Experimental study on application of secondary return air to small constant temperature and humidity systems

Constructs a small constant temperature and humidity system and tests the energy saving effect, control precision and anti-disturbance ability with fixed dew point control and static adjustment method by adjusting the mixing ratio of secondary return air to primary return air under the summer working condition. The results show that the secondary return air system can effectively reduce the reheating capacity compared with the primary return air system. With the increase of the secondary return air rate, the heating capacity gradually decreases, and when the regulating valve of the secondary return air opens to 50%, the heating capacity reduces to 31%. The system operates stably, and the temperature fluctuation range is ±0.3 ℃, and the relative humidity fluctuation range is ±2%. For the secondary return air system under the fixed mixing ratio, the indoor disturbance has a greater effect on the indoor temperature and humidity control fluctuation than the outdoor disturbance. This system not only can effectively reduce the reheating capacity, but also has good anti-disturbance ability and high control accuracy.