scholarly journals Assessment of steam condensation model with the presence of non-condensable gas in a vertical tube using RELAP5 Mod 3.2 code and MIT exp. Data

2014 ◽  
Vol 4 (3) ◽  
pp. 7-18
Author(s):  
V.T. Nguyen ◽  
H.T. Trinh
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Heat Removal ◽  
Vertical Tube ◽  
Saturated Steam ◽  
Film Condensation ◽  
Primary Concern ◽  
Transfer Coefficients ◽  
Mixture Flow ◽  
Plant Safety

The non-condensable gas effect is a primary concern in some passive systems used in advanced design concepts, such as the Passive Residual Heat Removal System (PRHRS) of AP1000, APR1400, AES-2006, the Passive Containment Cooling System (PCCS) of AP1000 design, and Isolation Condensation System (ICS) of ESBWR design. The accumulation of the non-condensable gas inside the condensing tubes can significantly reduce the level of heat transfer which affects the heat removal capacity in accident condition and impacts plant safety. The objective of the present work is to assess the analysis capability of two wall film condensation models of RELAP5/Mod3.2 with the presence of non-condensable gas in a vertical tube on condensation experiments performed at MIT, USA. The results of the simulations and experimental data show the similar tendencies that the heat transfer coefficients increase as the inlet steam-non condensable gas mixture flow rate increases, the inlet steam-non-condensable gas mass fraction decrease, and the inlet saturated steam temperature decrease

An Analytical Study of Laminar Film Condensation: Part 2—Single and Multiple Horizontal Tubes

1961 ◽  
Vol 83 (1) ◽  
pp. 55-60 ◽  
Author(s):  
Michael Ming Chen
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Horizontal Tube ◽  
Vertical Tube ◽  
Film Condensation ◽  
Transfer Coefficients ◽  
Inertia Effects ◽  
Horizontal Tubes ◽  
Laminar Film ◽  
Laminar Film Condensation

The boundary-layer equations for laminar film condensation are solved for (a) a single horizontal tube, and (b) a vertical bank of horizontal tubes. For the single-tube case, the inertia effects are included and the vapor is assumed to be stationary outside the vapor boundary layer. Velocity and temperature profiles are obtained for the case μvρv/μρ ≪ 1 and similarity is found to exist exactly near the top stagnation point, and approximately for the most part of the tube. Heat-transfer results computed with these similar profiles are presented and discussed. For the multiple-tube case, the analysis includes the effect of condensation between tubes, which is shown to be partly responsible for the high observed heat-transfer rate for vertical tube banks. The inertia effects are neglected due to the insufficiency of boundary-layer theory in this case. Heat-transfer coefficients are presented and compared with experiments. The theoretical results for both cases are also presented in approximate formulas for ease of application.

Experimental Study of Non-Condensable Effect on Passive Condenser System

2007 ◽  
Author(s):  
Wenzhong Zhou ◽  
Shripad T. Revankar
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Heat Removal ◽  
Scaling Analysis ◽  
Steam Condensation ◽  
Transfer Coefficients ◽  
Specific Design ◽  
Heat Transfer Coefficients ◽  
Removal Capacity ◽  
Safety Systems

One of the engineered safety systems in the advanced boiling water reactor is a passive containment cooling system (PCCS) which is composed of a number of vertical heat exchanger. A set of steam condensation experiments is conducted to evaluate the heat removal capacity of a PCCS condenser. A condensing tube is submerged in a water pool where condensation heat is transferred by secondary boiling heat transfer. The specific design of condensing tube is based on scaling analysis from the PCCS design of ESBWR. The two condensing tubes have same height (0.9m) but different inside diameters, 26.6mm and 52.5mm, respectively. Condensation heat transfer coefficients (HTC) are obtained under various test conditions, such as different primary pressure (150 – 450 kPa), inlet steam flow rate (1 – 5 g/s), air mass fraction (0 – 20%) and tube size (26.6 mm and 52.5 mm ID). The effects of these parameters to condensation performance are evaluated.

Microjet Impingement Cooling With Phase Change

2004 ◽  
Author(s):  
Evelyn N. Wang ◽  
Juan G. Santiago ◽  
Kenneth E. Goodson ◽  
Thomas W. Kenny
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Heated Surface ◽  
Heat Removal ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Impingement Cooling ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Wall Superheat

The large heat generation rates in contemporary microprocessors require new thermal management solutions. Two-phase microjet impingement cooling promises high heat transfer coefficients and effective cooling of hotspots. We have fabricated integrated microjet structures with heaters and temperature sensors to study local heat transfer at the impingement surface of a confined microjet. Circular jets with diameters less than 100 μm are machined in glass. Preliminary temperature measurements (for Rej = 100–500) suggest that heat transfer coefficients of 1000 W/m2C close to the jet stagnation zone can be achieved. As the flowrate of the jet is increased, a tradeoff in heat removal capability and wall superheat is observed. To aid in understanding the mechanism for wall superheat during boiling at the heated surface, the devices allow for optical access through the top of the device. However, the formation of vapor from the top reservoir makes visualization difficult. This study aids in the design of microjet heat sinks used for integration into a closed-loop cooling system.

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

Thermal Analysis of Cooling System in a Gas Turbine Transition Piece

2011 ◽  
Author(s):  
Jun Su Park ◽  
Namgeon Yun ◽  
Hokyu Moon ◽  
Kyung Min Kim ◽  
Sin-Ho Kang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Thermal Stresses ◽  
Cooling System ◽  
Structural Information ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Transfer Coefficients ◽  
Transition Piece ◽  
Inlet Conditions

This paper presents thermal analyses of the cooling system of a transition piece, which is one of the primary hot components in a gas turbine engine. The thermal analyses include heat transfer distributions induced by heat and fluid flow, temperature, and thermal stresses. The purpose of this study is to provide basic thermal and structural information on transition piece, to facilitate their maintenance and repair. The study is carried out primarily by numerical methods, using the commercial software, Fluent and ANSYS. First, the combustion field in a combustion liner with nine fuel nozzles is analyzed to determine the inlet conditions of a transition piece. Using the results of this analysis, pressure distributions inside a transition piece are calculated. The outside of the transition piece in a dump diffuser system is also analyzed. Information on the pressure differences is then used to obtain data on cooling channel flow (one of the methods for cooling a transition piece). The cooling channels have exit holes that function as film-cooling holes. Thermal and flow analyses are carried out on the inside of a film-cooled transition piece. The results are used to investigate the adjacent temperatures and wall heat transfer coefficients inside the transition piece. Overall temperature and thermal stress distributions of the transition piece are obtained. These results will provide a direction to improve thermal design of transition piece.

Cooling of a Finned Cylinder by a Jet Flow of Air

2002 ◽  
Author(s):  
F. Gori ◽  
F. De Nigris ◽  
E. Pippione ◽  
G. Scavarda
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Jet Flow ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Electric System ◽  
Heavy Trucks ◽  
Turbo Compressor ◽  
University Of Rome ◽  
The University

The paper describes a patented proposal to use jets of air in the cooling system of heavy trucks. Preliminary tests have been carried out, in the Heat Transfer Laboratory of the University of Rome “Tor Vergata”, to evaluate the heat transfer characteristics of a jet flow of air, impinging onto an externally finned cylinder. The cylinder is internally heated with an electric system. Thermocouples, located inside the cylinder, allow to measure the wall temperatures, in order to calculate the local and average convective heat transfer coefficients. A preliminary design of the practical apparatus, applied to heavy trucks, has been done in cooperation with Iveco. Nozzles are designed to be put after the fan of heavy trucks to converge air, in the form of jets, onto the tube where the charged air is flowing from the outlet of the turbo-compressor. The efficiency of the jet flow increases the cooling performances but, due to the high temperature at the outlet of the turbo-compressor, it may not be enough. The heat transfer cooling performances are enhanced if the tube to be cooled is externally finned. Some preliminary experiments have been carried out in a real scale bank test of an heavy truck engine at the Engineering Testing Laboratories Department of Iveco. Comparisons are done between the experiments and a simple theoretical model. Some conclusions are drawn about the cooling at different fluid dynamics conditions of the impinging jets.

Heat Transfer Measurements in an Internal Cooling System Using a Transient Technique With Infrared Thermography

2012 ◽  
Author(s):  
Christian Egger ◽  
Jens von Wolfersdorf ◽  
Martin Schnieder
Keyword(s):  
Heat Transfer ◽  
Data Analysis ◽  
Infrared Thermography ◽  
Outer Surface ◽  
Cooling System ◽  
Internal Cooling ◽  
Test Model ◽  
Cooling Channel ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

In this paper a transient method for measuring heat transfer coefficients in internal cooling systems using infrared thermography is applied. The experiments are performed with a two-pass internal cooling channel connected by a 180° bend. The leading edge and the trailing edge consist of trapezoidal and nearly rectangular cross sections, respectively, to achieve an engine-similar configuration. Within the channels rib arrangements are considered for heat transfer enhancement. The test model is made of metallic material. During the experiment the cooling channels are heated by the internal flow. The surface temperature response of the cooling channel walls is measured on the outer surface by infrared thermography. Additionally, fluid temperatures as well as fluid and solid properties are determined for the data analysis. The method for determining the distribution of internal heat transfer coefficients is based on a lumped capacitance approach which considers lateral conduction in the cooling system walls as well as natural convection and radiation heat transfer on the outer surface. Because of time-dependent effects a sensitivity analysis is performed to identify optimal time periods for data analysis. Results are compared with available literature data.

