An investigation of multi-parameters effects on the performance of liquid-to-liquid heat exchangers in rack level cooling

As the demand for faster and more reliable data processing is increasing in our daily lives, the power consumption of electronics and, correspondingly, Data Centers (DCs), also increases. It has been estimated that about 40% of this DCs power consumption is merely consumed by the cooling systems. A responsive and efficient cooling system would not only save energy and space but would also protect electronic devices and help enhance their performance. Although air cooling offers a simple and convenient solution for Electronic Thermal Management (ETM), it lacks the capacity to overcome higher heat flux rates. Liquid cooling techniques, on the other hand, have gained high attention due to their potential in overcoming higher thermal loads generated by small chip sizes. In the present work, one of the most commonly used liquid cooling techniques is investigated based on various conditions. The performance of liquid-to-liquid heat exchange is studied under multi-leveled thermal loads. Coolant Supply Temperature (CST) stability and case temperature uniformity on the Thermal Test Vehicles (TTVs) are the target indicators of the system performance in this study. This study was carried out experimentally using a rack-mount Coolant Distribution Unit (CDU) attached to primary and secondary cooling loops in a multi-server rack. The effect of various selected control settings on the aforementioned indicators is presented. Results show that the most impactful PID parameter when it comes to fluctuation reduction is the integral (reset) coefficient (IC). It is also concluded that fluctuation with amplitudes lower than 1 °C is converged into higher amplitudes as we get closer to servers' and chips' temperatures.