A Transient CFD Study on Implementation of Dynamic Liquid Cooling for Series and Parallel Arrangement of Components in a Server at Rack Level

Direct-to-chip liquid cooling has been one of the promising solutions for cooling high-heat flux components. To enhance the efficiency of liquid cooling, current research focuses on optimizing the flow configurations and improving the cold plates' thermal performance, but in all the different cases the coolant is constantly pumped at a fixed flow rate across the system irrespective of the workload utilization at a server level. This results in excess pumping of coolant leading to a loss in efficiency. The flow through each server can be varied based on workload utilization to improve the pumping power efficiency. In this study, a transient analysis was performed by varying the flow rate across a server at rack level using CFD. Two models are created for this CFD study, one model mimicking four servers at different heights on a rack, and the components inside the server are placed in series and the other model with components arranged in parallel. The flow variation through each server is done using a valve arrangement representing a flow control device. To dynamically vary the flow rate, a controller is integrated to vary the flow based on the average outlet temperature. The pumping power is compared for a case where a constant flow rate is supplied and with cases where the flow rate is dynamically varied based on the thermal design power. The results shown analyze the impact of dynamic response for the flow control device placed at the outlet of the server with both configurations.