Microvalve Flow Sensing for Faster Refrigerant Response
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Solution Overview
Problem
In refrigerant cooling systems, there is an undesirably long delay in detecting the rise in fluid pressure at the microvalve after the solenoid valve is re-opened, leading to a delayed supply of pressurized fluid to the consuming device, which hampers quick cooling.
Innovation Solution
The microvalve is equipped with a flow sensing capability that detects the change in electrical resistance of its ribs due to temperature changes caused by incoming fluid, allowing the electronic controller to quickly modulate the flow and avoid the delay by instantaneously detecting the fluid flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fluid pressure sensor is located downstream of the microvalve as part of the superheat controller, then the system can detect fluid pressure, but the rise in fluid pressure at the microvalve cannot be detected instantaneously, causing a delay in microvalve response
Solution Approach 1:
A thermal conductor element is introduced as an intermediary between the fluid and the flow sensor. The element conducts thermal energy from the incoming fluid to the sensor, enabling instantaneous detection of fluid presence without requiring the sensor to be positioned downstream where pressure detection is delayed.
Solution Approach 2:
The mechanical pressure-based detection system is replaced with a thermal-based detection system. Instead of using a pressure sensor that requires fluid to travel downstream, the invention uses thermal conduction to detect fluid flow instantaneously at the microvalve location.
2Reliability
If the microvalve remains closed until pressure is detected downstream, then the system avoids premature opening, but the supply of pressurized fluid to the consuming device is delayed
Solution Approach 1:
The flow sensor is activated and ready to detect fluid flow before the microvalve opens. When fluid enters the microvalve, the thermal conductor immediately conducts the thermal energy to the sensor, triggering instantaneous microvalve opening without waiting for downstream pressure detection.
Solution Approach 2:
The thermal flow sensor provides immediate feedback to the control system when fluid is detected at the microvalve inlet. This feedback loop enables the microvalve to open instantly in response to fluid presence, eliminating the delay inherent in downstream pressure-based feedback systems.
3Measurement precision
If only a small amount of liquid refrigerant passes through the microvalve initially, then the downstream pressure sensor can detect the flow, but the consuming device does not receive sufficient pressurized fluid quickly enough
Solution Approach 1:
The thermal conductor serves as an intermediary that allows the flow sensor to detect fluid presence with high precision while the microvalve simultaneously opens fully to deliver sufficient fluid quantity. The thermal conductor enables detection without restricting the main fluid flow path.
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 enables the microvalve to begin modulating fluid flow to the consuming device more quickly after the solenoid valve is re-opened, reducing the delay in supplying pressurized fluid and enhancing cooling efficiency.
Implementation Method 1
the ribs are used as a flow sensor to detect the flow of fluid through the microvalve by measuring a change in electrical resistance resulting from temperature changes
Implementation Method 2
measuring a change in electrical resistance resulting from temperature changes
Data Source
AI summary
A system for controlling the flow of a fluid from a source to a load includes a source. An on/off type of control valve communicates with the source. A micro-electric mechanical system communicates with the on/off type of control valve. A consuming device communicates with the micro-electric mechanical system. An electronic controller that communicates with the consuming device and the source. The electronic controller measures a change in a parameter of the micro-electric mechanical system that results from the flow of fluid through the micro-electric mechanical system to sense a flow of fluid through a micro-electric mechanical system.