CO2 Refrigerant Charge Control for Stable Supercritical Air Conditioning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing refrigerating air conditioning systems using CO2 as a refrigerant face challenges in stabilizing operation control due to long stabilization times and complex control requirements, especially in multiple-type systems with long extension pipes, where determining the appropriate decompression device for refrigerant adjustment is complicated, leading to unstable operation and inefficient cooling.
Innovation Solution
A refrigerating air conditioning system with a refrigeration cycle that includes a compressor, user and heat source side heat exchangers, decompression devices, and a refrigerant amount adjusting circuit, which controls the superheat at the heat source side decompression device and adjusts the refrigerant amount in the user side heat exchanger to maintain a predetermined state, allowing for efficient operation by storing refrigerants of different densities in a storage container connected to the cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the decompression device is controlled to change the operating state of the evaporator for controlling the amount of refrigerant in the receiver, then the refrigerant amount in the receiver can be controlled, but it takes a long time to stabilize the operation after occurrence of a state change in the evaporator
Solution Approach 1:
The patent introduces a receiver as an intermediary storage device between the evaporator and the decompression device. The receiver temporarily stores refrigerant and allows for controlled release, acting as a buffer that decouples the evaporator state changes from the decompression device operation. This intermediary mechanism enables faster stabilization by preventing direct propagation of state changes through the refrigerant circulation system.
2Adaptability or versatility
If multiple type refrigerating air conditioning system is provided with a plurality of indoor side heat exchangers, then the system can serve multiple indoor machines, but the extension pipe length becomes long and the operation stabilization time increases
Solution Approach 1:
The receiver serves as a central intermediary storage point for refrigerant distribution to multiple indoor heat exchangers. By positioning the receiver at the outdoor unit and using it as a common refrigerant reservoir, the system can quickly adjust refrigerant distribution to various indoor machines without requiring long stabilization times despite the extended pipe lengths connecting multiple indoor units.
3Adaptability or versatility
If decompression devices are provided corresponding to the evaporators of the respective indoor machines, then the capabilities can match the loads, but the control becomes complicated when determining which decompression device to use for adjusting refrigerant amount
Solution Approach 1:
The patent merges the refrigerant amount control function into a single receiver located at the outdoor unit, rather than distributing control across multiple decompression devices at indoor units. This consolidation simplifies the control architecture by providing a centralized control point for refrigerant amount adjustment, while the individual indoor decompression devices focus solely on load matching through superheat control.
4Ease of operation
If the decompression device is provided in the indoor machine, then the judgment control for adjusting refrigerant amount can be performed in the outdoor machine, but the control is further complicated by transmitting judgment between machines
Solution Approach 1:
The patent extracts the refrigerant amount control function from the indoor decompression devices and relocates it to the receiver at the outdoor unit. This separation of functions eliminates the need for complex inter-machine communication and judgment transmission, as all refrigerant amount adjustments are made centrally at the outdoor unit through the receiver, while indoor units focus exclusively on their local superheat 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 approach enables quick and stable control of refrigerant distribution, optimizing the high-pressure value for maximum COP, resulting in efficient operation and reliable performance by maintaining constant refrigerant amounts in heat exchangers and adjusting the refrigerant circulation based on predetermined pressure and temperature states.
Implementation Method 1
a refrigeration cycle configured to circulate refrigerant through a compressor, a user side heat exchanger, a user side decompression device, a heat source side decompression device and a heat source side heat exchanger
Implementation Method 2
a refrigeration cycle configured to circulate refrigerant through a compressor, a user side heat exchanger, a user side decompression device, a heat source side decompression device and a heat source side heat exchanger and operated with a high-pressure value being a pressure higher than a critical pressure of the refrigerant and a low-pressure value being a pressure lower than the critical pressure
Data Source
AI summary
In a refrigerating air conditioning system using refrigerant such as CO2 used in a supercritical area, a highly efficient refrigerating air conditioning system is provided by adjusting the amount of refrigerant in a radiator which contributes to the efficiency of the system stably and quickly. During heat utilizing operation, the superheat at the exit of an evaporator is controlled to a predetermined value by controlling the opening of an expansion valve provided on the upstream side of the evaporator, and an expansion valve is controlled so that the state of refrigerant in a connection pipe on the high-pressure side becomes a supercritical state. In this state, a flow rate control valve is controlled to change the density of the refrigerant stored in a refrigerant storage container and the amount of refrigerant existing in the radiator is adjusted. A target high-pressure value and a target value of the radiator exit temperature are set and the capacity of the compressor is controlled to obtain the target values, and the amount of refrigerant existing in the radiator is adjusted by the refrigerant amount adjusting circuit.