Numerical research on thermal stress of steam cooler tube sheet mechanical structure

Steam cooler is one of the most important mechanical equipment in thermal power generation system and nuclear power generation system. The steam cooler bears a huge temperature gradient load when the working conditions are switched. In order to analyze the thermal stress of steam cooler tube sheet with high temperature load under harsh working conditions, the thermal-structural coupling analysis model of steam cooler tube sheet is constructed with finite element method. The results show that the stress concentration exists at the position connection between heat exchanger tube and cylinder. The maximum stress is located at the outermost heat exchanger tube with the peak stress of 320MPa. The heat exchanger tube layout alone cause higher stress. This situation should be avoided in the design of heat exchanger tube sheet. Furthermore, the strength and safety of the steam cooler tube sheet are evaluated with the stress linearization method. The steam cooler tube sheet design meets the safety requirements of structural strength under high temperature load.

Failure analysis of an economizer tube sheet & its cover due to corrosionand imperfection

The boiler's economizer was found to be inefficient. Corrosion is suspected to be the source of the economizer's pressure reduction. The examinations included visual inspection, stereomicroscope, metallography, elemental microanalysis by EDS, and chemical composition analysis. The economizer failed due to a weld crater caused by improper welding, which induced residual welding stress. The slight sulfur content of the condensed or flue gas that causes rusting on the economizer's outer cover is not considered a severe failure issue. Material SUS304 stainless steel is the right selection for economizer materials.

Stress Analysis on Tubesheet Referring to TEMA Standard

A heat exchanger is a device used to transfer heat without mass transfer. The equipment must be designed according to established standards. The standard that is widely used is the standardissued by TEMA (Tubular Exchanger Manufacturer Association). The results of the design of theheat exchanger with these standards are considered less efficient in terms of the material. Theefficiency of the material used can be analyzed by stress analysis on the components that withstand the force, and one of these components is the tube sheet. Stress analysis on tube sheets can use finite element-based software. The results of the research show that the tube sheet design that refers to the TEMA standard is relatively safe because the maximum von Mises stress is below the yield strength of the material used, while the overdesign value is rather significant because the average von Mises stress is also far below the yield strength of the material used.

Experimental Investigation and Theoretical Analysis on the Performance of Tube-Sheet Photovoltaic Thermal (PV/T) Collectors

The PV/T collectors realize the simultaneous output of electricity and thermal energy, which are more efficient than the separated photovoltaic (PV) or solar thermal collectors. In this paper, the electricity generation and thermal collection performances of tube-sheet PV/T collector are studied. The main research contents are as follows: an experimental test system of PV/T collector was built to test the electricity generation and thermal collection performances of tube-sheet PV/T at an inlet water temperature of 30°C. Moreover, the flow resistance test was carried out. In addition, the theoretical heat transfer model was established, and the thermal performance was calculated by theoretical analysis. The experimental data showed that the daily average temperature difference between the PV panel and the inlet water temperature was about 22.5°C. The daily average electrical efficiency was about 9.25%, and the daily average thermal efficiency was about 28.67%. The theoretical analysis of the tube-sheet PV/T model was carried out, and the calculated results were close to the experimental results. The main reason for the large temperature difference between the PV panel and water temperature was that the combined thermal resistance between the PV panel and the absorber plate was large, and reducing the combined thermal resistance could reduce the temperature of the PV panel. The effects of solar irradiance, ambient temperature and spacing of row tubes on the performance of thermal collection were analyzed to optimize the PV/T performance.

New Joining Concepts for Self-Pierce Riveting

This paper is focused on innovative self-pierce riveting concepts to produce invisible joints in sheet-sheet and tube-sheet connections. The common element to these two different types of joints is the use of tubular rivets with chamfered ends, which are accessories in the case of sheet-sheet joints and constitutive (structural) elements in the case of tube-sheet joints. The presentation draws from the deformation mechanics of double-sided self-pierce riveting for producing lap joints in overlapped sheets to the development of self-pierce riveting of tubes to sheets, which is a new joining by forming process capable of attaching a sheet to the end of a tube, at room temperature. Aluminum sheets, carbon and stainless-steel tubes are utilized to demonstrate the effectiveness of the new self-pierce riveting concepts and finite element modelling using an in-house computer program gives support to the overall presentation. Destructive tests are carried out to evaluate the destructive strength that the joints are capable to withstand without failure.