Latent Heat Of Vaporization Research Articles

Wet surface wall model for latent heat exchange during evaporation.

Air conditioning is a dual heat and mass transfer process, and the human nasal cavity achieves this through the mucosal wall surface, which is supplied with an energy source through the sub‐epithelial network of capillaries. Computational studies of air conditioning in the nasal cavity have included temperature and humidity, but most studies solved these flow parameters separately, and in some cases, a constant mucosal surface temperature was used. Recent developments demonstrated that both heat and mass transfer need to be modeled. This work expands on existing modeling efforts in accounting for the nasal cavity's dual heat and mass transfer process by introducing a new subwall model, given in the Supplementary Materials. The model was applied to a pipe geometry, and a human nasal cavity was recreated from CT‐scans, and six inhalation conditions were studied. The results showed that when the energy transfer from the latent heat of evaporation is included, there is a cooling effect on the mucosal surface temperature.

A floating planting system based on concentrated solar multi-stage rising film distillation process

This work presents a floating planting system based on multi-stage rising film distillation process driven by concentrated solar energy. The proposed system applies desalinated freshwater to directly irrigate hydroponic crops, which saves land area and takes advantage of ocean resources. The hydrophilic wick is selected as the evaporator to form a rising seawater film by capillary suction. Through the vertically arranged multi-stage evaporation and condensation units, the latent heat of vapor can be recovered effectively. To obtain the maximum optical efficiency, the optical simulation of the concentrating section is carried out. Based on optimized structure, an experimental system is built to investigate the effects of different operating parameters on the internal temperature, water production rate, gained output ratio (GOR), and exergy efficiency. Under indoor steady-state conditions, the temperature difference of desalination units is found to be progressively larger under increasing irradiance. In addition, the system could achieve 1.7 of GOR and 6.1% of exergy efficiency with 900 W/m2 irradiance. Results at actual weather reveal that the daily water yield of the system could reach 9.51 kg/m2/day under azimuth tracking condition, which is 97% higher than the fully passive operation condition. Finally, under 28 consecutive days of operation, the average growth height of lettuces cultivated by the system is 13.7 cm.

REVIEW on FRAUD DETECTION in CREDIT CARD TRANSACTIONS USING MACHINE LEARNING TECHNIQUES

HVAC stands for Heating, Ventilation and Air conditioning is the technology of automotive and inside environmental comfort. HVAC system design is based on thermodynamics, heat transfer and fluid mechanics. A cooling tower is a specialized heat exchanger in which air and water are brought into direct contact with each other to reduce the water's temperature. It operates on the principle of removing heat from water by evaporating a small portion of water that is recalculated through the unit. The mixing of warm water and cooler air releases latent heat of vaporization, causing the water to cool. Cooling tower piping systems have evolved over the years from simplistic, dedicated hydraulic loops that lacked complexity to large-volume, multiplexed systems that offer peak operational efficiencies. The evolution of a more sophisticated system is due in part to the advent of advanced controls and the operational flexibility of modern chillers, cooling towers. Cooling tower piping systems are designed to be streamlined to keep capital costs low while yielding the most energy-efficient solution. The effects on the performances of cooling tower are determined by following parameters: (1) flow rate of water (2) diameter of pipe

Numerical investigation on shock waves generated by flashing water jet

Numerical study has been conducted to investigate shock waves generated by flashing water jet. This study presents results of a numerical simulation of flash evaporation phenomena occurring when a jet of superheated water is injected through a nozzle into low-pressure water vapor. Due to the sudden pressure drop, flashing takes place, and the sensible heat of the water converts into latent heat of evaporation. The multiphase flow field in the evaporation zone and induced shock waves are explored via a 2D transient investigation in Ansys Fluent. The Mixture model is applied with slip velocities to model the non-homogeneous multiphase flows. Resulting distributions of the fluid properties velocity, Mach number, pressure, liquid volume fraction, density, and in addition to speed of sound inside the flashing chamber at different time steps are presented and discussed. The results show that once the superheated water is injected, it flashes immediately and generates a shock wave. The primary and reflected shock waves are characterized by discontinuous fluid properties in a narrow region across the shock. The generated shock waves are moving shock waves and can be useful to transfer energy directly between fluids without using mechanical components such as pistons or vaned impellers, which can be exploited in industrial and technological applications such as utilizing resulting shock waves in creating useful compression.

