Compressor Cycling Control With Soft Loading at Low Loads
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Solution Overview
Problem
Variable flow heating and cooling systems experience energy inefficiency and excessive wear due to rapid compressor cycling at low loads, leading to potential freezing issues and system damage.
Innovation Solution
Implementing a control system with temperature sensors and a controller that introduces a delay period and soft loading periods to manage compressor start and stop operations, based on operational parameters such as temperature readings from multiple locations within the system, to reduce unnecessary cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the compressor is controlled using traditional temperature differential methods in variable flow systems, then the cooling load is met, but rapid cycling occurs causing energy inefficiency and excessive wear
Solution Approach 1:
The control system performs preliminary actions by introducing a delay period before allowing compressor restart and implementing a soft loading period with gradual capacity increase. These preliminary measures prevent rapid cycling by ensuring the compressor only restarts after a minimum time interval and ramps up capacity gradually rather than immediately, thereby reducing wear and energy inefficiency while maintaining cooling load satisfaction
2Productivity
If the compressor is controlled using traditional temperature differential methods in variable flow systems, then the cooling load is met, but rapid cycling occurs causing excessive compressor wear
Solution Approach 1:
The control system implements preliminary protective actions through a delay period that prevents immediate restart after shutdown and a soft loading period that gradually increases compressor capacity. This preliminary ramp-up approach reduces thermal and mechanical stress on the compressor during startup, thereby reducing wear and improving reliability while still meeting the cooling load requirement
3Power
If the compressor operates at full capacity in variable flow systems at low loads, then the cooling capacity is sufficient, but fluid temperature drops excessively causing freezing
Solution Approach 1:
The control system dynamically adjusts the compressor capacity based on actual system conditions rather than operating at fixed full capacity. During low-load conditions, the compressor capacity is reduced proportionally to match the actual cooling demand, preventing excessive cooling and fluid freezing while maintaining sufficient cooling capacity when needed. This dynamic adjustment is implemented through the soft loading period that gradually ramps capacity
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 minimizes energy inefficiency and compressor wear by optimizing compressor operation at low loads, preventing freezing, and extending system lifespan.
Implementation Method 1
a chiller which includes a heat exchanger and a compressor
Implementation Method 2
the compressor in the chiller removes more heat from the system than is added in the heat exchangers
Implementation Method 3
a compressor in a cooler has a minimum threshold load
Implementation Method 4
variable flow (VF) systems cycle fluid through heating or cooling systems
Data Source
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AI summary
Systems and methods for preventing excessive restarting of compressors (12) in variable primary flow systems operating at low loads, with system embodiments including temperature sensors both upstream and downstream from a heat exchanger (14), using the sensor downstream from the heat exchanger to determine when to stop a compressor and the sensor upstream from the heat exchanger to determine when to start the compressor. Methods may include a delay period between restarting operations of the compressor, or use a soft loading period in which the compressor is operated at a low level to reduce the frequency of starts and stops.