Heat Pump Defrost Control for Quieter Hot Water Supply
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Solution Overview
Problem
In hot water supply apparatuses without internal heat exchangers, the refrigerant becomes wet and denser during defrosting, leading to increased sound due to higher flow speed through the pressure reducing device.
Innovation Solution
Controlling the compressor frequency and pressure reducing device opening during defrosting to reduce refrigerant flow speed into the pressure reducing device, thereby minimizing sound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pressure reducing device is fully opened during defrosting operation, then the defrosting effectiveness is improved, but the refrigerant flow speed increases causing excessive noise
Solution Approach 1:
The patent applies parameter changes by adjusting the opening degree of the pressure reducing device from fully opened to a controlled partial opening during defrosting operation. This changes the refrigerant flow characteristics, reducing flow speed and thereby suppressing noise while maintaining sufficient defrosting effectiveness. The control unit dynamically adjusts this parameter based on operational conditions.
2Power
If the compressor operating frequency is increased, then the heating capacity is improved, but the refrigerant flow speed into the pressure reducing device increases causing noise
Solution Approach 1:
The patent applies dynamics by making the compressor operating frequency adjustable rather than fixed. The control unit dynamically modifies the compressor frequency during defrosting operation to an appropriate level that provides sufficient heating capacity while preventing excessive refrigerant flow speed and associated noise. This dynamic adjustment allows optimization of both performance and noise characteristics.
3Device complexity
If no internal heat exchanger is used to reduce cost, then the device complexity is reduced, but the high-pressure-side pressure rises excessively during defrosting
Solution Approach 1:
The patent applies parameter changes by adjusting the opening degree of the pressure reducing device during defrosting operation. This parameter adjustment helps regulate the high-pressure-side pressure that would otherwise rise excessively when no internal heat exchanger is present. By controlling the pressure reducing device opening, the system maintains pressure within acceptable ranges without requiring additional hardware.
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 approach effectively suppresses the increase in refrigerant passing sound during defrosting operations by adjusting the compressor frequency and pressure reducing device opening, enhancing operational efficiency.
Implementation Method 1
a compressor (11) configured to compress the refrigerant
Implementation Method 2
a water heat exchanger (12) configured to heat water by heat exchange with the refrigerant
Implementation Method 3
an air heat exchanger (14) configured to heat air by heat exchange with the refrigerant
Implementation Method 4
a pressure reducing device (13) configured to reduce pressure of the refrigerant
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A hot water supply apparatus includes a heat pump unit that includes a compressor, a water heat exchanger, a pressure reducing device, and an air heat exchanger and that is configured to heat water flowing through the water heat exchanger, a compressor control unit configured to control an operating frequency of the compressor, and a pressure reducing device control unit configured to control an opening degree of the pressure reducing device. Upon start of a defrosting operation in which the pressure reducing device is opened, supply of the water to the water heat exchanger is stopped, and refrigerant discharged from the compressor is caused to flow into the air heat exchanger, at least one of the operating frequency of the compressor and the opening degree of the pressure reducing device is controlled by the compressor control unit or the pressure reducing device control unit, thereby reducing flow speed of the refrigerant flowing into the pressure reducing device.