Compressor Suction Injection for Low-Load Refrigeration Capacity Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing air-conditioning apparatuses experience reduced operation efficiency due to frequent repetition of compressor stopping and starting, especially when thermal loads are low, as they struggle to adjust capacity without compromising compressor reliability.
Innovation Solution
A refrigeration cycle apparatus with an injection pipe and a second expansion valve, controlled by a controller to manage compressor rotation speed and valve opening, reduces refrigerant flow through the evaporator, thereby adjusting capacity without changing compressor speed, thereby minimizing compressor stop-start cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the rotation speed of the compressor is reduced to match low thermal load, then the capacity of the refrigeration cycle apparatus is adjusted, but the compressor cannot be driven at excessively low speeds without insufficient refrigerating machine oil supply to the slide portion, reducing reliability
Solution Approach 1:
The system performs preliminary heating of the refrigerant in the refrigerant heater before injection into the compressor. This pre-heating action ensures that the injected refrigerant does not cause excessive cooling that would lead to insufficient oil supply, thereby maintaining compressor reliability while enabling low-speed operation to match low thermal load conditions.
Solution Approach 2:
The refrigerant heater acts as an intermediary device between the refrigerant circulation system and the compressor. It mediates the temperature of the refrigerant before injection, preventing direct negative effects of cold refrigerant on compressor oil supply while still allowing capacity reduction through injection. This intermediary function resolves the contradiction between capacity adjustment and compressor reliability.
2Productivity
If the compressor is stopped and started intermittently to adjust capacity for low thermal load, then the capacity is reduced, but the operation efficiency is reduced due to pressure equalization and heat transfer between refrigerants
Solution Approach 1:
Instead of stopping and starting the compressor intermittently, the system maintains continuous compressor operation while injecting refrigerant to adjust capacity. This continuous operation eliminates the energy losses associated with stop-start cycles, including pressure equalization and heat transfer between high-pressure and low-pressure refrigerants, thereby maintaining high operation efficiency while achieving capacity adjustment.
Solution Approach 2:
The system uses refrigerant injection through the injection pipe and expansion valve to pneumatically/hydraulically adjust the capacity of the refrigeration cycle apparatus. By controlling the amount of refrigerant injected into the compressor suction side, the system can reduce capacity without stopping the compressor, avoiding the energy losses of intermittent operation while still matching low thermal load conditions.
3Adaptability or versatility
If the capacity is reduced by controlling rotation speed during low load operation, then the thermal load is matched, but the compressor must be driven at minimum rotation speed to ensure reliable refrigerating machine oil supply
Solution Approach 1:
The system changes the parameter of refrigerant temperature through heating in the refrigerant heater before injection. By heating the refrigerant, the system can inject warmer refrigerant that does not cause excessive cooling in the compressor, allowing the compressor to operate at lower rotation speeds while still maintaining reliable oil supply. This parameter change enables better thermal load matching without sacrificing operation efficiency.
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 approach effectively reduces the capacity of the refrigeration cycle apparatus during low loads, minimizing compressor stop-start cycles and enhancing operation efficiency by maintaining compressor reliability.
Implementation Method 1
an evaporator 103, through which the low-pressure refrigerant flows while receiving heat
Implementation Method 2
the low-pressure refrigerant flows while receiving heat from air to be conditioned in the evaporator 103
Implementation Method 3
a compressor 100, which compresses low-pressure refrigerant into high-pressure refrigerant
Implementation Method 4
a condenser 101, through which the high-pressure refrigerant flows while releasing heat
Data Source
AI summary
A refrigeration cycle apparatus includes: a refrigeration cycle circuit in which a compressor, a condenser, a first expansion valve, and an evaporator are connected by refrigerant pipes; an injection pipe having a refrigerant inflow side end and a refrigerant outflow side end, the refrigerant inflow side being connected between the condenser and the first expansion valve, the refrigerant outflow side end being connected to a suction side of the compressor; a second expansion valve provided at the injection pipe; and a controller that controls a rotation speed of the compressor and an opening degree of the second expansion valve. In the case of reducing a heat-exchange capability of the evaporator when the rotation speed of the compressor is a specified rotation speed, the controller performs a low load operation during which refrigeration is caused to flow through the injection pipe.