Heat and Mass Transfer最新文献

In the context of dual-carbon strategy, the insulation performance of the gathering and transportation pipeline affects the safety gathering and energy saving management in the oilfield production process. PCM has the characteristics of phase change energy storage and heat release, combining it with the gathering and transmission pipeline not only improves the insulation performance of collecting and transporting pipes, but also extends the safe shut time during the shutdown. Proposed a thermal model of a PCM-based composite energy storage pipeline combining the character of phase transformation between PCM and crude oil has been established. The heat preservation performance of the combined energy storage pipeline was evaluated by numerical simulation.This paper analyses the heat transfer performance of complex energy storage pipes, and considers the influence of natural convection and variable temperature zone on insulation performance.On this basis, the structure design of cascade phase transition was proposed, the optimized cascading composite pipe was presented, and the performance of different insulation structures was compared.

Pulsating heat pipes (PHPs) employ to multiphase heat transfer between condensers and evaporators. The efficacy of PHP is predominantly contingent upon the thermos-physical property exhibited by its working fluid. The exergy analysis of evaporator, adiabatic and condenser system were performed to evaluate the efficiency and sustainability of energy conversion processes, it was also seen that exergy loss of condenser was 1.01% higher than evaporator. Further, 2-D numerical simulation of a cryogenic pulsating heat pipe (CPHP) was conducted and also numerical and experimental simulation was conducted, where simulation results agreed with experimental results with 10% similarity. The simulation employs the volume of fluid (VOF) model to capture the dynamics of two-phase liquid–vapor flow within the CPHP employing liquid acetone – Al₂O₃ as the working fluid. The diameter of the single turn is systematically varied, ranging from 1 mm to 2.5 mm, while maintaining the filling ratio (FR) within the range of 25% to 75%. The evaporator temperature is adjusted within the span of 85 K to 115 K. The PHP exhibited best thermal performance at inner diameter of 2 mm among (1, 1.5, 2, 2.5 mm) and filling ratio of 55% among (25%, 45%, 55%, 65% and 75%).

This research examines the water and energy performance in wet cooling towers and identifies methods for enhancing efficiency and minimizing water and energy consumption by exploring methods to enhance system performance. A three-dimensional transient model, developed using MATLAB's open-source code software, was utilized to simulate the cooling tower's behaviour under various operating conditions. This research focuses on precise simulation of cooling tower behavior and demand modeling aided by regression. The model's accuracy was validated through experimental measurements in diverse environmental conditions. The key parameter and performance that is investigated in this paper is the temperature profile of the cooling tower, in which the performance algorithm and proposed methodologies are anchored in the operational temperature. The experimental results led to operational solutions for enhancing cooling tower performance. For winter conditions, the recommended action involves closing the upper part of the cooling tower and activating the two side fans. Specific approaches are suggested for mid-season and summer scenarios, focusing on make-up water consumption and ambient air temperature control, respectively. In addition, results indicated a close alignment between the model and the actual system, with discrepancies of less than 2% in energy consumption and 5% in water consumption. Analysis of proposed productivity enhancements and changes in supply policies indicated significant potential for energy and water conservation in wet cooling towers. Implementing these solutions could lead to an estimated annual reduction of 44% in water consumption and 4.2% in energy consumption.

Water is an emerging heat transfer fluid with great promise for thermal engineering because of its heat transfer coefficients. However, much more must be done with the fluid that transmits heat to make the system more effective in handling heat. Nanoparticle cooling fluid speeds up the movement of heat through the car radiator and makes it possible to make it smaller altogether. In the present study, to examine heat transfer characteristics of nanofluids of Deionized (DI) water and Ethylene glycol (60:40). Four different concentrations of nanofluids were prepared by mixing 0.05 to 0.3 Vol. % of nanofluids with a mixture of DI water and Ethylene glycol (EG). The studies were carried out by varying coolant from 3 to 15 LPM while keeping the airspeed at a mean of 5 m/s. The airflow velocity towards the radiator is continually maintained at a median of 5 m/s. The k-type thermocouple monitors the cooling outlet’s temperature and a comparative study of the thermal conductivity of experimental results with machine learning. The results show that the DI water had a lower thermal conductivity of 0.891 W/m K than the EG nanofluid, which had a thermal conductivity of 0.946 W/m K. The EG nanofluid showed a more significant heat transfer coefficient of 36384.41 W/m² K than the DI water. The viscosity of the nanofluid increases as the concentration of nanofluid in the DI water increases and decreases as the temperature rises.

The aim of this research is to conduct an experiment that will evaluate the effect of combining of counter flow air-impinging arrangement and an arc-shaped turbulators over the absorber plate of solar heater. This combination is intended to improve the thermohydraulic performance of the solar air heater. The parameters such as energy transfer and frictional factor are studied at flow Reynolds number varies from 18,000 to 3600, and the influence of a hole jet bore ratio from 0.0430 to 0.109 is considered. At the optimal hole jet bore ratio of 0.0650, the thermo-hydraulic achievement parameter has a value of 1.75, which is the greatest possible value can be attained. When compared to multi-pass V and multiple V roughened solar air heaters based on the THAP, the current work is improved the performance by 55.3 and 32.9%, respectively. Such comparisons clearly demonstrate the superiority of the present work. Furthermore, a relationship is shown between the jet hole bore ratio and the thermohydraulic performance measure, with a maximum divergence of 10%.

Apricots offer diverse health benefits, making them a valuable component of an attractive diet. In addition to ensuring the physicochemical and microbiological stability during storage and the year-round availability of this nutrient-dense fruit, apricot preservation, especially through sorption isotherm processes, also considers economic, nutritional, and environmental factors. In the same context, this study explores the analysis of two common apricot cultivars in Morocco. The primary objective is to determine the optimal conditions for storing and conserving the investigated products using the standard gravimetric static method at 30 °C, 40 °C, and 50 °C—six one-liter glass jars with insulated lids made up the experimental set-up. A fourth of the glass jar was filled with a saturated salt solution. Weighing 0.100 g (±0.001) g for adsorption and 0.200 g (±0.001) g for desorption, duplicate samples were precisely weighed and put into the glass jars. The outcomes revealed that the adsorption-desorption isotherms for all samples conformed to the characteristic Type II sigmoid pattern. The ideal water activity values to preserve “Aurora” and “Carmen” are 0.36 and 0.38, respectively. It was determined that the best model to describe the sorption curves of “Aurora” and “Carmen” was LESPAM. Analysis of the adsorption-desorption data aimed to determine the moisture content of the monolayer (ranging from 3.4 to 9.7%) and examine the properties of sorbed water within their porous structures and surfaces.

One of the most effective parameters in the thermal treatment of liver cancer by microwave heating method is the changes in the input power to the antenna. This study aims to numerically investigate the effects of the change in the input power to the microwave antenna in the presence of magnetic nanoparticles using the finite element method in liver tumors. Also, the importance of the type of nanoparticles, treatment time and side effects were investigated. According to the results, after the injection of maghemite nanoparticles, the purification time is 7.35 s at a power of 10 W and reaches 6.1 s when the power is increased to 100 W. Also, the ratio of the destroyed healthy volume of the tissue to the tumor volume is less than 20% in the mentioned powers, and the treatment can be considered independent of the power. After the injection of magnetite and FccFePt nanoparticles at a power of 10 W, the treatment time was calculated as 176 s and 295 s, respectively, and with the increase of the input power, the reduction of the treatment time was observed. So that the treatment time was reduced to 58 s and 74 s, respectively, at 100 W. In terms of side effects, for the mentioned nanoparticles, 4.89 and 8.93 times the volume of the tumor with a power of 10 W and when the power reaches 100 W, 4.05 and 5.6 times the volume of the tumor is destroyed from the healthy tissue, respectively. However, the lowest amount of healthy tissue destruction in these two nanofluids occurs at moderate powers—60 W and 50 W, respectively—so the dependence of treatment time and side effects on input power was observed.

A vehicle’s cooling cycle plays a major role in preventing overheating of the engine or excessive operating temperatures. The engine will run as effectively as possible under all circumstances if the operating temperature is set to the optimal value. Also, maintaining the characteristics of the lubricant that separates the surfaces that contact one another. Enhancing the radiator’s thermal performance is one of the options being researched by scientists right now in order to boost the cooling cycle’s effectiveness. To enhance heat transmission, nanofluids are now often used and are the topic of research. In an experimental study, the performance of using multi-wall carbon nanotubes (MWCNTs) with varied concentrations of nanofluid as operating fluids in an automotive radiator with louvered fins and flat tubes (Honda Civic 2005) was examined. Nanofluids were created using five volumetric concentrations of nanomaterials (0.2%, 0.4%, 0.8%, 1%, and 1.6%). The flow inside the tube had a Reynolds number that fluctuated from 11,000 to 58,000. It is possible to calculate the Nusselt number, pressure drop, friction factor, heat transfer coefficient, and heat transfer rate by measuring the variables. Experimental results show that when MWCNTs concentration and flowrate increase, the heat transfer rate and heat transfer coefficient also increase. The volume concentration of the nanoparticles is what has caused the Nusselt number value to rise by 13.72% in comparison to pure water. For estimating the Nusselt number, a correlation between the Reynolds number and MWCNTs volume concentration is provided.

In thermal design of space applications, calculating thermal contact conductance present a challenge. The absence of convective heat transfer necessitates the essential requirement for a comprehensive of thermal contact conductance and the pivotal physical factors that influence it. This article explores a thermal management for 3U CubeSat in LEO. It covers the space thermal environment, thermal analysis methodology, and the determination of thermal contact conductance using both elastic and plastic models. The study also outlines CubeSat design considerations and the assumptions made for simulations using Comsol Multiphysics software. Experimental results from thermal balance tests are presented and compared to simulations results. The research concludes that the CMY method is the best suited for CubeSat applications to identify the thermal contact conductance, but notes the need for further refinement when dealing with materials that have high roughness or less-than-ideal contact conditions.

This study investigated the effect of large values of relative surface roughness on the heat transfer and pressure drop characteristics using simultaneously measured heat transfer and pressure drop data. Experiments were conducted using a horizontal circular tube with a base inner diameter of 5 mm and length of 4 m. One smooth and two rough tubes, with relative roughnesses of 0.04 and 0.11, were tested at different constant heat fluxes between Reynolds numbers of 100 and 8 500. Water was used as the test fluid and the Prandtl number varied between 3 and 7. Contrary to the trend in the Moody Chart, a significant increase in laminar friction factors with increasing surface roughness was observed. Both the friction factors and Nusselt numbers as functions of Reynolds number showed a clear upward and leftward shift with increasing surface roughness across the different flow regimes. Furthermore, the boundaries between the flow regimes were the same for the pressure drop and heat transfer results. The width of the transitional flow regime was narrower for rough tubes and had a differing trend. The quasi-turbulent and turbulent flow regimes occurred at lower Reynolds numbers for increasing roughness. When investigating the relationship between heat transfer and pressure drop, it was found that an increase in surface roughness favoured heat transfer in the quasi-turbulent flow regime. This is useful for rough tubes as the quasi-turbulent flow regime onsets early with regards to the Reynolds number in tubes with large roughnesses.