CO2 Receiver Heat Exchanger for Flash Gas Pressure Control
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Solution Overview
Problem
CO2 refrigeration systems face high energy consumption and the risk of liquid CO2 entering the compressor inlet, which can lead to inefficiencies and potential damage.
Innovation Solution
The integration of a second pressure reduction device connected to a heat exchanging device within the receiver, which heats the refrigerant and recirculates it to reduce flash gas formation, decrease the receiver's pressure, and increase the temperature of the suction gas before it reaches the compressor, thereby preventing liquid CO2 from entering the compressor and enhancing system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If flash gas is removed from the receiver to maintain low pressure, then pressure is controlled (30-45 bar), but energy consumption increases and system efficiency decreases
Solution Approach 1:
The patent converts the harmful flash gas that needs to be removed into a useful resource by recirculating it through the evaporators. The flash gas, instead of being discarded to maintain pressure, is redirected to provide additional cooling capacity in the evaporators, thereby converting a problematic byproduct into a beneficial contributor to system performance and energy efficiency
Solution Approach 2:
The system recovers the flash gas that would otherwise be discarded from the receiver. By implementing a recirculation line that redirects flash gas back through the evaporators before returning it to the receiver, the system recovers potential cooling capacity and reduces energy consumption while maintaining proper pressure control
2Reliability
If suction gas temperature is increased to prevent liquid CO2 from entering the compressor, then compressor protection is improved, but energy consumption increases
Solution Approach 1:
The patent utilizes the cold flash gas from the receiver as a cooling source to pre-cool the suction gas before it enters the compressor. This converts the potentially harmful cold flash gas into a beneficial cooling resource that protects the compressor from liquid CO2 while actually reducing the energy required for heating, as the flash gas provides free cooling capacity
Solution Approach 2:
The system uses its own flash gas resource to provide the cooling function needed for compressor protection, rather than requiring external energy input. The flash gas self-regulates the suction gas temperature through heat exchange, making the system self-sufficient for this protective function
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 configuration reduces energy consumption, minimizes flash gas in the receiver, increases the efficiency of evaporators, and prevents liquid CO2 from reaching the compressor, ensuring higher overall system efficiency and protection against liquid hammer.
Implementation Method 1
a first heat exchanging device, which first heat exchanging device is integrated in the receiver, either in liquid part, gas part or in both, in which first heat exchanging device the refrigerant is heated
Implementation Method 2
subsequent to the receiver a medium temperature loop and a low temperature loop, wherein the medium and low temperature loops each comprise in flow direction an expansion device
Implementation Method 3
which expansion valves are connected to at least one first group of evaporators
Data Source
AI summary
A refrigeration system using CO2 as a refrigerant includes a receiver having a liquid outlet connected to expansion valves, which are connected to evaporators, which are connected to the suction side of the compressor. The receiver includes a second gas outlet connected to a second pressure reduction device, to reduce the energy consumption in CO2 cooling systems and to protect the compressors against liquid CO2 by heating the suction gas. The second pressure reduction device is connected by tubing to a first heat exchanging device, which is integrated in the receiver, so that gas that is evaporated in the top of a receiver can be used for cooling the liquid part of the same receiver.