Increase In Inlet Temperature Research Articles

Single-crystal height extension by Laser Metal Deposition of CMSX-4

The introduction of directionally solidified and single-crystal nickel-based superalloys have led to a higher thermal efficiency of engines by allowing for an increase in turbine inlet temperatures from 1000°C to 1400°C. These temperatures however lead to higher thermal stress and corrosive environments, resulting in a shorter life span. Previous work has shown the applicability of laser metal deposition (LMD) for the regeneration of these high value components, while maintaining primary crystalline orientation of single-crystal high pressure turbine blades. However, the processing of these materials by LMD poses several challenges, such as susceptibility to cracking, the formation of misoriented grains and low weldability. This paper examines deposition strategies to extend single-crystal height. While a continuous, meandering strategy shows the most promising percentage single-crystallinity results, an additional remelting step increases epitaxial deposition height. Apart from percentage single-crystallinity and deposition height, this study quantifies the effect of these strategies on cracking and the formation of misorientations.

MELTING CHARACTERISTICS OF CAPSULATED PHASE CHANGE MATERIALS

An experimental and computational investigation studied phase change material melting in a cylindrical capsule with PCM. The capsule is placed horizontally in a rectangular test section, where it is insulated from all sides’ wall except the front one. The PCM capsule is heated by passing hot water from downward to upward with different inlet mean water temperatures (327.9, 333.7, 338 and 343) K, different velocities, varied thermal conductivities of capsule material wall (copper, iron, pyrex-glass, and polyethylene), and PCM. Experiment during melting inside a pyrex-glass capsule was performed and compared with prediction analysis by using CFD ANSYS 2019 R2. Image processing of melting photographs along with melted time were used in comparison. The comparison between the liquid fraction and energy stored with time for lauric acid and paraffin wax was analyzed. PCM liquid fraction, temperature and energy stored measurements for lauric acid were assessed numerically. The results reveal for lauric acid that the total melting time was enhanced 43% for 4.6% increase in water mean inlet temperature, 18% for 500% increase in inlet water mean velocity, and 7% when used copper capsule wall. The results proved that the lauric acid charged with energy stored were 47% more than paraffin wax during the total melting time of it, and the effect of different water mean inlet temperatures was the main factor for the charging process to improve the PCM melting time.

Experimental investigation on the influence of internal heat exchanger in a transcritical CO2 heat pump water heater

In this paper, a transcritical CO2 heat pump water heater prototype was experimentally investigated to research the influence of internal heat exchanger (IHX). In addition, the exergy analysis was carried out based on the experimental data. The results showed that the optimal discharge pressure reduced with the application of IHX, and this reduction could be amplified by the decrease of the ambient temperature, the increase of the water inlet temperature and the increase of the water outlet temperature. From the energy point of view, under the optimal discharge pressure, the coefficient of performance (COP) increased by up to 6.65% and the total power consumption decreased by up to 6.22% via using IHX. Then the influence of IHX on the heat pump cycle was discussed. The results of the exergy analysis showed that the exergy destruction of compressor, gas cooler and evaporator increased, and the exergy destruction of expansion valve decreased with the application of IHX. Furthermore, the product exergy and the total exergy destruction increased, and the exergy efficiency of system decreased in all working conditions. In conclusion, the application of IHX enhanced the energy performance and impaired the exergy efficiency in this research.

PARAMETRIC INVESTIGATION OF ORGANIC RANKINE CYCLE EVAPORATOR FOR LOW TEMPERATURE APPLICATIONS

The present work deals with the development of thermodynamic model of low temperature basic Organic Rankine Cycle (ORC) system and a chevron plate heat exchanger evaporator sub-model using Engineering Equation Solver (EES). Work output is evaluated using the ORC thermodynamic model, while the evaporator sub-model calculates the total surface area of the heat exchanger. Using these mathematical models, the effect of evaporation pressure, expander inlet temperature and pinch point temperature difference (PPTD) on the network output and evaporator cost are studied. In addition to this, the effect of plate spacing and plate width of chevron plate heat exchanger on pressure drop and evaporator cost are analyzed in detail. Finally, thermodynamic and geometric optimization is carried out using genetic algorithm to identify the optimum parameters at which the network output is maximized and pressure drop in the evaporator is minimized. Sensitivity analysis showed that optimum evaporator pressure existed at which network output is maximum. Thermodynamic optimization showed that work output was maximum (5.03 kW) at evaporator pressure of 5.77 bar. No improvement in the work output was seen with increase in PPTD and expander inlet temperature. Increase in plate width and plate spacing led to increase in evaporator cost and decrease in pressure drop.

