Multi-Compartment Transport Refrigeration Adaptive Superheat Control
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Solution Overview
Problem
Conventional multi-compartment transport refrigeration systems face challenges in maintaining optimal temperature control across compartments, leading to potential flooding and engine instability due to shared evaporating temperatures and dynamic power disturbances.
Innovation Solution
The system adjusts the superheat setpoint of the warmer compartment based on the return air temperatures of both compartments, using a controller to calculate an adjusted superheat setpoint that balances the refrigerant flow and prevents excessive flooding in the frozen compartment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common suction plenum is used to share evaporating temperature across compartments, then system complexity is reduced, but temperature control precision deteriorates causing flooding in frozen compartments
Solution Approach 1:
The patent segments the common suction plenum into separate suction plenums for the frozen compartment and perishable compartment. This allows independent evaporating temperature control for each compartment, preventing the flooding issue that occurs when the perishable compartment's lower saturation temperature causes excessive refrigerant flow into the frozen compartment evaporator.
Solution Approach 2:
The patent implements local quality by allowing each compartment to have its own evaporating temperature saturation point tailored to its specific requirements. The frozen compartment can maintain a higher saturation temperature while the perishable compartment operates at a lower saturation temperature, optimizing each compartment's performance without interfering with the other.
2Manufacturing precision
If pulsed cooling with fixed PWM cycle is used to prevent flooding, then compartment temperature control is improved, but engine stability deteriorates due to dynamic power disturbances
Solution Approach 1:
The patent transitions from fixed PWM cycling to dynamic superheat setpoint adjustment. The superheat setpoint for the perishable compartment is continuously adjusted based on the temperature difference between compartments, allowing smooth, continuous control of refrigerant flow that avoids the abrupt on/off transitions of PWM while maintaining effective flooding prevention.
Solution Approach 2:
The patent changes the control parameter from binary PWM on/off control to continuous superheat setpoint adjustment. By dynamically modifying the superheat setpoint based on compartment temperature differential, the system achieves smooth refrigerant flow control that prevents flooding without causing engine power disturbances.
3Productivity
If expansion device is opened to 100% due to high sensed superheat, then perishable compartment cooling capacity is maximized, but frozen compartment evaporator flooding occurs
Solution Approach 1:
The patent implements feedback control by continuously monitoring the temperature difference between the frozen and perishable compartments and using this information to dynamically adjust the perishable compartment's superheat setpoint. When the temperature differential increases, the superheat setpoint increases, automatically reducing refrigerant flow to prevent flooding while maintaining adequate cooling capacity.
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 refrigeration system, reduces engine disturbances, and improves efficiency by minimizing saturation flooding and extending the life of expansion devices, while maintaining optimal temperature control across compartments.
Implementation Method 1
The remote evaporators are generally disposed in the refrigerant circulation circuit in parallel with the main evaporator
Implementation Method 2
The refrigeration unit must have sufficient refrigeration capacity to maintain the product stored within the various compartments of the container at the particular desired compartment temperatures
Data Source
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AI summary
A multi-compartment transport refrigeration system (10) includes a first evaporator (40) having an first evaporator inlet coupled to a first evaporator expansion device (140) and a first evaporator outlet coupled to a compressor inlet path, the first evaporator for cooling a first compartment of a container at a first temperature; a second evaporator (609 having a second evaporator inlet coupled to a second evaporator expansion device (160) and a second evaporator outlet coupled to the compressor inlet path, the second evaporator for cooling a second compartment of the container at a second temperature greater than the first temperature; and a controller (550) for controlling the first evaporator expansion device in response to a first superheat setpoint and controlling the second evaporator expansion device in response to a second superheat setpoint, the controller adjusting the second superheat setpoint in response to the second temperature and the first temperature.