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Über dieses Buch

This book presents new methods of numerical modelling of tube heat exchangers, which can be used to perform design and operation calculations of exchangers characterized by a complex flow system. It also proposes new heat transfer correlations for laminar, transition and turbulent flows. A large part of the book is devoted to experimental testing of heat exchangers, and methods for assessing the indirect measurement uncertainty are presented. Further, it describes a new method for parallel determination of the Nusselt number correlations on both sides of the tube walls based on the nonlinear least squares method and presents the application of computational fluid dynamic (CFD) modeling to determine the air-side Nusselt number correlations. Lastly, it develops a control system based on the mathematical model of the car radiator and compares this with the digital proportional-integral-derivative (PID) controller. The book is intended for students, academics and researchers, as well as for designers and manufacturers of heat exchangers.

Inhaltsverzeichnis

Chapter 1. Introduction

This monograph presents numerical modeling and experimental testing of heat exchangers with a particular focus on finned-tube cross-flow devices. Such exchangers are widely used in many industries, e.g., in power plants, oil refineries, chemical plants, as well as in gas and heating engineering and air-conditioning. Their characteristic feature is that liquid flows inside the tubes and gas flows in the direction perpendicular to the tube axis.
Dawid Taler

Chapter 2. Mass, Momentum and Energy Conservation Equations

Heat can be transferred by means of the following three fundamental processes:
• conduction,
• convection,
In practice, these three kinds of the heat transfer co-occur. Heat conduction plays the most significant role in solid bodies, whereas in gases and liquids convection and radiation prevail. Radiation differs from conduction and convection in that it can also occur in a vacuum. Like thermodynamics, the heat transfer phenomenon is based on mass, momentum, and energy conservation equations. The first law of thermodynamics is the law of energy conservation or, simply speaking, the energy balance equation.
Dawid Taler

Chapter 3. Laminar Flow of Fluids in Ducts

This chapter is devoted to the laminar flow of incompressible fluids with constant physical properties.
Dawid Taler

Chapter 4. Turbulent Fluid Flow

Turbulent flows involve irregular fluctuations in velocity, pressure and temperature. The momentary velocity vector varies from mean velocity in terms of both value and direction. All parameters characterizing the turbulent flow, such as velocity, pressure and temperature, oscillate around the mean value over time.
Dawid Taler

Chapter 5. Analogies Between the Heat and the Momentum Transfer

Heat exchangers, boilers, and many other devices are commonly calculated using the heat transfer coefficient. For several dozens of years, a search has been going on for simple $${\text{Nu}} = f\left( {\text{Re} ,\,\Pr } \right)$$ relations that could be applied in practice to calculate the heat transfer coefficient α on the solid body surface as a function of the fluid velocity, temperature, and physical properties.
Dawid Taler

Chapter 6. Developed Turbulent Fluid Flow in Ducts with a Circular Cross-Section

This chapter presents derivation of the Nusselt number correlations for fluid flows over a flat surface. The formulae are also used to calculate the heat transfer coefficient on the inner surface of tubes. However, the coefficient values obtained in this manner should be treated as an approximation only, due to the fact that the fluid flow velocity distributions in a tube and over a flat surface differ from each other. The fluid mean temperature used to calculate the heat transfer coefficient is also different.
Dawid Taler

Chapter 7. Basics of the Heat Exchanger Modelling

This chapter presents the basic mass, momentum and energy conservation equations derived for the flowing medium, determination of the temperature distribution in the walls of tubes with a circular cross-section and with a complex shape, and determination of the heat transfer coefficient for non-finned and finned tubes.
Dawid Taler

Chapter 8. Engineering Methods for Thermal Calculations of Heat Exchangers

This chapter presents two fundamental methods of thermal calculations which can be applied to various types of heat exchangers. The first to be discussed is the method based on the logarithmic mean temperature difference (LMTD), which is commonly used in Europe, and the second is the ε-NTU method (ε—heat exchanger effectiveness, NTU—the number of heat transfer units), which is mainly popular in the USA.
Dawid Taler

