Experimental Demonstration of Local Air Conditioning System Utilizing Low-Pressure Refrigerant at Data Center

Abstract

In this study, air conditioning system with two-phase rear door heat exchanger utilizing vapor compressor cycle for data center application has been developed. As rear door heat exchanger is directly installed at rack's rear side, thereby, allowing heat reception at higher temperature and larger heat exchanging surface area per unit heat load as compared to room air conditioning system. As a unique feature, low-pressure refrigerant (Saturated pressure 0.1 MPaA at 35°C) having low global warming potential ( $\text{GWP}=400$ ) in contrast to high pressure one has been utilized, resulting in easier maintenance and safer operation. On the other hand, low-pressure refrigerant requires large diameter piping system because system performance is sensitive to pressure drop. This problem is solved by utilizing multiple smaller diameter pipes (19.05 mm) layout instead of single large pipe. COP evaluation of developed air conditioning system is performed at a live data center in Southern India (Yearly average outdoor temperature = 28°C). The developed air conditioning system achieved $\text{COP} =3.2$ as compared to $\text{COP}=1.6$ of installed room air conditioning system at the data center.