Energy efficiency of district cooling systems (1):Mathematical model

Based on the first law of thermodynamics, the definition of power consumption to heat supply ratio is proposed, including equipment power consumption to heat supply ratio, effective power consumption to heat supply ratio (pipeline power consumption to heat supply ratio), and subsystem power consumption to heat supply ratio. Based on the similarity criterion of power consumption to heat supply ratio, a general dimensionless system energy efficiency model of the district cooling system is proposed. This model is independent of the installed capacity of the system and has a normalized characteristic, and the system energy efficiency can be directly obtained from operating state parameters. The operating state parameters include the temperature difference of the fluid, pipeline pressure drop, and so on. The dimensionless system energy efficiency model proposed in this paper can be used as the basis for comparing the energy efficiency of different forms of district cooling systems, including traditional chiller systems, ice storage chiller systems, chilled water storage chiller systems, and so on. It can be used for system design optimization, equipment selection optimization, and operation optimization. This model is also suitable for the design and operation optimization of chiller plants of individual buildings, and has certain application value.