Condenser Tubes Research Articles

Comparison of theoretical methods for describing the heat transfer in vertical tube condensers under conditions corresponding to the condensation of flue gas from a biomass boiler

Abstract A theoretical and experimental study was conducted on water vapor condensation in a vertical tube condenser under conditions corresponding to the condensation of flue gas from biomass boiler where flue gas is considered as a mixture of water vapor and a high content of noncondensable gas (NCG). Four fundamental theoretical methods were identified to determine the heat transfer coefficient and condenser heat output - Empirical correlations, Heat and mass transfer analogy, Diffusion layer theory, Boundary layer theory. These methods were compared with respect to usability in the design of flue gas condensers in energy systems and experimentally verified. Experiments were carried out in a 1.5 m long vertical double-pipe condenser with a condensing gas flowing downward in an inner tube with a diameter of 25 mm. The mass concentration of NCG in a mixture with water vapor ranged from 11 to 86 vol.% and the inlet Reynolds number of the condensing gas ranged from 1936 to 14408, which corresponds with the conditions of condensing flue gas from biomass boilers. The boundary layer theory is very complex and impractical for the calculation of heat exchangers. Empirical correlations have a wide dispersion of the result, because they take into account only the basic parameters of the process. However, Heat and mass transfer analogy and Diffusion layer theory seem to be the most suitable for flue gas condensers since they capture the physical essence of the phenomena.

Analyzing the Influence of Welding Process Selection on Residual Stresses in Tube-to-Tubesheet Welded Joints

Tube-to-tubesheet joints are used in the fabrication of shell and tube type heat exchangers, steam generators, boilers, condensers, and end shields of pressure tube type nuclear reactors like CANDU (Canada Deuterium Uranium) and PHWR (Pressurized Heavy Water Reactor). The weld joints connecting the tubes to the tubesheets are of prime importance as they have a direct impact on equipment safety. In the fabrication of these critical class-1 nuclear components, full penetration weld joints are used. Typically, these full penetration weld joints are created through multi-pass Tungsten Inert Gas (TIG) welding. However, more recent techniques, such as single-pass Electron Beam Welding (EBW) and Laser Beam Welding (LBW), have also been employed for this purpose. The fabrication time of these pieces of equipment containing full penetration weld joints can be drastically reduced if single-pass welding techniques are used compared to multi-pass welding techniques. However, the residual stresses developed in these joints due to the localized heat input and the substantial constraints of the tubesheet are unknown. Different welding processes, such as TIG welding, EBW, or LBW, can lead to varying levels of residual stresses in these joints, subsequently impacting their longevity. Weld residual stress plays a significant role in the initiation of failure modes of these tube-to-tubesheet welded joints, such as stress corrosion cracking, fatigue, and corrosion fatigue.This paper analyzes the residual stresses developed at the tube-to-tubesheet interface resulting from different welding techniques, such as multi-pass TIG welding and single-pass EBW/LBW. A comprehensive three-dimensional coupled thermo-mechanical finite element analysis is employed for this purpose. The findings reveal a significant difference, with single-pass EBW exhibiting up to 32% lower residual stresses compared to multi-pass TIG welding. Additionally, the Heat Affected Zone (HAZ) in EBW is approximately 50% smaller than in TIG welding, and the equivalent distortion in EBW is reduced by 90% compared to multi-pass TIG welding. In summary, this investigation concludes that single-pass EBW offers distinct advantages for tube-to-tubesheet weld joints, including reduced residual stresses, a smaller HAZ, and lower distortions.

Material and Parametric Design Optimization of Improved Heat Transfer Rate of AC Condenser

Air conditioner system is made up of a condenser that removes unwanted heat in an enclosure through the refrigerant and transfers the heat outside. Improving the heat transfer of air conditioning condenser is still a difficult task because of the broader set of materials and various parametric designs involved. Due to this high cost, the experimental set-up cost cannot be modified, instead, simulation analysis was introduced in the optimization process in order to achieve a near-optimal solution. The aim of this research is to improve the heat transfer rate for air conditioning condenser by material and parametric design optimization. The system was designed based on one basic parameter optimization: varying the condenser tube diameter. This variable was changed in order to improve the heat transfer of the condenser. Simulations using Computational Fluid Dynamic (CFD) analysis and thermal analysis were carried out to have a better understanding and distinct visualization of the fluid flow and materials used, and to compare the results. The materials that were used for CFD analysis are R32 and R290, and for thermal analysis are copper (C12200) and aluminum. The analysis was done using Analysis System (ANSYS) software. Different parameters were calculated from the results that were obtained and graphs were plotted between various parameters such as heat flux, static pressure, velocity, mass flow rate and total heat transfer. From the CFD analysis, the result shows that R32 has more static pressure, velocity, mass flow rate and total heat transfer than R290 at a condenser tube diameter of 7mm. In thermal analysis, the heat flux is more for copper (C12200) material at a condenser tube diameter of 7mm than aluminum.

Variation on hydraulic diameter for the different PETG condenser tube thickness

Variation on hydraulic diameter for the different PETG condenser tube thickness

Prediction of Heat Transfer during Condensation of Ammonia Inside Tubes and Annuli

Ammonia has been used as a refrigerant since the beginning of the refrigeration industry and it continues to be an important industrial refrigerant. However, there is no well-verified method for predicting heat transfer during condensation in tubes and annuli. Available information is often contradictory, especially about the effect of oil. In this paper, available test data and predictive methods are reviewed. Reliable test data are identified and compared to well-known general correlations. The effect of oil on heat transfer is investigated. The results of this research are presented, and recommendations are made for design calculations.

Performance Evaluation of a Condenser at a Combined Cycle Power Plant Using the LMTD Method

This study evaluates the performance of the condenser at the Cilegon Combined Cycle Power Plant (CCPP) using the Logarithmic Mean Temperature Difference (LMTD) method to measure the heat transfer rate. Routine maintenance carried out on the condenser in the form of cleaning the condenser water box and condenser tube from garbage and crust on the condenser tube wall. Currently, condenser maintenance follows a routine schedule that is tied to steam turbine maintenance, without taking actual condenser performance into account. This can lead to inefficiencies and unnecessary downtime. The goal of this research is to assess the heat transfer rate of the condenser before and after maintenance to judge its effectiveness. Data on temperature changes were gathered in June 2023, before maintenance, and again in July 2023, after an overhaul. The analysis shows that the heat transfer rate increased from 51,362,294.48 kcal/h to 127,246,219.7 kcal/h, while the LMTD value rose from 0.76°C to 1.86°C. Based on these results, the study suggests a new approach to maintenance that focuses on performance. Specifically, maintenance should be done when the heat transfer rate drops below 110,000,000 kcal/h. This approach will help ensure the condenser works at its best, improve the plant's overall efficiency, and prevent the need for unnecessary maintenance. By aligning maintenance with performance data, the plant can boost output while lowering costs and downtime.

Heat transfer characteristics of vertical condensers under unsteady boundary conditions: Dynamic modeling, experiment validation, and parametric analysis

A dynamic model has been developed to predict the coupled heat transfer characteristics of vertical condensers under varying boundary conditions. The model predictions closely matched the experimental data, with normalized mean bias error and root mean square error metrics below 3%. It was observed that variations in the inlet temperature of the secondary-side coolant did not immediately affect the outlet coolant temperature, exhibiting a noticeable lag phase before gradually adjusting to new conditions. Even after the inlet coolant stabilized, the outlet coolant temperature continued to rise until reaching a steady state after a defined period. The dynamic changes in the condensate film thickness and local heat flux density were categorized into three stages: lag, transitional, and steady. These stages showed differing response and transition times across various locations of the condenser. The bottom of the condenser pipeline demonstrated the shortest response time for condensate film thickness variation but the longest transition time. Additionally, the study investigated the influence of geometric parameters on the dynamic response characteristics of condensers. It was found that longer condenser tubes, lower wall thermal diffusivity, and thicker condensing walls resulted in extended transition times for condensate mass flow at the condenser bottom.

