Forced convective heat transfer to turbulent CO2 in the supercritical region
01 Aug 1970-International Journal of Heat and Mass Transfer (Pergamon)-Vol. 13, Iss: 8, pp 1339-1348
TL;DR: In this article, the wall temperatures of a 4·56 m long, 2·28 × 10−2 m dia. tube with heat transfer to turbulent flow of CO2 at supercritical pressure were measured.
About: This article is published in International Journal of Heat and Mass Transfer.The article was published on 1970-08-01. It has received 77 citations till now. The article focuses on the topics: Supercritical flow & Convective heat transfer.
Citations
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TL;DR: In this article, a comprehensive set of data was obtained for pressures from 226 to 294 bar, bulk temperatures from 230 to 540°C, heat fluxes from 116 to 930 kW/m 2 and mass velocities from 310 to 1830 kg/m2s.
570 citations
TL;DR: In this paper, the authors provide an up-to-date review of mixed convection heat transfer in vertical tubes, divided into two sections, the first dealing with laminar flow, and the second with turbulent flow.
421 citations
TL;DR: In this paper, the authors investigated the effects of strong non-uniformity of fluid properties whilst avoiding other complications associated with the temperature dependence of density, which can lead to important effects on the mean flow and turbulence fields and heat transfer effectiveness.
298 citations
TL;DR: In this article, the authors investigated the heat transfer and pressure drop characteristics of the Printed Circuit Heat Exchanger (PCHE) in an experimental supercritical CO2 loop.
Abstract: Heat transfer and pressure drop characteristics of the Printed Circuit Heat Exchanger (PCHE) were investigated in an experimental supercritical CO2 loop. The inlet temperature and pressure were varied from 280 to 300 °C/2.2 to 3.2 MPa in the hot side and from 90 to 108 °C/6.5 to 10.5 MPa in the cold side while the mass flow rate was varied from 40 to 80 kg h−1. The overall heat transfer coefficient range is 300–650 W m−2 K−1 while the compactness with respect to the heat exchanger core is approximately 1050 m2 m−3. The empirical correlations to predict the local heat transfer coefficient and pressure drop factor as a function of the Reynolds number have been proposed for the tested PCHE.
236 citations
TL;DR: In this article, the authors investigated the effect of turbulence on heat transfer to CO2 at supercritical pressure flowing in heated vertical tubes using direct numerical simulation at the inlet Reynolds number Re0=5400, which is based on inlet bulk velocity and tube diameter.
Abstract: Turbulent heat transfer to CO2 at supercritical pressure flowing in heated vertical tubes is investigated using direct numerical simulation at the inlet Reynolds number Re0=5400, which is based on inlet bulk velocity and tube diameter. Temperature range within the flow field covers the pseudocritical region, where very significant fluid property variations are involved. Both upward and downward flows are considered. The wall temperature distribution shows well-known heat transfer deterioration characterized by the localized peak in upward flows, while no such anomaly is observed in downward flows. The deterioration occurs at the region where turbulence is attenuated significantly, and is followed by the enhancement with restoration of turbulence caused by complicated interactions with a buoyancy effect. Further investigation of turbulence statistics indicates that ρux″ux″¯, ρux″ur″¯, and ρux″h″¯ are significantly affected by their respective buoyancy production terms due to ρ′ux′¯, ρ′ur′¯, and ρ′h′¯ which...
225 citations
References
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TL;DR: In this article, a simplified procedure was proposed for estimating heat transfer coefficients in the critical region by using a semitheoretical equation developed for zero heat flow, which was applied to the realt case of finite heat transfer.
Abstract: Heat transfer coefficients were measured experimentally for carbon dioxide in turbulent flow in an 0.18-in. I.D. pipe. The pressure was 1,200 lb./sq. in. abs. and the bulk temperature varied from 70° to 120°F. In this critical region the coefficients between fluid and tube wall ranged from 300 to 2,600 B.t.u./(hr.)(sq. ft./°F.) over a Reynolds number interval of 30,000 to 300,000.
