Expansion Valve Control for R32 Discharge Temperature Limits
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Solution Overview
Problem
Existing refrigeration/air-conditioning devices using R32 refrigerant face challenges in controlling discharge temperature, leading to increased motor efficiency issues and potential compressor breakdowns, which existing solutions fail to adequately address, especially under changing operation conditions and ambient temperatures.
Innovation Solution
A refrigeration/air-conditioning device with an electronic expansion valve control system that adjusts aperture based on suction gas superheat and discharge temperature, using target value switching and varying mechanisms to maintain optimal operation within utilization limits, avoiding excessive discharge temperature and ensuring stable operation without increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If R32 refrigerant is used to reduce environmental load, then global warming potential and ozone depletion potential are reduced, but discharge temperature increases by 10°C to 20°C compared to R410A
Solution Approach 1:
The control method dynamically adjusts the aperture of the electronic expansion valve based on discharge temperature measurements, changing the refrigerant flow parameters to maintain discharge temperature within safe operating limits while using R32 refrigerant
2Reliability
If discharge temperature is controlled within safe range, then compressor motor reliability is maintained, but control system becomes complicated requiring both rotational speed adjustment and aperture control
Solution Approach 1:
The invention extracts and focuses on controlling only the electronic expansion valve aperture as the primary control mechanism, eliminating the need for complex dual-control systems while maintaining discharge temperature within safe ranges
Solution Approach 2:
The system implements a feedback control mechanism where discharge temperature is measured by a sensor and used to dynamically adjust the electronic expansion valve aperture, maintaining reliable operation without requiring complex multi-parameter control
3Reliability
If electronic expansion valve aperture is controlled to maintain suction gas superheat, then liquid floodback to compressor is prevented, but discharge temperature may still exceed upper-limit value under changing operation conditions
Solution Approach 1:
The control system uses discharge temperature feedback to dynamically adjust the electronic expansion valve aperture, switching from fixed superheat control to adaptive temperature-based control that prevents discharge temperature from exceeding upper limits under varying operating conditions
Solution Approach 2:
The system transitions from static superheat control to dynamic discharge temperature control, where the electronic expansion valve aperture is continuously adjusted based on real-time discharge temperature measurements to adapt to changing operation 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
The system effectively prevents discharge temperature from exceeding utilization limits, maintains compressor motor insulation, and ensures efficient operation by adjusting expansion valve control in response to compressor speed and temperature changes, thereby enhancing reliability and heat exchange performance.
Implementation Method 1
a degree of suction gas superheat SH becomes constant
Implementation Method 2
the discharge temperature Td of the R32 refrigerant is higher by 10°C to 20°C than that of the R410A refrigerant due to its physical properties
Implementation Method 3
a heat source-side heat exchanger, an electronic expansion valve, and a utilization-side heat exchanger
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
In a refrigeration / air-conditioning device including a refrigeration cycle (29), and an expansion valve control means (35), the expansion valve control means (35) includes a target value switching means (36) which adopts the lower one of a target degree of discharge superheat TdSH plus a high pressure saturation temperature and an upper-limit value of the discharge temperature Td as a target value, or compares a target discharge temperature Td obtained by calculation from the rotational speed of a compressor and the high pressure saturation temperature with an upper-limit value and adopts the lower one of the target discharge temperature Td and the upper-limit value as the target discharge temperature Td while performing the control at the predetermined degree of discharge superheat TdSH or the control at the predetermined discharge temperature Td.