Liquid Heat Research Articles

Experimental Investigation of Thermophysical Properties and Combustion Characteristics of Thickened Jet Fuel

ABSTRACT The thermophysical properties and combustion characteristics of PIB thickened jet fuel are investigated based upon both aims of expanding basic combustion theory (i.e., the coupled gas phase and liquid phase flows and heat transfer involving flame spread over liquid fuel) and potential practical applications (i.e., the oil additive in two-stroke gasoline engine and in-situ burning of leaked oils). The effects of PIB on the thermophysical parameters of jet fuel including density, flashpoint, viscosity and surface tension are experimentally measured. The logarithm of the dynamic viscosity varies linearly with the proportion of PIB, which is in good agreement with predictions. Then, the impact of PIB on fire safety of jet fuel is examined through flame spread and ignition experiments. The temperature evolution, flame spread rate, length and velocity of subsurface flow are quantitated and analyzed. The addition of PIB into jet fuel reduces the flame spread rate, but promotes the ignitability. The viscosity augment plays the principal role in hindering flame spreading over thickened jet fuel.

Carbon Dioxide Absorption Heat in Liquid–Liquid and Solid–Liquid Phase-Change Solvents Using Continuous Calorimetry

For three groups of systems—homogeneous, liquid–liquid, and solid–liquid—absorption heats of carbon dioxide capture by amine solutions were determined with continuous calorimetry. In the case of a ...

Numerical modeling of vapor condensation over a wide range of non-condensable gas concentrations

This paper presents a numerical model to study the process of vapor condensation on surfaces characterized by film-wise condensation with the presence of Non-condensable gases (NCG). State variables in both the condensate film and the diffusion layer were solved separately and the condensation interface was used to couple the two solutions. The solution of the condensate film was obtained using well-established solutions of laminar film condensation of pure vapor. In contrast to other models surveyed, this work provides a inexpensive and accurate predictions of heat and mass transfer characteristics. We validated the work against two classical condensation problems. The model was first validated against empirical correlations and experimental work, resulting in a very good agreement. We then assessed the applicability of ignoring the condensate film effect, as performed in previous models, on the condensation processes by observing the thermal resistances of both the condensate film and diffusion layer. Results indicated that for the studied cases of NCG mass fractions above 20%, the condensate thermal resistance was at least an order of magnitude lower than that of the diffusion layer. However, the two thermal resistances seem to approach each other as NCG mass fraction becomes smaller. On another front, we observed that models that ignore the condensate film thermal resistance underestimate the interfacial temperature albeit accurately predicting the overall heat transfer rate. To simulate even lower NCG mass fractions, we validated our model to the classical analytical work of Sparrow and co-workers. Results showed a striking agreement between the two solutions at different NCG mass fractions (0.5%–10%) and subcooling degrees (5∘F–40∘F). Finally, we found a good agreement between results of our model and the heat/mass transfer analogy. The heat/mass transfer analogy is a semi-empirical method therefore, is limited to the existing correlations and their uncertainties. On the other hand, our model does not use any empiricism and relies on the available solutions of laminar condensate film of pure vapor in predicting the liquid side heat transfer coefficient.

Double-layer packed bed used for heating non-polar liquid under microwave irradiation

There are some reports showing that microwave heating has a positive effect on the non-polar reaction liquid with polar solute. For the continuous-flow microwave heating of non-polar reaction liquid, the methods such as the addition of a high-loss dielectric material are generally used, but there is a problem that the temperature of the fluid will continue to rise, which cannot be maintained within a stable range. In this paper, a novel double-layer packed bed is designed in order to solve the above problem. The double-layer packed bed is divided into a heating layer and a thermostatic layer: the packing of heating layer is composed of the high-loss dielectric material; the packing of thermostatic layer is composed of a mixture of the high-loss and low-loss dielectric material in a certain proportion. Both the experimental and simulation results verified that the non-polar liquid temperature can rapidly rise to the preheating temperature in the heating layer and remain stable in the thermostatic layer while passing through the double-layer packed bed under microwave irradiation. The practicality of the double-layer packed bed was exemplified in the continuous synthesis of geranyl butyrate that proceeded more rapidly under microwave irradiation than conventional heating.

Investigation of heat transfer coefficients in a liquid–liquid direct contact latent heat storage system

The study presents a latent heat storage system consisting of a phase change material (PCM) and a heat transfer fluid (HTF), placed in direct contact, for storing thermal energy derived from renewable energy sources or industrial waste heat. It is important that the two media are immiscible for the function of such a storage system. In this study the PCM was an eutectic mixture of the two salt hydrates, magnesium nitrate hexahydrate and magnesium chloride hexahydrate and the HTF was a mineral oil. The direct contact leads to intensified heat transfer compared to that in the indirect contact heat storage systems. This intensified heat transfer results in short loading and unloading periods of the storage tank with a high heat exchange performance. Furthermore, a higher storage density is observed in comparison to the sensible storage systems, particularly when combined with low temperature differences between the charged and discharged storage systems. In our study, the heat transfer between liquid PCM and liquid HTF (rises drop-shaped in the PCM) is investigated. For this purpose, a storage tank has been built with only one HTF inlet opening in the bottom. For the time and space resolved data, the axial temperature profile, and the surface temperature of the rising droplet, as well as the PCM temperature, are measured with a specially developed, fast, near infrared sensitive, and fiber-coupled technique. These measurements made it possible to determine a local heat transfer coefficient between the PCM and HTF. With the chosen parameters and materials in this study a heat transfer coefficient of 1845 W/m² K was calculated.

Liquid Heat Capacity Measurements of the Linear Dicarboxylic Acid Family via Modulated Differential Scanning Calorimetry

This paper reports liquid heat capacity data on members of the linear saturated dicarboxylic acid family and one dicarboxylic acid derivative measured using modulated differential scanning calorime...

Experimental Characterization of a Compact Milli-Channel Heat Exchanger for Liquid–Liquid Heat Transfer

The use of Milli-Channel Heat Exchangers (MCHE) presents numerous assets: efficient heat transfer, huge compactness, and limited pressure drop. For an engineer, the Fanning friction factor and the convective heat transfer coefficient are two main parameters to describe the performance of a heat exchanger. A brazed MCHE with rectangular channels in stainless steel made by the Institut für Mikrotechnik Mainz (IMM, Mainz, Germany) has been characterized experimentally and theoretically in a counter-current configuration. The selected working fluids are deionized water and oil without any phase change during experiments. The pilot unit ensures measurements of pressure drops, temperatures, and volumetric flow rate of each fluid flowing in laminar regime. A one-dimensional model has been developed. The temperature and pressure profiles of each fluid are represented by differential equations associated with boundary conditions. The system of coupled equations consists in a two-point boundary value problem solved numerically by the Matlab software. The parameters of a Nusselt number correlation are identified together with those of a Fanning friction factor one by minimizing a sum of squared differences between experimental and predicted data. The calculated temperature and pressure profiles present a good agreement with measurements. A statistical analysis shows that each optimized parameter is significant.

Study of transport phenomenon in Carreau fluid using Cattaneo–Christov heat flux model with temperature dependent diffusion coefficients

This article uses non-Fourier theory to investigate the transport phenomenon in Carreau liquid of temperature dependent diffusion coefficients. The governing problems are solved by finite element method (FEM) and simulated results for different values of Prandtl and Schmidt numbers, viscosity parameter, local Wiessenberg number, chemical reaction parameter, heat generation/absorption parameter and thermal and concentration relaxation parameters are displayed graphically. The relaxation parameters have a tendency to decrease the temperature and concentration field for both cases of variable and constant dynamic viscosity. Thermal relaxation time has significant decreasing behavior on the temperature. Thermal boundary layer relaxation time has significant decreasing behavior on the temperature. Thermal boundary layer thickness in the Carreau liquid obeying classical Fourier’s law is greater than that in the Carreau liquid obeying Cattaneo–Christov heat flux model further, the thermal boundary layer thickness associated with Carreau liquid of variable viscosity is greater or smaller than the thermal boundary layer thickness associated with Carreau liquid of constant viscosity. More heat transfer in liquids obeying classical Fourier’s laws of conduction is possible rather than transfer of heat in liquids obeying Cattaneo–Christov flux model. Thermo-elasticity in fluid flow has shown a decreasing trend in the transport of heat and mass.

A PROTOTYPE DEVICE FOR PRODUCING FRESH WATER FROM ATMOSPHERIC AIR

Objectives.The aim of the article is to develop the design and carry out the physical and mathematical modelling of a device for producing fresh water from atmospheric air in coastal areas, as well as under the conditions of sea transport.A Method for constructing the device for producing fresh water from atmospheric air is developed on the basis of a physical and mathematical model. Fresh water is obtained by condensation on a cold surface, which dew point is created using the natural cold of seawater with the application of the energy of moving waves for its circulation. The heating of the surface air layer adjacent to the cold surface by solar concentrators intensifies the process of the moisture condensation.Results. Data is obtained on the quantity (mass) of fresh water produced per unit of condensation surface area (1 m2 ) for 1 hour depending on the temperature difference between the condensation surface and seawater. The influence of the characteristics of solar concentrator and liquid heat remover with seawater on the device parameters is studied.Conclusion. It is established that the amount of the fresh water obtained from atmospheric air strongly depends on the temperature difference between the condensation surface and seawater. Thus, according to calculations, with an increase of the latter by 45 K, the mass of fresh water obtained from a condensation surface of 1 m2 in 1 hour approximately doubles to 5.8 kg.

Liquid Heating During the Collapse of a Single Cavitation Bubble

This paper presents the results of a numerical study of the liquid heating process during collapse of a single spherical cavitation bubble in water at a liquid pressure of 10 bar, temperature of 20°C, and an initial bubble radius of 500 μm. The simulation of this phenomenon took into account the thermal conductivity of the vapor in the bubble and the surrounding liquid, heat transfer and evaporation/condensation on the surface of the bubble, and the effects of viscosity and compressibility of the liquid. It is shown that, as a result of bubble collapse, the liquid heats up in a region of about 60 μm radius. The temperature in the center of this region is about 50°C higher than in the surrounding liquid. The thermal energy expended on heating the liquid in this region is approximately equal to 25 μJ.

Modelling evaporation processes of cement-bentonite mixtures

Upon drying, matter and energy are exchanged between the atmosphere and porous media through evaporation, which is a coupled process that involves the simultaneous transport of liquid water, water vapour and heat. At shallow depths, evaporation controls the water content and suction of both natural soils and earthworks, affecting their hydraulic response. This impact is particularly relevant when the earthworks are aimed at the containment of aqueous or non-aqueous pollutants, as in the case of cement bentonite cut-off walls. A coupled model for the transport of liquid water, water vapour and heat through cement bentonite mixtures upon evaporation was formulated. The model considers flow of water driven by both total suction and temperature gradients. Model predictions were compared to experimental results obtained in the laboratory on samples having different sizes and imposed boundary conditions. A good agreement between predicted and measured volumetric water contents was obtained, once defined a suitable dependency of the relative permeability of the mixture on degree of saturation. The results suggest that the proposed formulation correctly accounts for the underlying physical processes, and that it might be used to model the real scale behaviour of cut-off walls.

Теплові характеристики рідинного теплообмінника прий¬маль¬но-передавального модуля АФАР

The paper presents the results on numerical simulation of the temperature field of a cold plate type liquid heat exchanger for a multichannel transmitter/receiver module. Each side of the cold plate carries 8 local microwave fuel elements with a heat dissipation capacity of 11 W each and one block with low-power electronic elements (total power of all elements — 50 W), installed symmetrically on both sides. The total heat dissipation capacity is 276 W. The cold plate is cooled by pumping a liquid heat carrier (Antifreeze A 65) through a curved cooling channel of rectangular cross-section made inside the liquid heat exchanger. The study was conducted at a working fluid flow rate of 2, 4, 6, 8 and 10 l/min. Numerical simulation allowed obtaining the temperature distribution of the mounting surfaces of the cold plate and determining the values of the working fluid flow rate, which provide effective cooling of the mounting surfaces. It is shown that at a flow rate of 4 l/min, the temperature values at the installation sites of local microwave elements do not exceed 64°C. The total thermal resistance of the cooling system based on a liquid heat exchanger is from 0.063 to 0.028°C/W with a flow rate from 2 to 10 l/min, respectively.

