Controlling internal temperature of e.g. an incubator cabinet equipped with heater and coolant compressor

摘要

A tempering cabinet containing an additional sensor which measures external ambient temperature, is new. A derived signal, is taken into consideration in the decision between heater- or coolant compressor operation. A temperature limit (Tg) is formed by adding the surrounding temperature (Tu) and a given parameter (Tp). Internal temperature (Ti) is controlled by the heater when the compressor is switched off, whilst the desired value (Tw) exceeds (Tg) and/or when heating is necessary. When the desired value (Tw) is below the limit (Tg) and/or when cooling is necessary, the heater is switched off and the compressor is switched on, providing a flow of coolant through the heat exchanger, under valved control. The latter permits introduction of compressed gaseous or liquid coolant into the heat exchanger in alternation. These are introduced in this way, when the deviation (Ti-Tw) lies close to zero and the temperature (Tw) lies below the limit (Tg) or when heat extraction is required. When the desired value (Tw) falls below the ambient (Tu) at control temperature differential (Tu-T)less than 0, essentially-liquid coolant is introduced into the heat exchanger until the control temperature differential approaches zero. During compressor operation, forced convection is effected internally using a fan facing the cabinet interior. Fan speed is controlled in accordance with internal temperature (Ti) and/or ambient (Tu) and/or the desired value (Tw). Fan speed is adjusted as a function of the operational state of the compressor. Forced convection can be interrupted during heater operation.