Flow boiling of ammonia in vertical small diameter tubes: Two phase frictional pressure drop results and assessment of prediction methods

► Two phase pressure drop experiments of ammonia are performed in mini channels. ► Parametric effects on the two phase pressure drop are presented. ► Pressure drop is observed to increase with mass flux and vapour quality. ► Pressure drop is observed to be lower for higher saturation temperatures. ► New correlation is proposed which agreed well with experimental data.