Horizontal Heat Exchanger Tube with Vertical Outlet Risers
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Solution Overview
Problem
Conventional heat exchangers in Rankine cycles for vehicles experience uneven heating, thermal fatigue, and vapor lock due to the mixed phase of the working fluid, leading to inefficiencies in heat transfer and energy recovery.
Innovation Solution
A heat exchanger design featuring a generally horizontal heat exchanger tube with an inlet header at the lower surface and vertically oriented outlet risers along the upper surface, allowing for phase separation of the working fluid, with the liquid phase remaining in the tubes for continued heating and vapor phase rising through the risers, enhancing thermal conductivity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional heat exchangers are used with mixed phase working fluid, then heat transfer occurs, but uneven heating and thermal fatigue result
Solution Approach 1:
The heat exchanger is divided into multiple tubes, each containing a liquid chamber at the bottom and gas chambers at the top. This segmentation allows separate handling of liquid and vapor phases, with liquid remaining in the lower chambers and vapor rising through upper chambers, preventing mixed-phase contact and ensuring uniform temperature distribution across all tubes.
Solution Approach 2:
Different regions of the heat exchanger are assigned different functions: liquid chambers at the bottom for receiving and heating liquid working fluid, and gas chambers at the top for vapor collection and removal. This local differentiation ensures that each region operates under optimal conditions for its specific phase, preventing thermal fatigue caused by mixed-phase stress.
2Productivity
If conventional heat exchangers are used with mixed phase working fluid, then evaporation occurs, but vapor lock results
Solution Approach 1:
Vapor is extracted from the liquid phase as soon as it forms during evaporation. The gas chambers positioned at the top of each tube continuously remove vapor through outlet ports, preventing vapor accumulation that would cause vapor lock and maintain high productivity by ensuring continuous liquid flow through the heating zones.
Solution Approach 2:
The heat exchanger utilizes vertical dimensionality with liquid chambers at the bottom and gas chambers at the top, creating a clear phase separation along the vertical axis. This dimensional arrangement allows vapor to rise naturally through gravity and density differences, efficiently separating phases and preventing vapor lock while maintaining high energy recovery efficiency.
3Loss of energy
If mixed phase working fluid flows through heat exchanger, then heat transfer occurs, but thermal fatigue and wear result
Solution Approach 1:
The heat exchanger tubes are segmented into liquid chambers and gas chambers, with liquid entering at the bottom and vapor exiting at the top. This segmentation ensures that only liquid contacts the heating surfaces during the evaporation process, eliminating the thermal fatigue and wear caused by mixed-phase flow while maintaining efficient heat transfer through the liquid phase.
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 design achieves even temperature distribution and high thermal transfer efficiency by separating phases, reducing thermal fatigue and vapor lock issues, and improving overall energy recovery in Rankine cycles.
Implementation Method 1
The outer surface is adapted to contact a waste heat fluid... The remaining liquid in the heat exchanger tubes has a high thermal conductivity and high thermal transfer efficiency
Implementation Method 2
the vapor phase of the working fluid separates from the liquid phase and rises in vertical outlet risers of the outlet header
Implementation Method 3
heat exchanger tubes or chambers for evaporation of a working fluid in the cycle using a waste heat fluid
Implementation Method 4
As the working fluid is evaporated in the heat exchanger tubes, the vapor phase of the working fluid separates from the liquid phase
Data Source
AI summary
A vehicle includes a Rankine cycle containing a working fluid for waste heat recovery and has an evaporator. The evaporator has a heat exchanger tube positioned for generally horizontal flow of the working fluid therethrough. An inlet header is connected to a lower surface of an end region of the tube. An outlet header with a plurality of risers is positioned for generally vertical flow of the working fluid. The riser headers are connected to and spaced apart along an upper surface of the tube.