Heat Transfer to Freon 12 Near the Critical State in a Natural-Circulation Loop

1960 ◽  
Vol 82 (3) ◽  
pp. 221-226 ◽  
Author(s):  
J. P. Holman ◽  
J. H. Boggs
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Critical Region ◽  
Critical State ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Natural Circulation Loop

An experimental investigation of heat transfer to Freon 12 in the critical region was conducted. A closed natural-circulation loop was used. Correlation of the data is presented. Separate equations are presented for reduced volumes less than one and for reduced volumes greater than one. The investigation covered a range of temperatures from 150 to 400 F and pressures from 500 to 950 psi.

Thermal Performance of Water-Based Suspensions of Phase Change Nanocapsules in a Natural Circulation Loop

2013 ◽  
Author(s):  
C. J. Ho ◽  
Chi-Ming Lai
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Natural Circulation ◽  
Pure Water ◽  
Circulation Loop ◽  
Core Material ◽  
Working Fluid ◽  
Outer Diameter ◽  
Natural Circulation Loop ◽  
Water Based

Experiments were conducted to investigate the heat transfer characteristics of water-based suspensions of phase change nanocapsules in a natural circulation loop with mini-channel heat sinks and heat sources. A total of 23 and 34 rectangular mini-channels, each with width 0.8 mm, depth 1.2 mm, length 50 mm and hydraulic diameter 0.96 mm, were evenly placed on the copper blocks as the heat source and heat sink, respectively. The adiabatic sections of the circulation loop were constructed using PMMA tubes with an outer diameter of 6 mm and an inner diameter of 4 mm, which were fabricated and assembled to construct a rectangular loop with a height of 630 mm and a width of 220 mm. Using a core material of n-eicosane and a shell of urea-formaldehyde resin, the phase change material nanocapsules of mean particle size 150 nm were fabricated successfully and then dispersed in pure water as the working fluid to form the water-based suspensions with mass fractions of the nanocapsules in the range 0.1–1 wt.%. The results clearly indicate that water-based suspensions of phase change nanocapsules can markedly enhance the heat transfer performance of the natural circulation loop considered.

A223 Heat Transfer and Flow Characteristics during Reflooding Process in Natural Circulation Loop

2014 ◽  
Vol 2014 (0) ◽  
pp. _A223-1_-_A223-2_
Author(s):  
Takuya Kawai ◽  
Ikki Yumoto ◽  
Takeyuki Ami ◽  
Hisashi Umekawa ◽  
Mamoru Ozawa
Keyword(s):  
Heat Transfer ◽  
Natural Circulation ◽  
Flow Characteristics ◽  
Circulation Loop ◽  
Natural Circulation Loop

Steady-State Behavior of a Two-Phase Natural Circulation Loop With Thermodynamic Nonequilibrium

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Dipankar N. Basu ◽  
Souvik Bhattacharyya ◽  
P. K. Das
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Control Parameters ◽  
Subcooled Boiling ◽  
Two Phase ◽  
State Behavior ◽  
Natural Circulation Loop ◽  
Steady State Behavior

A model to predict the steady-state behavior of a rectangular two-phase natural circulation loop has been proposed. The analysis employs a one-dimensional two-fluid model to identify various system parameters, with particular emphasis on the subcooled boiling region. The onset of two-phase region and point of net vapor generation and associated liquid temperatures and vapor qualities have been estimated using a few widely recognized correlations. Predicted results demonstrate that the consideration of subcooled boiling may have significant effect on system behavior, particularly around the transition regions. The interaction of saturated bubbles and subcooled liquid and associated change in heat transfer and frictional forces has been discussed in detail. Fluid stream has been observed to have different combinations of flow stream conditions at boiler exit and condenser inlet. Five probable combinations have been identified and a generalized working-regime map has been proposed on Nsub−NZu plane. Attempts have been made to identify the influence of various control parameters. A favorable sink condition (higher coolant flow rate or lower coolant entry temperature) has been found to be of particular importance to attain a wider operating range of wall heat flux and better heat transfer characteristics. A design map has been proposed to identify favorable operating condition in terms of control parameters to ensure complete condensation.

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