ISSN:0145-7632    

DOI:10.1080/01457639808939916

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Mechanisms of heat transfer enhancement of single-phase turbulent flow within roughened tube bundles supported by rod or ring supports have been analyzed according to the results of velocity and turbulence distributions of fluid measured within tube bundles with LDV and the experiments of heat transfer and flow resistance in tube bundles. Performance of heat transfer enhancement of rough tube bundles supported by rod or ring supports have been evaluated and compared to each other.

ISSN:0145-7632    

DOI:10.1080/01457639808939917

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Efficiency assessment of heat exchangers ensures appropriate use of the available energy. This article presents the concept of a heat exchanger on-line expert system based on qualitative reasoning. Using confluence of the heat exchanger effectiveness defined by the NTU (number of transfer units) concept for the simple parallel-stream heat exchanger, the methodology is developed to be used for the description of the generic behavior of the heat exchanger system. In this respect, particular attention was paid to the recognition of those situations leading to the degradation of the effectiveness of the heat exchanger. The article describes the selection of the diagnostic variables, and their on-line measurements including the logging system for monitoring and acquisition of the data.

ISSN:0145-7632    

DOI:10.1080/01457639808939918

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Heat transfer experiments with a saturated CaS04solution were carried out in a closed-loop test rig containing an externally heated test section. Reproducible fouling curves were measured for the solution without fibers. The buildup of deposit was asymptotic, which implied that the fouling process was a combination of crystallization and particulate fouling. The addition of a small quantity (less than 0.05 mass percent) of softwood chemical pulp fiber to the bulk reduced the rate of fouling significantly. At 0.05 mass percent fiber addition, no fouling was measured in the test rig during 7 days of continuous running. The addition of fibers reduced the rate of deposit buildup and potentially offers a new method of fouling mitigation. Only a low concentration of fibers is needed, and the nontoxic fibers are easily removed.

ISSN:0145-7632    

DOI:10.1080/01457639808939919

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

When steam-water two-phase mixtures flow in inclined or horizontal tubes that are heated by alternating current, the circular angle-dependent temperatures on the outer radius imply that the inner heat transfer coefficients also vary with circular angle. The inner heat transfer coefficients are difficult to measure directly, but may be determined with the aid of inverse heat conduction theory. The direct model calculates the temperature field inside a half-pipe. This is subjected to a given heat transfer coefficient angular profile on its inner radius. The inverse heat conduction model calculates the temperature field under the conditions of the measured discrete temperatures and the heat-insulated boundary on the outer radius. Variation of the cylinder heat conductivity and specific resistance versus temperatures are considered in both models. The prediction accuracy is analyzed with a numerical test. The inverse heat conduction problem solution is verified as a useful tool for obtaining the inner heat transfer coefficient.

ISSN:0145-7632    

DOI:10.1080/01457639808939920

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The present study investigates the effect of longitudinal wall conduction on the thermal performance of a direct-transfer type, single-pass, crossflow heat exchanger with nonuniform inlet temperatures. The exit mean temperatures and effectiveness with four kinds of arrangement that include longitudinal wall conduction are calculated by the numerical method. The capabilities of heat recovery with respect to four kinds of arrangements are compared, and a sequence of these four arrangements is displayed in terms of suitability. In addition, the wall conduction affects the thermal performance for each arrangement unfavorably, and the deterioration is affected by the parameters of NTU and nonuniform inlet temperature distribution.

ISSN:0145-7632    

DOI:10.1080/01457639808939921

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method is presented to represent a curve by means of a polygonal. The curve, defined in a given interval, is divided into several arcs, and linear chords are drawn between the limits, such that the lines are close enough to the curve to satisfy a convergence criterion. The criterion states that the approximation is satisfactory if the ratio between the area under the curve arc and the area under the straight segment is equal to 1 within a prescribed error.

ISSN:0145-7632    

DOI:10.1080/01457639808939922

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor