Design Of Heat Transfer Equipment Research Articles

EXPERIMENTAL INVESTIGATION OF TWO-PHASE PRESSURE DROP IN THE STRAIGHT ADIABATIC TUBES

The pressure drop is the significant constraint in designing the single or multiphase flow systems. Innovative technologies, such as nuclear power plants and enhanced oil recovery processes, can be designed more efficiently with the knowledge of the multiphase pressure drop phenomenon. The higher pressure drop induces the lower system efficiency. There is a scarcity of literature representing the steam-water flow at atmospheric system pressure in the adiabatic tubes. The experiments are performed to get the two-phase pressure drop in the adiabatic tube for the effective design of heat transfer equipment used for diverse applications. The adiabatic tubes of 8, 13.7, and 18 mm diameter, having 15 × 10<sup>2</sup> mm length, are experimented for 32-495 kg/m<sup>2</sup>s mass flux and 0-1 vapor quality. The pressure drop in the adiabatic tubes increases nonlinearly with the increase of vapor quality. The pressure drop is influenced significantly by the diameter of the tube. The pressure drop is lesser in the 18 mm tube compared to the 8 and 13.7 mm tubes for constant vapor quality and mass flow rate. The increase of the mass flux increases the pressure drop monotonically. The pressure drop is higher at higher mass flux and higher vapor quality in the lesser diameter tube. The experimental pressure drop is compared to various correlations. A correlation is suggested to measure the two-phase pressure drop during steam-water flow at atmospheric system pressure in the adiabatic tubes.

Techno-economic feasibility analysis of zeotropic mixtures and pure fluids for organic Rankine cycle systems

• Optimization of net present value of ORC units using mixtures and pure fluids. • Zeotropic mixture R1234yf/i-butane (53/47) reaches highest net present value. • Sensitivity analysis employed for comparing R1234yf/i-butane and R1234yf. • Result robust to variations in fluid cost, electricity price and cost models. In this paper the techno-economic feasibility of employing zeotropic mixtures as working fluids in organic Rankine cycle power systems is assessed. For an application case based on the utilization of low temperature geothermal heat at 135 °C, the net present value of the organic Rankine cycle system was maximized by optimizing the process variables and heat transfer equipment design parameters. Parametric studies detailing the effect of the assumed electricity price and the employed equipment cost estimation models were carried out. The working fluids propane, i-butane, i-pentane, R1234yf, and their mixtures were selected for investigation, since they have shown promising performance in previous studies. The results suggest that the highest net present value (43.1 M€) is reached by the mixture R1234yf/i-butane (53.3/46.7), which is 2.1 M€ higher compared to the most economically feasible pure fluid R1234yf for an electricity price of 0.252 €/kWh. The results of the sensitivity analyses suggest that the techno-economic benefit of using the mixture is robust to variations in the electricity price, the cost of the working fluid, and the equipment cost estimation models. In the comparison of R1234yf based mixtures to propane based mixtures, the inclusion of model for estimating the turbine efficiency is assessed to have a relevant influence on the results. The results also indicate that the R1234yf/propane, R1234yf/i-butane, and R1234yf/i-pentane result in lower cooling water flows and thereby lower cooling tower costs compared with R1234yf.

The Specifics of Design and Prediction of Thermohydraulic Characteristics of Thermosiphons

Recommendations are given on designing thermosiphons (TS) prepared on the basis of the experience that the authors gained in designing more than 4000 TSs for heat-recovery steam generators and the results of long-term investigations and tests carried out to study thermohydraulic and corrosion processes in vertical and inclined TSs filled with steam-water mixture. The results of similar studies performed by other authors are analyzed. References are given to the regulations on the design of heat transfer equipment for thermal and nuclear power stations. The requirements for TS construction materials, the degree of TS filling with water, and the TS vacuum level are outlined. Whether the evacuation of TS may be abandoned was assessed. Measures are proposed to prevent depressurization on water freezing in TSs. Recommendations are given on the calculation of thermohydraulic characteristics and steam-and-gas distribution in vertical or inclined TSs. The conditions of displacement by a steam flow of noncondensable gases, including air, to the top of the condensation zone in a thermosiphon are considered. Various regimes of axial heat transport and heat transfer are described for pure steam condensation (including film condensation, bubble condensation, distribution of different regimes of steam condensation, and condensate cooling along the height of the condensation zone during “flooding”). Heat transfer in the steam condensation from an air-steam mixture (the diffusion component of thermal resistance), maximum power, and the conditions for poorer cooling of the TS heating zone (“flooding,” steam separation at the upper generatrix of the heating zone in an inclined thermosiphon) are examined. Thermosiphons feature a countercurrent flow of steam and its condensate in a single flow with the same mass flowrates. Hence, a special case of “flooding” affecting the maximum power of the thermosiphon, the effect of the incoming steam flow on the heat transfer rate during film condensation, steam-and-gas distribution in a top-plugged channel, corrosion processes in thermosiphons, and hydrogen diffusion through the thermosiphon wall should also be studied.

