Chiller Compressor Control Across Free Cooling Temperature Ranges
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Solution Overview
Problem
Chilled liquid systems using centrifugal compressors often fail to operate efficiently due to limited environmental conditions that allow for energy savings, as they typically shut down the compressor during free cooling conditions, resulting in reduced cooling capacity and energy inefficiencies.
Innovation Solution
A method of continuously operating the compressor in various temperature ranges by comparing condenser and evaporator temperatures, utilizing a variable speed drive for rotational speed control and magnetic bearings, ensuring the compressor operates even when the evaporator temperature is greater, equal to, or less than the condenser temperature by a predetermined amount, thereby maintaining chiller load capacity and energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the compressor is shut down during free cooling conditions, then energy savings are achieved, but the range of environmental conditions for energy-efficient operation is limited
Solution Approach 1:
The system dynamically adjusts compressor operation based on real-time temperature comparisons between condenser and evaporator. The control system continuously monitors temperatures and adjusts compressor status accordingly, enabling the system to adapt to varying environmental conditions while maintaining energy efficiency across a broader range of operating scenarios.
Solution Approach 2:
The invention changes the operational parameters by comparing condenser and evaporator temperatures to determine compressor operation. By using temperature differential as the control parameter rather than fixed environmental conditions, the system expands the range of conditions under which energy-efficient operation can be achieved.
2Loss of energy
If the compressor is shut down during free cooling conditions, then energy costs are reduced, but chiller load capacity is reduced
Solution Approach 1:
The system dynamically controls compressor operation based on temperature conditions, allowing the compressor to remain operational when temperature differentials indicate favorable free cooling conditions. This dynamic approach maintains chiller load capacity while capturing energy savings opportunities that would otherwise be unavailable.
Solution Approach 2:
The control system uses feedback from temperature sensors in both the condenser and evaporator to continuously monitor system conditions. This feedback mechanism enables real-time decision-making about compressor operation, ensuring that energy savings are achieved without compromising the ability to meet cooling demands.
3Productivity
If the compressor operates continuously, then chiller load capacity is maintained, but energy savings are reduced
Solution Approach 1:
The invention changes the control parameter from fixed environmental conditions to temperature differential between condenser and evaporator. This parameter change enables the system to maintain continuous compressor operation while still achieving energy savings when the temperature differential indicates favorable conditions for free cooling.
Solution Approach 2:
Continuous temperature monitoring and feedback control enable the system to make informed decisions about compressor operation. The feedback mechanism allows the system to maintain load capacity while capturing energy savings by adjusting operation based on real-time 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
This approach significantly expands the range of environmental conditions for energy-efficient operation, increasing chiller load capacity while minimizing energy costs by maintaining compressor operation across a broader temperature range, achieving nearly twice the design cooling capacity compared to conventional systems during free cooling conditions.
Implementation Method 1
a condenser for thermal communication with the refrigerant and in fluid communication with the evaporator
Implementation Method 2
an evaporator in thermal communication with the refrigerant and in fluid communication with the condenser
Implementation Method 3
some chillers can operate as a thermal siphon. Low-temperature condenser water condenses refrigerant, which is either drained by gravity or pumped into the evaporator
Data Source
AI summary
A method of operating a chiller having a closed refrigerant loop including a compressor, a condenser and an evaporator. The refrigerant used in the loop defining a pressure-enthalpy curve representative of different phases (vapor, liquid and vapor, and liquid) of the refrigerant at different combinations of pressure and enthalpy. The loop defining a process cycle (compression, condensation, expansion, and evaporation) of the refrigerant during operation of the loop relative to the pressure-enthalpy curve of the refrigerant. The method including continuously operating the compressor when a segment of the process cycle corresponds to the refrigerant being in the liquid phase.