Relay Bypass Refrigerant Control for Compressor Temperature Limits
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Solution Overview
Problem
Air-conditioning systems using refrigerant R32 experience excessive compressor discharge temperatures, leading to reduced heating capacity and comfort issues, especially in low outside air environments, due to the high enthalpy of refrigerant and increased pressure differences, which existing technologies struggle to manage without stopping the compressor or reducing its capacity.
Innovation Solution
The air-conditioning apparatus incorporates a refrigerant circuit with a relay unit, bypass pipe, and bypass flow rate control device, allowing for controlled refrigerant flow between the heat source and indoor units, ensuring the compressor discharge temperature remains below its heat-resistant limit by adjusting the opening degree of the bypass flow rate control device, even under high enthalpy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If refrigerant injection is performed to enhance heating capacity in heating main operation, then heating capacity is improved, but compressor discharge temperature excessively rises
Solution Approach 1:
The patent introduces an intermediate heat exchanger as a mediator between the compressor discharge and the injection pipe. The high-temperature discharge refrigerant passes through this intermediate heat exchanger where it transfers heat to the suction refrigerant, thereby reducing the discharge temperature before injection while maintaining the heating capacity enhancement effect.
Solution Approach 2:
The patent changes the temperature parameter of the discharge refrigerant by introducing it to an intermediate heat exchanger. The discharge refrigerant temperature is reduced from an excessively high state to an acceptable range through heat exchange with suction refrigerant, allowing the injection to proceed without causing overheating.
2Temperature
If compressor capacity is reduced or compressor is stopped to prevent excessive discharge temperature, then discharge temperature is controlled, but desired heating or cooling capacity cannot be exerted
Solution Approach 1:
The intermediate heat exchanger serves as a mediator that allows the compressor to maintain its full capacity operation while simultaneously reducing the discharge temperature. The heat exchanger absorbs the excess heat from the discharge refrigerant and transfers it to the suction refrigerant, enabling the compressor to run at full power without exceeding temperature limits.
Solution Approach 2:
The patent converts the harmful excessive heat in the discharge refrigerant into a beneficial cooling effect for the suction refrigerant. The high-temperature discharge refrigerant, which would normally cause overheating problems, is instead used to pre-cool the suction refrigerant through the intermediate heat exchanger, thereby eliminating the need to reduce compressor capacity.
3Power
If heat source unit-side flow rate control device controls evaporating pressure in cooling indoor unit during heating main operation, then cooling capacity is secured, but discharge temperature excessively rises under low outside air environment
Solution Approach 1:
The intermediate heat exchanger acts as an additional mediator that works alongside the heat source unit-side flow rate control device. While the flow rate control device manages the evaporating pressure to maintain cooling capacity, the intermediate heat exchanger simultaneously manages the discharge temperature by transferring heat from discharge refrigerant to suction refrigerant, resolving the temperature issue without compromising cooling performance.
4Temperature
If bypass pipe allows refrigerant to flow between heat source unit and indoor unit, then discharge temperature is controlled, but system complexity increases
Solution Approach 1:
The intermediate heat exchanger is designed to serve multiple functions within the refrigerant circuit. It acts as both a heat exchange device for temperature control and as part of the refrigerant flow path. This multi-functionality reduces the need for separate dedicated temperature control components, thereby minimizing the increase in system complexity while achieving effective discharge temperature control.
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 maintains a constant and comfortable temperature in the air-conditioned space while preventing compressor shutdown, ensuring reliable operation and maintaining desired heating and cooling capacities without reducing compressor capacity.
Implementation Method 1
a bypass pipe configured to cause a part of the refrigerant, which is discharged from the compressor and flows into the relay unit, to flow between the heat source unit-side heat exchanger and the indoor unit-side heat exchanger
Implementation Method 2
a heat source unit-side heat exchanger configured to exchange heat between an outside air and refrigerant; an indoor unit-side heat exchanger configured to exchange heat between an air to be conditioned and the refrigerant
Implementation Method 3
a phenomenon that the refrigerant is evaporated or condensed in the indoor unit-side heat exchanger by receiving or transferring heat from or to air in an air-conditioned space
Implementation Method 4
a heat source unit including a compressor
Data Source
AI summary
Provided is an air-conditioning apparatus capable of performing a cooling and heating mixed operation, including: a heat source unit including a compressor; a plurality of indoor units; a relay unit; a first relay unit-side bypass pipe configured to cause a part of refrigerant, which is discharged from the compressor and flows into the relay unit, to flow between a heat source unit-side heat exchanger and an indoor unit-side heat exchanger; a second relay unit-side flow rate control device provided to the first relay unit-side bypass pipe; and a controller configured to control an opening degree of the second relay unit-side flow rate control device so that, in an operation in which the heat source unit-side heat exchanger functions as an evaporator, a discharge temperature of a discharge refrigerant discharged from the compressor is equal to or lower than a heat-resistant temperature of the compressor.