computational fluid dynamic

Single staggered is a design development of normal wire and tube heat exchanger that wires are welded with staggered configuration on two sides. Capacity of wire and tube heat exchanger is the ability of the heat exchanger to release heat. The objective of this study is to analyse the effect of wire pitch (pw) on capacity of single staggered wire and tube heat exchanger. The research method uses Computational Fluid Dynamic (CFD) simulation by ANSYS Fluent to analyse heat transfer of wire and tube; also to analyse airflow at surface the wire and tube. The simulation is experimentally validated by measuring temperatures at some points of wire and tube. Based on results, temperature contours increasing capacity of heat exchanger depend on smaller wire pitch that the highest value is 72.02 W at pw 7 mm. The reason is smaller wire pitch increases area of convection heat transfer surface. Whereas, airflow patterns show air move slowly at the wire and tube surface and flow with free convection. This study contributes new design of wire and tube heat exchanger with CFD and it can be applied to improve the performance of this heat exchanger in refrigeration system and other applications.

Converting chemical energy into electricity is done by an electro-chemical device known as a fuel cell. Thermal stress is caused at high operating temperature between 700 oC to 1000 oC of SOFC. Thermal stress causes gas escape, structure variability, crack initiation, crack propagation, and cease operation of the SOFC before its lifetime. The aim of this study is to present a method that predicts the initiation of cracks in an anisotropic porous planar SOFC. The temperature and stress distribution are calculated. The code uses the generated data, stress intensity factor, and the J-integral of the materials to predict the initiation of the crack inside the porous anode and cathode. The results show that the highest thermal stress occurs at the upper corners of cathode and at the lower corners of the anode. In addition, the thickness of cathode electrode on the left side is increased by 1.5 %. Finally, the crack initiation occurs on the left side between the upper and lower corners of the cathode.

In this article effects of friction stir welding (FSW) tool rotational and traverse speeds were studied on heat generation and temperature distribution in welding zone of AA1100 aluminum alloy and A441 AISI joint. Computational fluid dynamics method was used to simulate the process with commercial CFD Fluent 6.4 package. To enhance the accuracy of simulation in this Study, the welding line that is located work-pieces interface, defined with pseudo melt behavior around the FSW pin tool. Simulation results showed that with increase of FSW tool rotational speed, the generated heat became more and dimensions of the stir zone will be bigger. The calculation result also shows that the maximum temperature was occurred on the advancing side. The computed results demonstrated that with increasing tool linear speeds the heat generation experienced growth down trend. With increasing traveling speeds the time to reach maximum temperature in stir zone growth but the tool rotational speed dose not effect on time to reach maximum temperature. The model outcomes show that more than 85% total heat was produced by tool shoulder and the maximum heat with selected parameters in this study was 935 kelvin degrees. The computed results shows that the maximum value of strain rate achieved was 29 S-1 for A441 AISI side and 42 S-1 at AA1100 side.