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/m(2) s, (3) inlet sub-cooling enthalpy (Delta H-i) of 12-26 kJ/ kg. Parametric trends of macroscopic system parameters (G,P,Delta H-i) 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 degrees on original non-treated surface to 15 degrees 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. Published by Elsevier Ltd.