Thermostatic Expansion Valve Restriction for Startup Noise Attenuation
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Solution Overview
Problem
In air conditioning systems, thermostatic expansion valves open rapidly during compressor startup, leading to noise and inefficient refrigerant flow due to the pressure differential between the charge and pressure chambers not being managed effectively, resulting in rapid valve opening before the refrigerant is fully sub-cooled.
Innovation Solution
Incorporating a restriction flow passage between the pressure and sensor chambers to limit fluid communication, slowing the valve opening and allowing more time for the refrigerant to reach a sub-cooled state, thereby reducing noise and initial refrigerant flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the pressure chamber is in fluid communication with the sensor chamber through a wide open flow passage, then the pressure chamber pressure follows the suction pressure rapidly, but the valve opens rapidly causing noise and inefficient refrigerant flow
Solution Approach 1:
The patent changes the flow passage parameters by introducing a restriction (reducing the cross-sectional area or increasing the flow path resistance) between the pressure chamber and sensor chamber. This modification alters the pressure transmission characteristics, slowing down the pressure equalization rate and thereby controlling the valve opening speed to reduce noise during compressor startup.
2Productivity
If the valve opens rapidly at compressor startup, then the refrigerant flow rate increases quickly, but the refrigerant is not fully sub-cooled leading to noise and system inefficiency
Solution Approach 1:
The restriction in the flow passage performs a preliminary control action on the pressure transmission before the valve opens. By limiting the pressure equalization rate in advance, the system ensures that the valve opens gradually only after the refrigerant has had time to become sufficiently sub-cooled, preventing noise and inefficiency associated with premature rapid opening.
3Stability of the object's composition
If the charge chamber temperature does not rapidly follow the evaporator outlet temperature, then the charge chamber pressure remains steady, but the pressure chamber pressure drops rapidly causing the valve to open substantially before refrigerant is sub-cooled
Solution Approach 1:
The restricted flow passage acts as an intermediary element between the pressure chamber and sensor chamber. It mediates the pressure transmission process by controlling the rate at which pressure changes are communicated, thereby balancing the response between the stable charge chamber and the rapidly changing pressure chamber to prevent noisy rapid valve opening.
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
The gradual opening of the thermostatic expansion valve minimizes noise and ensures a more sub-cooled state of the refrigerant, reducing vibrations and the initial refrigerant flow rate, thus enhancing the system's operational efficiency during compressor startup.
Implementation Method 1
A restriction flow passage is located to provide fluid communication between the pressure chamber and the sensor chamber and configured to limit a flow rate from the pressure chamber to sensor chamber
Implementation Method 2
A diaphragm separates a charge chamber and a pressure chamber where a pressure differential on two sides of the diaphragm controls the opening and closing of a valve element
Data Source
AI summary
A thermostatic expansion valve includes a valve body having an evaporator inlet port, an evaporator outlet port, a suction line port, and a liquid line port. A sensor chamber formed within the valve body is disposed between the evaporator outlet port and the suction line port. A valve is disposed within the valve body controls a flow of refrigerant from the liquid line port to the evaporator inlet port. A diaphragm separates a charge chamber and a pressure chamber where a pressure differential between a charge chamber and a pressure chamber controls the positioning of the valve. A restriction flow passage located to provide fluid communication between the sensor chamber and the pressure chamber is configured to limit a flow rate from the pressure chamber to sensor chamber, thereby slowing the opening of the valve resulting in a reduction of noise generated following an initial startup of a compressor.