Cascade Heat Pump Flow Control for Stable High-Temperature Water
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional heat pump systems face challenges in efficiently and stably generating high-temperature water due to high compressive pressures and the need for balanced evaporation and condensation heat quantities in cascade refrigeration cycles, particularly with natural refrigerants like CO2 and HC-based refrigerants.
Innovation Solution
A heat pump system with a high temperature heating side refrigerant circuit and a low temperature heating side refrigerant circuit, where the evaporating pressure and temperature of the refrigerant are stabilized through a control unit that adjusts the flow rate and operation of valves and pumps, allowing for efficient heating of water to high temperatures without complex control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a cascade refrigeration cycle is used to generate high-temperature hot water, then high efficiency can be achieved, but the evaporation heat quantity of the high order side evaporator and the heating quantity of the low order side condenser must be balanced at all times, making it difficult to stably generate high-temperature water
Solution Approach 1:
The system divides the heating load into two independent temperature zones: a high-order side circuit for high-temperature hot water and a low-order side circuit for low-temperature hot water. Each circuit operates independently with its own evaporator and condenser, eliminating the need for heat balance between circuits. This segmentation allows each circuit to be optimized for its specific temperature range without being constrained by the other circuit's thermal requirements.
Solution Approach 2:
The patent introduces an intermediary heat exchanger that allows the high-order side evaporator to be heated by the low-order side condenser when the low-order side produces excess heat. This intermediary mechanism enables flexible heat transfer between circuits only when beneficial, without requiring continuous balance, thus improving stability while maintaining efficiency.
2Object-affected harmful factors
If natural refrigerant such as CO2 is used in a heat pump cycle, then environmental friendliness is improved, but the compressive pressure becomes extremely high, creating technical and cost problems
Solution Approach 1:
The system uses different refrigerants for the high-order side and low-order side circuits. The low-order side can use environmentally friendly natural refrigerants like CO2 at lower pressures, while the high-order side uses refrigerants suitable for high-temperature operation. This segmentation allows each circuit to use the most appropriate refrigerant for its specific requirements, reducing the need for extremely high compressive pressures throughout the entire system.
Solution Approach 2:
The patent changes the operating parameters of different refrigerant circuits to match their optimal performance ranges. By operating the low-order side at lower temperatures and pressures where natural refrigerants excel, and the high-order side at higher temperatures where synthetic refrigerants perform better, the system achieves environmental friendliness without requiring extremely high compressive pressures across all components.
3Use of energy by moving object
If HC-based refrigerant is used to achieve high efficiency, then energy efficiency is improved, but the refrigerant becomes combustible, introducing safety concerns
Solution Approach 1:
The system segments the refrigerant circuits based on safety requirements. The low-order side circuit, operating at lower temperatures and pressures, can safely use HC-based refrigerants that provide high energy efficiency. The high-order side circuit uses refrigerants with lower flammability. This segmentation allows the system to achieve high overall efficiency while managing combustion risks in the specific zone where HC refrigerant is used.
Solution Approach 2:
The patent applies different safety characteristics to different parts of the system based on local requirements. In the low-order side where temperatures and pressures are lower, HC refrigerants with high efficiency are used. In the high-order side where safety concerns are greater, less flammable refrigerants are used. This local differentiation of refrigerant properties optimizes efficiency where safe and reduces combustion risks where necessary.
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 and stably generates high-temperature water by maintaining optimal evaporating pressures and temperatures, improving the balance between refrigerant circuits and reducing operational complexity.
Implementation Method 1
a low temperature heating side refrigerant circuit B in which a low temperature heating side compressor 9, a low temperature heating side condenser 4, a low temperature heating side expansion valve 12 and a low temperature heating side evaporator 6 are successively connected by a refrigerant pipe; and a high temperature heating side refrigerant circuit A in which a high temperature heating side compressor 8, a high temperature heating side condenser 1, a high temperature heating side expansion valve 11 and a high temperature heating side evaporator 2 are successively connected by a refrigerant pipe
Implementation Method 2
the first pipe configured to connect a low temperature side liquid supply port, the low temperature heating side condenser 4, and the high temperature heating side evaporator 2 in this order, thereby to circulate the liquid; and a pump provided in the first pipe and configured to feed the liquid heated in the low temperature heating side condenser 4 to the high temperature heating side evaporator 2
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A heat pump system of the present invention includes: a low temperature heating side refrigerant circuit; a high temperature heating side refrigerant circuit; a first pipe to connect a low temperature side liquid supply port, a low temperature heating side condenser, and a high temperature heating side evaporator in this order, thereby to circulate liquid; a second pipe configured to connect a high temperature side liquid supply port and a high temperature heating side condenser in this order, thereby to circulate the liquid; a pump provided in the first pipe and configured to feed the liquid heated in the low temperature heating side condenser to the high temperature heating side evaporator; a control valve provided in the first pipe between the low temperature heating side condenser and the high temperature heating side evaporator and configured to control a flow rate of the liquid circulated inside the first pipe; and a control unit configured to control at least one of the pump and the control valve, and control a flow rate of the liquid fed from the low temperature heating side condenser to the high temperature heating side evaporator.