ISSN:0145-7632    

DOI:10.1080/01457639808939909

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Heat transfer measurements are reported for the film condensation of pure steam on a thick-walled horizontal tube. The thermal resistance of the tube in these tests was approximately 3 times that of the condensation film. Significant circumferential temperature gradients were measured around the tube, with the magnitude of the variation exceeding that of the average vapor-to-wall temperature difference. The results were found to be in close agreement with a numerical model for condensation on a nonisothermal surface and also with the correlations proposed by Fujii for the surface temperature distribution under uniform heat flux conditions. The heat flux through the condensate film was found to be uniform within the region 0°–;165° but decreased where the condensate film thickened abruptly on the underside of the tube, where droplets were being formed.

ISSN:0145-7632    

DOI:10.1080/01457639808939910

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An analysis is made of the heat transfer in the turbulent flow of a high-temperature participating gas through a circular cross-section tube whose outer surface is covered by nonideal insulation. The gas is nongray, and its radiative properties are evaluated by the weighted sum of gray-gases model; its transport properties and density are assumed to be uniform throughout the duct. The radiative exchanges are evaluated by the zone method. This work is mainly concerned with the effect of the gas inlet temperature, the tube inner diameter, and the turbulent Reynolds number on the total, conuective, and radiative Nusselt numbers.

ISSN:0145-7632    

DOI:10.1080/01457639808939911

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The article presents a two-dimensional numerical model for the injection of a fluid through a slot into a free stream. The model is based on a finite-volume integration of the equations governing mass, momentum, and heat transport. The solution accuracy was improved by using local grid refinement. The storage of variables was done in a collocated manner, thus allowing for the reduction of storage requirements and a more accurate interfacing of the various subdomains of the grid. The model developed was doubly validated by comparison with available experimental data and the results of an analytical method proposed for two-dimensional injection of an irrotational inviscid fluid.

ISSN:0145-7632    

DOI:10.1080/01457639808939912

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this study the transient response of counterflow and parallel-flow heat exchangers hauing finite wall capacitance is investigated. Three configurations are considered: the flat-plate exchanger with phase change in either channel and the shell-and-tube exchangers with phase change either in the tube or in the shell. The transient response of these configurations results from sudden change in the inlet temperature of the one-phase fluid or from sudden exposition of the shroud to ambient conditions. The thermal behavior of the exchanger is described by detecting the transient variations in the temperature of the one-phase fluid and in the quality of the two-phase fluid within the exchanger. Closed-form expressions for these parameters are presented. These expressions can be used to evaluate different design parameters required by heat exchanger designers.

ISSN:0145-7632    

DOI:10.1080/01457639808939913

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method is proposed for reducing the weight of a straight rectangular fin by providing a semicircular cut at its tip. Finite element analysis is used to compute the temperature distributions and estimate the fin efficiency values. A fin comparison factor (FCF) is defined to take into account the simultaneous reduction in the weight of an otherwise optimized fin [1[f and the corresponding heat transfer rate. Typical values of fin efficiency and FCF for the proposed fin are 66.85% and 1.22 at a Biot number of 0.1048 and a cut-size ratio of 0.798. If the same fins were arranged in an array, under identical convectiue conditions and when the pitch is equal to the thickness, the efficiency of the array is estimated to be 68.05%.

ISSN:0145-7632    

DOI:10.1080/01457639808939914

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This article provides closed-form equations for computing view factors for parallel rectangular plates. View factor algebra is used in the derivation of these equations. Results of nine cases of parallel rectangular plates are given. Some results presented are taken from the literature and reproduced here for the sake of completeness. The equations given are easy to use for computation.

ISSN:0145-7632    

DOI:10.1080/01457639808939915

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor