Heat Pump Refrigerant Injection for Compressor Discharge Temperature Control
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Solution Overview
Problem
Air-conditioning systems using R32 as a refrigerant face issues with excessively high discharge temperatures during heating operations, leading to refrigerant and oil deterioration, and existing systems lack effective methods for controlling discharge temperatures across various operation modes, especially in mixed cooling and heating operations.
Innovation Solution
The air-conditioning apparatus incorporates a refrigerant circuit with a low-pressure shell compressor, refrigerant flow switching devices, heat exchangers, expansion devices, and a controller to manage refrigerant flow, allowing for adjustable injection of refrigerant into the compressor's compression chamber to regulate discharge temperature, ensuring it remains within safe limits regardless of operation mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If R32 is used as a refrigerant during heating operation when outdoor air temperature is low, then cooling and heating operation is enabled, but discharge temperature of compressor becomes excessively high which deteriorates refrigerant and refrigerating machine oil
Solution Approach 1:
The system performs preliminary cooling of the refrigerant before it enters the compressor by introducing refrigerant from the evaporator outlet to cool the suction gas. This preliminary action prevents excessively high discharge temperatures while maintaining the ability to perform both cooling and heating operations with R32 refrigerant.
Solution Approach 2:
The invention introduces an intermediary cooling mechanism where refrigerant from the evaporator outlet serves as a cooling medium for the compressor suction gas. This intermediary refrigerant flow acts as a mediator to reduce the temperature of the gas entering the compressor, thereby preventing high discharge temperatures without compromising system versatility.
2Object-affected harmful factors
If liquid refrigerant is injected from high-pressure liquid pipe into compressor to reduce discharge temperature, then discharge temperature is reduced, but the system does not support circulation channel reversal between cooling and heating operations
Solution Approach 1:
The system achieves multi-functionality by using a single refrigerant injection mechanism that serves both cooling and heating operations. The injection port and control valve are configured to work effectively in both operation modes, eliminating the need for separate systems for each mode while maintaining discharge temperature control.
Solution Approach 2:
The system dynamically adapts the refrigerant injection mechanism to different operation modes through a control valve that adjusts refrigerant flow based on whether the system is in cooling or heating mode. This dynamic control enables the same physical structure to effectively support circulation channel reversal while maintaining discharge temperature control.
3Loss of energy
If expansion device is installed in relay unit or indoor unit away from outdoor unit, then conveyance power of heat medium is reduced, but discharge temperature control during heating operation becomes difficult
Solution Approach 1:
The invention extracts the discharge temperature control function from the distant expansion device location and implements it locally at the compressor through a dedicated injection port and control valve. This separation allows the expansion device to remain in the relay unit or indoor unit for energy efficiency, while temperature control is handled independently at the compressor location.
Solution Approach 2:
The invention introduces an intermediary control mechanism at the compressor that independently manages discharge temperature without requiring the expansion device to be located near the compressor. This intermediary control system uses a control valve and injection port to regulate refrigerant temperature locally, decoupling temperature control from expansion device location.
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 effectively prevents refrigerant and oil deterioration by maintaining discharge temperatures below harmful levels, enabling safe and efficient operation across cooling and heating modes, even when using R32 as the refrigerant.
Implementation Method 1
the second heat exchanger serves as an evaporator due to a low-pressure refrigerant being flowed into part of or whole of the second heat exchanger
Implementation Method 2
the first heat exchanger serves as a condenser due to a high-pressure refrigerant being flowed into the first heat exchanger
Implementation Method 3
an expansion device, such as an electronic expansion valve, which decompresses a refrigerant
Data Source
AI summary
A heat pump hot-water supply apparatus controls a second expansion device during a heating operation so as to adjust the amount of refrigerant flowing through an injection pipe, and controls a third expansion device during a cooling operation so as to adjust the amount of refrigerant flowing through the injection pipe.