Globe temperature
The globe thermometer was introduced by Vernon in 1930 as a means of assessing the combined effects of radiation, air temperature and air velocity on human comfort.
It consists of a hollow copper sphere painted matt back to absorb radiant heat, with a temperature sensor at its centre. When it reaches a steady state (after 15 minutes or so depending on the size of the globe and the environmental conditions) the heat exchanges by convection and radiation will be in equilibrium, and the temperature recorded by the sensor will be somewhere between the air and radiant temperature. This is referred to as the globe temperature (tg) or black globe temperature and resembles the thermal conditions felt by the human body.
The standard sphere has a diameter of 150 mm. Other sizes do exist, but the smaller the diameter of the globe, the greater the effect of convection on the temperature recorded.
From the temperature recorded, the mean radiant temperature (mrt) in can be calculated:
MRT = tg + 2.42 x air velocity in m/s (globe temperature – air temperature)
(equation ref Novalynx Corporation 2010 - this equation is dependent on the size and emissivity of the globe thermometer, and the units they show for air velocity are incorrect - cm/s, rather than the correct m/s shown above)
Mean radiant temperature is a measure of the average temperature of the surfaces surrounding a body.
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Balfour Beatty fined £500,000 for exposing workers to hand-arm vibration.
James Brokenshire launches a consultation on banning combustible cladding.
A year after Grenfell, we have a collection of 30 articles telling you everything you need to know.
Infrastructure interconnectivity
ICE publish a policy paper on the UK’s future interconnectivity with the EU and the challenges for infrastructure.
Detailed guidance about construction waste management.
The changing identity of London communities in the face of rapid urbanisation.
Can you help? We have 300 industry acronyms beginning with 'C' but none beginning with 'Y'.
From the sinister Carceri d’Invenzione to the triple portrait of Sir Watkin Williams-Wynn and his Grand Tour travelling companions.
Design freeze: a quality perspective
Progressively freezing a design helps ensure it meets the specification when built.
BSRIA launch the 5th edition of the Design Framework for Building Services (BG 6/2018).
Stella Rimmington famously said the construction industry was just as tricky as the KGB.
CSCS
Construction site visitor cards are to be withdrawn.