Cooling Circuit Superheat Control for Parallel Evaporators
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Solution Overview
Problem
In cool drying installations with multiple parallel heat exchangers, controlling superheating in a cooling circuit is unstable, leading to fluctuating temperatures and moisture content in the gas, which can result in equipment damage and inefficiency, especially in large installations with a wide choice of coolants and multiple evaporators.
Innovation Solution
A cooling circuit with a control unit that jointly controls expansion valves based on temperature and pressure sensor measurements to maintain a consistent superheating level across all evaporators, ensuring stable operation and equal gas temperatures in secondary sections, thereby protecting compressors and improving the quality and constancy of dried gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple parallel heat exchangers are used to increase cooling capacity, then the installation can be made larger and more cost-efficient, but the control of superheating becomes unstable leading to fluctuating temperatures
Solution Approach 1:
The patent combines the control of multiple parallel heat exchangers into a single centralized control system that manages all expansion valves simultaneously. This merging of control functions ensures coordinated operation across all heat exchangers, stabilizing the overall superheating level and preventing temperature fluctuations that would occur with independent control of each unit.
Solution Approach 2:
The patent implements a feedback control mechanism where temperature sensors monitor the outlet temperatures of all heat exchangers, and this information is fed back to the control unit. The control unit continuously adjusts the expansion valves based on this feedback to maintain stable superheating levels, resolving the instability issue that arises from using multiple parallel heat exchangers.
2Reliability
If the extent of superheating is increased to prevent liquid coolant from damaging the compressor, then compressor protection is improved, but the heat exchanging capacity decreases due to higher average temperature in the primary section
Solution Approach 1:
The patent dynamically adjusts the superheating parameter by controlling the expansion valves to maintain an optimal superheating degree rather than using a fixed high superheating level. This parameter optimization allows the system to protect the compressor from liquid coolant damage while minimizing the negative impact on heat exchanging capacity by keeping the average temperature in the primary section as low as possible.
Solution Approach 2:
The patent applies partial superheating control where the expansion valves are adjusted to provide just enough superheating to prevent liquid coolant from reaching the compressor, rather than applying excessive superheating throughout the system. This partial action maintains compressor protection while preserving maximum heat exchanging capacity.
3Ease of operation
If traditional individual control of expansion valves is used for each heat exchanger, then each evaporator can be controlled independently, but unstable control situation arises leading to fluctuating superheating levels and temperatures
Solution Approach 1:
The patent merges the individual expansion valve controls into a unified centralized control system that manages all heat exchangers simultaneously. This combination eliminates the unstable control interactions that occur when each heat exchanger is controlled independently, as the centralized system coordinates all valves to maintain stable superheating levels across the entire system.
Solution Approach 2:
The patent creates an equipotential control situation where all heat exchangers operate at the same control level through centralized management. The control unit applies consistent control logic to all expansion valves, ensuring that superheating levels remain stable and uniform across all heat exchangers, preventing the fluctuating temperatures that arise from independent control.
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 stabilizes the cooling circuit operation, enhances the quality and consistency of the dried gas, extends the lifespan of the cooling circuit, allows for larger and more cost-efficient installations, and reduces the need for sensors, ensuring a low moisture content in the gas.
Implementation Method 1
By entire or partial evaporation of the coolant in the evaporator, as is known, heat is extracted from the gas to be dried that flows through the secondary section, whereby this gas to be dried is cooled such that condensate is released
Implementation Method 2
a condenser that connects to the output of the compressor; an expansion valve followed by an evaporator that connects to the input of the aforementioned compressor(s)
Data Source
Figure 1
Figure 2
AI summary
Cooling circuit that is equipped with a coolant, a compressor (3), a condenser (5) and evaporator (8)- expansion valve (7) combinations, whereby the outlets of the evaporators (8) are connected to a collection pipe (9) that is connected to the compressor (3)/ whereby this cooling circuit (2) comprises a control unit (18) that is connected to a temperature sensor (24) and a pressure sensor (23) that are placed in the collection pipe (9) and which is connected to the expansion valves (7, 7A, 7B) for the control of them, and whereby the control unit (18) is provided with an algorithm for controlling the expansion valves (7, 7A, 7B) on the basis of the temperature sensor (24) and pressure sensor (23), in order to control the superheating in the collection pipe (9).