Transient Convective Heat Transfer in a Helical Tube With Steam-Water Two-Phase Flow Under Pressure Drop Type Oscillations

2000 ◽  
Author(s):  
Lie-Jin Guo ◽  
Zi-Ping Feng
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Two Phase Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Range ◽  
Helical Tube

Abstract In the present paper the experiments for subcooled water flow and steam-water two-phase flow were conducted to investigate the effects of pulsation upon transient heat transfer characteristics in a closed-circulation helical-coiled tube steam generator. The non-uniform property of local heat transfer with steady flow was also examined. The secondary flow mechanism and the effect of interaction between the flow oscillation and secondary flow were analyzed on the basis of the experimental data. Some new phenomena were observed and explained. A series of correlations were proposed for the average and local heat transfer coefficients both under steady and oscillatory flow conditions. The results showed that there were considerable variations in local and peripherally time-averaged Nusselt numbers for pulsating flow in a wide range of parameters. Systematic investigations of pressure drop type oscillations and their thresholds for steam-water two-phase flow in a uniformly heated helical tube were also reported.

scholarly journals ENHANCEMENT THE HEAT TRANSFER FOR TWO-PHASE FLOW THROUGH A RECTANGULAR RIBBED VERTICAL CHANNEL

2018 ◽  
Vol 18 (1) ◽  
pp. 92-109
Author(s):  
Riyadh S Al-Turaihi ◽  
Doaa F Kareem
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Vertical Channel ◽  
Numerical Data ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Two Phase

 The heat transfer coefficient and temperature distribution of two phase flow (water, air)in rectangular ribbed vertical channel was investigated experimentally and numerically inthis work for different values of water and air superficial velocities (0.0421, 0.0842, 0.1158,0.1474 and 0.1684 m/s) and (1.0964, 1.425, 1.644, 1.864 and 2.193 m/s), respectively, atconstant heat flux (120 W). The distribution of temperature along the channel wasphotographed using thermal camera and compared with images for the correspondingcontours which found numerically. The experimental results of heat transfer coefficientcompared with computational fluid dynamics model simulated by Ansys fluent 15.0. Agood agreement has been found between the experimental and numerical data, where thepercentage deviation between the experimental and the numerical results is (1% - 6% ). Theresults showed that, the local heat transfer coefficient increased by adding ribs, it alsoincreased as the velocity of the flow increased.

ENHANCEMENT THE HEAT TRANSFER FOR TWO-PHASE FLOW THROUGH A RECTANGULAR RIBBED VERTICAL CHANNEL

2018 ◽  
Vol 18 (1) ◽  
pp. 92-109
Author(s):  
Riyadh S Al-Turaihi ◽  
Doaa F Kareem
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Two Phase Flow ◽  
Vertical Channel ◽  
Numerical Data ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Two Phase

The heat transfer coefficient and temperature distribution of two phase flow (water, air)in rectangular ribbed vertical channel was investigated experimentally and numerically inthis work for different values of water and air superficial velocities (0.0421, 0.0842, 0.1158,0.1474 and 0.1684 m/s) and (1.0964, 1.425, 1.644, 1.864 and 2.193 m/s), respectively, atconstant heat flux (120 W). The distribution of temperature along the channel wasphotographed using thermal camera and compared with images for the correspondingcontours which found numerically. The experimental results of heat transfer coefficientcompared with computational fluid dynamics model simulated by Ansys fluent 15.0. Agood agreement has been found between the experimental and numerical data, where thepercentage deviation between the experimental and the numerical results is (1% - 6% ). Theresults showed that, the local heat transfer coefficient increased by adding ribs, it alsoincreased as the velocity of the flow increased.

Two-Phase Flow Experimental Study: Influence of Gravity Level on Local Boiling Heat Transfer Inside a Minichannel

2009 ◽  
Author(s):  
Se´bastien Luciani ◽  
David Brutin ◽  
Christophe Le Niliot ◽  
Loune`s Tadrist
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Two Phase Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Gravity Level ◽  
Two Phase ◽  
Mass Transfers

Flow boiling in minichannels is the most complex convective phase change process. Indeed, there are a lot of physical parameters that influence the two-phase flow during boiling. Here, we will focus on the influence of one of this factor: the gravity level. Actually, there are not many mechanisms that have been proposed for the role of this bound on boiling phenomena. In fact, there is not complete agreement on the importance of gravity on heat and mass transfers with phase change because there is a lack of experimental data at this small scale and because reproducing different gravity levels during parabolic flights has a cost. In this line, the goal of this work is to obtain benchmark data on the local heat transfer coefficient in a minichannel during hyper and microgravity. We want to acquire a better knowledge of the elementary phenomena which control the heat and mass transfers during convective boiling. Indeed, boiling in microscale geometry is a very efficient mode of heat transfer since high heat and mass transfer coefficients are achieved. Actually, minichannels and microchannels are widely used in industry and they are already attractive in many domains such as design of compact evaporators and heat exchangers. They provide an effective method of fluid movement and they have large heat dissipation capabilities. In these situations, their compact size and heat transfer abilities are unrivalled. In this communication, the objective is to acquire better knowledge of the conditions that influence the two-phase flow under microgravity. The expected results will contribute to the development of microgravity models. To perform these investigations, we used an experimental data coupling with an inverse method based on BEM (Boundary Element Method). This non intrusive approach allows us to solve a 3D multi domain IHCP (Inverse Heat Conduction Problem). With this analysis, we are able to quantify the local heat flux, the local temperature and the local heat transfer coefficient in a minichannel (254 μm) by inversing thermocouples data without disturbing the established flow.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

Effects of Rib Arrangements on Pressure Drop and Heat Transfer in a Rib-Roughened Channel With a Sharp 180 deg Turn

1997 ◽  
Vol 119 (3) ◽  
pp. 610-616 ◽  
Author(s):  
S. Mochizuki ◽  
A. Murata ◽  
M. Fukunaga
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Secondary Flow ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Diameter Ratio ◽  
Equivalent Diameter ◽  
Before And After ◽  
Rib Roughened

The objective of this study was to investigate, through experiments, the combined effects of a sharp 180 deg turn and rib patterns on the pressure drop performance and distributions of the local heat transfer coefficient in an entire two-pass rib-roughened channel with a 180 deg turn. The rib pitch-to-equivalent diameter ratio P/de was 1.0, the rib-height-to-equivalent diameter ratio e/de was 0.09, and the rib angle relative to the main flow direction was varied from 30 ∼ 90 deg with an interval of 15 deg. Experiments were conducted for Reynolds numbers in the range 4000 ∼ 30,000. It was disclosed that, due to the interactions between the bend-induced secondary flow and the rib-induced secondary flow, the combination of rib patterns in the channel before and after the turn causes considerable differences in the pressure drop and heat transfer performance of the entire channel.

Numerical Research on Heat Transfer Characteristics Analysis of Two Particles in Supercritical Water

2021 ◽  
Author(s):  
Xiaoyu Li ◽  
Zhenqun Wu ◽  
Huibo Wang ◽  
Hui Jin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Phase Flow ◽  
Heat Transfer Characteristics ◽  
Particle Cluster ◽  
Two Phase ◽  
Transfer Characteristics

Abstract In the supercritical water (SCW)-particle two-phase flow of fluidized bed, the particles that make up the particle cluster interact with each other through fluid, and it will affect the flow and heat transfer. However, due to the complex properties of SCW, the research on particle cluster is lacking, especially in terms of heat transfer. This research takes two particles as an example to study the heat transfer characteristics between SCW and another particle when one particle exists. This research uses the distance and angle between the two particles as the influencing factors to study the average heat transfer rate and local heat transfer rate. In this research, it is found that the effect is obvious when L/D = 1.1. When L = 1.1D, the temperature field and the flow field will partially overlap. The overlap of the temperature field will weaken the heat transfer between SCW and the particle. The overlap of the flow field has an enhanced effect on the heat transfer between SCW and the particle. The heat transfer between SCW and particles is simultaneously affected by these two effects, especially local heat transfer rate. In addition, this research also found that as the SCW temperature decreases, the thermal conductivity and specific heat of SCW increases, which enhances the heat transfer between SCW and the particles. This research is of great significance for studying the heat transfer characteristics of SCW-particle two-phase flow in fluidized bed.

Sign in / Sign up

Export Citation Format

Share Document