The term 'mean radiant temperature' is used in Section A1 of the CIBSE Guide in connection with thermal comfort, and in Section A5 in connection with the thermal response of an enclosure. With one amendment, the argument of Section A1 is correct but those of Section A5 are flawed and incomplete. This Note draws attention to the need for three separate measures of radiant temperature in a room: the local value Trp (potentially observable), its space-averaged value (Trv), and the radiant star temperature Trs. ('Mean radiant temperature' might refer to any of these.) A study of room radiant exchange requires explicit consideration of the role of surface emissivity, and of the effect of long-wave energy flow from an internal heat source. It is pointed out that the conductances associated with this exchange (and also the convective exchange) are 'large', while the radiant and convective conductances associated with comfort temperature are 'small'.
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References
1.
CibseGuide Volume A: Design Data (London: Chartered Institution of Building Services Engineers) (1986)
2.
Davies M.G.A thermal circuit for radiant exchangeBuilding and Environ.1443-46 (1979)
3.
Davies M.G.Design models to handle radiative and convective exchange in a room Trans . Amer. Soc. Heating Refrig. Air-cond. Eng.94(2) 173-195 (1989)