Exergetic analysis of a domestic refrigerator with an innovative mini-channel flat tube condenser

Exergetic analysis of a domestic refrigerator with an innovative mini-channel flat tube condenser

Influence of surface structure and tube material on the condensation heat transfer coefficient of n-butane on horizontal single tubes and in tube bundles

The present study examines the condensation heat transfer coefficient αcond of n-butane on the outside of different horizontal tubes and in corresponding tube bundles. Experiments were conducted with a smooth tube, finned tubes with various fin densities, fin heights and tube materials, and a high-performance condensation tube (HPT) at vapor temperatures of (40 and 78) °C and varying heat flux densities q̇. The influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at q̇ of (20 and 60) kW·m−2. Differences between the experimental results from this work and previous ones for propane on the same condensation tubes could be explained with the help of the thermophysical properties and, thus, the retention angle of the condensate in the channels between the fins and the condensate layer thickness. For single copper tubes, αcond increased with increasing fin densities from (19 to 48) fins per inch and was between 9 and 17 times larger than for the smooth tube. This enhancement factor even reached a value of about 24 for the HPT. These increases can be attributed in part to the increased surface area, but the strongest effect appears to be related to surface tension-driven drainage of the condensate. In addition to the experimental investigations, αcond of the finned condensation tubes was predicted using an analytical model for the condensation heat transfer on finned tubes. Here, excellent agreement with an average deviation from the experimental results of 6.6 % could be found. Studies of the inundation effect have shown that the expected decrease in αcond due to the additional condensate impinging on the tubes inside bundles and increasing the film thickness often holds, but is partially counteracted by other effects and depends on the tube geometry.

Investigation of the Leak Failure of a Stainless Steel Condenser Tube Stimulated by Microbiological-Influenced Corrosion

Investigation of the Leak Failure of a Stainless Steel Condenser Tube Stimulated by Microbiological-Influenced Corrosion

Mathematical modelling of pumpkin seed drying in a rotary thermosyphon dryer

ABSTRACT Pumpkin seeds swagger a wealthy vitamin and mineral composition. They contain vitamins (A, B, C, K, D, E), minerals (calcium, selenium, zinc, magnesium, copper, potassium, press, manganese and phosphorus), a few amino acids such as glutamic, linolenic and arginine, and greasy plant acids. The Peclet number includes the peripheral rotation speed of the RTS condenser tube. In our case, the Peclet number reflects how the heat transfer to the grain layer due to convection, when the RTS capacitor rotates, relates to the heat transfer due to the thermal conductivity of the grain layer. Thus, in the first drying period, the determining factors for mass transfer will be the conditions at the phase boundary – the mode of air movement outside the grain, the area of the grain, the surface temperature of the RTS condenser. In total, pumpkin seeds contain 12 essential and eight nonessential amino acids.

Modeling and experimental study of air-cooled finned-tube condenser using coupled distribution parameter method and air-side temperature distribution

The air-cooled finned tube condenser (ACFTC) plays a crucial role in refrigeration systems, profoundly influencing overall operational efficiency. Its intricate structure, connectivity, and phase change characteristics pose challenges for numerical simulation modeling. While traditional distribution parameter methods effectively capture flow and heat transfer within tube mediums, they overlook ACFTC’s air-side temperature distribution, resulting in discrepancies between simulated and experimental outcomes. This study enhances existing distribution parameter models by incorporating ACFTC’s air-side temperature distribution characteristics, yielding an improved predictive model for transient operational behavior of both Z-shaped and U-shaped configurations. Dynamic experiments and model analyses were performed on the Z-shaped configuration using a cold storage experimental setup. Results demonstrate the improved model’s accurate prediction of tubing medium outlet temperature and pressure, with maximum deviations of approximately 3 °C and 0.01 MPa, respectively. Notably, the improved model exhibits around a 30 % enhancement in predictive accuracy compared to the existing models for both Z-shaped and U-shaped ACFTCs.

Evaluation of dropwise condensation from a vertical condenser tube impregnated with semisolid lubricant

