scholarly journals Pressure drop in a single U-tube test section

1967 ◽  
Author(s):  
E.L. Geery ◽  
W.R. Thompson
Keyword(s):  
Pressure Drop ◽  
Test Section ◽  
Tube Test

scholarly journals Effect of Metal Foam Insert Configurations on Flow Boiling Heat Transfer and Pressure Drop in a Rectangular Channel

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4617
Author(s):  
Sanghyun Nam ◽  
Dae Yeon Kim ◽  
Youngwoo Kim ◽  
Kyung Chun Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Test Section ◽  
Boiling Heat Transfer ◽  
Metal Foam ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Saturation Pressure ◽  
Two Phase

Heat transfer under flow boiling is better in a rectangular channel filled with open-cell metal foam than in an empty channel, but the high pressure drop is a drawback of the empty channel method. In this study, various types of metal foam insert configurations were tested to reduce the pressure drop while maintaining high heat transfer. Specifically, we measured the boiling heat transfer and pressure drop of a two-phase vertical upward flow of R245fa inside a channel. To measure the pressure and temperature differences of the metal foam, differential pressure transducers and T-type thermocouples were used at both ends of the test section. While the saturation pressure was kept constant at 5.9 bar, the steam quality at the inlet of the test section was changed from 0.05 to 0.99. The channel height, moreover, was 3 mm, and the mass flux ranged from 133 to 300 kg/m2s. The two-phase flow characteristics were observed through a high-speed visualization experiment. Heat transfer tended to increase with the mean vapor quality, and, as expected, the fully filled metal foam channel offered the highest thermal performance. The streamwise insert pattern model had the lowest heat transfer at a low mass flux. However, at a higher mass flux, the three different insert models presented almost the same heat transfer coefficients. We found that the streamwise pattern model had a very low pressure drop compared to that of the spanwise pattern models. The goodness factors of the flow area and the core volume of the streamwise patterned model were higher than those of the full-filled metal foam channel.

Hydrodynamics of Pulse-Stabilized Fluidization at Incipient Fluidization

1999 ◽  
Author(s):  
Subhadeep Gan ◽  
Donald E. Beasley
Keyword(s):  
Pressure Drop ◽  
Secondary Flow ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Test Section ◽  
Video Recording ◽  
Small Displacement ◽  
Pulsation Frequency ◽  
Primary Flow ◽  
Oscillatory Component

Abstract A laboratory scale experimental facility which models a Pulsed Atmospheric Fluidized Bed Combustor (PAFBC) has been developed; this facility is designed to examine the effect of an opposing secondary flow having an oscillatory component on a bubbling fluidized bed. The secondary flow is oriented in a vertical direction. The secondary flow is introduced into the bubbling bed through a tailpipe that extends through the bed and ends just above the porous polyethylene distributor. A pulsed flow simulator that employs a small displacement of a relatively large piston with variable drive radius and speed provides the oscillatory component of the secondary flow. The fluidized bed test section has a cross-sectional flow area of 30.5 by 30.5 cm with a height of 53 cm. Heat exchanger surfaces are modeled by two symmetric horizontal cylinders housed in the test section. The following test parameters are controlled: the primary flow rate, the mean secondary flow rate, the pulsation frequency and the amplitude of the secondary flow. Pressure taps are located just above the distributor and in the freeboard region to measure overall bed pressure drop. The facility is operated with a range of particles from 345 μm to 715 μm and a range of superficial fluidization velocities corresponding to the bubble flow regime. Fluidization curves were generated for traditional fluidization, using the primary flow through the porous distributor, with both primary and a steady secondary flow, and with primary and a pulsed secondary flow. Significant departures from the linear Darcy flow curves in the fixed bed region were observed, and attributed to significant local fluidization. Time resolved measurements of the overall bed pressure drop clearly indicate phase-locking behavior of the overall bed pressure drop with imposed frequency. Bubbles formed in pulse-stabilized fluidization are significantly smaller than in traditional fluidization, as observed through video recording of the present bed.

Large Eddy Simulation of a Helical Coil Steam Generator Test Section

2017 ◽  
Author(s):  
Jonathan K. Lai ◽  
Elia Merzari ◽  
Marilyn Delgado ◽  
Samuel J. Lee ◽  
Saya Lee ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Large Eddy Simulation ◽  
Steam Generator ◽  
Test Section ◽  
Helical Coil ◽  
Reynolds Stresses ◽  
Eddy Simulation ◽  
High Heat Transfer ◽  
Large Eddy ◽  
Inlet Conditions

The helical coil steam generator (HCSG) is a compact heat exchanger that can have high heat transfer even when the pressure drop is low. This makes it advantageous in small modular reactors and high-temperature reactor designs. In order to investigate the fluid phenomena around these helical banked tubes, a test section was built at Texas A&M University to represent flow across two half-rods within HCSG. This study focuses on the validation of large eddy simulation (LES) for this particular geometry. Pressure tap and particle image velocimetry (PIV) measurements have been recorded at an inlet Reynolds number of 8643, and both mean and fluctuating data is compared with the numerical results. The highly scalable spectral-element code Nek5000 has been used to produce the LES calculations. First, simulations of varying polynomial order expansions are made to determine the spatial resolution required to capture the turbulent scales. Then, simulations with different inlet conditions are compared with experimental data. The pressure drop shows good agreement with pressure tap measurements while velocity shows similar characteristics with PIV. Furthermore, the components of the Reynolds stresses and modes from proper orthogonal decomposition have been developed to validate the physics captured.

Flow Pattern, Void Fraction and Pressure Drop During Adiabatic Two-Phase Gas-Liquid Flow in Vertical Micro-Channel

2012 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Void Fraction ◽  
Test Section ◽  
Annular Flow ◽  
Fused Silica ◽  
Working Fluid ◽  
Micro Channel ◽  
Two Phase ◽  
Churn Flow

The experimental investigation is performed to study two-phase flow pattern, void fraction and pressure drop characteristics in a vertical micro-channel. The test section is a fused silica tube with a diameter of 0.53 mm and a length of 320 mm. Air and water are used as working fluid which is introduced to the test section in vertical upward direction. The test runs are done at superficial velocities of gas and liquid ranging respectively from 0.375 to 21.187 m/s and 0.004 to 2.436 m/s. Stereozoom microscope mounted together with camera are employed to conduct flow visualization from which slug flow, throat-annular flow, churn flow, annular flow and annular-rivulet flow are observed. Based on image analysis, void fraction data are obtained and found to be linear relationship with volumetric quality. The frictional pressure drop is relatively high when the formation of churn flow is established. Besides, the two-phase frictional multiplier is found to be strongly dependent on both mass flux and flow pattern.

Experimental Investigation on the Condensation Heat Transfer and Pressure Drop Characteristics of R134A at High Mass Flux Conditions During Annular Flow Regime Inside a Vertical Smooth Tube

2009 ◽  
Author(s):  
Ahmet Selim Dalkilic ◽  
Suriyan Laohalertdecha ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Temperature Difference ◽  
Test Section ◽  
Annular Flow ◽  
Condensation Heat Transfer ◽  
Mass Fluxes ◽  
Condensation Heat Transfer Coefficient

This paper presents an experimental investigation on the co-current downward condensation of R134a inside a tube-in-tube heat exchanger. The test section is a 0.5 m long double tube with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The inner tube is constructed from smooth copper tubing of 9.52 mm outer diameter and 8.1 mm inner diameter. The condensing temperatures are between 40 and 50°C, heat fluxes are between 9.78 and 50.69 kW m−2. The temperature difference between the saturation temperature of refrigerant and inlet wall varies between 1.66–8.94°C. Condensation experiments are done at mass fluxes varying between 340 and 456 kg m−2s−1 while the average qualities are between 0.76–0.96. The quality of the refrigerant in the test section is calculated considering the temperature and pressure measured from the test section. The pressure drop across the test section is directly measured by a differential pressure transducer. The average experimental heat transfer coefficient of the refrigerant is calculated by applying an energy balance based on the energy transferred from the test section. Experimental data of annular flow are examined such as the alteration of condensation heat transfer coefficient with the vapor average quality and temperature difference respectively according to different mass fluxes and condensing temperatures. The relation between the heat flux and temperature difference, besides this, the relation between the condensation heat transfer coefficient and condensing pressure are shown comparatively and the effects of mass flux and condensation temperature on the pressure drop are also discussed. The efficiency of the condenser is considered comparing with various experimental data according to tested condensing temperatures and mass fluxes of refrigerant. Some well known correlations and models of heat transfer coefficient were compared to show that annular flow models were independent of tube orientation provided that annular flow regime exists along the tube length and capable of predicting condensation heat transfer coefficient in the test tube.

Pressure Drop During Condensation in Microchannels

2010 ◽  
Author(s):  
Tian Yi Song ◽  
Guang Xu Yu ◽  
Xue Hu Ma ◽  
John W. Rose ◽  
Hua Sheng Wang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Test Section ◽  
Research Programme ◽  
Local Heat ◽  
Vapor Flow ◽  
Final Test ◽  
Total Heat Transfer ◽  
Local Heat Flux ◽  
New Research

The paper reports preliminary results from a new research programme for making accurate heat transfer and pressure drop measurements during condensation in microchannels. While commissioning the apparatus a dummy test section was used with identical channel and header geometry to that to be used in the main test program (The final test section will comprise a relatively thick copper test section containing 98 accurately located thermocouples for measuring the temperature distribution from which local heat flux and temperature at the microchannel surface will be obtained). While using the dummy test section (without embedded thermocouples) the opportunity was taken to make accurate pressure drop measurements while measuring the vapor flow rate and total heat transfer rate based on coolant measurements. Data have been obtained for FC72 and steam. Approximate comparisons with available pressure drop calculation methods are presented.

Heat Transfer Performance of Supercritical Carbon Dioxide in Microchannels

2015 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Kun-Chieh Liao
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Pressure Drop ◽  
Critical Point ◽  
Test Section ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Test Results ◽  
Test Conditions ◽  
Critical Carbon Dioxide

This paper provides an experimental investigation of heat transfer performance and pressure drop of supercritical carbon dioxide cooling in microchannel heat exchanger. An extruded flat aluminum tube with 37 parallel channels and each channel of 0.5 mm × 0.5 mm cross section was used as the test section. Super critical carbon dioxide at pressure of 7.5 MPa and inlet temperature varied from 55 to 25 °C was tested. The temperature drops of CO2 cooled inside the test section was controlled at 2, 4 and 8 °C separately for each test to investigate the effect of properties change on the friction and heat transfer performance at various temperature cooling ranges near the critical point. The test results showed that while the test conditions were away from (approximately 5 °C higher or lower) the critical point, both heat transfer and pressure drop performance agreed very well with those predicted by convention correlations. However, while the test conditions near the critical point, the difference between the present test results and the prediction values is very high. From the experiment results of various temperature change range inside the test section, we can find that both heat transfer and pressure drop were strongly affected by the temperature cooling ranges near the critical point. Since there is a drastic peak of the properties change near the critical point, neither fluid properties at the average temperature nor the average properties at the inlet and exit temperatures may appropriately present the actual properties change in the test process. If we use the properties integrated but not averaged from inlet to the exit temperatures, we may obtain the results that agree well with the values predicted by conventional correlations. The heat transfer and pressure drop performance of super critical carbon dioxide are indeed similar to these at normal conditions if its properties were appropriately evaluated.

Experimental Investigation and Flow Visualization of the Two-Phase Flow Instability at Low Vapor Quality in a Vertical Narrow Channel

2018 ◽  
Author(s):  
Liqiang Pan ◽  
Yang Liu ◽  
Weihua Li ◽  
Yefei Liu
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Test Section ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Narrow Channel ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase

The two-phase flow instability of forced convection has been experimentally investigated in a vertical narrow channel with the hydraulic diameter of 2.857mm and aspect ratio of 20. Transparent, metallic and conductive films on external surfaces of the test section can provide visualization and uniform heating for deionized water. The heat flux is 6–18.2 kW · m−2. When the instability occurs at low vapor quality, a series of parameters are measured and visualized images are obtained by a high-speed camera. The results show that the large amplitude of pressure drop between the inlet and outlet in the test section is due to the elongated bubble, and the value of pressure drop is positively correlated with the volume of the bubble. The oscillation period of pressure drop decreases with the increase of heat flux, and the period can be determined by the method of the Fast Fourier Transform. The backflow phenomenon is analyzed, which has a greater effect on the oscillation of pressure drop than bubble nucleation, bubble growth, bubble coalescence and recoiling of bubble boundary.

Pressure Drop Study and Correlation Development for Two-Phase Flow of R134a in Annular Helicoidal Pipe

2004 ◽  
Author(s):  
H. L. Mo ◽  
R. Prattipati ◽  
C. X. Lin
Keyword(s):  
Experimental Data ◽  
Liquid Phase ◽  
Pressure Drop ◽  
Vapor Phase ◽  
Test Section ◽  
Circular Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Annular Section ◽  
Phase Pressure

Pressure drop characteristics of R134a in annular helicoidal pipe was investigated experimentally with R134a flowing in the annular section. The experimental results revealed that when more R134a vapor was condensed, the liquid phase pressure drop increased largely while the vapor phase pressure drop decreased slightly. By comparing with the experimental data obtained from the same test section with R134a flowing in the inner circular tube of the helicoidal pipe, it was observed that the pressure drop for refrigerant in the annular section was always larger. It was also observed that the helicoidal pipe orientation showed little effect on the pressure drop variations. A pressure drop correlation was developed from the experimental data in terms of pressure drop multiplier with respect to Lockhart-Martinelli parameter.

Optimization of the Relationship Between the Two-Phase Friction Factor and Reynolds Equivalent Number Model by Means of Genetic Algorithm

2011 ◽  
Author(s):  
Berna Bolat ◽  
Muhammet Balcilar ◽  
Ahmet Selim Dalkilic¸ ◽  
Somchai Wongwises
Keyword(s):  
Genetic Algorithm ◽  
Pressure Drop ◽  
Friction Factor ◽  
Test Section ◽  
Smooth Tube ◽  
Condensation Process ◽  
Significant Variable ◽  
Two Phase ◽  
Equivalent Number ◽  
The Relationship

The two-phase friction factor of R134a in a copper smooth tube having an inner diameter of 8.1 mm and length of 0.5 m during downward condensation is investigated experimentally and numerically. The test runs were performed at average condensing temperatures of 40–50 °C. The mass fluxes were around 260, 340 and 456 kg m−2s−1 and the heat fluxes were between 11.3 and 55.3 kW m−2. Accuracy of the dataset was proven in many papers in the literature. The quality of the refrigerant in the test section is calculated considering the temperature and pressure obtained from the experiment. The pressure drop across the test section is directly measured by a differential pressure transducer. The equivalent Reynolds number is considered to be the significant variable for the analysis. A Genetic Algorithm (GA), is one of the most successful methods among evolution algorithms, is applied for the optimization of the relationship between the two-phase friction factor and Reynolds equivalent number model in this study. The annular flow condensation process in the vertical test tube is expressed using GA method successfully. Regression analysis was done including the Reynolds equivalent number and other measured values such as pressure drop and mass flux of R134a, and gave a convincing correlation based on 182 smooth tube data points for practical applications. The most suitable coefficients of the proposed correlations are depicted to be compatible with the experiment by way of the algorithm.

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