Further study on the inherent operating characteristics of a variable speed direct expansion air conditioning system

• Steady state experiments carried out under different inlet air states to a VS DX A/C system.
• Different inlet air states influenced the system inherent operational characteristics.
• A data processing method developed to estimate the ICs at non-test inlet air states with accuracy.
• It paved the way to developing advanced control strategy for DX A/C system.

Further to a previous experimental study on the inherent operational characteristics of an experimental variable speed (VS) direct expansion (DX) air conditioning (A/C) system at only two inlet air states, an experimental study using the same experimental VS DX A/C system at six different inlet air states to the DX A/C system has been carried out and the study results are presented in this paper. The results suggested that different inlet air states to a DX A/C system influenced the operational characteristic of the system, in terms of the Inherent Correlation (IC) between its output total cooling capacity (TCC) and Equipment sensible heat ratio (SHR). Therefore, a further data processing method was developed using regression, by which the ICs of the VS DX A/C system at non-test inlet air states can be predicted with adequate accuracy. This has therefore paved way to developing advanced control strategies for indoor thermal environment (i.e., air temperature and humidity) based on the known or predicted ICs within the possible operating ranges of inlet air temperature and humidity to the DX A/C system, for better control accuracy and energy efficiency.