TWO PHASE SPHERICAL STEFAN INVERSE PROBLEM SOLUTION WITH LINEAR COMBINATION OF RADIAL HEAT POLYNOMIALS AND INTEGRAL ERROR FUNCTIONS IN ELECTRICAL CONTACT PROCESS

Abstract. In this research the inverse Stefan problem in spherical model where heat flux has to be determined is considered. This work is continuing of our research in electrical engineering that when heat flux passes through one material to the another material at the point where they contact heat distribution process takes the place. At free boundary α (t) contact spot starts to boiling and at β (t) stars to melting and there appear two phase: liquid phase and solid phase. Our aim to calculate temperature in liquid and solid phase, then find heat flux entering into contact spot. The exact solution of problem represented in linear combination of series for radial heat polynomials and integral error functions. The recurrent formulas for determine unknown coefficients are represented. The effectiveness of method is checked by test problem and approximate problem in which exact solution and approximate solution of heat flux is compared. The coefficients of heat at liquid and solid phases and heat flux are found. The heat flux equation is checked by testing problem by using Mathcad program.Key words: Stefan problem, radial heat polynomials, Faa-di Bruno, collocation method.

Efficient use of microwave EMF and multilevel high temperature sterilization modes in apple puree technology for dietetic nutrition

The article is dedicated to improving the quality of apple puree with xylitol for dietetic nutrition due to the development and implementation of a new technological process. This is microwave boiling of apples, rather than traditional steaming using saturated steam before chopping, with the development of a device for its implementation and multilevel high-temperature sterilization modes with prebake of apple puree in glass jars in microwave EMF. The analysis of research and technical data proved that pre-heat treatment of apples with saturated steam and traditional sterilization modes have a considerable duration, which impairs the finished products quality and has an adverse effect on the nutrient composition of the raw material during processing. Substituting the traditional method of pre-heat treatment of apples for their short-time processing in microwave EMF reduces the process by more than twice, which, in turn, contributes to an increased preservation of the nutrient composition of apples, while enhancing the yield of apple puree. For the implementation of microwave processing method of raw materials, a new design of the device for electromagnetic treatment of plant roughage has been developed, providing a uniform and more intensive heat treatment of raw materials in a continuous flow. Rapid multilevel high-temperature sterilization modes with the application of apple puree in glass jars in microwave EMF, liquid high-temperature heat devices and an autoclave basket, providing the opportunity for thermal sterilization of the product without creating reverse pressure in the machine, generally contribute to reducing heat costs and increasing the nutritional value.

Polar soft-SAFT: theory and comparison with molecular simulations and experimental data of pure polar fluids.

The consideration of polar interactions is of vital importance for the development of predictive and accurate thermodynamic models for polar fluids, as they govern most of their thermodynamic properties, making them highly non-ideal fluids. We present here for the first time the extension of the soft-SAFT equation of state (EoS), named polar soft-SAFT, to explicitly model intermolecular polar interactions (dipolar and quadrupolar), using the approach of Jog and Chapman (P. K. Jog and W. G. Chapman, Mol. Phys., 1999, 97(3), 307-319). The theory is first validated using molecular simulation data for a wide range of polar model systems including Stockmayer fluids, LJ dimers with dipole, and quadrupolar LJ fluids, for a wide range of thermophysical properties such as liquid density, vapour pressure, surface tension and heat capacities. Excellent agreement between polar soft-SAFT and simulation data has been obtained for all examined fluids and properties for systems exhibiting low to intermediate polar strength, while the agreement deteriorates at very high polar strengths. Once validated with simulations, the equation has been applied to calculate vapour-liquid equilibria (VLE), surface tension and second-order derivative properties of systems such as 2-ketone and methane chloride families as showcases for dipolar fluids and the benzene family for quadrupolar fluids, finding very good agreement with experimental data. In order to preserve the robustness of the model, the experimental value of the dipole or quadrupole was used in these calculations, while the additional parameter for the polar fluids was set a priori rather than included in the fitting procedure. The excellent agreement found with simulations and experiments empowers the soft-SAFT equation with new capabilities for the development of robust and accurate molecular models of polar fluids of industrial relevance.

SESAME project: advancements in liquid metal thermal hydraulics experiments and simulations

Liquid metal cooled reactors are envisaged to play an important role in the future of nuclear energy production because of their possibility to use natural resources efficiently and to reduce the volume and lifetime of nuclear waste. Sodium and Liquid lead (-alloys) are considered the short and long term solution respectively, as coolant in GEN-IV reactor. Thermal-hydraulics of liquid metals plays a key role in the design and safety assessments of these reactors. Therefore, this is the main topic of a large European collaborative program (the Horizon 2020 SESAME) sponsored by the European Commission. This paper will present the progress in the project with respect to liquid metal cooled reactor thermal-hydraulics (liquid metal heat transfer, fuel assembly thermal-hydraulics, pool thermal-hydraulics, and system thermal-hydraulics). New reference data, both experimental and high-fidelity numerical data is being generated. And finally, when considering the system scale, the purpose is to validate and improve system thermal-hydraulics models and codes, but also to further develop and validate multi-scale approaches under development.

Assessment of energy efficiency of application heat-insulating paint for the needs of district heat supply systems

Energy conservation is a priority for most of the nation states. Its relevance in modern world energy industry is growing every year. This problem acquires particular importance when a country is characterized by a lack of fuel and energy resources or adverse climatic conditions. The most effective way to reduce heat losses from heat network pipelines to environment is the use of heat insulation. This paper presents the results of application heat-insulating paint on the surface of main pipeline. The infrared thermometry devices (pyrometer and thermal imager) were used to evaluate the energy efficiency of modern high-tech insulation. The thermograms from thermal imager and the readings from pyrometer were analyzed, it was established that the absolute difference in temperatures of an isolated pipeline section and an unpainted section are 5-10 °C. The studies have also shown that when a 250×6 pipeline is coated with a 1 mm thick heat-insulating paint, it will save 126.1 m3 of natural gas per 1 running meter per year. In monetary terms it will be approximately 610 rubles or about $9 (for the first half of 2020). The payback period of this energy-saving measure should not exceed six months. Increasing the thickness of liquid heat insulation layer is not economically feasible. The equivalent fuel economy is approximately 65% when the heat-insulating paint is of 1 mm thickness, and it will increase by only 8% for a thickness of 1.5 mm.

Research on thermal equilibrium performance of liquid-cooled lithium-ion power battery system at low temperature

The development of electric vehicles is an important trend in the automotive industry, in which the performance of power batteries is greatly affected by temperature. In recent years, it has been widely concerned that the performance of power batteries at low temperature will lead to the vehicle failure to start because of the bad thermal equilibrium of power battery heating system. This paper studies the thermal equilibrium performance of battery liquid heating system at low temperature. Inlet temperature, heating time, ambient temperature, and their coupling relationship to battery thermal equilibrium performance are studied by orthogonal experimental design method. It is expected that this study can provide reference for the parameter selection of battery heating system.

Application of thermoelectric cooler in temperature control system of space science experiment

As an important mission of space stations and scientific satellites, space science experiment usually requires effective temperature control measures. Integrating heating and cooling capacities, thermoelectric cooler (TEC) is competent for this job attributed to the low complexity and high reliability. In this paper, two TEC systems are introduced, including direct temperature control system (DTCS) and environment temperature control system (ETCS). DTCS directly deals with the temperature control of the target element surface. The effects of the current and the heat sink (i.e. working liquid) temperature are analyzed under heating and cooling conditions respectively. ETCS deals with the temperature control of the entire environment surrounding the element. The element is indirectly heated or cooled by the ambient air. Depending on whether an additional intermediate air-to-liquid heat exchanger is consisted or not, ETCS can be further classified as TEC-HX system and TEC-alone system. The heat exchanger may improve the system performances. The effects of the liquid flow rate and heat exchanger efficiency on system performances are analyzed, providing guides for the design of the practical system.

Thermophysical Properties of Advanced Ni‐Based Superalloys in the Liquid State Measured on Board the International Space Station

Advanced nickel‐based superalloys combine excellent high‐temperature mechanical strength, creep resistance, and toughness, and therefore find applications in next‐generation aircraft engines and turbines for land‐based power generators. The related fabrication processes are complex, time consuming, and costly, making it necessary to perform supporting computer simulations of the heat and material flow in the melt before and during crystallization. Such models are based on reliable thermophysical property data in the solid and liquid phase. However, measurements of surface‐ and volume‐dependent properties, such as liquid surface tension, viscosity, and specific heat of these complex liquid metal alloys, are very challenging, due to the melts high chemical reactivity at temperatures of interest. The method of choice is electromagnetic levitation, a containerless method. The measurements of surface tension, viscosity, mass density, and specific heat capacity, performed in the electromagnetic levitator (EML) on board the Space Laboratory Columbus in the International Space Station (ISS), are presented and discussed.