Time-delay characteristics of air-conditioning system for subway trains

Abstract

The time-delay characteristic of the air-conditioning system is the basis of predictive control of the air-conditioning system. The time-delay of the subway train's air-conditioning system can be divided into system response delay and carriage temperature change delay. Among them, the system response delay can be divided into two stages. The first stage is when the cooling load enters the carriage to the air-conditioning system starts to adjust; the second stage is when the air-conditioning system starts to adjust to the carriage temperature starts to decrease. In this study, the time-delay characteristics of the subway train's air-conditioning system are studied by numerical simulation and mathematical derivation. The accuracy of the calculation model was verified by comparing it with the field measurements data. Then, the influence of various factors on the time-delay characteristics of the air-conditioning system are analyzed. The results indicated that the system response delay time of the subway train's air-conditioning system increases exponentially with the instantaneous cooling load change and decreases linearly with the carriage design temperature. Moreover, the carriage temperature change delay of the air-conditioning system is related to the train carriage volume and temperature, the supply air volume and temperature, and the instantaneous cooling load change. However, the influence of the carriage and the supply air temperature on the carriage temperature change delay is minimal. Especially in the constant air volume air-conditioning system, the carriage temperature change delay is mainly affected by the instantaneous cooling load change.