Numerical analysis of the methods for reducing the energy use of air-conditioning systems in non-uniform indoor environments

Abstract

Previous studies have shown that using efficient airflow distributions for a non-uniform indoor environment can reduce the space cooling load significantly. However, the system cooling load (SCL) of air-conditioning is decreased only a little when the fresh-air ratio is small, causing the limited decrease in the air-conditioning system energy use (SEU). To fully exploit the energy-saving potentials of efficient airflow distributions to reduce the SEU, the SCL in a large-space building with different airflow distributions was simulated, and the SEU was compared between using a single cooling source and the multiple low-grade cooling sources to handle the air. The results show that (1) efficient airflow distributions actually provide the potentials of using the multiple low-grade cooling sources to handle the air; in contrast, using a single cooling source will abandon the potentials and result in little energy saving; (2) using multiple low-grade cooling sources for cooling the supply air, return air, and fresh air can make the potentials available, and the energy-saving rate could be 13.9%–27.5% in the numerical cases with a displacement ventilation; (3) although the increase in the SCL for inefficient airflow distributions is little when the fresh-air ratio is small, the grade of cooling source is increased significantly so that 22.9% more energy is needed in the numerical case with a short-circuit ventilation. This study will be beneficial for the design of air-conditioning systems in non-uniform indoor environments with higher energy-saving capacity.