Experiments on Thermosyphon Loops for Low-Temperature Waste-Heat Recovery

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Koji Matsubara ◽  
Suguru Tachikawa ◽  
Itaru Kourakata ◽  
Yusaku Matsudaira
Keyword(s):  
Thermal Resistance ◽  
Heating Rate ◽  
Waste Heat ◽  
Volume Ratio ◽  
Pressure Head ◽  
Working Fluid ◽  
Heating Rates ◽  
Different Temperatures ◽  
Flow Circulation ◽  
Flow Map

We tested a thermosyphon loop with water as the working fluid using heating rates between 100 W and 400 W. Four kinds of core blocks were installed in the evaporator and tested: a hollow block, and blocks with narrow holes: Φ 2.2 mm × 90; Φ 2.5 mm × 55; and Φ 4.0 mm × 30. The temperature distribution indicated stable flow circulation inside the thermosyphon at low volume ratios but was unstable when the volume ratio was increased higher than 30%. The characteristics of the flow pattern are summarized as a flow map showing the heating rate versus the volume ratio. The recovered heat and the thermal resistance of the thermosyphon loop were clearly improved by using the core blocks with narrow holes instead of hollow blocks for the treated volume ratios from 20% to 80%. The thermal resistance increased when the volume ratio reached high values, suggesting that the effects from the abnormality of the flow circulation affected thermal resistance. The velocity of the gas stream in the thermosyphon was estimated by assuming an isothermal state, and it is diagrammed showing the heating rate at different temperatures. The current experiment of the thermosyphon loop is plotted in this diagram, which indicates the need for a wide margin due to the limitations of the sonic velocity and the pressure head at the full height of the heat pipe.

scholarly journals Thermal Performance of Micro-Pulsating Heat Pipe

2019 ◽  
Vol 8 (6) ◽  
pp. 2786-2791
Keyword(s):  
Thermal Resistance ◽  
Temperature Profile ◽  
Thermal Performance ◽  
Heat Input ◽  
Computational Study ◽  
Working Fluid ◽  
Pulsating Heat Pipe ◽  
Ansys Fluent ◽  
Vof Model ◽  
Flow Circulation

In this study, thermal performance of MPHP is investigated computationally. A case with 0.7mm hydraulic diameter with 7 turns is considered for the study. Simulation is carried out using ANSYS-FLUENT® software by considering water as working fluid with the help of VOF model. Computational study shows the oscillation of fluid inside and formation of new vapor slugs. The heat input is varied from 1.2 W to 4.8 W in the step of 1.2. Flow circulation inside the MPHP is not unidirectional and frequently changes with the pressure disturbance created in the channels. The temperature profile from computational study shows the startup condition is changing with heat input. Thermal resistance of the MPHP decreases with increase in heat input and the corresponding thermal resistance found to be varied from 3.94 to 3.65 K/W.

The Effect of Heating Rate and Temperature on Mechanical and Microstructure Properties of β-TCP by Microwave Sintering

2017 ◽  
Vol 264 ◽  
pp. 91-94
Author(s):  
Chuthathip Mangkonsu ◽  
Ahmad Fauzi Mohd Noor ◽  
Banhan Lila ◽  
Kawashita Masakazu
Keyword(s):  
Heating Rate ◽  
Microwave Sintering ◽  
Sintered Sample ◽  
Mechanical Analysis ◽  
Heating Rates ◽  
Microwave Furnace ◽  
Different Temperatures

This aim of this work was to evaluate the influences of the heating rates and sintering temperatures for sintering β-TCP by microwave furnace. In the first part of work, the heating rates used for sintering β-TCP were including 10, 20, 30 and 40°C/min. Results from physical and mechanical analysis shown that the optimum properties were shown by samples produced at heating rate of 30°C/min. In the second part of the study, the heating rate of 30°C/min was continuing used to sintering samples by different temperatures (1200°C, 1250°C and 1300°C). The sintered sample at 1200°C presented the optimum properties in the physical and mechanical analysis. Finally, the sintered samples by the heating rate 30°C/min at 1200°C were in immersed in SBF to confirm the bioactivity property of β-TCP.

scholarly journals Impact of Heating Rates on Alicyclobacillus acidoterrestris Heat Resistance under Non-Isothermal Treatments and Use of Mathematical Modelling to Optimize Orange Juice Processing

Foods ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1496
Author(s):  
Juan-Pablo Huertas ◽  
María Ros-Chumillas ◽  
Alberto Garre ◽  
Pablo S. Fernández ◽  
Arantxa Aznar ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Heat Resistance ◽  
Heating Rate ◽  
Heat Treatments ◽  
Microbial Inactivation ◽  
Economic Losses ◽  
Inactivation Kinetics ◽  
Heating Rates ◽  
Alicyclobacillus Acidoterrestris ◽  
Heating Phase

Alicyclobacillus acidoterrestris is a spoilage microorganism responsible for relevant product and economic losses in the beverage and juice industry. Spores of this microorganism can survive industrial heat treatments and cause spoilage during posterior storage. Therefore, an effective design of processing treatments requires an accurate understanding of the heat resistance of this microorganism. Considering that industrial treatments are dynamic; this understanding must include how the heat resistance of the microorganism is affected by the heating rate during the heating and cooling phases. The main objective of this study was to establish the effect of heating rates and complex thermal treatments on the inactivation kinetics of A. acidoterrestris. Isothermal experiments between 90 and 105 °C were carried out in a Mastia thermoresistometer, as well as four different dynamic treatments. Although most of the inactivation takes place during the holding phase, our results indicate the relevance of the heating phase for the effectiveness of the treatment. The thermal resistance of A. acidoterrestris is affected by the heating rate during the heating phase. Specifically, higher heating rates resulted in an increased microbial inactivation with respect to the one predicted based on isothermal experiments. These results provide novel information regarding the heat response of this microorganism, which can be valuable for the design of effective heat treatments to improve product safety and stability. Moreover, it highlights the need to incorporate experimental data based on dynamic treatments in process design, as heating rates can have a very significant effect on the thermal resistance of microorganisms.

scholarly journals Transient Liquid Phase Sintering of PM Steel—A Matter of the Heating Rate

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1662
Author(s):  
Stefan Geroldinger ◽  
Raquel de Oro Calderon ◽  
Christian Gierl-Mayer ◽  
Herbert Danninger
Keyword(s):  
Liquid Phase ◽  
Heating Rate ◽  
Transient Liquid Phase ◽  
Liquid Phase Sintering ◽  
Alloying Elements ◽  
Heating Rates ◽  
Different Temperatures ◽  
Transient Liquid Phase Sintering ◽  
Heating Up ◽  
Cct Diagrams

Powder metallurgy (PM) offers several variants to introduce alloying elements for establishing the desired final composition. One route is the master alloy (MA) approach. The composition and the elements contained in the MA can be adjusted to obtain a liquid phase that penetrates through the interconnected pore network and thus enhances the distribution of the alloying elements and the homogenization of the microstructure. Such a liquid phase is often of a transient character, and therefore the amount of liquid formed and the time the liquid is present during the sintering are highly dependent on the heating rates. The heating rate has also an impact on the reaction temperatures, and therefore, by properly adjusting the heating rate, it is possible to sinter PM-steels alloyed with Fe-Cr-Si-C-MA at temperatures below 1250 °C. The present study shows the dependence of the melting regimes on the heating rate (5, 10, 20, 120 K/min) represented by “Kissinger plots”. For this purpose, liquid phase formation and distribution were monitored in quenching dilatometer experiments with defined heating up to different temperatures (1120 °C, 1180 °C, 1250 °C, 1300 °C) and subsequent quenching. Optimum sintering conditions for the materials were identified, and the concept was corroborated by C and O analysis, CCT diagrams, metallographic sections, and hardness measurements.

Mechanical Behaviors of Magnesium Alloy AZ61 under Different Strain Rates and Heating Rates

2011 ◽  
Vol 686 ◽  
pp. 208-212
Author(s):  
Bin Chen ◽  
Quan Yuan ◽  
Ji Luo ◽  
Ding Fei Zhang ◽  
Guo Zheng Quan
Keyword(s):  
Magnesium Alloy ◽  
Heating Rate ◽  
Ultimate Strength ◽  
Testing System ◽  
Strain Rates ◽  
Mechanical Behaviors ◽  
Heating Rates ◽  
High Heating ◽  
Different Temperatures ◽  
Fracture Section

The effects of strain rate (SR) and heating rate (HR) on the mechanical behaviors of the tensile specimens of magnesium alloy AZ61 were experimentally investigated using a Gleeble-1500 thermal-mechanical material testing system. It showed that the higher the temperature is, the lower the ultimate strength of the specimens will be. The higher the heating rate is, the higher the ultimate strength of the specimens will be. The metallurgraphs of the fracture section of the specimens were also experimentally investigated for exploring their failure mechanism under different temperatures and heating rates. It showed that the high temperatures and high heating rates will induce microvoids in the specimens. The microvoids make the specimens failure under relative low loads.

Study on Thermal Conductivity of SPS-Sintered Si3N4 Ceramics after Heat-Treatment

2005 ◽  
Vol 475-479 ◽  
pp. 1279-1282 ◽  
Author(s):  
Xin Lu ◽  
Xiao Shan Ning ◽  
Wei Xu ◽  
He Ping Zhou ◽  
Ke Xin Chen
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Heating Rate ◽  
Great Influence ◽  
Heating Rates ◽  
Plasma Sintering ◽  
Heat Treated ◽  
Different Temperatures ◽  
Spark Plasma ◽  
Si3n4 Ceramics

α-Si3N4 ceramics were sintered at a low temperature of 1773K by using a spark-plasma-sintering (SPS) method with different heating rates, and then they were further heat-treated at different temperatures from 1773K to 2273K, to study the effect of the heating rate of SPS on the microstructure and the thermal conductivity of Si3N4 ceramics after the heat-treatment. Results show that the heating rate of SPS has great influence on the phase transformation and the microstructure of the β-Si3N4, but it has little influence on the thermal conductivity of the ceramics. This proves that the thermal conductivity of the ceramics does not have an obvious relationship with the ratio and the size of the columnar β-Si3N4 grain.

Analysis and Comparison Between Fixed and Variable Volume Ratio Expander for Micro-Scale ORC

2015 ◽  
Author(s):  
Sergei Gusev ◽  
Martijn van den Broek
Keyword(s):  
Waste Heat ◽  
Volume Ratio ◽  
Optimal Operation ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Variable Volume ◽  
Fixed Volume ◽  
Wide Range ◽  
The Right

Waste heat recovery has become very important in the last decennia. The Organic Rankine Cycle is the most popular technology to transform waste heat into mechanical work or electricity. While large and medium scale installations are widely available on the market for various temperature and power levels, small scale ORCs are still in a pre-commercial phase because of a relatively high specific price. To make small scale ORCs more attractive for potential customers, the price has to be drastically reduced which means reducing the manufacturing and assembling operations, the number of parts in assemblies and unification of these assemblies. In addition, the performance has to be increased by using advanced cycle architectures and the right fluids. Not only the right choice of the working fluid is important but also the expander built-in volume ratio (BVR) has to be optimal or improved. Neither a fixed volume ratio expander, nor a turbine can provide an optimal expansion of a working fluid in a wide range of operating conditions [1]. In automotive applications, for instance, a strongly fluctuating heat input will be introduced to an ORC unit. To estimate losses caused by non-optimal operation, a model of a volumetric expander has been developed and verified using the result of extensive test campaigns with a screw expander. The volume ratio of the expander mentioned cannot be physically changed, so under widely changing pressure ratio, caused by varying inlet waste heat and ambient temperatures, it operates mostly far from its design point. The model gives a possibility to vary the BVR in order to compare a fixed-volume ratio expander with a variable one. Benefits from replacement of this expander by an adaptive one are studied. Only steady states are taken into account since there is no dynamic model of this expander developed yet. As a consequence of the results obtained, a concept of a variable volume ratio expander is proposed.

scholarly journals Investigating the pyrolysis kinetics of Pinus sylvestris using thermogravimetric analysis

BioResources ◽  
2020 ◽  
Vol 15 (3) ◽  
pp. 5577-5592
Author(s):  
Langui Xu ◽  
Jiawei Zhou ◽  
Jiong Ni ◽  
Yanru Li ◽  
Yan Long ◽  
...  
Keyword(s):  
Thermogravimetric Analysis ◽  
Pinus Sylvestris ◽  
Heating Rate ◽  
Industrial Applications ◽  
High Heating Rate ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Model Free ◽  
Different Temperatures