Existing empirical and semitheoretical correlations were found inadequate in this region, where the thermal conductivity, viscosity, density, and specific heat are all varying rapidly and nonuniformly with temperature. A method of integrating the heat and momentum transfer equations with variable physical properties, recently proposed by Deissler, was applied to the experimental data and found to fit well. The application required extensive calculations, which were carried out with an Electrodata digital computer.
A simplified procedure was proposed for estimating heat transfer coefficients in the critical region by using a semitheoretical equation developed for zero heat flow. Simple rules were suggested for estimating the temperature at which to evaluate the physical properties when this equation is applied to the realt case of finite heat transfer. The method worked well when compared with the computed heat transfer coefficients of Deissler for supercritical wate but showed about 30% deviation when compared with the carbon dioxide results. This discrepancy is believed due to the fact that the carbon dioxide was very close to the critical point (reduced pressure = 1.1) but the water was somewhat further removed (reduced pressure = 1.6).
106 citations
"Forced convective heat transfer to ..." refers methods in this paper
...The only exceptions are the measurements over a limited part of the near critical region, of mean velocity and temperature profiles through COz flow in a tube by Wood and Smith [7] and the Schlieren pictures of CO2 flow over a heated flat plate by Sabersky and Hauptmann [8]....
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TL;DR: In this paper, the authors measured the temperature and velocity profiles and local heat transfer coefficients for turbulent flow of carbon dioxide in a tube at 1,075 lb/sq. in. abs.
Abstract: Unusual heat transfer phenomena have been observed between solid surfaces and fluids near their thermodynamic critical point. To understand better these phenomena temperature and velocity profiles and local heat transfer coefficients were measured for turbulent flow of carbon dioxide in a tube at 1,075 lb/sq. in. abs. (pc = 1,071). The results indicate a severe flattening of the radial temperature profiles, a maximum in the velocity profile between the wall and the tube axis, and a maximum in h' when the bulk fluid temperature passes through the transposed critical temperature.
The results can be explained qualitatively by considering the variation with temperature of thermal conductivity near the tube wall and specific heat in the turbulent core.
57 citations
TL;DR: In this article, the use of liquefied gas as a supercoding fluid has been investigated in the context of forced convection in a region of the world with high oxygen consumption.
Abstract: H e a t t r ans fe r by forced convect ion in t h e region of t h e c r i t i ca l t e m p e r a t u r e h a s been s tud i ed expe r imen ta l ly , u s i n g oxygen a t superc r i t i ca l a n d a t subcr i t i ca l p ressures . Near t h e cr i t ica l t e m p e r a t u r e t h e r e exists a m i n i m u m in t h e h e a t t r ans fe r coefficient wh ich is apprec iab ly lower t h a n t h e value a t lower or a t h i g h e r t e m p e r a t u r e s . T h i s p h e n o m e n o n will l i m i t t h e use of t h i s liquefied gas as a h e a t t ransfer fluid.
33 citations
01 Sep 1967
TL;DR: In this article, experimental data from studies of turbulent heat transfer at high fluxes to water flowing in vertical tubes at supercritical pressures were presented, and a comparison of data for upward and downward flows indicated an effect of natural convection.
Abstract: Experimental data are presented from studies of turbulent heat transfer at high fluxes to water flowing in vertical tubes at supercritical pressures. A comparison of data for upward and downward flows indicates an effect of natural convection.
30 citations
TL;DR: In this paper, experiments were described on the transfer of heat from a heated tube to a gas flowing through it, where three gases were used: air, helium and carbon dioxide.
Abstract: In this paper, experiments are described on the transfer of heat from a heated tube to a gas flowing through it. Three gases were used: air, helium and carbon dioxide. The difference in temperature between the tube and the gases was large and the main objective of the work was to study the effects of radial variations of the gas properties with temperature. The conditions under which the experiments were performed were (1) essentially fully developed velocity and temperature profiles, (2) approximately uniform wall heat flux and (3) low subsonic turbulent flow.Some analysis has been developed to cover the present experimental work. Predicted Nusselt number-Reynolds number relations for the constant properties case are found to be in reasonable agreement with the experimental data for Reynolds numbers above about 10 000, provided the ratio of eddy diffusivities is assumed to vary from about 1·0 at Re = 104 to about 1·2 at Re = 105. The effects of variations of surface/gas temperature ratio, predicted by th...
21 citations