ISSN:0145-7632    

DOI:10.1080/01457639408939819

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The Stirling heat engine was first patented in 1816 [1].It was a form of closed-cycle hot air engine, which, in itself, was not a new concept, even in the early nineteenth century. However, in Stirling's version there was a crucial innovation that made the engine unique—a regenerative heat exchanger. This was a remarkable invention, considering the state of knowledge of thermodynamics and heat transfer at the time. Moreover, Stirling, in his original patent document, foresaw the many future uses the regenerative principle could be put to in iron, steel, and glassmakingprocesses. The inventor of the regeneratorMdash; he called it an economizer—worked with his brother James to perfect the device, and by 1845 their experimental investigations had clearly identified the complexities of balancing the conflicting requirements for enhancing heat transfer and reducing gas dynamic drag [2]. Their contributions to the field of regenerative heat transfer have never been universally acknowledged. It is hoped that this article will help to redress this situation.

ISSN:0145-7632    

DOI:10.1080/01457639408939820

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Radiation view factors between opposed rectangular surfaces, between normal rectangular surfaces, and between cylinders and parallel rectangular surfaces are readily found in the literature. However, when the cylinder is located at the center of a rectangular duct, the view factors between the surfaces of the duct are obviously influenced by the presence of the cylinder; these uiew factors do not appear to be auailablc in the literature. This article presents the uiew factors between the surfaces of a long duct, in which a long cylinder is located at its center, in terms of two dimensionless parameters: D % S, the ratio of the cylinder diameter to the length of the short side, and S % L, the ratio of the length of the short side to the length of the long side.

ISSN:0145-7632    

DOI:10.1080/01457639408939821

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Enhanced heal transfer in curved rectangular channels depends on at least two geometric factors, the radius of curvature of the duct and the aspect ratio, which is the width / depth ratio of the duct. In this work, an expression for optimum aspect ratio is derived mathematically from a correlation that includes both aspect ratio and bend curvature parameters. Enhancement factors are developed that show optimal, near-optimal, and nonoptimal aspect ratios for curved rectangular ducts. Predicted enhancements are within 25% of published literature results for individual designs, two of which show heat transfer enhancement of 200% over that of a straight duct with turbulent flow. The theoretical maximum enhancement is shown to be about 480% over a straight-duct, turbulent-flow situation. This is not achievable in practice, but near-optimal solutions are achievable, yielding enhancements on the order of 200-300%

ISSN:0145-7632    

DOI:10.1080/01457639408939822

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In this article the dynamic model of a tunnel kiln is developed in detail, based on the transient heat conduction occurring in the products (or wares) and in the lining bricks of kiln cars (LBKC), as well as on the gas continuity, heat balance, and material balance equations. The computational method used to solve the present model is discussed briefly. Numerical simulations associated with a 72-m-long tunnel kiln that is used for firing clay bricks were performed. Transient heat conduction in two dimensions in wares and in LBKC were computed. Two oxygen schedules under one firing schedule and three lining brick structures were simulated. The fuel consumption and flow rates of primary air, cooling air, and exhaust flow were investigated under different atmosphere (i.e., oxygen concentration) schedules. The relationship between the fuel consumption and heat storage rate in wares and in LBKC was also studied. The results of the present numerical simulations show that, using the present model, we can predict the following parameters: temperature distributions in wares and in lining bricks and in metal parts of kiln cars; fuel consumption; heat losses; heat storage and heat storage rates in wares, in lining bricks, and in metal parts of kiln cars; gas flow; and exhaust components. The present results disclose that the dynamic characteristic of a tunnel kiln is dominated by the transient heat conduction in wares and in lining bricks. This transient feature determines the tunnel kiln behavior, such as fuel consumption, cooling airflow, exhaust flow, heat storage and heat loss, etc. The results obtained are in good agreement with the practical situation. From the present simulations two types of energy-saving structures of kiln cars are suggested.

ISSN:0145-7632    

DOI:10.1080/01457639408939823

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The present study reports on an analysis of the sensitivity of condensation heat transfer coefficient correlations on the simulations of the performance of steam surface condensers. Five correlations of heat transfer coefficient for filmwise condensation are tested against the experimental data for a steam surface condenser. A quasi-three-dimensional approach is used to predict the fluid flow and heat transfer in the steam surface condenser. The governing equations are solved in primitive variable form using a semiimplicit consistent control-volume formulation in which a segregated pressure correction-linked algorithm is employed. The modeling of the geometries of condensers, including tube bundles and baffle plates, is carried out based on the porous media concept using flow, heat, and mass transfer resistances.

ISSN:0145-7632    

DOI:10.1080/01457639408939824

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A mathematical model has been developed for the time-dependent heat conduction process in a region of arbitrary geometry. An alternating direction implicit (ADI) scheme has been worked out for the computer solution of the problem in three space dimensions. The time and nodal propagation of the errors are depicted graphically. Also included in the computer software is a subroutine for plotting the isotherms in various geometries.

ISSN:0145-7632    

DOI:10.1080/01457639408939825

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor