Systems and methods for control of superheat from a subcooler
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Solution Overview
Problem
Excessive subcooling in HVACR systems can lead to issues like liquid slugging and freezing at heat exchangers, requiring defrost cycles and reducing efficiency, while controlled subcooling aims to enhance capacity and efficiency without these risks.
Innovation Solution
A suction line heat exchanger with a flow director and controller to regulate the flow of working fluid, determining superheat generation and controlling it to stay below a threshold value, thereby managing subcooling levels to prevent excessive superheat and maintain system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If subcooling is increased to improve capacity and efficiency, then heating capacity and efficiency improve, but risk of liquid slugging and freezing increases
Solution Approach 1:
The controller continuously monitors superheat at the suction line heat exchanger and adjusts the flow director accordingly. When superheat exceeds the threshold, the controller reduces subcooling by adjusting the flow director to bypass more refrigerant, preventing liquid slugging and freezing while maintaining optimal heating capacity
Solution Approach 2:
The system dynamically adjusts the subcooling parameter by controlling the flow director position based on measured superheat conditions. This allows the system to operate at optimal subcooling levels for maximum heating capacity while preventing excessive subcooling that would cause reliability issues
2Loss of energy
If subcooling is increased to improve efficiency, then energy consumption decreases, but defrost cycles are required which reduce efficiency
Solution Approach 1:
The controller uses real-time superheat measurements to adjust subcooling levels, preventing the conditions that would trigger freezing and subsequent defrost cycles. This feedback control maintains energy efficiency while avoiding the productivity loss from defrost operations
Solution Approach 2:
The system proactively controls subcooling to prevent freezing conditions before they occur by monitoring superheat and adjusting the flow director. This preliminary action avoids the need for corrective defrost cycles, maintaining both energy efficiency and operational continuity
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 increases heating capacity by approximately 4% and reduces energy consumption by 4% at maximum heating capacity, improving overall efficiency and avoiding issues associated with excessive subcooling.
Implementation Method 1
a suction line heat exchanger configured to exchange heat between a first working fluid flow, where the first working fluid flow is a flow of working fluid from the evaporator to the suction of the compressor, and a second working fluid flow, where the second working fluid flow is a flow of working fluid from the condenser to the expander
Data Source
AI summary
Systems and methods for controlled subcooling of working fluid in a heating, ventilation, air conditioning and refrigeration (HVACR) system through a suction line heat exchanger are disclosed. The suction line heat exchanger may receive a first fluid flow travelling to a suction of the compressor in the HVACR system and second flow of working fluid that is travelling from a heat exchanger receiving the discharge of the compressor to an expansion device. Superheating of the first working fluid may be determined based on temperature measurements prior to and following the suction line heat exchanger. The superheating may be used to control the quantity of the second flow of working fluid introduced into the suction line heat exchanger, for example to maintain superheat that is below a threshold value. These systems may include chillers and heat pump systems, and methods may be applied to chillers or heat pump systems.