CO2 Heat Pump Pressure Control for 150°C Water Heating
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Solution Overview
Problem
High-temperature heat pumps operating with carbon dioxide as a refrigerant face challenges in achieving high hot water outlet temperatures efficiently due to unregulated coolant injection into the evaporator and lack of control over liquid carbon dioxide escape, leading to suboptimal performance figures, especially in industrial applications with higher outputs.
Innovation Solution
A high-temperature heat pump design incorporating at least two internal heat exchangers, a compressor, multiple gas coolers connected in series, a refrigerant collector, and a refrigerant injection valve, with control mechanisms to regulate refrigerant overheating and high pressure in the gas coolers, allowing precise control of hot water outlet temperatures and optimizing the coefficient of performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unregulated coolant injection is used into the evaporator, then device complexity is reduced, but performance figures become suboptimal due to inability to control refrigerant overheating and liquid carbon dioxide escape
Solution Approach 1:
The patent applies parameter changes by implementing electronic control of the expansion valve based on measured refrigerant temperature and pressure parameters. The control unit adjusts the valve opening degree dynamically to maintain optimal refrigerant overheating levels and prevent liquid carbon dioxide escape, thereby optimizing performance figures while managing device complexity through automated parameter adjustment.
Solution Approach 2:
The patent implements feedback control by using temperature sensors and pressure sensors to continuously monitor refrigerant conditions in the evaporator and gas cooler. The control unit processes this feedback information and adjusts the expansion valve position accordingly, enabling precise control of refrigerant flow, overheating, and pressure to achieve optimal performance.
2Temperature
If pressure in gas coolers is increased to achieve higher hot water outlet temperatures, then temperature output is improved, but coefficient of performance is reduced
Solution Approach 1:
The patent applies dynamics by making the gas cooler pressure adjustable rather than fixed. The system dynamically adjusts the pressure level in the gas coolers based on operational requirements, allowing optimization of the balance between achieving desired hot water outlet temperatures and maintaining acceptable coefficient of performance. This is achieved through controlled refrigerant flow regulation and pressure management in the transcritical cycle.
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 enables the achievement of high hot water outlet temperatures up to 150°C with improved performance figures by precisely controlling refrigerant overheating and pressure, minimizing the reduction in coefficient of performance, and enhancing energy efficiency in industrial heat generation and storage applications.
Implementation Method 1
heat is transferred from warmer carbon dioxide flowing back from the gas coolers into the evaporator to colder carbon dioxide exiting the evaporator
Implementation Method 2
heat pumps are almost always used to generate higher temperatures, they are inevitably operated in the transcritical range
Implementation Method 3
at least two internal heat exchangers, a compressor, one or more gas coolers connected in series
Implementation Method 4
the inlet of the refrigerant collector has a controllable expansion valve
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a high-temperature heat pump for warming a fluid, preferably water, to a temperature level upto 150°C, which is operated with carbon dioxide as a coolant in the transcritical range. Said heat pump comprises an evaporator (6), at least two inner heat exchangers (4, 5), a compressor (1), one or more serially connected gas coolers (2, 3), a coolant collector (7) and a coolant injection valve (8). In order to control the high pressure in the gas coolers (2, 3), the inlet of the coolant collector (7) is connected via a control valve (15) to the outlet of the serially connected gas cooler (2, 3) and the outlet of the coolant collector (7) is connected to the coolant injection valve (8). Very high pressure values can be attained by controlling the overheating of the coolant of the water pump, by means of the inflow of the coolant into the evaporator (6) and the high pressure in the gas coolers (2, 3) via the volume flow of the carbon dioxide from the gas coolers (2, 3) into the coolant collector (7).