Measurement of air temperature in the presence of a large radiant flux: an assessment of assively ventilated thermometer screens

Erell, Evyatar; Leal, Vítor; Maldonado, Eduardo

doi:10.1007/s10546-004-8946-8

Cited by 71 publications

(50 citation statements)

References 13 publications

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“…NTC thermistors (MEA model 6507, nominal accuracy 0.2°C) were housed in radiation shields constructed especially for the experiment (Erell and Williamson, 2006). Comparative tests of this type of makeshift instrument shield in conditions of very bright sunlight and low wind against a mechanically aspirated standard, confirmed that it was superior to the conventional Stevenson screen (Erell et al, 2005), which has been shown to produce some error in such conditions (World-Meteorological-Organization, 1971;Sparks, 1972;Andersson and Mathisson, 1992;van der Meulen, 1998). However, error due to radiant load cannot be ruled out entirely when relatively large sensors are used, such as the thermistors employed in this experiment, and deviations of up to 1°C from 'true' air temperature are nonetheless possible.…”

Section: Instrumentationmentioning

confidence: 99%

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

Erell

Williamson

2006

Intl Journal of Climatology

133

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Abstract:Detailed meteorological measurements were carried out in two urban street canyons in central Adelaide and at two reference sites in a suburban location and at an exposed site near the middle of the city for an extended period of nearly a year. The meteorological records revealed substantial differences between air temperature in the urban street canyons and both reference sites. The nocturnal urban heat island observed in most cities was noted in Adelaide street canyons, too. However, the frequent occurrence of a daytime cool island during summer, albeit much weaker than the night-time phenomenon, is less expected. Both phenomena are attributed at least in part to the increase in surface area participating in energy exchanges with the atmosphere in an urban street canyon compared to a typical rural site, and hence in an increase in the effective thermal mass. The presence of additional thermal mass is manifested not only in the dampening of the diurnal temperature range in the city, but also in a noticeable time lag in the maximum intensity of the daytime cool island. The measurements also demonstrate an observable difference in the daily progression of air temperature between a north-south street canyon and an adjacent east-west oriented street.

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Section: Instrumentationmentioning

confidence: 99%

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

Erell

Williamson

2006

Intl Journal of Climatology

133

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“…Erell et al (2005), Richardson et al (1999), have recognized that temperature accuracy improves with decrease in sensor size because the convective heat exchange efficiency improves. This suggests the use of a temperature sensor small enough to maximize ventilation efficiency but durable enough to withstand weather extremes.…”

Section: Introductionmentioning

confidence: 99%

Accurate Temperature Measurements in a Naturally-Aspirated Radiation Shield

Kurzeja

2009

Boundary-Layer Meteorol

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Experiments and calculations were conducted with a 0.13 mm fine wire thermocouple within a naturally-aspirated Gill radiation shield to assess and improve the accuracy of air temperature measurements without the use of mechanical aspiration, wind speed or radiation measurements. It was found that this thermocouple measured the air temperature with root-mean-square errors of 0.35 K within the Gill shield without correction.A linear temperature correction was evaluated based on the difference between the interior plate and thermocouple temperatures. This correction was found to be relatively insensitive to shield design and yielded an error of 0.16 K for combined day and night observations.The correction was reliable in the daytime when the wind speed usually exceeds 1 m s -1 but occasionally performed poorly at night during very light winds. Inspection of the standard deviation in the thermocouple wire temperature identified these periods but did not unambiguously locate the most serious events. However, estimates of sensor accuracy during these periods is complicated by the much larger sampling volume of the mechanically-aspirated sensor compared with the naturally-aspirated sensor and the presence of significant near surface temperature gradients. The root-mean-square errors therefore are upper limits to the aspiration error since they include intrinsic sensor differences and intermittent volume sampling differences.

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“…Various shapes of solar radiation shields have been proposed and evaluated (Peon et al, 1998;Ma et al, 2004;Erell et al, 2005). In this study, five shapes of solar radiation shields were chosen to be compared with the fan-aspirated radiation shield.…”

Section: Solar Radiation Shields To Compare With the Fan-aspirated Ramentioning

confidence: 99%

“…Many studies have been carried out on the performance of these solar radiation shields. Erell et al (2005) compared several shapes of radiation shields and reported that the high airflow and small surface of sensor tip reduce the measuring error. A technique to block the solar radiation and generate airflow for the sensor tip is known as the Asman psychrometer.…”

Section: Introductionmentioning

confidence: 99%

Effects of Fan-Aspirated Radiation Shield for Temperature Measurement in Greenhouse Environment

Yang¹,

Lee²,

Kim³

et al. 2012

Journal of Biosystems Engineering

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Purpose: Provision of accurate temperature measurement is an essential element to ensure a precise control in greenhouse environment. This study was organized to compare the effects of six solar radiation shields with different shapes for temperature measurement and find the most appropriate shield for greenhouse environment. Methods: A fan-aspirated radiation shield was designed and manufactured. Using the fan-aspirated radiation shield and five other shapes i.e., the cup shape, horizontal pipe, vertical pipe, parallel boards and commercial shields, temperature measurement was conducted over the lawn surface as well as greenhouse indoor environment. The measurement height varied at 0.5, 1.0 and 1.5 m from the floor. Results: The measured temperatures by the fan-aspirated radiation shield were 1.30-1.49℃ lower than the values recorded by other different-shaped shields at 1.5 m of measurement height. As the measurement height decreases, observed differences between measured temperatures of the fan-aspirated radiation shield and other shields demonstrate a declining trend. However, at low measurement heights, the radiation emitted from the bottom surface would be the source of error in temperature measurement. Conclusions: The fan-aspirated radiation shield is a required tool for exact measurement of air temperature in greenhouse temperature control.

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Measurement of air temperature in the presence of a large radiant flux: an assessment of assively ventilated thermometer screens

Cited by 71 publications

References 13 publications

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

Intra‐urban differences in canopy layer air temperature at a mid‐latitude city

Accurate Temperature Measurements in a Naturally-Aspirated Radiation Shield

Effects of Fan-Aspirated Radiation Shield for Temperature Measurement in Greenhouse Environment

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