scholarly journals Frictional resistance of supercritical pressure RP-3 flowing in a vertically downward tube at constant heat fluxes

2022 ◽  
Author(s):  
Yinlong Liu ◽  
Guoqiang Xu ◽  
Yanchen Fu ◽  
Jie Wen ◽  
Geng Gong ◽  
...  
Keyword(s):  
Frictional Resistance ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Constant Heat

Predicting charring rate of woods exposed to time-increasing and constant heat fluxes

2008 ◽  
Vol 81 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Yang Lizhong ◽  
Zhou Yupeng ◽  
Wang Yafei ◽  
Guo Zaifu
Keyword(s):  
Heat Fluxes ◽  
Constant Heat ◽  
Charring Rate

scholarly journals Deterioration in Heat Transfer to Fluids at Supercritical Pressure and High Heat Fluxes

1969 ◽  
Vol 91 (1) ◽  
pp. 27-36 ◽  
Author(s):  
B. S. Shiralkar ◽  
Peter Griffith
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
High Heat ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Bulk Temperature ◽  
Operating Pressure ◽  
The Heat Transfer Coefficient

At slightly supercritical pressure and in the neighborhood of the pseudocritical temperature (which corresponds to the peak in the specific heat at the operating pressure), the heat transfer coefficient between fluid and tube wall is strongly dependent on the heat flux. For large heat fluxes, a marked deterioration takes place in the heat transfer coefficient in the region where the bulk temperature is below the pseudocritical temperature and the wall temperature above the pseudocritical temperature. Equations have been developed to predict the deterioration in heat transfer at high heat fluxes and the results compared with previously available results for steam. Experiments have been performed with carbon dioxide for additional comparison. Limits of safe operation for a supercritical pressure heat exchanger in terms of the allowable heat flux for a particular flow rate have been determined theoretically and experimentally.

Pseudoboiling Heat Transfer to Supercritical Pressure Water in Smooth and Ribbed Tubes

1970 ◽  
Vol 92 (3) ◽  
pp. 490-497 ◽  
Author(s):  
J. W. Ackerman
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heated Surface ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Film Boiling ◽  
Fluid Temperature ◽  
Bulk Fluid ◽  
Pressure Water ◽  
Supercritical Pressure Water

Investigations of heat transfer to supercritical pressure fluids have been going on for some time, and correlations have been developed for both free and forced-convection conditions. In these investigations, unpredictable heat transfer performance has sometimes been observed when the pseudocritical temperature of the fluid is between the temperature of the bulk fluid and that of the heated surface. The unusual performance has been attributed to many causes, but one for which more evidence is being collected is that of a pseudofilm-boiling process similar to film boiling which occurs at subcritical pressures. This paper, which is an extension of work reported earlier on forced-convection heat transfer to supercritical pressure water, presents experimental evidence which suggests that a pseudofilm-boiling phenomenon can occur in smooth-bore tubes. During the period from 1963–1966, tubes with ID’s from 0.37 to 0.96 in. were tested at pressures from 3300–6000 psia and at heat fluxes and mass velocities in the range of interest in steam-generator design. The effects of heat flux, mass velocity, tube diameter, pressure, and bulk fluid temperature on both the occurrence and characteristics of pseudofilm boiling are discussed. Results of a second series of tests conducted in 1967, which show that ribbed tubes suppress pseudofilm boiling at supercritical pressure much like they do film boiling at subcritical pressures, are also discussed.

Variations of Buoyancy-Induced Mass Flux From Single-Phase to Two-Phase Flow in a Vertical Porous Tube With Constant Heat Flux

1999 ◽  
Vol 121 (3) ◽  
pp. 646-652 ◽  
Author(s):  
T. S. Zhao ◽  
Q. Liao ◽  
P. Cheng
Keyword(s):  
Heat Flux ◽  
Mass Flux ◽  
Single Phase ◽  
Two Phase Flow ◽  
Constant Heat Flux ◽  
Heat Fluxes ◽  
Phase Flow ◽  
Constant Heat ◽  
Two Phase ◽  
Porous Tube

This paper presents an experimental study of a buoyancy-induced flow of water with phase-change heat transfer in a vertical porous tube heated at a constant heat flux. Experiments were carried out from subcooled liquid flow to connective boiling by varying the imposed heat fluxes. At a prescribed heat flux the steady-state mass flux of water, as well as the temperatures along the tube wall and along the centerline of the packed tube, were measured. It is shown that for both single-phase flow and the two-phase flow with a rather low vapor fraction, the induced mass flux increased as the heat flux was increased. However, as the imposed heat flux was increased further, the induced mass flux dropped drastically, and remained relatively constant afterwards. The influences of various parameters such as the porous tube diameter, the particle sizes, and the hydrostatic head on the induced mass flux are also examined.

Vibration Effects on Surface Coke Deposition of Hydrocarbon Fuel at Supercritical Pressure Condition in Micro-Tubes

2013 ◽  
Author(s):  
Yanchen Fu ◽  
Zhi Tao ◽  
Guoqiang Xu ◽  
Hongwu Deng
Keyword(s):  
Heat Transfer ◽  
Flow Resistance ◽  
Stable Condition ◽  
Hydrocarbon Fuel ◽  
Constant Heat Flux ◽  
Supercritical Pressure ◽  
Coke Deposition ◽  
Wave Crest ◽  
Vibration Energy ◽  
Constant Heat

Experiments are performed to study vibration effects on surface coke deposition of aviation hydrocarbon RP-3 under supercritical pressure. The flowing RP-3 kerosene is stressed to 5MPa, and heated up from 127°C to 450°C in a stainless tube (1.8mm I.D., 2.2mm O.D., 1Cr18Ni9Ti) with a constant heat flux, and the mass flow rate is 3g/s. The working fluids flow downward through an 1800mm long tube. The vibration frequency is set from 100Hz to 600Hz, covering the main frequencies of the combustion chamber vibration when it works. Compared with stable condition, vibration effects have a distinct impact on the flow resistance and heat transfer. The amount of coke deposition reduced under all different frequencies with the maximize decline of 40.46%. Moreover, restraining efficiency is proportional to the vibration energy. Besides, vibration enhanced the heat transfer, the coefficient of which comes to a wave crest at the zone of second-order modes of response to the peak area with the biggest vibration energy.

Heat Flow Transducer Responses to Hyperbaric Environments

1980 ◽  
Vol 102 (3) ◽  
pp. 247-252 ◽  
Author(s):  
M. L. Nuckols
Keyword(s):  
Heat Flow ◽  
Ambient Pressure ◽  
Heat Fluxes ◽  
Constant Heat ◽  
Flow Transducer ◽  
Ambient Temperatures ◽  
Temperature And Pressure ◽  
Environmental Temperatures ◽  
Body Heat ◽  
Hyperbaric Conditions

The responses of heat flow transducers, used in the evaluation of convective body heat losses, have been investigated at hyperbaric environments. Environmental temperatures, pressures, and gas composition were varied while transducer responses to constant heat fluxes were observed. Ambient temperatures were varied between 3° and 40° C. Ambient pressures were varied between simulated depths of 0 and 1000 feet of seawater (445 psi). Transducer responses to heat fluxes varying between 0 and 250 watts/m2 are reported in the above temperature and pressure ranges within atmospheres of helium, nitrogen, and air. Ambient pressure variations were found to have little effect on the response of the heat flow transudcers to a constant heat source once appropriate temperature corrections were made. However, transducer response variations of up to 14 percent were observed when environmental gas compositions were varied at hyperbaric conditions.

Experimental Investigation of Convective Heat Transfer of Supercritical Pressure Hydrocarbon Fuel in a Horizontal Section of a Rotating U-Duct

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Zelong Lu ◽  
Yinhai Zhu ◽  
Yuxuan Guo ◽  
Peixue Jiang
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rotational Speed ◽  
Convective Heat Transfer Coefficient ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Secondary Flows ◽  
Horizontal Section ◽  
Static Conditions

Abstract The experimental and numerical investigations of the heat transfer of supercritical pressure n-decane flowing through a pipe at various rotational speeds, mass flow rates, heat fluxes, and pressures, are presented. This pipe is 2 mm in diameter, 200 mm in length, with a radius of 0.328 m, and is parallel to the rotating axis. The wall temperature was measured at four positions around the periphery of the pipe at each of the five selected cross section along the pipe's length. Maximum convective heat transfer was observed at the outer edge of the horizontal section, while its corresponding minimum was observed at the inner edge. The heat transfers at the two sides of the channel were observed to be similar. The density and pressure differences between the outer and inner edges increased at increasing rotating speeds. However, the temperature difference between the outer and inner edges decreased with increased rotational speed mainly because of the increase of secondary flows in the section. The section's average convective heat transfer coefficient increased with an increase in the rotational speed, and its value at 1000 rpm was approximately twice than that at static conditions. The phenomenon of oscillation was observed near the exit of the horizontal section, and was caused by the flow and considerable property changes near the pseudo critical temperature. A computational fluid dynamics (CFD) model was developed using the real gas thermal properties and was coupled with the heat transferred owing to fuel flow. The predicted fuel and wall temperatures were in good agreement with the experimental data. A new local Nusselt number correlation of the heat transfer of n-decane in a rotating horizontal section was proposed.

Experimental Study of the Influence of Surface Coke Deposition on Heat Transfer of Aviation Kerosene RP-3 at Supercritical Pressure

2012 ◽  
Author(s):  
Z. X. Jia ◽  
G. Q. Xu ◽  
J. Wen ◽  
H. W. Deng
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Flux ◽  
Flow Resistance ◽  
Constant Heat Flux ◽  
Supercritical Pressure ◽  
Coke Deposition ◽  
Transfer Enhancement ◽  
Constant Heat ◽  
Effect Of Surface

Experiments are performed to study the effect of surface coke deposition on heat transfer of aviation hydrocarbon RP-3 under supercritical pressure. The flowing RP-3 kerosene is stressed to 5MPa, and heated up to 130°C to 450°C in a stainless tube (1.8mm I.D., 2.2mm O.D., 1Cr18Ni9Ti) with a constant heat flux, and the mass flow rate is 3g/s. The working fluids flowed downwards through an 1800mm long tube. The experimental results indicated that insoluble products deposited onto metal surface have a significant impact on flow resistance and heat transfer the effect of coke deposition on heat transfer coefficient can be divided into four regimes: a) onset heat transfer enhancement zone; b) transition zone; c) heat transfer impairment zone; d) heat transfer stabilizing zone.

The Effect of Swirl, Inlet Conditions, Flow Direction, and Tube Diameter on the Heat Transfer to Fluids at Supercritical Pressure

1970 ◽  
Vol 92 (3) ◽  
pp. 465-471 ◽  
Author(s):  
B. Shiralkar ◽  
P. Griffith
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Supercritical Pressure ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Tube Diameter ◽  
Inlet Temperature ◽  
The Heat Transfer Coefficient

An investigation has been made of the factors governing the heat transfer coefficient to supercritical pressure fluids, particularly at high heat fluxes. The deterioration in heat transfer to supercritical carbon dioxide has been experimentally studied with reference to the operating conditions of mass velocity and heat flux, tube diameter, orientation, tape induced swirl, inlet temperature, and pressure. A detailed comparison has been made with the apparently contradictory results of other investigators, and operating regions, in which the heat transfer coefficient behaves differently, have been defined. The terms used to describe these regions are the Reynolds number, a heat-flux parameter, and a free-convection parameter.

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