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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
competence. CPD is a requirement of both remain available online at www.cibsejournal.
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.
The psychrometrics of HVAC sub-systems
The CPD articles in the April, August and October editions have considered
using the psychrometric chart to examine the main properties of moist
air, how values may be calculated in the absence of a chart, and the
principal processes that may be combined to develop system psychrometry.
This article completes the set of processes that are likely to be used in
commercial HVAC and develops some combined psychrometric sub-
systems. Symbols are defined in the box at the end of the article – you may
also find it useful to be able to refer to those earlier articles (all are available
online at www.cibsejournal.com)
Heat recovery processes Figure 1 –
When considering heat recovery components
Psychrometry
in HVAC systems they will exchange either
of Plate Heat
Exchanger
sensible heat, or both sensible and latent
heat, from typically the discharge room
air into the air being introduced from
outdoors. An example of a sensible heat-
recovery process is shown in Figure 1. This
is the psychrometric process that would
characterise sensible only heat recovery
in a plate heat exchanger, a (regenerative)
thermal wheel or a run-around coil. The
process is similar to that of a basic sensible
heating or cooling process – depending on
the temperature of the opposing airstream
(and this air would be typically the air that is
being extracted from the conditioned space).
Considering Figure 1, if the temperature of
50 CIBSE Journal December 2009 www.cibsejournal.com
CIBSEdec09 pp50-53 cpd.indd 50 11/19/09 3:58:40 PM
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