ISSN:0145-7632    

DOI:10.1080/01457638508939620

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Experiments are described in which shell-side heat transfer coefficients for a shell-and-tube heat exchanger were determined from mass transfer measurements. The mass transfer experiments were carried out using the naphthalene sublimation technique. In utilizing the technique, the external surface of the tubes is coated with a film of naphthalene, which sublimes when exposed to an air flow. Mass transfer coefficients were measured for fully developed flow conditions at each of the tubes in the cross section. These coefficients were transformed to heat transfer coefficients by employing the analogy between heat and mass transfer. Detailed pressure drop measurements were made internal to the heat exchanger, and the axial pressure distribution indicated that the fluid flow was fully developed downstream of the first compartment. The cross-sectionally averaged mass (heat) transfer coefficients and the pressure drop were compared with the predictions from two well-established methods for the thermal-hydraulic design of shell-and-tube heat exchangers.

ISSN:0145-7632    

DOI:10.1080/01457638508939621

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper presents a description of three computer algorithms developed to perform rating calculations of commercially available cooling towers, evaporative fluid coolers, and evaporative condensers. The paper illustrates the various simulations that are possible, including varying wet-bulb, inlet and exit temperatures, different fluid flow rates, altitude, or combinations of the above. The heat and mass transfer “characteristic equations, ”as a function of the fluid flow rates for a given evaporative heat exchanger, are derived from the manufacturer's rating data on one operating point, e.g., at the rating point. Or, one may use independently developed “characteristic equations” for any packing or tube bundle geometry of interest. The algorithms provide capability to predict the heat exchange capacity at any weather or process condition. They also allow the plant engineer to assess the effect of varying the air flow rate on the fan power for specified operating conditions. Example cases are analyzed for each of the three evaporative exchanger types, in order to illustrate the utility of the simulation algorithms. For the cases illustrated, the predicted heat duty is within 3% of the manufacturer's rating data.

ISSN:0145-7632    

DOI:10.1080/01457638508939622

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An extremely compact cross-flow heat exchanger is described. The exchanger is constructed by furnace-brazing together a stack of hundreds of stainless-steel sheets. The resulting structure is leak-tight and very strong, but fluid channels as small as 51 μm (0.002 in) are not plugged by excess brazing material. Measurements of heat transfer between water and liquid propylene flowing through the heat exchanger are in excellent agreement with calculations based on exchanger geometry and fluid properties.

ISSN:0145-7632    

DOI:10.1080/01457638508939623

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

This paper discusses procedures for the prediction of pressure gradients, flow patterns, entrainment, and void fraction on the shell side of heat exchangers and in pipes during horizontal flow.

ISSN:0145-7632    

DOI:10.1080/01457638508939624

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The problem of heat transfer in a four channel plate heat exchanger involving the effect of unsymmetrical heat transfer in the outer two channels is studied analytically and experimentally. An energy balance over a control volume yields the governing system of differential equations that has been solved exactly for the cases of parallel flow and counterflow to give the temperature distribution in the channels. The results show that zero or even reversed heat flow may be obtained at the middle plate of the heat exchanger. Expressions for the heat exchanger efficiency and the log-mean temperature difference correction factor in terms of the heat capacity rate ratio and the number of transfer units are presented. Experiments carried out with a counterflow plate heat exchanger show reasonable agreement between the experimentally observed and the theoretically calculated efficiencies and mean driving temperature differences.

ISSN:0145-7632    

DOI:10.1080/01457638508939625

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor