Method for operating a chiller
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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, to maintain a compressor operational state even during free cooling conditions, thereby increasing the range of operational temperatures and load capacity while minimizing energy costs.
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 savings 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 modulates compressor activity to maintain efficiency across varying environmental conditions, transitioning from static on/off control to dynamic adaptive control.
Solution Approach 2:
The invention changes the operational parameters by allowing compressor operation across a broader temperature differential range. By modifying the control logic to permit compressor operation when evaporator exit temperature is below condenser entering temperature, the system expands the environmental conditions under which energy savings can be achieved.
2Adaptability or versatility
If the compressor is continuously operated, then the range of operational temperatures and load capacity are increased, but energy consumption increases
Solution Approach 1:
The system implements feedback control by continuously comparing condenser and evaporator temperatures and using this information to make real-time decisions about compressor operation. This closed-loop control ensures the compressor operates only when thermodynamically beneficial, preventing unnecessary energy consumption while maintaining expanded operational range.
Solution Approach 2:
The control system applies partial action by selectively operating the compressor only during specific temperature conditions rather than continuous operation. This partial operation strategy maintains the expanded temperature range capability while avoiding excessive energy consumption during conditions where compression would be inefficient.
3Loss of energy
If the compressor is shut down during free cooling, then energy costs are reduced, but cooling capacity is reduced
Solution Approach 1:
The system dynamically balances energy consumption and cooling capacity by continuously monitoring temperature differentials and adjusting compressor operation accordingly. This dynamic approach allows the system to maintain adequate cooling capacity during periods when energy savings are achievable, rather than using fixed on/off thresholds.
Solution Approach 2:
The control system takes preliminary action by pre-cooling the evaporator water when conditions are favorable, storing cooling capacity in the chilled water loop. This allows the system to meet future cooling demands without continuous compressor operation, effectively decoupling immediate energy consumption from future cooling capacity requirements.
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 operational temperatures, enhances energy savings, and increases chiller load capacity by maintaining compressor operation across a broader range of conditions, achieving nearly twice the design cooling capacity compared to conventional systems during free cooling conditions.
Implementation Method 1
a condenser (for thermal communication with refrigerant in the condenser)
Implementation Method 2
an evaporator (for thermal communication with refrigerant in the evaporator)
Implementation Method 3
the refrigerant used in the loop defining a pressure-enthalpy curve representative of different phases (vapor, liquid and vapor, and liquid) of the refrigerant
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.