Cascading Heat Pump Water Heater for Low-Ambient Operation
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Solution Overview
Problem
Heat pump water heater systems are limited in their ability to effectively heat water in low ambient temperatures, leading to inefficiencies and higher costs, especially in cooler climates, as they require operating multiple compressors to maintain heating capacity.
Innovation Solution
A heat pump water heater system with two compressors operating at different pressures, a preheater, and a condenser, controlled by sensors and valves to optimize refrigerant flow based on ambient temperature, allowing efficient heating in both cool and warm climates by selectively using each compressor as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If two heat pumps are arranged in a cascading configuration to heat water in cool climates, then the heating capacity is sufficient for low ambient temperatures, but the system becomes more expensive to manufacture and operate, and efficiency decreases in warm climates
Solution Approach 1:
The system divides the heating function into two separate heating circuits: a first heating circuit with a first heat pump for normal temperature heating, and a second heating circuit with a second heat pump for low-temperature heating. This segmentation allows each heat pump to be optimized for its specific operating range, with the first heat pump handling warm climate conditions and the second heat pump activated only when ambient temperature drops below a threshold, thus maintaining simplicity in warm climates while providing sufficient capacity in cold climates.
2Temperature
If two compressors are operated simultaneously in a cascading heat pump system, then water can be heated to sufficient temperatures in cool climates, but energy consumption and operating costs increase
Solution Approach 1:
The system dynamically adjusts the operation of compressors based on ambient temperature conditions. A control mechanism monitors ambient temperature and selectively activates only the necessary compressor: the first compressor operates in warm climates, while the second compressor is activated only when ambient temperature falls below a predetermined threshold. This dynamic operation prevents simultaneous operation of both compressors, thereby reducing energy consumption and operating costs while still achieving sufficient water heating temperature in cool climates.
3Use of energy by moving object
If a single heat pump is used in warm climates, then the system operates efficiently, but it cannot sufficiently heat water in low ambient temperature conditions
Solution Approach 1:
The system is designed with multi-functionality to handle different climate conditions. The first heat pump serves as the primary heating device for efficient operation in warm climates. The second heat pump is incorporated as a supplementary device that activates only when ambient temperature drops below a threshold. This universal design allows the system to maintain high operating efficiency in warm climates using only the first heat pump, while gaining the capability to sufficiently heat water in low ambient temperature conditions by activating the second heat pump.
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
The system efficiently heats water in low ambient temperatures while reducing energy consumption and costs by operating only the necessary compressor, maintaining efficiency across varying climate conditions.
Implementation Method 1
an evaporator configured to facilitate heat exchange between ambient air and a refrigerant
Implementation Method 2
a preheater configured to receive the refrigerant at the first pressure from the first compressor and facilitate heat exchange between the refrigerant at the first pressure and water
Implementation Method 3
a condenser configured to receive the refrigerant at the second pressure from the second compressor and facilitate heat exchange between the refrigerant at the second pressure and the water
Implementation Method 4
a first compressor configured to compress the refrigerant to a first pressure, and a second compressor configured to compress the refrigerant to a second pressure. The second pressure can be greater than the first pressure.
Data Source
AI summary
The disclosed technology includes devices, systems, and methods for heat pump systems configured to operate in low ambient temperatures. The disclosed technology can include a heat pump water heater system having an evaporator, a first compressor configured to compress refrigerant to a first pressure, and a second compressor configured to compress the refrigerant to a second pressure. The second pressure can be greater than the first pressure. The heat pump water heater system can include a preheater configured to receive the refrigerant at the first pressure and heat water and a condenser configured to receive the refrigerant at the second pressure and heat water. The water can be passed through the preheater before being passed through the condenser.