Condensation Heat Research Articles

Effect of non-condensable gas on the direct-contact condensation heat transfer of vapor in a convergent tube

The direct-contact condensation heat transfer of vapor in the presence of non-condensable gas (NCG) on the falling water column in a convergent tube was simulated with a two-phase boundary layer approach, and the variations of the condensation heat transfer parameters and the vapor condensation length were analyzed. Results show that the convergent angle has an important influence on the condensation heat transfer parameters. Both Nusselt and Stanton numbers rose as the convergent angle went up from 0° to 40°. The increment in the convergent angle enhanced the condensation heat transfer coefficient from 1.06 to 4.8 times at the range of the vapor pressure from 1 atm to 3.6 atm. The increase in the inlet NCG mass fraction caused a reduction in the condensation heat transfer parameters. and its accumulation in the downstream where its mass fraction was over 90 %. The nozzle diameter and the inlet velocity and temperature of falling water column affected importantly the condensation heat transfer parameters. The vapor condensation length was increased with the rising inlet velocity. of falling water column, the vapor pressure and the nozzle diameter, while decreased with the ascending of the inlet NCG mass fraction and the convergent angle. The increment in the vapor pressure enhanced effectively the condensation heat transfer parameters, and weakened the adverse effect of NCG on the direct-contact condensation heat transfer.

A numerical study on convective condensation of flue gas in tubular heat exchangers

The accurate calculation of heat transfer process in the condensing heat exchanger plays a crucial role in the waste heat recovery. In this study, the convective-condensation heat transfer process in a condensing heat exchanger with five small heat exchangers is analyzed through utilizing a new numerical simulation model. The method that loads the latent heat of condensation as the heat generation rate is adopted. Under the two working conditions in this study, the deviations of outlet temperature between numerical and experimental results are 1.3 and 2.2 K, respectively, while the deviations of total condensate water flow are 8.5 % and 5.5 %, respectively. Under the drier working condition, the average temperature reduction (5.8 K) per row of tubes in the first small heat exchanger where no condensation occurs is higher than that (2.6 K) in the third small heat exchanger where the water vapor starts to condense. It indicates that the release of latent heat of condensation slows down the cooling rate of the flue gas. In the small heat exchanger where the water vapor starts to condense, the amount of condensate water on the wall of each row of tubes increases first and then decreases slowly along the flow direction of the flue gas.

Entropy generation analysis on condensation upward flow for hydrocarbon mixture in two types of helical wavy pipes

This paper proposed the application of two types of wavy structures for spiral wound heat exchanger, and conducted numerical simulations on the condensation flow of a hydrocarbon mixture with methane, ethane, and propane in them. The effects of saturation pressure and mass velocity are also studied. It was found that both types of helical wavy pipes produce higher condensation heat transfer coefficients and frictional pressure drop than those in helical smooth one, and both of them increase with the rise in mass velocity and the decrease of saturation pressure. The influence of saturation pressure on heat transfer and pressure drop is greater than that of mass velocity. Meanwhile, the comprehensive performance of the two types of helical wavy pipes is analyzed using entropy generation. It can be found that the horizontal wavy pipe has a better overall performance than vertical wavy one with a lower irreversible loss. Finally, prediction models for the condensation heat transfer coefficients and frictional pressure drops are established using RBF neural networks, with 95 % of the predicted results having a relative deviation within 10 %.

Experimental investigation of thermoelectric system with condensation heat transfer process

The objective of this study was to investigate the impact of vapor temperature, mass flow rate, concentration and turbulating insert on the performance of a thermoelectric generator/module (TEG/TEM) system. The researchers conducted experiments using a thermoelectric setup comprising 32 TEGs. Various experimental conditions were explored, including the electric connection type of the TEGs, inlet saturation steam temperature ranging from 70 °C to 100 °C, steam mass flow rate ranging from 4 kg/h to 16 kg/h, two different types of turbulators (Twisted Tape and Rod), and vapor gas concentration of 1 % to 3 %. The results of the study revealed several key findings. Firstly, the peak power output of the system increased with higher inlet steam temperatures. However, the power output was found to be nearly independent of the mass flow rate and the type of turbulator under the current experimental conditions. Among the different types of TEG module connections, connecting all TEG modules in series yielded the best performance compared to other connection types. Furthermore, the study found that TEMs positioned at different locations within the system produced approximately the same power output due to the high condensation heat transfer coefficient. This was supported by the power uniformity coefficient, which approached unity. Regarding the effect of vapor concentration, the presence of Marangoni effect led to an enhancement in harvested energy by 8 % when the gas phase vapor of the ethanol–water mixture was 1 %. Finally, the highest net efficiency of 1.64 % was achieved at a temperature of 100 °C and a vapor concentration of 1 %.

Experimental Evaluation of Condensation of R32 and R134a over a Plain Tube

The rise in demand for universal energy, combined with environmental concerns, prompted a search for a new technology that was compatible with the existing scenario. Nowadays, most conventional refrigerants are being phased out due to environmental restrictions, which has led to the development of alternative refrigerants. Such newly developed alternative refrigerants need further experimental assessment regarding their thermophysical properties. The current work has experimentally looked at the heat transfer phenomena that occur when the refrigerants R32 and R134a condense over a single horizontal plain tube at saturation temperatures of 40–50 °C, wall sub-cooling temperatures ranging from 3 °C to 11 °C, and heat fluxes of 8–31 kW/m2. The results showed that at a saturation temperature of 40 °C, R32 and R134a have a coefficient of condensation heat transfer about 4.0–9.0% higher than that at saturation temperatures of 45 °C and 50 °C. At the same wall sub-cooling temperature, R32 has a 50–55% higher condensing-side heat transfer coefficient than R134a. The validation of the experimental condensing-side heat transfer coefficient with Nusselt’s model revealed a deviation of ±10%. Further, a modified correlation based on Nusselt’s model predicted the experimental condensing-side heat transfer coefficient with an error band of ±5%.

An innovative ocean thermal energy conversion system with zeotropic Rankine cycle and direct contact membrane distillation for enhanced efficiency and sustainability

This research introduces an integrated ocean thermal energy conversion water and power cogeneration system (OTEC-WPCS), combining a Zeotropic Rankine Cycle (ZRC) with Direct Contact Membrane Distillation (DCMD) for efficient power and water production. The hydrofluoroolefins (HFOs), chosen for their zero ozone depletion potential (ODP) and extremely low global warming potential (GWP), are used as working fluid components in the ZRC. Additionally, DCMD is implemented for freshwater generation. A mathematical model is established, incorporating both thermodynamic and CFD simulations. The goal is to identify optimal operating conditions that maximize the output of the system. By coupling DCMD and ZRC in series, the system's efficiency reaches 8.92 %, an improvement of 5.71 % compared to a standalone ZRC system. This configuration allows for more efficient use of surface seawater heat compared to an ammonia-based Organic Rankine Cycle (ORC)-DCMD system. The enhancements include an increase in power and water production per unit mass flow of surface seawater by 0.55 kW/(kg·s) and 30 %, respectively. Over 60 % of the system's exergy destruction occurs in the DCMD modules and evaporator, while nearly 80 % of the capital cost is associated with the evaporator, condenser, and DCMD heat exchanger. Enhancing the DCMD module structure and heat exchanger can improve both energy and exergy efficiency, and economic feasibility.

Heat transfer characteristics in vertical tube condensers: Experimental investigation and numerical validation

The paper establishes a vertical steam condensation heat transfer experimental device to investigate the process of liquid film condensation heat transfer under the countercurrent heat transfer of a secondary coolant. An improved experimental method, integrating measurements and simulations, accurately calculates local heat transfer coefficients and heat flux. The validity of the data is confirmed through comparison with established condensation correlations, affirming the method's effectiveness. The correlations of previous research (i.e., Numrich, Carey, Oh, Lee, and Shah) demonstrate greater consistency with the experimental results, with mean relative deviations (MRD) of −4.90%, 7.18%, 11.42%, −8.63% −4.45%, and mean absolute relative deviations (MARD) of 11.61%, 21.57%, 23.60%, 18.97%, and 12.53%, respectively. Numrich's correlation demonstrated the closest congruence. Based on these results, the research proposes a new coupled heat transfer model, effectively simulating the interaction between external cooling water and steam condensation. This model simplifies the process by pre-defining coolant temperature changes per unit length, thereby reducing the need for extensive iterative calculations and eliminating assumptions about wall temperature. It accurately predicts the wall temperature, local condensing temperature, and coolant temperature in a vertical condenser. These experimental methods and models offer valuable insights for optimizing vertical condenser design and analysis. The study underscores the significance of combining simulation models with experimental measurements to enhance the understanding of heat transfer in complex systems. The findings promise to advance research in film condensation heat transfer and assist in condenser design and optimization.

Investigation of the effects surface alteration via coatings on the condensation heat transfer and wettability

Background Heat exchangers are a critical component in organic Rankine cyclic (ORC) geothermal power plants as they represent more than 50% of the capital. In this study, the thermal performance of coatings devised for condensation heat exchangers have been studied. Methods For this purpose, a mock-up heat exchanger rig was designed and fabricated. The coatings used for the trials are of hydrophobic nature, in order to promote a change in the heat transfer mode from film-wise condensation to drop-wise condensation. The coatings for this study were developed by chemical vapour deposition and magnetron sputtering on aluminium substrates. The wettability and adhesion of the coatings was characterized before and after the tests. Statistical analysis was used to analyse the heat transfer related data. Results The results indicate that the silica based coating produced an improvement in the heat transfer performance indicators and the working fluid caused a deterioration of the wetting properties. However, even at the end of the tests, the coated samples performed better than the substrate material in terms of heat transfer performance. Conclusions The results of this research prove that shifting from film-wise condensation to drop-wise condensation is viable method to improve heat transfer efficacy. However, a one to one correlation could not be established with water contact angles measured in water or diiodomethane suggesting that wettability properties in ORC fluid could differ to established in these conventional fluids for contact angle measurements.

Impact of condensate water recycling on the performance of open refrigerated display cabinet

The escalating global energy concerns have underscored the urgent need for energy conservation, particularly within the refrigerated industry. The imperative of optimizing the performance of open refrigerated display cabinets (ORDC) has become increasingly pronounced. This study sought to investigate the impact of condensate water recycling on ORDC operations through experiment, focusing on the influence of condensate water flowrate, temperature, and heat exchanger length on key performance indicators such as thermal entrainment factor (TEF), coefficient of performance (COP), and heat transfer efficiency enhancement (η). The findings revealed that the flowrate of condensate water wielded the most substantial impact on system performance, leading to noteworthy increases of 10.42% in COP and 7.05% in η, while TEF experienced a reduction of 4.33% within a flow rate range from 0 ml/min to 54 ml/min. Notably, an optimal flowrate of 54 ml/min was identified. Conversely, the temperature of condensate water exhibited minimal influence on system performance. Increasing the length of the heat exchanger demonstrated a linear correlation with improved system performance. In practical applications, the enhancements in COP, η, and TEF, compared to scenarios without a condensate water recycling system, ranged from 2.23% to 5.80%, 1.21% to 3.68%, and 0.37% to 2.09%, respectively.

Condensation heat recycling system for heat engines

THE RELEVANCE of the research lies in the need to use waste heat, which is a byproduct of the operation of energy machines, to increase the efficiency of their operation. Using the example of introducing a system for recovering condensation heat and using it in an air heating system, the possibility of beneficial use of waste heat generated by refrigeration machines used to freeze the ice arena of a sports complex was confirmed.TARGET. Development of a system for recycling the condensation heat of refrigeration machines to use waste heat when organizing air heating of a building.METHODS. Study of engineering systems for the possibility of beneficial use of low-grade heat. Organization of a system for recycling the condensation heat of refrigeration machines in a sports complex. Installation of a measuring stand, including, among other things, a heat meter, a heat calculator, a controller for transferring measurement results to a personal computer, carrying out the necessary calculations, their subsequent processing and analysis.RESULTS. At a facility with constant operation of refrigeration machines and a need for heating, a condensation heat recovery system has been introduced. The possibility of implementing the proposed system without long-term downtime of the main equipment is shown.CONCLUSION. The introduction of a condensation heat recovery system increased the energy efficiency of the system, which allowed for 2.6 million rubles. reduce utility bills of the heat supply organization, as well as reduce thermal pollution of the environment by at least 1.4 GW per year.

Evaluating the generality of machine learning-based universal models used for prediction of condensation heat transfer coefficient in mini/macro channels

This research concerns the development of universal models founded on machine learning to predict the condensation heat transfer coefficient. In this regard, a consolidated database has been employed encompassing 8340 data points which belong to the flow condensation inside mini/macro channels. The database consists of 25 working fluids with hydraulic diameters ranging from 0.42 to 20.8 mm, mass velocities ranging from 13.1 to 1400 Kg m−2 s− 1 and reduced pressures ranging from 0.03 to 0.9. Four machine learning regression models namely artificial neural network (ANN), gradient-boosted regression (GBR), random forest regression (RFR) and support vector regression (SVR) are trained utilizing the database, and subsequently their accuracy and generality are compared. A multitude of dimensionless parameters are regarded as features, while three parameters specifically the heat transfer coefficient, Nusselt number and Nusselt number correction factor are each considered individually as targets. Within each model, the optimal values of the important hyper-parameters are tuned through appropriate search methods. In order to evaluate the generality of the models, the idea is to sequentially exclude each individual database from the consolidated database. The comparison of accuracy and generality of the models reveals that the RFR model using Nusselt number correction factor as target with a mean absolute relative deviation (MARD) of 3.01 % exhibits the highest level of accuracy, whereas the RFR model employing Nusselt number as target with a MARD for the predicted excluded values equal to 19.49 % demonstrates the superior generality.

Nanorough Is Not Slippery Enough: Implications on Shedding and Heat Transfer.

Lowering droplet-surface interactions via the implementation of lubricant-infused surfaces (LISs) has received important attention in the past years. LISs offer enhanced droplet mobility with low sliding angles and the recently reported slippery Wenzel state, among others, empowered by the presence of the lubricant infused in between the structures, which eventually minimizes the direct interactions between liquid droplets and LISs. Current strategies to increase heat transfer during condensation phase-change relay on minimizing the thickness of the coating as well as enhancing condensate shedding. While further surface structuring may impose an additional heat transfer resistance, the presence of micro-structures eventually reduces the effective condensate-surface intimate interactions with the consequently decreased adhesion and enhanced shedding performance, which is investigated in this work. This is demonstrated by macroscopic and optical microscopy condensation experimental observations paying special attention at the liquid-lubricant and liquid-solid binary interactions at the droplet-LIS interface, which is further supported by a revisited force balance at the droplet triple contact line. Moreover, the occurrence of a condensation-coalescence-shedding regime is quantified for the first time with droplet growth rates one and two orders of magnitude greater than during condensation-coalescence and direct condensation regimes, respectively. Findings presented here are of great importance for the effective design and implementation of LISs via surface structure endowing accurate droplet mobility and control for applications such as anti-icing, self-cleaning, water harvesting, and/or liquid repellent surfaces as well as for condensation heat transfer.

SUTTERBY NANOFLUID FLOW WITH MICROORGANISMS AROUND A CURVED EXPANDING SURFACE THROUGH A POROUS MEDIUM: THERMAL DIFFUSION AND DIFFUSION THERMO IMPACTS

This study anticipates examining a slip bioconvective movement of a non-Newtonian Sutterby nanofluid (SF) layer with motile microorganisms, where the fluid layer flows over a curved stretching surface. The movement is taken across a permeable medium under the influence of thermal diffusion, diffusion thermo, an unchanged vertical magnetic field (MF), joule heating, thermal radiation, and chemical reactions. The mathematical construction comprises momentum, energy, nanoparticles volume fraction, and microorganism concentration equations along with linear slip velocity and applicable boundary conditions (BCs). The motivation of the problem concerns recent progress in curved electronics and microchip technology, which made a growing development of the remarkable weaknesses of traditional planar electronics, which concerns the importance of the current work. Furthermore, the implication of this work emerges from the participation of microorganisms in the flow over a curved surface and shares with the temperature, velocity, and nanoparticle system of equations. This prototype is widely applicable in some manufacturing and engineering mechanisms like conduits, sports balls, combustion, inflated broadcast, and flow-structure contact between hydrodynamics and aerodynamics. The configuration of nonlinear partial differential equations (PDEs) is converted into ordinary differential equations (ODEs) by consuming suitable similarity transformations. The resulting equations are numerically analyzed via the fourth-order Runge-Kutta (RK-4) in concurrence with the shooting technique. The graphical construction of the targeted distributions is analyzed to recognize the effects of the relevant material coefficients. As key outcomes, it is noted that the greater the curvature of the surface, the greater the temperature, velocity, microorganisms, and nanoparticle distributions. Correspondingly, the Soret and Dufour impacts are found to be the improvement coefficients of the heat and dampness of both nanoparticle and microorganism condensation. Additionally, heat transmission develops with almost all relevant parameters, which is a noteworthy finding that can benefit potential applications.

Influence of geometric factors on the heat transfer characteristics of two-phase thermosyphons

Thermosyphons are two-phase closed heat exchange systems that contain a certain amount of liquid and utilize the latent heat of vaporization and condensation to transfer heat between the heat source and the heat sink without any external devices. They are a type of heat pipe that lacks a capillary structure, so the return of the condensed coolant from the condensation zone to the heating zone is driven by gravitational forces. Due to the absence of a capillary structure, thermosyphons exhibit lower resistance to the movement of the vapor-liquid mixture from the heating zone to the condensation zone, as well as to the return flow of the condensate. A distinctive feature of such systems is their high equivalent thermal conductivity, which is several orders of magnitude greater than that of natural metals (such as copper or silver). Because of their superior heat transfer characteristics, thermosyphons are widely used in various technical fields, including the chemical and petroleum industries, electronics, telecommunications devices, energy storage systems, and geothermal heating systems, among others. This paper presents experimental data on the heat transfer characteristics of two-phase thermosyphons with an internal diameter of 9 mm and lengths of 500, 700, and 1000 mm, using water as the coolant. The filling ratio (Fr) varied from 0.3 to 1.2. The length of the condensation zone was the same for all thermosyphons. The study was conducted with the thermosyphons oriented vertically at an angle of 90° relative to the horizontal. The influence of the filling ratio and the effective length of the thermosyphons on the minimum thermal resistance, the maximum heat flux, and the equivalent thermal conductivity is analyzed.

Modifikovani Rankinov ciklus parne turbine bez odbacivanja toplote kondenzacije ciklusa, pokretan termokompresorom koji radi u oblasti vlažne pare

The disclosed concept relates to a novel modified and simplified steam-turbine Rankine cycle without rejection of the cycle waste heat of condensation, which is driven by a thermocompressor (ejector) operating in the wet-vapor region. The thus modified steam-turbine Rankine cycle can theoretically achieve the maximum possible thermal efficiency (~100%). The wet-vapor mixture circulating within the thermocompressor is being separated in a dedicated cylindrical separation tank, so that the saturated water is pumped to a water heater where it receives the cycle heat input, while the saturated vapor is expanded in a backpressure steam turbine producing useful mechanical work and is then recirculated back to the thermocompressor, where it is being re-pressurized by means of the primary fluid (pumped and heated saturated water). The concept can be applied to steam-turbine-cycle power-plants fueled by: coal or solid/liquid/gaseous fuel, waste heat, nuclear fuel (used by boiling water reactors, pressurized water reactors, pressurized heavy-water reactors, gas-cooled reactors, molten salt reactors or liquid-metal-cooled fast reactors) or renewable energy sources (Solar energy, biomass, geothermal). The concept can also be applied as the “bottoming” steam-turbine-cycle part of a combined gas-turbine/steam-turbine cycle power plant.

Removal pattern of particulate matter from condensing heat exchanger after wet desulfurization of coal-fired unit

The flue gas after wet desulfurization of coal-fired units still contains a large amount of particulate matter. Flue gas condensing heat exchangers are often used to further remove particulate matter. However, current research focuses on the overall removal effect of the heat exchangers, but ignores the difference of pollutant removal ability of the inner tube bundle along the flue gas-flow direction. This paper studied the correlation between pollutant removal and operating parameters of condensation heat exchanger, so as to make the removed amount of pollutants as large as possible. A field experimental platform was built on a 3 ? 350 MW supercritical circulating fluidized bed coal-fired unit. The total amount of pollutants removed between the 3rd and 6th rows of tube bundles from the inlet of the heat exchanger was the largest. The removal of particulate matter near the outlet of the heat exchanger was the smallest. The highest removal rate of filterable particulate matter reached 76 %. The proportion of condensable particulate matter in the total removal of particulate matter reached around 90%. The mass ratio of both H2SO4 and SO3 to the removed condensable particulate matter were more than 9 %.

Study of filmwise condensation heat transfer enhancement by removal of condensate using wettability difference

Study of filmwise condensation heat transfer enhancement by removal of condensate using wettability difference

Experimental study on enhancement condensation heat transfer in tube by foam metal in presence of non-condensable gas

Condensation heat transfer in tube is widely applied in industrial production, and the heat transfer process is often weakened by non-condensable gas (NCG) in actual production. Enhancing condensation heat transfer is beneficial to improve production efficiency, which has always been a hot topic in current research. Foam metal material with large specific surface area and good thermal conductivity is an ideal material to enhance heat transfer. In order to study enhancement heat transfer effect and optimize structure of foam metal, this paper investigated condensation heat transfer in tube strengthened by foam metal in presence of NCG experimentally. Section shape of foam metal is annular, and the pores per inch (PPI) of foam metals is 10, 15, 20 respectively. The effects of PPI value, steam/air mixture mass flow, and NCG mass fraction on heat transfer coefficient (HTC) and flow resistance are studied. The results reveal the following: (1) Compared with smooth tube, the foam metal enhances heat transfer significantly, and HTC increases by 1.5-2.3 times. (2) At same steam/air mixture mass flow, 10PPI foam metal tube has the highest HTC compared to others. (3) With increase of NCG mass fraction and PPI value, pressure drop increases and the HTC decreases. Based on experimental data, pressure drop and HTC correlations are developed. This paper provides an important technical basis for foam metal material application in enhancement heat transfer area.

Condensation heat transfer enhancement through durable, self-propelling fluorine-free silane-treated anodized surfaces

When two or more adjacent droplets coalesce, excess surface energy is generated, which can be converted into the kinetic energy of the merged droplet through a suitable nanostructure and the superhydrophobicity of the surface.

Multi-objective particle swarm optimization algorithm for data acquisition and system characteristics research of phase change thermal storage heat pump water heaters

In order to understand the multi-objective particle swarm optimization algorithm for data collection and system characteristics research of heat pump water heaters, the author proposes a multi-objective particle swarm optimization algorithm for data collection and system characteristics research of phase change thermal storage heat pump water heaters. The author first introduced the working principle of the phase change heat storage heat pump water heater, and then conducted a comparative experimental study on the performance of two types of heat pump water heater systems using pure paraffin phase change heat storage and water storage. They compared and analyzed the heat storage process, condensation heat recovery rate of the heat storage box, and comprehensive energy efficiency coefficient of the system under the refrigeration and heat recovery mode of the two types of heat pump water heater systems, on this basis, measures were proposed to improve the performance of pure paraffin phase change thermal storage hot water systems. At long last, the examination of exploratory information shows that the Rx of the water warm capacity framework is around 6% higher than that of the stage change warm capacity framework, and the framework COPt is likewise 20% higher than that of the stage change warm capacity framework, from this, it tends to be seen that the stage change heat capacity box has unfortunate intensity move proficiency, prompting a lessening in the presentation of the intensity siphon water radiator framework. Contrasted and customary water stockpiling heat siphon boiling water frameworks, unadulterated paraffin stage change capacity heat siphon high temp water frameworks lessen the volume of the intensity stockpiling tank, and the framework works somewhat flawlessly during the intensity stockpiling process. However, the system?s overall energy efficiency is impacted by the heat storage tank?s poor heat exchange effect and relatively low condensation heat recovery rate. The intensity move of the intensity stockpiling box can be upgraded by finning the winding curls in the intensity stockpiling box, embedding aluminum foil, adding extended graphite, and different measures to further develop the buildup heat recuperation rate, subsequently working on the general execution of the framework.