Refrigerated Truck Cryogenic Cooling with Variable Pressure Control
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Solution Overview
Problem
Existing cryogenic refrigeration systems in refrigerated trucks face inefficiencies due to fixed tank pressure, leading to high cryogen consumption, long 'pull-down' times, and limited modularity between full and partial load refrigeration needs, resulting in suboptimal cooling capacity and economic imbalance.
Innovation Solution
Adapting the tank configuration to operate at variable pressure by lowering the nominal pressure and incorporating a rapid pressurization system, which automatically adjusts pressure based on refrigeration needs using solenoid valves and a control system to optimize cryogen use and cooling capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the refrigeration system operates at fixed nominal pressure (3.2 barg), then the system maintains stable operation, but the cooling capacity modularity between full load and partial load is limited and cryogen consumption increases
Solution Approach 1:
The patent implements variable pressure operation in the cryogenic tank, transitioning from fixed nominal pressure (3.2 barg) to dynamic pressure adjustment. The control system modifies tank pressure between 1.5-4.0 barg based on refrigeration load requirements, enabling the system to adapt cooling capacity to actual needs and improve modularity between full and partial load conditions while reducing cryogen consumption
Solution Approach 2:
The patent changes the operating pressure parameter of the cryogenic tank from a fixed value (3.2 barg) to a variable range (1.5-4.0 barg). By adjusting pressure as a controllable parameter, the system optimizes cryogen flow rate and cooling capacity according to thermal load, achieving better adaptability and reduced substance loss
2Loss of substance
If the tank pressure is lowered to optimize cryogen consumption, then cryogen use improves, but the pull-down time increases and cooling capacity decreases
Solution Approach 1:
The patent employs periodic or pulsed pressurization through the RMP circuit during the pull-down phase. Instead of maintaining constant high pressure, the system applies pressure increases intermittently to provide cooling bursts that overcome thermal inertia, enabling rapid temperature descent while maintaining overall lower average pressure to optimize cryogen consumption
Solution Approach 2:
The patent activates the rapid pressurization circuit (RMP) in advance during the pull-down phase to quickly establish necessary cooling capacity. This preliminary high-pressure action ensures rapid temperature reduction, after which the system transitions to lower pressure operation for maintenance, optimizing both speed and consumption
3Speed
If the nominal tank pressure is increased to reduce pull-down time, then cooling capacity improves, but cryogen consumption increases and filling time from upstream storage increases
Solution Approach 1:
The patent implements dynamic pressure adjustment where the tank operates at higher pressure temporarily during pull-down to achieve rapid cooling, then transitions to lower pressure during maintenance phases. This dynamic approach optimizes the balance between pull-down speed and overall cryogen consumption, avoiding sustained high-pressure operation
Solution Approach 2:
The patent uses the rapid pressurization circuit to quickly overcome the thermal inertia of the system during pull-down, rushing through the critical temperature descent phase efficiently. This allows the system to complete the demanding pull-down phase quickly and then operate at lower pressure, minimizing total cryogen consumption
4Device complexity
If fixed pressure operation is maintained, then system simplicity is preserved, but the difference between full load and partial load power remains limited resulting in overconsumption
Solution Approach 1:
The patent introduces dynamic pressure control with automatic adjustment between 1.5-4.0 barg based on thermal load detection. The control system monitors temperature and cooling requirements, automatically modifying tank pressure to match actual demand, thereby eliminating cryogen overconsumption while maintaining manageable system complexity through automated 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 solution enhances modularity and efficiency by reducing cryogen consumption, shortening 'pull-down' times, and allowing for flexible operation between full and partial load conditions, while maintaining low operational costs.
Implementation Method 1
the heat extracted from the air first allows complete evaporation of the cryogenic fluid circulating in the exchanger
Implementation Method 2
an air circulation system (fans) bringing this air into contact with the cold walls of the exchanger
Implementation Method 3
the rapid pressurization circuit RMP is activated by opening said valve of the pressurization circuit (EV Rp) in order to vaporize cryogen in said exchanger/heater and thus increase the pressure in the gas headspace of the reserve
Implementation Method 4
vaporize cryogen in said exchanger/heater
Data Source
Figure 1~2
Figure 3~4
Figure 5
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.