Improving chiller performance by optimizing operating conditions of ice storage tanks

Ice storage tanks (ISTs) are utilized to reduce electricity consumption during peak hours and to optimize costs in air conditioning systems. ISTs can also help improve the performance of the chiller in an air conditioning system when it operates in conjunction with a chiller. In the conventional method, the output flow temperature from IST (OTIST) is kept constant by a thermostatic valve. In this study, a novel design for air conditioning systems equipped with IST is proposed to increase the performance of the chiller during the discharging period by adjusting the output temperature from the IST (OTIST). The improvement is due to an increase in the output temperature from the chiller (COT) during the discharging period. In this method, the OTIST is set according to the required cooling load. A model for internal melt ice-on-coil tanks in charging and discharging periods is proposed using fundamental heat transfer analysis to evaluate and compare this method with a conventional one. Moreover, the paper suggests a procedure to design suitable ISTs for this purpose. The performance of the method is studied for three common types of air conditioning systems, CAV, VAV, and fan coil units (FCUs), through two real case studies. It is found that the method is more efficient for CAV than FCUs and VAV systems. In the case studies, the method gives ۳.۴%, ۵.۴%, and ۲.۶% improvement in COP for CAV, VAV, and FCU systems, respectively. Moreover, the reheat mechanism in CAV systems can be eliminated by the proposed method.

کلیدواژه ها:

Melt Ice-On-Coil Tanks ، Ice Storage System ، Air conditioning system ، Partial Storage Control ، Chiller Performance ، Thermal Storage System