhydrophobic coating

The condensate retention and bridging on the airside of the heat exchanger, such as the evaporator of the heat pump and air-conditioning system, can adversely increase the pressure drop penalty and energy consumption of the heat transfer systems. The objective of this study is to minimize the airside pressure drop of the rectangular plain heat exchangers using superhydrophobic coating which promotes continuous condensate shedding through coalescence induced droplet jumping. The experiments are carried out for different inlet air temperatures (23 °C and 27 °C), relative humidities (50%, 70%, and 90%) and the fin base temperature is fixed to be 7 °C. While the frontal air velocity is varied from 0.5 to 2.5 m/s, and the fin spacing ranges from 1 mm to 4 mm. The results showed that the heat transfer rate between untreated and superhydrophobic heat exchanger is almost similar; whereas a 30–55% increase in heat transfer is observed when inlet air temperature increased from 23 °C to 27 °C and an increase of 20–50% and 60–100% in heat transfer is noticed when relative humidity increased from 50% to 70% and 90%, respectively. Due to the effective condensate removal and the early arrival of steady state, the airside pressure drop for the superhydrophobic heat exchanger is almost two times lower than that of the untreated one. The reduction in airside pressure drop led to appreciable energy saving of the heat transfer system, and it is found that 30–60% saving can be achieved especially at higher relative humidities (70% or 90%) and frontal air velocities (more than 1 m/s).

Natural fracture, cleat, and strong adsorption impact on low oil and condensate retention in the Carboniferous shales and coals of the western Black Sea Basin of Turkey

Total organic carbon (TOC) values of the Carboniferous shales and coals of the western Black Sea Basin of Turkey range from 0.72 to 71.52 wt. %, with an average of 32.3 wt. %, and generation potential chance from 0.33 to 184.64, with an average of 82.47 mg HC/g rock. Hydrogen index (HI) values of the shales and coals range from 24 to 384 mg HC/g TOC. The HI versus pyrolysis temperature at the maximum rate of kerogen conversion plot indicates that the organic matter is type II–III. The calculated vitrinite reflectance equivalent values of the shales and coals range from 0.63% to 1.32%. Thus, the shales and coals of the Carboniferous formations are represented by immature, effective oil and condensate generation windows. The shales and coals of the Alacaagzi Formation contain high quartz and lower clay. Oil saturation index (OSI) values of the shales and coals have been calculated as being 0.7 and 12 mg HC/g TOC, indicating possible lack of producible oil and condensate. The OSI values are lower than those of other coal-bearing and marine shales of the world. First, strong adsorption capacity may be a cause of the lower oil and condensate retention. Second, faults, natural fractures, and cleats related fluid flows may be important factors in these lower OSI ratios. The extensional, collisional, and inverse tectonic stages and diagenetic processes of coalification formed multiple interconnected faults, natural opening-mode fractures, and cleats in the shales and coals. Thus, 15 coalbed methane exploration wells failed to produce any economical coalbed methane.

Investigation on dynamic behaviour of condensation heat transfer in indirective evaporative cooler

Indirect evaporative cooling is a rapidly developing air-handling technology and has great application potentials for energy recovery in hot and humid regions. The condensation in dry channels of an indirect evaporative cooler (IEC) occurs when the dew point temperature of outdoor air is high. However, the dynamic heat transfer performance of an IEC during the process of condensation evolution was rarely discussed. This paper aims to experimentally investigate the dynamic behaviour of primary air condensation and its effects on the convective and total heat transfer rate of an IEC. A transparent cover plate is placed outside an aluminium heat exchanger plate to visualize the evolution process of droplets retained on the surface. The droplets' falling frequency was recorded and the accumulated condensate mass was correlated based on an analytical method taking into account the contact angle and droplet volume. Results showed that the dynamic dehumidification performance can pose great influences on the convective heat transfer in IEC. The gradually diminished dropwise regions and increase of filmwise regions deteriorate the wet-bulb effectiveness of IEC by 14.8%. The convective heat flux keeps decreasing with the accumulation of condensate retention until a dynamic equilibrium is achieved between the retained and falling droplets.

Condensation heat transfer characteristics of moist air outside a three-dimensional finned tube

The condensation heat transfer of moist air is a common phenomenon in industry processes, and improving the efficiency of condensation heat transfer is a common focus of research. Many studies have shown that extending the surface of the heat exchanger can effectively enhance the condensation heat transfer efficiency. Therefore, this study focused on a three-dimensional (3-D) finned tube heat exchange element with an extra-large extended surface, and experiments were conducted to study the condensation heat transfer characteristics of moist air outside the 3-D finned tube. The effects of different steam mole fractions, moist air velocities, cooling water inlet temperatures, and moist air temperatures on the condensation heat transfer characteristics of the moist air outside the 3-D finned tube were studied under atmospheric pressure. A smooth tube was also tested under the same conditions for comparison. The experimental results showed that the 3-D finned tube can achieve a higher heat transfer coefficient compared with the smooth tube under all tested conditions. Moreover, for both the 3-D finned tube and the smooth tube, the heat transfer coefficient increased with an increase in the steam mole fraction and moist air velocity, and decreased with an increase of moist air temperature or cooling water inlet temperature. Furthermore, in a single-phase convective heat transfer case, the 3-D finned tube could achieve 3.1 times the heat transfer coefficient of the smooth tube. In a moist air condensation heat transfer case, the 3-D finned tube could achieve 1.7 times the heat transfer coefficient of the smooth tube when the steam mole fraction was 0.05. Although the 3-D finned tube had a more serious condensate retention phenomenon compared with that of the smooth tube, the 3-D fins could still increase the heat transfer area and effectively break the flowing boundary layer outside the tube wall. In addition, the 3-D finned tube had a higher heat transfer coefficient compared with the smooth tube.

Effect of fin pitch on the filmwise condensation of steam on three-dimensional conical pin fin arrays: A comparative study

An experimental investigation on the use of three-dimensional conical pin fins to enhance filmwise condensation of steam on vertical plates was carried out. Nine surfaces with conical pin fin arrays were fabricated by Selective Laser Melting and tested in a condensation chamber. The conical pin fin arrays have the same fin base diameter but are of different fin heights and fin pitches. The effects of fin pitch on the condensation heat transfer performance of the conical pin fin arrays were examined. A detailed comparative study was also carried out to evaluate the thermal performances of the conical, sinusoidal and cylindrical pin fin arrays fabricated by Selective Laser Melting. Based on our investigation, it was determined that the condensation heat flux and heat transfer coefficient of the conical pin fin specimens increase as the fin pitch increases from 1.25 mm to 1.67 mm. However, with a further increase in the fin pitch from 1.67 mm to 2.50 mm, reductions in the heat flux and heat transfer coefficient were recorded. The highest thermal enhancement factor of 2.46 was achieved with the conical pin fin specimen of 1.28 mm fin height and 1.67 mm fin pitch. Visualization studies of the static condensate retention height show that the change in fin pitch has more significant effect on the condensation retention height as compared to the change in fin height. A fin analysis was performed to determine the average heat transfer coefficients of the conical pin fins. In addition, a thermal enhancement-to-area enhancement ratio was also proposed to evaluate the condensation performances of conical pin fin arrays. Our results show that significantly higher average heat transfer coefficients and thermal enhancement-to-area enhancement ratios were obtained by the conical pin fin surfaces as compared to the sinusoidal and cylindrical pin fins. Due to the significant surface tension effect and reduced condensate flooding, the conical pin fin structure is shown to be the best geometry for enhancing natural convection condensation heat transfer as compared to the sinusoidal and cylindrical pin fins.

Experimental investigation of condensate retention on horizontal pin fin tube with varying pin angle

This paper presents the effect of pin fin rotational angle on the condensate retention as function of vapour velocity (0–20 m/s) on four different pin fin tubes, by systematically changing the pin fin angle from 0° – 45° with horizontal axis. While other parameters of pin fin tubes like tooth height, tooth thickness, longitudinal spacing inner and outer diameter remain constant for all 4 tubes tested. Three fluids (2-propanol, distilled water and ethylene glycol) with varying surface tension to density ratio are tested. Experimentation is conducted in a vertical wind tunnel by downward supply of air (to simulate vapour) with velocity from 0 - 20 m/s. By accurate small holes on upper side of the tube a constant flow of condensate was assured on a tube to be tested. At almost all vapour velocities; it is observed that retention angle increases with increase in pin fin angle for all fluids tested. As the vapour velocity increased from 0 to 20 m/s, it is observed that the retention angle for tube A1 increased for all test fluids, whereas with increasing velocity, a decrease in retention angle is observed for tubes A2, A3 and A4 for all fluids tested.

Condensate retention of water-ethanol mixture on horizontal enhanced condensing tubes

Condensate retention has been found an important parameter for heat transfer on horizontal enhanced condensing tubes. In this research, five pin-fin (varying in circumferential pin spacing) and three integral-fin horizontal tubes are investigated for condensate retention angle (which is measured from the top of tooth to the fully flooded flank) using water-ethanol mixture. An attempt was made to find the optimum concentration of ethanol in water for maximum retention angle. Concentration of ethanol was varied in between 0.5% to 1.5% by weight. Data revealed the importance of integral-fin tube over pin-fin tube as significant increase in retention angle was observed for integral-fin tube ((having same longitudinal spacing, tooth thickness, tooth height, inner and outer diameter) while retention angle for pin-fin tubes remain unchanged. Optimum ethanol concentration was observed to be 0.75%.

