Pressure Drop During Forced Convection Boiling of R-12 Under Swirl Flow

1982 ◽  
Vol 104 (4) ◽  
pp. 758-762 ◽  
Author(s):  
K. N. Agrawal ◽  
H. K. Varma ◽  
S. Lal
Keyword(s):  
Pressure Drop ◽  
Forced Convection ◽  
Flow Boiling ◽  
Horizontal Tube ◽  
Swirl Flow ◽  
Flow Data ◽  
Nelson Model ◽  
Twisted Tapes ◽  
Twist Ratio ◽  
Flow Pressure

This investigation deals with the pressure drop during forced convection boiling of R-12 under swirl flow inside a horizontal tube. Plain flow and swirl flow pressure drop data are reported for an electrically heated, horizontal, stainless steel, round test-section fitted with twisted tapes having twist ratios from 3.76 to 10.15. A correlation has been presented expressing the swirl flow boiling pressure drop in terms of the twist ratio and the plain flow boiling pressure drop calculated by the Martinelli-Nelson model. The proposed correlation predicts the swirl flow data to within ± 20 percent of the observed values.

scholarly journals EXPERIMENTAL STUDY ON IN-POND HEAT EXCHANGER PROVIDED WITH TWISTED TAPES

2017 ◽  
Vol 10 (13) ◽  
pp. 467
Author(s):  
Karunamurthy K ◽  
Nayan Singh ◽  
Vivek Singh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Saline Water ◽  
Salinity Gradient ◽  
Swirl Flow ◽  
Laboratory Model ◽  
Solar Ponds ◽  
Twisted Tapes ◽  
Twist Ratio

In-pond heat exchangers (IHE) are used in salinity gradient solar ponds (SGSP), to transfer heat from hot saline water of the lower convective zone to the heat transfer medium. The performance of the SGSP depends on the performance of the IHE, which in turn depends on the method of heat transfer augmentation. A laboratory model IHE was fabricated to augment the heat transfer using helical twisted tapes (HTTs). The effects of varying twist ratio and double TTs on pressure drop and heat transfer were studied in this experimental work. Conventional HTTs of three twist ratios (Y=7, 9, 11), twin TTs of co-swirl flow (CoTT), and counter-swirl TTs (CTT) with Y=7 were provided in the flow path of the heat exchanger tube for analysis. From the results, it is observed that TTs with less twist ratio yielded higher rate of heat transfer by sacrificing the pressure drop. Compared to single TT, double TT provided better thermal performance. The pressure drop and rate of heat transfer for CTT are more compared to all other cases, including double TT with co-swirl flow.

Subcooled Swirl-Flow Boiling and Burnout With Electrically Heated Twisted Tapes and Zero Wall Flux

1965 ◽  
Vol 87 (3) ◽  
pp. 342-348 ◽  
Author(s):  
W. R. Gambill
Keyword(s):  
Tube Wall ◽  
Flow Boiling ◽  
Heated Surface ◽  
Swirl Flow ◽  
Heat Fluxes ◽  
Twisted Tape ◽  
Centripetal Acceleration ◽  
Head Tank ◽  
Twisted Tapes ◽  
Twist Ratio

A series of swirl-flow tests was conducted in which all of the heat was generated in twisted-tape swirl generators. This is in contrast to past ORNL swirl-flow tests with twisted tapes, in which ∼99 percent of the heat was generated in the metallic tube wall. In the present study, water from a constant-head tank flowed by gravity at 5 to 8 fps through a vertical 0.27-in.-ID glass tube ∼13 in. long, in which was located a resistance-heated, 16-mil-thick A-nickel tape. Tape-twist ratios were varied from 2.7 to ∞ inside tube diameters/180-deg twist, inlet water temperatures from 63 to 173 F, and heat fluxes from 0.21 × 106 to 1.20 × 106 Btu/hr·ft2. The water head above the top of the tube was held at 30.7 in. In all cases, the critical wall superheat increased with decrease of tape-twist ratio, whereas the critical heat fluxes for the twisted tapes fell between 93 percent and 122 percent of those for flat tapes, maximizing in all cases at a tape-twist ratio of 7 to 10. It is postulated that the deleterious effect of centripetal acceleration with this geometry, which tends to hold the vapor on the heated surface, is compensated in the swirl-flow entrance region by inertial impingement of the liquid onto the tape surface, and along the remainder of the length by a double-vortex secondary flow pattern in the plane normal to the tube wall. The power density of a swirl-flow tube assembly may therefore be significantly increased by generating heat in the twisted tape as well as in the tube wall.

INVESTIGATION ON VOID FRACTION FOR TWO-PHASE FLOW PRESSURE DROP OF EVAPORATIVE R-290 IN HORIZONTAL TUBE

2016 ◽  
Vol 78 (8-4) ◽  
Author(s):  
Agus Sunjarianto Pamitran ◽  
Sentot Novianto ◽  
Normah Mohd-Ghazali ◽  
Nasruddin Nasruddin ◽  
Raldi Koestoer
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Homogeneous Model ◽  
Saturation Temperature ◽  
Horizontal Tube ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions

Two-phase flow boiling pressure drop experiment was conducted to observe its characteristics and to develop a new correlation of void fraction based on the separated model. Investigation is completed on the natural refrigerant R-290 (propane) in a horizontal circular tube with a 7.6 mm inner diameter under experimental conditions of 3.7 to 9.6 °C saturation temperature, 10 to 25 kW/m2 heat flux, and 185 to 445 kg/m2s mass flux. The present experimental data was used to obtain the calculated void fraction which then was compared to the predicted void fraction with 31 existing correlations. A new void fraction correlation for predicting two-phase flow boiling pressure drop, as a function of Reynolds numbers, was proposed. The measured pressure drop was compared to the predicted pressure drop with some existing pressure drop models that use the newly developed void fraction model. The homogeneous model of void fraction showed the best prediction with 2% deviation

Transient Critical Heat Fluxes of Subcooled Water Flow Boiling in SUS304-Circular Tubes With Various Twisted-Tape Inserts (Influence of Twist Ratio)

2014 ◽  
Vol 6 (3) ◽  
Author(s):  
Koichi Hata ◽  
Katsuya Fukuda ◽  
Suguru Masuzaki
Keyword(s):  
Circular Tube ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Effective Length ◽  
Twisted Tape ◽  
Subcooled Flow Boiling ◽  
Circular Tubes ◽  
Twisted Tapes ◽  
Subcooled Flow ◽  
Twist Ratio

The transient critical heat fluxes (transient CHFs) in SUS304-circular tubes with various twisted-tape inserts are systematically measured for mass velocities (G = 3988–13,620 kg/m2s), inlet liquid temperatures (Tin = 287.55–313.14 K), outlet pressures (Pout = 805.11–870.23 kPa) and exponentially increasing heat inputs (Q = Q0 exp(t/τ), exponential periods, τ, of 28.39 ms to 8.43 s) by the experimental water loop comprised of a multistage canned-type circulation pump controlled by an inverter. The SUS304-circular tube of inner diameter (d = 6 mm), heated length (L = 59.4 mm), effective length (Leff = 49.4 mm), L/d (=9.9), Leff/d (=8.23), and wall thickness (δ = 0.5 mm) with average surface roughness (Ra = 3.89 μm) is used in this work. The SUS304 twisted-tapes with twist ratios, y [H/d = (pitch of 180 deg rotation)/d], of 2.40 and 4.45 are used. The transient critical heat fluxes for SUS304-circular tubes with the twisted-tapes of y = 2.40 and 4.45 are compared with authors' transient CHF data for the empty SUS304-circular tube and a SUS304-circular tube with the twisted-tape of y = 3.37, and the values calculated by authors' transient CHF correlations for the empty circular tube and the circular tube with twisted-tape insert. The influences of heating rate, twist ratio and swirl velocity on the transient CHF are investigated into details and the widely and precisely predictable correlations of the transient CHF against inlet and outlet subcoolings for the circular tubes with various twisted-tape inserts are given based on the experimental data. The correlations can describe the transient CHFs for SUS304-circular tubes with various twisted-tapes of twist ratios (y = 2.40, 3.37, and 4.45) in the wide experimental ranges of exponential periods (τ = 28.39 ms to 8.43 s) and swirl velocities (usw = 5.04–20.72 m/s) obtained in this work within −26.19% to 14.03% difference. The mechanism of the subcooled flow boiling critical heat flux in a circular tube with twisted-tape insert is discussed.

Flow boiling heat transfer and pressure drop characteristics of Isobutane in horizontal channels with twisted tapes

2020 ◽  
Vol 162 ◽  
pp. 120345
Author(s):  
Alireza Sarmadian ◽  
Hadi Ahmadi Moghaddam ◽  
Amirmasoud Asnaashari ◽  
Hossein Ahmadi Nejad Joushani ◽  
Mostafa Moosavi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Twisted Tapes ◽  
Flow Boiling Heat Transfer

scholarly journals Study Pressure Drop for Two-Phase Flow in a Large Diameter Tube

2019 ◽  
Vol 17 (72) ◽  
pp. 101-109
Author(s):  
Muhsen Koli Nahi
Keyword(s):  
Pressure Drop ◽  
Two Phase Flow ◽  
Homogeneous Model ◽  
Large Diameter ◽  
Horizontal Tube ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Pressure

The aim of this study is to discover the deviation of two phase flow correlations. A comparsion was made between the expermital values of two-phase flow pressure drops data were obtained experimentally by Al-Jumaily (1999) by using air-water mixture in a horizontal tube of (132 mm) nominal diameter and a test section of (32 m) long at pressure and temperature close to atmospheric and those predicted by three correlations well-used in the literature, which show that the homogeneous model was the best

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