A modeling study on the effects of refrigerant pipeline length on the operational performance of a dual-evaporator air conditioning system

Multi-evaporator air conditioning (MEAC) systems are gaining greater and greater popularity because they offer building owners many advantageous over convenient chilled water based A/C systems, such as higher energy efficiency and flexibility in design and installation. However, while the coupling effects among operating parameters in evaporators of an MEAC system have been extensively studied, the influence of large pressure drop along the complicated refrigerant pipework of an MEAC system on the operating performance has not yet been investigated. This paper reports on a modeling study on the effects of refrigerant pipeline length on the operational performance of a dual-evaporator air conditioning (DEAC) system. To facilitate the intended modeling study, a physical-based steady-state mathematical model with a sub-module specifically devoted to accounting for the influence of refrigerant pipeline length on system operational performance has been developed. The model has been validated by comparing its prediction results with the experimental results previously reported by others. Using the model developed, the effects of refrigerant pipeline length on the operating performance of the DEAC system have been studied and are reported, and the layout optimization of a DEAC system was studied for the highest possible operational efficiency. Results of the study indicated that the DEAC system's COP decreased with an increase in the refrigerant pipeline length. The results also suggested that for a DEAC system, its highest COP would be resulted in when the outdoor unit was located equally between the two indoor units and its lowest COP when the outdoor unit was located close to either of the indoor unit.