Papers by Keyword: Heat Transfer Coefficient (HTC)

Abstract: The purpose of this research is to investigate effect of wake splitter to pressure drop and heat transfer characteristics in a tube bank with staggered arrangements. The pressure drop and averaged heat transfer coefficient of seven rows with five tubes in each row with integral wake splitter has been determined by means of 2-D simulation using commercial computational fluid dynamics (CFD) code Fluent. Two type of integral wake splitter length have been studied, 0.5D and 1D with different location. Simulations have been carried out at Reynolds number based on tube diameter from 5000 up to 27800. The results, presented in terms of pressure drop as well as averaged heat transfer coefficient values, show the influence of wake splitter length and direction. By adding 0.5D wake splitter at downstream direction leads to higher averaged heat transfer coefficient and reduction of the pressure drop.

Abstract: Heat transfer boundary conditions have significant influence on the FEM analysis of the steel hot extrusion process using glass lubricant. However, the determination of heat transfer coefficient between billet and tooling lacked experimental basis. In order to obtain rational values of the coefficient, experimental study was conducted to measure it on thermal contact between P92 steel and H13 steel separated by glass lubricant. The influence of contact temperature, contact pressure and lubricant thickness was investigated. The obtained results can provide experimental basis for the determination of heat transfer boundary conditions for steel hot extrusion.

Abstract: This paper using Fluent Software to numerical simulate the heat transfer in square enclosure cavity air layer in different thickness and heights.By analysed the simulation results, we found that the best thickness in it is 20mm .Then we respectively used empirical formula as well as simulation results to calculated the heat transfer coefficient in air layer. The results showed that both numerical were very close, the calculation of heat transfer coefficient was consistent with the simulation results obtained by the rules.

Abstract: This study presents thermal models of pipes or ventilation ducts with variable flow rates. The models are based on dynamic thermodynamic heat balances, and much attention has been put into developing accurate heat transfer coefficients. MATLAB/Simulink environment has been used for modeling, but the model is however universal and can be implemented into any software. The model has been validated against measurement data, and found to be quite accurate for use in typical HVAC applications. Accuracy is particularly good if taking thermal damping into account. Thermal damping of pipe or duct mass has shown to be significant for dynamic performance. The model is suited for control simulations or accurate heat loss simulations, where dynamic conditions are important.

Abstract: Three-dimensional numerical simulation was implemented to analyze the heat transfer characteristics for jet impingement impact fin surface. 60 calculation cases were simulated to investigate the effects of different fin surfaces on heat transfer characteristics, and 12 jet array impingement cases were calculated for comparison. The results shown that the fin shape, the height and the fin arrangement were the critical factors to affect the jet impingement and the best combination were existed in a certain range. The thermal resistance of cylinder fin arranged in order was34.7 percent higher than that of cylinder fin arranged staggered. The thermal resistance of square fin arranged in order was38.9 percent higher than that of square fin arranged staggered .The heat transfer coefficients of impinging jet impact fin surface were better than that of jet array impingement. The fitting correlations on heat transfer of impinging jet impact fin surface were given.

Abstract: The three-dimensional model of heat exchangers with continuous helical baffles was built. The fluid flow dynamics and heat transfer of shell side in the helical baffled heat exchanger were simulated and calculated. The velocity, pressure and temperature distributions were achieved. The simulation shows that with the same baffle pitch, shell-side heat transfer coefficient increased by 25% and the pressure drop decreases by 18% in helical baffled heat exchanger compared with segmental helical baffles. With the analyzing of the flow and heat transfer in heat exchanger in 5 different inclination angles from 11°to 21°, it can be found that both shell side heat transfer coefficient and pressure drop will reduce respectively by 86% and 52% with the increases 11°to 21°of the inclination angles. Numerical simulation provided reliable theoretical reference for further engineering research of heat exchanger with helical baffles.

Abstract: This study presents an experimental investigation of the characteristics of the flow boiling heat transfer and pressure drop for refrigerant of R134a flowing in a small - diameter evaporative tube with the pipe sections having increased diameters. The experiments were performed at the saturation temperature of 5°C , heat flux of 5.12 ~ 10.96 ( KW/m²), mass flux of 200~600 ( kg/m²s), different length-to-diameter ratios of the test tubes and refrigerant quality of 0.07~0.78, and based on the same surface area of heat transfer. The enhancement performance ratios, θa/s for the tubes with the pipe sections having increased diameters relative to the smooth tube are higher than 1 (about 1.01~1.10). It means that the augmented tubes show the better overall performance than the smooth tube under study.

Abstract: In view of the present situation of high energy consumption from buildings in China, we study the thermal performances of the different wall systems of steel public buildings. We test on insulation tests for the different wall systems by protective thermal box law in the laboratory. According to the test data, we analyze differences between test values and theoretical values in order to determine the different wall systems for the different climatic regions and provide foundation to choose the wall systems of steel public buildings for energy savings.

Abstract: Fin widely used in industrial practice, and the surface heat transfer coefficient is not constant value. In this paper, through appropriate simplification, the mathematical model in Longitudinal Fin of Rectangular Profile has been established, When the surface heat transfer coefficient along the fin in the exponential changes. The exact solution of fin conduction has been get, and derived efficiency and the corresponding fin heat flux formula. And an example has been given to verify. The solution can be applied to engineering practice, and guided theoretical the heat transfer enhancement in the design of fin.

Abstract: With the appearance of high temperature resistance alloy steel and the requirement of light weight for vehicles, more and more exhaust manifolds are made from newly developed alloy steel. The changing of material directly affects the design and manufacturing process. To estimate the thermal load of the tight-coupled exhaust manifold, the joint analysis methods of CFD and FEM are put forward to predict the temperature distribution, thermal stress and deformation. Using Computational Fluid Dynamics (CFD) method, gas temperature and convective heat transfer coefficient, adjoining the inside and outside surfaces of the exhaust manifold, are estimated firstly in this paper. Then these results are mapped to the finite element mesh of exhaust manifold, which are created for the heat transfer analysis. At last, thermal stress and thermal deformation analysis are presented by taking nonlinear material properties into account, which provide some reference to evaluate the cooling capacity and structure design of exhaust manifold.