A Mechanistic Condensation Model for a Passive Condenser System

2005 ◽  
Author(s):  
Seungmin Oh ◽  
Shripad T. Revankar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Rate ◽  
Transfer Rate ◽  
Mass Fraction ◽  
Condensation Heat Transfer ◽  
Condenser Tube ◽  
Noncondensable Gas ◽  
System Pressure ◽  
Condensation Heat Transfer Coefficient

An experimental study is conducted and a mechanistic model is developed to investigate the effect of noncondensable gas in a passive condenser system. A vertical condenser tube was submerged in a water pool where the heat from the condenser tube was removed through boiling heat transfer. Data was obtained for various process parameters such as inlet steam flow rate, noncondensable gas mass fraction, and system pressure. Degradation of the condensation with noncondensable gas was investigated, where condensation heat transfer coefficient and heat transfer rate decrease with the noncondensable gas. It was found that the condensation heat transfer rate is enhanced by increasing the inlet steam flow rate and the system pressure. A mechanistic condensation correlation is developed which contains the major heat transfer components in its functional relationships. The heat transfers for the film region and the gas region sensible heat were modeled with the modified Nusselt solution and the single phase heat transfer correlations, respectively. The gas region condensation was correlated with bulk noncondensable mass fraction, gas region Reynolds number, and Jakob number. New correlation was compared with available experimental data and models. Mean errors of the correlation were found to be 4.7% and 13.4% for the tube average and the local condensation heat transfer coefficient, respectively.

Prediction of Bundle Shell Side Condensation Heat Transfer Coefficient

2008 ◽  
Author(s):  
Tailian Chen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Reasonable Agreement ◽  
Condensation Heat Transfer ◽  
Condenser Tube ◽  
Shell Side ◽  
3 Dimensional ◽  
Design Engineers ◽  
Condensation Heat Transfer Coefficient

Prediction of condenser bundle performance is of great interest to chiller design engineers and tube developers as well. Depending on their locations in a condenser bundle, tubes are subjected to inundation or flooding of condensate coming from those above them. The tubes located in the top portion of the bundle are not or slightly inundated whereas the tubes located deep in the bundle experience larger degree of inundation; those in the bundle bottom are the most severely inundated. For a condenser bundle to have good performance, it is necessary for the tubes to perform well in both non-inundated and inundated conditions. In this paper, the outside condensation heat transfer coefficient and its sensitivity to inundation for a condenser tube of enhanced 3-dimensional (3D) outside fins were measured. Based on the single tube measurements, shell side condensation performance of a condenser bundle was predicted. The predicted bundle outside heat transfer coefficient has a reasonable agreement with that of a condenser tested in a 500-ton chiller.

Influence of Wall Sub-Cooling on Local Heat Transfer for Forced Convection Condensation of Steam/Air in a Horizontal Tube

2016 ◽  
Author(s):  
Huiqiang Xu ◽  
Qiunan Sun ◽  
Haifeng Gu ◽  
Xiaofan Hou ◽  
Zhongning Sun
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Fraction ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Condensation Heat Transfer ◽  
Fraction Mixture ◽  
Condensation Heat Transfer Coefficient

For the purpose of analyzing the influence of wall sub-cooling on condensation heat transfer characteristic in the presence of noncondensable gases inside a horizontal tube, experiments for air-cooling and water-cooling at the secondary side outside the condenser tube have been conducted. By comparing the experimental data of different inlet air mass fraction, mixture gases velocity and coolant volume flow rate, the variation of local heat transfer coefficient with wall sub-cooling was obtained. The results show that for annular and wavy flow, the condensation heat transfer coefficient increases with increasing wall sub-cooling but decreases for stratified flow. For annular and wavy flow, the positive influence of wall sub-cooling on condensation heat transfer coefficient is enhanced by the rise of inlet noncondensable gas mass fraction, mixture gases velocity and pressure.

Roll Wave Effects on Annular Condensing Heat Transfer in Horizontal PCCS Condenser Tube

2002 ◽  
Author(s):  
Masaya Kondo ◽  
Hideo Nakamura ◽  
Yoshinari Anoda ◽  
Sadanori Saishu ◽  
Hiroyuki Obata ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Annular Flow ◽  
Cooling System ◽  
Condensation Heat Transfer ◽  
Transfer Model ◽  
Condenser Tube ◽  
Condensing Heat Transfer ◽  
Condensation Heat Transfer Coefficient

A horizontal in-tube condensation heat exchanger is under investigation to be used for a passive containment cooling system (PCCS) of a next generation-type BWR. The flow conditions in the horizontal condenser tube were observed both visually and by local void fraction fluctuation. The observed flow regimes at a rated condition were annular flow at the tube inlet, and turned gradually into wavy flow and smooth stratified flow along the length of the tube. It was found further that frequency of the roll waves that appear on the liquid film in the annular flow is closely related to the measured local condensation heat transfer coefficient. Based on the flow observation, the roll wave frequency and measured condensation heat transfer coefficient, a model is proposed which predicts the condensation heat transfer coefficient particularly for annular flows around the tube inlet region. The proposed heat transfer model predicts well the influences of pressure, local gas-phase velocity and film thickness.

Effect of Vibration on Condensation Heat Transfer to a Horizontal Tube

1969 ◽  
Vol 184 (1) ◽  
pp. 99-106 ◽  
Author(s):  
J. C. Dent
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Exploratory Study ◽  
Field Experiments ◽  
Horizontal Tube ◽  
Condensation Heat Transfer ◽  
Condenser Tube ◽  
Frequency Range ◽  
Experimental Findings ◽  
Condensation Heat Transfer Coefficient

An exploratory study was carried out on the condensation of air-free steam at a pressure slightly above atmospheric, on a horizontal condenser tube vibrating in the plane of the gravitational field. Experiments conducted in the frequency range 20-80 Hz with maximum amplitudes up to 0.17 in, showed that the condensation heat transfer coefficient increased with increasing intensity ( af) of vibration, up to a maximum of about 15 per cent, above the vibration-free value. A perturbation analysis verified the experimental findings. Because of the small observed increases in heat transfer, it can be concluded that tube vibration effects on condensation heat transfer in power plant condensers will be negligible.

scholarly journals The Investigation on Heat Transfer Characteristics of Steam Condensation in Presence of Noncondensable Gas under Natural Convection

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Xizhen Ma ◽  
Jiang Ma ◽  
Heng Tong ◽  
Haijun Jia
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Natural Convection ◽  
Transfer Coefficient ◽  
Molar Fraction ◽  
Condensation Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Steam Condensation ◽  
Noncondensable Gas ◽  
Condensation Heat Transfer Coefficient

The NHR-200 reactor in China adopts the noncondensable gas self-stabilizing control and the noncondensable gas used for pressure stabilization control can weaken steam condensation heat transfer in the integrated steam-gas pressurizer. A condensation experimental system was established and the heat transfer characteristics of steam-nitrogen and steam-argon condensation under natural convection had been investigated. The pressure ranged from 0.516 to 5.10 MPa. The distributions of nitrogen and argon in the steam/gas mixture were obtained in the experiments, and the results showed that nitrogen and argon were evenly distributed in the steam under different pressure, respectively. The effects of heat transfer temperature difference had also been investigated and it is found that the total heat transfer coefficient difference had little influence on the total condensation heat transfer coefficient. However, the steam condensation heat transfer coefficient decreased with the increase of the degree of supercooling of the wall. The condensation heat transfer coefficient was reduced by approximately 0.11 kW/(m2·K) as the degree of supercooling of the wall changed from 14°C to 36°C. The condensation heat transfer coefficient also decreased with the mass/molar fraction of noncondensable gas increasing and a certain difference between the effect of the mass fraction of noncondensable gas and the effect of the molar fraction of noncondensable gas was discussed in this paper.

scholarly journals Improving the Heat Transfer Rate of Air Conditioning Condenser by Material Optimization

2021 ◽  
pp. 39-50
Author(s):  
A. A. Adegbola ◽  
O. A. Adeaga ◽  
A. O. Babalola ◽  
A. O. Oladejo ◽  
A. S. Alabi
Keyword(s):  
Heat Transfer ◽  
Thermal Analysis ◽  
Heat Flux ◽  
Flow Rate ◽  
Transfer Rate ◽  
Air Conditioning ◽  
Static Pressure ◽  
Cfd Analysis ◽  
Condenser Tube ◽  
Total Heat Transfer

Air conditioning systems have condensers that remove unwanted heat from the refrigerant and transfer the heat outdoors. The optimization of the global exploit of heat exchanging devices is still a burdensome task due to different design parameters involved. There is need for more and substantial research into bettering cooling channel materials so as to ensure elevated performance, better efficiency, greater accuracy, long lasting and low cost heat exchanging. The aim of this research work is to improve the heat transfer rate of air conditioning condenser by optimizing materials for different tube diameters. Simulations using thermal analysis and Computational Fluid Dynamic (CFD) analysis were carried out to determine the better material and fluid respectively. The analysis was done using Analysis System software. Different parameters were calculated from the results obtained and graphs are plotted between various parameters such as heat flux, static pressure, velocity, mass flow rate and total heat transfer. The materials used for CFD analysis are R12 and R22, and for thermal analysis are copper and aluminium. From the CFD analysis, the result shows that R22 has more static pressure, velocity, mass flow rate and total heat transfer than R12 at condenser tube diameter 6 mm. In thermal investigation, the heat flux is more for copper material at condenser tube diameter 6 mm. Copper offers maximum heat flux. Also, refrigerant R22 scores maximum for the heat transfer criteria, but cannot be recommended due to toxicity

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