The hka class has been developed by HTT for heating, cooling and deep-freezing in the temperature area of between -80°C and +400°C. The hka units work with uniform heating media, are free of corrosion, non-toxic and are also optionally food-safe. This is made possible by the special construction method which avoids direct contact between the primary energy source and the consumer. The heating medium is not direct, but is connected with the primary energy source via a heat exchanger. In this way, the heating medium works simultaneously as a divider between the reaction product and the environment. A definite safety advantage, in particular for the chemical, pharmaceutical and food industries.