A Test Study of Technology Cooling Loop in a Liquid Cooling System

Abstract

One of direct liquid cooling systems is consisted of two heat transfer loops: a primary loop and a technology cooling system (TCS) loop. The primary loop is similar as a facility loop in a traditional data center air cooling infrastructure. However, the primary loop has a CDU unit assembled in the loop instead of a CRAC/CRAH, or any other air handler equipment. The TCS loop is also called a secondary loop. In the TCS loop, the fluid circulates between CDU secondary loop and liquid cooling devices such as manifolds and cold plates. The design specifications and requirements of the two loops are in significantly different. For example, the operating parameters including liquid flow rate, temperature and pressure in the TCS loop are more critical, and they may be different from case to case in actual applications. As another example, the quality and composition of cooling fluid in the TCS loop are more critical than in the primary loop, and a very careful design is needed for the fluid in the TCS loop to ensure a long-term performance and reliability of a liquid cooling system. In addition, the IT equipment especially components such as CPU and GPU cards which are liquid cooled are in dynamic operating mode during most of the time. Therefore, the dynamic control of the TCS loop is critical and it should be carefully designed to provide proper fluid flow rate, temperature and pressure. In this work, several experiments are presented to characterize a TSC loop design in a liquid cooling system. The system performance at different operational conditions including flow rates, velocities and temperatures are studied. The environmental impact of air flow rate on the TCS loop performance are performed as well. Several TCS loop control test cases are designed and conducted, including different control logics and modes. The different control strategies are then analyzed and compared.