Good Thermal Homogeneity Research Articles

A Numerical Analysis of Radio Frequency Heating of Coal With Different Ranks

AbstractRadio frequency (RF) heating is a novel thermal stimulation method in developing coalbed methane (CBM). Various research has been conducted on the effect of electromagnetic (EM) heating on the physical properties of coal. However, few studies considered the working conditions of underground coal seam heating. This paper calculates the coal seam temperature distribution based on the coupling between electromagnetic wave propagation and heat transfer in a vertical well to study the influence of coal seam metamorphism and thermoelectric characteristics on temperature distribution. The reservoir thermophysical parameters related to temperature are considered in the heat transfer and wave equations, respectively. Numerical simulations reveal the influence of coal ranks and thermo-electrical properties on heating efficacy. Results indicate that the temperature in the vicinity of the RF heater is relatively high, and the whole heated zone forms an elliptical shape. Low-metamorphism coal, such as lignite, is more functional for RF heating and has a broad heating range, leading to a uniform diffusion coefficient enhancement and good thermal homogeneity. Higher thermal conductivity, lower specific heat capacity, and water saturation can expand the heating area and reduce the temperature near the borehole, benefiting the maintenance of wellbore integrity. The coal seam relative permittivity has little effect on the reservoir temperature when its value is between 2.4 and 6.4.

Effect of in‐row cooling units numbers/locations on thermal and energy management of data centers servers

The current research investigates the effects of numbers and arrangements of the cooling units on the thermal and energy management of in-row cooling architectures of data centers. Three different configurations with different numbers of cooling units; namely one rack between each two cooling units (Configuration A), two racks between each two cooling units (Configuration B), and three racks between each two cooling units (Configuration C), are numerically investigated. A scaled physical module of data center rack is experimentally constructed and tested for model validation. Two thermal evaluation indices (Supply Heat Index SHI and Index of Mixing IOM) and two energy efficiency metrics (Beta Index β and Energy Utilization Index ηr) are used to investigate, evaluate, and compare the thermal management and energy efficiency of the three configurations. The results show that the three configurations have good thermal homogeneity and the same good values of the thermal and energy efficiency metrics at the intermediate racks. However, problems of hot air circulations with hot spots and bad performances indices were noticed at terminal racks of the racks array. The energy utilization index is in the optimal range (about 2) for the intermediate rack and drop to 1.5 for the terminal racks. Economic study shows that configuration B has the minimum capital cost and configuration A has the minimum needed white area with a capital cost very close to that of B. Accordingly, configuration B is economically recommended, and configuration A is recommended for limited white area.

Near real-time estimation of Sea and Land surface temperature for MSG SEVIRI sensors

Land and Sea Surface Temperatures (LST and SST) are both recognized as Essential Climate Variables, and are routinely retrieved by a wealth of satellites. However, for validated approaches, the latest data are usually not available to the general public. We offer to bridge this gap, by using Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI), with its 15 min temporal resolution. Here, we present generic algorithms for the retrieval of both LST and SST, valid for the SEVIRI instrument onboard MSG platforms 8–11, which we validate using hourly data of 4 ground stations and 11 buoys in Spain over the years 2015 to 2018. These validations show that in the best conditions of surface homogeneity (cloud-free summer nights), errors in our LST estimation are below 1.5 K for stations with good thermal homogeneity. Comparison with LSA-SAF (Land Surface Analysis - Satellite Application Facility) LST shows differences below 2 K for most of SEVIRI disk, with higher differences in arid areas and during daytime. As for SST retrieval, the average error amount to 0.67 K for cloud-free buoy data. These algorithms have been implemented in a near-real time processing chain, which provide actualized LST and SST maps every 15 min within 5 min of image reception. These maps, along with other products, can be freely consulted from a dedicated webpage (https://www.uv.es/iplsat).

Development of low cost tubular furnaces for Research & Development Laboratories

In order to contribute with the most diverse research and development laboratories in its experiments, this paper presents the development methods for the construction of electric furnaces able to operate at temperatures up to 1200oC, with high thermal inertia and low cost. Research and development laboratories in Latin America face many difficulties in maintaining their experiments, especially those related to the synthesis of materials. However, many labs do not have the philosophical tradition of building their own research equipment, depending on whether importing or buying expensive equipment. In this article, we demonstrate the possibility of developing furnaces with good thermal homogeneity using low cost materials found throughout Latin America. Finally, we describe the construction methods and the materials used in the construction of two different furnaces operating at temperatures up to 400oC and 1200oC, presenting very good thermal inertia and homogeneity. With an operational temperature up to 1200 oC, both furnaces have thermal inertia and homogeneity.

On the importance of telemetric temperature sensor location during intraperitoneal implantation in rats

This study aims to assess the thermal homogeneity of the intraperitoneal (IP) cavity and the relevance of using a fixed telemetric temperature sensor at a given location in studying rodents. Ten rats were intraperitoneally implanted with three Jonah® capsules each; after assessing the accuracy and reliability of the sensors. Two capsules were attached, one to the right iliac fossa (RIF) and the other to the left hypochondrium (LH), and another was placed between the intestines but not attached (Free). In the ex vivo condition, the differences between sensors and reference values remained in the range of ±0.1. In the invivo condition, each sensor enabled the observation of temperature patterns. However, sensor location affected mean and median temperature values while the rats were moving freely. Indeed, temperature data collected in the LH were 0.1 significantly higher than those collected in the RIF and temperature data collected in the LH were 0.11 significantly higher than those collected with the Free capsules. In invivo conditions, intra-sensor variability of temperature data was not affected by sensor location. Taking into account sensor accuracy, similar intra-sensor variability, and mean differences observed between the three locations, the impact of sensor location within the IP cavity could be considered negligible. In invivo conditions, temperature differences between locations regularly exceeded ±0.2 and reached up to 2.5. These extreme values could be explained by behavioral factors such as food or water intake. Finally, considering the good thermal homogeneity of the IP cavity and possible adverse consequences of sensor attachment, it seems better to let sensors range free within the cavity.

