Optimal Performance of an Endoreversible Four-Heat-Reservoir Absorption Heat-Transformer

2004 ◽  
Vol 11 (02) ◽  
pp. 147-159 ◽  
Author(s):  
Xiaoyong Qin ◽  
Lingen Chen ◽  
Fengrui Sun ◽  
Chih Wu
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Coefficient Of Performance ◽  
Heat Reservoir ◽  
Cycle Model ◽  
Surface Areas ◽  
Heating Load ◽  
Temperature Levels ◽  
Heat Transformer

Based on an endoreversible absorption heat-transformer cycle model operating between four temperature levels with linear (Newtonian) heat transfer law, the fundamental optimal relation between the specific heating load and the coefficient of performance, the optimal temperatures of the working substance, and the optimal heat transfer surface areas of the four heat exchangers are derived by using finite-time thermodynamics. Moreover, the effects of the cycle parameters on the cycle characteristic are studied by numerical examples. The results obtained herein can provide some guidance for the optimal design of absorption heat-transformers.

scholarly journals Enhancement of heat exchangers with metal foams

2019 ◽  
Vol 9 (1) ◽  
pp. 15-28
Author(s):  
Mete Ozturk ◽  
Bahadır Dogan
Keyword(s):  
Heat Transfer ◽  
Surface Area ◽  
Heat Exchangers ◽  
Energy Demand ◽  
Emerging Technologies ◽  
Metal Foams ◽  
Heat Transfer Surface ◽  
Technological Equipment ◽  
Surface Areas

Removal of the heat is becoming a vital issue for safer operations of today’s technological equipment. The necessity of heat exchangers is underlined at this stage for the sake of the emerging technologies, which are producing more heat than before by the increment of the higher energy demand during their operations. Several methods have been suggested to improve the efficiency of the heat exchangers in last decades by the researchers including the extension of the heat transfer surface by the larger surface areas surrounding the channels. In addition to this fundamental approach (extension of the surface area), alternate methods have been released too including the implementation of metal foams to the heat exchangers as for the extension of the surface. Keywords: Heat exchangers, surface extension, metal foams.

Model of irreversible finite-heat capacity heat reservoir absorption heat transformer cycle and its application

2007 ◽  
Vol 221 (12) ◽  
pp. 1643-1651 ◽  
Author(s):  
L Chen ◽  
X Qin ◽  
F Sun
Keyword(s):  
Performance Characteristic ◽  
Variable Temperature ◽  
Coefficient Of Performance ◽  
Cycle Performance ◽  
Working Fluid ◽  
Cycle Model ◽  
Heating Load ◽  
Internal Irreversibility ◽  
General Relations ◽  
Heat Transformer

An irreversible four-temperature-level absorption heat transformer cycle model with variable-temperature heat reservoirs is established, which considers the heat resistances between the heat reservoirs and the working fluid, the internal irreversibility due to internal dissipation of the working fluid, and the heat leakages between the heat reservoirs and the surrounding. The general relations between the heating load and the coefficient of performance are derived, and the general performance characteristic and the optimal performance characteristic are obtained using numerical examples. Moreover, the cycle model and the derived general relations are confirmed by comparing the prediction results of the model and engineering analysis results for real absorption heat transformer, and the cycle performance characteristic are discussed. The results obtained herein can provide some guidance for the optimal design of absorption heat transformer.

Failure Analysis of Heat Exchangers

2021 ◽  
pp. 3-19
Author(s):  
Dusan P. Sekulic
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Failure Analysis ◽  
Thermal Energy ◽  
Solid Surface ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Tubular Heat Exchanger ◽  
Erosion Corrosion ◽  
Different Temperatures

Abstract Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.

Finned Elliptical Tubes and Their Application in Air-Cooled Heat Exchangers

1966 ◽  
Vol 88 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Franz J. Schulenberg
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Great Success ◽  
Sufficient Criterion ◽  
Tube Heat Exchanger ◽  
Circular Tubes ◽  
Fin Tube

Finned circular tubes have been used exclusively in air-cooled heat exchangers built for the American petroleum and chemical industries. In Europe, however, other tube geometries, in particular, finned elliptical tubes, have been used with great success. In this paper, the theory of the finned elliptical tube and its application in air-cooled heat exchangers are discussed. Finned circular and elliptical tubes are compared; it is shown that the developed heat transfer surface alone is not a sufficient criterion for predicting the performance of an air-cooled fin-tube heat exchanger.

scholarly journals Modelling and Analysis of Plate Heat Exchangers for Flexible District Heating Systems

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4141
Author(s):  
Serafym Chyhryn
Keyword(s):  
Heat Transfer ◽  
Power Systems ◽  
Heat Exchangers ◽  
District Heating ◽  
Estimation Procedure ◽  
Computational Effort ◽  
Seamless Integration ◽  
Plate Heat ◽  
Temperature Levels ◽  
Flexible Operation

Seamless integration of district heating (DH) and power systems implies their flexible operation, which extends their typical operational boundaries and, thus, affects performance of key components, such as plate heat exchangers (PHXs). Despite that the heat transfer in a PHX is regulated by mass flows, flexible operation and demand variations cause shifts in temperature levels, which affects the system operation and must be efficiently accounted for. In this paper, an overall heat transfer coefficient (OHTC) model with direct relation to temperature is proposed. The model is based on a linear approximation of thermophysical components of the forced convection coefficient (FCC). On one hand, it allows to account for temperature variations as compared to mass flow-based models, thus, improving accuracy. On the other hand, it does not involve iterative lookup of thermophysical properties and requires fewer inputs, hence, reducing computational effort. The proposed linear model is experimentally verified on a laboratory PHX against estimated correlations for FCC. A practical estimation procedure is proposed based on component data. Additionally, binding the correlation to one of varying parameters shows reduction in the heat transfer error. Finally, operational optimization test cases for a basic DH system demonstrate better performance of the proposed models as compared to those previously used.

Crystallization Fouling in Plate Heat Exchangers

1993 ◽  
Vol 115 (3) ◽  
pp. 584-591 ◽  
Author(s):  
B. Bansal ◽  
H. Mu¨ller-Steinhagen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Velocity ◽  
Wall Temperature ◽  
Heat Exchangers ◽  
Calcium Sulfate ◽  
Surface Reaction ◽  
Heat Transfer Surface ◽  
Plate Heat

Crystallization fouling of calcium sulfate was investigated in a plate and frame heat exchanger. The effects of flow velocity, wall temperature, and CaSO4, concentration on the fouling rates have been investigated and the distribution of scale along the heat transfer surface has been observed. The measured fouling curves are compared with predictions from a surface reaction controlled model.

Heat-Transfer and Flow-Friction Characteristics of Crossed-Rod Matrices

1960 ◽  
Vol 82 (3) ◽  
pp. 199-213 ◽  
Author(s):  
A. L. London ◽  
J. W. Mitchell ◽  
W. A. Sutherland
Keyword(s):  
Heat Transfer ◽  
Electrical Resistance ◽  
Heat Exchangers ◽  
Air Conditioning ◽  
Nuclear Reactor ◽  
Heat Transfer Surface ◽  
Friction Behavior ◽  
Flow Friction ◽  
Nuclear Reactor Fuel ◽  
Fuel Elements

The paper presents a continuation of the program on porous media heat-transfer and flow-friction behavior previously covered in References [2b] and [3b]. All the previous results of interest to the designer on woven-screen matrices and crossed-rod matrices of a random configuration are summarized here. In addition, new design results for the regular in-line and regular staggered crossed-rod-matrix configurations are reported. Matrices of the type considered here may find application as heat-transfer surface geometries for nuclear-reactor fuel elements, for electrical resistance heaters and for periodic-flow-type heat exchangers used for gas-turbine regenerators, and some air-conditioning applications.

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