Heat Pump Defrost Termination Using Segmented Temperature Sensing
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Solution Overview
Problem
In refrigerant cycle apparatuses, the sub heat exchange unit may not need defrosting during normal operation, but existing methods terminate defrost operations based on downstream refrigerant temperature, leading to unnecessary prolongation of defrost time as the entire heat exchange unit, including the sub unit, rises in temperature.
Innovation Solution
A refrigerant cycle apparatus with a flow direction switching mechanism and temperature sensors to differentiate between normal and defrost operations, allowing termination of defrost based on specific temperature thresholds to prevent unnecessary extension of defrost time, particularly when the sub heat exchange unit does not require defrosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If defrost operation is terminated based on downstream refrigerant temperature, then the entire heat exchange unit temperature increases, but the defrost operation is unnecessarily prolonged when the sub heat exchange unit does not need defrosting
Solution Approach 1:
The heat exchange unit is divided into a main heat exchange unit and a sub heat exchange unit with different refrigerant flow paths. The defrost termination is segmented into two independent temperature monitoring systems: one for the main heat exchange unit and one for the sub heat exchange unit. This allows independent defrost termination judgment for each unit, preventing unnecessary prolongation of defrost time when the sub unit does not require defrosting.
Solution Approach 2:
Different termination criteria are applied to different parts of the system. The main heat exchange unit uses downstream refrigerant temperature for termination judgment, while the sub heat exchange unit uses upstream refrigerant temperature. This local differentiation ensures that defrost operation terminates promptly when the main unit is defrosted, without being extended by the sub unit's temperature changes.
2Temperature
If the refrigerant flows through the sub heat exchange unit upstream of the pressure loss portion, then the refrigerant temperature in the sub heat exchange unit is higher, but frost is less likely to form making defrosting unnecessary
Solution Approach 1:
The system dynamically switches refrigerant flow directions based on operational mode. During normal heating operation, refrigerant flows through the sub heat exchange unit upstream of the pressure loss portion, maintaining higher temperatures that prevent frost formation. During defrost operation, the flow direction reverses, allowing the main heat exchange unit to be defrosted while the sub unit's higher temperature naturally prevents frost issues.
Solution Approach 2:
The refrigerant flow path is segmented into two distinct units with different positions relative to the pressure loss portion. The sub heat exchange unit is positioned upstream where higher temperature refrigerant flows, creating a natural frost-resistant zone. The main heat exchange unit is positioned downstream where lower temperature refrigerant flows, making it susceptible to frost formation and requiring defrosting. This segmentation allows selective defrost operation.
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 suppresses unnecessary extension of defrost time by terminating the defrost operation based on the refrigerant temperature at the main heat exchange unit, ensuring efficient operation and reducing frost remnants at the sub heat exchange unit.
Implementation Method 1
The compressor compresses a refrigerant
Implementation Method 2
The expansion mechanism is disposed on the refrigerant flow path between the first heat exchange unit and the second heat exchange unit, and decompresses the refrigerant
Implementation Method 3
The first heat exchange unit includes a main heat exchange unit, a sub heat exchange unit
Implementation Method 4
for removal of frost adhering to the heat exchange unit which serves as a refrigerant heater (heat absorber) during the normal operation
Data Source
AI summary
A refrigerant cycle apparatus is configured to suppress extension of defrost time. The refrigerant cycle apparatus includes: a refrigerant circuit; a first temperature sensor configured to measure first refrigerant temperature between the main heat exchange unit and the pressure loss portion; a second temperature sensor configured to measure second refrigerant temperature between the pressure loss portion and the expansion mechanism; and a controller configured to control the flow direction switching mechanism to switch between normal operation and defrost operation. The controller has control modes for the defrost operation, including a control mode of terminating the defrost operation based on the first refrigerant temperature and a control mode of terminating the defrost operation based on the second refrigerant temperature.