Electro-thermal simulation and characterization of preconcentration membranes

We use electro-thermal simulations to design thermally insulated membranes that support thin film heaters as components of gas preconcentrators. These heaters provide a good thermal homogeneity ensuring a narrow desorption peak and, thus, a good sensor response. Temperature measurements have been carried out using an infrared camera and they are in agreement with the corresponding numerical predictions. Our model has been validated and it can be used in future designs.

Design of an ohmic reactor to study the kinetics of thermal reactions in liquid products

An ohmic reactor was developed at a laboratory-scale to study the kinetics of thermal reactions in liquid products such as milk and infant formula in the UHT domain. Temperature mapping revealed good thermal homogeneity with a maximum difference of 3 °C in the treatment cell. The ohmic reactor enabled determination of the electrical conductivity of the product under the real thermal conditions with a precision of ±15%. Reproducible thermal profiles were obtained with a 2.3% relative variation for the heating phase, 1% for holding and 20% for cooling. The FAST index, giving a global measurement of the extent of the Maillard reaction in dairy products, was used to estimate the reproducibility of a thermal reaction with an average standard deviation of 3.8%. Finally, a semi-empirical model was developed to predict product temperature history during a complete thermal treatment with good adjustment for heating and holding and acceptable adjustment for cooling.

Electro-thermal simulation and characterization of preconcentration membranes

Preconcentrators have been much studied last years to enhance sensitivity of gas sensors. We use electro-thermal simulations to design thermal isolated membranes that supports thin film heaters as components of gas preconcentrators, these heaters provide a good thermal homogeneity ensuring a narrow desorption peak and improving in this way the sensors response. We have validated our simulations with experimental results.

Thermal conductivity measurements of polarized liquid [formula omitted]He

We present preliminary measurements of the thermal conductivity of spin-polarized normal liquid 3 He. Our experimental apparatus allows good thermal homogeneity of the 3 He as well as high sensitivity to the 3 He conductivity. Initial measurements show the conductivity changes by <10% for polarizations up to 70%.

Traitement des carcinoses péritonéales par exérèse complète et chimiohyperthermie intrapéritonéale. Étude de phase I–II permettant de définir la meilleure procédure technique

Objectives The complete or quasi complete resection of peritoneal carcinomatosis (PC) followed with IPCH is potentially able to cure some patients with a disease confined to the peritoneum. The aim of this prospective phase I-II study was to elaborate an efficient IPCH procedure with a good thermal homogeneity and a good spatial diffusion, which should be reproductible (and so standardizable and exportable), and to appreciate its tolerance and its carcinologic impact. Patients and methods Seven IPCH procedures were successively tested in 32 patients (for a total of 35 IPCH); each of these were tested in at least four patients before being modified for technical or tolerance reason. Five of them were followed with an immediate postoperative intraperitoneal chemotherapy (IPIC) lasting four days. Thermal homogeneity was measured with six thermal probes situated in different places inside the abdominal cavity. Spatial diffusion was studied in the last patients by adding methylene blue in the IPCH liquid. The precise extent of the PC was reported, for each intra-abdominal region, and scored with a peritoneal index (ranging from 1 to 39). The mean follow-up was 23.85 months for the series. Results Procedures with the closure of the abdomen were not efficient: thermal homogeneity was almost satisfactory when only the skin was closed, but these ‘closed’ procedures did not permit the treatment of all the risky surfaces. The peritoneal cavity ‘expander’ did not permit the treatment of the parietal wound, and an undetermined amount of the perfusion oozed out at its periphery. The open technique by tracking the skin upwards was the best one. Death occurred in three patients (9.4%), and complications occurred in 24 patients (75%) during the postoperative course. Intra-abdominal complications were significantly correlated ( P = 0.02) with the peritoneal index (scoring the extent of the PC). The two year survival rate was 60%, and PC did not recur in 50% of the patients. Conclusion An efficient and reproducible procedure for IPCH was defined: an open procedure with an upwards traction of the skin. The post-IPCH IPIC was abandoned because it did not treat all the risky peritoneal surfaces. Patients with an extended PC and with extraperitoneal localization did not seem to have benefited from this therapeutic approach. Progress is needed in the chemotherapeutical procedure and indications must be more finely defined.

Thermodynamic measurement of the magnetization curve of liquid 3He up to 200 Tesla

The study of spin polarised liquid 3He provides new insight in the physics of Fermi liquids. The rapid melting technique offers a way to obtain transiently strongly polarised liquid 3He. We have improved this technique by melting the solid in a silver sinter. This opens the way to experiments on highly polarised liquid (up to 70%) at low temperatures (<100 mK). The use of this sinter results in a good thermal homogeneity of the sample. We applied our technique to measure the magnetisation curve up to fields as large as 200 T, providing essential information on the magnetism of this Fermi liquid. Other possible experiments are briefly discussed.

Sample cell to measure the electromigration of tritium in metals

The features of a cell with which the electromigration of tritium in metals can be conveniently measured are described. The concentration profile due to the electromigration is monitored by a resistometric technique. The main requirements incorporated in the design of the cell are good thermal homogeneity and stability around the specimens, possibility of housing many samples in one run so as to generate more data during the long waiting times, and the safe containment of the radioactive tritiated samples. The cell has been used up to 300 °C. Results on the electromigration of tritium in niobium are presented to demonstrate the cell performance.