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Title: An experimental study on sub-cooled flow boiling CHF of R134a at low pressure condition with atmospheric pressure (AP) plasma assisted surface modification

In this study, sub-cooled flow boiling critical heat flux tests at low pressure were conducted in a rectangular flow channel with one uniformly heated surface, using simulant fluid R-134a as coolant. The experiments were conducted under the following conditions: (1) inlet pressure (P) of 400-800 kPa, (2) mass flux (G) of 124-248 kg/m2s, (3) inlet sub-cooling enthalpy (ΔHi) of 12~ 26 kJ/kg. Parametric trends of macroscopic system parameters (G, P, Hi) were examined by changing inlet conditions. Those trends were found to be generally consistent with previous understandings of CHF behavior at low pressure condition (i.e. reduced pressure less than 0.2). A fluid-to-fluid scaling model was utilized to convert the test data obtained with the simulant fluid (R-134a) into the prototypical fluid (water). The comparison between the converted CHF of equivalent water and CHF look-up table with same operation conditions were conducted, which showed good agreement. Furthermore, the effect of surface wettability on CHF was also investigated by applying atmospheric pressure plasma (AP-Plasma) treatment to modify the surface characteristic. With AP-Plasma treatment, the change of microscopic surface characteristic was measured in terms of static contact angle. The static contact angle was reduced from 80° on original non-treated surface to 15°more » on treated surface. An enhancement of 18% on CHF values under flow boiling conditions were observed on AP-Plasma treated surfaces compared to those on non-treated heating surfaces.« less
Authors:
 [1] ;  [2] ;  [3]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
  3. Univ. of Illinois, Urbana, IL (United States). Dept. of Nuclear, Plasma and Radiological Engineering
Publication Date:
OSTI Identifier:
1178046
Report Number(s):
INL/JOU--14-32460
Journal ID: ISSN 0017-9310; TRN: US1500188
DOE Contract Number:
AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Heat and Mass Transfer; Journal Volume: 81; Journal Issue: C
Publisher:
Elsevier
Research Org:
Idaho National Laboratory (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; PRESSURE RANGE KILO PA; SUBCOOLED BOILING; SURFACES; WATER; CRITICAL HEAT FLUX; ENTHALPY; MODIFICATIONS; HEATING; MASS TRANSFER; SCALING LAWS; WETTABILITY; REFRIGERANTS; SURFACE TREATMENTS CHF; SUB-COOLED FLOW BOILING; SURFACE MODIFICATION; SURFACE WETTABILLITY