A direct expansion ammonia refrigeration system and a method of direct expansion ammonia refrigeration is described and which includes a source of liquid ammonia refrigerant which is delivered in fluid flowing relation to a plurality of evaporator tubes which incorporate wicking structures, and which through capillary action facilitated by the wicking structures are effective for drawing liquid ammonia refrigerant along the inside facing surface of the evaporator tubes so as to substantially reduce any stratified and/or wavy flow patterns of the liquid ammonia refrigerant within the evaporator tubes. The invention further includes a novel accumulator vessel and heat exchanger vessel which are coupled in fluid flowing relation relative to the direct expansion ammonia refrigeration system and which facilitate the removal of water from the ammonia refrigerant in order to enhance the operation of the direct expansion ammonia refrigeration system.