Refrigerant circuit system and control method
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Solution Overview
Problem
Existing refrigerant circuit systems for water heaters lack an efficient control method to maintain a predetermined outlet temperature of supply water when the inlet temperature varies, affecting the operation of both transient and circulation-type systems.
Innovation Solution
A refrigerant circuit system with a control device that switches the operation of an injection circuit based on the temperature difference between the inlet and outlet of the use-side heat exchanger, using a third expansion valve and intermediate heat exchanger to optimize the refrigerant flow and compressor operation, ensuring efficient temperature regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the injection circuit operates continuously to improve cooling capacity and COP, then the coefficient of performance improves, but the system cannot efficiently adapt to varying inlet temperatures in both transient and circulation-type water heater systems
Solution Approach 1:
The injection circuit's operation is made dynamic by switching between operation and non-operation states based on real-time temperature difference detection. The control device monitors the difference between use-side heat exchanger inlet and outlet temperatures, and adjusts the injection circuit accordingly, allowing the system to adapt efficiently to varying operating conditions in both transient and circulation-type systems
2Manufacturing precision
If the system maintains a constant outlet temperature for supply water, then the temperature regulation efficiency improves, but the control complexity increases when inlet temperature varies
Solution Approach 1:
The control device implements feedback control by continuously detecting the temperature difference between the use-side heat exchanger inlet and outlet. Based on this feedback, the system automatically switches the injection circuit operation state, maintaining precise outlet temperature control without requiring complex control algorithms or additional control components
3Device complexity
If the third expansion valve is completely closed to simplify control, then the device complexity reduces, but the system cannot optimize refrigerant flow under all operating conditions
Solution Approach 1:
The third expansion valve's opening state is made dynamic, switching between completely closed and a predetermined opening level based on operating conditions. This dynamic adjustment allows the system to optimize refrigerant flow under different operating conditions while maintaining simple control logic through binary state transitions
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
The system efficiently operates by adjusting the injection circuit's operation to maintain a constant outlet temperature, improving the coefficient of performance (COP) and reducing refrigerant pressure loss, thus maintaining efficient operation across varying inlet temperatures.
Implementation Method 1
a use-side heat exchanger which condenses the refrigerant compressed by the compressor
Implementation Method 2
a use-side heat exchanger which condenses the refrigerant compressed by the compressor
Implementation Method 3
a first expansion valve which depressurizes the refrigerant flowing out from the use-side heat exchanger
Implementation Method 4
a second expansion valve which depressurizes the refrigerant flowing out from the receiver
Implementation Method 5
a heat-source-side heat exchanger which evaporates the refrigerant depressurized by the second expansion valve
Implementation Method 6
an intermediate heat exchanger which performs heat exchange between a refrigerant passing through the third expansion valve and a refrigerant passing through the mainstream circuit
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A refrigerant circuit system (1) includes a mainstream circuit which connects a plurality of compressors (10A, 10B), a use-side heat exchanger (11), a first expansion valve (12), a receiver (13), a second expansion valve (14) which depressurizes the refrigerant flowing out from the receiver (13), and a heat-source-side heat exchanger (15), an injection circuit which branches some of the refrigerant flowing out from the receiver (13) and supplies the branched refrigerant to a suction side of a predetermined compressor among the plurality of compressors (10A, 10B), and a control device which switches between operation and non-operation of the injection circuit on the basis of a difference between an inlet temperature on an inlet side of the use-side heat exchanger (11) of a use-side medium that receives a supply of heat by the use-side heat exchanger (11) and an outlet temperature on an outlet side of the use-side heat exchanger.