Thermogravimetric analyses of Pinus sylvestris from Xinxiang were performed to investigate its kinetic characteristics, which could provide information for industrial applications. Thermal degradation experiments were conducted at various heating rates of 10 °C/min, 20 °C/min, and 60 °C/min using a thermogravimetric analysis-differential scanning calorimetry (TG-DSC) analyzer with an inert environment. The peak pyrolysis temperatures of the three major components (hemicellulose, cellulose, and lignin) were predicted by the Kissinger-Kai method, and activation energy values (Eα) were calculated. The Eα of Pinus sylvestris was also estimated by two model-free methods. The decomposition reactions of hemicellulose, cellulose, and lignin at different temperatures were the main reason for fluctuations in Eα. The time for heat transfer was less sufficient at a high heating rate compared with that at a low heating rate, which caused the temperature gradients in the samples. Therefore, the temperature of maximum exothermic peaks was higher than the maximum pyrolysis temperature. This kinetic study could be useful for providing guidance for optimizing the biomass pyrolysis process.

scholarly journals Utilization of liquid product through pyrolysis of LDPE and C/LDPE as commercial wax

2021 ◽  
Author(s):  
Hasret Akgün ◽  
Ece Yapıcı ◽  
Zerrin Günkaya ◽  
AYSUN ÖZKAN ◽  
Müfide Banar
Keyword(s):  
Heating Rate ◽  
Liquid Product ◽  
Product Yield ◽  
Effect Of Temperature ◽  
Heating Rates ◽  
H Nmr ◽  
Elemental Analyses ◽  
Liquid Products ◽  
Different Temperatures ◽  
Ft Ir

Abstract Background In this study, pyrolysis of low-density polyethylene (LDPE) and LDPE with aluminum (C/LDPE) wastes was carried out with different heating rates (5-10-20°C/min) at different temperatures (400-600-800°C). The effect of temperature and heating rate on liquid product yield was investigated. Product yields of LDPE and C/LDPE wastes were compared, and optimum liquid products were analyzed to utilize as commercial waxes for future use. Methods To determine the parameters of pyrolysis wastes was investigated with proximate, elemental analysis, and TGA. The as-produced liquid from pyrolysis of wastes was characterized by different characteristic tools, such as elemental analyses, GC-MS analyzes, 1H-NMR tests, FT-IR spectra, the density, melting point, and carbon residue to compare commercial waxes. The characterization process was continued for the parameters with the optimum liquid products. Results As a result of pyrolysis, the highest liquid product yield was achieved at 800°C with 5°C/min heating rate (85.87 %), and at 600°C with 5°C/min heating rate (71.3 %) for LDPE and C/LDPE, respectively. The results indicated that the derived liquid products are similar to commercial heavy wax.

scholarly journals Analysis of heat transfer and irreversibility of organic rankine cycle evaporator for selecting working fluid and operating conditions

2020 ◽  
Vol 24 (3 Part B) ◽  
pp. 2013-2022
Author(s):  
Shuang Ye ◽  
Yan Xu ◽  
Yu Chen ◽  
Wei Huang
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Thermal Resistance ◽  
Heat Transfer Performance ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Transfer Performance ◽  
Irreversible Loss

Organic Rankine cycle (ORC) is suitable to converting the normally hard to utilize low temperature thermal energies, such as geothermal energy, solar energy, and industrial waste heat, to electricity through utilizing low boiling organic working fluids. The performance of ORC system is dramatically affected by the selections of working fluid and working conditions. As a key component of waste heat recovery, the irreversible loss of evaporator also has great influence on the performance of ORC system. In this paper, we study the heat transfer performance in evaporator under the condition that the heat source parameters and pinch point temperature difference are identified. It is found that the heat transfer performance is affected by Cr, the ratio of heat capacity flow rates between the working fluid and the heat source fluid. The equivalent thermal resistance, deducing from the concept of entransy, to measure the irreversability during the heat transfer process is used. Then, the parameter ?r, the ratio between latent heat and sensible heat of working fluid is defined. With the parameters Cr and ?r, we investigate the relationship between the heat transfer and irreversible loss, and deduce the condition that maximum heat transfer and minimum equivalent thermal resistance occurs. Finally, a calculation method is established to choose the optimum working fluid and the evaporation condition.

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