Multi-Temperature Level Heat Pump Water Heaters (HPWH)
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Solution Overview
Problem
Heat pump water heaters (HPWH) face efficiency drops in high temperature and pressure lift conditions, especially in cold climates, due to the large temperature difference between heat rejection/ejection and the heat source, leading to increased energy consumption.
Innovation Solution
Implementing a cascaded fluid circuit with thermally connected HP circuits operating at different pressure differentials, allowing each circuit to have separate refrigerants, compressors, and heat exchangers, and incorporating vapor injection for enhanced efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single HP circuit operates at high temperature and pressure lift conditions, then hot water supply is achieved, but efficiency drops due to large temperature difference between heat rejection and heat source
Solution Approach 1:
The patent divides the single HP circuit into two separate HP circuits operating at different pressure differentials. The first HP circuit operates at a higher pressure differential for high-temperature hot water supply, while the second HP circuit operates at a lower pressure differential for lower-temperature hot water supply or preheating. This segmentation allows each circuit to operate within optimal efficiency ranges, reducing overall energy consumption.
Solution Approach 2:
The system changes the operating parameters (pressure differential, temperature levels) of the HP circuits based on demand conditions. By operating multiple circuits at different parameter sets simultaneously or selectively, the system optimizes efficiency across varying load conditions while meeting different temperature requirements.
2Adaptability or versatility
If a single HP circuit is used, then system simplicity is maintained, but operational flexibility and efficiency at different temperature levels are limited
Solution Approach 1:
The patent segments the HP system into multiple independent circuits, each capable of operating autonomously. This allows the system to adapt to different operational requirements by activating only the necessary circuits, providing flexibility while managing complexity through modular design.
Solution Approach 2:
Each HP circuit is designed to perform multiple functions - the first circuit can provide high-temperature hot water supply or preheat water for the second circuit, while the second circuit can independently provide lower-temperature hot water supply. This multi-functionality increases adaptability without proportionally increasing system complexity.
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 improves efficiency by reducing compressor pressure lift, increasing refrigerant mass flow rate, and allowing independent control of multiple temperature levels, reducing energy consumption and extending operational range.
Implementation Method 1
a heat exchanger that thermally connects one HP circuit (e.g., a high pressure circuit or an upper circuit) to another HP circuit (e.g., a lower pressure circuit or a lower circuit) or an auxiliary refrigerant line to facilitate heat exchange between a first refrigerant or refrigerant flow flowing through the upper circuit and the second refrigerant or second refrigerant flow flowing through the lower circuit (or auxiliary refrigerant line)
Implementation Method 2
Heat pumps, and more specifically heat pump water heaters (HPWH) use electricity to move heat from one place to another (e.g., hot water supply) instead of generating heat directly. Generally, A HPWH pulls heat from the surrounding environment and transfers the heat (at a higher temperature) to heat water in a storage tank
Data Source
AI summary
A heat pump water heater system includes a water source providing water at a water source temperature to inlet water line(s). The system includes heat pump (“HP”) circuits that involve a heat exchanger, such as an upper HP circuit and a lower HP circuit or a main HP circuit and an auxiliary refrigerant line. The heat exchanger thermally connects the HP circuits and/or auxiliary refrigerant line to facilitate heat exchange between refrigerants flowing therethrough to allow the HP circuits to operate with different pressure differentials, improving efficiency. Heat is also be exchanged to water tanks thermally coupled to the inlet water line(s) and various HP circuit components such that outlet water lines can deliver water at a first temperature, a second temperature, or at an intermediate temperature between the two by mixing water from one or more tanks and/or inlet water lines.