Trailer Refrigeration Defrosting Using Radiator-Heated Condenser Airflow
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Solution Overview
Problem
In trailer refrigerating apparatuses, ambient temperatures equal to or lower than a certain level can cause a decrease in condenser pressure, leading to reduced defrosting performance due to refrigerant flowing towards the condenser, even when the outside-compartment fan is stopped, resulting in inadequate refrigerant supply to the evaporator during defrosting cycles.
Innovation Solution
The apparatus includes an electric compressor, condenser, expansion mechanism, evaporator, hot gas introduction path, and a switching valve, along with a generator, engine, radiator, and fan. During defrosting, if the condenser pressure is equal to or lower than a threshold, the fan forms an air flow from the radiator to the condenser, increasing its temperature and pressure, ensuring sufficient refrigerant flows to the evaporator, and a controller adjusts the engine's rotational speed to maintain adequate pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the outside-compartment fan is stopped to reduce energy consumption, then energy use is reduced, but refrigerant flows toward the condenser causing defrosting performance degradation
Solution Approach 1:
The system uses the engine-driven radiator as a heat source to warm the condenser, making the condenser itself generate the pressure differential needed to prevent refrigerant leakage. This self-regulating mechanism eliminates the need for active fan control during defrosting while maintaining defrosting performance.
Solution Approach 2:
The system changes the temperature parameter of the condenser by introducing warm air from the radiator, which in turn changes the pressure parameter of the refrigerant in the condenser. This parameter transformation prevents refrigerant flow toward the condenser without requiring fan operation.
2Reliability
If a discharge pressure adjusting valve is added to prevent refrigerant from flowing toward the condenser, then defrosting performance is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing engine-driven radiator to provide heat to the condenser, making the condenser self-regulate its pressure to prevent refrigerant leakage. This eliminates the need for additional discharge pressure adjusting valves or complex control systems.
Solution Approach 2:
The radiator, originally designed for engine cooling, is given a dual function by using it to heat the condenser during defrosting operations. This multi-functionality eliminates the need for separate heating devices or pressure control valves.
3Reliability
If the condenser pressure is increased to prevent refrigerant flow toward the condenser, then defrosting performance is improved, but the system requires additional active control components
Solution Approach 1:
The system achieves pressure regulation passively by using the radiator's natural heat output to warm the condenser. The pressure increase is a natural consequence of the temperature increase, eliminating the need for active pressure control systems.
Solution Approach 2:
The warm air from the radiator acts as an intermediary medium that transfers thermal energy to the condenser, indirectly increasing condenser pressure without requiring direct mechanical or electrical intervention in the refrigerant circuit.
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 configuration enhances defrosting efficiency by ensuring a sufficient refrigerant supply to the evaporator, reducing the need for a discharge pressure adjusting valve and lowering costs, while maintaining effective heating capacity even in low ambient temperatures or during traveling air stream exposure.
Implementation Method 1
the fan forms an air flow from the radiator to the condenser, increasing its temperature and pressure
Implementation Method 2
introducing refrigerant into the evaporator through the hot gas introduction path to defrost the evaporator
Implementation Method 3
a refrigerant circuit which includes an electric compressor, a condenser, an expansion mechanism, an evaporator
Data Source
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AI summary
A refrigerant circuit (21) is configured, which includes an electric compressor (22), a condenser (23), an expansion mechanism (24), an evaporator (25), a hot gas introduction path (123) connecting the electric compressor (22) and the evaporator (25) together, and a switching valve (143) for controlling a flow of refrigerant in the hot gas introduction path (123). In addition, a fan (26) is provided. In a defrosting cycle for introducing refrigerant into the evaporator (25) through the hot gas introduction path (123) to defrost the evaporator (25), if the pressure of the condenser (23) is equal to or lower than a predetermined threshold, the fan (26) forms an air flow from a radiator (45) to the condenser (23).