Heat Transfer In System Research Articles

Effect of arc corrugation initiation on the thermo-hydraulic performance and entropy generation of the corrugated tube

It's important to know which corrugation start provides the best heat transfer performance with the least frictional losses. Thus, the present work focuses on the performance of corrugated tubes with different corrugation initiation. The different types of arc corrugations (outward arc, inward arc, outward arc-inward arc, and inward arc-outward arc) are used for assessing the entropy generation and thermo-hydraulic performance of the tubes under the application of constant wall heat flux. The different corrugation starts have a different effect on the thermo-hydraulic and entropy generation performance. For all the considered flow rates, the outward arc-inward arc configuration has the highest Nusselt number. The combination of inward and outward arc corrugations results in better heat transfer, but this improved heat transfer is at the expense of the pressure drop. The total and heat transfer entropy generation in the corrugated and smooth tubes reduce with an increment in the Reynolds number, while frictional entropy generation enhances. The outward arc-inward arc configuration results in the lowest total entropy generation at the highest Reynolds number and it is 0.398 W/K. All the corrugated tubes have entropy generation number less than unity, which is advantageous because of better heat transfer and lesser system irreversibility.

Thermal management of power electronics using nanofluids and nucleate boiling heat transfer technique

Nucleate boiling is an efficient solution for thermal management of power electronics where high-intensity heat flux needs to be transferred in a compact space. Both micro surfaces and nanofluids are used in literature to enhance the performance of nucleate pool boiling heat transfer systems; however, the effect of nanofluids over the microporous surface still needs to explore in several phase change heat transfer applications. The study’s objective is to examine the performance of nanofluid over microporous surfaces in Nucleate Boiling Heat transfer (NBHT) and performs a comparative analysis with plain and micro-porous surfaces. The study analyzed three ceramic (Alumina) nanofluids for nucleate pool boiling heat transfer (NBHT) over plain and microporous surfaces. The literature reported enhanced performance of nanofluids over the plane surface is verified in the study before proceeding to the detailed analysis over the microporous surface. Three different concentrations of 0.005%, 0.0005%, and 0.00005% were tested for the nanofluid. For plane surface, the critical heat flux (CHF) has been increased to 1035 [kW/m2] for Alumina from 783 [kW/m2] for deionized water, with the average increase in heat transfer coefficient (HTC) being 46.5%. The maximum CHF has been reported for micro-porous surfaces with a value of 1110 kW/m2. Out of the tested surfaces and fluids combination, the micro-porous surfaces with deionized water have been concluded as the most efficient surface with the highest heat transfer capacity for thermal management of high-power electronics and other high heat flux applications.

Heat transfer system and feedback temperature controller design for safety process operation of phosphorous acid potassium salts production

The phosphorous acid salts are widely used in the industry because of the effective treatment against various fungal diseases encountered in plants. The production process is exothermic and, with high temperatures around 94℃ achieved, significant risks were observed in terms of occupational health and safety. Therefore, the aim is to design a control system that will make this production process reliable for human health, economic and ecological damage. For this purpose, studies were carried out to determine the optimum operating mode, heat transfer system, and temperature controller design to prevent a sudden temperature rise. First, the overall heat transfer coefficient between the reactor and the jacket was determined as 51.0930 W/m2℃ and, the refrigerant was chosen as cooling water with 1.271 g/s flow rate which is relatively more economical and accessible. The model parameters of the system were determined with a detailed dynamic analysis by giving positive and negative step inputs to the cooling water flow rate and then obtaining model parameters through reaction curve and linear regression methods. By using the obtained model parameters theoretical P, PI and PID parameters were calculated by Cohen Coon and, Ziegler-Nichols approaches, and the success of controller parameters was tested, simulated with the MATLAB Simulink program and lastly, successful temperature control was achieved in the experimental system.

Dynamic control method of flue gas heat transfer system in the waste heat recovery process

A new flue gas waste heat recovery system and its control strategy are proposed based on the intelligent control technology and the principle of phase-change heat transfer. It is composed of flue gas heat transfer system (FGHTS) and air heat transfer systems (AHTS). The system pressure and outlet flue gas temperature are adjusted by blower frequency in the AHTS and the concentration of lithium bromide-water in the FGHTS, respectively. For FGHTS, a dynamic control method is proposed based on improved particle swarm optimization (PSO). In this method, the optimization ability and the convergence of PSO algorithm are affected by inertia weight and fitness function. The inertia weight strategy with the inverted S-shaped function (IWS-ISF) can enhance the global search ability in the initial stage and the local search ability in the later stage compared with other inertia weight strategies. Meanwhile, the integral time absolute error (ITAE) fitness function is improved by introducing overshoot into ITAE, and the improved fitness function is defined as IITAE fitness function. The improved PSO algorithm based on IITAE fitness function can reduce the overshoot of FGHTS by 66.23%. This paper can provide a theoretical basis for improving the control performance of the new system.

Multiphysics of multifunctional nanofluids based on different oxides nanoparticles and glycerol fluid

Nanofluid (NF) materials consisting of glycerol (Gly) and different inorganic nano oxides (TiO2, ZnO, Al2O3, and SiO2 for the oxides concentration of 0.01 wt% to the weight of Gly base fluid) were prepared by a two-step method through ultrasonic cavitation process. These nanofluids were investigated by employing an X-ray diffractometer (XRD), ultraviolet–visible (UV–Vis) spectrophotometer, 20 Hz to 1 MHz frequency range dielectric relaxation spectroscopy (DRS), ultrasonic interferometer, and rotational viscometer. The multiphysics of these nanofluids includes structural and optical properties, dielectric permittivity, electrical conductivity, conductivity relaxation, ultrasound velocity, adiabatic compressibility, acoustic impedance, viscosity, density, thermal conductivity, and viscoacoustic relaxation were characterized. The XRD patterns identified monodispersed and stable suspensions of these different characteristic nanoparticles in the hydrogen-bonded 3D supramolecular structure of ultra-high viscous glycerol fluid which were supported by their UV–Vis absorbance analyses. The energy band gap values of the TiO2 and ZnO containing nanofluids were found primarily ruled by the characteristic optical properties of these oxides nanomaterials. The complex dielectric and various electrical functions studied at 25 °C revealed that the suspension of different oxide nanoparticles in the glycerol fluid increased the static permittivity whereas reduced the direct current electrical conductivity which showed strong conductivity relaxation process dependence. The rheological measurements of the formulated nanofluids were performed over a shear rate range of 0.4–40 s−1 at temperatures of 25–55 °C. The linear relationship between shear rate and shear stress and also the shear rate-independent viscosity revealed the Newtonian behaviour of these nanofluids. The shear viscosity non-linearly decreased with the increase of temperature and exhibited the Arrhenius behaviour for all different oxides containing Gly-based nanofluids. The acoustic parameters of the nanofluids were altered unevenly with types of nano oxides and inferred some structure-property correlations. The promising technologically useable properties of these nanofluids were expected to impact their potential applications in optoelectronics, UV-blocking, sensing, nanodielectrics, energy storing and electric insulation, heat transfer systems, and also in materials processing for the development of innovative soft condensed devices.

Map of zoning of the territory of Kazakhstan by the average temperature of the heating period in order to select a heat pump system of heat supply: A case study

ABSTRACT The article considers feasibility of using air-water heat pumps to provide residential and industrial buildings with heating, cooling and ventilation requires taking into account a large number of different factors, such as the estimated and average outdoor temperature for the heating period in the considered climate region. The study of temperature fluctuations during the heating period will help to clarify the boundaries of areas of synchronous changes to solve the problems of climatological zoning, with the goal of establishing the heat production, energy transformation coefficient of the selected heat pump model. Using a statistical data and quantitative indicators of temperature variability across the territory of Kazakhstan, an interactive online map was developed based on the ArcGIS software, which integrated 67 weather stations in five regions. The developed zoning map is a qualitatively new information product that combines reliable data and a tool for analysis, visualization and data management of a professional GIS system. In general, in conclusion, we can say that our work is the creation of a map of the zoning of the territory of Kazakhstan according to the average temperature of the heating period in order to select a heat pump heat supply system is relevant in that we take into account the climatic conditions and the heating season to select a heat transfer system.

Analysis of the thermo-pneumatic properties of copper oxide-based nanofluids for pressure generation during membrane filtration

• The method used in the synthesis of nanoparticles, influences their shapes. • The stability of nanoparticles in nanofluids greatly affects their thermal conductivity enhancement. • The enthalpy of vaporization of volatile liquids is lowered when nanoparticles are dispersed in the fluid. • Nanofluids generally have improved thermal properties than their pure base fluids. The development of nanofluids and their application in heat transfer systems has been improved in recent years. These nanofluids enable heat engines to work at lower temperatures and utilize low-grade energy sources more efficiently especially in membrane filtration systems. In this study, CuO and Cu 2 O nanoparticles were synthesized, characterized, and used in preparing nanofluids. These nanofluids were then tested for vapour pressure generation enhancement in a diaphragm pump. Optimization of the thermo-pneumatic properties of the nanofluids was done through altering the nature, shape, size, and weight concentrations of the copper oxide nanoparticles in different base fluids. The equilibrium vapour pressure generated by a 0.1 wt% CuO nanofluid at 30 °C was found to be 100% higher than that of the pure working liquid. The 0.1 wt% CuO nanofluid also attained equilibrium pressures at a rate that was 37% faster on average than for the pure working liquid in the temperature range of 35 °C to 60 °C. he latent heat of vaporization of the pure volatile liquid was decreased by 15,7% and its thermal conductivity was enhanced by 26,2% by the 0.1 wt% CuO working liquid which showed the best stability at a pH of 6.

Recognizing Design Issues in Process Industry for Safer Design

Recognizing Design Issues in Process Industry for Safer Design

Dynamic Properties of a One-Dimensional Heat Transfer System with a Moving Heat Source

Dynamic Properties of a One-Dimensional Heat Transfer System with a Moving Heat Source

Hazop Study for Thermic Fluid Heater (At Industry by Heterogeneous Method)

Abstract: Hazard and Operability study(HAZOP) is a technique in which it is used to identify the possible hazards in a systematic and step by step manner through which consequences and deviations could be found in several ways during the design stage, commissioning stage and running stage. In thermic fluid heater the HAZOP study is carried out at the running stage by finding the possible deviations, causes, consequences through the use of guide word and providing appropriate recommendations to the actions based on the severity, occurrences and detection. The main process is to eliminate the hazards in a proactive manner in the thermic fluid heater process by using this qualitative approach and showing results based on the quantitative approach.The design and operation of thermal fluid-based heat transfer systems (hot oil systems) is often poorly understood and hence preventable accidents occur due to system failure.

Application of Nanocomposites with Thermal Barrier Coating in Heat Pump Heat Transfer Systems

Air-source heat pumps are highly valued in many fields because of their energy-saving and efficient characteristics and they have a good market prospect. However, with the continuous development of heat pump technology, the thermal barrier coating materials used in air-source heat pumps seriously limit their growth. Nanoparticles are the smallest microparticles found at present. They have many excellent characteristics, and the nanomaterials made of nanoparticles have surface activity that ordinary materials do not have. Based on this, this paper combines nanostructures with thermal barrier coatings to study the application of thermal barrier coatings based on nanocomposites in heat pump systems.

Supercritical Heat Transfer Characteristics and System Performance Analysis of R744 and Its Two Azeotropic Blends

Abstract A three-dimensional (3D) numerical model of the double-tubes heat exchanger was established by using fluent16.0 in this study. The supercritical flow and heat transfer characteristics of R744 and its two azeotropic blends in the gas cooler and their performance in the single-stage compression heat pump were investigated. The results showed that the peak value of the heat transfer capabilities of R744 was the highest, and that of R744/R170 was the lowest. With the increase in the pressure, the peak value of the heat transfer capabilities decreased, and the bulk temperature corresponding to the peak value of the heat transfer capabilities also increased. Moreover, the temperature of R744/R170 at the same position near the outlet of the tube section was lower under the different working conditions, which would be conducive in increasing the coefficient of performance (COP) of the system. Lastly, when R744 and its two azeotropic blends were employed in the single-stage compression heat pump system, the difference of COP between R744/R170 and R744 decreased with the increase of the outlet temperature in the gas cooler, and the difference of COP between R744/R41 and R744 increased.

An Analytic Orthotropic Heat Conduction Model for the Stretchable Network Heaters.

Compared with other physiotherapy devices, epidermal electronic systems (EES) used in medical applications such as hyperthermia have obvious advantages of conformal attachment, lightness and high efficiency. The stretchable flexible electrode is an indispensable component. The structurally designed flexible inorganic stretchable electrode has the advantage of stable electrical properties under tensile deformation and has received enough attention. However, the space between the patterned electrodes introduced to ensure the tensile properties will inevitably lead to the uneven temperature distribution of the thermotherapy electrodes and degrade the effect of thermotherapy. It is of great practical value to study the temperature uniformity of the stretchable patterned electrode. In order to improve the uniformity of temperature distribution in the heat transfer system with stretchable electrodes, a temperature distribution manipulation strategy for orthotropic substrates is proposed in this paper. A theoretical model of the orthotropic heat transfer system based on the horseshoe-shaped mesh electrode is established. Combined with finite element analysis, the effect of the orthotropic substrate on the uniformity of temperature distribution in three types of heat source heat transfer systems is studied based on this model. The influence of the thermal conductivity ratio in different directions on the temperature distribution is studied parametrically, which will help to guide the design and fabrication of the stretchable electrode that can produce a uniform temperature distribution.

Structural Identifiability Applied to a Heat Transfer System

Identifiability is an essential property of a dynamical model whose study should be addressed before performing any parameter estimation procedure. In this work, we study the structural identifiability of a heat transfer system by making use of the local state isomorphism theorem for two scenarios based on the available experimental measurements.

Javier Sanz - Structural Identifiability Applied to a Heat Transfer System

Structural Identifiability Applied to a Heat Transfer System

Experimental investigation of near-critical CO2 heat transfer performance in a closed natural circulation loop

The natural circulation system based on supercritical CO2 has attracted attention due to its simple structure and safety compared with the forced circulation system. This work presented an experimental investigation of the heat transfer characteristics of CO2 based on natural circulation. A closed loop natural circulation experimental system was built, which was specially designed for near-critical pressure experiments. The effects of filling ratio, coolant temperature, heat transfer rate and system pressure were carefully discussed. Experimental results illustrated the loop had excellent heat transfer capability at subcritical pressure, but the heating section showed heat transfer deterioration at supercritical pressures. The heat transfer behaviors were analyzed. From subcritical pressure to supercritical pressure in the loop, the heat transfer mechanism transforms from two-phase transition to supercritical single-phase convection. Gas-like layer and insulating layer will form near the wall in the heating section, resulting in a large thermal resistance at the wall for heat to enter the core flow.

Enhanced thermal energy storage performance of molten salt for the next generation concentrated solar power plants by SiO2 nanoparticles: A molecular dynamics study

Chloride molten salt is the most promising thermal energy storage materials for the next generation concentrated solar power (CSP) plants. In this work, to enhance the thermal performance of KNaCl2 molten salts, composited thermal energy storage (CTES) materials based on amorphous SiO2 nanoparticles and KNaCl2 were proposed and designed under the guidance of the material composition design strategy. The molecular dynamics simulation method has been conducted to investigate the thermal storage properties and analyze the mechanism of heat transfer improvement from the perspective of microstructure evolution, thermal diffusion properties and energy changes. Thermal conductivity, viscosity, and specific heat capacity of CTES materials at high temperatures with different volume fractions of nanoparticles were predicted to provide reference data for the design of heat transfer systems in CSP plants. The study discovered that increasing the volume fraction of nanoparticles increases the thermal conductivity and specific heat capacity of the systems significantly, with the maximum increase of 25.28% and 7.87%, respectively. Moreover, the enhancement of heat transfer characteristics is the result of the formation of a compressed interface layer with a thickness 5 Å on the outer surface of SiO2 nanoparticles. This work has important guiding significance for the material selection and composition design of molten salt-nanoparticle composite materials used for next-generation CSP plants.

An experimental study on the performance of water-based CuO nanofluids in a plate heat exchanger

The fluids added nanoparticle known as nanofluids, are used in various heat transfer systems due to some advantages they provide. The most prominent features are improvement in heat conduction and classical fluid is being replaced with working fluid in micro-channels, heating installations and various other areas where heat transfer is important. In the present study, the hydrodynamic and thermal performance of a plate heat exchanger in a modeled heating system with CuO nanofluid have been analyzed experimentally. The system consists of two basic parts as cooling water circuit and heating main circuit in which CuO nanofluid circulates. The experiments have been conducted at three different flow rate for the nanofluids with volume fractions of 0.27, 0.56, 0.81 and 1.1. The hydrodynamic parameters considered in the study are pumping power and pressure drop, while the thermal parameters are effectiveness of the heat exchanger, heat conduction coefficient and Nu number. The results of the study show that the plate heat exchanger takes the highest value of effectiveness 96% at ϕ = 0.81 in the plate heat exchanger. It has also been determined that the heat convection coefficient increased with the increase in nanopowder mixture ratio in accordance with the data in the literature. In addition, a new correlation for Nusselt number of Nu = 11.3453 ∗ Re0.199194 ∗ Pr0.305504 ∗ ϕ0.00965827 has been proposed for CuO nanofluid including volume fraction (ϕ) as well as Reynolds and Prandtl numbers.

Enhancing the energy and exergy performance of a photovoltaic thermal system with [formula omitted]-shape collector using porous metal foam

The use of porous media in heat transfer systems leads to a rise in the heat transfer surface area and pressure loss of the working fluid, the first of which is desirable and the second is undesirable. The effect of porous metal foam positioning on the energy and exergy performances of an air-based photovoltaic thermal system with ∇-shape collector is investigated in this research. For this purpose, porous foam is placed once in the channel between the photovoltaic panel and the collector (system II), again in the channel between the collector and the back insulation wall (system III), and finally in both channels (system IV). The results are compared with each other and with those of the system without porous metal foam (system I). The energy balance equation is written for each part of the system, and the resulting system of equations is solved with a code written in MATLAB. The mathematical modeling was performed for several values of air mass flow rate. The results showed that the maximum overall energy efficiency (61.53–111.49%) and overall exergy efficiency (14.18–17.46%) belong to systems II and IV.

Phase change heat transfer and energy storage in a wavy-tube thermal storage unit filled with a nano-enhanced phase change material and metal foams

Latent heat thermal energy storage plays a key role in the thermal management of heat transfer systems, shifting thermal loads, and developing renewable systems. A latent heat thermal energy storage (LHTES) unit can store/release a significant amount of heat in a compact space. However, the main issue of LHTES units is their poor heat transfer characteristics. Thus, the thermal response time of most LHTES is low, and they cannot absorb/release the required energy in a timely manner. Hence, the heat transfer enhancement approaches such as using nano additives, metal foams, and extended, wavy surfaces are promising approaches to improve the heat transfer capability of LHTES. The present study aims to address the impact of using wavy tubes in a composite phase change material and metal foam LHTES unit. A phase change heat transfer model based on enthalpy-porosity was introduced and solved via the finite element approach. The influence of nanoparticle volumetric fraction (VFna), tube wave amplitude (A), tube wave number (N), and the porosity coefficient (ε) was investigated on the charging time, stored energy, and heat transfer behavior of the LHTES unit. According to the findings, employing metal foams and nanoparticles enhances heat transmission and decreases charging time. A simple tube with no wavy surface produces lower pressure drop and better charging power compared to a wavy tube.