Thermoeconomic Optimization of a Ventilation Air Heater in a Backpressure Combined Heat and Power Plant

1989 ◽  
Vol 203 (4) ◽  
pp. 255-267
Author(s):  
T J Kotas ◽  
D S Kibiikyo
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Structural Investigation ◽  
Combined Heat And Power ◽  
Structural Method ◽  
Pressure Losses ◽  
Air Heater ◽  
Second Stage ◽  
Two Stages ◽  
Plant Efficiency

In this paper a method of optimization of plant components is demonstrated for the case of a ventilation air heater in a backpressure combined heat and power (CHP) plant. The method, known as thermoeconomic optimization, combines the concepts of exergy analysis with those of economic analysis. The optimization is carried out in two stages. First the heat-exchanger geometry is optimized for a range of different fixed heat-transfer areas using the trade-off between irreversibility due to pressure losses and that due to heat transfer over a finite temperature difference. In the second stage the economically justified cost of the heat-exchanger is determined using a version of thermoeconomic optimization known as the structural method. The concept of the coefficient of structural bonds is discussed and its use in structural investigation and thermoeconomic optimization is explained. Potential for further improvement in the plant efficiency through optimization is discussed with reference to a diagram of exergy flows and irreversibility rates known as the Grass-mann diagram.

Shellside Waterflow Pressure Drop Distribution Measurements in an Industrial-Sized Test Heat Exchanger

1988 ◽  
Vol 110 (1) ◽  
pp. 60-67 ◽  
Author(s):  
H. Halle ◽  
J. M. Chenoweth ◽  
M. W. Wambsganss
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Operating Cost ◽  
Power Requirement ◽  
Pressure Drops ◽  
Pressure Losses ◽  
Finned Tubes ◽  
Heat Exchanger Design ◽  
Isothermal Water

Throughout the life of a heat exchanger, a significant part of the operating cost arises from pumping the heat transfer fluids through and past the tubes. The pumping power requirement is continuous and depends directly upon the magnitude of the pressure losses. Thus, in order to select an optimum heat exchanger design, it is is as important to be able to predict pressure drop accurately as it is to predict heat transfer. This paper presents experimental measurements of the shellside pressure drop for 24 different segmentally baffled bundle configurations in a 0.6-m (24-in.) diameter by 3.7-m (12-ft) long shell with single inlet and outlet nozzles. Both plain and finned tubes, nominally 19-mm (0.75-in.) outside diameter, were arranged on equilateral triangular, square, rotated triangular, and rotated square tube layouts with a tube pitch-to-diameter ratio of 1.25. Isothermal water tests for a range of Reynolds numbers from 7000 to 100,000 were run to measure overall as well as incremental pressure drops across sections of the exchanger. The experimental results are given and correlated with a pressure drop versus flowrate relationship.

Heat Transfer Characterization of a Finned-Tube Heat Exchanger (With and Without Condensation)

1990 ◽  
Vol 112 (1) ◽  
pp. 64-70 ◽  
Author(s):  
S. A. Idem ◽  
A. M. Jacobi ◽  
V. W. Goldschmidt
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Factor Versus ◽  
Finned Tube ◽  
Transfer Coefficients ◽  
Number Range ◽  
Tube Heat Exchanger ◽  
Pressure Losses ◽  
Finned Tube Heat Exchanger

The effects upon the performance of an air-to-water copper finned-tube crossflow heat exchanger due to condensation on the outer surface are considered. A four-tube, two-pass heat exchanger was tested over a Reynolds number range (based on hydraulic diameter) from 400 to 1500. The coil was operated both in overall parallel and overall counterflow configurations. Convective heat and mass transfer coefficients are presented as plots of Colburn j-factor versus Reynolds number. Pressure losses are, similarly, presented as plots of the friction factor versus Reynolds number. Enhancement of sensible heat transfer due to the presence of a condensate film is also considered.

Optimizing Effectiveness of Double Pipe Heat Exchanger Using Nanofluid and Different Porous Fins Arrangement

2021 ◽  
Author(s):  
Avinash Kumar ◽  
Vinay Arya ◽  
Chirodeep Bakli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Design Parameters ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Porous Fin ◽  
Transfer Characteristics ◽  
Porous Fins ◽  
Double Pipe ◽  
Pipe Heat

Abstract A numerical study is carried out to investigate the effect of porous fins in counter-flow Double Pipe Heat Exchanger (DPHE). Four DPHE with different porous fin arrangements is simulated for varying Darcy number, fin height, and the number of fins and compared with the conventional DPHE with no porous fins. The Darcy-Brinkman-Forchheimer equation is employed to model the flow in the porous fins considering fixed Re = 100. Al2O3-H2O nanofluid and water are used as hot and cold fluids respectively. Stainless steel is used as porous material with a porosity of 0.65. Results are evaluated in terms of effectiveness and Performance Evaluation Criterion (PEC). The effectiveness of the heat exchanger is used to analyze the heat transfer characteristics whereas the PEC is used to analyze the heat transfer characteristics considering pressure losses also. We evaluated maximum enhancement in thermal performance using effectiveness analysis and through PEC study we evaluated optimal effectiveness and corresponding design parameters. It is shown that utilizing porous fins in DPHE enhances the heat transfer by 134.3%. However, along with enhancement in heat transfer, the pressure losses also enhance which makes the application of porous fin non-viable. Therefore, using the PEC study we obtained optimal design parameters (Da = 10−3, hf = 4 cm, and n = 30) which adapts porous fin viable with enhancement in heat transfer by 66.38%.

scholarly journals Design and analysis of double-pipe heat exchanger using both helical and rotating inner pipe

2021 ◽  
Vol 25 (2 Part B) ◽  
pp. 1545-1559
Author(s):  
Tarkan Koca ◽  
Aydın Citlak
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cold Water ◽  
Straight Tube ◽  
Empirical Formulas ◽  
Pressure Losses ◽  
Annular Gap ◽  
Double Pipe

In this study, the effects of rotating straight and helical inner tubes is experimentally discussed to determine heat transfer and pressure losses in rotating tubes and improve heat transfer. The outer tube remains stationary and the inner tube is rotated at different speeds in the work. In the experiments for straight and helical tubes, the flow regime is turbulent. According to the results, Nusselt number, pressure loss, and efficiency of heat exchanger were gauged. In addition, empirical formulas were obtained for each pipe type. It is observed that as the rotation speed of the pipe increases, the heat transfer rate increases. The pipe that provides the best increase in heat transfer is the five helixes tubes. At five helixes tubes; after the number of revolutions per minute exceeds 300, the increase in heat transfer rate has almost halt. At five helixes tubes and at 300 rpm speed when the flow of cold water through the annular gap with the fluid passing through the inner tube is equal, the heat transfer increases by 124.10% compared to straight tube, 23.47% compared to two helixes tubes, 7.92% compared to three helixes tubes, and 1.65% compared to four helixes tubes. Maximum effectiveness was obtained while rotating with 300 rpm in five helixes pipes.

Methods to Reduce Hot Return Condensate Temperature Without Compromising Plant Efficiency for Combined Heat and Power Plants

2017 ◽  
Author(s):  
Anil Kumar Addanky
Keyword(s):  
Heat Transfer ◽  
Water Quality ◽  
Power Plant ◽  
Power Plants ◽  
Treatment Plant ◽  
Water Treatment Plant ◽  
Combined Heat And Power ◽  
Higher Plant ◽  
Improve Water Quality ◽  
Plant Efficiency

This paper describes five methods to achieve effective heat transfer and higher plant efficiency when condensate return temperature is high and treatment is needed to improve water quality in the water treatment plant before sending it to the deaerator for a combined heat and power plant.

Spiral Heat Exchanger Utilizing Dimpled Primary Surface

2007 ◽  
Author(s):  
B. Glezer ◽  
I. Borisov ◽  
A. Khalatov ◽  
S. Kobsar
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Total Pressure ◽  
Rectangular Cross Section ◽  
Entry And Exit ◽  
Operational Parameters ◽  
Counter Flow ◽  
Excessive Pressure ◽  
Pressure Losses ◽  
Structural Support

Paper presents a small demonstrator of the heat exchanger technology based on spiral counter-flow arrangement of dimpled primary surfaces. The heat exchanger has been developed as result of collaborative effort between Ukrainian and US scientists, authors of the paper. The heat transfer surfaces were fabricated out of stainless steel foil with arrays of spherical dimples augmenting heat transfer on the hot (gas) sides and corresponding spherical protrusions enhancing heat transfer on the cold (air) sides of the heat exchanger passages. About thirty primary surface geometries have been studied prior to selection of the presented configuration. Protruding diagonal ribs were introduced between lines of dimples on each side of the low-pressure passages, which were sandwiched between high-pressure passages, to prevent collapsing of the heat transfer surfaces under the pressure difference of 3.5 Bar. The counter-flow heat exchanger was assembled out of 24 (12 pairs) spiral rectangular cross-section channels, which were formed between dimpled surfaces. Development work was focused on optimizing thermal effectiveness and pressure losses within the heat exchanger core with little attention devoted to the entry and exit sections of the heat exchanger. The paper provides details of the experimental rig that was build for testing of the heat exchanger simulating operational parameters, which were representative for microturbine application. The overall recuperator effectiveness of 80–82% at total pressure loss of 10% was measured, including entry and exit losses. Excessive pressure losses in the entry-exit sections and headers were found to be main contributors to these losses. It was revealed that losses in the headers were related to inadequate structural support of the foil surfaces in the lower pressure passages, causing these passages to be partially closed. Design improvement measures addressing this issue are being evaluated with a goal of achieving 90% effectiveness with total pressure losses of less than 5% of the air inlet pressure.

