Precooler-based transcritical CO<sub>2 </sub>heat pump system and control method of waterway two-way valve thereof
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Solution Overview
Problem
Transcritical CO2 heat pump systems face efficiency issues due to high return water temperatures and challenges in defrosting, including low defrosting efficiency and temperature fluctuations in the heating water supply, which affect system performance and operational efficiency.
Innovation Solution
A precooler-based transcritical CO2 heat pump system with a control method that automatically switches between heating and defrosting modes using sensors and a programmable logic controller, incorporating a precooler system to reduce inlet water temperature and maintain stable water temperature during defrosting by bypassing the precooling system evaporator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If high temperature return water is directly introduced into the gas cooler to exchange heat with CO2 gas, then the heating system can operate continuously, but the temperature of cooled CO2 gas becomes high, reducing heat supply potential and system operation efficiency
Solution Approach 1:
The water circulation system is divided into two separate loops: a first water circulation system that continuously exchanges heat with CO2 in the gas cooler, and a second water circulation system that pre-cools return water before it enters the gas cooler. This segmentation allows the first system to maintain continuous heating operation while the second system improves CO2 cooling efficiency by providing lower temperature return water.
2Reliability
If the heat pump system uses conventional defrosting method with hot air discharged into evaporator, then the system can defrost, but the defrosting time is longer and causes temperature fluctuations in heating water supply
Solution Approach 1:
A third water circulation system is introduced as an intermediary medium for defrosting. Instead of using hot air that causes temperature fluctuations, this system circulates water through a third water cooler that directly contacts the evaporator, providing controlled and stable defrosting heat while maintaining heating water temperature stability.
3Reliability
If the heat pump system cannot carry out conventional heat supply during defrosting process, then defrosting can be performed, but the average water temperature in the waterway circulation system decreases and temperature fluctuation occurs
Solution Approach 1:
The water circulation system is segmented into three independent systems that can operate simultaneously or independently. During defrosting, the third water circulation system activates to provide defrosting heat while the first and second systems continue to maintain heating water temperature, ensuring both defrosting function and temperature stability are achieved concurrently.
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 solution enhances the heat production capacity and energy efficiency of the transcritical CO2 heat pump system, ensures continuous heat supply during defrosting, and accurately controls the defrosting process to prevent temperature fluctuations, thereby improving operational reliability and efficiency.
Implementation Method 1
a precooler system to reduce inlet water temperature
Implementation Method 2
CO2 without a phase change process releases heat to the circulating water with a huge temperature slip in the gas cooler, so that the circulating water can be directly raised from a low-temperature condition to a high-temperature condition exceeding 80° C.
Implementation Method 3
maintain stable water temperature during defrosting by bypassing the precooling system evaporator
Data Source
AI summary
The present disclosures discloses a precooler-based transcritical CO2 heat pump system and a control method of a waterway two-way valve thereof, in which a transcritical CO2 heat pump system is assisted by a precooler system. A circulating waterway is divided into two parts in the system through a three-way diversion valve and a three-way confluence valve and is connected to a waterway bypass valve through a waterway two-way regulating valve. An ambient temperature sensor, an evaporation fin temperature sensor and an evaporation pressure sensor are provided, and a programmable logic controller is used as a core for acquisition, operation and control.