Two-Circuit Counter-Flow Cooling for High Heat Rejection Data Centers
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Solution Overview
Problem
Conventional cooling systems are inefficient under varying load conditions and extreme environmental conditions, leading to increased energy consumption and maintenance costs, particularly in high ambient temperatures and high latent load environments, due to limitations in refrigerant systems and compressor operations.
Innovation Solution
A cooling system design featuring two separate liquid refrigerant pump systems with a series, counter-flow water flow arrangement and optimal flow rate control, allowing for higher energy efficiency and reduced water flow rate, pipe size, and pumping power, with the ability to operate effectively across a broader range of outdoor wet bulb temperatures and as a backup system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cooling systems operate under reduced load conditions, then cooling output is reduced, but energy consumption remains high due to minimum flow constraints and compressor power requirements
Solution Approach 1:
The system divides the cooling load into two separate circuits, each capable of independent operation. This allows the system to match compressor output more precisely to actual cooling demand, avoiding the minimum flow constraints that plague single-circuit conventional systems. Each circuit can be optimized for its specific load range.
Solution Approach 2:
The system employs variable frequency drives on both refrigerant pumps and compressor motors, enabling continuous adjustment of flow rates and speeds. This dynamic control allows the system to operate efficiently across the full loading spectrum, eliminating the fixed minimum flow constraints of conventional systems.
2Loss of energy
If water flow rate is reduced to save energy, then pumping power decreases, but heat transfer efficiency deteriorates
Solution Approach 1:
The water flow path is segmented into two separate circuits with independent flow control. This allows each circuit to operate at its optimal flow rate for the given heat load, maximizing heat transfer efficiency while minimizing pumping power. The counter-flow arrangement further enhances thermal efficiency at reduced flow rates.
Solution Approach 2:
The system utilizes a counter-flow heat exchanger arrangement where water and refrigerant flow in opposite directions. This hydraulic configuration maximizes the temperature gradient along the entire heat transfer surface, maintaining high heat transfer efficiency even at reduced water flow rates.
3Use of energy by moving object
If compressor speed is reduced to match low cooling demand, then power consumption decreases, but vapor compression stability becomes difficult to maintain
Solution Approach 1:
The compression function is segmented into two independent compressors, each serving its own refrigerant circuit. This allows each compressor to operate within its stable efficiency range even when total system demand is low, avoiding the vapor stability problems that occur when a single compressor is overloaded or operated at extremely low speeds.
Solution Approach 2:
Variable frequency drives enable continuous speed adjustment of each compressor independently. This dynamic control allows each compressor to maintain optimal operating conditions across a wide range of loading conditions, preserving vapor compression stability while minimizing power consumption.
4Ease of manufacture
If pipe size is reduced to lower material costs, then installation cost decreases, but pressure drop increases reducing system efficiency
Solution Approach 1:
The refrigerant and water distribution systems are segmented into two separate circuits. This allows each circuit to use smaller diameter pipes optimized for its specific flow rate, reducing material costs and installation complexity while maintaining acceptable pressure drops through proper pipe sizing for the reduced flow conditions.
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
The system achieves significant energy efficiency improvements and reduced water consumption by optimizing water flow and refrigerant handling, enabling efficient operation under high heat rejection and high sensible heat ratio conditions, such as in data centers and other applications.
Implementation Method 1
two circuits, each of which has a refrigerant pump loop and a water (or glycol) loop to condense the refrigerant
Implementation Method 2
The water flow of the two circuits is in a series, counter-flow arrangement
Data Source
AI summary
The cooling systems and methods of the present disclosure relate to cooling electronic equipment in data centers or any other applications that have high heat rejection temperature and high sensible heat ratio.