Refrigerated Truck Pressure Control for Faster Cryogenic Pull-Down
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Solution Overview
Problem
Existing cryogenic systems for transporting heat-sensitive products face inefficiencies due to fixed reservoir pressure, leading to high energy consumption, long 'pull-down' times, and limited modularity in refrigeration power, especially during varying load conditions.
Innovation Solution
Adapting the reservoir to operate at variable pressure by lowering the nominal pressure and incorporating a rapid pressurization system, activated based on refrigeration needs, to optimize cryogen use and increase refrigeration power dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If fixed reservoir pressure is used in cryogenic systems, then system simplicity is maintained, but refrigeration power modularity is limited and energy consumption increases
Solution Approach 1:
The system transitions from fixed pressure operation to variable pressure operation, where the reservoir pressure dynamically adapts to match refrigeration demand. The control system adjusts pressure in real-time based on thermal load conditions, enabling the cryogenic unit to deliver variable refrigeration power that matches actual needs rather than operating at constant capacity.
Solution Approach 2:
The invention changes the operating pressure parameter of the reservoir from a fixed value to a variable parameter that can be adjusted according to refrigeration requirements. By modifying pressure as a controllable parameter, the system achieves modularity in refrigeration power output, allowing optimization between partial load and full load conditions.
2Speed
If high refrigeration power is provided during pull-down phase, then rapid temperature drop is achieved, but energy consumption and cryogen use increase
Solution Approach 1:
The system dynamically adjusts refrigeration power based on the operational phase. During pull-down, high power is delivered to achieve rapid cooling, then automatically reduced during holding phase to match lower thermal loads. This dynamic power adjustment eliminates the need to maintain high power continuously, reducing overall energy consumption while achieving fast temperature drop when needed.
Solution Approach 2:
The control system implements periodic modulation of refrigeration power corresponding to different operational phases (pull-down vs. holding). The system alternates between high-power and low-power modes based on real-time temperature and thermal load conditions, optimizing the balance between cooling speed and energy consumption throughout the refrigeration cycle.
3Productivity
If fixed pressure operation is used, then system operation is simple, but pull-down time is extended and productivity decreases
Solution Approach 1:
The system uses dynamic pressure adjustment to accelerate the pull-down process. By increasing reservoir pressure during pull-down phase, the system delivers maximum refrigeration power to overcome thermal inertia and achieve rapid temperature drop. This dynamic response significantly reduces pull-down time compared to fixed pressure operation, improving overall productivity despite added control complexity.
Solution Approach 2:
The control system anticipates the need for high power during pull-down and pre-adjusts pressure settings accordingly. By preparing the system in advance with appropriate pressure levels before the cooling demand arises, the system can immediately deliver maximum refrigeration capacity when needed, reducing the time required to reach target temperatures.
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 operational flexibility, reduces energy consumption, and allows for efficient refrigeration by matching refrigeration power to demand, ensuring rapid temperature control and minimizing cryogen loss.
Implementation Method 1
the heat removed from the air first of all allows complete evaporation of the cryogenic fluid flowing through the heat exchanger
Implementation Method 2
complete evaporation of the cryogenic fluid flowing through the heat exchanger
Implementation Method 3
the enclosure furthermore being provided with an air circulation system (fans) that brings this air into contact with the cold walls of the heat exchanger, thereby making it possible to cool the air inside the cold chamber
Data Source
AI summary
A method for managing the operation of a refrigerated truck for transporting heat-sensitive products, of the indirect-injection type, in which the parameter ΔT=Tair inlet−Tsetpoint(Tair inlet: temperature of the air coming into contact with the heat exchanger internal to the truck as a result of the action of the fan, Tsetpoint: temperature to be set in the chamber inside the truck) is determined in real time and in which if ΔT is greater than an upper setpoint value ΔTsetpoint H, a rapid-pressurization (RMP) circuit is activated to vaporize some cryogen and thus increase the pressure in the head of gas above the reserve of cryogen of the truck.