Method and system for heating tap water
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Solution Overview
Problem
Existing methods for heating tap water in buildings using heat pumps are inefficient due to a low coefficient of performance, especially when achieving a large temperature increase, and often require high pressure levels with refrigerants like carbon dioxide.
Innovation Solution
A stepwise heating method where tap water is heated in stages using condensation heat from a heat pump, with reheated water circulated back to maintain temperature increases, combined with post-heating using hot gas heat exchanger to achieve the desired temperature efficiently, avoiding direct mixing of refrigerants with tap water.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If heating water temperature is increased to achieve large temperature difference for tap water heating, then heating efficiency improves, but coefficient of performance of heat pump decreases
Solution Approach 1:
The heating process is divided into multiple stages: first heating the heating water to a high temperature (e.g., 80-90°C) to achieve large temperature difference and high heating efficiency, then using this pre-heated water to heat the tap water in the tank. This segmentation allows the heat pump to operate at optimal temperatures while still achieving the required tap water heating effect.
Solution Approach 2:
Heating water is introduced as an intermediary medium between the heat pump refrigerant and the tap water. The heat pump heats the heating water, which then circulates through the tank to heat the tap water indirectly. This intermediary approach allows the system to achieve large temperature differences without directly exposing the refrigerant to tap water, maintaining high coefficient of performance.
2Loss of energy
If CO2 refrigerant is used to achieve high coefficient of performance, then energy efficiency improves, but system complexity and pressure requirements increase
Solution Approach 1:
The patent uses conventional refrigerants instead of CO2, accepting slightly lower coefficient of performance in exchange for using simpler, more readily available components and avoiding the technical difficulties associated with CO2 systems. This trade-off prioritizes ease of implementation and lower system complexity over maximum energy efficiency.
Solution Approach 2:
The system changes the operating parameters of the heat pump to work efficiently with conventional refrigerants by controlling the heating water temperature within specific ranges (80-90°C) and optimizing the circulation rates, thereby achieving satisfactory energy efficiency without requiring CO2-specific high-pressure components.
3Device complexity
If direct heating of tap water is implemented, then system simplicity improves, but risk of refrigerant mixing with tap water increases
Solution Approach 1:
Heating water serves as an intermediary fluid that transfers heat from the refrigerant to the tap water without direct contact between the two. The heating water circulates in a closed loop through the tank, absorbing heat from the refrigerant side and releasing it to the tap water side, thereby eliminating refrigerant mixing risk while maintaining system functionality.
Solution Approach 2:
The harmful element (refrigerant) is extracted from direct contact with the tap water by separating the heating functions into distinct circuits. The refrigerant remains confined to the heat pump and heating water circuit, while the tap water is heated indirectly through the heating water circulation, thus removing the source of potential contamination.
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 significantly enhances the overall coefficient of performance, allowing for efficient heating of tap water to the required temperature while maintaining regular pressure levels and avoiding technical difficulties associated with CO2 refrigerants.
Implementation Method 1
heating step wherein incoming tap water is heated with condensation heat released by a heat pump into heating water at its condenser
Implementation Method 2
the tap water which has been heated this way is conveyed into a tap water tank
Implementation Method 3
A stepwise heating method where tap water is heated in stages using condensation heat from a heat pump, with reheated water circulated back to maintain temperature increases
Implementation Method 4
combined with post-heating using hot gas heat exchanger to achieve the desired temperature efficiently
Data Source
Figure 1
AI summary
In a method for heating tap water (15) of a building, incoming tap water is heated with condensation heat released by a heat pump (2) into heating water (5) at its condenser (3), and the tap water which has been heated this way is conveyed into a tap water tank (11) to be conveyed further for use. According to the invention, tap water is heated in said heating step with the heat pump in such a way that the temperature increase provided between heated and incoming tap water only corresponds to a part of the targeted total temperature difference, and said heating step is repeated using, as incoming tap water, the tap water that has already been heated in a previous heating step and that is conveyed from the lower part of the tap water tank (11), and by conveying back the tap water that has been reheated this way to the upper part of the tap water tank, until the desired temperature of tap water has been reached, and when conveying tap water for use from the tap water tank, it is heated with hot water, which is heated with heat released by hot gas (4) of a heat pump.