Preform Heating Device Using Preheating and Microwave Units
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Solution Overview
Problem
Microwave-based heating devices for preforms face inefficiencies due to the physical principles governing microwave heating, which require multiple stations and result in non-uniform heating, leading to increased process time and reduced throughput.
Innovation Solution
A device that combines a microwave heating unit with a preheating unit using heated air and waste heat from the microwave generator to increase the dielectric loss factor of PET preforms, allowing for more efficient heating by preheating the preforms before microwave exposure, and using a heat exchanger to recycle waste heat for further heating, while also designing the device to heat the outside of preforms to counteract temperature gradients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If microwave heating is used to heat preforms, then heating speed is improved, but heating uniformity deteriorates due to temperature gradients and requirement of multiple stations
Solution Approach 1:
The patent applies preliminary action by preheating the preform using conventional heating means (heating elements or infrared radiation) before subjecting it to microwave heating. This preliminary heating raises the baseline temperature of the preform, reducing the temperature gradient that develops during microwave heating and improving overall heating uniformity while maintaining the speed advantage of microwave heating.
Solution Approach 2:
The patent applies local quality by using different heating methods for different regions or stages of the heating process. Conventional heating elements or infrared radiation are used for initial uniform heating, while microwave heating is applied subsequently. This combination allows each heating method to address its strengths - conventional heating for uniformity and microwave for speed - thereby resolving the contradiction between heating speed and heating uniformity.
2Manufacturing precision
If multiple microwave stations are used to achieve uniform heating, then heating uniformity is improved, but device complexity and process time increase
Solution Approach 1:
The patent merges two different heating methods - conventional heating (heating elements or infrared radiation) and microwave heating - into a single integrated heating system. This combination allows the system to achieve heating uniformity that would otherwise require multiple microwave stations, while avoiding the complexity and increased process time associated with multiple microwave stations. The conventional heating provides a uniform thermal baseline that complements the rapid microwave heating.
Solution Approach 2:
The patent uses conventional heating elements or infrared radiation as an intermediary step between ambient temperature and full microwave heating. This intermediary preheating phase creates a more favorable thermal state for subsequent microwave heating, reducing the severity of temperature gradients and allowing uniform heating to be achieved with a single microwave station rather than multiple stations.
3Productivity
If microwave heating power is increased to reduce process time, then productivity is improved, but energy loss and inefficiency increase
Solution Approach 1:
The patent applies parameter changes by modifying the thermal state parameters of the preform before microwave heating. By preheating the preform to a higher temperature using conventional heating methods, the dielectric loss factor of the material increases, which enhances its ability to absorb microwave energy. This parameter change allows for more efficient microwave heating at lower power levels, improving energy efficiency while maintaining or increasing productivity.
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 enhances the heating power output and uniformity of preforms, increasing the efficiency and throughput of the microwave heating process by leveraging the temperature dependence of the dielectric loss factor and utilizing waste heat, resulting in more effective energy use and reduced process time.
Implementation Method 1
a preheating unit (4) which is arranged upstream in the transport direction of the containers with respect to the microwave heating device (20)
Implementation Method 2
a microwave heating device (20) which has a microwave generator (22) and a microwave conductor (24)
Implementation Method 3
The device has a heat exchanger which is in heat-exchanging connection with the microwave generating unit or the microwave generator
Implementation Method 4
The use of microwave radiation allows the preforms to be heated more quickly. Due to the physical principles, a resonator cavity is required for microwave heating
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The invention relates to a device (1) for heating containers (10) and, in particular, preforms, comprising a microwave heating device (20) which includes a microwave generator (22) and a microwave conductor, and a transport device (12) which transports the containers. According to the invention, the device includes a further heating device (4) which heats the containers (10), wherein the further heating device is a preheating unit (4) which is arranged upstream of the microwave heating device (20) in the transport direction of the containers (10).