Evaluation of the length of refrigerant pipeline for multi-Unit air conditioners based on pressure drop model and validation
The length of refrigerant pipeline of the multi-unit air conditioners deter-mines the refrigerant transmission and oil return scheme.Accurately identifying the pipe length of the multi-unit air conditioners can improve the refrigerant transmission and oil return,consequently making the system more energy saving.A method for identifying the length of refrigerant pipeline based on refrigerant pressure drop model is proposed.In this method,a generalized heat balance method for compressor based on isentropic efficiency is established to iteratively calculate the mass flow rate of refrigerant;a pressure drop model of the main and end branches is established based on the drag weighting coefficient of the number of indoor unit to accurately evaluate the pressure drop of the main and branch pipes under different load rates;a refrigerant pipe length model with uncertainty guided by the length and resistance of the end branch pipe is proposed to evaluate the length of the refrigerant pipeline.The experimental validation shows that for the pipe length calcu-lated by the method described in this paper,for the short pipe(L=15 m),the average length calculation error under each working condition is less than 10%;for the long pipe(L=150 m),the average length calculated by the model is 141 m,and the calculation er-ror under each working condition is less than 20%.The proposed model can effectively o-vercome the difficulty to distinguish pipe length by simple pressure drop under part load conditions.
multi-unit air conditionerrefrigerant pipelinepressure dropmodelingevaluation
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NSTL
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