This invention relates to an apparatus for conditioning the temperature of a fluid by utilizing a thermoplastic heat exchanger (50) comprised of a plurality of hollow tubes. The apparatus controls the temperature of a process fluid inside the heat exchanger (50) via a controller (46) by adjustment of a control valve (64) that regulates the flow of an exchange fluid. The apparatus can be used to maintain the temperature of a chemical bath (12) and also to prepare discreet dispensed volumes of temperature controlled liquid.