Central Solar Receiver Tubes for Heat Transfer and Thermal Stress
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Solution Overview
Problem
Concentrating solar power receivers face inefficiencies in heat transfer and thermal stress management, particularly in designs that aim to maximize absorption of solar energy and handle differential expansion, while maintaining effective gas flow and pressure.
Innovation Solution
A central solar receiver with a heat exchanger assembly featuring concentric inlet and outlet chambers connected by tube assemblies with inner and outer tubes, allowing 180° flow direction change, and equipped with axially movable inner tubes and helical fins to enhance heat transfer and minimize thermal stresses, along with varying tube lengths and domed closed ends for optimized energy absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple high temperature resistant metal alloy boiler tubes are used in tubular receivers, then heat transfer efficiency is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The receiver is divided into multiple independent tubular elements arranged in an array. Each tube acts as an independent heat transfer channel, allowing the system to scale heat transfer capacity by adding or removing tubes rather than increasing the complexity of individual components.
Solution Approach 2:
Different sections of the tubes have different properties - the tubes are selectively positioned and oriented to capture solar radiation from specific directions. The tube material and dimensions can be optimized for local thermal and mechanical conditions at different positions in the array.
2Use of energy by moving object
If directly-irradiated volumetric receivers with porous absorber medium are used, then heat absorption is improved, but pressure management and gas flow control become more difficult
Solution Approach 1:
The invention extracts the heat absorption function from a single volumetric chamber and distributes it across multiple tubular elements. This allows the working gas to flow through defined pathways outside the tubes while heat is absorbed through the tube walls, separating the absorption and flow control functions.
Solution Approach 2:
The tube walls act as an intermediary between the concentrated solar radiation and the working gas. Heat is transferred through the tube walls from the absorbed radiation to the gas flowing in the annular space, providing a controlled interface for heat transfer while maintaining pressure boundaries.
3Use of energy by moving object
If tube length is increased to enhance heat absorption, then energy capture is improved, but thermal stress and differential expansion increase
Solution Approach 1:
An inner tube is nested within an outer tube, creating a telescopic structure. This allows the inner tube to expand and contract axially independently within the outer tube, accommodating thermal expansion differences without generating excessive thermal stress in the heat absorption sections.
Solution Approach 2:
The inner tube is made movable within the outer tube, transforming a static rigid structure into a dynamic one. This allows the system to adapt to thermal expansion and contraction during operation, reducing thermal stresses while maintaining the long tube length needed for effective energy capture.
4Stress or pressure
If inner tube is made movable within outer tube, then thermal stress is reduced, but manufacturing precision and assembly difficulty increase
Solution Approach 1:
Axial clearance and positioning features are built into the design of the nested tube structure before operation. This pre-built accommodation for movement allows the inner tube to expand and contract freely within defined limits, reducing thermal stress without requiring high-precision alignment during assembly.
Solution Approach 2:
Different sections of the nested tube structure have different degrees of constraint. The tubes are rigidly connected at certain locations to maintain structural integrity while allowing relative movement at other locations, optimizing both stress reduction and manufacturability in different regions of the assembly.
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 solution effectively transfers heat from concentrated solar radiation to a pressurized air stream, reducing thermal stresses and enhancing heat transfer efficiency, thereby improving the performance of the solar power generation system.
Implementation Method 1
heat transfer fluid to be heated is introduced to the apex of each of the pyramidal elements and become heated as it flows between the outer wall of the pyramidal element that become heated by solar energy
Implementation Method 2
receiving reflected solar radiation from a heliostat field of solar radiation reflectors that are focused onto the central solar receiver
Implementation Method 3
helical fins to enhance heat transfer
Implementation Method 4
axially movable inner tubes and helical fins to enhance heat transfer and minimize thermal stresses
Data Source
AI summary
A central solar receiver (1) is provided having a heat exchanger assembly with walls that form an inlet chamber (2) and a generally juxtaposed outlet chamber (3) connected to each other by way of a multitude of tube assemblies (4). Each tube assembly (4) has an inner tube (6) and an outer tube (7) with the tube assemblies (4) extending away from the inlet and outlet chambers (2, 3). A remote end (8) of the outer tube (7) is closed and the inner tube (6) terminates short of that closed end (8). The interior of each inner tube (6) communicates with one of the inlet and outlet chambers (2, 3) and a space between each of the inner and outer tubes (6, 7) communicates with the other of the inlet and outlet chambers (2, 3) to form a passageway connecting the inlet and outlet chambers (2, 3) by way of the inner tube (6) and the space between the inner and outer tubes (6, 7) with a change in direction of flow of about 180°.