scholarly journals Analysis of Wetting Characteristics on Microstructured Hydrophobic Surfaces for the Passive Containment Cooling System

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Wei Zhao ◽  
Xiang Zhang ◽  
Chunlai Tian ◽  
Zhan Gao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Cooling System ◽  
Heat Removal ◽  
Interface State ◽  
Transfer Performance ◽  
Hydrophobic Property ◽  
High Mechanical Strength ◽  
Feasible Solutions ◽  
Baxter Model

As the heat transfer surface in the passive containment cooling system, the anticorrosion coating (AC) of steel containment vessel (CV) must meet the requirements on heat transfer performance. One of the wall surface ACs with simple structure, high mechanical strength, and well hydrophobic characteristics, which is conductive to form dropwise condensation, is significant for the heat removal of the CV. In this paper, the grooved structures on silicon wafers by lithographic methods are systematically prepared to investigate the effects of microstructures on the hydrophobic property of the surfaces. The results show that the hydrophobicity is dramatically improved in comparison with the conventional Wenzel and Cassie-Baxter model. In addition, the experimental results are successfully explained by the interface state effect. As a consequence, it is indicated that favorable hydrophobicity can be obtained even if the surface is with lower roughness and without any chemical modifications, which provides feasible solutions for improving the heat transfer performance of CV.

Evaluation of Numerical Methods to Predict Temperature Distributions of an Experimentally Investigated Convection-Cooled Gas-Turbine Blade

2017 ◽  
Author(s):  
E. Findeisen ◽  
B. Woerz ◽  
M. Wieler ◽  
P. Jeschke ◽  
M. Rabs
Keyword(s):  
Heat Transfer ◽  
Numerical Methods ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Gas Turbines ◽  
Cooling System ◽  
Fe Model ◽  
Gas Turbine Blade ◽  
Transfer Coefficients ◽  
Temperature Distributions

This paper presents two different numerical methods to predict the thermal load of a convection-cooled gas-turbine blade under realistic operating temperature conditions. The subject of the investigation is a gas-turbine rotor blade equipped with an academic convection-cooling system and investigated at a cascade test-rig. It consists of three cooling channels, which are connected outside the blade, so allowing cooling air temperature measurements. Both methods use FE models to obtain the temperature distribution of the solid blade. The difference between these methods lies in the generation of the heat transfer coefficients along the cooling channel walls which serve as a boundary condition for the FE model. One method, referred to as the FEM1D method, uses empirical one-dimensional correlations known from the available literature. The other method, the FEM2D method, uses three-dimensional CFD simulations to obtain two-dimensional heat transfer coefficient distributions. The numerical results are compared to each other as well as to experimental data, so that the benefits and limitations of each method can be shown and validated. Overall, this paper provides an evaluation of the different methods which are used to predict temperature distributions in convection-cooled gas-turbines with regard to accuracy, numerical cost and the limitations of each method. The temperature profiles obtained in all methods generally show good agreement with the experiments. However, the more detailed methods produce more accurate results by causing higher numerical costs.

A Compact Nanostructure Integrated Pool Boiler for Microscale Cooling Applications

2009 ◽  
Author(s):  
Muhsincan S¸es¸en ◽  
Cem Baha Akkartal ◽  
Wisam Khudhayer ◽  
Tansel Karabacak ◽  
Ali Kos¸ar
Keyword(s):  
Heat Transfer ◽  
Surface Temperature ◽  
High Efficiency ◽  
Cooling System ◽  
Bubble Formation ◽  
Heat Removal ◽  
Nucleate Boiling ◽  
External Energy ◽  
Excessive Heat ◽  
Aluminum Base

An efficient cooling system consisting of a plate, on which copper nanorods (nanorods of size ∼100nm) are integrated to copper thin film (which is deposited on Silicon substrate), a heater, an Aluminum base, and a pool was developed. Heat is transferred with high efficiency to the liquid within the pool above the base through the plate by boiling heat transfer. Near the boiling temperature of the fluid, vapor bubbles started to form with the existence of wall superheat. Phase change took place near the nanostructured plate, where the bubbles emerged from. Bubble formation and bubble motion inside the pool created an effective heat transfer from the plate surface to the pool. Nucleate boiling took place on the surface of the nanostructured plate helping the heat removal from the system to the liquid above. The heat transfer from nanostructured plate was studied using the experimental setup. The temperatures were recorded from the readings of thermocouples, which were successfully integrated to the system. The surface temperature at boiling inception was 102.1°C without the nanostructured plate while the surface temperature was successfully decreased to near 100°C with the existence of the nanostructured plate. In this study, it was proved that this device could have the potential to be an extremely useful device for small and excessive heat generating devices such as MEMS or Micro-processors. This device does not require any external energy to assist heat removal which is a great advantage compared to its counterparts.

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