Shell-and-tube heat exchanger with inner guiding jacket
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Solution Overview
Problem
Existing shell-and-tube heat exchangers face challenges in preventing vaporization during natural circulation and managing temperature crosses between hot and cold media, leading to instability and potential overheating or corrosion, especially when using U-shaped tubes with multi-pass configurations.
Innovation Solution
A shell-and-tube heat exchanger design featuring a cylindrical geometry with a first pressure chamber and a second pressure chamber connected by a common tube-sheet, incorporating U-shaped tubes with a guiding jacket that creates a stagnant zone to prevent heat transfer in specific portions, allowing for stable operation even with vaporizing cooling media or temperature crosses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If U-shaped tubes with multi-pass configurations are used, then heat transfer area is increased, but vaporization occurs during natural circulation causing instability
Solution Approach 1:
The U-shaped tube bundle is segmented into multiple passes (first pass, second pass, third pass) with distinct flow directions. The first pass handles downward flow where vaporization is prevented, the second pass handles upward flow, and the third pass provides additional heat transfer area. This segmentation allows each section to be optimized for its specific function, preventing vaporization-induced instability while maintaining high heat transfer area.
Solution Approach 2:
Different sections of the tube bundle are assigned different qualities: the first pass is designed for vaporization-free heat transfer with downward flow, the second pass allows upward flow with potential vaporization, and the third pass provides additional heat transfer. The shell is also divided into zones with different baffle configurations to optimize local flow patterns and prevent harmful vaporization effects in critical areas.
2Productivity
If multi-pass configurations are used, then heat transfer efficiency is improved, but temperature crosses between hot and cold media occur
Solution Approach 1:
The heat exchanger dynamically manages temperature profiles across multiple passes. The first pass maintains high temperature differential for efficient heat transfer, the second pass handles the transition zone where temperature cross could occur, and the third pass ensures proper temperature sequencing. The dynamic flow arrangement and baffle positioning optimize temperature distribution to minimize harmful temperature crosses while maintaining high heat transfer efficiency.
3Adaptability or versatility
If U-shaped tubes are used, then thermal expansion is accommodated, but intermediate welding is required creating potential failure points
Solution Approach 1:
The intermediate welding section is extracted and replaced by a U-bend configuration. The U-shaped tubes are formed without intermediate welds by bending the tube material into a U-shape, eliminating the welding joint that would be required to connect separate tube sections. This maintains the ability to accommodate thermal expansion through the flexible U-bend geometry while removing the reliability issue associated with intermediate welding.
4Productivity
If vaporization occurs in descending legs, then cooling effect is enhanced, but natural circulation is disturbed
Solution Approach 1:
The design preliminarily prevents vaporization in the descending legs by arranging the first pass to flow downward through sections where vaporization would be harmful to natural circulation. The baffle configuration and tube arrangement are designed in advance to ensure that the descending flow occurs in zones where liquid cooling is maintained, preventing the formation of vapor pockets that would disrupt natural circulation. This preliminary anti-action approach prevents the problem before it can occur during operation.
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
The design ensures stable and efficient heat transfer performance by minimizing vaporization and temperature crosses, maintaining positive thermal-hydraulic conditions and extending the operational life of the heat exchanger.
Implementation Method 1
The inner guiding jacket being open at a second end thereof, thereby creating an at least partly stagnant zone within the inner guiding jacket preventing the first fluid flow across said first portion of each U-shaped exchanging tube, therefore preventing or reducing the heat transfer from the first fluid to the second fluid in said first portion of each U-shaped exchanging tube
Implementation Method 2
The tube-sheet is connected to a tube bundle housed in the first pressure chamber and comprising a plurality of U-shaped exchanging tubes through which the second fluid flows to indirectly perform heat exchange with the first fluid
Implementation Method 3
designed to operate with hot process gases. Such a heat exchanger is designed for cooling a hot medium either by a vaporizing cooling medium or by a non-vaporizing cooling medium
Data Source
AI summary
A shell-and-tube heat exchanger has a cylindrical geometry and comprises a first pressure chamber and a second pressure chamber connected to a common tube-sheet on opposite sides. The tube-sheet is connected to a tube bundle housed in the first pressure chamber and comprising a plurality of U-shaped exchanging tubes. Each U-shaped tube is provided with a first portion and with a second portion. The first pressure chamber contains at least one inner guiding jacket having a cylindrical or pseudo-cylindrical geometry and extending along the major longitudinal axis of the first pressure chamber. The inner guiding jacket surrounds the first portion of each U-shaped tube for at least part of the respective length. The inner guiding jacket is sealingly connected, at a first end thereof, to the tube-sheet. The inner guiding jacket is open at a second end thereof.