Heat Pump Internal Heat Exchanger with Variable Superheat Control
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Solution Overview
Problem
Heat pumps employing vapor compression cycles face inefficiencies due to inadequate control over refrigerant superheat, leading to suboptimal heat transfer and potential compressor damage, especially when operating under varying conditions.
Innovation Solution
A heat pump system with an internal heat exchanger and a controller that dynamically adjusts the expansion valve to maintain a variable target superheat based on operating conditions, ensuring that at least 90% of superheating occurs in the internal heat exchanger, optimizing evaporative and sensible heating distribution between the evaporator and internal heat exchanger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed superheat control method is used, then the compressor is protected from damage, but the heat pump efficiency deteriorates under varying operating conditions
Solution Approach 1:
The patent implements dynamic superheat control by varying the target superheat value based on operating conditions such as ambient temperature and heat exchange medium temperature. The controller adjusts the expansion valve positioning dynamically to maintain optimal superheat levels different from fixed control methods, thereby improving efficiency while ensuring compressor protection across varying operating conditions.
Solution Approach 2:
The patent changes the superheat parameter from a fixed value to a variable target superheat that depends on operating conditions. The controller determines different target superheat values based on parameters like ambient temperature and heat exchange medium temperature, allowing the system to adapt to varying conditions and optimize performance while maintaining reliability.
2Reliability
If superheat is increased to prevent compressor damage, then reliability improves, but heat transfer efficiency deteriorates
Solution Approach 1:
The patent optimizes the superheat parameter by determining target superheat values that are sufficient for compressor protection but not excessively high. The controller adjusts the superheat level dynamically based on operating conditions, maintaining it within an optimal range that balances compressor protection with heat transfer efficiency, avoiding the energy loss associated with excessive superheat.
Solution Approach 2:
The controller uses feedback from temperature sensors to monitor actual superheat levels and adjusts the expansion valve positioning accordingly. This feedback mechanism ensures that superheat is maintained at the optimal level needed for compressor protection without exceeding it, thereby preventing heat transfer efficiency deterioration.
3Productivity
If dynamic superheat control is implemented, then heat pump efficiency improves, but device complexity increases
Solution Approach 1:
The controller performs multiple functions: it determines target superheat values based on operating conditions, controls the expansion valve positioning, and maintains optimal superheat levels. By consolidating these functions in a single controller, the patent achieves dynamic superheat control and improved efficiency without proportionally increasing device complexity.
Solution Approach 2:
The system uses its own operating condition data (temperatures from sensors) to automatically determine appropriate target superheat values and adjust the expansion valve. This self-service capability allows dynamic optimization of efficiency without requiring external complex control systems or additional sophisticated components.
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 enhances the coefficient of performance (COP) of the heat pump by efficiently distributing heat transfer, maintaining a dry saturation location within the vaporization portion, and preventing compressor damage by optimizing refrigerant superheat levels.
Implementation Method 1
an internal heat exchanger configured to transfer heat from refrigerant in the liquid line pathway to refrigerant in the suction line pathway, to superheat the refrigerant upstream of the compressor
Data Source
AI summary
There is disclosed heat pump, comprising: an internal heat exchanger configured to transfer heat from refrigerant in a liquid line pathway to refrigerant in a suction line pathway, to superheat the refrigerant upstream of a compressor; and a controller configured to: control an expansion valve to maintain a target superheat of refrigerant at a control location. The target superheat is variable and is determined based on one or more operating conditions of the heat pump. There is also disclosed a method of operating a heat pump and a simulation method to determine a variable superheat.