AbstractThe quest for augmenting dropwise condensation heat transfer performance has been the driving force behind the exploration of innovative techniques and approaches to fulfill the desired objective. Mostly, earlier research on dropwise condensation was devoted to study condensation from horizontal tubes and plates but, rarely, addressed dropwise condensation from vertical tubes. An interesting topic of current research in dropwise condensation is to explore the application of Slippery Liquid Infused Porous Surfaces (SLIPSs) to improve the condensation performance. The aforesaid facts are the motivation behind the topics of interest in the present study. In this study, we explore the applicability of semisolid lubricant‐impregnated porous surfaces in enhancing dropwise condensation performance of a vertical condenser tube. The experiments conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in saturated steam environment showed significant improvement in condensation heat transfer coefficient of a vertical condenser tube impregnated with semisolid lubricants when compared to bare vertical condenser tube. The highest enhancement is found to be 280% at a subcooling of 40°C. Furthermore, these surfaces proficiently sustain dropwise condensation over a period of 72 hours without compromising heat transfer performance. The devised fabrication method is simpler, more cost‐effective, and less time‐consuming than earlier techniques used for creating SLIPSs. Additionally, an approach based on numerical optimization by a stochastic global optimization technique, namely, Genetic Algorithm, is proposed to retrieve the coefficients and the exponent in the mathematical expression of overall resistance, that is being used to compute the tube‐side dropwise convection heat transfer coefficient.

Modified Evaporation Model for ATHLET System Code in a Passive Containment Cooling System for Nuclear Safety

The presented work deals with the improvement of the evaporation model of the ATHLET (Analysis of Thermal and Hydraulics of Leaks and Transients) system code to be applied to a passive containment cooling system of a nuclear power plant. For the model validation, INTRAVIT (Investigation of Passive Heat Transfer in a Variably Inclined Tube) test facility setup at the University of Luxembourg was used. The first part of the paper presents a review of the existing literature on evaporation models that revealed that those models significantly simplify the physical processes that occur. Next, a modified evaporation model is proposed that offers a realistic description of various evaporation processes and the start of bubble formation using a nucleation model, and a surface density calculation model is introduced that is necessary for evaporation simulation. The final part of this work explored five different system configurations to test the evaporation model: three condenser tube inclinations (5 deg, 60 deg, and 90 deg), two riser lengths (1 m and 2.5 m), and different thermal loads. They made it possible to simulate several experiments for stable and unstable natural circulation and to verify the proposed model.

EROSION OF TUBULAR HEAT EXCHANGERS

This paper presents the results of an erosion study of a tubular heat exchanger operating on a railroad sleepersaturation processing line. The object of the study is a DN 800 oil condenser cooling the creosote oil vaporsflowing through the condenser tubes, fixed in the sieve plate of the upper and lower condenser bottom.Subject to the erosion are the upper part of the tubes and the weld connecting the tubes to the upper sieveplate. This resulted in unsealing of the connection, which led to the contamination of the cooling medium.The key problem, therefore, is to protect the entire condenser bottom from erosion. Since only the centralpart of the surface of the top sieve plate was eroded, the conclusion is that the velocity of the vapor streamover the inlet to the condenser tubes in the central part and beyond is varied. This thesis was confirmed bythe correspondence of the actual eroded area with the cavitation area resulting from a simulated flow inAutodesk CFD 2019 Ultimate software after increasing the height of the upper condenser bottom, placinga stream dispersing element between the liquid vapor inlet to the condenser and the upper sieve plate, andafter applying a protective sieve plate. Flow simulation studies for each of these variants, or a combinationof them, made it possible to evaluate the tested solutions in terms of protection against erosion, includingcavitation erosion, of the upper sieve plate of the condenser.

SIMULATION ANALYSIS OF SHELL AND TUBE HEAT EXCHANGER USING DIFFERENT FLUIDS

There are many models to characterize the behavior of the heat exchangers encountered in many industries. There are several correlations available, so that the heat transferred and the thermal stresses can be evaluated. Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, and pre -heaters. They are also widely used in process applications as well as the refrigeration and air conditioning industry. The robustness and medium weighted shape of Shell and Tube heat exchangers make them well suited for high pressure operations. The present work deals with the design and analysis of water-cooled shell and tube condenser and we have shown how to done the thermal analysis by using theoretical formula, for this we have chosen an industrial problem of 8 ton capacity of counter flow shell and tube heat exchanger of water type. The condenser is designed using theoretical procedures. The condenser is modeled by using the dimensions obtained from the design procedures. Then thermal analysis is carried out in SOLIDWORK flow simulation. The results obtained through the analysis are discussed in detail and compared with analytic values. .Key Words: Heat exchanger, Perforated rings, Reynolds number, Overall heat transfer coefficient.

Sensitivity analysis of velocity field influence on condensers’ performance and parallel circuit design based on actual air velocity distribution

Currently, most integral simulations of condensers are based on the assumption of uniform intake air, which differs from real scenarios and leads to imprecise circuit designs. To obtain the actual air velocity distribution and reflect its impacts in the model, a comprehensive methodological system is established in this study. The implementation involves employing the porous media model to simulate air velocity distribution and utilizing the results as the air inlet condition of the distributed parameter model to achieve an integral simulation of condensers. The results indicate that the air velocity distribution is significantly non-uniform. The distribution of air velocity has a limited impact on the performance of single-row tube condenser, but has a significant effect on double-row tube condenser. Minimizing the discrepancy in the positioning of each sub-flow circuit and arranging tubes with large temperature differences in the high air velocity area can enhance heat transfer performance, the “z"-shaped double-tube parallel circuit designed by these theories can continue to improve the heat transfer performance by 2.8 % compared to the single-tube serial circuit with countercurrent arrangement within the accuracy limits of the simulations, and marking a 43.5 % improvement compared to the conventional zigzag-shaped single-tube serial circuit.

Growth characteristics of submicron particles by water vapor condensation in the multi-section growth tube

In order to study the growth characteristics of submicron particles by water vapor condensation in the multi-section growth tube, the three-stage heterogeneous condensation process model was used to predict the size distribution of grown droplets. And the supersaturated environment is formed by the cool saturated flow into a warm-walled growth tube. The calculated results show that with the increase of the section number of the growth tube, the more obviously enhanced growth effect is presented when the growth tube length is shorter and the particle number concentration is lower. Nevertheless, the increase of the section number has more advantages of particle enlargement when the CO2 concentration improved. Additionally, more section number of growth tube could strongly improve the particle growth on the condition of elevating the wall temperature compared with the situation of reducing the inlet temperature. Meanwhile, the final mean size of grown droplets could be enhanced by 16.03% and 3.46% with the section number from 5 increasing to 15 in the case of promoting wall temperature or declining inlet temperature by 10 K, respectively.

Experimental investigation of the oscillation threshold to limit state operation of a single branch pulsating heat pipe

The study investigates the characteristics of oscillations and associated thermo-hydrodynamic phenomena for startup, limit state, and intermediate transitional behavior of a pulsating heat pipe (PHP) with the help of its single branch. Experiments are performed on a transparent single branch PHP (SBPHP) at different orientations, evaporator and condenser section temperatures using n-pentane as the working fluid. The entire two-phase flow behavior is recorded with the help of shadowgraph based high speed imaging synchronized in real-time domain with pressure data acquisition at evaporator end. Instability threshold is determined in terms of evaporator temperature at different tube orientations and condenser temperatures. The oscillation startup mechanism along with the associated intermittency is studied in detail. The SBPHP is found to have characteristic variations in oscillation amplitude and frequency as it undergoes a gradual transition from its oscillation threshold to limit state. The mechanism by which the limit state creeps-in and intumesces further is an intrinsic function of liquid-vapor distribution in SBPHP, which in turn depends on the applied boundary conditions. The operational limit is governed by evaporator dryout exceeding permissible limits marked by the steep rise in the dry length of evaporator. As SBPHP approaches or operates at its limit state, evaporator is found to have different regimes across its length, viz., mild convective evaporation combined with subcooled nucleate boiling, saturated nucleate boiling, forced convective boiling, film breakdown and permanent dryout. The liquid film distribution, pressure fluctuations, and heat transfer components in evaporator at the limit state have also been studied.

Performance evaluation of novel plate-type condenser for an absorption/adsorption refrigeration system: Experimental and CFD study

Plate heat exchangers are widely used in many industries, such as refrigeration and air conditioning. Traditionally, the condenser in an absorption system comprises a shell and tube heat exchanger. However, we have innovatively replaced the conventional tubes with chevron plates in this system. The following variables were measured: condensation pressure (5.75–7.00 kPa), wall subcooling (0.2–1.8 °C), and channel Reynolds number (350–1400). In alignment with experimental results, the CFD simulation shows a higher condensation rate and large droplet size at the higher subcooling, and lower heat flux as the saturation pressure is decreased. Moreover, the overall heat transfer coefficient and the pressure drop of the chevron-type plate heat exchanger are increased by 1.60–5.00 times and 1.30–3.00 times, respectively, compared to the shell and tube condenser.