Test Chamber and Control Method
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Solution Overview
Problem
Existing test chambers using carbon dioxide as a refrigerant face challenges in efficiently managing temperature fluctuations and energy consumption due to high pressure requirements and limited temperature range, especially when carbon dioxide's triple point restricts cooling below −56.6°C, leading to inefficient compressor operation and increased costs.
Innovation Solution
A cooling circuit design with a valve device that allows refrigerant to be directed to either the low-pressure or high-pressure compressor, enabling dynamic temperature control and energy-efficient operation by selectively using one or both compressors based on load requirements, utilizing a 3-way valve for efficient refrigerant distribution and bypass systems to manage temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If carbon dioxide is used as a refrigerant with a single compressor, then the device complexity is reduced, but the temperature range is limited below −56.6°C due to the triple point
Solution Approach 1:
The compressor system is segmented into two independent compressors (first compressor for low-pressure operation, second compressor for high-pressure operation) that can operate separately or together. This segmentation allows the system to overcome the temperature limitation of single-compressor CO2 systems while maintaining manageable complexity through modular architecture.
Solution Approach 2:
The dual-compressor system provides multi-functionality by enabling the refrigeration system to operate across a broader temperature range than a single compressor could achieve. The system can selectively engage either compressor or both simultaneously depending on the required temperature and load conditions, making the system adaptable to diverse operating scenarios.
2Temperature
If both compressors operate continuously, then the temperature control range is extended, but the energy consumption increases
Solution Approach 1:
The system dynamically selects which compressor(s) to operate based on real-time temperature requirements and load conditions. The control system adjusts compressor operation modes (first compressor only, second compressor only, or both together) to match the instantaneous cooling demand, preventing unnecessary energy consumption while maintaining the required temperature range.
Solution Approach 2:
The system changes operational parameters by switching between different compressor configurations based on the required temperature and cooling load. This parameter change approach allows the system to achieve broad temperature control capability without continuously operating all components at full capacity, thereby reducing overall energy consumption.
3Reliability
If the cooling capacity is increased to handle load fluctuations, then the temperature stability improves, but the compressor size and cost increase
Solution Approach 1:
The cooling capacity is segmented into two compressors of different sizes and pressure ratings. This segmentation allows the system to handle varying load requirements by engaging only the necessary compressor capacity, avoiding the need for a single oversized compressor that would be required to handle maximum load fluctuations alone.
Solution Approach 2:
The system uses partial action by selectively engaging only the required compressor capacity for each operating condition. Instead of always operating at full capacity to handle maximum load fluctuations, the system applies just enough cooling capacity needed for current conditions, improving efficiency while maintaining temperature stability.
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
Enables efficient temperature control in a range of −40°C to +180°C with reduced energy consumption by optimizing compressor usage and maintaining a small temperature difference across the heat exchanger, allowing for dynamic temperature changes while using carbon dioxide as a refrigerant.
Implementation Method 1
a cooling circuit with carbon dioxide as a refrigerant
Implementation Method 2
a low-pressure compressor, and a high-pressure compressor downstream of the low-pressure compressor in a flow direction of the refrigerant
Implementation Method 3
a heat exchanger in the test space
Implementation Method 4
an expansion valve
Data Source
AI summary
A method for conditioning air in a test space of a test chamber, the test space being sealable against an environment and being temperature-insulated, and a test chamber, in particular a climate chamber, for receiving test material. A temperature in a temperature range of −40° C. to +180° C. is established within the test space by a cooling device of a temperature control device of the test chamber, which comprises a cooling circuit with carbon dioxide as a refrigerant, a heat exchanger in the test space, a low-pressure compressor, and a high-pressure compressor downstream of the low-pressure compressor in a flow direction of the refrigerant, a gas cooler, and an expansion valve. The temperature in the test space is controlled and/or regulated by a control device of the test chamber, the cooling circuit having a valve device by which the refrigerant is conducted to the low-pressure compressor or to the high-pressure compressor.