Experimental study on heat and mass transfer of a multi-stage planar dehumidifier

Removing excessive moisture from the ambient air by means of a selective membrane in the membrane-based dehumidifier has become a new emerging technology. The present study pertains to the experimental work on heat and mass transfer of a multi-stage planar membrane dehumidifier. Commercial Nafion 212 membranes are applied in this membrane dehumidification system because of the large selectivity. The operating conditions of inlet dry air are fixed to maintain at temperature of 27ºC and relative humidity of 0.1% while performing dehumidification tests. Attention is mainly paid to examining the effects of various temperature, relative humidity and flow rate of the wet side inlet air on performance indexes including the dehumidification rate (DR), dew point approach temperature (DPAT), pressure loss (ΔP), and pumping power (Ω) in planar membrane-based dehumidifiers. Measured results show that increasing inlet temperature, relative humidity and flow rate of humid air in the wet channel enhances performance indexes, that is, higher DR, DPAT, ΔP and Ω. In addition, the counter flow configuration in the dehumidifier provides better mass and heat transfer performance compared to parallel flow configuration.

Flooding numerical simulation of heterogeneous oil reservoir using different nanoscale colloidal solutions

In this study, flooding of oil reservoir by implementing Nanoscale colloidal solutions as a working fluid is simulated. All oil reservoirs are heterogeneous porous media; therefore, in this investigation for more accurate prediction of the problem, the porous media is considered heterogeneous. The governing equations of this problem are solved by finite element method (FEM). Moreover two-phase equations of Darcy and mass transfer equations are used.In this paper, the effect of temperature and volume fractions of nanoparticles on the rate of oil recovery is investigated. The SiO2, Al2O3, and CuO nanoparticles are used in the enhanced oil recovery (EOR) process. Also, in order to solve the dual-phase equations of Darcy, the relative permeability model of “Raafat” and the capillary pressure of “Brooks-Corey” have been used. Finally, the effect of volume fraction of nanoparticles on porosity and absolute permeability of the environment in the enhanced oil recovery process is investigated. The results showed that increasing inlet temperature has a high role in (EOR) process because changing the viscosity and density. Also at a concentration of less than 5%, the effect of precipitate is only shown in terms of porosity and absolute permeability of the environment.

The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.

Heat transfer characteristics of water flowing through micro-tube heat exchanger with variable fluid properties

The heat transfer characteristics of laminar single-phase forced convective water flow through a micro-tube heat exchanger are numerically investigated in this paper. Two-dimensional simulations are performed to find the effects of variable fluid properties on heat transfer for hydrodynamically and thermally developed flow. The effects of variable fluid properties on convective heat transfer coefficient (h) and Nusselt number (Nu) are significant for micro-convective flow. It is noted that the variation in temperature-dependent thermal conductivity [k(T)] greatly enhances the h as compared to the variation in temperature-dependent viscosity [µ(T)], although water viscosity–temperature sensitivity (SμT) is greater than that of thermal conductivity–temperature sensitivity (SkT). The effects of variation in wall heat flux (\(q_{\text{w}}^{\prime\prime}\)) and inlet temperature on heat transfer are investigated for variable fluid properties. It is noted that the Nu declines with an augment in \(q_{\text{w}}^{\prime\prime}\) for temperature-dependent density variation [ρ(T)]. The Nu increases with an increase in \(q_{\text{w}}^{\prime\prime}\) for µ(T) and k(T) variations. The results show that the Nu decreases with an increase in inlet temperature for variable fluid properties. The undevelopment and redevelopment of the flow are observed due to µ(T) variation. Additionally, the effects of wall heat flux, inlet temperature and inlet velocity on the variation of Nu/Pr1/3 with Re are examined for µ(T) variation.

Numerically thermal analysis of a turbine vane at high temperature

Using conjugate heat transfer, thermal analysis of a turbine vane coated with thermal barrier coating (TBC) at a high temperature is presented. Numerical results are carried out at two turbine inlet temperatures (T ∞) i.e. 783 K (low) and 1566 K (high) under two turbulence intensities (Tus) i.e. 8.3% and 16.6%. The main findings of this research are that for both Tus, the metal surface temperature reduction at the high temperature is higher than that at the low temperature because of the lower heat-flux ratio at the higher temperature. Based on the metal temperature reduction, the increasing inlet temperature has a greater influence than the increasing turbulence intensity. The results also indicate that at T ∞ = 783 K, on the pressure side (PS) the metal surface temperature reduction at Tu = 8.3% is lower than that at Tu = 16.6%, while on the suction side (SS) no significant difference happens when Tu increases. Interestingly, an inverse phenomenon happens for both PS and SS, that is the metal surface temperature reduction at Tu = 8.3% increases above that at Tu = 16.6% when T ∞ increases. This discrepancy may suggest the instability of the surface heat-flux ratio due to complex heat convection at the different inlet temperatures.

