Implementation of a Water Heat Pipe at CETIAT

Measurement, 2020

Gas-Controlled Heat Pipes (GCHPs) are devices based on generating and maintaining, at millikelvin level, a thermodynamic liquid-vapour equilibrium of a fluid. For this reason, GCHPs have been studied for more than thirty years for research and applications in thermal metrology. Capabilities have been constantly improved and adapted by National Metrology Institutes (NMIs) and accredited laboratories. Activities include study of vapour pressure curves of pure elements and substances, thermometers' nonuniqueness up to 960°C, calibrations between À20°C and 900°C with millikelvin uncertainties, studies of innovative pressure controllers allowing regulation better than 10 À6 from below 1000 Pa up to 400 kPa. GCHPs operating at different temperature ranges have also been connected to a common pressure line in the so-called ''Temperature Amplifier" configuration. This review paper presents an almost complete report about the several models of GCHPs, materials and working fluids, techniques adopted in different temperature/pressure ranges. All involved NMIs using GCHP are here included, with detailed bibliography.

2020

Article Info Abstract Article History: Received May 19, 2020 Revised July 14, 2020 Accepted July 21, 2020 Uneven temperature distribution in the water-bath chamber can cause the temperature conditions in the chamber are not the same. Temperature, humidity, atmospheric pressure, and dust particles are the main factors that adversely affect the accuracy of the water bath's temperature. Therefore, the purpose of this study is to design a calibration device for water-bath with six-channel temperature sensors. In this study, the system able to detect temperatures at each point. The K-type thermocouple sensor is used to detect the temperature at each chamber point with the help of the MAX6675 module as a signal conditioning amplifier. The sensor readings will be displayed on a personal computer using a USB cable, and the sensor readings can be stored on a personal computer in the TXT format so that the data can be reprocessed using Microsoft Excel for further calibration purposes. Thi...

Metrologia, 1994

A new primary humidity generator was developed at the National Standards Authority of Ireland (NSAI). The principles of operation and overall design of the generator are discussed. The flow regime within the saturators was analysed using computational fluid dynamics (CFD) to determine if sufficient mixing takes place within the final saturator. This was later investigated by experiment and it was found that sufficient mixing takes place for flow rates up to 3 l min −1 at standard flow conditions of 101 325 Pa and 293.15 K. The uncertainty due to nonideal saturation at 90 °C dp is discussed. This uncertainty was analysed with respect to the effect that the flow speed and latent heating in the saturators has on the saturation efficiency, separately. The uncertainty associated with saturation efficiency at 90 °C dew point was estimated from the temperature gradients along the saturation path arising due to latent heating effects. The standard uncertainty due to nonideal saturation was found to be ±3 mK dp.

2019

Calibration is one area in measurement where our country is still in the process of improvement. The absence of confirmed approaches and actions for identifying the features of calibration baths by numerous laboratories disallowed them to assess more the finest measurement ability and develop their accurateness. In recent advances in technology, there is now a way of providing the best measurement capability in temperature calibration by providing validated methods in characterizing calibration baths that contributes to the uncertainty of measurement of the calibrated thermometer and is therefore important to measure the extent of its contribution to the final uncertainty. This study adapted the process from obtainable and current methods. Platinum Resistance Thermometer (PRT-Isotech) and Standard Platinum Resistance Thermometer (SPRT-Hart) which are interfaced to Precision Digital Multimeters were used for measurements. Quite a few measurements were made at varying time durations i...

Hydrological Processes, 2005

Thermochron iButtons incorporate the latest in digital technology, making them smaller, less expensive, durable and potentially more reliable than many other temperature logging devices. The objective of this study was to test the accuracy of an inexpensive air temperature measurement system, composed of a Thermochron iButton and radiation shield. Sixty-one iButtons were subjected to a sequence of two water baths (0°C and 24·9°C) to assess the absolute accuracy of the sensors. Five solar radiation shields were tested in a greenhouse setting to evaluate the reduction in radiative heating. Significant differences (p < 0·05) were detected between instruments subsequent to both water-bath treatment analyses. The accuracy of the sensors was well within the manufacturer's stated specification of ±1·0°C with a collective temperature variance of ±0·21°C. Temperature responses generated by the Thermochron iButtons in different radiation shields were consistent, but varied significantly (p < 0·05) from 28 to 44°C based on diurnal temperature ranges. Results indicate that the Thermochron iButton is an accurate, inexpensive alternative to more expensive temperature datalogging systems, and is well suited for obtaining quality spatially distributed data for hydrologic and water quality investigations.

Physiological Measurement, 2011

We determined the validity and reliability of heat flow thermistors, flexible thermocouple probes and general purpose thermistors compared with a calibrated reference thermometer in a stirred water bath. Validity (bias) was defined as the difference between the observed and criterion values, and reliability as the repeatability (standard deviation or typical error) of measurement. Data were logged every 5 s for 10 min at water temperatures of 14, 26 and 38 • C for ten heat flow thermistors and 24 general purpose thermistors, and at 35, 38 and 41 • C for eight flexible thermocouple probes. Statistical analyses were conducted using spreadsheets for validity and reliability, where an acceptable bias was set at ±0.1 • C. None of the heat flow thermistors, 17% of the flexible thermocouple probes and 71% of the general purpose thermistors met the validity criterion for temperature. The interprobe reliabilities were 0.03 • C for heat flow thermistors, 0.04 • C for flexible thermocouple probes and 0.09 • C for general purpose thermistors. The within trial intra-probe reliability of all three temperature probes was 0.01 • C. The results suggest that these temperature sensors should be calibrated individually before use at relevant temperatures and the raw data corrected using individual linear regression equations.

2017

This paper reports the results of measurements performed on a digital thermohygrometer by several metrology laboratories throughout Romania. The comparison began in 2013 and concluded in 2014. Temperature Laboratory of National Institute of Metrology (INM) acted as pilot laboratory (PL) and reference laboratory (RL) for the programme. The measurements were conducted at temperature integer values in the range of (10…30)º C. The results obtained in this comparison by participating laboratories are used to validate and transmitting traceability measurement according to quality management system.

2016

setup using computational fluid dynamics simulators

Review of Scientific Instruments, 1985