Abstract: In order to improve the efficiency of energy transmission, a device for temperature control and a heat exchanger is characterized in that the heat exchanger is embodied as a plastic heat exchanger (1), that the energy transmission bodies (10.1, . . . 10.n) comprise first sectional hollow body members (11.1, . . . , 11.n) made of a conducting plastic material with a thermal conductivity (?) of approximately 1.0 to 50.0 [W/(mK)] and are arranged on the second sectional hollow body members (12.1, . . . , 12.n) of a plastic material with a thermal conductivity (?) of approximately 0.001 to 1.0 [W/(mK)], that the first sectional hollow body members (11.1, . . . , 11.n) are enclosed by an energy conductor (13) composed of a further conducting plastic material with a thermal conductivity (?) of approximately 1.0 to 50.0 [W/(mK)], and that a heat insulating body member (14) composed of an insulating plastic material is arranged on the second sectional hollow body members (12.1, . . . 12.n).