ISSN:0145-7632    

DOI:10.1080/01457639008939719

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The history of the fouling of heat transfer surfaces is reviewed up to 1979. Four epochs of fouling are identified. Particular attention is paid to fouling in steam boilers and steam condensers. The origin of the cleanliness factor and the fouling factor are discussed. The introduction of scientific methods of studying fouling through the model of Kern and Seaton, and the application of models based on fundamental ideas in mass transfer are considered. The paper concludes by drawing attention to the successes in understanding fouling and pointing out the needs for future research.

ISSN:0145-7632    

DOI:10.1080/01457639008939720

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The corresponding states principle (CSP) thermodynamic generalization methods described in [1] and references cited therein rest entirely on the empirical fact that key saturated liquid and vapor properties are universal functions (UFs) of reduced pressure P+= P/PσThis was highlighted in Figs. 2-4 of a recent paper in Heat Transfer Engineering [2]. However, these figures included only four to eight different substances, mostly common refrigerants, and were partially based on published physical properties dating back to the 1960s. The prime objective of the present communication is to document more thoroughly the extremely broad validity and accuracy of the UF (P+) that are most relevant in two-phase flow and heat transfer engineering analyses. For this purpose 21 different substances (including thermodynamically “similar” as well as “dissimilar” chemical species, pure substances, and azeotropic mixtures) are assessed on the basis of recent (1980s) thermophysical properties [3, 4] with the help of more precise modern computer-aided graphical/analytical techniques.

ISSN:0145-7632    

DOI:10.1080/01457639008939721

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The classical problem of determining heat transfer performance of extended surfaces is revisited. An improved one-dimensional formulation of the energy equation is proposed, which takes approximately into account the nonuniformity of temperature distributions across the fin, as opposed to the classical approach, which neglects transversal temperature gradients. The resulting modified expressions are as simple as those obtained from the classical solution, but accuracy on heat transfer rates at the base and average temperature profiles along the fin is significantly improved, as demonstrated by numerical results for rectangular longitudinal fins and cylindrical pins. The present analysis extends the applicability range of the very simple one-dimensional formulation to considerably larger values of Biot number at the fin's lateral surface.

ISSN:0145-7632    

DOI:10.1080/01457639008939722

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Generalized thermodynamic and transport properties evaluation for nonpolar fluids was developed based on a four-parameter equation of state. Thermodynamic properties of the fluids were derived from thermodynamic relations and the equation of state, while the transport properties were evaluated through the use of the best available correlations. A computer code was subsequently developed with P and T as input to predict fluid properties in the superheated state as well as the saturation state including the saturated liquid properties. Specific volume, specific enthalpy, specific heat, viscosity, thermal conductivity, and surface tension are among the properties predicted. Predictions were compared to experimental data for different nonpolar fluids such as R-12, nitrogen, carbon dioxide, etc., and showed good agreement.

ISSN:0145-7632    

DOI:10.1080/01457639008939723

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/01457639008939724

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor