Heat Pump Pressure Control for Low-Refrigerant Heating
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Solution Overview
Problem
Conventional heat pump cycles face challenges in maintaining compressor durability and heating capacity at low outside air temperatures, as refrigerant flow rate reductions can lead to compressor damage and inadequate heating performance.
Innovation Solution
A heat pump cycle with a refrigerant shortage determination unit and compressor control unit that adjusts refrigerant discharge capacity and blower operation to prevent compressor damage while ensuring heating capability at low temperatures, by setting reference pressures and controlling blower capacity to prevent erroneous refrigerant shortage detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the compressor stops at low outside air temperature to protect against refrigerant shortage, then compressor durability is improved, but heating capacity is lost
Solution Approach 1:
The patent changes the pressure threshold parameter for refrigerant shortage detection based on outside air temperature. At low temperatures (below 0°C), a higher pressure threshold is used compared to normal temperatures, allowing the compressor to operate in refrigerant shortage conditions that would normally trigger protection shutdown, thereby maintaining heating capacity while still protecting compressor durability through temperature-compensated detection.
2Reliability
If the refrigerant flow rate is reduced at low outside air temperature, then compressor protection is improved, but heating performance deteriorates
Solution Approach 1:
The system dynamically adjusts the pressure threshold parameter according to outside air temperature. When the temperature is low, the threshold is raised, allowing higher refrigerant flow rates that maintain heating performance while still providing compressor protection adapted to the operating conditions.
3Device complexity
If a fixed pressure threshold is used for refrigerant shortage detection, then detection simplicity is improved, but detection accuracy deteriorates at low temperatures
Solution Approach 1:
The patent implements temperature-dependent pressure thresholds, where the detection system switches between different threshold values based on outside air temperature. This maintains relatively simple detection logic while significantly improving accuracy by accounting for the temperature effect on refrigerant pressure characteristics.
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 maintains compressor durability and provides heating capacity at low outside air temperatures by reducing refrigerant discharge and increasing blower capacity, preventing compressor damage and ensuring efficient heating.
Implementation Method 1
a compressor (11) that compresses and discharges a refrigerant
Implementation Method 2
a heating heat exchanger (12) that heats fluid by exchanging heat between a high pressure refrigerant discharged from the compressor and the fluid to be heated
Implementation Method 3
a decompression unit (13) that decompresses the refrigerant flowing out from the heating heat exchanger
Implementation Method 4
an outdoor heat exchanger (16) that evaporates a low pressure refrigerant decompressed by the decompression unit by exchanging heat between the low pressure refrigerant and an outside air
Data Source
Figure 1~2
Figure 3
AI summary
A refrigerant shortage determination unit (S2, S3, S6, S8, S9) determines that refrigerant is in shortage state if a high pressure side refrigerant pressure (Pd) between a discharge port of a compressor (11) and an inlet of a decompression unit (13) is lower than a predetermined first reference pressure (KPd1) when an outside air temperature (Tam) is equal to or higher than a predetermined reference outside air temperature (KTam), and determines that refrigerant is in shortage state if the high pressure side refrigerant pressure (Pd) is lower than a predetermined second reference pressure (KPd2) in a state where the compressor (11) is operated when the outside air temperature (Tam) is lower than the reference outside air temperature (KTam). A compressor control unit (S4) reduces a refrigerant discharge capacity of the compressor (11) when the refrigerant shortage determination unit determines that refrigerant is in the shortage state.