Abstract Formation of mineral scale, particularly calcium carbonate, has long been a concern in domestic appliances such as boilers, steamers and washing machines. In this work, the formation of inorganic deposits was studied on solid surfaces and in the bulk solution as a result of evaporation of potable water. Scale precipitation was evaluated on metallic samples for various bulk temperatures, surface

ABSTRACT Horizontal tube falling film evaporators are commonly used in multiple-effect distillation plants for seawater desalination. Scale formation on the evaporator tubes strongly depends on film flow characteristics. The thickness of the liquid film on a horizontal tube was measured in a test rig with a high-resolution optical micrometer. Furthermore, scale formation was studied with artificial

ABSTRACT Fouling in condensers of thermal power stations can reduce their heat load, which increases the backpressure of the steam turbine and cause deleterious effects to the energy output. A complete analysis of the condenser behavior must handle the exchanger as an integrated part of an entire cooling system, which also encompasses hydraulic equipment such as the pumping system. This paper presents

13th Heat Exchanger Fouling and Cleaning Conference - 2019, Warsaw, Poland. Heat Transfer Engineering. Accepted .

Abstract To promote the development of enhanced tubes in heat exchangers, forced convection experiments were carried out using R410A in the annular region outside enhanced tubes. Three enhanced tubes were investigated by experiments to evaluate the heat transfer performance; with different surface structures of novel fin arrays (C-enhanced tube), newly-developed combined dimples (L-enhanced tube) and

Abstract Three micro heat pipes belonging to different types are selected as the research objects due to their lowest thermal resistance and the steadiest operation according to published literatures. They are the pulsating heat pipe with corrugated configuration (CPHP), the flat-plate heat pipe with eight microchannels (FPMHP) and the radial pulsating heat pipe (RPHP). A mathematical model common

ABSTRACT This study presents a simple method for predicting the temperature of the base-plate of a central processing unit (CPU) cooler. These coolers are used in desktop computers to keep the CPU at an optimum operating temperature. The technique discussed here combines a computational approach with an analytical solution. The cooler has a base-plate, four heat pipes, and many plate-fins that transfer

Abstract Microstructures of wicks have been widely investigated on their performances of heat and mass transfer and various structures have been attempted. As have been optimized by the nature, the microstructures inside plants may also be applied on the wick structure. In this paper, four substomatal cavity structures are chosen to investigate the influence of the structural parameters on the diffusional

Abstract Numerical simulations are carried out to infer the heat transfer performances of perforated trapezoidal vortex venerators (PTVG) in a turbulent regime, for Reynolds numbers ranging from 7500 to 15000. The flow geometry consists of a circular pipe fitted with seven arrays of perforated tabs, similarly, arranged as in the high efficiency vortex static mixer (HEV™) used in the industry. Four

Abstract Compact recuperative heat exchangers are critical components in supercritical carbon dioxide (sCO2) waste heat to power conversion systems. To investigate their thermohydraulic performance, a model based on the segmental design and the ε-NTU method has been developed. Four different types of heat exchanger have been considered: printed circuit heat exchanger with straight channels (PCHE-SC);

ABSTRACT The multi-objective optimization of heat exchangers can provide a reliable solution for both improved efficiency and reduction in cost. A computer program for the thermal and hydraulic design optimization of shell and tube heat exchangers is developed. Its user-friendly graphic user interface provides an excellent feature for the teaching, learning and preliminary design of shell and tube

ABSTRACT Photovoltaic/thermal (PV/T) systems are taking up an increasing market share owing to a high overall solar energy efficiency. An innovative PV/T system that combines amorphous silicon cells and micro-channel loop heat pipes is proposed in this paper. It can overcome problems of large thermal stress at fluctuating temperature and frosting in winter which exist in conventional PV/Ts using crystalline

Abstract Structural morphology and surface features of torrefied cornstalk are investigated under the given torrefaction temperatures of 250 °C, 270 °C, or 290 °C and the different atmospheres at Air or N2. The surface functional groups and pore volume distribution tests are conducted experimentally with Fourier Transform Infrared Spectrometer and N2 adsorption/desorption methods, respectively. Meanwhile

ABSTRACT The study investigates experimentally and numerically the problem of turbulent convective heat transfer and pressure drop in a packed bed with internal heat generation. The main objective is to develop correlations for the heat transfer between the bed and coolant as well as the pressure drop in the system using detailed experimental and 3-dimensional pore-scale numerical simulation. The system

ABSTRACT Double emulsions have been intensively used as a template to form core/shell structured microcapsules encapsulating and releasing a substance of interest in a controllable way for wide spectrum of chemical and biological applications. Herein a numerical model was established to investigate the thermal effect on breakup dynamics of a double emulsion flowing through a microchannel with a constricted