Nonlinear Finite Element Analysis-Based Flow Distribution and Heat Transfer Model

A new strategy for fast, approximate analyses of fluid flow and heat transfer is presented. It is based on Finite Element Analysis (FEA) and is intended for large yet structurally fairly simple heat transfer equipment commonly used in process and power industries (e.g., cross-flow tube bundle heat exchangers), which can be described using sets of interconnected 1-D meshes. The underlying steady-state model couples an FEA-based (linear) predictor step with a nonlinear corrector step, which results in the ability to handle both laminar and turbulent flows. There are no limitations in terms of the allowed temperature range other than those potentially stemming from the usage of fluid physical property computer libraries. Since the fluid flow submodel has already been discussed in the referenced conference paper, the present article focuses on the prediction of the tube side and the shell side temperature fields. A simple cross-flow tube bundle heat exchanger from the literature and a heat recovery hot water boiler in an existing combined heat and power plant, for which stream data are available from its operator, are evaluated to assess the performance of the model. To gain further insight, the results obtained using the model for the heat recovery hot water boiler are also compared to the values yielded by an industry-standard heat transfer equipment design software package. Although the presented strategy is still a “work in progress” and requires thorough validation, the results obtained thus far suggest it may be a promising research direction.

Why ionizing radiation enhances surface wettability

Radiation-Induced Surface Activation is an inherent phenomenon where surfaces that are exposed to gamma irradiation are observed to undergo an increase in wettability. This increase in wettability as a result of the ionizing radiation exposure has so far been demonstrated to have a pronounced impact on Leidenfrost temperature and two-phase fluid dynamics. Test results from previous experiments have shown that incorporation of this effect on heat transfer equipment design may increase the thermal-hydraulic margin leading to higher thermal efficiency. However, the mechanism behind the increased wettability is not clearly understood. In the present work, three different materials (Zircaloy-4, 316 stainless steel, and copper) were exposed at two different dose rates with use of two different gamma irradiation facilities. A detailed surface characterization on the post-irradiated samples is carried out to understand the changes in surface chemistry, wettability and surface morphology. It is observed from the experiments that the increase in wettability upon irradiation depended on the total dose and not on the dose rate. Moreover, localized oxidation and porosity induced by radiolysis was seen to be the predominant mechanism behind increased wettability which leads to improved Leidenfrost temperature.

Investigation Into Effective Viscosity, Electrical Conductivity, and pH of γ-Al2O3-Glycerol Nanofluids in Einstein Concentration Regime

Nanofluids have shown great promise in the design of heat transfer equipment. In this study, the viscosity of γ-Al2O3 glycerol nanofluids was investigated in the Einstein's volume concentration regime (≤2%). The effect of temperature, volume concentration, electrical conductivity, and pH was investigated at a constant shear rate. The nanoparticles were 20–30 nm. γ-Al2O3 glycerol nanofluids samples were prepared, followed by ultrasonication at two different time period of 3 and 6 h. The effects of volume concentration on the effective viscosity, electrical conductivity, and pH were all monitored in the temperature range of 20–70°C. It was found that classical models underpredicted the experimental data while an empirical model overpredicted the experimental data. Furthermore, the electrical conductivity and pH were significantly affected by temperature and volume fraction.

Suitability of some commonly available software for unconventional condenser analysis

Computer aided design of heat transfer equipment, i.e., thermal-hydraulic design of process and power apparatuses for heat exchange, is an essential part of industrial practice. There are several world-renowned software tools of which the most-used ones are those developed by Heat Transfer Research, Inc. (HTRI® Xchanger Suite®), Aspen Technology, Inc. (Aspen Exchanger Design & Rating), and Chemstations, Inc. (CHEMCAD™). Advantages of these sophisticated software systems are unquestionable particularly in the field of conventional heat exchanger solutions. This paper, however, aims to compare and discuss features of the above-mentioned packages in case of unconventional equipment via a specific industrial problem in which components having common geometries could not be used.For this purpose, thermal-hydraulic analyses of an unconventional steam condenser is performed using educational versions of the three packages with operating parameters at the inlet of the apparatus, thermo-physical properties of streams, and geometry of the apparatus being taken from the operator of the condenser. Based on comparison of the obtained results and condenser operating data it can be seen that although some of the available software tools offer relatively large sets of functionalities, there still is opportunity for development of flexible tools – especially those capable of evaluating non-standard geometries.

Evaluation of the thermodynamic effectiveness of a plate heat exchanger integrated into an experimental single stage heat transformer operating with Water/Carrol mixture

This paper analyzes the effectiveness of a Plate Heat Exchanger (PHE) used as an economizer integrated into an experimental Single Stage Heat Transformer (SSHT). The heat exchanger effectiveness (η), sometimes referred as thermal efficiency, is an important parameter for the design of heat transfer equipment. Two thermodynamic methods for η evaluation are shown. The overall heat transfer coefficient (U) and the individual convective heat transfer coefficients (h) were calculated for Water/Carrol mixture. Four SSHT experimental tests runs were carried out, in order to evaluate the η. The economizer effectiveness ranged from 0.69 to 0.71. Finally, the η effect for Coefficient of Performance (COP) is shown as a function of absorber temperature.

Studies on Thermal, Textural and Quality Parameters of Multiplier CO 4 Onion Bulb (Allium cepa L.var aggregatum Don.)

Thermal properties are essential for predicting the temperature distribution within the foods and to allow optimum design of heat transfer equipment. Study of thermal, textural properties and quality parameters are necessary to understand the behavior of onion during storage and consumption. All these properties were measured and a data base for the CO 4 variety was formed. Thermal properties of the fresh and three months stored onion bulbs were estimated. The specific heat, thermal conductivity and volumetric heat capacity were linearly related and also the thermal diffusivity indirectly related with moisture content of the fresh and three months stored onion. Penetration load and crushing load of fresh and stored onion bulbs were determined. The mean values of total soluble solids (TSS), colour parameter ‘a’ and pyruvic acid content were 16.91±0.90 to 17.29 ± 0.62 per cent, 15.23 ± 10 to 14.58±0.67 and 4.58±0.41 and 4.25±0.39 μmol/g respectively, for the fresh and three months stored onion. All the properties were assessed at an average moisture content of 83.45±1.10 per cent (wb) for the fresh onion bulbs and 81.82±1.01 per cent (wb) for the three months stored onion CO 4 variety.

Computational Fluid Dynamics in Research and Design of Heat Exchangers

This paper gives a brief summary of computational methods in heat transfer equipment, such as CFD (computational fluid dynamics), methods for thermal problems (computational heat transfer), and turbulence modeling for single-phase applications in the design, research and development of heat exchangers. Details of the finite volume method and their extension to arbitrary geometries are presented. An overall presentation of turbulence modeling is provided. Some of the most common commercially available computer codes are listed. Ways to apply CFD to heat exchangers are discussed. The paper presents results from some examples of application of CFD methods for real heat exchangers in order to demonstrate how such methods can be used in the research, development, and design of heat transfer equipment. Limitations and shortcomings as well as needs for further research are also highlighted.

Optimal heat exchanger network synthesis with the detailed heat transfer equipment design

This paper presents an optimisation model for the synthesis of heat exchanger networks (HEN) including the detailed design of the equipments formulated as a decomposition method. Shell and tube pressure drops and fouling are considered, as well as mechanical aspects, like shell and tube bundle diameters, internal and external diameter of tubes, number of tubes, number of baffles, number of shells, tube length, tube arrangement and the fluid allocation in the heat exchanger. The optimisation model is based on area, energy and pumping costs. The algorithm combines two distinct models, in a decomposition method, a mixed integer non-linear programming (MINLP) superstructure simultaneous optimisation model for the heat exchanger network synthesis considering stream splitting and a MINLP model for the detailed equipment design, following rigorously the standards of the TEMA. Two examples from the literature are used to test the algorithm developed, and the results confirm the achievement of the optimum HEN configuration with the detailed heat exchangers design, following the TEMA standards.

Recent Advances on Heat Transfer Equipment Design and Optimization—Selected Papers from PRES 2004 Conference

This editorial provides an overview of a special issue dedicated to the 7th conference on Process Integration, Modeling and Optimization for Energy Saving and Pollution Reduction—PRES 2004. Eight papers have been selected and peer-reviewed covering various subjects of heat transfer engineering, focusing on the recent development of various features of heat transfer equipment design and optimization. This is the fourth special issue of Heat Transfer Engineering dedicated to selected contributions from PRES conferences [1, 2, 3].

Solid–gas equilibrium in chemical heat pumps: the NH 3–CoCl 2 system

The design of heat transfer equipment used in chemical heat pumps requires a knowledge of the temperature at which heat is produced during the synthesis reaction and the temperature at which it is used during the decomposition reaction. The existing equilibrium data in the literature for the reaction, CoCl 2·2NH 3+4NH 3=CoCl 2·6NH 3 was obtained at pressures of 1 atm or less. Data at greater pressures were measured in this investigation. The measurements reported here were more complex than a single van’t Hoff equilibrium line. Pseudo-equilibrium hysteresis behaviour (equilibrium lines were a function of solid concentration) was observed between the synthesis reaction and the decomposition reaction. The widths of the hysteresis loops were found to be a function of heating rate. When heating rate was eliminated as a variable by maintaining the temperature constant for several hours, the hysteresis loops became narrower. Extrapolation of the data suggests that the hysteresis might be eliminated entirely by maintaining the temperature for extremely long times. Nevertheless, in all circumstances it appears that the conversion of the salt would be a function of temperature. The experimentally measured bivariant behaviour was contrary to monovariant behaviour which had been anticipated and has been discussed in the literature. Fixed bed chemical heat pumps normally operate as batch reactors which have different operating conditions in the synthesis and decomposition cycles. As the temperatures of the batch reactors are cycled relatively rapidly in real chemical heat pumps, true equilibrium conditions are not established. Therefore, when the rate of temperature change in the batch reactors is known, the pseudo-equilibrium hysteresis loop data corresponding to the same heating rate can be used. This hysteresis phenomena can make a 15°C temperature difference in the specifications of the heat transfer equipment.

Boiling and Nonboiling Heat Transfer to Electrolyte Solutions

Heat transfer to electrolyte solutions is a common engineering problem in the chemical and petrochemical industries. Nevertheless, only a few experimental investigations of heat transfer to electrolyte solutions can be found in the literature. To improve design of heat transfer equipment and to understand fouling characteristics, it is important to know the clean heat transfer coefficient of electrolyte solutions, and whether heat transfer to electrolyte solutions can be predicted with models found for less complicated fluids. A wide range of experiments were performed to determine the effects of various dissolved salts on forced-convective, pool boiling, and subcooled flow-boiling heat transfer. The effect of dissolved salts on bubble size and nucleation site density were also investigated. The measured heat transfer coefficients are compared with recommended correlations for the different heat transfer modes.

System for automated design of heat-transfer equipment

System for automated design of heat-transfer equipment

Thermal analysis as an aid to monomer plant design

AbstractThe thermal data needed for the design of heat transfer equipment and distillation columns for the manufacture of a new vinyl monomer, diacetone acrylamide, were rapidly and effectively provided by differential scanning calorimetry. A method has been developed for determining the effects of inhibitors and metals on the polymerization of the vinyl monomer. The latter was an aid in the selection of materials of construction. DSC was used to determine the total inhibitor concentration in the monomer. Selection of inhibitors was facilitated by information derived from thermal analysis.

Instationäre wärmetechnische rechnungen als grundlage für die spannungsanalyse von dampferzeugern und wärmetauschern

Zusammenfassung The assessment and design of heat-transfer equipment is based on thermal calculations. For conventional components and in many cases also for nuclear applications this basis was restricted to the steady-state thermal performance, whereas for the transient behaviour estimates derived from the experience with existing installations had to be used. The reason for this unsatisfactory state of the art was, that — although exact theoretical calculation models did exist — the actual performance of such calculations is cumbersome and time consuming. Results have been obtained only for simple cases or with simplified calculation models. Computer programs enabling an exact prediction of the transient behaviour of steam generators were made available only recently. The Waagner-Biro computer codes TRANS were developed especially for the analysis of the dynamic (transient) behaviour of once-through steam generators with any geometry and flow arrangement. Temperature, mass flow rate and pressure of both primary and secondary medium can be introduced as time dependent functions. Combinations of the above variables, simultaneously or consecutively, are possible. The results include time functions of temperature, mass flow rate and pressure of both media at any location in the steam generator. The codes can also be used for heat exchangers; no limitations exist concerning the type of the primary and secondary medium. Also for heat transfer between more than two media — with and without change of phases — the codes are applicable. The complexity of the heat and mass transport problems dealt with in the TRANS programs necessitated a limitation in the geometric barrier between primary and secondary medium. This barrier has been fixed to be a tube; its diameter, wall thickness and material can be selected independently for each section. More complicated geometries like headers and tube plates cannot be introduced into the program. Such components are of less or no importance for heat transfer calculations which are performed in the TRANS programs, but in general represent the most critical and determining parts from the point of view of stress analysis. Thus, separate codes, TRALIN and FINTRAN, have been elaborated by means of which temperature fields, both stationary and transient, for bodies of any geometric shape can be calculated. Thermal data are introduced as boundary conditions, e.g. time functions of local temperature and heat transfer coefficient of one or more media in contact with a specific face of the body; the geometry is represented by a fine subdivision of the structure, similar to the “finite-element” method in stress calculation. This has the advantage that the TRALIN/FINTRAN results can be used directly in finite element stress programs or that in a following program step the stress calculation can be performed directly on the basis of the transient temperature distribution at any given time.