Abstract
This paper presents a sizing study of the buffer tank in chilled water A/C systems. In order to
find out the adequate sizing criteria for buffer tanks in these kind of installations, a review of
different manufacturers' guidelines was carried out and it was concluded that there are three main
operation parameters affected by the volume of the tank: the ON cycle time, the OFF cycle time,
and the number of starts per hour of the chiller compressor. In order to better understand the
influence of each parameter, a theoretical analysis was carried out where the impact of the
building thermal load in different design criteria was also studied. After a thorough analysis of
all the studied criteria, it was concluded that the minimum ON cycle time which is necessary to
ensure that the oil returns to the compressor is the most critical criterion. Finally, a design
guideline is proposed by the authors in order to determine the minimum volume of the buffer
tank, mainly depending on the capacity of the chiller and the temperature deadband of the
thermostat control.
