Brine Loop Temperature-Difference Control for High-COP Air Conditioning
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Solution Overview
Problem
Air-conditioning apparatuses using refrigeration cycles with heat transport via a heat medium, such as water or brine, exhibit lower performance compared to direct expansion air conditioners, and there is a need to enhance system COP while minimizing product cost and complexity, including finer temperature control and actuator control optimization.
Innovation Solution
The air-conditioning apparatus controls the temperature difference between the secondary-side heat transfer medium before and after the use side or intermediate heat exchanger, with this difference being greater during heating operations than cooling operations, allowing for adequate actuator control and high COP operation by managing the compressor, expansion device, and pump operations based on temperature and pressure readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If heat is exchanged via a heat medium (water, brine) between refrigerant and indoor air, then refrigerant leakage risk is eliminated indoors, but air conditioning performance is lower than direct expansion air conditioners
Solution Approach 1:
The patent changes the temperature parameter of the heat medium by controlling the temperature difference between inlet and outlet of the heat exchanger. By adjusting the temperature difference to be 10°C or larger, the system achieves both safety (no refrigerant indoors) and improved performance (higher COP) through optimized heat exchange parameters
2Volume of stationary object
If the temperature difference between inlet and outlet of water heat exchanger is increased to 10°C or larger, then the size of air-conditioning unit is reduced and transport energy is reduced, but control complexity increases
Solution Approach 1:
The patent applies parameter changes by setting specific temperature difference values (10°C or larger) as control targets. This simplifies the control strategy to a clear parameter-based approach, where the controller adjusts the pump or valve to maintain the target temperature difference, reducing control complexity while achieving compact size and energy efficiency
Solution Approach 2:
The patent implements feedback control by measuring the actual temperature difference between inlet and outlet of the heat exchanger and comparing it with the target value. The controller adjusts the heat medium flow rate based on this feedback to maintain optimal temperature difference, enabling automated control that simplifies operation while achieving the desired compact design
3Loss of energy
If system COP is enhanced by improving refrigeration cycle performance and reducing heat medium driving power, then energy efficiency improves, but control optimization becomes more complex
Solution Approach 1:
The patent optimizes system energy efficiency through parameter changes by controlling the temperature difference parameter of the heat medium. By setting the temperature difference to 10°C or larger, the system achieves better COP without requiring complex multi-parameter optimization, as the temperature difference serves as a key control parameter that directly impacts both energy efficiency and system performance
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 enables high COP operation by optimizing actuator control and reducing driving power, thereby enhancing system performance and reducing costs by simplifying control methods and eliminating the need for additional instruments like wattmeters.
Implementation Method 1
a refrigeration cycle is constituted by connecting a compressor, a heat source side heat exchanger, an expansion valve, and an intermediate heat exchanger in sequence via pipes, and in which a pump, a use side heat exchanger, and the intermediate heat exchanger are connected in series, thereby performing heat transport so as to transport cooling energy and heating energy generated in the refrigeration cycle to the use side heat exchanger using a heat medium such as water or brine
Data Source
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AI summary
An air-conditioning apparatus which is capable of achieving enhancement of the system COP while suppressing product cost. An air-conditioning apparatus 100 controls the difference between the temperatures of brine at a position before and at a position after an indoor heat exchanger 12 or at a position before and at a position after an intermediate heat exchanger 5 to be a preset target value and to be larger at the time of a heating operation than at the time of a cooling operation.