Dual-Circuit Cooling With Evaporative Pre-Cooling for 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 climates with high ambient temperatures and high latent loads, due to limitations in refrigerant systems and compressor operations.
Innovation Solution
A dual-circuit cooling system that employs 'free' water evaporation and vapor compression with refrigerant-to-refrigerant heat transfer, eliminating intermediate heat transfer steps and incorporating a microchannel evaporator for efficient cooling, allowing for efficient operation across a wide range of environmental conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cooling systems operate under partial or lightly loaded conditions, then the system continues to run, but energy consumption per ton of cooling increases dramatically
Solution Approach 1:
The cooling system is divided into two separate circuits: a primary refrigerant-based circuit and a secondary evaporative cooling circuit. Each circuit can operate independently or in combination, allowing the system to segment the cooling load and optimize energy consumption at different operating conditions. The secondary circuit handles sensible cooling while the primary circuit handles latent cooling, enabling efficient partial loading operation.
Solution Approach 2:
The system dynamically switches between different cooling modes and circuits based on ambient conditions and cooling load. The control system adjusts the operation of compressors, fans, and evaporative coolers in real-time, allowing the system to adapt to varying load demands and maintain optimal energy efficiency across different operating points.
2Measurement precision
If metering devices are used to control refrigerant flow in evaporators, then tight control of vapor evaporation is achieved, but liquid slugging to the compressor can occur under low loading conditions
Solution Approach 1:
The system extracts the metering function from the refrigerant circuit by introducing a separate evaporative cooling circuit that does not require precise metering. The secondary circuit uses direct evaporation of water to provide cooling, eliminating the risk of liquid slugging to the compressor while still achieving precise temperature control through the combination of both circuits.
Solution Approach 2:
A bypass line with a control valve serves as an intermediary pathway for excess refrigerant, allowing it to bypass the evaporator and return to the compressor without causing liquid slugging. This mediator mechanism protects the compressor while maintaining refrigeration cycle operation under varying load conditions.
3Reliability
If hot gas bypass is used to combat inflexibility problems in refrigerant systems, then slugging and uneven heat distribution are mitigated, but a false load is created and energy is consumed
Solution Approach 1:
The system converts the excess refrigerant that would normally require hot gas bypass into a beneficial resource by using it in the evaporative cooling circuit. The excess refrigerant provides additional cooling capacity in the secondary circuit, transforming what would be a harmful condition (excess refrigerant causing slugging) into a useful function (additional cooling capacity).
Solution Approach 2:
The system changes the operating parameters of the refrigerant circuit by allowing it to operate at higher superheat conditions when the evaporative circuit is active. This parameter change enables the refrigerant system to run more efficiently while the evaporative circuit handles the bulk of the cooling demand, reducing the need for energy-consuming bypass operations.
4Temperature
If air-cooled DX systems are used in high ambient temperature conditions, then cooling is provided, but kw per ton exceeds 1.0 indicating poor energy efficiency
Solution Approach 1:
The system merges two different cooling technologies: refrigerant-based compression cooling and evaporative cooling. The evaporative coolers are positioned to pre-cool the ambient air before it enters the air-cooled condensers, combining the benefits of both systems to maintain high cooling capacity while significantly reducing the energy consumption of the compressors in high ambient temperature 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 dual-circuit cooling system reduces energy consumption and maintenance costs by optimizing cooling performance under both high and low load conditions, and across varying environmental conditions, by leveraging 'free' cooling and refrigerant-to-refrigerant heat transfer for efficient heat management.
Implementation Method 1
an evaporative cooler in thermal communication with the condensing air to cool the condensing air
Implementation Method 2
The expanded liquid absorbs the heat present in the evaporator coil and leaves the coil as a super-heated vapor
Implementation Method 3
a condenser in thermal communication with the cooled condensing air to condense the refrigerant vapor to liquid
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.