Turbo Chiller Capacity Control Under Changing Cooling Water Temperature
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Solution Overview
Problem
Existing heat source systems using turbo chillers face inefficiencies when cooling water temperature changes, as they require extensive data to maintain high efficiency, making it impractical to operate at optimal performance across varying conditions.
Innovation Solution
A turbo chiller system with a turbo compressor driven by an inverter for variable speed, utilizing flow and pressure coefficients at a specific operating point to determine an arithmetic expression for chilling capacity, allowing flexible operation within an adequate capacity range, ensuring high coefficient of performance across changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the relationship between coefficient of performance and load factor is obtained at every conceivable cooling water temperature, then the turbo chiller can be operated at high efficiency under any condition, but the amount of data required becomes enormous and unrealistic
Solution Approach 1:
The patent changes the approach from storing data at every cooling water temperature to using a mathematical model with dimensionless parameters (flow coefficient φ and pressure coefficient ψ). By expressing the relationship between load factor and coefficient of performance through these dimensionless parameters, the system can determine optimal operation points without requiring extensive experimental data for each temperature condition.
Solution Approach 2:
Instead of directly measuring and storing performance data for each cooling water temperature, the patent creates a universal mathematical model that copies the essential relationships through dimensionless parameters. This model can be applied across different operating conditions without requiring separate data sets for each temperature, effectively copying the performance characteristics through a generalized framework.
2Adaptability or versatility
If the turbo chiller operates outside the adequate chilling capacity range, then it can handle varying cooling water temperatures, but the coefficient of performance decreases and energy efficiency is lost
Solution Approach 1:
The patent implements dynamic operation by enabling the turbo compressor to adjust its revolution speed via an inverter. The control system dynamically determines the adequate chilling capacity range based on the current cooling water temperature using the mathematical model, and adjusts the compressor speed to maintain operation within this range. This dynamic adaptation allows the system to maintain high efficiency across varying temperatures rather than operating at fixed parameters.
Solution Approach 2:
The control system uses feedback from the actual cooling water temperature and current operation state to continuously determine the adequate chilling capacity range. The controller compares the current operating point with the calculated adequate range and adjusts the compressor speed accordingly, creating a closed-loop control system that maintains optimal efficiency while adapting to temperature changes.
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
Enables efficient operation of turbo chillers within a predetermined chilling capacity range, achieving high energy savings by maintaining optimal performance even with varying cooling water temperatures, thus effectively managing chilling capacity and energy usage.
Implementation Method 1
a turbo compressor (60) having an impeller (601)
Implementation Method 2
a condenser (62) that condenses refrigerant compressed by the turbo compressor
Implementation Method 3
an expansion valve (65) that expands the condensed refrigerant
Implementation Method 4
an evaporator (66) that evaporates the expanded refrigerant to cool cooled water
Implementation Method 5
a turbo compressor driven by an inverter in a manner that enables variable revolution speeds
Data Source
AI summary
There is provided a turbo chiller that can be operated at high efficiency within an adequate chilling capacity range even when the cooling water temperature changes during the operation. The adequate chilling capacity range is obtained by using a flow coefficient and a pressure coefficient at a specific operating point of a turbo compressor as well as a predetermined coefficient to determine an arithmetic expression representing the relationship between a head and a chilling capacity, using a chilling capacity that can lead to a substantially highest coefficient of performance at a single head to obtain the predetermined coefficient as an optimum coefficient, computing an adequate operation coefficient range having a predetermined range and including the optimum coefficient, and substituting the adequate operation coefficient range and a head at the time of operation into the arithmetic expression.