Constant temperature and humidity air conditioning unit and control method

The invention discloses a constant temperature and humidity air conditioning unit and a control method. The constant temperature and humidity air conditioning unit comprises a circulation loop formed by sequentially connecting a compressor, a condenser, throttling devices and a main heat exchanger, and also comprises a four-way valve, an auxiliary heat exchanger and a humidifier, wherein the auxiliary heat exchanger is arranged between the main heat exchanger and an outlet of an air supply channel, the humidifier is arranged between a heat exchanger fan and the main heat exchanger, an end A of the four-way valve is connected with an output end of the condenser, an end C of the four-way valve is connected with a suction end of the compressor, an end B of the four-way valve is connected with an output end of the auxiliary heat exchanger through the first throttling device on one hand, and is connected with an input end of the main heat exchanger through the second throttling device on the other hand, an end D of the four-way valve is connected with an input end of the auxiliary heat exchanger, and a control unit is also connected with a temperature sensor and a humidity sensor. According to the air conditioning unit, energy of air conditioning refrigerants can be recycled to be used for heating air, no electrical heating pipe needs to be specially arranged, the energy utilization ratio is high, and the purpose of energy saving is achieved when a constant temperature and humidity condition is guaranteed.