Heat Pump Water Temperature Control for Reduced Compressor Cycling
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Solution Overview
Problem
Conventional heat pump hot water heating systems with AC-driven water circulation pumps face inefficiencies and reduced lifespan due to on/off cycle operations, especially when the compressor's minimum supply capacity exceeds the heat transfer or removal demand, leading to increased costs and complexity in control algorithms.
Innovation Solution
A hot and cold water air conditioning system that employs a controller to switch from on/off normal control to on/off restriction control, turning on the compressor when the water temperature falls below a second temperature value and turning it off when it reaches or exceeds a third temperature value higher than the target, thereby minimizing the compressor's operation frequency and reducing on/off cycle operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the compressor operation frequency is controlled to match the heat transfer demand, then the system efficiency is improved, but the compressor lifespan is reduced due to frequent on/off switching
Solution Approach 1:
The patent applies periodic action by intentionally allowing the compressor to operate in on/off cycles at minimum frequency rather than attempting to continuously match the heat transfer demand. This periodic operation pattern, while not perfectly efficient, prevents excessive frequent switching and extends compressor lifespan by maintaining operation above a minimum threshold frequency.
2Loss of energy
If the compressor minimum supply capacity is reduced to match small heat transfer demand, then the system efficiency is improved, but the compressor reliability deteriorates due to operation below minimum frequency
Solution Approach 1:
The patent applies parameter changes by adjusting the temperature differential parameters (first temperature differential and second temperature differential) based on the heat transfer demand. When demand is small, the system increases the temperature differential to allow the compressor to operate at minimum frequency without excessive on/off cycling, thus maintaining reliability while accepting reduced efficiency.
3Loss of energy
If the supply temperature is increased to match small heat transfer demand, then the system efficiency is improved, but the water temperature control precision deteriorates
Solution Approach 1:
The patent applies dynamics by making the temperature differential parameters dynamic rather than fixed. The first temperature differential is adjusted based on the heat transfer demand: when demand is large, a smaller differential is used for precise control; when demand is small, a larger differential is used to maintain efficiency while accepting reduced precision.
4Speed
If the compressor on/off cycle operation is increased to match fluctuating heat pump capacity, then the system responsiveness is improved, but the electric circuit parts lifespan is reduced due to repeated relay contact switching
Solution Approach 1:
The patent applies beforehand cushioning by establishing minimum frequency constraints and temperature differential buffers before excessive on/off cycling occurs. These pre-set parameters act as cushions that prevent the compressor from switching too frequently, thereby protecting relay contacts and electric circuit parts from repeated switching damage while still maintaining adequate system responsiveness.
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 restricts on/off cycle operations, enhancing the efficiency and extending the lifespan of the system by ensuring the compressor operates at a minimum frequency necessary, even when the supply capacity exceeds the heat transfer or removal demand, resulting in a high-efficiency and long-life air conditioning system.
Implementation Method 1
hot water heated with a refrigerant of the heat pump cycle via a heat exchanger
Implementation Method 2
a water circulation pump configured to circulate water inside the pipes
Data Source
AI summary
The hot and cold water air conditioning system includes a water temperature sensor configured to detect a temperature of water flowing out of the heat pump heat source apparatus by an operation of the water circulation pump, and a controller configured to perform, in a heating operation, on/off normal control that turns on a compressor when the water temperature detected by the water temperature sensor becomes lower than a target water temperature and turns off the compressor when the water temperature becomes higher than a first temperature value higher than the target water temperature, and to switch from the on/off normal control, upon repeating the on/off operation of the compressor at a minimum frequency necessary for an operation of the compressor in the on/off normal control, to on/off restriction control that turns on the compressor when the water temperature becomes lower than a second temperature value lower than the target water temperature and turns off the compressor when the water temperature becomes equal to or higher than a third temperature value higher than the target water temperature.