Direct-contact heat exchange between fluidizing particles and a heat transfer surface in a fluidized bed: Temperature visualization of fluidizing particles

2002 ◽  
Vol 31 (3) ◽  
pp. 165-181 ◽  
Author(s):  
Jun Yamada ◽  
Norihisa Nagahara ◽  
Isao Satoh ◽  
Yasuo Kurosaki
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Fluidized Bed ◽  
Direct Contact ◽  
Heat Transfer Surface ◽  
Contact Heat ◽  
Bed Temperature ◽  
Contact Heat Exchange

Mechanisms of Heat Transfer Enhancement of Gas–Solid Fluidized Bed: Estimation of Direct Contact Heat Exchange From Heat Transfer Surface to Fluidized Particles Using an Optical Visualization Technique

1995 ◽  
Vol 117 (1) ◽  
pp. 104-112 ◽  
Author(s):  
Y. Kurosaki ◽  
I. Satoh ◽  
T. Ishize
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Fluidized Bed ◽  
Flow Rate ◽  
Direct Contact ◽  
Heat Transfer Surface ◽  
Heat Transfer Tube ◽  
Transfer Tube ◽  
Contact Frequency ◽  
Fluidized Particles

This paper deals with mechanisms of heat transfer in a gas–solid fluidized bed. Heat transfer due to heat exchange by direct contact from a heat transfer tube immersed in the bed to fluidized particles was studied by means of visualization of contact of the fluidized particles to the heat transfer surface. The results show that the duration of contact of fluidized particles was almost uniform over the tube circumference and was hardly affected by the flow rate of fluidizing gas. On the other hand, the contact frequency between the particles and heat transfer tube was evidently influenced by the gas flow rate and particles diameter, as well as the location on the tube circumference. Using the visualized results, the amount of heat conducted to fluidized particles during the contact was estimated. This result showed that unsteady heat conduction to the fluidized particles plays an important role in the heat transfer, especially at the condition of incipient fluidization.

Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part II — Void Fraction

2002 ◽  
Author(s):  
S. Abdulla ◽  
X. Liu ◽  
M. H. Anderson ◽  
R. Bonazza ◽  
M. L. Corradini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Liquid Metal ◽  
Void Fraction ◽  
Direct Contact ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Test Facility ◽  
Contact Heat ◽  
Contact Heat Exchange

One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. In order to investigate the interfacial transport phenomena, heat transfer and operational stability of direct liquid-liquid contact, a series of experiments are being performed in a 1-d test facility at Argonne National Laboratory and a 2-d experimental facility at UW-Madison. Each of the experimental facilities primarily consist of a liquid-metal melt chamber, heated test section (10cm diameter tube for 1-d facility and 10cm × 50cm rectangle for 2-d facility), water injection system and steam suppression tank. This paper is part II which, primarily addresses results and analysis of a set of preliminary experiments and void fraction measurements conducted in the 2-d facility at UW-Madison, part I deals with the heat transfer in the 1-d test facility at Argonne National Laboratory. A real-time high energy X-ray imaging system was developed and utilized to visualize the multiphase flow and measure line-average local void fractions, time-dependent void fraction distribution as well as estimates of the vapor bubble sizes and velocities. These measurements allowed us to determine the volumetric heat transfer coefficient and gain insight into the local heat transfer mechanisms. In this study, the images were captured at frame rates of 100 fps with spatial resolution of about 7mm with a full-field view of a 15cm square and five different positions along the test section height. The full-field average void fraction increases rapidly to about 15% in these preliminary tests, with the apparent boiling length of less than 20cm. The volumetric heat transfer coefficient between the liquid metal and water are compared to the CRIEPI data, the only prior data for direct contact heat exchange for these liquid metal/water systems.

scholarly journals Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part I — Heat Transfer

2002 ◽  
Author(s):  
D. H. Cho ◽  
R. J. Page ◽  
D. Hurtault ◽  
S. Abdulla ◽  
X. Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Molten Metal ◽  
Direct Contact ◽  
Water Flow Rate ◽  
Contact Heat ◽  
Saturated Water ◽  
Contact Heat Exchange ◽  
Initial Results ◽  
Steam Production

Experiments on direct-contact heat exchange between molten metal and water for steam production were conducted. These experiments involved the injection of water into molten lead-bismuth eutectic for heat transfer measurements in a 1-D geometry. Based on the initial results of the experiments, the effects of the water flow rate and the molten metal superheat (temperature difference between molten metal and saturated water) on the volumetric heat transfer coefficient were discussed.

Air Molten Salt Direct-Contact Heat Exchange

1985 ◽  
Vol 107 (3) ◽  
pp. 208-214 ◽  
Author(s):  
M. S. Bohn
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Direct Contact ◽  
Packed Column ◽  
Economic Benefits ◽  
Finned Tube ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Contact Heat ◽  
Contact Heat Exchange

Volumetric heat transfer coefficients for direct-contact heat exchange between air and molten nitrate salt have been measured as a function of air and salt flow rates at 350° C salt inlet temperature. Using these heat transfer data for a packed column-type heat exchanger, an economic analysis was used to compare direct-contact heat exchange with conventional finned-tube heat exchangers. High volumetric rates of heat transfer (2000–3000 W/m3 °C) and flexibility in choice of materials of construction allow one to realize significant economic benefits by using direct-contact heat exchange in this application.

Liquid-Metal/Water Direct Contact Heat Exchange: Flow Visualization, Flow Stability, and Heat Transfer Using Real-Time X-Ray Imaging

2005 ◽  
Vol 150 (2) ◽  
pp. 182-220 ◽  
Author(s):  
Sherif H. Abdulla ◽  
Xin Liu ◽  
Mark H. Anderson ◽  
Riccardo Bonazza ◽  
Michael L. Corradini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Liquid Metal ◽  
Flow Visualization ◽  
Direct Contact ◽  
Exchange Flow ◽  
Contact Heat ◽  
X Ray ◽  
X Ray Imaging ◽  
Contact Heat Exchange
Sign in / Sign up

Export Citation Format

Share Document