Multi-Capacity Heat Pump Unit Selection to Reduce Compressor Cycling
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Solution Overview
Problem
Air-conditioning systems with heat pump apparatuses face reliability issues due to frequent on-off cycles of compressors, leading to reduced lifespan and discomfort, especially during intermediate seasons with lower heat source loads, as existing technologies do not effectively manage compressor operation based on varying capacities.
Innovation Solution
An air-conditioning system with an air handling unit and multiple outdoor heat pump units of different capacities, where a unit number control system selects and operates the outdoor units with the lowest capacity to minimize compressor start-ups and optimize operating frequencies, reducing the frequency of on-off cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single heat pump apparatus is used to meet varying heat source loads, then the system structure is simple, but the compressor must undergo frequent on-off cycles during low-load conditions, reducing reliability and lifespan
Solution Approach 1:
The system divides a single heat pump function into multiple independent heat pump apparatuses (first and second heat pump apparatuses), each with its own compressor. This segmentation allows the system to operate one or both apparatuses depending on load conditions, avoiding frequent on-off cycles of a single compressor and thereby improving reliability while maintaining manageable system complexity.
2Productivity
If the compressor operates at minimum frequency to meet low required capacity, then the system can respond to low heat source loads, but the on-off cycles cause discomfort and reduce system life
Solution Approach 1:
By segmenting the heat pump system into multiple apparatuses, the control unit can selectively operate only the necessary number of apparatuses based on heat source load. During low-load conditions, only one apparatus operates continuously at optimal frequency, avoiding the on-off cycling that would otherwise occur with a single apparatus operating at minimum frequency, thus extending system life while maintaining productivity.
Solution Approach 2:
The system dynamically adjusts the number of operating heat pump apparatuses based on the heat source load. The control unit monitors the required capacity and switches between operating one or two apparatuses, allowing the system to adapt to varying load conditions without subjecting compressors to frequent start-stop cycles, thereby maintaining both productivity and durability.
3Reliability
If multiple heat pump apparatuses are used to cover a range from low to high required capacity, then the system can avoid on-off cycles and improve reliability, but the system complexity and control difficulty increase
Solution Approach 1:
The system uses segmentation into two heat pump apparatuses with a clear control strategy: the control unit determines whether to operate one or both apparatuses based on heat source load. This segmented approach improves reliability by eliminating on-off cycles while keeping control complexity manageable through a straightforward decision-making process that compares required capacity against the capabilities of individual apparatuses.
Solution Approach 2:
The control unit continuously monitors the heat source load and adjusts the number of operating apparatuses accordingly. This feedback mechanism allows the system to maintain high reliability by avoiding on-off cycles while managing complexity through automated load-based control, where the control unit seamlessly switches between operating one or two apparatuses based on real-time 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 extends the life of compressors and improves system reliability by reducing the number of compressor start-ups and maintaining consistent temperatures, even during low-load conditions, thereby enhancing the overall performance and efficiency of the air-conditioning system.
Implementation Method 1
at least one heat exchange coil configured to exchange heat between air flowing from the outside of the building to the inside of the building and refrigerant
Implementation Method 2
a plurality of outdoor units each including a compressor
Implementation Method 3
each connected to the at least one heat exchange coil with a refrigerant pipe to each form an independent heat pump apparatus
Data Source
Figure 1
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AI summary
An air-conditioning system includes an air handling unit including an air exhaust fan forming a flow of air from an inside of a building toward an outside of the building, an air supply fan forming a flow of air from the outside of the building toward the inside of the building, and at least one heat exchange coil exchanging heat between air flowing from the outside of the building to the inside of the building and refrigerant, a plurality of outdoor units each including a compressor, a pressure reducing device, and an outdoor heat exchanger, and each connected to the at least one heat exchange coil with a refrigerant pipe to each form an independent heat pump apparatus, and a unit number control unit performing unit number control of selecting one of the plurality of outdoor units to be operated and determining an operating frequency of the compressor included in the one of the plurality of outdoor units to be operated to meet a capacity required of the air handling unit corresponding to a heat source load. The plurality of outdoor units include outdoor units different in basic capacity. The unit number control unit preferentially identifies at least one of the plurality of outdoor units lowest in the basic capacity, and selects the one of the plurality of outdoor units from the identified at least one of the plurality of outdoor units.