Dimensionless Parameter for Evaluation of Thermo-Fluids Performance of Air Conditioning and Ventilation Systems

Evaluation of effectiveness of air handling systems for cooling and ventilation is either non-existent or based on thumb rules. There is lack of quantifiable metrics to assess the performance of these systems vis-à-vis the environment. With the advent of high density, mission-critical datacenters and high energy demands it is necessary to develop metrics to evaluate the effectiveness and efficiency of thermal management provided by these systems. Hosting business and mission-critical applications at high power levels demand a high degree of reliability and flexibility in air conditioning systems. Energy consumptions of air handling equipment has also severely increased by over-designed fan systems, plenum designs and room layouts that allow the hot and cold air streams to mix. Lack of monitoring sensor network has added to this problem. In this paper, we formulate non-dimensional parameters to evaluate the thermal performance of air conditioning systems within a conditioned space. The parameters, based on temperature, reflect the convective heat transfer and fluid flow within the space and can be applied to commercial or non-commercial buildings as well. The self-similar parameters can be scaled from one unit to several units operating in the same room. Measurements from an experimental system are used to validate and correlate with monitored data from other sources. Dimensionless parameters in the form of Utilization Index (UI) are calculated, based on space temperature, outlet and inlet temperatures, for validation purposes. Experimental data show that UI provides a simple and powerful tool to understand the convective heat transfer and fluid flow in around the air conditioning system. Analysis based on Utilization index is carried out to understand air flow distribution among units.