Steady-state Apparatus Research Articles

Manufacture and Design an Apparatus for Measuring the Thermal Resistance of Building Materials

A good thermal design of buildings plays a key role in reducing the thermal loads of heating and air conditioning systems and thus reducing energy consumption. This study develops a steady-state apparatus for measuring the thermal resistance of building materials by using an absolute technique. The apparatus is designed to accommodate the full and actual size of the tested samples of building materials used in the Syrian market to ease testing. Therefore, suitable samples do not have to be built for the apparatus; the thermal resistance is measured for many samples, and the results are compared with the thermal insulation code for buildings in the Syrian Arab Republic. The results show that the difference between the resistance values obtained from the experiments and the Syrian thermal insulation code is due to the materials used in the local markets and their non-compliance with the code. These materials need testing and quality control during the manufacturing process.

Determination on the thermal conductivity and thermal contact resistance of thin composite phase change films as a thermal interfacial material

Sub-millimeter thick phase change material (PCM) composites have been utilized in the thermal management of micro-electronics serving as a novel thermal interfacial material. However, there is a lack of appropriate measuring methods and precise data for the thin-film PCM composites' intrinsic thermal conductivity, as well as the thermal contact resistance (TCR) at interfaces between those thin-films and metal. In this work, the out-of-plane thermal conductivity of thin-film PCM35, which is a paraffin composite showing the melting point of 35 °C, was first gauged through the commercialized transient plane source (TPS) method, followed by a correction process to deduct the TCR between thin films/temperature sensor interfaces. The direct TPS readings were corrected based on the proportional relation between samples’ thickness and inherent thermal resistance. An improved steady-state heat flow apparatus designed for thin-walled samples was then utilized to examine the reliability of the corrected TPS technique, with a relative deviation between them being only ∼7%. In order to test the applicability of the corrected TPS method, the thermal conductivities of thin polytetrafluoroethylene films were also determined. Furthermore, the TCR between thin PCM35 film and thin 1060Al plate was identified by performing the improved steady-state apparatus. The contribution of overheated PCM35 film on fitting the interfacial voids and reducing the TCR were elucidated, which can guide the thermal design with the use of such thin-film PCMs.

Correlating the thermal contact resistance between metal/erythritol interfaces with surface roughness and contact pressure

The thermal contact resistance (TCR) between the interfaces of phase change materials (PCMs) and their encapsulation materials, usually thin-walled metals, have a great impact on the heat storage/retrieval rates of PCM-based latent heat storage (LHS) systems. However, the TCR data beteween metal/PCM interfaces are rarely reported in the literature. In this work, an improved self-designed steady-state apparatus was adopted to measure the TCR between the interfaces of erythritol, a cost-effective sugar alcohol with great potential for medium-temperature LHS, and multiple metals including SS304, nickel silver (a copper-nickel-zinc ternary alloy), and 1060 Al. The metal/erythritol composites were prepared by naturally solidifying molten erythritol on the surface of thin metal plates. The variation of the TCR between metal/erythritol interfaces was measured as a function of the surface roughness (of the metal plates) and the contact pressure applied (between the interfaces). With the decrease of surface roughness, the TCR also decreases due to the better contact between the interfaces as observed by a microscope. Comparing to SS304 and nickel silver, the 1060 Al/erythritol composites exhibit a significant reduction of TCR by ~40% when rising the contact pressure from 0 MPa to 7 MPa, for all surface roughness levels tested. The in situ measured sample thickness variations confirmed that upon pressurization, the softer metal, i.e., 1060 Al, experiences more micro-deformation at the interface. In addition, correlations of the TCR data between metal/erthyritol interfaces were proposed with the surface roughness and contact pressure. The results and correlations attained in this work could serve as a reference for the thermal design of LHS units using erythritol.

Evaluation of Thermal Conductivity of Polyimide Foam for Space -Development of Simple and Small Steady State Apparatus using Heat Flow Separation Method and Numerical Analysis using Monte Carlo Method-

Evaluation of Thermal Conductivity of Polyimide Foam for Space -Development of Simple and Small Steady State Apparatus using Heat Flow Separation Method and Numerical Analysis using Monte Carlo Method-

Design and construction of a new steady-state apparatus for medium thermal conductivity measurement at high temperature.

A new steady-state apparatus is designed and constructed for the measurement of thermal conductivity (up to 25 W/mK) on a square specimen (300 mm side) with a heating temperature range from 30 °C to 900 °C. A vacuum container, of which the pressure can reach to 1 Pa, is also built for materials which can be easily oxidized. The structure of the facility is different from that of traditional steady-state devices, especially for the design of heating plate and heat sink. To verify the temperature uniformity of the heating plate, a simulation analysis is carried out in this paper. Besides, the heating system, the heat sink, the measuring system, and the vacuum system are presented in detail. In addition, the thermal conductivities of a heat insulation tile, 304L stainless steel, n-docosane, and erythritol are measured by this apparatus. Finally, an uncertainty analysis is discussed depending on different temperatures and materials.

