ISSN:0145-7632    

DOI:10.1080/01457639808939923

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Professor Arthur E. Bergles has made major contributions in a number of areas in heal transfer. This article presents a review of 300 papers published by him, and with his students and co-workers, through December 1996. Professor Bergles' research work can be broadly categorized into seven areas: (1) enhanced heat transfer, (2) two-phase flow and heat transfer, (3) heat transfer to refrigerants (boiling and condensation), (4) cooling of electronic components, (5) laminar internal flow, (6) review and general articles, and (7) history of heat transfer. This research, conducted over more than 30 years, has produced a wealth of high-quality experimental data, theoretical models, and practical applications. One of the major objectives of this article is to highlight these contributions and identify their sources, to facilitate future researchers and designers in developing new theoretical models and in designing industrial equipment. The present article presents a comprehensive survey of his research work.

ISSN:0145-7632    

DOI:10.1080/01457639808939924

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this article, four methods of heating hot water in domestic storage tanks are investigated experimentally to determine the unsteady temperature gradients formed in the storage tank. These four methods involved heating the water with an electric hot water heater, a heat pump parallel to the storage tank, a temperature-controlled heat pump, and a temperature-controlled heat pump with return water. The first heating method was studied on a real electric hoi water heater system, while the other three heating systems were experimentally simulated. Temperatures were measured as a function of lime at different vertical locations on the centerline of a vertical storage tank. The temperature distributions and, more important, the availability of hot water for the different types of consumptions were compared. It was concluded that the four heating methods may be ranked from the most favorable to the least favorable as follows: temperature-controlled heat pump, electric hot water heater system, temperature-controlled heat pump with a return loop, and lastly the heat pump parallel to the storage tank without any temperature control.

ISSN:0145-7632    

DOI:10.1080/01457639808939925

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

For ammonia-water generator-absorber heat exchanger (GAX) systems to work at high coefficient of performance, the heat and mass transfer components have to operate at optimum performance within a narrow range of conditions for the recovery of internal energy, in the present work, an analysis is performed to study the absorption process of an ammonia-water vapor mixture by an aqueous solution of ammonia in a falling film absorber. The combined heat and mass transfer processes involved arc analyzed through an integral formulation of the continuity, momentum, energy, and diffusion equations. The effects of vapor flow direction relative to the solution, cooling ability, ammonia concentration of solution and vapor, and interfacial momentum and heat transfer rate on absorption processes are investigated. The characteristics of the absorption process are found to be governed by the relative significance of the mass transfer resistance and the driving forces between the solution film and the vapor mixture.

ISSN:0145-7632    

DOI:10.1080/01457639808939926

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An analysis is made to quantify the effect of flow maldistribution on the performance of a laminar, counterflow, high-effectiveness heat exchanger. An investigation of the ability of thermally connected fins in one passage (screen mesh) to correct the uneven heat transfer distribution from the maldistributed mass flow in the other passage is made. A heat transfer model is developed for both passages. A parametric study presents the effect of adding thermal paths to correct the uneven heat transfer. A redefined fin efficiency is proposed to incorporate the fins' ability to correct uneven heat transfer. Data are compared to the model.

ISSN:0145-7632    

DOI:10.1080/01457639808939927

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This theoretical study of the heat flow within finned heat exchangers is of considerable practical importance because of the extensive utilization of finned surfaces for heat transfer enhancement in applications varying from air-cooled heat exchanges in the process industries to heat-rejection equipment in space vehicles.

ISSN:0145-7632    

DOI:10.1080/01457639808939928

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this communication, simple formulas (based on the latest experimental tabulated data) for 11 physical properties of liquid ordinary water substance at saturation state—saturation pressure, density, volumetric thermal expansion coefficient, specific volume of saturated vapor, specific enthalpy, specific heal, latent heal of vaporization, thermal conductivity, dynamic viscosity, Prandtl number, and surface tension as a function of temperature (from 0 to 150°C)—which are used in heat transfer calculations for heat exchangers in heating systems and also for many other technological applications, are presented. Also, the uncertainties of these formulas are given. In most practical cases the pressure of liquid water is within the range from 1 to 10 absolute bar, which makes it possible to neglect the effect of pressure. All properties of saturated liquid water calculated with the recommended formulas are tabulated with a temperature increment of 5°.

ISSN:0145-7632    

DOI:10.1080/01457639808939929

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In spacecraft thermal design and analysis practice, the lumped-parameter network formulation is used extensively to construct mathematical models. The models lake the form of a system of coupled, nonlinear, first-order ordinary differential equations (ODEs). The number of equations may vary from a few tens to a few thousands. It is necessary to solve these equations in an efficient and economical way. This article reviews various methods available for the numerical solution of ODEs. General-purpose codes available for this are discussed. Numerical experiments are conducted to investigate the efficiency of various methods. The results indicate that the Crank-Nicholson method with provision for automatic selection of step size to control the local truncation error is a very good choice for the solution of spacecraft thermal problems.

ISSN:0145-7632    

DOI:10.1080/01457639808939930

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor