Condensation Region Research Articles

Analysis of noctilucent clouds’ fields according to ground-based network and airborne photography data

The article analyzes the fields of noctilucent clouds over the territory of the Russian Federation, recorded by a ground-based network of cameras using also aircraft photography, over the two nights in June 2021. It is demonstrated that aircraft photography can significantly improve the coverage of the territory of noctilucent clouds’ probable appearance. The detected noctilucent cloud fields are compared with model regions of water vapor condensation derived from satellite measurements of temperature and water vapor mixing ratio. Practical steps are proposed for the development of aircraft observations of noctilucent clouds.

Computational Evaluation of Pulsating Heat Pipe for Fluid Flow Behavior and its Thermal Performance

Computational fluid analysis of a single circuit heat pipe was undertaken to ascertain the thermal efficiency of water at various fill ratios, specifically 40%, 50%, and 60% under varying heating conditions. The analysis employed the ANSYS Fluent computational fluid dynamics software, utilizing a k-epsilon to the heat pipe as the solver. The analysis was carried out on a copper tube with an internal diameter measuring 3/16 inches. During the analysis, the thermal inflow at the adiabatic region was adjusted to zero, while the condenser region’s temperature remained constant at 25°C. Meanwhile, the heat input at the evaporator region was systematically adjusted to 105°C, 110°C, 115°C, and 120°C. Key Performance characteristics of heat pipe i.e. thermal resistance, and water volume fraction were evaluated during analysis. The temperature variations noted in both regions affirmed that the pulsating pipe’s performance was influenced by the phase transition between liquid and vapor. Furthermore, the concentration of volume within the evaporator section was monitored, confirming the presence of a dual-phase phenomenon within the heat pipe. Through the analysis, it was noted that the thermal resistance of the water is minimized at a 50% fill ratio for each level of heat input. Notably, the promising results were obtained at an input temperature of 120°C with a value of 1.025°C /W which was 7.3% and 9.8% lower than thermal resistance at 40% and 60% fill ratios, respectively. The reduced thermal resistance in this scenario is attributed to the flow dynamics within the capillary, propelled by rapid phase change mechanisms. This shows the importance of Pulsating Heat Pipes (PHPs) in thermal control, as well as the intricacies of their operating mechanisms. Experimental and theoretical investigations have investigated numerous elements influencing PHP performance, with numerical modeling providing insight into thermal resistance and water volume fraction dynamics under varying heating temperatures and fill ratios.

Multiphase Gas in Elliptical Galaxies: The Role of Type Ia Supernovae

Massive elliptical galaxies harbor large amounts of hot gas (T ≳ 106 K) in their interstellar medium (ISM) but are typically quiescent in star formation. The jets of active galactic nuclei (AGNs) and Type Ia supernovae (SNe Ia) inject energy into the ISM, which offsets its radiative losses and keeps it hot. SNe Ia deposit their energy locally within the galaxy compared to the larger few ×10 kiloparsec-scale AGN jets. In this study, we perform high-resolution (5123) hydrodynamic simulations of a local (1 kpc3) density-stratified patch of the ISM of massive galaxies. We include radiative cooling and shell-averaged volume heating, as well as randomly exploding SN Ia. We study the effect of different fractions of supernova (SN) heating (with respect to the net cooling rate), different initial ISM density/entropy (which controls the growth time t ti of the thermal instability), and different degrees of stratification (which affect the freefall time t ff). We find that SNe Ia drive predominantly compressive turbulence in the ISM with a velocity dispersion of σ v up to 40 km s−1 and logarithmic density dispersion of σ s ∼ 0.2–0.4. These fluctuations trigger multiphase condensation in regions of the ISM, where min(tti)/tff≲0.6exp(6σs) , in agreement with theoretical expectations that large density fluctuations efficiently trigger multiphase gas formation. Since the SN Ia rate is not self-adjusting, when the net cooling drops below the net heating rate, SNe Ia drive a hot wind which sweeps out most of the mass in our local model. Global simulations are required to assess the ultimate fate of this gas.

Single-Well Simulation for Horizontal Wells in Fractured Gas Condensate Reservoirs.

Fractured gas condensate reservoirs (FGCR) are a complex, special, and highly valuable type of gas reservoir, accounting for a significant proportion of gas reservoir development. In recent years, with the continuous advancement of horizontal well technology, it has become the main approach for the development of FGCR. The current model is unable to accurately represent the fluid distribution in the near-well area of horizontal wells due to the unique retrograde condensation phenomenon in GCR. Additionally, the presence of fractures complicates the solution of traditional analytical models. In response to this issue, this paper proposes a novel semianalytical model for horizontal wells in FGCR, which incorporates natural fractures, multiphase flow, and the influence of stress sensitivity on pressure response. A dual-porosity model is employed to simulate fractured reservoirs, and a four-region radial composite model is developed to characterize multiphase flow resulting from retrograde condensation in GCR. The pseudopressure transform, Pedrosa transform, Laplace transform, and Finite Cosine transform are utilized to address the nonlinear partial differential equation. A systematic verification of the semianalytical solution is confirmed through a comparison with the numerical solution from computer modeling group (CMG). We thoroughly explain the physical significance of the various features by identifying the 12 flow regimes of the typical curve. Furthermore, we offer a method for assessing the extent of retrograde condensation and the size of the retrograde condensate region based on the curve's characteristics. Finally, the pressure measurements recorded from the Bohai field are carried out to validate the accuracy of the proposed model. The results show that the predictions of the new model are in good agreement with the actual production data, demonstrating the proposed solution's applicability.

The effect of the inlet steam superheat degree on the non-equilibrium condensation in steam turbine cascade

Due to the high steam velocity and low thermal parameters at the turbine's final stage, steam generates non-equilibrium condensation and forms a large number of small droplets during the process of pressure expansion. The wet steam mixed with droplets impinges on the turbine blades, endangering turbine operation safety and reducing turbine work efficiency. This article modifies the non-equilibrium condensation control equation and embeds it into the numerical simulation software to make the numerical calculation results more accurate. By modifying the inlet steam superheat in the classical experiments, the condensation characteristics of wet steam in Moses–Stein nozzles and Dykas cascades are studied. The results show that increasing inlet superheat can effectively suppress the generation of non-equilibrium condensation and reduce outlet liquid mass fraction. The minimum supercooling temperature of non-equilibrium condensation is only related to the working fluid characteristics (the steam model used in this article is around 20 K). When the inlet superheat of the cascade is large, the rapid condensation region is mainly near the suction surface. In contrast, when the superheat is low, the rapid condensation zone is mainly near the pressure surface. The condensation location is mainly affected by the intensity of internal condensation shock waves in the cascade. Increasing inlet superheat not only increases the shock wave intensity but also decreases the shock wave angle in the passage. When the inlet temperature increases by 20 K, the heat efficiency of the cascade increases by about 1%.

Investigation of mechanical properties of graphene-CNT reinforced nickel metal matrix nanocomposite structure

Nickel is a metal widely used in many industrial applications, but despite its superior properties, it also has some shortcomings. Carbon-based structures can be important reinforcement elements in improving the properties of metals. By providing a balance between the high corrosion resistance, high electrical conductivity and good magnetic properties of the nickel material and the lightness and high strength of carbon-based structures, a material with advanced properties can be obtained. Therefore, in this study, a new Nickel-Carbon nanostructure supported by a covalently bonded graphene-carbon nanotube (CNT) skeleton structure is presented. Additionally, three material designs with different geometric dimensions (Ni-G-CNT(5,5), Ni-G-CNT(10,10) and Ni-G-CNT(15,15)) were designed to determine the mechanical properties and properties of the structures in all directions. is to investigate the underlying deformation mechanisms. According to the results, it was observed that G-CNT structures increased the tensile and compressive behavior of the Ni structure in the CNT direction. For tensile loading in the CNT direction, as the CNT diameter decreases, the elastic modulus of the hybrid structures increases, while the maximum stress values are independent of the CNT diameter. As the CNT diameter increases, the ductility of the structures increases. In terms of compressive strength, it has been observed that in the linear region, as the CNT diameter increases, the strength generally increases and in the condensation region, it exhibits better compressive strength. With this study, an anisotropic nanostructure that is lighter and can exhibit higher tensile strength compared to the Ni structure is presented.

Fluid characterization of oil and gas fields: implications for fault and top seal integrity assessment

Integrity of fault and top seal is a key factor that affects hydrocarbon fluid phase distribution in the subsurface. Mapping fluid property distribution can therefore provide important tools towards assessing seal integrity and trapping mechanisms – two of the most critical elements in petroleum systems analysis towards optimzing exploration and development strategies. This is best achieved by proper fluid characterization that integrates fluid geochemistry and pressure–volume–temperature (PVT) data to identify equilibrated and disequilibrated fluid gradients. Fields from Paleozoic and Mesozoic basins in the Arabian Peninsula at different stages of delineation, appraisal, development and management are discussed as examples to demonstrate the role of fluid characterization in aiding the evaluation of top, lateral and fault seal integrity, and in providing insights into the sealing and buffering effects of reservoir heterogeneity on trapping mechanism, fluid distribution and flow capacity. Examples discussed include (1) reservoir heterogeneity controlling fluid distribution and trapping mechanisms in two neighbouring gas fields, (2) geochemical evidence for a lateral seal separating gas condensate region from oil discovered during field development, (3) solid reservoir bitumen atop a giant gas field, (4) selective gas leakage through anhydrite seal, and (5) geochemical evidence for fault-controlled reservoir compartmentalization rather than a hydrodynamically tilted fluid contact in a field at an appraisal stage where PVT data are limited or inconclusive. Put in structural context, seal-related interpretations of the fluid data are aligned with observations from seismic and geological data on the existence of faults with favourable orientations or facies changes. Thematic collection: This article is part of the Fault and top seals 2022 collection available at: https://www.lyellcollection.org/topic/collections/fault-and-top-seals-2022

A close look at the H-C phase Diagram and Hydrocarbon Reservoir Classification and Behavior

H-C phase diagram of reservoir fluids is an important tool used in explaining reservoir fluids behavior during the life period of any reservoir. In this paper, detailed analysis of certain terms of the Pressure–Temperature Diagram (P-T diagram) are presented and discussed. Some of these terms are redefined since the already existing definitions does not fit all cases and conditions of reservoir pressure and temperature, and hence, new definitions are given to such terms so as to make them fit all possible conditions that might exist in the reservoir. Special attention was given to explain and analyze the phase behavior inside the phase envelope (two phase region) of the P-T diagram. Among such terms for example, new definitions and analysis are given to the quality lines to give them much more interest and importance in the P-T diagram as they should be given than just representing the percentages of both liquid and gas phases. The new given definition will open new interpretations and add more interesting and valuable importance to the quality lines. Another new definition is given herein to the Cricondenbar Pressure to make it fit all possible conditions on the P-T diagram since the existing definition does not fit all pressure and temperature conditions. This paper also include some explanations regarding the retrograde gas condensation process and region on the P-T diagram. Finally, the herein mentioned factors and definitions will add more important and wider interpretations and applications for the P-T Diagram for a better understanding of H-C reservoirs. Such interpretations might be applied, also to the fluid flow control inside the reservoir and in the choosing of the best EOR method to apply whenever and wherever it is necessary.

Understanding the effect of the condensation temperature on solar-driven reverse distillation for enhanced water production

Reverse distillation driven by solar energy decouples light-incoming and evaporation–condensation regions that are integrated together in conventional solar distillation, thereby providing diverse choices in materials and structures for enhancing vapor condensation. However, detailed experiments and discussion are scarce in exploring how condensation temperature influences the solar-to-water energy conversion efficiency in the reverse-distillation process and may thus constrict the further understanding and application in water production processes. A common impression is that a low temperature is good for vapor condensation and performance improvement but that may not be the case. An interesting conclusion from both experimental and theoretical exploration in this research is that the efficiency of the reverse-distillation device first increases and then decreases with the condensation temperature, indicating an optimal condensation temperature for obtaining the best water production performance. In indoor experiments with one-sun illumination, the reverse-distillation device with natural air cooling shows a distillate yield of 1.04 kg⋅m−2⋅h−1 and a solar-to-water energy conversion efficiency of 68.8 %, which is 9.4 % and 6.3 % more than that of a device with enhanced cooling by water flow and inhibited cooling by thermal insulation, respectively. In the outdoor experiments, the increase in efficiency using natural air cooling is 4.9 % and 7.1 % compared with the enhanced and inhibited cooling measures, respectively. The conclusion is further explained from the perspective of heat-and-mass transfer, which may provide meaningful guidance for designing a high-efficiency reverse-distillation system. In future water production, cooling measures should be cautiously considered according to the device structure and the actual working conditions to achieve better performance.

Determination of optimum parameters using different nano fluids in heat pipe heat exchangers with response surface method

In this study, optimum parameters affecting the thermal efficiency of heat pipes were determined experimentally with response surface method using different types of nanofluids in heat exchangers. Experimental design was carried out at three levels for four parameters affecting thermal efficiency. Experiments were made for Al2O3, TiO2 and SiO2 at 0.2-0.4-0.6% concentrations. Nanofluid suspensions were formed using isopropyl alcohol as the base fluid. The inlet temperatures in the evaporator region were determined as 30-60-90 °C, and the Reynolds numbers in the condenser region were determined as 7200, 14400 and 21600. The thermal efficiencies of the heat pipes were calculated as a result of the experiments carried out in accordance with the experimental design created with the response surface method. The accuracy of the model was tested with analysis of variance (ANOVA) and optimum parameters were obtained as nanoparticle SiO2, concentration 0.32%, evaporator inlet temperature 90 °C and Reynolds number 21600 in the condenser.

Design of a sheathed water condensation particle counter with variable saturation ratio

We consider a particle condensation device where a cold aerosol enters at one open end of a tube. The wall of the tube is porous beyond a certain section. A stream of cold air is injected radially and symmetrically through an initial focusing region of the porous wall, and a stream of warm humid air with a saturation ratio S is injected in a condensation region further downstream. The configuration offers several advantages over existing water condensation particle counters (WCPCs). First, S may be varied by mixing a dry gas stream with a humid stream prior to their passage through the porous tube wall. Second, radial entry of the humidified flow accelerates the penetration of the vapor into the core of the tube, such that the maximal saturation ratio is reached within axial distances comparable with the tube radius. Third, the aerosol is partially confined within the tube core by the radially entering dry and humid gases. The particles then sample the relatively uniform saturation field near the tube axis, resulting in sharp responses of the activation probability versus particle diameter. Calculations with various combinations of axial and radial Reynolds numbers are carried out in search of conditions resulting in the smallest possible variation of the maximal supersaturation reached along the various flow streamlines.

Study on characterization and distribution of four regions of tight sandstone condensate gas reservoirs in the depletion development process

The traditional three-region theory cannot explain why some condensate gas reservoirs have high production in field depletion development even if the formation pressure is below the dew point. To solve this problem, the re-designed depletion development experiments are conducted under various pressure drop velocities conditions. Besides, a new quantitive method of the pressure range of different regions is established. The results show that there is a fog-state region in the porous medium, which is in the adjacent area below the dew point, and the production of the fog-state region is as high as the pure gas region. Compared with the fog-state region, the instantaneous gas and condensate production in the movable gas and immovable condensate (MIMC) region decreased by 23% and 93.8% in this work, respectively. The depressurizing velocity has a great impact on the fog-state region range, the positive coupling effect caused by a suitable depressurizing velocity can enlarge the fog-state region and compress the MIMC region, but the inertia effect caused by over-high depressurizing velocity will generate plenty of condensate bridges and reduce the recovery of gas condensate reservoirs. To our knowledge, the existence and quantitive pressure range of the fog-state region of the gas condensate reservoir in the porous medium is experimentally determined for the first time, which improves the traditional three-zone theory of the gas condensate and gives important support to reservoir-scale field application.

An experimental study of steam turbulent jet condensation & upward propagation of thermal plume into sub-cooled water pool

Supersonic steam’s axial injection into water in a cylindrical vessel (1 m high and 24 cm in diameter) was achieved through a nozzle of 6 mm diameter, located at the center of the vessel. Optical examinations were determined through a steam jet to find out condensation rate, which was allied with the steam mass flux (295–672 kg/m2/s) while leaving the nozzle’s exit. The Reynolds number (i.e., 41,000–73,610) has been estimated based on most swollen section of the steam’s jet. Further beyond the condensation zone, the steam, that has been condensed, progresses into a condensed steam plume, which is surrounded by the sub-cooled water. Particle Image Velocimetry (PIV) has been applied to focus region through the mid axis of the heated water plume along a vertical plane of 100 mm × 100 mm cross sections till 400 mm from the nozzle. Central upward averaged velocity profile of the condensed water thermal plume has been evaluated at 295 and 672 kg/m2s, both have hinted the exponential decrease of mean axial velocity when the plume travels vertically upward. The radial velocity distribution of the mean axial velocity across the radial dispersal of the jet, has been obtained as self-preservable and the mean axial velocity attained the Gaussian profile by incorporating appropriate grading of axial distance and mean velocity. Other significant aspect of the current work is to apply the buoyant scaling evolved from the single-phase non-condensing upward thermal plumes to the condensed upward plume through the relations of volume flow, momentum and buoyant being computed from the steam jet operating conditions. The source values of physical dimensionless parameters such as Reynolds number (Reo), Plume Richardson number (Ripo), entrainment coefficient (αo), buoyant vertical scale (Bo) have been evaluated. Based on the radial spread of the velocity profiles along the vertical distance from the condensation region, the dynamics of the thermal and the jet propagation has been highlighted through the evaluation of the dimensionless buoyant parameters along the downstream of the plume. The present experimental measurements obtained for condensed single-phase plume are compared with the experimental results of the non-condensed single-phase thermal plume to signify the vitality of the dimensionless parameters derived from non-condensed plumes.

Adiabatic wall temperature in the supersonic flow of moist air with spontaneous condensation

The expansion of moist air in supersonic nozzles is accompanied by spontaneous condensation of water vapor due to a sharp decrease in flow temperature and pressure. However, in the near-wall boundary layer due to the viscous dissipation, moist air temperature decreases slightly in comparison with initial one. This leads to the fact that the vapor remains overheated in the near-wall region and condensation does not spread to its entire depth. Droplets formed in the core flow as a result of condensation can penetrate into the near-wall region due to turbulent diffusion and evaporate due to higher temperature in the near-wall region. This process causes cooling of the near-wall gas layers and, consequently, a decrease in the adiabatic wall temperature. A decrease in the adiabatic wall temperature relative to the stagnation temperature leads to a decrease in aerodynamic heating and, consequently, in the heat flux from the gas to the body. In this paper, measurements of the adiabatic temperature of the supersonic nozzle wall for moist air flow with condensation are presented. Temperature measurements were made using an infrared thermal imager. Initial moisture content varied in the range of 1.5–20.2 g/(kg. dry air) and initial relative humidity in the range 20–90%. It is shown that in the region behind the zone of spontaneous condensation (“condensation shock”), adiabatic wall temperature depends on the initial moisture content and can be either greater or less than the value of a single-phase (dry air) flow with identical initial flow parameters. Estimates of the flow parameters behind the condensation region are obtained using one-dimensional diabatic flow equations and experimental static pressure distributions along the nozzle length. The correlation between the initial moisture content, the average droplet size and the temperature recovery factor is shown.

Cooling of power electronic devices using rectangular flat heat pipes with externally and internally cooled condenser regions

In traditional heat pipes employing external cooling, the internal flow pattern undergoes a transition to annular flow. In this stage, vapor moves through the central region of the heat pipe, while a liquid film develops on the inner wall surface. This liquid film acts as a thermal barrier, impeding the condensation of vapor within the vapor core area, which reduces the coolant's ability to condense vapor effectively. To address this issue, a rectangular flat heat pipe with an internal condenser (RFHP-IC) has been designed and tested for heat loads up to 360 W with different fill ratios. The RFHP-IC incorporates a tube-in-tube structure within the condenser section of the heat pipe, facilitating the condensation of the working fluid while maintaining a compact form factor. Results indicate that employing an internal condenser reduces thermal resistance and evaporator wall temperature by 67.5% and 20.1% respectively when compared to an external condenser. Furthermore, the RFHP-IC allows vapor to make direct contact with the cold surface of the internal condenser, increasing the condensation rate by 8.5% in comparison to an external condenser under the same heat load. The findings of this study can improve the performance, capacity, and reliability of RFHPs, making them more suitable and efficient solutions for thermal management applications.

Hartree–Fock with Nambu spinors, and d-wave condensation in the 2D Hubbard model

The usual Hartree–Fock approximation to the Hubbard model is based on eigenstates of the electron number operator. But this formulation is not unique. A different (and inequivalent) version, formulated in terms of Nambu two-component spinors, is based on eigenstates of the difference between the numbers of spin up and spin down electrons, with electron density dependent on parameters U,t,t′ and chemical potential μ. The advantage of this formulation is that electron pairing condensates can be directly computed. We show that in the ground states away from half-filling, obtained in this “Nambu” Hartree–Fock approximation, a discrete rotation symmetry is spontaneously broken, and the condensates exhibit the expected d-wave form in momentum space. We also show that the Mott insulator electron configuration is obtained in this formulation at large U/t and half-filling, and roughly locate the boundary, in the hole doping−U/t plane, between a region of local antiferromagnetism and stripe/domain formation, and the region of d-wave condensation.

Preparation of high purity magnesium by vacuum gasification-directional condensation technology

As the lightest structural metallic material, magnesium (Mg) is expected to be widely used in many fields to instead of steel and aluminum. However, there are still too many kinds of impurities in Mg ingot which will be transformed to Mg products and damage their performance obviously. In this paper, by analyzing of the source and existence form of the impurities in Mg ingot and calculating the optimal removal temperature, the volatilization and condensation, migration and enrichment processes of different elements in purification process were clarified. Based on the theoretical research, a vacuum gasification-directional condensation technology and a vacuum tubular furnace were proposed, which can remove most impurities in Mg ingot. The key impurities (such as Fe, Co, Ni, Cu) and difficult to remove impurities (such as K, Na, Zn) are all removed effectively, high purity Mg more than 99.999% can be collect in the high temperature condensation region.

A Facile Ultrapure Water Production Method for Electrolysis via Multilayered Photovoltaic/Membrane Distillation

Ultrapure water production is vital for sustainable green hydrogen production by electrolysis. The current industrial process to generate ultrapure water involves energy-intensive processes, such as reverse osmosis. This study demonstrates a facile method to produce ultrapure water from simulated seawater using a low capital cost and low-energy-consuming membrane distillation (MD) approach that is driven by the waste heat from photovoltaic (PV) panels. To optimize the PV-MD operation, modeling efforts to design a multilayered MD system were carried out. The results were used to guide the construction of several prototype devices using different materials. The best performing PV-MD device, containing evaporation and condensation regions made from steel sheets and polytetrafluoroethylene (PTFE) membranes, can produce high-purity water with conductivity less than 40 mS and flux higher than 100 g/m2 h, which is suitable for typical electrolyzer use.

Performance evaluation of a solar desalination-hot water system using heat pipe vacuum tube parabolic trough solar collector – An experimental study with Taguchi analysis

The utilization of renewable energy to generate hot water and distilled water can considerably reduce pollution. This study looked at a hybrid system that used a parabolic-trough heat pipe solar collector to generate hot water while also providing drinking water. The system is constructed in two stages, the first producing distilled water and the second producing hot water. A concave mirror increases the temperature of a vacuum tube heat pipe's evaporator area and the condenser of the heat pipe, which is directly connected to the desalination system's saltwater tank. To improve the amount of drinking water generated and to transfer thermal energy to the hot water generation system, a condenser region at the top of the saltwater tank, as well as multiple heat pipes, were employed. The effect of the water flow rate (200, 300, 400 and 500 ml/min), number of heat pipes (0, 1, 2 and 4), and the filling porous medium (0, 0.3, 0.6 and 0.9 m) of the vacuum tube on the system performance were evaluated. In addition, Taguchi-Based design of experiments was used to determine the effect of independent input parameters on the energy and efficiency of the system. The results showed that the effects of water flow rate, porous medium length, and number of heat pipes on the energy efficiency were approximately 50.89%, 26.53%, and 20.6%, respectively. Furthermore, the cost of distilled water and the cost of hot water were approximately 0.0380 $/L and 1.01 $/m3, respectively. Additionally, the highest daily productivity of the system (4940 ml/day) was obtained with a water flow rate of 200 ml/min, a length of porous media of 0.6 m, and four heat pipes. The CO2 emission reduction based on the environmental and enviroexergoeconomic parameters of the proposed systems ware improved by 37.5% and 268.4%, respectively, resulting in returns of approximately $358.1 and $260.5, respectively.

Experimental investigation of heat transfer limitations in concentric annular sodium heat pipes and thermosyphon

This paper presents experimental investigations on the heat transfer performance of concentric annular heat pipe (CAHP) and thermosyphon (CATP) using sodium as a working fluid for microreactor applications. CAHP characterized by wicks on the inner and outer walls offers the potential to enhance capillary force and enable more compact microreactor designs. The research aims to understand the implications of structural differences between CAHP, CATP and conventional heat pipe (CHP) and identify favorable conditions for their use in microreactors. The thermal behavior and heat transfer limits of CAHP and CATP were examined under various boundary conditions. The experimental results revealed that CAHP exhibited capillary limits approximately 71.2% higher than cylindrical heat pipes under horizontal conditions. However, the Chi model used for predicting capillary limits showed a difference about 19.7% in horizontal operation and exceeded 44.6% in vertical operation, highlighting the need for considering the effect of non-uniform capillary forces in CAHP. The presence of additional inner wick in CAHP provided large evaporation areas, which facilitated rapid vapor generation and enabled the development of a continuum flow faster than in CHP, by approximately 70 °C. However, in vertical operation, CATP necessitates higher heat fluxes and exhibits notable temperature disparities between the evaporator and condenser regions compared to CAHP. This difference can be explained depend on the vapor generation mechanisms: heat pipes utilize additional wick area to facilitate evaporation, while thermosyphon depend on boiling that the advantages related to the annular flow path in CATP are not clear. Furthermore, the presence of an adiabatic section yields contrasting effects: while it promotes the formation of larger menisci in heat pipes, its presence is unfavorable in thermosyphons as it can elevate boiling temperatures that delayed operations. The findings underscore the advantages of CAHP over CHP, particularly in microreactor applications, provide insights into design optimizations for compact microreactors, and showed gaps in operating prediction models and experimental results.