CPD Programme
CPD Programme
The CIBSE Journal CPD Programme programme is free and can be used by any
Members of the Chartered Institution of reader. It is organised jointly by CIBSE Journal
Building Services Engineers (CIBSE) and other and London South Bank University, and will
professional bodies are required to maintain help you to meet CIBSE’s requirement for
their professional competence throughout CPD. It will equally assist members of other
their careers. Continuing professional institutions, who should record CPD activities
development (CPD) means the systematic in accordance with their institution’s guidance.
maintenance, improvement and broadening Simply study the module and complete the
of your knowledge and skills, and is therefore questionnaire on the final page, following the
a long-term commitment to enhancing your instructions for its submission. Modules will
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CIBSE and the Register of the Engineering com/cpd while the information they contain
Council (UK). remains current. You can also undertake the
CIBSE Journal is pleased to offer this questionnaire online, and receive your results
module in its CPD Programme. The back by return email.
Radiant heating panels
This CPD article considers the attributes and applications of low-
temperature radiant heating panels as an aid to cutting the carbon dioxide
emissions of buildings
T
he use of radiant heating panels in the centre of the room (°C) and θ
ao
is the radiant fraction, R, with high ventilation
buildings can provide an energy- outside air temperature (°C). coefficient, C (i.e. high air change rate), will
V
efficient and space saving solution, The factors F
1
and F may be obtained reduce the value of the factors F
cu 2cu 1
and F .
cu 2cu
contributing to reduced energy in a from: When high values of R and C are combined
v
building, helping to meet the TER (Target 3(C A) in large volume spaces and particularly for
F
v
+ 6∑
CO Emission Rate) as well as lowering its ∑
1cu
=
(AU) + 18∑A + 1.5R[3C those with relatively small values of ∑(AU)
2 v
+ ∑(AU)]
operational energy use. and (i.e. low U values and/or relatively small
Radiant heating was traditionally ∑(AU) + 18∑A external envelopes compared with the room
F
associated with gas-fired or steam-supplied ∑
2cu
=
(AU) + 18∑A + 1.5R[3C
v
+ ∑(AU)] volume) – there will significantly lower
high-temperature, high-roofed industrial and where ∑(A) is the total area through calculated heat losses due to the higher
applications; however, ceiling-based low- which heat flows (m
2
), and R is the radiant emitter radiant fraction.
temperature radiant heating is now regularly fraction of the heat source; this will have a Typical wall mounted emitters (erroneously
applied to the healthcare, educational and high value for radiant heat sources (with called ‘radiators’) will emit 80 to 90 per cent
secure facility sectors. a maximum value of 1 for a pure radiant of the heat convectively and just 10 to 20
source) and a low value for predominantly per cent by radiant heat transfer – i.e. a low
Reducing the building heat loss convective sources (right down to of zero for radiant fraction of 0.2. In comparison, flat
To determine the predicted heat loss using forced air heaters). plate radiant heating panels (typically ceiling
the CIBSE Simple Method
[1]
the following In many cases when undertaking building mounted) will emit predominantly infrared
relationship is used: heat loss calculations the two factors F
1
radiation (radiant heat) – likely to be at least
cu
Φ
t
= [F
1cu
∑(AU) + F
2cu
C
v
] (θ
c
- θ
ao
) and F practically have a value of 1 and so 67 per cent radiant – ie, have a high radiant
2cu
where Φt is the total heat loss (W), F
1cu
and the heat loss expression reverts to the time factor, R, of 0.67.
F are factors that are related to the type of honoured simplification of: This radiation will travel in all directions
2cu
heat source, ∑(AU) is the sum of the products Φ
t
= [∑(AU) + C ] (θ - θ ) from the panel’s surface and passes through
V c ao
of the surface area and corresponding U However, when examining the equations the air with virtually no absorption of heat.
value for each surface where there is a heat for F
1
and F it can be seen that, as the The radiation is then absorbed by any non-
cu 2cu
flow (W·K
-1
), C
v
is the ventilation coefficient value of R increases, both factors will get reflective surfaces; any reflected heat will
(W·K
-1
), θ
c
is the operative temperature in smaller. Similarly, a combination of a high be subsequently absorbed when striking >
www.cibsejournal.com June 2009 CIBSE Journal 59
CIBSEjun09 pp59-62 cpd.indd 59 5/28/09 3:11:29 PM
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