Bypass Refrigerant Control in Air Conditioners for Discharge Temperature
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Solution Overview
Problem
In air-conditioning systems using refrigerant cycles, the compressor discharge temperature rises excessively when the ratio of operating cooling indoor units is high under low outside air conditions, particularly with R32 refrigerant, leading to reduced heating capacity and discomfort, as existing systems struggle to maintain the desired temperature without stopping the compressor.
Innovation Solution
The air-conditioning apparatus employs a control mechanism for the bypass flow rate control device to manage the compressor discharge temperature by adjusting the opening degree, ensuring it remains below the heat-resistant temperature, even under high enthalpy conditions, thereby maintaining comfort and consistent air-conditioned space temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the heating capacity is enhanced by injecting refrigerant into the compressor during compression stroke, then the heating capacity is improved, but the compressor discharge temperature rises excessively
Solution Approach 1:
A subcooling heat exchanger is introduced as an intermediary component between the condenser and the injection point. This heat exchanger subcools the liquid refrigerant before injection, lowering its temperature and enthalpy. The subcooled refrigerant then mixes with the suction refrigerant in the compressor, effectively reducing the discharge temperature while maintaining the heating capacity enhancement benefit
Solution Approach 2:
The invention changes the temperature parameter of the injected refrigerant by subcooling it before injection. By lowering the temperature and enthalpy of the injected refrigerant through the subcooling heat exchanger, the mixing process in the compressor results in a lower discharge temperature, resolving the contradiction between heating capacity enhancement and discharge temperature control
2Power
If the ratio of cooling indoor units is increased under low outside air conditions, then the cooling capacity is improved, but the compressor discharge temperature rises excessively
Solution Approach 1:
The subcooling heat exchanger acts as an intermediary that processes the liquid refrigerant before it enters the compressor. By subcooling the refrigerant, it reduces the enthalpy of the injected portion, which directly impacts the discharge temperature calculation, allowing higher cooling capacity operation without excessive discharge temperature
Solution Approach 2:
The invention modifies the enthalpy parameter of the injected refrigerant through subcooling. This parameter change allows the system to operate with a higher proportion of cooling indoor units while keeping the discharge temperature within acceptable limits, as the lower enthalpy of injected refrigerant reduces the overall discharge temperature
3Temperature
If the opening degree of the bypass flow rate control device is increased to suppress discharge temperature, then the discharge temperature is reduced, but the heating capacity is reduced
Solution Approach 1:
The subcooling heat exchanger serves as an intermediary that pre-cools the injected refrigerant, replacing the need to rely solely on bypass control for discharge temperature management. This allows the bypass flow rate control device to maintain a larger opening degree (preserving heating capacity) while the subcooling heat exchanger handles the discharge temperature suppression function
Solution Approach 2:
By changing the temperature parameter of the injected refrigerant through subcooling, the system can maintain a larger bypass opening degree (which preserves heating capacity) while still achieving discharge temperature suppression through the combined effect of subcooling and bypass modulation
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 solution effectively suppresses the compressor discharge temperature, ensuring continuous operation and maintaining desired comfort levels without reducing the compressor's operating capacity, thus providing a reliable air-conditioning system capable of simultaneous cooling and heating.
Implementation Method 1
the control of the opening degree of the bypass flow rate control device can suppress the discharge temperature of the compressor to be equal to or lower than a heat-resistant temperature of the compressor without stopping the operation even under an operating condition in which the discharge temperature excessively rises
Implementation Method 2
in the operation in which the heat source unit-side heat exchanger functions as the evaporator
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 side unit (heat source unit, outdoor unit) including a compressor
Implementation Method 5
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
Data Source
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AI summary
Provided is an air-conditioning apparatus capable of performing a cooling and heating mixed operation, including: a heat source unit (100) including a compressor (110); a plurality of indoor units (200); a relay unit (300); a first relay unit-side bypass pipe (342) configured to cause a part of refrigerant, which is discharged from the compressor (110) and flows into the relay unit (300), to flow between a heat source unit-side heat exchanger (131) and an indoor unit-side heat exchanger (210); a second relay unit-side flow rate control device (343) provided to the first relay unit-side bypass pipe (342); and a controller (400) configured to control an opening degree of the second relay unit-side flow rate control device (343) so that, in an operation in which the heat source unit-side heat exchanger (131) functions as an evaporator, a discharge temperature of a discharge refrigerant discharged from the compressor (110) is equal to or lower than a heat-resistant temperature of the compressor (110).