Indirect Cooling of Cutting Tool via Micro-Channel Heat Exchanger
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Solution Overview
Problem
Current machining technologies face challenges in efficiently managing heat at the tool-chip interface, leading to high costs, environmental impact, and health risks associated with cutting fluids, particularly in high-volume machining and when working with low thermal conductivity materials like titanium.
Innovation Solution
An indirect cooling system utilizing a micro-channel heat exchanger installed on the tool holder with liquid nitrogen as the working fluid, which leverages latent heat transfer to efficiently remove heat from the tool-chip interface, reducing the environmental and health hazards associated with traditional cutting fluids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional cutting fluids are used for cooling and lubrication, then tool temperature is decreased and tool life is increased, but machining costs increase and health risks are created
Solution Approach 1:
The patent uses liquid nitrogen as a coolant, which is an inert substance that does not pose health risks or environmental hazards like traditional cutting fluids. The nitrogen evaporates after cooling, leaving no harmful residues, thus eliminating the harmful factors associated with conventional cutting fluids while maintaining effective tool cooling.
Solution Approach 2:
The invention extracts and eliminates the harmful components (traditional cutting fluids) from the machining process by replacing them with liquid nitrogen, thereby removing the source of health risks and environmental pollution while preserving the essential cooling function.
2Object-affected harmful factors
If dry machining is used to eliminate cutting fluids, then health risks are reduced, but energy consumption increases and tool wear increases
Solution Approach 1:
The patent utilizes the phase transition of liquid nitrogen to gas during evaporation, which absorbs significant latent heat of vaporization. This phase change provides highly efficient cooling without requiring the high energy input needed for dry machining, thereby reducing energy consumption while maintaining tool cooling effectiveness.
Solution Approach 2:
The invention employs liquid nitrogen delivery systems similar to hydraulic and pneumatic systems, using controlled flow rates and pressure regulation to optimize cooling efficiency and minimize energy consumption, unlike conventional dry machining which relies on high-power machine tools.
3Temperature
If liquid nitrogen is sprayed directly into the machining zone for cooling, then tool temperature is decreased, but large amounts of nitrogen are consumed and environmental impact increases
Solution Approach 1:
The patent introduces a micro-channel heat exchanger as an intermediary between the liquid nitrogen source and the tool-chip interface. This heat exchanger efficiently transfers heat from the tool to the nitrogen with high heat transfer coefficients, requiring much smaller nitrogen flow rates (1-10 mL/min) compared to direct spraying methods while achieving the same cooling effect.
Solution Approach 2:
The invention changes the delivery method parameter from direct high-flow spraying to indirect low-flow heat exchanger-based cooling. This parameter change optimizes nitrogen consumption by utilizing the high heat transfer surface area-to-volume ratio of micro-channels, reducing nitrogen usage by orders of magnitude while maintaining effective tool cooling.
4Strength
If high-pressure coolant jets are used to reduce tool wear, then tool wear is decreased, but equipment complexity increases and machining time increases
Solution Approach 1:
The patent extracts and removes the complex high-pressure delivery system, positioning mechanisms, and large compressors from the cooling apparatus. By using a simple liquid nitrogen reservoir connected to a micro-channel heat exchanger, the invention achieves effective cooling without the cumbersome equipment required by high-pressure jet systems.
Solution Approach 2:
The micro-channel heat exchanger system is self-regulating and requires no active positioning or complex control mechanisms. The liquid nitrogen automatically flows through the heat exchanger channels, providing continuous cooling without requiring operator intervention or complex positioning systems, thereby reducing device complexity and machining time.
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 system achieves significant reductions in tool wear, energy consumption, and production costs while maintaining high part quality and dimensional accuracy, with a minimal environmental impact by using much lower flow rates of cryogenic coolant compared to direct cooling methods.
Implementation Method 1
uses a micro-channel heat exchanger installed on the tool holder to remove a portion of the thermal energy generated during machining
Implementation Method 2
The indirect cooling uses very small flow rates of a cryogenic coolant such as, liquid nitrogen as a working fluid... uses the latent heat of vaporization of the cryogen as a means to remove heat from the tool-chip interface
Implementation Method 3
uses the latent heat of vaporization of the cryogen as a means to remove heat from the tool-chip interface... uses very small flow rates of a cryogenic coolant such as, liquid nitrogen as a working fluid
Data Source
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AI summary
A cutting tool having a cutting element such as an insert is cooled indirectly by a micro-channel heat exchanger that is mounted against the rear face of the insert. The heat exchanger is formed with an internal cavity that receives a coolant such as a cryogen. The cavity may include fins to enhance the removal of heat by the cryogen from the insert. Coolant inlet and outlet tubes are coupled to the interior of the heat exchanger to supply cryogen to the cavity. The flow rate of cryogen required to cool the insert during a given machining operation is less than one percent of the amount of standard coolant required to cool the same insert during the same machining operation.