Heat Source Heat Exchanger Segmentation for Defrost Time Control
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Solution Overview
Problem
Conventional refrigerant cycle apparatuses prolong defrost time unnecessarily by terminating defrost operation based on downstream refrigerant temperature, even when the sub heat exchange unit does not require defrosting, due to its higher temperature during normal operation.
Innovation Solution
A refrigerant cycle apparatus with a flow direction switching mechanism that allows the refrigerant to flow in a direction opposite to normal operation, incorporating a first and second defrost control mode, where the first mode terminates defrost based on the main heat exchange unit's temperature and the second mode based on the sub heat exchange unit's temperature, ensuring timely termination of defrost operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If defrost operation is terminated based on downstream refrigerant temperature, then the entire heat exchange unit temperature is monitored, 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 main heat exchange unit and sub heat exchange unit, with separate temperature measurement and separate defrost termination judgment for each unit. This allows independent assessment of defrost needs for each segment, preventing unnecessary prolonged defrost operation when only one unit requires defrosting.
Solution Approach 2:
Different defrost termination criteria are applied to different parts of the heat exchange unit based on their specific conditions. The main heat exchange unit uses one temperature threshold while the sub heat exchange unit uses another threshold, allowing localized optimization of defrost operation duration.
2Temperature
If the sub heat exchange unit is disposed upstream of the pressure loss portion, then the refrigerant temperature in the sub heat exchange unit is higher during normal operation, but the sub heat exchange unit may still require defrosting in some cases
Solution Approach 1:
Temperature sensors continuously monitor the refrigerant temperature in both the main and sub heat exchange units, providing feedback to the control unit. Based on this real-time feedback, the control unit dynamically adjusts the defrost operation duration and termination criteria for each unit, ensuring reliable defrost coverage even when temperature conditions vary.
3Device complexity
If a single temperature measurement point is used for defrost termination, then the control system is simple, but it cannot accurately determine when defrosting is complete for different heat exchange units
Solution Approach 1:
The temperature measurement system is segmented into multiple independent measurement points, with one sensor dedicated to the main heat exchange unit and another to the sub heat exchange unit. This segmentation enables accurate detection of defrost completion for each unit independently while maintaining relatively simple control logic.
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 prevents unnecessary extension of defrost time by accurately determining the need for defrosting at the sub heat exchange unit, ensuring efficient operation and reducing frost accumulation.
Implementation Method 1
a compressor (12) that compresses a refrigerant
Implementation Method 2
an expansion mechanism (18) that decompresses the refrigerant
Implementation Method 3
a first heat exchange unit (20) that causes heat exchange between the refrigerant and a heat exchange target
Implementation Method 4
causing a refrigerant to flow in a direction opposite to a direction during normal operation, for removal of frost adhering to a heat exchange unit
Data Source
Figure 1
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Figure 3
AI summary
Provided is a refrigerant cycle apparatus configured to suppress extension of defrost time. A refrigerant cycle apparatus (100) includes: a refrigerant circuit (80) including a compressor (12), a heat source heat exchanger (20) having a main heat exchange unit (22), a sub heat exchange unit (28), and a pressure loss portion (25) disposed between the main heat exchange unit and the sub heat exchange unit, an expansion mechanism (18), a utilization heat exchanger (62), and a flow direction switching mechanism (14) configured to switch a flow direction of a refrigerant; a first temperature sensor (92c) configured to measure first refrigerant temperature (T1) between the main heat exchange unit and the pressure loss portion; a second temperature sensor (92d) configured to measure second refrigerant temperature (T2) between the pressure loss portion and the expansion mechanism; and a controller (70) configured to control the flow direction switching mechanism (14) 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 (T1) and a control mode of terminating the defrost operation based on the second refrigerant temperature (T2).