Expansion Valve Control for Low-Temperature Air Conditioner Cooling
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Solution Overview
Problem
In low outside air temperature environments, air conditioners face challenges in controlling the amount of refrigerant circulated due to reduced outdoor fan rotations, leading to excessive supercooling and reduced cooling capability, with existing methods being inefficient and requiring additional sensors.
Innovation Solution
A method to control the expansion valve and outdoor fan rotations to maintain a predetermined temperature difference between the outdoor and indoor heat exchangers, allowing for rapid adjustment of refrigerant circulation without significant design changes to the air conditioner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of rotations of the outdoor fan is reduced to prevent supercooling of the outdoor heat exchanger, then the refrigerant can circulate properly, but the cooling capability is reduced and the response speed is slowed
Solution Approach 1:
The patent changes the control parameter from outdoor fan rotation speed to expansion valve opening degree. By controlling the expansion valve opening based on the temperature difference between indoor and outdoor heat exchangers, the system maintains reliable refrigerant circulation while preserving cooling capability through precise refrigerant flow regulation rather than relying solely on fan speed reduction.
2Productivity
If the expansion valve is opened larger to circulate liquid refrigerant through the indoor heat exchanger, then cooling capability is improved, but the system becomes more complex and requires additional sensors
Solution Approach 1:
The patent makes the existing temperature sensors serve a dual purpose: they detect temperatures for normal cooling operation and simultaneously provide data for calculating the temperature difference used to control expansion valve opening in low-temperature environments. This eliminates the need for additional sensors while enabling precise control of refrigerant circulation and cooling capability.
3Reliability
If the outdoor fan rotates at lower speed in low temperature environment, then supercooling is prevented, but the response speed of the system is reduced
Solution Approach 1:
The patent implements a feedback control system where the expansion valve opening is continuously adjusted based on real-time temperature difference measurements between indoor and outdoor heat exchangers. This closed-loop control maintains reliable supercooling prevention while achieving fast response speed through active feedback regulation rather than passive fan speed reduction.
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 method enables effective control of refrigerant circulation, preventing supercooling and ensuring optimal cooling performance in low outside air temperatures without the need for additional sensors, improving response speed and maintaining efficient refrigerant flow.
Implementation Method 1
it is necessary to open the expansion valve (in many cases, an electronic expansion valve)
Implementation Method 2
the refrigerant in the outdoor heat exchanger is excessively supercooled
Implementation Method 3
using the indoor heat exchanger and the outdoor heat exchanger as a condenser and an evaporator
Implementation Method 4
using the outdoor heat exchanger and the indoor heat exchanger as the condenser and the evaporator
Implementation Method 5
the air conditioner performs a cooling operation to circulate a high-pressure and high-temperature refrigerant gas
Implementation Method 6
a high-pressure and high-temperature refrigerant gas discharged from the compressor
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method of controlling an air conditioner includes a step of controlling an opening degree of the expansion valve and/or the number of rotations of an outdoor fan of the outdoor heat exchanger such that the difference Tx (= Te - Ti) between the temperature Te of the outdoor heat exchanger and the temperature Ti of the indoor heat exchanger is within a predetermined range, in a cooling mode in a low outside air temperature environment. Specifically, the opening degree of the expansion valve is adjusted, with the number of rotations of the outdoor fan being reduced to be smaller than that in a normal cooling mode, and then, the number of rotations of the outdoor fan is adjusted with the opening degree of the expansion valve being fixed, thereby controlling the difference Tx to be substantially constant.