Indirect Evaporative Cooling With AAHX for Clean Data Center Air
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Solution Overview
Problem
Current cooling systems for enclosed spaces, such as data centers, face challenges including high energy consumption, dust accumulation, contaminant transfer, and limited climate suitability due to existing evaporative and air-side/water-side economizer methods, which also require frequent maintenance and can lead to reduced air quality and equipment inefficiencies.
Innovation Solution
A combination of a direct evaporative cooler (DEC) in a scavenger air stream and an air-to-air heat exchanger (AAHX) is used to indirectly and sensibly cool process air, with a pre-cooler coil and direct expansion cooling system to achieve target temperatures, reducing the need for backup chillers and minimizing contaminant transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If air-side economizer is used to reject heat from data center, then energy consumption is reduced, but dust accumulation and air contaminants increase inside the space
Solution Approach 1:
The patent introduces an air-to-air heat exchanger as an intermediary device between the outdoor air stream and the process air stream. This heat exchanger enables heat rejection without direct mixing of outdoor air with the data center environment, thus reducing energy consumption while preventing dust and contaminant ingress. The heat exchanger acts as a mediator that transfers thermal energy without allowing particulate matter to pass through.
2Use of energy by moving object
If direct evaporative cooler is used to cool buildings, then energy efficiency is improved, but supply air temperature control becomes challenging and humidity increases
Solution Approach 1:
The air-to-air heat exchanger serves as an intermediary that decouples the evaporative cooling process from the supply air delivery. The heat exchanger allows the system to achieve evaporative cooling efficiency while maintaining precise control over supply air temperature and humidity by transferring heat indirectly rather than through direct contact with evaporative media.
3Temperature
If direct evaporative cooler is used, then cooling performance is improved, but bacteria, algae, fungi and contaminants proliferate in the water system
Solution Approach 1:
The air-to-air heat exchanger acts as a barrier that prevents direct contact between the evaporative cooling water system and the process air stream. This intermediary arrangement allows the system to maintain evaporative cooling performance while isolating the water system from air quality concerns, thereby reducing the proliferation of bacteria, algae, and fungi in the air supply.
4Temperature
If evaporative cooler operates at wet bulb temperature, then cooling is achieved, but cooling temperatures below wet bulb temperature cannot be reached
Solution Approach 1:
The air-to-air heat exchanger enables the system to achieve temperatures below the wet bulb temperature by allowing heat rejection to outdoor air at lower temperatures. The heat exchanger mediates the heat transfer process, enabling the process air to be cooled to temperatures lower than what direct evaporative cooling alone can achieve, thus expanding the system's adaptability to various climate conditions.
5Temperature
If water-side economizer (cooling tower) is used, then cooling capacity is increased, but water mineral deposition, micro-organisms and corrosion increase
Solution Approach 1:
The air-to-air heat exchanger serves as an intermediary that replaces the water-based cooling tower system with an air-based heat rejection system. This eliminates the harmful effects associated with water-side economizers, including mineral deposition, micro-organism growth, and corrosion, while maintaining cooling capacity through direct air-to-air heat exchange.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances cooling performance, reduces energy consumption, and extends the operating range of evaporative cooling systems, providing better humidity control and minimizing maintenance needs while maintaining indoor air quality.
Implementation Method 1
a direct evaporative cooler (DEC) in a scavenger air stream
Implementation Method 2
an air-to-air heat exchanger (AAHX) exchanging heat between the scavenger air stream and a process air stream
Data Source
AI summary
Systems and methods for controlling temperature in an enclosed space can include an air-to-air heat exchanger (AAHX) and a direct evaporative cooler (DEC). The DEC can be located in a scavenger or outdoor air stream such that the DEC cools the outdoor air, which is then used to cool or reject heat from a process air stream passing through the AAHX. In an example, the AAHX can be a sensible wheel. In another example, the AAHX can be a counter-flow flat plate. The system can operate in various modes, including an economizer mode and an evaporation mode, depending, in part, on the outdoor air conditions and a load on the system. In some examples, the system can include a DX coil to provide additional cooling to the process air in another operating mode.