Experimental study of solving thermal heterogeneity problem of data center servers

- Increasing server power density increases its surface temperature heterogeneity.
- Variation of servers air flow rates leads to better thermal performance.
- Uniform increase of server's air flow rates enhances thermal performance.
- Proper scheme of servers air flow rates maintains all servers at the low temperature.

Desirable thermal management of data center requires uniform temperature distribution along the servers. Hot air recirculation and cold air bypass in data center leads to non-homogeneous cold air distribution along the servers of the racks which may lead to heterogeneous temperatures distribution along the servers. The present work aims to experimentally study the possibility of controlling these heterogeneous temperature distributions by controlling the cold air flow rates along the servers. A physical scaled data center model was used to conduct this investigation. The effectiveness of thermal management of the servers racks of the data centers has been expressed in terms of intake, rare and surface temperature distributions along the rack servers and the supply and return heat indices (commonly symbolized as SHI and RHI; respectively). Excessive tests were firstly performed under uniform servers fans speed (uniform air flow rates through the different servers). Then the air flow rates distributions along the racks servers has been changed by regulating the server's fans speeds using different schemes of fans speeds regulations at different data centers power densities. It is concluded that a uniform increase of server's flow rate from the bottom to the top of servers rack cabinet provides (i) the lowest temperature at both cooling aisle (around 10%) and exhaust aisles (around 5%), (ii) the best uniform surface temperature of all rack servers (as the standard deviation is reduced from 10 to around 2), and (iii) the best values of thermal management metrics (SHI and RHI) typically SHI is reduced by around 20% while RHI is increased by around 3% to approach the targeted values; 0.1 and 0.9, respectively.