Thermal conductivity of a sandy soil

The thermal properties of soils are of great importance in many thermo-active ground structures such as energy piles and borehole heat exchangers. In this paper the effect of the porosity and degree of saturation on the thermal conductivity of a sandy soil that has not been previously thermally tested is investigated using steady state experimental tests. The steady state apparatus used in these tests was designed to provide high performance in controlling all boundary conditions. Twenty thermal conductivity experimental tests have been carried out at different porosity and saturation values. The performance of selected prediction methods have been validated against the experimental results. The validation shows that none of the selected models can be used effectively in predicting the thermal conductivity of Tripoli sand at all porosity and saturation values. However, some can provide good agreement at dry or nearly dry condition while others perform well at high saturations. The performance of most of the selected models also increases as the soil approaches a two phase state where conduction plays the dominant role in controlling heat transfer. An empirical equation of thermal conductivity expressed as a function of water content and porosity has been developed based on the experimental results obtained.

Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation.

Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm.

An improved steady-state apparatus for measuring thermal conductivity of soils

The thermal conductivity of soil is among the most critical parameters required to design ground heat exchangers, which are widely used as a renewable technology for providing heating and cooling for buildings. This paper describes the development of new test apparatus that can be used for soil specimens obtained from routine site investigation as well as reconstituted specimens. The design of the apparatus is based on the application of Fourier’s law where one directional uniform heat flux is generated through two identical specimens, producing a measurable temperature gradient that is used to calculate the thermal conductivity of the specimen. A new concept of minimizing the radial heat losses using a thermal jacket as a heat insulation barrier was examined. It was found that the no-radial heat losses condition can be achieved with thermal jacket temperature approximately equal to the average value of the ambient temperature and average specimen temperature. All parameters that can affect the measurements have been tested and the results showed a good performance with margin of error upto 5%. An application of the new test procedures involved conducting several experimental tests on undisturbed and reconstituted soil samples highlighted the simplicity of this apparatus in measuring thermal conductivity of soil under different conditions.

Thermal Conductivity of Cobalt-Based Catalyst for Fischer–Tropsch Synthesis

In this study, the thermal conductivity of cobalt-based catalyst specimens in the temperature range from 160 ◦C to 255 ◦C are measured via a steady-state apparatus. The apparatus and procedures are applied to several specimens of cobalt-based catalyst powder compacts. Specimens with different degrees of porosity are produced by pressing cobalt-based catalyst powder with a particle size of (80 to 360) mesh. The thermal conductivity of cobalt-based catalyst powder compacts is investigated as functions of temperature, specimen density, porosity, and powder size. The results indicate that the thermal conductivity of the catalyst specimens increases linearly with temperature and density and is practically independent of the particle size of the powder in an atmosphere of air, while the porosity dependence of the thermal conductivity is inverse to that of density. In addition, the effects of some measuring factors on the thermal conductivity show that the reliability of the thermal conductivity measurements of cobalt-based catalyst specimens are influenced easily by parallelism, specimen roughness, and moisture content, whereas the specimen thickness and water bath temperature have only a slight effect on the reliability.

A Steady-State Apparatus to Measure the Thermal Conductivity of Solids

This paper presents a steady-state apparatus to measure the thermal conductivity of solids based on the use of heat flux sensors. The uncertainty assessment of the experimental apparatus is performed in accordance with the ISO “Guide to the Expression of Uncertainty in Measurement” (GUM): the combined standard uncertainty (k = 1) with reference to the properties of Pyrex Glass CRM 039 at 20°C is ±1.9%. The standard uncertainty has also been assessed in the measurement range from 0.1 to 10W · m−1 · K−1. The experimental apparatus has been used to measure the certified reference material Pyrex Glass CRM 039 in the temperature range from 3.1 to 60.3°C: the standard deviation (k = 1) between the experimental measurements and the certified values is ±1.1% with a maximum deviation of 2.4%. Reasonable agreement is found between the uncertainty assessment and the experimental validation.

A route to MFI zeolite-α-alumina composite membranes for separation of light paraffins

Zeolites are microporous crystalline materials used as catalysts, ion-exchangers, adsorbents and molecular sieves. Several industrial separation processes, e.g. dehydration of alcohols, have been developed based on zeolite membranes. It is also of great interest the separation of light paraffins. Silicalite-1 crystal layers were synthesised on the surface of asymmetric α-alumina planar supports. A molar ratio of synthesis mixture was 100 SiO 2:42.9 TPAOH: 2229 H2O with Aerosil 380 (Degussa) used as a silica source. Permeation and separation characteristics of the membranes were measured using steady state apparatus MEMFIS. Separation factor of ceramic silicalite-1 composite membrane, which was synthesised for 24 h using a synthesis mixture aged for 7 days, was studied by an equimolar mixture of butane isomers as a function of temperature. High separation factor for n-butane (>10) in the mixture with isobutane showed good quality of the composite membrane. The results showed that the separation performance of the membrane could be tailored to find suitable compromise between permeation and separation.

A modified steady state apparatus for thermal conductivity measurements of liquid metals and semiconductors

An experimental arrangement based on the steady-state concentric cylinder method has been developed for the measurement of the thermal conductivity of liquid metal and semiconductor alloys over a wide temperature range (up to 1700 K) under ambient pressures of argon gas (up to 1 MPa). Particular attention has been paid to minimization of heat leakage and convection heat flows. The various experimental errors are analysed. Thermal conductivity data for molten Pb, Sn and the semiconducting alloy TlAsTe2 are reported.

Dehydration of mature and immature sickle red blood cells during fast oxygenation/deoxygenation cycles: role of KCl cotransport and extracellular calcium

AbstractSickle red blood cells (RBC) become dehydrated as a consequence of potassium loss. This process depends at least partly on deoxygenation and may be influenced by the presence of oxygenation/deoxygenation cycles and the frequency of cycling. In this study, sickle RBC were subjected to approximately 180 oxygenation/deoxygenation cycles during 4 hours to evaluate RBC dehydration with cycle periods more similar to in vivo cycles than those in previous studies. A continuous-flow, steady-state apparatus circulated a dilute RBC suspension through gas-permeable silicone tubing with segments that were exposed to either nitrogen or ambient oxygen. The percentage of sickling and partial pressure of oxygen were measured by means of sampling ports in the deoxygenation and oxygenation regions. The density increase (dehydration) of young (transferrin receptor-positive) and mature (transferrin receptor-negative) RBC and the requirements for calcium and chloride were evaluated. Density increase correlated with the percentage of sickled cells at the deoxygenation sampling port and was observed only in the presence of calcium, thereby implicating the calcium-dependent potassium channel (Gardos pathway). Density increase was not dependent on the presence of chloride, making it unlikely that KCl cotransport was an important pathway under these conditions.

Thermal conductivity of packed beds consisting of porous particles wetted with binary mixtures

The thermal conductivity of particles wetted with a binary mixture and packed beds of such particles has been investigated both theoretically and experimentally. The model of Zehner and Bauer has been used to combine the conductivites of the (wetted) pores and the solid matrix to provide an effective thermal conductivity for the particle as well as to predict the effective conductivity of the packed bed. The latter is obtained both from the conductivity of the single particles and from the conductivity of the moist gas in the cavities, the additional transport of energy via the evaporation and recondensation of the vapours of both components being taken into account through the introduction of an equivalent thermal conductivity. Two different techniques have been employed in the experimental investigations. The thermal conductivities of single particles were obtained by means of a transient method, in contrast to the conductivities of fixed beds which were measured in a steady-state apparatus. By fitting two unknown parameters to the results for the single particles, a good prediction of the thermal conductivities of packed beds was obtained showing a strong temperature dependence in the case of wet particles.

Incorporation of 14CO2 in photosynthetic pigments of Chlorella pyrenoidosa

Tracer kinetic studies of chloroplast pigments of Chlorella pyrenoidosa were carried out in a special steady-state apparatus which allowed the simultaneous recording of oxygen evolution, CO2-fixation and (14)CO2-incorporation. A special cylindrical vessel which permits labeling experiments with larger algae suspensions (800 ml) is described.-1. After 2 h of (14)CO2-photosynthesis (fixation rate 100-160 μmol CO2/μmol chlorophyllxh) 3.3% of the total (14)C-uptake (5.66 mCi) was found in the Chlorella lipid fraction. Total and specific radioactivity were higher in total carotenoids than in the chlorophylls. Chlorophyll a gave a higher labeling degree (2.4%) than chlorophyll b (1.3%).-2. Among the carotenoids α-and β-carotene were labeled after 2 h (14)CO2 exposure with the same specific radioactivity and with a particular high labeling degree of c. 19%. The xanthophylls exhibit lower labeling degree (violaxanthin 5.1%, zeaxanthin 1.9%, lutein 1.4%, antheraxanthin 1.3%, and neoxanthin 0.7%).-3. During the 4 h (12)CO2-exposure period, which followed the 2 h (14)CO2-incorporation time, the specific and total radioactivity of the α-and β-carotene pools decrease with a concomitant increase in the α-ionone-(lutein) and β-ionone xanthophylls (violaxanthin, zeaxanthin, antheraxanthin). The possibility, that the decrease of (14)C label in the carotenes may in part be due to a photo-oxidative degradation, is discussed.-4. Calculation of biological half-life-times from the (14)C-incorporation kinetics during the first hour of the experiment, when the pigment concentration is almost unchanged, results in times from 30 to 60 min. Half lives are shorter in the precursor pools such as chlorophyll a (30 min), α-carotene (40 min) and β-carotene (50 min) and violaxanthin (60 min) respectively.

Analysis of Steady State Photosynthesis in Alfalfa Leaves

A method for carrying out kinetic tracer studies of steady state photosynthesis in whole leaves has been developed. An apparatus that exposes whole leaves to (14)CO(2) under steady state conditions, while allowing individual leaf samples to be removed as a function of time, has been constructed. Labeling data on the incorporation of (14)C into Medicago sativa L. metabolite pools are reported. A carbon dioxide uptake rate of 79 micromoles (14)CO(2) per milligram chlorophyll per hour was observed at a CO(2) level slightly below that of air. Several actively turning over pools of early and intermediate metabolites, including 3-phosphoglyceric acid, glycerate, citrate, and uridine diphosphoglucose, showed label saturation after approximately 10 to 20 minutes of photosynthesis with (14)CO(2) under steady state conditions. Alanine labeling increased more rapidly at first, and then at a lower rate as saturation was approached. Sucrose was a major product of photosynthesis and label saturation of the sucrose pool was not observed. Labeled carbon appeared rapidly in secondary metabolites. The steady state apparatus used has numerous advantages, including leaf temperature control, protection against leaf dehydration, high illumination, known (14)CO(2) specific radioactivity, and provision for control and adjustment of (14)CO(2) concentration. The apparatus allows for experiments of long duration and for sufficient sample points to define clearly the metabolic steady state.

Quantitative tracer studies of metabolic dynamics of animal cells growing in tissue culture

Metabolic dynamics of animal cells, growing in tissue culture, can be determined quantitatively by allowing the cells to metabolize radioactively labeled substrates under carefully controlled steady-state conditions. In order to avoid artifacts resulting from uncontrolled changes in physiological conditions, a steady-state apparatus for animal cells (SAFAC) has been constructed. In this device, cells in culture plates (max of 30) can be given radioactive substrate and incubated for various periods without disturbing the steady-state metabolism prior to killing. Subsequent analysis by two-dimensional paper chromatography and radioautography shows that metabolites are labeled rapidly and thereafter are maintined at constant levels of radioactivity, as expected for steady-state metabolism.

Research Potentials in Auditory Characteristics of Violin Tone

Sensations of tone, including violin tone, come partly from evoked matrices generated within the brain. Cited evidence from electrodes permanently implanted in the brains of conditioned cats shows that an incoming signal evokes generation of temporally patterned recurrences. The cat acts appropriately for the signal when coincidence exists between the input and the internally generated pattern. An adequately functioning nervous system experiences tone from input of regularly repeating waves, such as are compatible with neural temporal recurrence, but human patients with some neural handicaps, including vertebral artery insufficiency, commonly experience noise instead of tone from smooth sine wave input, presumably because of inadequate internal generation or coincidence detection. The normal human nervous system, with many neurons responding only to change, is not a steady-state apparatus, yet it uses temporal recurrence with an appetite for regularity. Human preference for regularity and change can be observed when a master plays a violin which is thus physiologically controlled.

The design of a steady-state gradient for the study of populations in a continuously renewed environment

The design for a steady-state gradient environment to be used in conjunction with a plankton capable of directed movement is given. A dilution of partially digested human waste produced the gradient. The steady-state apparatus is composed of three distinct units: the agent flow system, the dilutant flow system, and the gradient chamber.

Simplified determinations of heat transfer data for solids, applications to quality testing of electrical insulations

The first part of the paper describes a simple steady state apparatus for measuring the thermal conductivity of plates of electrical insulations, plastics, etc. The measurement is quick, requiring approximately 5 min. The apparatus also enables one to determine the thermal capacity of the sample. The second part of the paper describes the k-meter, a new device for measuring the heat transfer coefficient through the insulation on metal bars such as generator coils. The method does not require any access to the inner conductor. The suitability of the k-meter for nondestructive thermal ageing investigations of e.g. generator insulations and for quality control, is demonstrated. In this respect k-value measurements might be a valuable complement to dielectric loss measurements.