Direct Evaporative Air Handler With Air Bypass Humidity Control
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Solution Overview
Problem
Direct evaporative air handlers face challenges in controlling temperature and humidity in data centers under varying ambient conditions, particularly in cold weather where humidification can lead to freezing of evaporative media and in warm conditions where cooling and humidity control are difficult.
Innovation Solution
The air handler design includes an evaporative cooler with multiple air ports and dampers that allow for selective mixing of outdoor and recirculated air streams, enabling precise control of supply air temperature and humidity through different operation modes, including bypassing the evaporative cooler for outdoor air and using wetted stages to humidify recirculated air, thus preventing freezing and optimizing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If outdoor air is cooled using discrete evaporation steps, then cooling effect is achieved, but the air becomes too cool or too humid
Solution Approach 1:
The evaporative cooler is divided into multiple stages or sections, each capable of independent operation. This allows the system to apply evaporation cooling in controlled increments rather than as a single discrete step, enabling precise control of the cooling effect and preventing over-cooling or excessive humidification.
Solution Approach 2:
The system dynamically adjusts the operation of different evaporative cooler stages based on real-time conditions. By making the cooling process adaptive and controllable rather than fixed, the system can maintain supply air temperature within desired ranges while preventing harmful effects of over-cooling.
2Quantity of substance
If evaporative media is wetted to humidify outdoor air in cold weather, then humidity is increased, but the evaporative media freezes
Solution Approach 1:
Different sections of the evaporative cooler are treated differently based on local conditions. The system can selectively wet or dry specific stages depending on the ambient temperature and humidity requirements, allowing humidification in warmer sections while keeping sections exposed to cold outdoor air dry to prevent freezing.
Solution Approach 2:
The multi-stage evaporative cooler acts as an intermediary between outdoor air and the indoor space. By introducing intermediate cooling stages, the system can gradually condition the air, allowing humidity control without subjecting the evaporative media to freezing temperatures that would occur with direct exposure to cold outdoor air.
3Reliability
If control signal stops wetting the media, then over-humidification is prevented, but the media remains wet for a significant period continuing to cool and humidify
Solution Approach 1:
The evaporative media is divided into multiple independent sections or stages that can be controlled separately. When humidification needs to be stopped, only specific sections are dried while others may remain wet, significantly reducing the overall time for the system to respond to control signals and preventing prolonged over-humidification.
Solution Approach 2:
Rather than requiring complete drying of all media sections to stop humidification, the system achieves effective control by drying only the necessary portions. This partial action approach allows the system to respond quickly to control signals while maintaining sufficient humidification capacity when needed.
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 design achieves optimal energy efficiency, minimizes air stratification, and maintains humidity within desired limits, providing improved control of temperature and humidity under diverse ambient conditions while preventing freeze risks during cold operations.
Implementation Method 1
cooling outdoor air is accomplished with discrete evaporation steps
Implementation Method 2
The supply fan can be positioned downstream of the evaporative cooler, and can be configured to draw air through the outdoor air port, outdoor air bypass port, first return air port, and second return air port
Data Source
AI summary
A direct evaporative air handler for providing supply air to humidify and cool an enclosed space such as a data center. The air handler includes an evaporative cooler and a return air port that is positioned upstream of the evaporative cooler to allow recirculated air from the enclosed space to pass through the evaporative cooler. The air handler includes an additional return air port that is positioned downstream of the evaporative cooler to allow recirculated air from the enclosed space to bypass the evaporative cooler. The air handler includes an outdoor air port that is positioned upstream of the evaporative cooler to allow outdoor air to pass through the evaporative cooler and further includes an outdoor air bypass port that allows outdoor air to enter the air handler without passing through the evaporative cooler. The temperature and humidity of the supply air can be controlled under various ambient conditions by controlling the amount of air that enters the air handler through each port.