Abstract: A direct expansion evaporator includes an inner guiding duct defining a feeding channel for guiding raw material, and an outer guiding duct enclosing the inner guiding duct therewithin to form a heat exchange channel between the outer and inner guiding ducts for guiding refrigerant flowing along the heat exchange channel to heat-exchange with the raw material along the feeding channel, wherein a helix indention is formed at the outer guiding duct to form the heat exchange channel partitioned by a helix partition, wherein a peak of the helix partition is biased against an outer surrounding wall of the inner guiding duct to conceal the heat exchange channel along the inner guiding duct in a weld-less manner.

Abstract: A direct expansion evaporator for making a frozen product from raw material includes a feeding channel, a heat exchange channel thermally communicating with the feeding channel, and a refrigerant flowing within the heat exchange channel for exchanging heat between the raw material within the feeding channel and the refrigerant within the heat exchange channel in an expanded evaporation manner. Therefore, the refrigerant releases the thermal energy via the phase changing from liquid to gaseous state of the refrigerant. The heat exchange channel has a pre-cooling portion for pre-cooling the raw material at a predetermined temperature and a freezing portion for freezing the raw material to a final predetermined temperature of the frozen product in two-stage evaporation manner. Thus, the direction expansion evaporator provides a relatively more efficient way for making the frozen product, so as to increase the quality of the frozen product.