Numerical Analysis of Two Phase Cross-Flow Heat Exchanger for High Power Density Equipment in Data Centers under Dynamic Conditions

Computational demand in the IT sector has increased dramatically and so rack level power densities from 10 to 50 kW/rack are increasingly common. Expanding the capabilities of the IT equipment requires thermal management systems able to handle time dependent thermal loads. Emerging system designs will almost certainly have to utilize close-coupled cooling subsystems to augment or replace traditional centralized perimeter air handlers. Distributed cooling technologies such as close-coupled rear-door heat exchangers, overhead heat exchangers, and in-row cooler heat exchangers have been developed to meet these high demands. To increase the thermal performance of the cross-flow heat exchangers, two phase flow is used with low-boiling-point refrigerants such as R134a, R407c, and R410a. In this study, a physics-based numerical model for cross-flow heat exchanger is developed in order to understand dynamic behavior. A system of partial differential equations for mass, momentum, and energy conservation has been solved using the finite difference method and implemented in MATLAB. Thermodynamic properties are obtained from COOLPROP. The dynamic model of cross-flow heat exchangers may be used to develop improved control strategies and increase energy efficiencies to meet the ever-increasing cooling demands of data centers.