Multi-Compressor Heat Pump Control for Low-Load Cycling
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Solution Overview
Problem
Existing air-conditioning systems face challenges with high operational costs and inefficiencies due to the use of multiple compressors, which lead to frequent on/off cycles and reduced compressor lifespan, especially during low load conditions, and there is a need for a system that utilizes refrigerant from a heat pump cycle as a heat source while minimizing these inefficiencies.
Innovation Solution
The air-conditioning system incorporates multiple outdoor units with compressors, pressure-reducing devices, and heat exchangers connected via refrigerant pipes to form independent heat pump cycles, with a number control unit managing the operation of compressors and their frequencies to match air-conditioning load demands within specific efficiency ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single compressor is used in the heat pump cycle, then the device complexity is reduced and cost is lowered, but the compressor enters on/off cycle operation during low load conditions which reduces reliability and shortens compressor lifespan
Solution Approach 1:
The system divides the compression function into multiple independent compressors (first compressor and second compressor) that can operate independently. This segmentation allows the system to maintain continuous operation during low load conditions by switching between compressors, preventing the on/off cycling problem that would occur with a single compressor.
2Reliability
If multiple compressors are provided to prevent on/off cycle operation, then the reliability and operational efficiency are improved, but the device complexity and cost increase due to complicated refrigerant pipes and refrigerant circuit components
Solution Approach 1:
The patent merges the refrigerant circuits of multiple compressors into a shared common refrigerant circuit. The first compressor and second compressor both connect to the same refrigerant pipes, heat exchangers, and expansion valves, allowing them to share infrastructure rather than requiring separate dedicated circuits for each compressor, thereby reducing overall system complexity.
Solution Approach 2:
The refrigerant circuit components (heat exchangers, expansion valves, pipes) are designed to serve multiple compressors simultaneously. Each component can work with either the first compressor or the second compressor, providing multi-functionality and eliminating the need for duplicate components for each compressor.
3Device complexity
If the compressor operates at minimum frequency continuously, then the device complexity is minimized, but the energy efficiency deteriorates due to on/off cycle operation during low air-conditioning loads
Solution Approach 1:
The system dynamically adjusts the number of operating compressors based on the air-conditioning load. The control unit monitors the load and switches between one-compressor mode and two-compressor mode, allowing the system to adapt its configuration to match demand, thereby maintaining high efficiency across varying load conditions without requiring complex variable speed control.
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 configuration reduces the frequency of on/off compressor cycles during low loads, enhances operational efficiency, and allows for a cost-effective solution by utilizing existing outdoor unit designs, thereby extending compressor lifespan and improving energy savings.
Implementation Method 1
a heat exchanger coil is integrally incorporated in a main body casing... during heating operation, hot water is allowed to pass through the heat exchanger coil, and fresh air is allowed to pass through the coil to generate hot air
Implementation Method 2
an air-conditioning system including a heat pump cycle including a compressor
Implementation Method 3
a pressure-reducing device, and an outdoor heat exchanger
Implementation Method 4
an indoor heat exchanger through which the air inside the passage flows
Data Source
AI summary
A low-cost and highly-efficient air-conditioning system including an AHU using refrigerant of a heat pump cycle as a heat source, and capable of reducing an on/off cycle operation of compressors at a time of a low load, the system including: a plurality of outdoor units; an air handling unit; a plurality of independent heat pump cycles formed by connecting the plurality of outdoor units and the air handling unit by refrigerant pipes, each of the plurality of independent heat pump cycles including a compressor, an indoor heat exchanger, an expansion valve, and an outdoor heat exchanger; and a number control unit controlling, to satisfy a capacity demand corresponding to an air-conditioning load, based on a particular frequency range associated with the compressor, in which a certain compressor efficiency or more is obtained, a number of the compressors in operation and operating frequencies of the respective compressors in operation.