摘要:

An explicit procedure for the design and sizing of balanced regenerators has been developed. A set of performance curves relating the thermal ratio, harmonic mean reduced length and period, and minimum cold fluid outlet temperature is presented. The specific characteristics of the regenerator's matrix including the heat transfer and pressure drop correlations are used to develop interrelations, represented by a set of three design curves, between these quantitites and the operating characteristics of the regenerator. The performance and design curves are used in the design procedure to determine the dimensions of the regenerator for the specified operating conditions.

ISSN:0145-7632    

DOI:10.1080/01457638108939582

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In recent articles evaporative cooling has proved to be the utmost air-side heat transfer augmentation. This kind of augmentation, when applied to steam condensers in power plants or to refrigerants in air conditioner systems, results in a lowering of the condensing temperature, even below ambient levels. This yields a remarkable increase of thermodynamic efficiencies of both processes and, therefore, a reduction of energy consumption. The combined heat and mass transfer processes in an evaporatively cooled device are very complex, due to the vast numbers of parameters which must be considered. Previous studies have assumed it impossible to perform any analysis unless many simplifying assumptions are made. The present article indicates that analysis can be performed where none of the assumptions originally used by Merkel are made. It is demonstrated by experiments that plate-fin tube and bare tube condenser performances can be predicted reliably. The insensitivity of the analysis to geometric design eliminates the need for extensive model tests and for production of correction and design factors for the design of evaporative condensers.

ISSN:0145-7632    

DOI:10.1080/01457638108939583

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Coefficients of heat transfer from a coiled Turbotec spiral tube to an air-fluidized bed were measured. Experimental parameters included particle diameter, number of flutes, flute pitch, groove depth, and air fluidizing velocity. Results indicated that the heat transfer coefficient generally increased with increasing fluidizing velocity. A maximum coefficient was observed in some cases. The heat transfer coefficient increased with decreasing particle size. The spiral tube with three flutes had the highest heat transfer coefficients. The spiral tube with four flutes and a pitch of 5.66 cm had gains in heat transfer duty as large as 40% compared to plain tubes. A correlation was formulated which fit the data within the range of experimental error.

ISSN:0145-7632    

DOI:10.1080/01457638108939584

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The effects of operating parameters on the steady-state heat flux and surface temperature at several locations on the cylinder head of a single-cylinder spark-ignition engine were investigated. The local heat flux was found to be strongly affected by engine speed and volumetric efficiency. Air-fuel ratio and spark timing had comparatively smaller effects. Coolant temperature, in the range of this study (300-380 K), had no effect on the average heat flux. Both the heat flux and the surface temperature varied considerably with the location of measurement. Except at very rich mixtures, the average heat flux was found to vary as the 0.65 power of the rate of fuel consumption.

ISSN:0145-7632    

DOI:10.1080/01457638108939585

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Correlation of the data for heat transfer between a fluid in turbulent flow and the entrance region of a tube is made for the entrance shapes normally used in heat exchangers. Equations representing the variation of the “average heat transfer” with tube length, Reynolds number, and Prandtl number are suggested.

ISSN:0145-7632    

DOI:10.1080/01457638108939586

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A case study method is employed to calculate the performance benefits and cost effectiveness of enhanced tubes for an application involving seawater on the tube side and ammonia boiling on the shell side. A porous boiling surface is used on the ammonia side, and eight basic geometries are evaluated for the water side. The analysis method selects the “optimum” enhancement dimensions for each geometry type. The optimum is de fined as the minimum material requirement for fixed heat duty and water-side pumping power. Heat exchanger size reductions of 55–67% are possible, depending on the tube-side enhancement type. The cost effectiveness of the enhanced tube designs are calculated relative to a plain tube exchanger for aluminum, copper, and titanium materials. Heat exchanger tubing cost reductions in the range of 10% are predicted for the titanium and copper tubes. Doubly enhanced aluminum tubes do not appear to provide heat exchanger cost reduction. A better application for enhanced tubes may involve increasing the UA value to provide a reduced LMTD. The reduced LMTD can be used to increase process thermodynamic efficiency, and thus offset the greater heat exchanger cost. The results of this study must be considered tentative until the water-side fouling characteristics of enhanced tubes are established.

ISSN:0145-7632    

DOI:10.1080/01457638108939587

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A general expression is developed for determining the degree of freedom in the design of a multiple-effect evaporation plant having some or all of the following auxiliary features: condensate flash tanks, liquor flash tanks, intermediate liquor heaters, multiple feeds, finisher unit, vapor bleed points, and twin-body evaporator effects. These degrees of freedom are utilized in specifying the process design variables for the evaporation plant.

ISSN:0145-7632    

DOI:10.1080/01457638108939588

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper reviews the state of the art in design methods for multicomponent condensation and boiling. In multicomponent condensation, a range of methods of varying complexity are available to calculate the local heat and mass transfer rates; the complexity depends on the detail with which the mass transfer resistances are calculated. These methods are briefly reviewed and their interrelationships along with those of their expertmental validation are discussed. Mixture boiling research has thus far followed different lines and very little effort has gone into understanding the liquid multicomponent diffusion process in boiling. Research work has been mainly concentrated on understanding the dynamics of bubble growth; heat transfer calculations are done using empirical corrections to coefficients calculated for pure fluids. The extensive research in these areas is reviewed and also the few previous studies on convective two-phase heat transfer to mixtures are described. In conclusion, possible design recommendations are offered. It is suggested that, although condensation and boiling heat transfer in mixtures have hitherto been studied separately, a combined research approach may produce further advances.

ISSN:0145-7632    

DOI:10.1080/01457638108939589

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor