Seasonal Free Cooling for University Data Center

The design and implementation of a free cooling system to chill water for the UI campus, during the winter months, is the main goal of this project. By considering system economics, environmental impact, and  overall optimization, among other factors, the designed system will provide an efficient, cost-saving method of cooling water through the use of cold ambient air.

Problem Definition
Currently, to chill water for campus, the University uses vapor-compression chillers throughout the entire year. While this process is able to handle the load, this type of system experiences problems during the winter time. The main issue is with the evaporative cooling towers, which are prone to ice build-up. The reason for this is that the cooling water is directly exposed to the freezing conditions. When this build-up happens, damage may occur to the system, so ice must be manually removed from the cooling towers. There are a few methods for ice removal, but none of them are very efficient and all require human intervention into an otherwise automated system. Other than freezing, which interrupts system operation and is hard on equipment, other issues include working fluids freezing within pipes and flash freezing of humid exhaust air.

Background
Free cooling, also known as enterprise cooling, involves utilizing relatively low temperature ambient air to cool a working fluid within a system. Conversely, a conventional method for completing the same task would be to use a vapor-compression chiller. However, free cooling is enticing for a few reasons. First, air is a working fluid within the system that does not have an associated monetary cost, hence the name "free" cooling. Secondly, operational costs for a free cooling system are generally lower, due to the fact that pumps and fans are the only main components that must be powered. In a conventional system, compressors and cooling towers, along with pumps, produce a much higher power demand while operating. Finally, a free cooling system can be a completely enclosed system, protecting it from the environment and eliminating the need for make-up water and continuous chemical treatment of the system.

Deliverables
For this project, the final product will be a complete design and analysis, with supporting calculations, of a free cooling system to chill water for the UI campus during the winter season. Once our design has been approved, the University will purchase and install the components outlined in our design to create a full scale, operational free cooling system.

Project Design
The following information provides evidence and reasoning for the decisions that we made during the design of our system. Above is a comparison of two potential heat exchangers for use in our system, along with a table of important values from a hypothetical test system. Below are two schematics of our system, the first being a general system outline that shows all of the main components and the second being a floor plan of the actual installation location with options for placement of our system.