Comprehensive review of pure vapour condensation outside of horizontal smooth tubes (original) (raw)
Related papers
International Journal of Energy Research, 2005
Energy and mass transfer to a column of condensate draining by gravity between two successive tubes has been analysed theoretically. The results of the model agree well with previous experimental data where the variation in condensate temperature with distance from the upper tube was measured. The analysis provides a basic tool for the thermal analysis of inundated tubes by eliminating the need to make assumptions about the condensate inundation temperature and mass flow rate on such tubes.
Condensation in a vertical tube bundle passive condenser – Part 1: Through flow condensation
International Journal of Heat and Mass Transfer, 2010
An experimental study and a boundary layer analysis were performed for the steam condensation in a vertical tube bundle passive condenser operating in a through flow mode. Four condenser tubes were submerged in a water pool and the heat from the condenser tube was removed through boiling. Experimental data were obtained for various system pressures (100-170 kPa), inlet steam flow rates (15-47 g/s) and non-condensable gas concentration (0-15%). The experimental results showed substantial deterioration in condensation when non-condensable gas was present. With increase in steam flow rate and system pressure the condensate rate increased. The boundary layer thickness and non-condensable gas concentration increased along the condenser tube length.
Numerical investigation of condensation in inclined tube air-cooled condensers
Applied Thermal Engineering, 2017
Air-cooled condensers (ACC) have the potential to drastically reduce water consumption in power plants using a steam Rankine cycle operating; however, there are very few comprehensive models to simultaneously describe the heat and mass transfer effects for both the air and steam domains. This paper presents a coupled model for laminar film condensation and air side convective cooling for an inclined air cooled condenser tube. The air-side fluid flow is modeled using ANSYS Fluent. A Nusselt thin film analysis is then used to describe the film thickness in the upper region of the tube interior with a pool condensation model used to define the axial flow in the lower region. The commonly used isothermal boundary condition is relaxed by applying the heat transfer at the tube surface on the air-side to the inside tube surface during the film analysis to investigate the impact on the local film thickness and the overall heat transfer coefficient of the condenser. The results are related to the heat transfer on both staggered and inline tube configurations.
Volume 2: Heat Transfer Enhancement for Practical Applications; Heat and Mass Transfer in Fire and Combustion; Heat Transfer in Multiphase Systems; Heat and Mass Transfer in Biotechnology, 2013
Heat exchangers using in-tube condensation have great significance in the refrigeration, automotive and process industries. Effective heat exchangers have been rapidly developed due to the demand for more compact systems, higher energy efficiency, lower material costs and other economic incentives. Enhanced surfaces, displaced enhancement devices, swirl-flow devices and surface tension devices improve the heat transfer coefficients in these heat exchangers. This study is a critical review on the determination of the condensation heat transfer coefficient of pure refrigerants flowing in vertical and horizontal tubes. The authors' previous publications on this issue, including the experimental, theoretical and numerical analyses are summarized here. The lengths of the vertical and horizontal test sections varied between 0.5 m and 4 m countercurrent flow double-tube heat exchangers with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The measured data are compared to theoretical and numerical predictions based on the solution of the artificial intelligence methods and CFD analyses for the condensation process in the smooth and enhanced tubes. The theoretical
Refrigerant forced-convection condensation inside horizontal tubes
1969
Condensing heat transfer rates inside a horizontal tube were investigated-for large quality changes across the tube. The proposed correlation is a modification of the work of Rohsenow, Webber and Ling [29]. The result of the investigation is modified through new variables which include the effect of the true axial pressure gradient in a tube. Experimental data are presented for a range of flow conditions. A 0.493 in. ID, 19.75 ft. long nickel tube was used for condensing Refrigerant-12. The saturation temperature was varied from 84.6*F to 118*F and flow rates of vapor-liquid mixture ranged from 151,000 lbm/ft 2hr to 555,000 lbm/ft 2hr. The inlet quality was essentially 100% at saturation and exit qualities ranged from 50% to zero and subcooled liquid. The test results for average heat transfer coefficient ware correlated by the analysis within 15%. NOMENCLATURE A Cross section area ft 2 c Specific heat Btu/lbm *F D Tube inner diameter ft D. Tube outer diameter ft f Friction factor F. Pressure Gradient in the Tube lbf/ft 2/ft g Gravity ft/sec 2 2 G Mass velocity of the liquid lbm/hr ft G vMass velocity of the vapor ibm/hr ft 2 h fg Latent heat of the evaporation Btu/lbm h Local heat transfer coefficient Btu/hr ft 2 *F z k Conductivity of the liquid Btu/hr ft *F L Length of the cooling water jacket ft Nu Nusselt Number Pr Prandtl Number (q/A) Heat flux Btu/ft 2hr Re Reynolds Number T Inner wall temperature *F T Outer wall temperature *F AT Temperature difference between vapor and condensing wall AT Cooling water temperature rise *F Vz Velocity of the condensate flow ft/sec W Flow rate of the fluid lbm/hr W Flow rate of the cooling water lbm/hr w z Distance from condensation starting point ft 0075 62.3 73 62.32 a [ I p MNIMIIIMIIIIMMMINII M ON110111101111111i
A dataset of steam condensation over a double enhanced tube bundle under vacuum
Applied Thermal Engineering, 2004
Low pressure steam condensation on a double enhanced copper nickel tube bundle under loaded conditions. Energy balance indicates the accuracy of the dataset to within 10%. Checks on shell side measurements indicate they are of good quality. A comparison is made with the Nusselt model on plain copper tubes and with data from previous plain stainless steel tubes. Previous research on steam condensation indicates the tube side resistance is usually dominant. However, on the double enhanced tube bundle, the condensate film resistance is controlling. There is no marked improvement by the double enhanced tubes while using water as the process fluid. It is postulated that high surface tension fluids, such as water, cause fin inundation (thicker condensate film) and negates any heat transfer enhancement.
An experimental study of filmwise condensation on horizontal enhanced condenser tubing
Masters Thesis, 1979
SECUR1TY CLASSIVICATI@M OIF TMgS WAGE fMile DOI* 11SO (NP-9-79-%14 xperimental tudy Of-lmwise Master's 4hja 1aht on On HorizdWMal Enharced Cond~Iser ____________ Tubing# * 0".O~e~ e 5902 kum lbHuseyin/Ciftci 9. 0696PORMwuw ORGANIZATION MA01 ANA ADDRESS 10-ON. PRANW01j.EUEY.j PRJECT. TASN Naval Postgraduate School 653,91 Monterey, California 93940 02499G7 14. MONITORING AGENCY NAME 6 A000911110 deill*#f 00001 CORIMdte Of"0) 1S. S9CuRITY CLASS. (of Oft-as Approved for public release; distribution unlimited. to. SUPOLEMEN11TARY MOTES It. KEYV WORDS rCafteftne ave Vrn old* o RSO" adn~ad IMon~ep or No num~u.) Filmwise Condensation Augmented Heat Transfer Condenser so. 1ftTRACT eC..mtee n g e od It oe...mv ande
Condensation heat transfer coefficients of enhanced tubes.
In solar power generating plants, dry cooling towers are used when there is scarcity of water. Normally, condensation of the steam occurs in dry cooling towers in tubes at inclined angles. Almost all the previous work on condensation was in horizontal and vertical tubes until recently when work was done on condensation in inclined tubes but limited to smooth tubes and one type of enhanced tube. The purpose of this paper is to continue on previous work and present heat transfer coefficients and pressure drops during the condensation of R134a in an enhanced tube of inner diameter of 8.67mm with 60 fins with height of 0.22mm spiraled at an angle of 37 o. The experiments were conducted at condensing temperatures of 30 o C and 40 o C at mass fluxes between 300 kg/m 2 s and 400 kg/m 2 s and various vapour qualities. It was found that the heat transfer coefficients and pressure drops increased with mean quality. Overall, the heat transfer enhancement factors were between 2.1 and 2.9 and the pressure drop penalty factors were between 1.2 and 1.8 with the enhancement more pronounced at lower mass fluxes. Finally, the heat transfer and pressure drops increased with decrease in condensing temperature.
Numerical performance evaluation of a delugeable flat bare tube air-cooled steam condenser bundle
2015
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Validation of in-tube condensation performance
2002
This paper reports on the condensation heat transfer and pressure drop performance of a heat pump water heater operating with R-22 at an average saturation temperature of 40°C with mass fluxes ranging from 300 - 800kg/m 2 s. The purpose of the experimental work was to validate the effectiveness of a computerized data acquisition system, as well as to establish a sound experimental procedure. Experimental flow regimes were determined using a well-known flow regime predictor. This showed that the experimental data points lay mainly in the annular flow region. The experimental heat transfer coefficients and pressure drops were compared with widely used correlations, and good agreement was obtained.