Optimization of Plate Heat Exchangers with Intermittent Ridges

2015 ◽  
Vol 752-753 ◽  
pp. 820-827 ◽  
Author(s):  
Vaclav Dvorak
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Objective Function ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Optimization Method ◽  
Plate Heat Exchanger ◽  
Plate Heat ◽  
Pressure Losses ◽  
Computational Mesh

Research of devices for heat recovery is currently focused on increasing the temperature and heat efficiency of plate heat exchangers. The goal of optimization is not only to increase the heat transfer or even moisture but also reduce the pressure loss and possibly material costs. This study deals with a plate heat exchanger with wall shaped by intermittent ridges. We used software fluent and user defined deforming to deform computational mesh and create various heat exchange walls with different number of ridges and different number of set-offs. The intention of the set-offs is to discompose boundary layer inside channels created by ridges, mix the temperature field and thus intensify the heat transfer. We used previously formulated objective function, which is a linear combination of efficiency and pressure loss, and a simple local method to optimize the heat exchanger for required pressure loss. It was found that the objective function surface is monotone and unimodal, but is not smooth. The global optimums were identified and it was shown that the optimal wall shape has no set-off for low pressure losses. The optimal count of ridges and optimal count of set-offs rise with higher required pressure loss. It was proved that the suggested objective function is suitable for optimization of a counterflow plate heat exchanger, but use of a global optimization method would be beneficial.

A Method to Solve the Heat Transfer Problem in a Circular Duct With an Internal Longitudinal Fin

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
E. K. Vachagina ◽  
A. I. Kadyirov ◽  
K. I. Sibgatova ◽  
V. S. Yunusova ◽  
E. P. Gurmanchuk
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Transfer Problem ◽  
Analytical Form ◽  
Heat Transfer Problem ◽  
Constant Wall Temperature ◽  
Circular Duct ◽  
Second Stage ◽  
Two Stages ◽  
Variable Separation Method

Abstract The heat transfer problem in a circular duct with an internal longitudinal fin is investigated under constant wall temperature. Different fin heights are considered. The problem is solved in two stages. In the first stage, the distribution of axial velocity corresponding to the fully developed laminar viscous flow is obtained using comsolmultiphysics. In the second stage, the variable-separation method is implemented to reduce the solution of the energy transfer equation under constant wall temperature to an eigenvalue problem. Finally, the temperature distribution is obtained in the analytical form as a series expansion. The influence of fin height on the Nusselt number and the friction factor is discussed.

Microturbine Recuperation: Turbulators and Their Effect on Power Density and Thermal Efficiency

2012 ◽  
Author(s):  
Kaylee M. Dorman ◽  
Sergio Arias Quintero ◽  
Lucky V. Tran ◽  
Mark Ricklick ◽  
J. S. Kapat
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Power Density ◽  
Thermal Efficiency ◽  
High Reliability ◽  
Negative Effects ◽  
Reduced Pressure ◽  
Pressure Losses ◽  
Surface Areas ◽  
Compact Size

Microturbines have proven to be a vital part of the distributed power generation field due to their low emissions, compact size, high reliability and low maintenance. However, microturbines operate at low pressure ratios and relatively low turbine inlet temperatures that limit cycle efficiency. In order to overcome these limitations, microturbines often utilize a recuperator or regenerator to achieve the optimal balance between improved heat rates and reduced pressure ratios across the turbine. Recuperator design aims to achieve maximum effectiveness while staying reasonably compact, which creates the need to study novel heat transfer surfaces for compact heat exchanger application. In this study, experimental data of heat transfer augmentation and friction factor augmentation values for various turbulator geometries is used to determine the required heat exchanger volume to achieve 85%, 90%, and 95% effectiveness. A parametric analysis of various recuperator channel surface areas and turbulator geometry data will be utilized to determine the feasibility of increasing thermal efficiency while remaining compact to avoid large, negative effects on power density for a hypothetical gas turbine modeled after the Turbine Technologies, Ltd. SR-30 Turbo-Jet Engine. The turbulators considered in this study consist of 4 wedges, 4 ribs, and a dimpled geometry. The results will highlight the applicability of surface features in recuperator designs that can improve overall efficiency for microturbines. Results present the power density, thermal efficiency, and specific fuel consumption as functions of heat exchanger channel Reynolds number for heat exchangers implementing different turbulators. It is shown that dimples at low Reynolds numbers yield 85% effectiveness with only a 8% reduction in power density and 90% effectiveness with only a 12% reduction in power density. Ribs and wedges also perform well but suffer from high pressure losses due to their obtrusive design.

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