Energy-saving and emission reduction system of data center heat pipe based on latent heat of water evaporation

To address the current problem of high energy consumption in data centers, this paper proposes a data center heat pipe air-conditioning system based on the latent heat of water evaporation, which uses the latent heat of water evaporation for cooling by creating a low pressure environment to evaporate large amounts of water. In order to verify the effect of the system, a heat pipe test bench based on the latent heat of water evaporation was designed and built. Compared with the traditional heat pipe in the data center for heat dissipation, the performance and economy of the water evaporation latent heat pipe system designed in this paper are analyzed experimentally. A multi-physics coupled model of water evaporation latent heat pipe air-conditioning based on COMSOL Multiphysics was established to simulate and study the temperature field and velocity field distribution of water evaporation latent heat pipe air-conditioning system in data centers. The research shows that: - Under the designed test conditions, compared with the traditional heat pipe system, the water evaporation latent heat pipe air conditioner can conduct 2540 kJ more heat in one day in an outdoor environment of 24?C. - At an ambient temperature of 35?C and an indoor temperature of 25.8 ?C, the cooling capacity of the heat pipe in the data center water evaporation latent heat pipe air-conditioning system is twice the cooling capacity of the air conditioner, and the heat pipe can work efficiently regardless of the outdoor ambient temperature. - The energy-saving effect of the latent heat pipe of water evaporation in the data center has a significant effect on air conditioners with an energy efficiency rating (EER) lower than 2.5-4.4. It can improve the energy efficiency of level 5 with an EER of 2.5 to level 2 with an EER of 3.22, greatly reducing the power consumption of the data center air-conditioning system. When the EER of the air conditioner exceeds 4.4, the coefficient of performance of the data center water evaporation latent heat pipe air-conditioning system will be lower than that of the air conditioner itself.

Enhanced low-temperature stable combustion of hydrocarbon with suppressing the Leidenfrost effect

Low-temperature stable combustion of liquid hydrocarbons helps improve energy efficiency and alleviate environmental pollution. However, when hydrocarbons (mainly saturated ones) are used as aircraft fuel, they show a long ignition delay time (IDT) and high ignition temperature as a result of Leidenfrost effect and chemical inertness of the CH bond. In especial, the insulated fuel vapor film due to the Leidenfrost effect that inhibits the heat transfer efficiency in the wide Leidenfrost region is unfavorable. Herein, we first propose a strategy that combines low-temperature self-oxidation and enhanced heat conduction to achieve low-temperature stable combustion of hydrocarbon while suppressing the Leidenfrost effect. Specifically, moderately reactive organometallic compound methoxydiethylborane (MDEB) with special radicals and silver nanoparticles (Ag NPs) with high thermal conductivity are preferred as fuel modifiers. By thermodynamic calculation, the heat released by the self-oxidation of MDEB is two orders of magnitude higher than the evaporation latent heat of n-decane, suggesting the applicability of energy conversion supported by enhancing fuel reactivity in suppressing the Leidenfrost effect. Ignition experiment results show that the negative temperature dependence associated with the Leidenfrost effect is eliminated under the specific fuel composition. Encouragingly, compared with n-decane, the IDT of MDEB/Ag/n-decane hybrid fuel is reduced from 4027 to ∼10 ms at a surface temperature of 600 °C. Comparing the ignition of MDEB/Ag/n-decane and MDEB/n-decane hybrid fuels at same temperatures, the influence of Ag NPs on IDT is highlighted by its significant decrease (∼28%). The minimum ignition temperature of n-decane-based hybrid fuel decreases to 112 °C, which is 508 °C lower than that of n-decane. These two ignition characteristic values are the low limit of saturated hydrocarbons to date. Our results thus provide a promising tool for enhancing the low-temperature ignition reliability and combustion stability of liquid hydrocarbons, which potentially decreases the pollution from the low temperature combustion.

Optical diagnostics and chemical kinetic analysis on the dual-fuel combustion of methanol and high reactivity fuels

Dual-fuel combustion is an effective method to utilize methanol because of its high octane number and latent heat of evaporation. Two ways to use methanol are discussed. One is port-injected high reactivity fuel and directed-injected methanol, named as active-thermal atmosphere combustion (ATAC). The other is port-injected methanol and direct-injected high reactivity fuel, which is reactivity-controlled compression ignition (RCCI). In the current work, both methanol combustion modes were investigated in an optical engine. Several optically diagnostic methods were utilized to characterize flame features, including flame natural luminosity imaging, OH* natural luminosity imaging and two-color method by wavelength integration. Meantime, the chemical kinetics simulation was also combined to investigate the effects of active atmosphere and thermal atmosphere on methanol combustion. Results show that as for methanol ATAC, when the methanol is direct-injected during the low temperature heat release (LTHR) stage of n-heptane, it causes significant effects on the combustion phasing of the following high temperature heat release (HTHR). When the methanol is direct-injected during the HTHR stage of n-heptane, the single-peak HTHR turns to the double-peak HTHR. Besides, the yellow diffusion flame of methanol can also be observed. Affected by the in-cylinder vortex, the area and intensity of the OH* signal in the vortex squeeze zone are greater than those in the vortex stretch zone. The flame temperature of methanol maintains in 1800–2500 K at CA50 (the crank angle of 50% mixtures is burned completely), while the maximum KL factor maintains in 0.04–0.05. The thermal atmosphere created by the n-heptane combustion has the dominant effects on shortening the ignition delay of methanol. The effects of active atmosphere are limited. As for methanol/high reactivity fuel RCCI, because of the existence of homogeneous low reactivity methanol, the misfire condition occurs when the direct injection (DI) timing is late. With the DI timing of high reactivity fuel advancing, the combustion stability improves. But the flame development progress is mainly low-speed flame propagation, which results in long combustion duration. The combustion characteristics can be further improved by utilizing higher reactivity fuel, such as n-dodecane, specifically, the combustion phasing advances and the number of auto-ignition spots increases.

Performance, Combustion, and Emission Characteristics of a Common Rail Direct Injection Diesel Engine Fueled by Diesel/n-Amyl Alcohol Blends With Exhaust Gas Recirculation Technique

AbstractBiofuels are considered as one of the best viable and inexhaustible alternatives to conventional diesel fuel. Alcohols have become very important and popular in the present scenario due to their peculiar fuel properties and production nature. This study examines the effect of n-amyl alcohol and exhaust gas recirculation of 10% and 20% on various engine characteristics of common rail direct injection (CRDI) compression ignition engine. The proportion of n-amyl alcohol varies from 5% to 25% in 5% step (by volume). The obtained results show that diesel/n-amyl alcohol blends decrease the mean gas temperature and cylinder pressure, which is 1.88% and 4.25% less at 75% load for n-amyl alcohol (25%) with conventional diesel fuel. The duration of combustion has shown a hike of 4.66 °CA for 25% n-amyl alcohol (at 75% load) compared to conventional diesel fuel. However, the cumulative heat release rate improved by 12.95% higher for 25% n-amyl alcohol at 75% load due to the extended delay in ignition. While n-amyl alcohol was used, the emission of nitrogen oxide emissions decreased considerably. However, the hydrocarbon (HC) (7–9%) and carbon monoxide (CO) (6–8%) emissions are increased due to inferior fuel properties like high latent heat evaporation of n-amyl alcohol. Compared with other blends, n-amyl alcohol (5%) produced results comparable to conventional diesel fuel, which is 3.6% higher in BSFC, 2.37% higher BTE, and 33.33% higher CO emissions 18.18% more in HC emission, and 17.55% less NOx emission. Without further modification, we can use 25% n-amyl alcohol in the combustion ignition engines. From this evidence, we can summarize that n-amyl alcohol is a biofuel that is both renewable and sustainable, and also it considerably reduces harmful nitrogen oxide emissions. The performance, if needed, can be improved by changing the parameters of the engine.