Condensate retention as a function of condensate flow rate on horizontal enhanced pin-fin tubes

The extent of condensate flooding as a function of condensate flow rate is measured on six horizontal pin-fin tubes (varying in circumferential pin-spacing) via simulated experimentation. Surface tension to density ratio is tested using three fluids namely water, ethylene glycol and R-141b. Results show that flooding was strongly effected by changing the condensate flow rate. An increase in flow rate caused a marginal decrease in flooding angle (an angle extracted from top of the test tube to the fully flooded flank). Similarly, circumferential pin-spacing also effected the retention angle and the effect goes on increasing by decreasing the surface tension to density ratio.

Filmwise condensation of steam on sinusoidal pin fin arrays: Effects of fin height and fin pitch

An experimental investigation on the use of sinusoidal pin fins to enhance filmwise condensation of steam on vertical plates was carried out. Nine surfaces with pin fin arrays were fabricated by Selective Laser Melting (SLM) and tested in a condensation chamber. The pin fin arrays have the same fin base diameter (db) but are of different fin heights (l) and fin pitches (p). At the same fin pitch (p = 1.25 mm and 1.67 mm), the heat flux (q″) and condensation heat transfer coefficient (h) increase as l increases from 1.25 mm to 1.66 mm. However, with further increment in l from 1.66 mm to 2.49 mm, reductions in q″ and h were observed. At the same fin heights of l = 1.25 mm and 1.66 mm, an increase in p from 1.25 mm to 1.67 mm has negligible effects on q″ and h. However, with further increment in p from 1.67 mm to 2.50 mm, significant reductions in q″ and h were observed. Visualization studies of the static condensate retention height (Have) show that two distinct flooding regions can be identified for sinusoidal pin fin surfaces. The static condensate retention height of both regions decreases with increasing p but remains unchanged with varying l. A fin analysis was performed to determine the average heat transfer coefficients (ht) which considers the total heat transfer areas (At) of the enhanced surfaces. Our results show that the highest thermal enhancement factor (η) of 1.86 is achieved with Specimens S4 and S5 whereas Specimens S3 has the highest average heat transfer coefficient (ht). In comparison with cylindrical pin fin surfaces, the sinusoidal pin fin surfaces show better heat transfer performances at the same p/l ratio.

Condensation heat transfer in horizontal three dimensional two-layer two-side enhanced tubes

Condensation heat transfer characteristics of near-azeotropic refrigerant R410A inside the horizontal copper and stainless steel EHT series tubes were measured. All three dimensional two-layer two-side enhanced tubes have deep-textured surface structures composed of petal-shaped background patterns and dimpled protrusions or boat-shaped cavities. Tests were conducted at an average saturation temperature of 45 °C; over a mass flux range of 100–450 kg/(m2·s); with an inlet quality of 0.8 and outlet quality of 0.2. Condensation heat transfer coefficient of the copper 1EHT1 tube is about 39–47% higher than that of a stainless steel one, showing a beneficial effect of high thermal conductivity material. Effects of saturation temperature and tube diameter on the copper 1EHT tubes were also discussed. Compared with a smooth tube, the heat transfer enhancement ratio of these stainless steel EHT tubes is up to 1.19. As expected, the 1EHT1 tube exhibits the highest condensation heat transfer coefficient due to its larger dimpled protrusions. In addition, the heat transfer performance of 1EHT2 and 3EHT tubes are similar. An explanation could be the condensate retention in boat-shaped cavities on the bottom of the 3EHT tube.

Filmwise condensation of steam on vertical plates with novel pin fin arrays produced by selective laser melting

An experimental investigation of the use of pin fin arrays to enhance filmwise condensation of steam on vertical plates was carried out. New fin geometries of cylindrical, conical and sinusoidal profiles were produced and investigated in a condensation chamber. The effects of fin geometry and fin height were systematically examined and a comparison of the heat transfer performances of the pin fin structures and equivalent longitudinal fins was made. Visualization studies were carried to determine the condensate retention heights of the various fin structures and to elucidate the possible mechanisms affecting the condensation heat transfer coefficient. Our results show that the pin fin structures exhibit higher heat transfer performances as compared to the equivalent longitudinal fins of the same fin base diameter/width, pitch and height even though the longitudinal fins have larger heat transfer area as compared to the pin fins. The conical fin geometry of Specimen C1 was shown to promote condensate drainage away from the specimen surface, which reduced the condensate retention height and enhanced the heat transfer. In addition, the three-dimensional geometry of the conical fin also resulted in additional variation of curvature that reduces the film thickness near the fin tip and promotes heat transfer. On the other hand, the sinusoidal fin geometry of Specimen S1 promoted the draining of the condensate film from the fin tip to the fin base which significantly improved heat transfer near the fin tip. In comparison with the plain surface, enhancement factors (η) of 2.04 and 1.80 were achieved with Specimens C1 and S1, respectively.