Heat Pump Water Heater Mode Switching for Higher COP
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Solution Overview
Problem
Heat pump water heaters face inefficiencies in COP (coefficient of performance) due to differences in hot water flow rates between circulation and non-circulation heating systems, particularly when using refrigerants like R410A and CO2, where the optimal system depends on entering water temperature and refrigerant properties.
Innovation Solution
The system dynamically adjusts the hot water flow rate and operation mode between circulation and non-circulation heating based on temperature changes and thresholds, ensuring operation in the mode that provides the highest COP, using a valve mechanism to direct flow to the bottom or top of the tank and adjusting the circulation pump's flow rate accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the non-circulation heating system is used for the refrigerant such as R410A, then the system is simpler to operate, but the COP of the heat pump is considerably low for some entering water temperatures
Solution Approach 1:
The patent makes the heating system universal by incorporating both circulation and non-circulation heating capabilities within a single system. The control unit selects between circulation heating mode and non-circulation heating mode based on the entering water temperature and refrigerant type. This multi-functionality allows the system to achieve high COP when circulation mode is beneficial while maintaining operational simplicity through automated mode selection, resolving the contradiction between ease of operation and energy efficiency.
2Productivity
If the circulation heating system is used, then the heat exchange efficiency is improved, but the entering water temperature increases which decreases the COP
Solution Approach 1:
The patent implements feedback control by using a temperature detector to monitor the entering water temperature and using this information to adjust the circulation pump's flow rate. When the entering water temperature reaches or exceeds a predetermined value, the control unit reduces the flow rate to prevent excessive stirring in the storage tank. This feedback mechanism allows the system to maintain high heat exchange efficiency while preventing COP degradation, resolving the contradiction between productivity and energy efficiency.
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 enhances energy efficiency by selecting the operation mode that maximizes COP, regardless of refrigerant type or temperature changes, thereby improving the overall performance of the heat pump water heater.
Implementation Method 1
a heat pump unit (2); a hot water storage tank (5)... hot water heated by a heat pump unit is supplied to a hot water storage tank
Implementation Method 2
there is a refrigerant which condenses in a condenser, such as R410A, R134a, and R407C
Implementation Method 3
In the circulation heating system, heated hot water is supplied to the hot water storage tank at a relatively higher flow rate
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Energy efficiency is improved. A heat pump water heater 1 includes: a heat pump unit 2 including a refrigerant circuit 3 in which a refrigerant condensing in a condenser 22 circulates; and a hot water storage tank 5 which stores hot water heated in the condenser 22. An operation mode is selectable from a circulation heating mode in which heated hot water is supplied to the hot water storage tank at a first flow rate, and a non-circulation heating mode in which heated hot water is supplied to a top portion of the hot water storage tank 5 at a second flow rate lower than the first flow rate. The operation mode is switched between the circulation heating mode and the non-circulation heating mode based on the temperature of the refrigerant supplied to the condenser 22.