Performance Optimization Of The Condensing Exhaust Air Heat Recovery Fresh Air All-in-One Unit

Facing the joint challenge of environmental protection,energy conservation,economy and indoor air quality,the all fresh air handling units as an effective air purification equipment has received extensive attention and research on its energy-saving optimization design.The use of exhaust heat recovery devices is an important direction for the optimization of the all fresh air handling units.The condensing exhaust air heat recovery fresh air all-in-one unit is a combination of a all fresh air handling units and a heat pump system,and it uses a building exhaust as a condensing air.Aimed at the shortcomings of heat pump exhaust heat recovery technology in the application of the all fresh air handling units,this paper established a test rig and the Simulink system simulation model for the condensing exhaust air heat recovery fresh air all-in-one unit to study the running performance of the unit by using the combination of experiment and simulation,and established the Simulink-M file hybrid programming optimization model by using the Simulink-M file hybrid programming method.The main contents of this paper are as follows:(1)For the actual needs of the condensing exhaust air heat recovery fresh air all-in-one unit,this paper selected and simplified the mathematical model of the components established by the predecessors,established a mathematical model for each component of the condensing exhaust air heat recovery fresh air all-in-one unit,and make appropriate assumptions for the model;(2)Established a test rig for the condensing exhaust air heat recovery fresh air all-in-one unit and test the reliability of the Simulink system simulation model for the condensing exhaust air heat recovery fresh air all-in-one unit;(3)The Simulink system simulation model was applied to research the variable air volume performance and the variable environmental conditions performance of the condensing exhaust air heat recovery fresh air all-in-one unit;(4)Aiming at the performance variation characteristics of the condensing exhaust air heat recovery fresh air all-in-one unit,the optimization method of the condensing exhaust air heat recovery fresh air all-in-one unit was explored,and the minimize 1/COP of the unit was taken as the optimization target,established the Simulink-M file optimization model to obtain the optimal control strategy for the bypass fresh air volume by using the Simulink-M hybrid programming method.The result shows:the error between the simulation results and the experimental results is small,the models can correctly reflect the performance changes of the unit during operation;Under the condition of variable air volume,with the increase of bypass fresh air volume,the oncoming air speed of the condenser increases,the refrigerant pressure of the inlet and outlet of the compressor decreases,the cooling capacity increases first and then gradually becomes gentle,and the input power decreases first then increases,so the COP of unit has a tendency to increase first and then decrease;Under variable environmental conditions,the performance parameters of unit are affected by the inverter compressor.As the ambient temperature increases,the frequency of the compressor increases,the refrigerant pressure and condensing temperature at the outlet of the compressor gradually increase,the refrigerant pressure at the inlet of the compressor and the evaporating temperature change gently,and the cooling capacity and input power of compressor gradually increase.The COP of unit is maximum when the ambient dry bulb temperature is 29℃;The optimal operating conditions of the unit are also affected by the temperature and air volume of the bypass fresh air.Under different ambient temperatures,each ambient temperature corresponds to an optimal bypass fresh air volume that maximizes the COP of the unit.And as the ambient temperature increases,the optimal bypass fresh air volume increases first then decreases;The optimal control strategy for the new air volume of the condensing exhaust air heat recovery fresh air all-in-one unit is proposed:in order to maintain the best operating COP of the unit at all times,system can adjust the new damper accurately to controlled the bypass air volume,and the frequency of compressor and exhaust fan can be coordinated and adjusted at the same time by monitoring the outdoor environment temperature.