Refrigeration system , cascade refrigeration system and control method thereof
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Solution Overview
Problem
Cascade refrigeration systems face high and unstable temperature differences between the refrigerant in the condensation and evaporation parts of the evaporative condenser, leading to potential damage and reduced service life due to frequent temperature fluctuations.
Innovation Solution
Incorporating a liquid accumulator with a cooling heat exchanger that allows for efficient heat exchange between high-temperature gaseous and low-temperature liquid refrigerants, and a bypass valve control method to adjust the refrigerant temperature at the condenser inlet, ensuring a stable temperature difference of 6 K to 10 K between the evaporation and condensation parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the gaseous refrigerant is cooled only by the liquid accumulator in the prior art, then the system structure remains simple, but the temperature difference between the refrigerant in the condensation part and evaporation part of the evaporative condenser becomes extremely high and unstable (up to 50 K), causing damage to the evaporative condenser
Solution Approach 1:
The cooling function is segmented into two stages: the liquid accumulator provides preliminary cooling of the gaseous refrigerant, and a dedicated cooling heat exchanger provides further cooling. This segmentation allows each component to specialize in a specific cooling task, achieving better temperature control and protecting the evaporative condenser from excessive temperature differences while maintaining reasonable system complexity
Solution Approach 2:
The cooling heat exchanger acts as an intermediary component between the liquid accumulator and the evaporative condenser. It mediates the temperature adjustment process by providing an additional cooling stage, ensuring that the refrigerant temperature entering the evaporative condenser is properly controlled and preventing direct thermal shock to the condenser
2Device complexity
If no cooling heat exchanger is added in the liquid accumulator, then the device complexity is low, but the temperature difference between evaporation and condensation parts reaches extremely high values (up to 50 K), damaging the evaporative condenser
Solution Approach 1:
The cooling heat exchanger performs preliminary cooling action on the gaseous refrigerant before it enters the evaporative condenser. By pre-cooling the refrigerant in the liquid accumulator and cooling heat exchanger, the system prepares the refrigerant at an appropriate temperature, preventing the harmful extreme temperature difference from occurring at the evaporative condenser
Solution Approach 2:
The cooling heat exchanger provides beforehand cushioning by absorbing excess heat from the gaseous refrigerant before it reaches the evaporative condenser. This cushioning effect prevents thermal shock and fatigue aging of the welds in the evaporative condenser by ensuring the temperature difference remains within acceptable ranges (6-10 K)
3Device complexity
If the refrigerant temperature at the condenser inlet is not controlled, then the control system remains simple, but the temperature difference fluctuates frequently and reaches over 40 K, causing fatigue aging and damages to welds
Solution Approach 1:
The control system uses feedback from temperature sensors to monitor the refrigerant temperature at the condenser inlet and adjusts the bypass valve opening degree accordingly. This feedback mechanism maintains the temperature difference within the desired range (6-10 K) by dynamically adjusting the refrigerant flow, ensuring stability and preventing fatigue damage to the evaporative condenser
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
The solution significantly reduces the workload on the downstream evaporative condenser, extends its service life, and maintains system performance by ensuring a stable and reduced temperature difference, thereby preventing fatigue and maintaining efficient heat exchange.
Implementation Method 1
a cooling heat exchanger disposed in the liquid accumulator housing... efficient heat exchange between high-temperature gaseous and low-temperature liquid refrigerants
Implementation Method 2
the refrigerant in the high temperature stage part is evaporated to condense the refrigerant in the low temperature stage part
Implementation Method 3
the refrigerant in the high temperature stage part is evaporated to condense the refrigerant in the low temperature stage part
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A liquid accumulator (210) for heat exchange system, comprising: a liquid accumulator housing (215) provided with an air inlet (211), an air outlet (212), and a liquid inlet (213); and a cooling heat exchanger (214) disposed in the liquid accumulator housing, wherein the cooling heat exchanger comprises an inlet end (214a), a main body part (214c), and an outlet end (214b) in sequence; the inlet end of the cooling heat exchanger connected to the air inlet on the liquid accumulator housing; and the outlet end of the cooling heat exchanger arranged to be higher than a working liquid level of a refrigerant in the liquid accumulator. A high-temperature gaseous refrigerant that enters the liquid accumulator can fully exchange heat with a low-temperature liquid refrigerant in the liquid accumulator under guidance of the cooling heat exchanger, so that refrigerant is cooled before leaving the liquid accumulator, and can be further cooled in a downstream evaporative condenser.