ISSN:0145-7632    

DOI:10.1080/01457638708962781

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This paper compares the experimental thermal hydraulic performance of an inclined lube bundle of staggered high finned tubes with that of the same bank in cross flow. The data are shown on a relative basis with the conventional cross-flow arrangement used as the reference layout. The results, presented as plots of heat transfer coefficient and pressure drop per row versus face velocity, are compared with other published data for bare and extended-surface tube banks. Correction factors that account for the deviation from cross-flow performance are presented. Estimated savings in plot area are shown for typical cases. Some possible cost reduction opportunities in specific fields of application are also suggested.

ISSN:0145-7632    

DOI:10.1080/01457638708962782

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Heat transfer coefficients are measured with water and 1.0-4.0% aqueous carboxymethylcellulose solutions flowing across a tube bank with a triangular pilch of 1.43 cm and a 1.50 pitch ratio. A parallel-plate channel model is used to define the flow in the bank. Based on this model a single-valued correlation is proposed for both Newtonian and inelastic non-Newtonian fluids.

ISSN:0145-7632    

DOI:10.1080/01457638708962783

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This paper presents some results of heat transfer deterioration (HTD) tests that were conducted on a finned smooth bore tube of 11 mm nominal ID to evaluate the effect of one-sided heating on the HTD phenomenon in once-through power boiler tubes, The one-side radiantly heated test sections were operated using upward steam-water flow at pressures of 179, 189, and 193 aim. Using peak heat flux at the tube wall crown as the correlating parameter and comparing with uniform heating data, the effects of one-sided healing on HTD quality and minimum heat transfer coefficient were found.

ISSN:0145-7632    

DOI:10.1080/01457638708962784

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A novel method of controlling heat flow from a surface is discussed. The method employs a nematic liquid crystal. A convective motion of the liquid crystal can be induced by subjecting it to either an AC or DC electric field. If the liquid crystal is used to transfer heat between two surfaces, the heat transfer rate can be controlled by varying the electric field strength. It is shown that the heat transfer rate through a thin layer of the liquid crystal can be increased by 25 limes when an electric field is present. This paper briefly discusses the physical phenomena that induce the convective motion in the liquid crystal due to the electric field. Experiments to determine the effects of field strength and gap distance on the enhancement of the heat transfer rate are discussed. An abrupt change in the rate of increase of the heat transfer rate with increasing voltage was found and is believed to be caused by a change in the fluid flow structure. This “heat switch” may find applications in aerospace and electronics cooling situations in which heat must be removed from a surface periodically while at other times the surface must remain insulated.

ISSN:0145-7632    

DOI:10.1080/01457638708962785

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Data are presented which demonstrate that two different types of condensing instabilities can exist in the horizontal U-tube heat exchangers used in moisture separator reheaters. The first instability was a cyclic type. The thermocouple readings showed that at times the subcooled condensate temperatures leaving certain lubes were cycling in phase and with the same period. The maximum values of these temperature traces never reached the saturation temperature. The second instability was a condensate chugging or water hammer type. The thermocouple readings indicated that vapor was entering some lube ends because of a stratified flow regime. It was then condensed, and all the condensate was discharged as a liquid plug.

ISSN:0145-7632    

DOI:10.1080/01457638708962786

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The transient operation of a multipass shell-and-tube heat exchanger with baffles is described by a multicell dynamic model where every cell represents a specific part of the exchanger. The proposed modeling technique can be used in a digital computer for the dynamic simulation of almost any type of shell-and-tube heat exchanger. The model includes time-dependent inlet conditions for both the cold and the hot streams. Hence, a number of start-up cases can be simulated and, once the system reaches a stationary operating point, a disturbance can be introduced in the inlet temperatures or the flow rates. This particular feature makes the model very useful not only for design purposes but also for transient analysis and control system design.

ISSN:0145-7632    

DOI:10.1080/01457638708962787

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

ISSN:0145-7632    

DOI:10.1080/01457638708962788

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor