Empirical Correlation of Factors Influencing Departure From Nucleate Boiling in Steam-Water Mixtures Flowing in Vertical Round Tubes

1966 ◽  
Vol 88 (4) ◽  
pp. 367-373 ◽  
Author(s):  
D. Pasint ◽  
R. H. Pai
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Forced Convection ◽  
Mass Flow ◽  
Nucleate Boiling ◽  
Vertical Tube ◽  
Empirical Correlation ◽  
Factors Influencing ◽  
Vertical Tubes ◽  
Heated Length

An empirical correlation of forced convection DNB for steam-water mixtures between 500 and 3000 psia in uniformly heated vertical tubes is proposed. DNB quality is expressed in terms of pressure, mass flow, inlet enthalpy, heated length from inlet to DNB point, and tube dia. The experimental data of the authors at 2000–3000 psia, 250,000–1,000,000 lb/hr sq ft2 mass flow, and 40,000–180,000 Btu/hr sq ft heat flux, obtained from a 6 ft long, 3/4-in-ID electrically heated vertical tube, are correlated with other published results ranging from 500 to 2000 psia.

Critical Heat Flux Modeling in Forced Convection Boiling During Power Transients

1990 ◽  
Vol 112 (4) ◽  
pp. 1058-1062 ◽  
Author(s):  
K. O. Pasamehmetoglu ◽  
R. A. Nelson ◽  
F. S. Gunnerson
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Theoretical Prediction ◽  
Forced Convection ◽  
Critical Heat Flux ◽  
Nucleate Boiling ◽  
Convective Boiling ◽  
New Model ◽  
Semi Empirical

In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is exceptionally good. The new model also is compared with the semi-empirical transient CHF model in the literature.

Simple Model of Boiling Heat Transfer on Tubes in Large Pools

1997 ◽  
Vol 119 (2) ◽  
pp. 376-379 ◽  
Author(s):  
Y. Parlatan ◽  
U. S. Rohatgi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Atmospheric Pressure ◽  
Boiling Heat Transfer ◽  
Saturation Temperature ◽  
Flow Dynamics ◽  
Simple Method ◽  
Vertical Tubes

A simple method has been developed to model boiling heat transfer from a heat exchanger to pools using the experimental data available in the literature without modeling the flow dynamics of the pool. In this approach the heat flux outside vertical tubes is expressed as a function of outside wall temperature of the tubes and saturation temperature of the pool at or near atmospheric pressure.

Numerical Investigation of Heat and Mass Flux Effects on Heat Transfer Characteristics of Supercritical Water in an Upward Flow Vertical Tube

2014 ◽  
Vol 592-594 ◽  
pp. 1667-1671
Author(s):  
T. Vinoth ◽  
K. Karuppasamy ◽  
D. Santhosh Kumar ◽  
R. Dhanuskodi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Supercritical Water ◽  
Mass Flux ◽  
Vertical Tube ◽  
Upward Flow ◽  
Heat Transfer Characteristics ◽  
Ansys Fluent ◽  
Transfer Characteristics

In the present work, the heat transfer characteristics of supercritical pressure water are numerically investigated in an upward flow vertical smooth tube. The numerical simulations are carried out by using Ansys-Fluent solver. The objective of the present work is to investigate the effect of heat flux and mass flux on heat transfer characteristics in supercritical water. In order to perform numerical simulation, experimental data of Mokryet al.[2] is considered. Various simulations were carried out for the inlet parameters of temperature 350°C, pressure 240bar; heat flux values ranging from 190 to 884kW/m2and mass flux values ranging from 498 to 1499kg/m2s. Based on the available parameters of heat flux and mass flux, they are segregated as groups with heat flux to mass flux ratios of 0.39 and 0.67. According to computational data, the heat transfer enhancement and heat transfer deterioration phenomenon of supercritical water were analyzed and based on the comparison with experimental data; their occurrence and mechanism were addressed.

Critical Heat Flux of Steady Boiling for Subcooled Water Jet Impingement on the Flat Stagnation Zone

2004 ◽  
Vol 126 (2) ◽  
pp. 179-183 ◽  
Author(s):  
Zhen-Hua Liu ◽  
Tie-Feng Tong ◽  
Yu-Hao Qiu
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Jet Impingement ◽  
Nucleate Boiling ◽  
Water Jet ◽  
Stagnation Zone ◽  
Subcooled Water ◽  
Nozzle Size ◽  
Jet Nozzle

An experimental investigation was carried out for predicting the critical heat flux (CHF) of steady boiling for a round subcooled water jet impingement on the flat stagnation zone. The experimental data were measured in a steady nucleate boiling state. Three main influencing parameters, i.e., subcooling, impact velocity and jet nozzle size were widely changed and their effects on the critical heat flux were systemically studied. An empirical correlation was obtained using the experimental data over a wide experimental range for predicting the critical heat flux of steady boiling for a round subcooled water jet impingement on the flat stagnation zone.

The Onset of Flow Instability in Uniformly Heated Horizontal Microchannels

1999 ◽  
Vol 122 (1) ◽  
pp. 118-125 ◽  
Author(s):  
J. E. Kennedy ◽  
G. M. Roach, ◽  
M. F. Dowling ◽  
S. I. Abdel-Khalik ◽  
S. M. Ghiaasiaan ◽  
...  
Keyword(s):  
Heat Flux ◽  
Flow Instability ◽  
Experimental Parameter ◽  
Nucleate Boiling ◽  
Wall Heat Flux ◽  
Exit Pressure ◽  
Channel Exit ◽  
Demand Curves ◽  
Parameter Ranges ◽  
Heated Length

Onset of nucleate boiling and onset of flow instability in uniformly heated microchannels with subcooled water flow were experimentally investigated using 22-cm long tubular test sections, 1.17 mm and 1.45 mm in diameter, with a 16-cm long heated length. Important experimental parameter ranges were: 3.44 to 10.34 bar channel exit pressure; 800 to 4500 kg/m2s mass flux (1 to 5 m/s inlet velocity); 0 to 4.0 MW/m2 channel wall heat flux; and 7440–33,000 Peclet number at the onset of flow instability. Demand curves (pressure drop versus mass flow rate curves for fixed wall heat flux and channel exit pressure) were generated for the test sections, and were utilized for the specification of the onset of nucleate boiling and the onset of flow instability points. The obtained onset of nucleate boiling and onset of flow instability data are presented and compared with relevant widely used correlations. [S0022-1481(00)02101-0]

scholarly journals An experimental study on the subcooled flow boiling pressure drop of R141b in the system of two microchannels

2021 ◽  
Vol 2119 (1) ◽  
pp. 012053
Author(s):  
A. S. Shamirzaev
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Copper Block ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Boiling Incipience

Abstract An experimental study of the pressure drop under subcooled flow boiling of the refrigerant R141b in a system with two slotted microchannels was carried out. A copper block with two microchannels 2 mm wide, 0.4 mm deep, and 16 mm long was used as an experimental section for testing. The mass flow rate varied in the range from 1 to 4 g/s, the initial subcooling from 20°C to 50°C. Experimental data show a significant decrease in the pressure drop when the critical heat flux is reached. The experimental data are compared with the model known from the literature. Experimental data show that the occurrence of nucleate boiling incipience at subcooled boiling corresponds to a larger heat flux than that given by the recommended correlation.

Investigation of the Dynamics of Nucleate Boiling in Subcooled Falling Liquid Films

2014 ◽  
Vol 9 (2) ◽  
pp. 145-155
Author(s):  
Vladimir Serdyukov ◽  
Anton Surtaev ◽  
Oleg Volodin
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Strong Dependence ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Liquid Films ◽  
Heat Fluxes ◽  
Nucleation Frequency ◽  
Water Films ◽  
Falling Liquid Films

This paper deals with the features of nucleation dynamics at boiling in falling water films at different subcooling, Reynolds number and heat fluxes. With the use of high-speed infrared and digital video the local parameters of nucleate boiling in falling liquid films such as: bubbles’ diameter before condensation, frequency of nucleation and temperature of onset of bubble appearance were received. Analysis of the experimental data showed that bubbles’ diameter before condensation has strong dependence on initial temperature and increases with the rise of heat flux. The main influence on nucleation frequency has the variation of heat flux density. At the same time the experimental data on nucleation frequency in falling water films are close to the frequency of nucleation at pool boiling. To identify the main features the comparison of received data on the local characteristics at boiling in subcooled falling liquid film with existing models for pool boiling was made

A Heat Flux Correlation for Spray Cooling in the Nucleate Boiling Regime

2000 ◽  
Author(s):  
E. Cabrera ◽  
J. E. Gonzalez
Keyword(s):  
Heat Flux ◽  
Surface Roughness ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Ambient Pressure ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Boiling Regime

Abstract In this work an experimental study of spray cooling using monodispersed droplet sprays impinging on a flat and heated surface is reported. The aim of the work was to formulate an empirical model describing the heat flux (HF) for the nucleate boiling regime. Monodispersed water droplets with a known diameter and velocity, produced by a droplet generator, were directed toward a heated surface and the heat transfer was registered using a data acquisition system. The resulting high heat flux was investigated as function of the droplets’ diameter and velocity, mass flow rate, ambient pressure, subcooling degree and surface roughness. The resulting matrix of variables investigated in the experiments included; mass flux rate (340 < ṁ″ < 750 kg/m2s), subcooling degree (25 < Tsub < 78 °C), ambient pressure (1 < P < 1.8 bar), and surface roughness (79 < Rt < 5 μm). A generalized correlation was developed for the dimensionless HF as function of the dimensionless mass flow rate, temperature, surface roughness and pressure, along with the Jacob number. The form of the correlation is q ˙ ″ ρ V h f g = 0.245 ( Ja ) 1.038 ( Δ T sub Δ T sat ) 0.491 ( ρ σ m ˙ μ 3 ) 0.133 ( R t D ) 0.0213 ( P P 0 ) 0.291 having a confidence level greater than 95%, the differences between predicted and experimental HF were less than ±19%.

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