Experimental and numerical study of water-cooled datacom equipment

• A study of an electronic rack cooled by air to water heat exchanger is carried out.
• Experimental study with a substantial instrumentation at different scales is performed.
• The energy efficiency of the cooling system is highlighted.
• Numerical model of the system by using nodal approach is defined and validated.

This paper presents an experimental and numerical study of an electronic rack cooled by a finned tube heat exchanger. The objectives are to evaluate cooling and energy performance of this system and formulate a numerical model based on measurements. Experimentation has been carried out using commercial servers. A substantial instrumentation has been conducted at different scales (servers, rack and exchanger). Several tests have been made with different sets of parameters like water inlet temperature or power dissipated by servers. In each case, the heat exchanger has removed more than 90% of electrical power consumed by the rack (with no chiller use). Furthermore, promising results are obtained with this system, especially the reduction of energy consumption of cooling part compared to traditional air cooling. Finally, the rack and heat exchanger are simplified into two numerical models which can predict temperature outputs as a function of defined inputs (water and air flow rate and temperature, power dissipation). Validation tests have been carried out with different sequences of measure and numerical models have given satisfactory results. They will be duplicated to compute the impact of this cooling system at a data center room scale.