Graduated Tube Bundle Cooler for Tube Disk Thermal Stress
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Solution Overview
Problem
Tube bundle heat exchangers in gas turbine cooling air coolers face high thermal stresses on tube disks due to temperature gradients, leading to material damage and the need for costly jacket compensators, and are prone to stress corrosion cracking (SRC), which can cause system failure.
Innovation Solution
Using ferritic stainless steel for the straight tubes and non-alloy steel for the pressure vessel, combined with a thermal insulation device at the inlet tube disk to reduce heat transfer and prevent direct contact between the primary fluid and the tube, thereby minimizing thermal stresses and the risk of SRC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If austenitic steel tubes are used in the tube bundle heat exchanger, then the tubes can withstand high temperatures and corrosion, but the tube disk experiences high thermal stresses and is prone to stress corrosion cracking (SRC)
Solution Approach 1:
The patent changes the material parameter of the tubes from austenitic steel to ferritic steel, which has different thermal expansion characteristics. This parameter change reduces the thermal stress differential between the tubes and the tube disk, thereby preventing stress corrosion cracking while maintaining high-temperature and corrosion resistance.
Solution Approach 2:
The patent employs a composite material system where ferritic steel tubes are used in conjunction with a ferritic steel tube disk, creating a material combination with matched thermal expansion properties. This composite approach ensures compatibility between components, reducing thermal stresses at the tube-disk interface.
2Productivity
If the primary fluid directly contacts the tubes at the inlet tube disk, then heat exchange efficiency is maximized, but thermal stresses on the tube disk increase due to temperature gradients
Solution Approach 1:
The patent applies local quality by using ferritic steel specifically for the tubes and tube disk in the high-temperature inlet region, while the rest of the pressure vessel can use different materials. This localized material selection addresses the thermal stress problem at the critical inlet tube disk area without affecting the overall heat exchange efficiency.
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 reduces thermal stresses on the tube disks, eliminates the need for jacket compensators, and prevents SRC, allowing for efficient cooling of air up to 550°C while maintaining the functionality of the heat exchanger.
Implementation Method 1
a thermal insulation device at the inlet tube disk to reduce heat transfer and prevent direct contact between the primary fluid and the tube
Implementation Method 2
heat exchangers are used to exchange heat between a heat-emitting medium to be cooled (here referred to as the primary fluid) and a heat-absorbing medium to be heated (here referred to as the secondary fluid or 'cooling fluid')
Implementation Method 3
the water is often vaporized in the process and the energy consumption is increased due to the high vaporization enthalpy
Implementation Method 4
the water is often vaporized in the process
Data Source
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AI summary
The invention relates to a tube bundle heat exchanger in graduated tube design, comprising a pressure vessel, a graduated tube bundle with a number of graduated tubes, which are arranged through an inlet tube disk and an outlet tube disk and run through the interior of the pressure vessel. The invention also relates to a gas turbine cooling air cooler with a tube bundle heat exchanger, a gas turbine power plant and a gas and steam turbine power plant with a gas turbine cooling air cooler according to the invention and a process gas cooler and a method for cooling cooling air with such a gas turbine cooling air cooler.