Heat Pump Water Heater Control for High Outlet Temperature
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Solution Overview
Problem
Conventional heat pump water heaters struggle to maintain a higher hot water delivery temperature while controlling refrigerant condensing pressure, leading to inefficiencies and potential changes in refrigerant pipes due to varying saturation pressures with different refrigerants.
Innovation Solution
A water heater system that includes a heat pump apparatus with a controller that synchronizes the capacity control of the compressor and flow rate control of the water supply pump to maintain a higher hot water delivery temperature without increasing refrigerant condensing pressure, using a refrigerant/water heat exchanger and temperature detection means to adjust operations accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the condensing pressure of refrigerant is increased to obtain higher saturation temperature, then the hot water delivery temperature can be increased, but the refrigerant pipe and system components must be changed to withstand higher pressure
Solution Approach 1:
The patent changes the operating parameters of the heat pump system by coordinating compressor capacity and water flow rate to maintain higher water outlet temperatures without increasing condensing pressure beyond design limits. This allows the system to deliver hotter water using existing refrigerant pipes and components.
Solution Approach 2:
The patent implements dynamic control where the compressor capacity and water pump flow rate are adjusted in coordination based on operating conditions. This dynamic adjustment allows the system to maintain optimal temperature differential across the heat exchanger while keeping condensing pressure stable, enabling higher delivery temperatures without pressure increases.
2Ease of operation
If the water temperature of water inlet side of refrigerant/water heat exchanger is controlled separately from water outlet temperature, then the control is simpler, but the condensing pressure increases
Solution Approach 1:
The patent uses feedback control where the water outlet temperature is measured and used to adjust the water flow rate in coordination with compressor capacity. This feedback mechanism ensures that the temperature differential across the heat exchanger is maintained within optimal ranges, preventing excessive condensing pressure while achieving the desired outlet temperature.
Solution Approach 2:
The patent performs preliminary control actions by adjusting the water flow rate based on predicted heating requirements and compressor capacity settings. This preliminary adjustment prevents the water inlet temperature from rising too much, thereby avoiding the need to increase condensing pressure to maintain outlet temperature.
3Productivity
If the capacity of compressor is increased to heat water to higher temperature, then the heating capacity is improved, but the condensing pressure increases
Solution Approach 1:
The patent changes the operational parameters by coordinating compressor capacity with water flow rate. Instead of simply increasing compressor capacity alone, the system adjusts both parameters together to maintain optimal temperature differential, achieving higher heating capacity without proportionally increasing condensing pressure.
Solution Approach 2:
The patent implements dynamic coordination between compressor capacity control and water pump flow rate control. This dynamic adjustment allows the system to increase heating capacity by optimizing the balance between heat input and water flow, maintaining condensing pressure within acceptable limits while improving productivity.
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
Enables the heating of water to a higher temperature while stabilizing refrigerant condensing pressure, effectively managing temperature and pressure dynamics to ensure efficient and stable operation.
Implementation Method 1
a refrigerant/water heat exchanger and temperature detection means to adjust operations accordingly
Implementation Method 2
a capacity control unit that controls the capacity of a compressor
Implementation Method 3
a flow rate control unit that controls the flow rate of water flowing in the water circuit by driving of a water supply pump
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
[Object] To obtain a water heater that is capable of delivering hot water at a higher temperature, while suppressing an increase in the condensing pressure of a refrigerant. [Solution] A refrigerant circuit includes a compressor 2 that compresses a refrigerant, the capacity of the compressor 2 being variable; a refrigerant/water heat exchanger 12 that exchanges heat between the refrigerant and water; a decompression device 4 that decompresses the refrigerant by opening degree adjustment; and an evaporator 5 that evaporates the refrigerant by heat exchange, and the compressor 2, the refrigerant/water heat exchanger 12, the decompression device 4, and the evaporator 5 are connected by pipes. A refrigerant circuit further includes a water supply pump 7 that forms a flow of water passing through the refrigerant/water heat exchanger 12, the water flow rate of the water supply pump 7 being variable; water inlet temperature detection means 8 for detecting a water inlet temperature of the water flowing into the refrigerant/water heat exchanger 12; water outlet temperature detection means 10 for detecting the water outlet temperature of the water flowing out of the refrigerant/water heat exchanger 12; and a controller 15 that performs fixed control for the capacity of the compressor 2 when the water inlet temperature is determined to have reached a preset first temperature, and that performs variable control for the water flow rate of the water supply pump 7 so that the water outlet temperature is made equal to a second temperature, are provided.