Two-Phase Refrigerant Temperature Control With Thermal Energy Buffering
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Solution Overview
Problem
Existing refrigeration systems face challenges in achieving precise and efficient temperature control due to phase changes in refrigerants, which can lead to instability and inefficiency in thermal energy transfer and storage.
Innovation Solution
The implementation of a two-phase thermodynamic system with a thermal capacitor and additional control loops that allow for selective retention and manipulation of thermal energy, using a refrigerant that transitions between gas and liquid phases to control temperature, incorporating features like back pressure control and an ambient temperature evaporator for enhanced efficiency and versatility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-phase refrigerant system is used for temperature control, then temperature control range and flexibility are improved, but system stability deteriorates due to phase changes
Solution Approach 1:
The system is divided into separate single-phase and two-phase flow paths. The two-phase path provides broad temperature control range while the single-phase path ensures stability. This segmentation allows each path to optimize for its specific function without compromising the other.
Solution Approach 2:
A thermal capacitor serves as an intermediary energy storage device between the refrigerant system and the thermal load. It buffers the instability caused by phase changes while maintaining the benefits of two-phase temperature control, effectively decoupling the load from refrigerant phase fluctuations.
2Measurement precision
If direct thermal contact between refrigerant and load is implemented, then temperature control precision is improved, but control complexity increases due to phase change management
Solution Approach 1:
The system dynamically switches between single-phase and two-phase flow modes based on the required temperature control precision and range. This dynamic adaptation allows the system to maintain precision while managing complexity through intelligent mode selection rather than fixed complex control architecture.
Solution Approach 2:
The TDSF system performs multiple functions: it provides both precise temperature control and broad temperature range coverage, stores thermal energy, and manages phase changes. This multi-functionality reduces the need for separate specialized components, thereby managing overall system complexity while maintaining precision.
3Adaptability or versatility
If thermal energy storage is added to the system, then system versatility is improved, but device complexity increases
Solution Approach 1:
The thermal capacitor is integrated into the existing refrigerant flow paths rather than being added as a completely separate subsystem. It merges the energy storage function with the thermal transfer infrastructure, providing versatility in processing modes while minimizing additional structural complexity.
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 enables precise temperature control with higher efficiency, stability, and versatility, allowing for various dynamic ranges and operating temperature bands, as well as efficient heating and cooling capabilities, exemplified by its application in on-site preparation of frozen comestibles like ice cream.
Implementation Method 1
a two phase medium is not only temperature controlled but is itself in direct thermal contact with the thermal load... varying from pure gas in an initial state through an intermediate range in which gas and liquid phases are mixed to provide a controllable temperature and pressure
Implementation Method 2
a reservoir of the refrigerant fluid may be employed as a thermal capacitor in the control loop paths that transfer refrigerant fluid so as to receive and retain thermal energy for particular purposes in thermal energy cycling or transfer
Implementation Method 3
one of which is controlled in rate while the other flow, which is then differentially variable, dependent on the controlled flow, is first condensed and then expanded to a lower temperature level
Implementation Method 4
a separate return path between the thermal load and the compressor input may be directed through an ambient temperature evaporator which operates the system so as to serve as a heat pump
Data Source
AI summary
Versatile temperature control systems adaptable to many different applications employ different states and proportions of a pressurized dual phase medium in direct contact with a thermal load. In one aspect of the invention, thermal energy generated by pressurization of a gaseous medium is stored at a selected temperature level so that it is later readily accessible. In addition, in accordance with the invention temperature control of a two-phase medium can be exercised across selectable dynamic ranges and with different resolutions. In accordance with such features, the control can be exerted by varying the input flow rate of a mixture applied to a thermal load, or by controlling the back pressure of the flow through the thermal load.In accordance with another feature of the invention, substantial energy conservation can be effected by employing an ambient temperature evaporator configuration between the thermal load and the input to the compressor. This variant also utilizes the two-phase characteristics of the medium. Moreover, the system can be configured compactly utilizing a thermal reservoir for retaining thermal energy for special purposes. In a food processing system for providing a frozen product, for example, the thermal reservoir can be accessed to utilize the refrigerant itself in different operating modes, such as rapid heating and system cleansing. In the food processing application, target temperatures can be set and maintained on a platen which is to receive food ingredients using energy flows at two different enthalpies, to enable rapid freezing or temperature elevation.