Performance analysis of a vertically oriented concentric-tube PCM based thermal energy storage system: Parametric study and correlation development

Latent heat based thermal energy storage systems stores energy which can be retrieved whenever required. Total melting time (or melting rate) is an important parameter which governs suitability of any system for a given application. In the present work, a numerical analysis has been performed on the vertically orientated concentric double-pipe storage system. Effect of phase change material (PCM) properties, flow parameter and geometric parameters of the storage system on total PCM melting time are studied. Enthalpy-porosity technique has been used to model the phase change process apart from governing fluid flow and energy equations. It is found that with the increase in melting temperature and latent heat, the total melting time increases whereas the total melting time decreases with increase in the heat transfer fluid inlet temperature and aspect ratio. 74.11% decrease in the total melting time has been observed when melting temperature is decreased from 343 K to 323 K with latent heat 144 kJ/kg, heat transfer fluid inlet temperature 348 K and aspect ratio 11.76. A correlation for the total melting time comprehending the effect of all studied parameters has been developed which can provide the total melting time within ±15% accuracy.

Effect of spray-drying temperature on physicochemical, antioxidant and antimicrobial properties of pectin/sodium alginate microencapsulated carvacrol

Microencapsulation has been extensively utilized in the pharmaceutical and food industries to entrap essential oils related to flavoring. Spray-drying is one of the most commonly used microencapsulation techniques in the food industry because of its low expense and readily available equipment. The spray-drying operating parameters, particularly inlet temperature, affect the physicochemical and functional properties of the microcapsules. In this research, four inlet air temperatures (100, 130, 160, and 190 °C) were applied for the encapsulation of carvacrol in a matrix composed of pectin/sodium alginate. The 100 °C treatment resulted in the highest moisture content, bulk density, and retention efficiency, but lowest dissolution time, hygroscopicity, and encapsulation efficiency. The antioxidant activity evaluated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay decreased, while the antimicrobial activity with respect to Escherichia coli K12 assessed by minimum inhibitory concentration (MIC) increased with the increasing inlet temperature due to the reduced retention efficiency. The microcapsules produced at lower temperature were smaller, smoother, and more spherical. Our results indicate that an inlet temperature between 100 and 130 °C is the ideal for processing pectin/sodium alginate encapsulated carvacrol.

Protective effects of the use of taro and rice starch as wall material on the viability of encapsulated Lactobacillus paracasei subsp. Paracasei

In this study, was evaluated the protective effect of two microencapsulation materials of different sized starch granules, taro (5.16 μm) and rice (6.99 μm), on the survival of Lactobacillus paracasei subsp. paracasei (LPSP) at controlled spray-drying inlet air temperatures of 70, 115, and 135 °C. Physicochemical properties, encapsulation efficiency, and gastrointestinal viability of microcapsules were analyzed. Rice microcapsules showed a slight increase in water activity and moisture values when compared with taro microcapsules. Viability of the microcapsules was affected drastically with the increase in inlet temperature during spray-drying. Small-sized taro starch granules showed a better formation of spherical aggregates for one logarithmic cycle in the initial viability of LPSP. Electron microscopy showed less LPSP on the outside of the taro starch microcapsules. The findings in this study indicated that use of microcapsules constructed from taro starch can offer better protection to probiotic strains.

Numerical study on the effects of battery heating in cold climate

Abstract At low temperature, the performance of battery declines significantly. Thus Battery Thermal Management System (BTMS) for heating and maintaining its temperature in proper range is crucial when the batteries of electric vehicle operate in cold climate. The objective of this study is to investigate the effects of heating parameters on the heating performance of BTMS based on heat/cold plate method. A 3D model of 6 battery cells and heat/cold plate was built in COMSOL. The numerical study considered three effects under the cold climate of −20 °C, which are the discharge rate of battery, inlet mass flow rate of heating medium and inlet temperature. According to the results, the batteries cannot be heated to its proper operating temperature range only by vaChongqingrying the discharge rates of battery. In addition, the discharge rates also have a negligible effect on the temperature raising compare with external heating source. With external heating source, higher mass flow rate can achieve a better heating performance, but it is limited when the mass flow rate exceeds 0.065 kg/s, which increase of the heating medium inlet temperature can more quickly heat up the batteries, but it may lead to the maximum temperature of batteries exceeds 40 °C. Among the calculated temperatures, the inlet temperature around 45 °C can be a reasonable temperature for the battery heating of BTMS based on heat/cold plate.

Exergy and economic assessments of solar organic Rankine cycle system with linear V-Shape cavity

In this research, a parabolic trough concentrator with linear V-Shape cavity receiver was studied as the heat source of an organic Rankine cycle system. The solar organic Rankine cycle system was evaluated under exergy and economic analyses. Thermal oil was used as the solar working fluid, and ethanol was used as the organic working fluid under different turbine inlet temperatures and turbine inlet pressure. The influence of different operational parameters, including solar radiation, mass flow rate, and inlet temperature of solar working fluid was investigated on the performance of the solar organic Rankine cycle system. It was found that exergy gain and exergy efficiency of the solar system improved with increasing solar radiation, increasing inlet temperature, and decreasing the flow rate of the solar working fluid. The highest organic Rankine cycle efficiency and total efficiency were found to be 35%, and 25% at turbine inlet temperature of 592 K and turbine inlet pressure of 6 MPa, respectively. Finally, the lowest levelized cost of electricity, and the lowest payback period were calculated equal to 0.0716 (€/kWh), and 8.79 (years) for the optimum condition of the developed solar organic Rankine cycle system, respectively. The present study is beneficial for improving the performance of the solar organic Rankine cycle systems with parabolic trough concentrators in a simple and convenient way and the development of solar thermal technologies.

Analysis of Coupled Wellbore Temperature and Pressure Calculation Model and Influence Factors under Multi-Pressure System in Deep-Water Drilling

The purpose of this paper is to discuss the variation of wellbore temperature and bottom-hole pressure with key factors in the case of coupled temperature and pressure under multi-pressure system during deep-water drilling circulation. According to the law of energy conservation and momentum equation, the coupled temperature and pressure calculation model under multi-pressure system is developed by using the comprehensive convective heat transfer coefficient. The model is discretized and solved by finite difference method and Gauss Seidel iteration respectively. Then the calculation results of this paper are compared and verified with previous research models and field measured data. The results show that when the multi-pressure system is located in the middle formation, the temperature of the annulus corresponding to location of the system is the most affected, and the temperature of the other areas in annulus is hardly affected. However, when the multi-pressure system is located at the bottom hole, the annulus temperature is greatly affected from bottom hole to mudline. In addition, the thermo-physical parameters of the drilling fluid can be changed by overflow and leakage. When only overflow occurs, the annulus temperature increases the most, but the viscosity decreases the most. When only leakage occurs, the annulus temperature decreases the most and the viscosity increases the most. However, when the overflow rate is greater than the leakage rate, the mud density and bottom-hole pressure increase the most, and both increase the least when only leakage occurs. Meanwhile, bottom-hole pressure increases with the increase of pump rate but decreases with the increase of inlet temperature. The research results can provide theoretical guidance for safe drilling in complex formations such as multi-pressure systems.

Optimal allocation of heat exchangers in a Supercritical carbon dioxide power cycle for waste heat recovery

Supercritical carbon dioxide (sCO2) power cycles have attracted attention because of their high efficiency and flexibility in various temperature heat sources including low-temperature waste heat applications. In waste heat applications, the size of the heat exchangers is an important issue because of the trade-off between performance and installation cost. For the optimal design of an sCO2 cycle for waste heat recovery, a thermodynamic model for the basic cycle and the preheating cycle was constructed. The heat exchangers were then modeled by a finite volume analysis under the fixed total UA value, with the equivalent conductance representing the size of the heat exchanger. The net power and thermal efficiency of the cycle were calculated. The results of the optimization confirmed that the application of the preheater improves the performance of the basic cycle, and an optimum point of the split ratio exists. From the simulation, with an increase in the turbine inlet temperature (TIT), the thermal efficiency improves, but the net power does not always increase. Instead, a close linearity between the optimum CO2 split ratio (ϕ) and the turbine inlet temperature was found at the maximum net power, even under different turbine inlet pressures and total UA values. From these results, the configuration of heat exchangers for waste heat applications can be planned appropriately to operate at the maximum net power.

Numerical Predictions on the Influences of Inlet Temperature and Pressure of Feed Gas on Flow and Combustion Characteristics of Oxy-pulverized Coal Combustion

ABSTRACT Carbon capture and storage employing oxy-fuel combustion is one of the most promising options to reduce greenhouse gas emission. For the transition from conventional air-fired combustion to oxy-fuel combustion, there is a necessity of detailed investigation of various phenomena that occur during oxy-fuel combustion. Numerical modeling of oxy-fuel combustion process can serve the purpose effectively and efficiently. The current paper presents a thorough numerical investigation of the combustion process of pulverized coal under oxy-fuel conditions. The influence of inlet temperature and pressure of feed gas is investigated in the present study. Computational fluid dynamics simulation is performed for the test facility located at the Institute of Heat and Mass Transfer at Aachen University. The numerical results obtained employing various Reynolds Averaged Navier Stokes (RANS) models have been compared with measured data. The results showed that the strength and axial dispersion of the internal recirculation zone (IRZ) are enhanced at higher inlet temperature. The combustion of volatile matter present in coal shifts near the burner which results in shorter flames at higher inlet temperature. The flame temperature increased by ~9% with increase in inlet feed gas temperature from 313 to 800 K. Inlet feed gas pressure of 10.0 bar has ~38% increment and ~32% reduction in IRZ length and flame length, respectively, than the base case.

Preliminary design of radial inflow turbine and working fluid selection based on particle swarm optimization

Organic Rankine cycle (ORC) is an efficient technique to recycle the low temperature heat sources. The design method of the critical component, radial inflow turbine, is a main focus of research. A preliminary design method was developed to optimize eight critical parameters based on particle swarm optimization (PSO) algorithm. The isotropic efficiency was the objective function of the algorithm. Six working fluids were selected to conduct turbine design based on the design method. The turbine with R245fa was determined to be optimal due to its small geometry size, high exergy efficiency (0.929) and high load coefficient (1.1027). The off-design performance of R245fa turbine was investigated with the variation of pressure ratio (PR), stator inlet temperature and power output. The results indicate that the turbine efficiencies increase with the reduction of PR and turbine inlet temperature and the increase of power output. The exergy efficiency and isotropic efficiency drop slightly with the increase of turbine inlet temperature. So the turbine with R245fa exhibited good off-design performance.

CFD study of heat transfer and fluid flow in a parabolic trough solar receiver with internal annular porous structure and synthetic oil–Al2O3 nanofluid

In this study, a finite volume method is employed to investigate the performance of a novel parabolic trough solar collector with synthetic oil–Al2O3 nanofluid as the heat transfer fluid. An annular porous structure is installed inside the absorber tube to improve heat transfer. The effects of the simultaneous utilization of porous structure and nanoparticle addition on heat transfer, pressure drop, and thermal efficiency of the receiver are investigated for different values of Reynolds number, volume fraction of nanoparticle, inlet temperature and Darcy number of the porous region. The results show that as Reynolds number and volume fraction of nanoparticle increase, heat transfer coefficient, pressure drop, and thermal efficiency increase. However, the increases in inlet temperature lead to the decreases in heat transfer coefficient, pressure drop, and thermal efficiency. At Reynolds numbers higher than 30×104, simultaneous utilization of porous structure with Da = 0.3 and nanoparticles increases heat transfer coefficients nearly 7% and 20%, pressure drops up to 42.5% and 42%, thermal efficiencies up to 8% and 15%, overall efficiencies nearly 5% and 14%, and exergetic efficiencies by 7% and 15% for inlet temperature of 500 and 600 K, respectively.

Experimental investigation of the heat transfer and flow characteristics of microchannels with microribs

The single-phase heat transfer and flow characteristics of microchannels with microribs were investigated experimentally in this paper. Based on a smooth rectangular microchannel (MC-S), rectangular microchannels with rectangular ribs on one side (MC-OSR) and both sides (MC-BSR) were proposed. The effects of the volumetric flow rate and inlet temperature on the Nusselt number and friction factor were analyzed. Five positions were assigned evenly in the flow direction at the wall to measure the temperature and determine the wall temperature distribution. The results showed that the Nusselt number increased as the volumetric flow rate and inlet temperature increase. The friction factor decreased with increasing inlet temperature. The thermal performance index of the MC-OSR was higher than those of the MC-BSR and MC-S, which reflected the superior heat transfer performance of the MC-OSR. The wall temperature was nonlinearly distributed in the flow direction. The amplitude of the temperature difference gradually decreased. Compared to the MC-S, the entrance effects of the MC-OSR and MC-BSR were more obvious mainly due to the presence of ribs.