ABSTRACT In this paper, experimental and numerical study has been carried out to investigate impingement cooling with a row of five circular jets, varied between target positions on a realistic leading edge region of gas turbine blade geometry. Experimental data is collected from a transient thermochromic liquid crystal measurement technique at the target surface. Numerical study was conducted with

ABSTRACT The realization of a high heat flux removal with a flat loop heat pipe at ambient temperature is of great importance for achieving thermal control within spacecraft electronic equipment. In this article, a flat bifacial evaporator loop heat pipe with two flat thermo-contact surfaces has been proposed, fabricated, and investigated. The shell of the flat evaporator was made of stainless steel

Selected Papers from the 16th UK Heat Transfer Conference (UKHTC2019). Heat Transfer Engineering. Accepted .

ABSTRACT Pool boiling can be mentioned as one of the most effective processes of heat transfer regarding the resultant phase change. In this research study, heat transfer in nucleate pool boiling is modeled experimentally with the consideration of surface modification methods utilizing surface photolithography in saturated water at atmospheric pressure. Further, the effects of etching material, confined

Abstract Combination of transient computational fluid dynamics simulations of a gas-fired heat treatment furnace and experimental validation were carried out to investigate the applicability of equilibrium non-premix combustion model and the effect of different turbulence models on the thermal interactions inside the furnace. Thermal interactions analyses based on temperature measurements on an instrumented

Abstract The gas turbines are highly demanded in modern industries, and the improvement of the performance derives from the increase of the turbine inlet temperature. Various cooling structures are used, such as ribs, pin fins, to improve heat transfer performance and extend the lifespan of the blade. Due to the limitations of the measurement technique, magnified geometry models have been tested with

ABSTRACT Appropriate arrangement of the fin structures in the evaporator and condenser not only enhances the heat transfer coefficient but also suppresses the increase of the pressure drop. Due to this reason, a new method of using large-scale pin fins is explored to increase the heat transfer area and to modify the liquid film flow characteristics in the enhanced tubes. In the present study, four

ABSTRACT This study investigates the thermal and hydrodynamic effects of incorporating nanomaterials to the continuous and gas-liquid Taylor flows in mini scale tubes. Aluminum Oxide nanopowder was dispersed in distilled water to produce three nanofluid concentrations: 1, 2 and 4 wt% using a two-step method. Heat transfer enhancement in miniscale tubes ( ∼1.5 mm) was assessed using Nusselt number and

Abstract In this study, the free convection with volumetric radiation in a water–alumina nanofluid flowing between two inclined concentric cylinders was simulated. The enclosure, or the cavity between the two circular quadrants in which the inner and outer pipes were respectively at high and low temperatures, was exposed to a magnetic field, and the remaining walls were insulated. Simulations were

ABSTRACT Straight vegetable oils have a huge potential to minimize the dependence of the automobile and energy sectors on conventional fossil fuels. In the present study, the impact of a single drop of Jatropha straight vegetable oil on a stainless steel surface is investigated for various surface temperatures. The effects of the impact velocity and the surface temperature on both spreading and receding

ABSTRACT Pool boiling is cost-effective, simple and prevalent amongst all available cooling schemes. The lack of quantitative data, qualitative theories and explanations in the area of critical heat flux (CHF) in mini tubes makes it an interesting domain of research. This paper discusses the effect of heater length, diameter, orientation and subcooling on CHF. There is the scarcity of literature that

Abstract This study carried out a three-dimensional, unsteady, numerical simulation to investigate the effects of the cylinder radius, Reynolds number, three-dimensionality and unsteadiness on the mixed convection in a rectangular enclosure containing a cold circular cylinder. The variations in the cylinder radius in the range of 0.1 to 0.3 times the length of the enclosure and the Reynolds number

Abstract The thermal design of natural convection heat sinks is critical to the heat management of electronic devices. In this paper, topology optimization (TO) with a new parameter advancing scheme is employed to study the effect of the heating power, heat source size, allowed volume and material thermal conductivity on the optimized design of natural convection heat sinks. Except for the heating

Abstract This paper numerically investigates the heat transfer characteristics of supersonic high-temperature combustion-gas jet impinging to a perpendicular flat plate. First, the numerical method is validated using an experimental case and meanwhile different turbulence models are evaluated for heat transfer prediction. Then, the effects of multi-species, nozzle-to-plate distance and nozzle pressure

Abstract Room cooling is traditionally used for postharvest products and is always involved with heterogeneous airflow and heat transfer. Despite the current evaluation of such heterogeneity, the irreversibility parameters are still not considered to evaluate the corresponding characteristics. Furthermore, the relationships between the irreversibility and the heterogeneous airflow and heat transfer

Abstract A series of large-scale parallel simulations of flat-plate film cooling are performed to uncover the qualitative and quantitative relationship between coherent structure dynamics and heat-transfer features. The near-wall flow dynamics and heat-transfer features at five inclination angles of 15∘, 30∘, 45∘, 60∘ and 90∘ are also analyzed in detail. Hybrid thermal lattice Boltzmann method and

Abstract This work numerically presents the study of flow and heat transfer in a rectangular channel partially filled with porous media at the pore scale using lattice Boltzmann method. Quartet structure generation set is adopted to generate the structure of porous media. The effects of the relative height, porosity and specific surface area of porous media on the fluid flow and the Nusselt number

Abstract In this paper, the flying heat transfer characteristics of slag particles are studied in the process of the dry centrifugal granulation. When the solidification time of particle surface decreased by 66.67% at the rotational speed of 800 rpm, the total solidification time on the particle surface decreased by 55.5% and the average cooling rate increases faster in the phase transition region;

Abstract In a fluidized bed evaporator, heat transfer between walls of heated tubes and solutions belong to a vapor-liquid-solid flow boiling, and solid particles are fluidized by a vapor-liquid flow. In this evaporator, evaporation can operate continuously without fouling on tube walls even for the solutions of high viscosity and density, like extract liquids of traditional Chinese medicines. In this

ABSTRACT Printed circuit heat exchanger has been recognized as a perspective mini-channel heat exchanger. Semi-circular cross-section is designed here due to the special manufacture technology. However, there is a lack of related investigations on condensation process in mini-channels with semi-circular cross-section. In this paper, corresponding three-dimensional numerical simulations are presented

ABSTRACT The solar water heating system (SWHS) is one of the main ways to utilize solar energy. In this study, the design, transient performance and techno-economic analysis of a hotel SWHS in Shanghai are carried out. Three distribution strategies are considered for the SWHS, which are small-scale distributed system (System I), medium-scale system (System II) and large-scale centralized system (System

ABSTRACT The current work focuses on wall temperature (300 − 1200 K), dimensionless spin rate (0 − 0.315) and angles of attack (0 − 10°) on Magnus effects for the 7-caliber Army-Navy Spinner Rocket (ANSR) using Reynolds-averaged Navier-Stokes methods. The Mach number and the Reynolds number, in terms of the free-stream velocity and the ANSR diameter, are 1.8 and 8.37 × 105. Different turbulence models

ABSTRACT In this paper, numerical investigation on the flow field structure of a hollow cone spray injected transversely into a confined crossflow is presented. The unsteady turbulent flow is predicted by adopting the Scale-Adaptive Simulation approach and the atomization of the spray is predicted by using the linear instability analysis and Taylor analogy breakup theory. The interactions between the

ABSTRACT Experiments of flow regime visualization and identification of air-water two-phase flow were conducted in a horizontal helically coiled rectangular channel. The test superficial liquid and gas velocities are 0.09 − 2 m/s and 0.18 − 16 m/s, respectively. Flow regimes were observed with a high-speed video camera and the corresponding local and average void fractions were measured with an electric

ABSTRACT In this paper, in order to provide guidance on the design and operation of waste heat recovery heat exchangers for the dryer exhaust of lignite pre-drying, pressure drop and heat transfer characteristics of wet air with ash particles across circular finned tube bundles were experimentally studied under different conditions. The experimental water vapor mass fraction ranged from 5% to 15%,

ABSTRACT This paper describes an evaluation method for the liquid separation structure that is utilized in thermal probe for measuring gas temperature in gas-droplet two-phase flows. The study is performed on two structures. Numerical simulations are conducted to find the proper position of the thermocouple detector in the structures. Based on that, a visualization device equipped with high-sensitivity

ABSTRACT This study analyzed the acoustic energy transfer process in expanded pipe of heat exchangers based on the field synergy principle. The synergy between the flow field and the acoustic field was deduced theoretically based on the energy and momentum equations pertaining to the acoustic field. The synergy angle of the flow field and the acoustic field were calculated numerically. The noise propagation

ABSTRACT This paper presents critical analysis of process modeling and mechanisms of CO2 evaporation inside macro- and micro-channels. First, some existing experimental results of CO2 evaporation heat transfer in macro-channels and micro-channels are compared and discussed. Then, the comprehensive two-phase flow pattern map of Cheng et al. for CO2 evaporation inside channels is presented. The flow

Selected Papers from the 1st International Symposium on Thermal-Fluid Dynamics (ISTFD2019). Heat Transfer Engineering. Accepted .

ABSTRACT In this study, the heat transfer by forced convection over a circular cylinder was studied numerically in the presence of an electric field and the effects of the installation angle of discharge electrode, wire - cylinder spacing and electrohydrodynamic (EHD) number were also investigated. The results showed that the location of discharge electrodes has a considerable effect on changing the

ABSTRACT The effect of the entrance geometry conditions on the local and averaged heat transfer coefficient in a rectangular channel with 45° angled ribs has been investigated. Ribs were deployed on one side only, the remaining walls of the channel being assumed smooth and unheated. The influence of entrance conditions was addressed by considering either a long ribbed unheated section or a smooth channel

ABSTRACT In the present study, the boiling flow of R1234yf refrigerant in a horizontal helically coiled tube is investigated to experimentally measure the heat transfer coefficient and pressure drop. A well-instrumented apparatus consisting of the test evaporator and other necessary equipment is used in this investigation. A preheater and a post-evaporator are used to achieve the required vapor qualities

ABSTRACT Al2O3–water nanofluids along with stationary and rotating twisted tape inserts are used to increase the rate of heat transfer in a plain tube. The simulations are conducted through varying the design parameters including angular velocity of twisted tape, Reynolds number and nanofluid volume concentration. It is found that inserting a twisted tape inside a tube substantially increases the heat

ABSTRACT A significant part of boiling heat transfer enhancement methods is surface modification and the creation of structures, both regular and irregular multiscale. In this paper, beam technologies for surface modification are presented. Using these technologies, samples are obtained for experimental studies. Experimental data on heat transfer and critical heat flux during R-113 pool boiling on

Abstract In this study, the effect of axial heat conduction on thermal performance in a zigzag channel printed circuit heat exchanger (PCHE) with supercritical liquefied natural gas as the working fluid is studied by a numerical method under different conditions. The influence factors include Reynolds number, operating pressure, inlet temperatures of the cold side, and wall thermal conductivity. The

Abstract While most critical heat flux (CHF) studies focus on relatively straightforward geometries, actual equipment applications are complex. This paper summarizes literature which provides insights into the effects of selected inlet conditions on CHF and the occurrence of upstream CHF. Vertical smooth bore tube CHF tests found that the concept of “local conditions hypothesis”, though not universally

Abstract Current film-cooling hole-geometry research is attempting to clarify the mechanism of film cooling effectiveness and its relation to the counter-rotating vortex pair (CRVP), in this paper a mechanism of film cooling heat transfer has been proposed. The coolant expansion in this mechanism is likely to improve film cooling effectiveness. It was characterized by developing a high aspect ratio

ABSTRACT In this study, the impingement of a concave surface by hot water jets is investigated. The jets are subjected to a cross airflow at ambient temperature in order to study the effects of the interactions between both fluids on the jet dynamics and the heat flux at jet stagnation area. Different parameters such as the jet diameter, separation distance between two adjacent jets, Reynolds numbers

Abstract In this work, the heat transfer, subject to the effect of viscous dissipation, in a laminar fully-developed flow of a Herschel-Bulkley fluid between parallel plates was analyzed analytically. Both constant and asymmetric wall heat fluxes are considered. For a power-law index, n, higher than 0.5 the average calorific power generated by viscous effects only depends on the ratio between the fluid

Abstract A new configuration of microchannel heat sink with a superior heat removal capability is proposed. The proposed geometry consists of double-layered wavy channels with porosity inserted on the top layer. A conjugate heat transfer numerical solver is employed to compare thermal and hydrodynamic properties of the proposed configuration with other possible double-layered wavy and rectangular geometries

Abstract This paper experimentally studies a new method to enhance heat transfer in which a soft textile flap flutters and slaps a hot plate surface, due to fluid-structure interaction. The self-sustained periodic slapping of the textile flap against the heat transfer surface disrupts the boundary layers and thus, increases the heat transfer between the air and plate surface. Heat transfer coefficients

Abstract This study investigates the electrical and thermal characteristics of a cylindrical lithium-ion cell with an axisymmetric two-dimensional lumped model. The cell is completely discharged at 0.5, 1 and 1.5 C rates under 0, 20 and 50 °C operating temperatures. Both the open circuit voltage values and the average specific heat value of the cell are measured and used as an input to the model. The

ABSTRACT Ceiling diffusers are one of the most important elements of ventilation and air-conditioning installations. They have a significant impact on the speed and temperature distribution of air. The basic task of these devices is to provide the required air stream while maintaining its appropriate parameters in the occupied zone and low noise levels in the room. Square ceiling diffusers are designed

ABSTRACT In the present work, three-dimensional numerical investigations are carried out to study the influence of top wall confinement on unsteady flow and heat transfer characteristics of sinusoidal wavy channels. Different channel confinements considered in the present study are channels having sinusoidal bottom wall and plane, in-phase, and out-of-phase configurations of the top wall. Computations

ABSTRACT The insertion of a broken twisted tape (BTT) in tube is a novel passive heat transfer augmentation method, which constitutes the subject of the present investigation. Effect of BTT on heat transfer performance in novel triangular axial corrugated tubes is investigated experimentally and numerically. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered