The present invention discloses a generator (1100) of a cooling machine which is a tube-in-tube heat exchanger housing a plurality of ascending tubes (1160) surrounded by a generator jacket tube (1105) forming a jacket cavity (1199). The ascending tubes (1160) are operative to receive a refrigerant-rich solution via a solution intake (1110) of the generator jacket tube (1105). The jacket cavity (1199) is operative to receive a heating medium via a heating intake (1140), and the ascending tubes (1160) are held in a fixed position within the generator jacket tube (1105) by a lower end plate (1151) and/or an upper end plate (1152); characterized in that the ascending tubes (1160) are constructively arranged with the heating intake (1140) and the generator jacket tube (1105) such that at least a lower portion (1161) of the ascending tubes (1160) remain substantially unheated by the heating medium provided by the heating intake (1140).