An experimental study of the fire extinguishing ability of modular fire extinguishing installations if astralene-modified water mist is used

Introduction. The aim of the research project is to study the effect produced by one type of carbon nanostructures, or astralenes, on processes of extinguishing oil product flame using finely sprayed water. Materials and research methods. The research is focused on fire extinguishing suspensions used in modular water mist installations for the fire extinguishing of oil products. Astralene-modified distilled water, having the volumetric concentration of nanostructures equal to 0.05–1.0 percent, was used as a fire extinguishing substance under research. The experiment was focused on the study of thermophysical characteristics of fire extinguishing liquids, such as density, dynamic viscosity, surface tension, specific heat of vaporization. Also, studies were carried out to identify the rate of evaporation, the distribution of droplet sizes of sprayed fire extinguishing compositions, and the time needed to extinguish the model source of ignition of oil products.Research results. The dispersion of nanostructures of fire-extinguishing liquids allows to increase their density, surface tension by 20.6 %, increase the specific heat of vaporization if the volumetric concentration of astralenes is equal to 0.25 and 0.5 %, and boost the dynamic viscosity by 6.68–15.38 % at the temperature of 20 °С. The research was carried out to find the rate of evaporation of droplets of the modified fire-extinguishing liquid. It was found that an increase in the volumetric concentration of nanostructures from 0.05 to 0.5 % causes reduction in the evaporation rate.The droplet speed increases if the volumetric dispersion of astalenes goes up to 0 to 0.25 %. However, a further increase in the volumetric concentration of astralenes to 1.0 % causes a reduction in their speed. The extinguishing time was identified using a laboratory fire extinguishing installation. The distribution of droplet sizes of fire-extinguishing compositions is in the range of 20 to 160 microns. The fire extinguishing capacity of the installation was highest if a fire extinguishing composition had a 0.5 % volumetric concentration of astralenes.Conclusions. The modification of a fire extinguishing composition by carbon nanostructures leads to a change in its thermophysical characteristics. The addition of this composition to the installation, used at facilities involved in the processing of petroleum products, will increase its fire extinguishing ability. Further areas of research may include the development of astralene stabilization methods for suspensions and adaptation to low temperatures.

Analysis of Selection of the Best Refrigerant Using the WASPAS Method

Every nation is working to stop ozone depletion and global warming as climate changes have just become apparent on a global scale. According to the prevailing theory behind ozone depletion, free chlorine radicals first eliminate ozone from the atmosphere before chlorine atoms continue to turn more ozone into oxygen. The migration of substances containing chlorine is what causes chlorine to be present in the stratosphere. This behaviour is common across a wide class of compounds called hydro chloro fluoro carbons (HCFCs) and chlorofluorocarbons (CFCs). The world's consumers and industries employ these substances in a variety of applications, particularly as refrigerants in air conditioning and refrigeration systems. The optimal refrigerant was chosen in this study using the WASPAS approach. In this paper R152a, R1234yf, R1234ze (E), R1233zd (E), R290, R600a, R744 and R1270 are used as an alternative for refrigerants. Vapour density, Latent heat of vaporization, Thermal conductivity of liquid, Critical Pressure and Saturated pressure are used to evaluate the performance of refrigerants. Rank of refrigerants R152a is third-ranked, R1234yf is ranked fifth, R1234ze (E) is ranked first, R1233zd (E) is fourth ranked, R290 is fourth-ranked, R600a is ranked eighth, R744 is second and R1270 is seventh-ranked. The result of the analysis shows that the best refrigerant is R1234ze (E) with a coefficient value of 0.634741 followed by R744 with a coefficient value of 0.517734.

Mixed refrigerant components selection criteria in LNG processes; thermodynamic analysis and prioritization guidelines

The most important operating variables for the optimization of natural gas liquefaction processes are the flow rate of the mixed refrigerant (MR) components and operating pressures. In this paper, for the first time, the thermodynamic principles of selecting MR components were investigated. For this purpose, the single mixed refrigerant process was simulated in thirteen cases with different MR components and optimized with the genetic algorithm to minimize process power consumption. The optimization results indicated that the boiling point temperature (Tb), specific heat capacity (cp), and latent heat of vaporization (λ) were the most essential thermodynamic properties. The lower Tb and cp in the selection of lightweight components among nitrogen, methane, ethane, and ethylene, and higher Tb, cp, and λ in the selection of heavy components among propane, i-butane, and i-pentane caused better performance. The results of the process optimization with MR, including nitrogen, methane, ethane, propane, and i-butane, showed that the process power consumption would be reduced up to 11.28% and 8.91% by replacing ethane with ethylene and i-butane with i-pentane, respectively. In addition, MR components must be selected in such a way that the difference between their Tb is not significant. Therefore, propane and ethylene are a priority for heavy and lightweight components, respectively.

Study on the characteristics of performance, combustion, and emissions for a diesel water emulsion fuel on a combustion visualization engine and a commercial diesel engine

Water-in-oil (W/O) emulsion fuels generate rapid evaporative latent heat owing to the simultaneous vaporization of water particles during the compression (550 °C–700 °C) and combustion processes. Combustion is improved as fuel particulates are emitted during the combustion process. This is due to the reduction in combustion temperature caused by the absorption of this evaporation latent heat and the microexplosions caused by the rapid evaporation of water particulates. This allows the simultaneous reduction of nitrogen oxide and smoke, no requirement of additional devices (unlike pre- and post-treatment technologies), and the use of existing diesel engines without any modification. Therefore, this study applied diesel oil (DO) for automobiles and diesel–water emulsion (DWE) fuel to combustion visualization engines and diesel engines to identify the basic combustion and exhaust characteristics. The results showed that the DWE fuel had a −15.3% reduction in combustion duration compared with DO, which had a −19.6% reduction in nitrogen oxide and a −66.3% reduction in smoke.

Equation to determine the sizes of various light and heavy metallic nanoparticles prepared by pulsed wire discharge

By theoretically considering the critical size during homogeneous nucleation and the atomic mass of different metals, the equation to determine the sizes of nanoparticles prepared by pulsed wire discharge (PWD) is revisited. The new equation is successful at predicting the sizes of Mg particles, for which submicrometer particles were previously reported to be prepared by PWD, even though their sizes were substantially larger than those of nanoparticles such as Cu, Ni, Ag, or Pd prepared by PWD. The temperature of the cross section of the plasma/vapor cloud at the midpoint of the wire when the plasma/vapor expansion attained its maximum volume was estimated to be approximately 0.7 times the boiling temperature of Mg and 0.56 times the boiling temperature of Cu, Ni, Ag, and Pd. These estimated temperatures are assumed to be nucleation temperature and can be predicted by the latent heat of vaporization. The critical sizes of the nanoparticles at these temperatures were calculated, which complemented the previously proposed equation for the determination of particle size by Tokoi et al. [Jpn. J. Appl. Phys. 52(5R), 055001 (2013)]. The estimated temperature T during this time was verified by investigating the temporal evolution of the temperature along the radial axis using conventional hydrodynamic equations. Mg and Cu wires were also experimentally discharged for comparison of the plasma/vapor cloud conditions during the time of interest using a high-speed camera. The consistency of the high-speed photographs with the simulation results, along with the validity for different nanoparticles prepared by PWD, confirmed the feasibility of the revisited equation.

A Global Model for Predicting Vacuum Drying of Used Nuclear Fuel Assemblies

A global model is proposed to simulate the drying process of used nuclear fuel assemblies under vacuum drying conditions. The transient model consists of a coupled mass and energy conservation equation with appropriate source and sink terms. The classic Hertz-Knudsen expression is employed to resolve the evaporation rate and the associated water mass depletion in the system. Both latent heat of vaporization and residual decay heat are considered as sink and source in the energy conservation, respectively. The model is employed to simulate vacuum drying of spent nuclear fuel rod storage systems. Multistage stepwise vacuuming of the system is emulated, and several parametric studies are conducted to identify their role in the drying process. The predicted temporal profiles show that the proposed model is able to capture qualitative trends of the water removal rate, hence the dryness level of the system. The model prediction is also compared against experiments where the amount of residual water after a standard vacuum drying procedure is quantified. The predictions are found to compare favorably with the experimental measurements.

Predicting Conduction Heat Flux through Macrolayer in Nucleate Pool Boiling

In the current work, the heat flux in nucleate pool boiling has been predicted using the macrolayer and latent heat evaporation model. The wall superheat (ΔT) and macrolayer thickness (δ) are the parameters considered for predicting the heat flux. The influence of operating parameters on instantaneous conduction heat flux and average heat flux across the macrolayer are investigated. A comparison of the findings of current model with Bhat’s decreasing macrolayer model revealed a close agreement under the nucleate pool boiling condition at high heat flux. It is suggested that conduction heat transfer strongly rely on macrolayer thickness and wall superheat. The wall superheat and macrolayer thickness is found to significantly contribute to conduction heat transfer. The predicted results closely agree with the findings of Bhat’s decreasing macrolayer model for higher values of wall superheat signifying the nucleate boiling. The predicted results of the proposed model and Bhat’s existing model are validated by the experimental data. The findings also endorse the claim that predominant mode of heat transfer from heater surface to boiling liquid is the conduction across the macrolayer at the significantly high heat flux region of nucleate boiling.

Promoted stable combustion of alcohol-based fuel accompanied by inhibition of Leidenfrost effect in a wide temperature range

Combustion of bio-alcohols helps alleviate energy crisis and environmental pollution. However, the Leidenfrost effect (LE) of alcohols triggered by the adiabatic vapor layer greatly reduces the heat transfer efficiency, which makes alcohols exhibit a long ignition delay time (IDT) at low temperatures, hindering energy efficiency and clean combustion. Here, we first develop a scalable strategy to inhibit LE via self-propagating oxidation heat release and concomitant in-situ active radical generation. Reliable ignition and stable combustion of alcohol-based fuels are achieved in a wide temperature range by using a reactive organometallic compound methoxydiethylborane (MDEB). The theoretically released heat of MDEB self-oxidation is two orders of magnitude greater than the evaporation latent heat of ethanol or n-decane by thermodynamic calculation. Experiments show that the flammable temperature limits of MDEB/ethanol and MDEB/ethanol/n-decane are extended to 225 and 125 °C, which dropped by 370 and 465 °C, respectively. Moreover, the IDT of MDEB/ethanol/n-decane hybrid fuel significantly decreases to 27 ms. The 100% ignition achievement and disappearance of negative temperature behavior highlight the reliable start-up in the Liedenfrost region. This work thus provides a promising tool for promoting the ignition reliability and combustion stability of alcohols for ICEs at low temperatures, as well as pollutant control.

Improved thermal multiple-relaxation-time lattice Boltzmann model for liquid-vapor phase change

In this paper, an improved thermal multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for simulating liquid-vapor phase change. A temperature equation is first derived for liquid-vapor phase change, where the latent heat of vaporization is decoupled with the equation of state. Therefore, the latent heat of vaporization can be arbitrarily specified in practice, which significantly improves the flexibility of the present LB model for liquid-vapor phase change. The Laplacian term of temperature is avoided in the proposed temperature equation and the gradient term of temperature is calculated through a local scheme. To solve the temperature equation accurately and efficiently, an improved MRT LB equation with nondiagonal relaxation matrix is developed. The implicit calculation of the temperature, caused by the source term and encountered in previous works, is avoided by approximating the source term with its value at the previous time step. As demonstrated by numerical tests, the results by the present LB model agree well with analytical results, experimental results, or the results by the finite difference method where the fourth-order Runge-Kutta method is employed to implement the discretization of time.

Flow boiling heat transfer performance of copper-alumina micro-nanostructured surfaces developed by forced convection electrodeposition technique

The stability and adhesion of developed surfaces to the substrate is directly influenced the boiling performance with respect to the recurring trial runs. For the commercial application point of view, the stability of developed surfaces is an important concern. Therefore, a new multi-step forced convective electrocodeposition technique is proposed for further improvement in adhesion, nucleation sites, wettability, and flow boiling heat transfer. The uniform particles deposition on the surface is achieved by forced convection electrodeposition technique. The SEM images, porosity, wettability, coating thickness, EDS spectrum, and surface roughness are carried out in order to analyze the surface behaviors of the surfaces. The flow boiling tests are conducted on considered surfaces at different mass flow rates with DI water. The maximum variations of 5.3% in critical heat flux (CHF) and 1.3°C in surface temperature are monitored for micro-nanostructured (MS#2) surface between the first and fifth test run. The incipience of boiling (ONB) for MS#2 surface is occurred at surface temperatures of 100.3, 102.1, 103.4, and 106.5°C for the mass fluxes of 53, 113, 268, and 361 kg/m2s, respectively. The maximum augmentation in CHF (~176%) and heat transfer coefficient (~200%) are achieved on MS#2 surface at lower mass flux.Statement of novelty and Significance: The boiling heat transfer mechanism is an efficient heat transfer mode and able to achieve large amount of heat extraction with very small wall superheat temperature from the critical equipments though sensible heat and latent heat of vaporization. In boiling heat transfer process, being a vigorous process, the stability and adhesion of developed surfaces to the substrate is directly influenced the boiling performance with respect to the repetitive test runs. For the commercial application point of view, the stability of developed surfaces is an important concern. Therefore, In the present study, a new four-step (deposition-sintering-deposition sintering) forced convection electrodeposition technique is conceptualized and used in the present work for further improvement in adhesion, nucleation sites, wettability, and boiling heat transfer. The flow boiling tests are conducted on micro/nanostructured surfaces at different mass flow rates with DI water (working fluid). More improvements in CHF and HTC have been monitored with the developed micro- nanostructured Cu-Al2O3 (MS#2) surface.

Theoretical analysis of vapour refrigeration cycle with hybrid refrigerant of different types and mixing ratios

In this paper analytical study has been made to investigate a hybrid refrigerant consists of different refrigerants with different mixing ratios and find out its effects on the performance of cycle and specify the best refrigerant that gives best performance and least environmental pollution. Firstly the performance of vapor compression refrigeration system has been analyzed with several different pure refrigerants( R11, R12, R13,R22,R23, R32, R41, R115, R116, R124, R125, R134a, R142a, R143a, R152a) by REFPROP software and the values of coefficient of performance (COP) and mass flow rate ( ) and work in compressor (Wc) for each pure refrigerant is calculated and by use other properties for every refrigerant it can determine the best refrigerants to make a new refrigerant that comes from mixing of two or three of pure refrigerants with best performance for example R22 and R134a with mixing ratios (25:75),(50:50),(75:25) respectively Assuming the evaporator temperature is (-10 °C) and the condenser temperature is (35 °C). The main parameters are calculated such as new refrigerant, mass flow rate and work used in compressor for various capacity in (kW). The results showed that the maximum performance recorded with R134a and the minimum value with R115 while the values of performance for their mixtures fluctuated between the maximum and minimum values for the pure refrigerants and the cause of this is due to combination of properties as boiling point temperature and critical temperature, latent heat of vaporization, specific heat of liquid and specific volume of the vapor

Investigation of Extinguishment process of Liquid Hydrocarbon Flames by Aqueous Suspensions of Astralenes

The extinguishing properties of aqueous suspensions with carbon nanoparticles (astralenes) used for extinguishment of liquid hydrocarbon flames were investigated. The extinguishment time (τ) was found to decrease by 75–80% with increasing of astralene concentrations (φ) from 0 vol.% to 0.5 vol.%. As the concentration is further increased above 1.0 vol.%, the value of τ also increases. Such changes are caused by the dependence of the latent heat of vaporization and heating rate of suspension to the boiling point on astralene concentration. The effects of nanoparticle concentration and size on nanofluid permittivity were determined. For nanofluids containing 1.0–1.5% astralenes, the permittivity was found to enhance with increasing the distances between nanoparticle agglomerates. Ultimately, these physical processes negatively affect the transport characteristics and extinguishing properties of the suspension.