Subcooling Heat Exchanger Control During Refrigeration Cycle Switching
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Solution Overview
Problem
The refrigeration apparatus experiences increased thermal stress on the subcooling heat exchanger when switching from the first refrigeration cycle to the second, due to a relatively high-temperature refrigerant flowing into the subcooling heat exchanger, which can cause damage.
Innovation Solution
A refrigeration apparatus with a switching mechanism that reduces the cooling capability of the subcooling heat exchanger before switching cycles, using a regulation mechanism including an expansion valve and control unit to manage the flow rate and pressure of the refrigerant, thereby reducing thermal stress by raising the temperature of the refrigerant in the subcooling heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refrigeration apparatus switches from the first refrigeration cycle to the second refrigeration cycle, then the utilization heat exchanger serves as a radiator for defrosting operation, but the thermal stress on the subcooling heat exchanger increases due to high-temperature refrigerant flowing into it
Solution Approach 1:
The control unit reduces the cooling capability of the subcooling heat exchanger before the cycle switching occurs. This preliminary action prevents the thermal stress problem by adjusting the refrigerant temperature in advance, so that when high-temperature refrigerant flows into the subcooling heat exchanger during defrosting operation, the temperature difference and resulting thermal stress are minimized.
Solution Approach 2:
The control unit changes the operating parameters of the subcooling heat exchanger by reducing its cooling capability before cycle switching. This parameter change involves adjusting the refrigerant flow or heat exchange conditions to raise the refrigerant temperature, thereby reducing the thermal stress that would occur during the transition to defrosting operation.
2Temperature
If the subcooling heat exchanger maintains high cooling capability, then the refrigerant is effectively cooled during the first refrigeration cycle, but the thermal stress increases when switching to the second refrigeration cycle
Solution Approach 1:
Before switching to the second refrigeration cycle, the control unit performs a preliminary action to reduce the cooling capability of the subcooling heat exchanger. This ensures that the refrigerant temperature is adjusted in advance, preventing excessive thermal stress while maintaining effective cooling during the first cycle through normal operation.
Solution Approach 2:
The cooling capability of the subcooling heat exchanger is made dynamic rather than static. The control unit adjusts the cooling capability based on the operating cycle - maintaining high cooling capability during the first refrigeration cycle for effective refrigerant cooling, then reducing it before switching to the second cycle to prevent thermal stress. This dynamic adjustment resolves the contradiction between cooling efficiency and thermal stress prevention.
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 effectively reduces thermal stress on the subcooling heat exchanger, preventing damage and ensuring reliable operation during cycle switching.
Implementation Method 1
a subcooling heat exchanger (40) having a first channel (40a) connected to a middle portion of a liquid pipe (32, 33) through which a liquid refrigerant in the heat source circuit (11) flows, and a second channel (40b) through which a heating medium for cooling the refrigerant in the first channel (40a) flows
Implementation Method 2
cooling the refrigerant in the first channel (40a)
Implementation Method 3
through which a heating medium for cooling the refrigerant in the first channel (40a) flows
Implementation Method 4
a regulation mechanism including an expansion valve (26) connected to an upstream side of the second channel (40b) and a control unit (101) configured to control an opening degree of the expansion valve (26)
Data Source
Figure 1
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AI summary
A heat source unit (10) including a heat source circuit (11) is connected to a utilization unit (50) to constitute a refrigerant circuit (2) that performs a refrigeration cycle. The heat source unit (10) includes a switching mechanism (24) that switches the refrigeration cycle between a first refrigeration cycle and a second refrigeration cycle, and a subcooling heat exchanger (40) having a first channel (40a) and a second channel (40b) through which a heating medium for cooling a refrigerant in the first channel (40a) flows. The heat source unit (10) further includes a regulation mechanism (80) configured to perform a first operation of reducing a capability of the second channel (40b) of cooling the refrigerant in the first channel (40a) before switching from the first refrigeration cycle to the second refrigeration cycle.