Heat exchanger
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Solution Overview
Problem
Falling film evaporators in vapor compression systems face challenges in managing vapor flow velocity, leading to cross flow disruptions and entrainment of liquid droplets, which affect heat transfer performance and risk damage to compressors.
Innovation Solution
A heat exchanger with a tube bundle arrangement where the vertical pitch between adjacent tubes is larger in the upper region than in the lower region, and the horizontal pitch between columns is larger in the outer region than in the inner region, to control vapor flow velocity and prevent entrainment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the tube bundle uses a uniform pitch arrangement, then the structure is simple and easy to manufacture, but the vapor flow velocity becomes excessive in certain regions causing cross flow disruptions and liquid droplet entrainment
Solution Approach 1:
The patent applies asymmetry by implementing a non-uniform pitch arrangement where the vertical pitch between adjacent tubes varies along the tube bundle length, and the horizontal pitch between columns also varies. Specifically, the pitch is smaller in regions where vapor generation is intense and larger in regions where vapor flow is less intense, creating an asymmetric distribution that adapts to the local vapor flow conditions and prevents excessive vapor velocity and liquid droplet entrainment.
Solution Approach 2:
The patent applies local quality by making the pitch arrangement location-dependent. Different regions of the tube bundle have different pitch values tailored to their specific operational characteristics. In regions with high vapor generation rates, smaller pitches are used to restrict vapor flow velocity, while in regions with lower vapor generation, larger pitches are used to maintain adequate liquid refrigerant distribution. This localized optimization ensures reliable operation throughout the entire tube bundle.
2Reliability
If the vertical pitch between tubes is increased in the upper region, then vapor velocity is suppressed and liquid distribution is improved, but the tube bundle structure becomes more complex
Solution Approach 1:
The patent applies dynamics by implementing a gradient pitch arrangement where the vertical pitch between adjacent tubes gradually increases from the lower region to the upper region of the tube bundle. This dynamic variation in pitch allows the system to adapt to the changing vapor flow conditions along the height of the tube bundle, suppressing vapor velocity in upper regions where vapor accumulation occurs while maintaining simpler construction compared to completely irregular arrangements.
3Reliability
If the horizontal pitch between columns is increased in the outer region, then vapor velocity is reduced at the boundaries, but the overall heat transfer area is reduced
Solution Approach 1:
The patent applies local quality by implementing a horizontal pitch arrangement where the pitch between columns varies across the width of the tube bundle. Specifically, the horizontal pitch is larger in the outer regions (near the boundaries) and smaller in the inner regions (near the center). This localized adjustment suppresses vapor velocity at the boundaries where vapor escape occurs while maximizing the heat transfer area in the central regions, thus balancing reliability and productivity.
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 arrangement suppresses vapor velocity within the tube bundle, preventing disruptions to the liquid refrigerant film and reducing entrained liquid droplets, thereby enhancing heat transfer performance and ensuring reliable operation.
Implementation Method 1
a vapor flow velocity from exceeding a prescribed level
Implementation Method 2
causing cross flow or travel by the vaporized refrigerant in a transverse direction
Implementation Method 3
liquid refrigerant is deposited onto exterior surfaces of the heat transfer tubes from above so that a layer or a thin film of the liquid refrigerant is formed along the exterior surfaces of the heat transfer tubes. Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film to the vapor-liquid interface where part of the liquid refrigerant evaporates
Implementation Method 4
Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film
Implementation Method 5
Heat from walls of the heat transfer tubes is transferred via convection and/or conduction through the liquid film
Implementation Method 6
The liquid refrigerant that does not evaporate falls vertically from the heat transfer tube at an upper position toward the heat transfer tube at a lower position by force of gravity
Data Source
AI summary
A heat exchanger is adapted to be used in a vapor compression system, and includes a shell, a distributing part and a tube bundle. The tube bundle includes a plurality of heat transfer tubes arranged in a plurality of columns extending parallel to each other when viewed along the longitudinal center axis of the shell. The heat transfer tubes has at least one of: an arrangement in which a vertical pitch between adjacent ones of the heat transfer tubes in at least one of the columns is larger in an upper region of the tube bundle than in a lower region of the tube bundle; and an arrangement in which a horizontal pitch between adjacent ones of the columns is larger in an outer region of the tube bundle than in an inner region of the tube bundle.