Chapter 9. Mathematical Models of Heat Exchangers

In this chapter, formulae will be derived that define the temperature of fluids in four basic types of the heat exchanger. If in a given cross-section the hot and the cold medium temperatures (T h and T c , respectively) and the heat transfer coefficients on the hot and the cold medium side (α h and α c , respectively) are known, it is possible to find the wall temperature T w .
Dawid Taler

Chapter 10. Mathematical Modelling of Tube Cross-Flow Heat Exchangers Operating in Steady-State Conditions

This chapter presents two numerical models and one exact analytical model of a two-pass, two-row heat exchanger being a cross-flow plate fin-and-tube heat exchanger made of oval tubes. The computation results obtained using the two numerical models will be compared to those obtained using the exact analytical model.
Dawid Taler

Chapter 11. Assessment of the Indirect Measurement Uncertainty

The heat exchanger experimental testing usually draws on indirect methods of determining quantities appearing in thermal and flow calculations. One example of such indirect measurement is determination of the mean heat transfer coefficient values on the sides of the two mediums flowing in the heat exchanger. The indirect measurement uncertainty assessment is often a complex task, which is presented in detail in this chapter.
Dawid Taler

Chapter 12. Measurements of Basic Parameters in Experimental Testing of Heat Exchangers

The primary aim of the heat exchanger testing is to measure the exchanger pressure drops Δp h and Δp c on the side of the hot and the cold medium, respectively.
Dawid Taler

Chapter 13. Determination of the Local and the Mean Heat Transfer Coefficient on the Inner Surface of a Single Tube and Finding Experimental Correlations for the Nusselt Number Calculation

The local heat transfer coefficient cannot be determined experimentally if the temperature and heat flux values on the channel inner surface and the fluid mass-averaged temperature are unknown.
Dawid Taler

Chapter 14. Determination of Mean Heat Transfer Coefficients Using the Wilson Method

The method of the heat transfer coefficient measurement described in Chap. 14 is challenging to apply to determine the local or the mean heat transfer coefficient in heat exchangers due to the difficulty of calculation or measurement of the heat flux on the tube inner surface.
Dawid Taler

Chapter 15. Determination of Correlations for the Heat Transfer Coefficient on the Air Side Assuming a Known Heat Transfer Coefficient on the Tube Inner Surface

A car radiator experimental testing results will be used to find the correlation for the air-side Nusselt number Nu a assuming that the water-side Nusselt number correlation is known.
Dawid Taler

Chapter 16. Parallel Determination of Correlations for Heat Transfer Coefficients on the Air and Water Sides

This chapter is devoted to the parallel determination of unknown coefficients in the Nusselt number correlations on the air and the water side (Nu a and Nu w , respectively) based on the testing of the car radiator of a 1600 cm3 spark-ignition combustion engine.
Dawid Taler

Chapter 17. Determination of Correlations for the Heat Transfer Coefficient on the Air Side Using CFD Simulations

Correlations describing the air-side heat transfer coefficient in cross-flow finned-tube exchangers can be found using the CFD (Computational Fluid Dynamics) tools.
Dawid Taler

Chapter 18. Automatic Control of the Liquid Temperature at the Car Radiator Outlet

The control system regulating the car engine coolant temperature has a considerable impact on the engine performance, reliability, and life. One of the system tasks is to ensure the optimum temperature, possibly constant in time, to make sure that the engine is properly lubricated and high thermal stresses are avoided in the engine head and cylinder block.
Dawid Taler

Chapter 19. Concluding Remarks

This monograph is devoted to issues related to calculations and testing of heat exchangers. It presents a detailed discussion of the mass, momentum and energy conservation equations, which—after appropriate simplifications—are used in the heat exchanger mathematical modelling. Considerable attention is given to cross-flow tube heat exchangers.
Dawid Taler

Backmatter

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