The present invention relates to a self-contained, portable refrigeration unit having a construction arrangement which enables it to be compatible with several models, types and variations of refrigeratable compartments. This refrigeration unit is represented by a refrigeration module (1) capable of being removably fitted into a refrigeratable compartment, comprising a first portion (100) and a second portion (200) associated with each other. The first portion (100) is in contact with the inside of the refrigeratable compartment and the second portion (200) is in contact with the outside of the refrigeratable compartment, and in some embodiments of the present invention, the first portion (100) is capable of moving in relation to the second portion (200). The first portion (100) comprises at least a first closed box (101 ) interfacing the refrigeration module (1 ) with the inside of the refrigeratable compartment. The second portion (200) comprises at least a second closed box (201 ) interfacing the refrigeration module (1 ) with the outside of the refrigeratable compartment. In another preferred embodiment, the first box (101 ) fits into the refrigeratable compartment through a fitting portion (111 ) whose cross section is smaller than the largest cross section of the second box (201). The present invention also relates to a refrigeration system (500) comprising at least one embodiment of the portable refrigeration module (1 ) mentioned above.